CCNA Discovery - Networking for Home and Small Businesses
CCNA Discovery - Networking for Home and Small Businesses
3 Connecting to the Network
3.0 Chapter Introduction
3.0.1 Introduction
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3.0.1 Introduction
Single Diagram
Diagram 1, Slide show
More and more, it is networks that connect us. People communicate online from everywhere.
Conversations in coffeehouses spill into chat rooms. Online debates continue at school.
Efficient, reliable technology enables networks to be available whenever and wherever we need them.
In this chapter, you will learn how communication occurs over a network and about the many different components that need to operate together to make it work.
After completion of this chapter, you should be able to:
Explain the concept of networking and the benefits of networks.
Explain the concept of communication protocols.
Explain how communication occurs across a local Ethernet network.
Describe Access Layer devices and communication methods on a local Ethernet network.
Describe Distribution Layer devices and communication methods across networks.
Plan, implement, and verify a local network.
3.1 Introduction to Networking
3.1.1 What is a Network?
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There are many types of networks that provide us with different kinds of services. In the course of a day, a person might make a phone call, watch a television show, listen to the radio, look up something on the Internet, or even play a video game with someone in another country. All of these activities depend on robust, reliable networks. Networks provide the ability to connect people and equipment no matter where they are in the world. People use networks without ever thinking about how they work or what it would be like if the networks did not exist.
This picture of the airport illustrates people using networks to share information, use resources and communicate with others. There are multiple types of networks shown in this scene. How many can you find?
3.1.1 What is a Network?
Two Diagrams
Diagram 1, Interactive
The diagram depicts people using the following network types. Hovering the mouse over items in the picture displays the text associated with that item.
Computer/Data Network
Provides communications between computer users via copper, fiber optic and wireless connections.
Television Network
Provides regular and high definition broadcasts over the air via cable and satellite networks.
Telephone Network
Connects callers and allows modem connections via traditional land lines.
Mobile Phone Network
Connects mobile callers to voice, text, and Internet via the mobile phone system.
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Communication technology in the 1990s, and before, required separate, dedicated networks for voice, video and computer data communications. Each of these networks required a different type of device in order to access the network. Telephones, televisions, and computers used specific technologies and different dedicated network structures, to communicate. But what if people want to access all of these network services at the same time, possibly using a single device?
New technologies create a new kind of network that delivers more than a single type of service. Unlike dedicated networks, these new converged networks are capable of delivering voice, video and data services over the same communication channel or network structure.
New products are coming to market that take advantage of the capabilities of converged information networks. People can now watch live video broadcasts on their computers, make a telephone call over the Internet, or search the Internet using a television. Converged networks make this possible.
In this course, the term network refers to these new multi-purpose, converged information networks.
3.1.1 What is a Network?
Diagram 2, Animation
The diagram depicts the following independent network types, Voice Network, Computer Network, and Video Network, and shows how all three converge to become a single Information Network that carries all three types of traffic.
3.1.2 Benefits of Networking
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Networks come in all sizes. They can range from simple networks consisting of two computers, to networks connecting millions of devices. Networks installed in small offices, or homes and home offices, are referred to as SOHO networks. SOHO networks enable sharing of resources, such as printers, documents, pictures and music between a few local computers.
In business, large networks can be used to advertise and sell products, order supplies, and communicate with customers. Communication over a network is usually more efficient and less expensive than traditional forms of communication, such as regular mail or long distance phone calls. Networks allow for rapid communication such as email and instant messaging, and provide consolidation, storage, and access to information on network servers.
Business and SOHO networks usually provide a shared connection to the Internet. The Internet is considered a "network of networks" because it is literally made up of thousands of networks that are connected to each other.
Here are other uses of a network and the Internet:
* Sharing music and video files
* Research and on-line learning
* Chatting with friends
* Planning vacations
* Purchasing gifts and supplies
Can you think of other ways people use networks and the Internet in their daily lives?
3.1.2 Benefits of Networking
Single Diagram
Diagram 1, Interactive
Small Home Networks
Small home networks connect a few computers to each other and the Internet.
Small Office/Home Office Networks
The Small Office/Home Office (SOHO) network enables computers within a home or remote office to connect to a corporate network, and have access to centralized, shared resources.
Medium to Large Networks
Medium to large networks, such as those used by corporations and schools, can have many locations with hundreds or thousands of interconnected computers.
Worldwide Networks
The Internet is a network of networks that connects hundreds of millions of computers worldwide.
3.1.3 Basic Network Components
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There are many components that can be part of a network, for example personal computers, servers, networking devices, and cabling. These components can be grouped into four main categories:
* Hosts
* Shared peripherals
* Networking devices
* Networking media
The network components that people are most familiar with are hosts and shared peripherals. Hosts are devices that send and receive messages directly across the network.
Shared peripherals are not directly connected to the network, but instead are connected to hosts. The host is then responsible for sharing the peripheral across the network. Hosts have computer software configured to enable people on the network to use the attached peripheral devices.
The network devices, as well as networking media, are used to interconnect hosts.
Some devices can play more than one role, depending on how they are connected. For example, a printer directly connected to a host (local printer) is a peripheral. A printer directly connected to a network device and participates directly in network communications is a host.
3.1.3 Basic Network Components
Two Diagrams
Diagram 1, Interactive
The diagram depicts several networking devices, including a PC, scanner, local printer, hub, switch, network printer, laptop, server, and webcam. There is a brief description about each of the categories that the devices belong to.
Peripherals
Shared peripheral devices do not communicate directly on the network. Instead, peripherals rely on their connected host to perform all network operations. Examples of peripherals are cameras, scanners, and locally attached printers. Printers and scanners can be shared.
Hosts
Hosts send and receive user traffic. A host is a generic name for most end user devices. A host has an IP network address. Examples of hosts are personal computers and network attached printers.
Network Devices
Networking devices connect other devices, mainly hosts. These devices move and control network traffic. Examples of network devices include hubs, switches, and routers.
Network Media
Network media provides connections between hosts and network devices. Network media can be wired, such as copper and fiber optic, or use wireless technologies.
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3.1.3 Basic Network Components
Diagram 2, Activity
The diagram depicts an activity in which you must match different types of networking components with the correct category.
Category
One.Peripheral
Two.Host
Three.Network Media
Four.Network Device
Devices
A:Network Printer
B:Switch
C:Hub
D:MP3 Player
E:PC
F:Laptop
G:Local Printer
H:Network Cable
I:Server
3.1.4 Computer Roles in a Network
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All computers connected to a network that participate directly in network communication are classified as hosts. Hosts can send and receive messages on the network. In modern networks, computer hosts can act as a client, a server, or both. The software installed on the computer determines which role the computer plays.
Servers are hosts that have software installed that enable them to provide information, like email or web pages, to other hosts on the network. Each service requires separate server software. For example, a host requires web server software in order to provide web services to the network.
Clients are computer hosts that have software installed that enable them to request and display the information obtained from the server. An example of client software is a web browser, like Internet Explorer.
3.1.4 Computer Roles in a Network
Three Diagrams
Diagram 1, Interactive
The diagram depicts common network server and client device pairs and gives a brief description of how they interact.
Email Server and Email Client
The email server runs server software. The client uses mail client software, such as Microsoft Outlook, to access email on the server.
Web Server and Browser Client
The web server runs server software. Clients use browser software, such as Windows Internet Explorer, to access web pages on the server.
File Server and File Access Client
The file server stores the files. A client device accesses the file with client software, such as Windows Explorer.
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A computer with server software can provide services simultaneously to one or many clients.
Additionally, a single computer can run multiple types of server software. In a home or small business, it may be necessary for one computer to act as a file server, a web server, and an email server.
A single computer can also run multiple types of client software. There must be client software for every service required. With multiple clients installed, a host can connect to multiple servers at the same time. For example, a user can check email and view a web page while instant messaging and listening to Internet radio.
3.1.4 Computer Roles in a Network
Diagram 2, Image
The diagram depicts a server running email services, web services, and file sharing services. The server has four clients attached, which are using the following services:
Computer 1 Web Browser, Email Client, File Access Client
Computer 2 Web Browser, File Access Client
Computer 3 File Access Client
Computer 4 Web Browser, Email Client
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3.1.4 Computer Roles in a Network
Diagram 3, Activity
The diagram depicts an activity in which you must identify the correct server, depending on the services a client wishes to use.
Client 1 Web Browser
Client 2 Email Client, Web Browser
Client 3 FTP Client, File Access Client
Client 4 Email Client
Server 1 Web Server, Email Server
Server 2 FTP Server, Email Server
Server 3 Web Server
Server 4 Web Server, File Server
3.1.5 Peer-to-Peer Networks
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Client and server software usually runs on separate computers, but it is also possible for one computer to carry out both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.
The simplest peer-to-peer network consists of two directly connected computers using a wired or wireless connection.
Multiple PCs can also be connected to create a larger peer-to-peer network but this requires a network device, such as a hub, to interconnect the computers.
The main disadvantage of a peer-to-peer environment is that the performance of a host can be slowed down if it is acting as both a client and a server at the same time.
In larger businesses, due to the potential for high amounts of network traffic, it is often necessary to have dedicated servers to support the number of service requests.
3.1.5 Peer to Peer Networks
Three Diagrams
Diagram 1, Image/Tabular
The diagram depicts two connected PC's. PC1 is connected to a printer.
There are speech bubbles in the diagram, as follows:
PC1 says, I have a printer to share.
PC2 says, I have files to share.
The advantages of peer to peer networking:
Easy to set up.
Less complexity.
Lower cost since network devices and dedicated servers may not be required.
Can be used for simple tasks such as transferring files and sharing printers.
The disadvantages of peer to peer networking:
No centralized administration.
Not as secure.
Not scalable.
All devices may act as both clients and servers, which can slow their performance.
Tip Popup
Microsoft operating systems have built in server software which allows any computer to share stored files with other computers on the network. When you share a file, your computer is acting as a server. Also, Microsoft computer operating systems have built in client software which allows any computer to access shared files on another computer. When you access a shared file, your computer is acting as a client.
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3.1.5 Peer to Peer Networks
Diagram 2, Activity
The diagram depicts an activity in which you must identify different roles in a peer to peer network. For each of the four scenarios, indicate whether the computer is acting as a client, server, or both.
Scenarios
One.Trishna connects to the Internet and downloads a file from a site using a protocol called File Transfer Protocol. Is Trishna's computer acting as a client, server, or both?
Two.Juan connects into an e learning website to learn about networking. Is Juan's computer acting as a client, server, or both?
Three.Noriko has a dedicated computer used for sharing her files. Carlos is downloading a folder from Noriko's computer. Is Noriko's computer acting as a client, server, or both?
Four.Patti has a video game loaded on her computer. Donald has the same video game loaded on his computer. They are playing each other over the network. Is Donald's computer acting as a client, server, or both?
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Lab Activity
Build a simple peer-to-peer network using two PCs and an Ethernet crossover cable.
Click the lab icon to begin.
3.1.5 Peer to Peer Networks
Diagram 3, Lab Activity
Link to Hands on Lab: Building a Simple Peer to Peer Network
3.1.6 Network Topologies
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In a simple network consisting of a few computers, it is easy to visualize how all of the various components connect. As networks grow, it is more difficult to keep track of the location of each component, and how each is connected to the network. Wired networks require lots of cabling and network devices to provide connectivity for all network hosts.
When networks are installed, a physical topology map is created to record where each host is located and how it is connected to the network. The physical topology map also shows where the wiring is installed and the locations of the networking devices that connect the hosts. Icons are used to represent the actual physical devices within the topology map. It is very important to maintain and update physical topology maps to aid future installation and troubleshooting efforts.
In addition to the physical topology map, it is sometimes necessary to also have a logical view of the network topology. A logical topology map groups hosts by how they use the network, no matter where they are physically located. Host names, addresses, group information and applications can be recorded on the logical topology map.
The graphics illustrate the difference between logical and physical topology maps.
3.1.6 Network Topologies
Single Diagram
Diagram 1, Interactive
Physical Topology
The diagram depicts the physical layout of the network. For example, what is connected to what.
Logical Topology
The diagram depicts a diagram of the logical topology of the network, such as IP addressing.
3.2 Principles of Communication
3.2.1 Source, Channel, and Destination
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The primary purpose of any network is to provide a method to communicate information. From the very earliest primitive humans to the most advanced scientists of today, sharing information with others is crucial for human advancement.
All communication begins with a message, or information, that must be sent from one individual or device to another. The methods used to send, receive and interpret messages change over time as technology advances.
All communication methods have three elements in common. The first of these elements is the message source, or sender. Message sources are people, or electronic devices, that need to communicate a message to other individuals or devices. The second element of communication is the destination, or receiver, of the message. The destination receives the message and interprets it. A third element, called a channel, provides the pathway over which the message can travel from source to destination.
3.2.1 Source, Channel, and Destination
Single Diagram
Diagram 1, Animation
The diagram depicts the flow of information with respect to communication between two humans and then between two computers. In both cases, the message starts at the message source and is converted to a signal by the transmitter. The signal is transmitted over the transmission media and received by the receiver. At this point, it is reassembled as a message for the message destination.
3.2.2 Rules of Communication
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In any conversation between two people, there are many rules, or protocols, that the two must follow in order for the message to be successfully delivered and understood. Among the protocols for successful human communication are:
* Identification of sender and receiver
* Agreed-upon medium or channel (face-to-face, telephone, letter, photograph)
* Appropriate communication mode (spoken, written, illustrated, interactive or one-way)
* Common language
* Grammar and sentence structure
* Speed and timing of delivery
Imagine what would happen if no protocols or rules existed to govern how people communicate with each other. Would you be able to understand them? Are you able to read the paragraph that does not follow commonly accepted protocols?
3.2.2 Rules of Communication
Two Diagrams
Diagram 1, Interactive
The diagram depicts several lines of text that are difficult to understand if there are no protocols governing the structure of the information. The example below shows text that is displayed without using agreed upon protocols:
Humans communications between govern rules.
Itisverydifficulttounderstandmessagesthatarenotformattedanddonotfollowtheestablishedrulesandprotocols.
A estrutura da gramatica, da lingua, da pontuacao e do sentance faz a configuracao humana compreensivel por muitos individuos differentes.
Clicking the Translate button applies the protocol and translated text appears below:
Rules govern communications between humans.
It is very difficult to understand messages that are not correctly formatted and do not allow the established rules and protocols.
The structure of the grammar, the language, the punctuation, and the sentence make the configuration humanly understandable for many different individuals.
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Protocols are specific to the characteristics of the source, channel and destination of the message. The rules used to communicate over one medium, like a telephone call, are not necessarily the same as communication using another medium, such as a letter.
Protocols define the details of how the message is transmitted, and delivered. This includes issues of:
* Message format
* Message size
* Timing
* Encapsulation
* Encoding
* Standard message pattern
Many of the concepts and rules that make human communication reliable and understandable also apply to computer communication.
3.2.2 Rules of Communication
Diagram 2, Image
The diagram depicts a box at the center of a star arrangement surrounded by six boxes, acting as nodes. The center box is labeled Protocols. The other six boxes are labeled: Encoding, Message Pattern, Timing, Message Size, Encapsulation, and Message Format. The diagram is suggesting that all of these characteristics are associated with protocols.
3.2.3 Message Encoding
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One of the first steps to sending a message is encoding it. Written words, pictures, and spoken languages each use a unique set of codes, sounds, gestures, and/or symbols to represent the thoughts being shared. Encoding is the process of converting thoughts into the language, symbols, or sounds, for transmission. Decoding reverses this process in order to interpret the thought.
Imagine a person watching a sunset and then calling someone else to talk about how beautiful the sunset looks. To communicate the message, the sender must first convert, or encode, their thoughts and perceptions about the sunset into words. The words are spoken into the telephone using the sounds and inflections of spoken language that convey the message. On the other end of the telephone line, the person listening to the description, receives and decodes the sounds in order to visualize the image of the sunset described by the sender.
Encoding also occurs in computer communication. Encoding between hosts must be in an appropriate form for the medium. Messages sent across the network are first converted into bits by the sending host. Each bit is encoded into a pattern of sounds, light waves, or electrical impulses depending on the network media over which the bits are transmitted. The destination host receives and decodes the signals in order to interpret the message.
3.2.3 Message Encoding
Single Diagram
Diagram 1, Animation
The diagram depicts two people standing next to each other conversing. The conversation flow is broken down into the following steps:
Human Communication
One.The girl begins the conversation. She is determined to be the message source.
Two.The girl processes the thought and begins the encoding of the message into English.
Three.The girl begins to speak in English to the boy. She defines herself at this stage as the transmitter. The audible signal generated by the girl as conversation is received by the boy. The transmission medium is the link between the boy and the girl, and this is defined as the channel.
Four.The receiver receives the communication from the girl and decodes the signal so he can understand the content.
Five.The receiver is known as the destination where decoding occurs.
Computer Communication
One.PC1 begins the communication. It is determined to be the message source.
Two.PC1 begins encoding of the message and transmits it to PC2.
Three.The digital signal generated by PC1 as a data stream is received by PC2. The transmission medium is the link between PC1 and PC2, which is defined as the channel.
Four.The receiver, PC2, receives the communication from PC1, and decodes the signal so it can understand the content.
Five.The receiver is known as the destination where decoding occurs.
3.2.4 Message Formatting
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When a message is sent from source to destination, it must use a specific format or structure. Message formats depend on the type of message and the channel that is used to deliver the message.
Letter writing is one of the most common forms of written human communication. For centuries, the agreed format for personal letters has not changed. In many cultures, a personal letter contains the following elements:
* An identifier of the recipient
* A salutation or greeting
* The message content
* A closing phrase
* An identifier of the sender
In addition to having the correct format, most personal letters must also be enclosed, or encapsulated, in an envelope for delivery. The envelope has the address of the sender and receiver on it, each located at the proper place on the envelope. If the destination address and formatting are not correct, the letter is not delivered.
The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation. De-encapsulation occurs when the process is reversed by the recipient and the letter is removed from the envelope.
3.2.4 Message Formatting
Three Diagrams
Diagram 1, Animation
Message Formatting
The diagram depicts the addressing and content of a letter being posted by snail mail from the sender to the receiver. This demonstrates the concepts of formatting and encapsulation and is depicted as an envelope and a letter inside the envelope. The components and addressing are as follows:
Envelope Addressing
One.Recipient (destination), Location Address: 1400 Main St, Canton, Ohio, 44203.
Two.Sender (source), Location Address: 4085 SE Pine St, Ocala, Florida, 34471.
Encapsulated Letter
Three.Salutation (start of message indicator), Dear
Four.Recipient (destination identifier), Jane
Five.Content of letter (encapsulated data), I just returned from my trip. I thought you might like to see my pictures.
Six.Sender (source identifier), John
Seven.End of frame (end of message indicator), Stamp and postmark
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A letter writer uses an accepted format to ensure that the letter is delivered and understood by the recipient. In the same way, a message that is sent over a computer network follows specific format rules for it to be delivered and processed. Just as a letter is encapsulated in an envelope for delivery, so computer messages are encapsulated. Each computer message is encapsulated in a specific format, called a frame, before it is sent over the network. A frame acts like an envelope; it provides the address of the intended destination and the address of the source host.
The format and contents of a frame are determined by the type of message being sent and the channel over which it is communicated. Messages that are not correctly formatted are not successfully delivered to or processed by the destination host.
3.2.4 Message Formatting
Diagram 2, Image
The diagram depicts the composition of a computer message sent from the sender to the recipient. The frame composition is as follows:
Frame Addressing
Destination (physical hardware address)
Source (physical hardware address)
End of Frame (end of message indicator)
Encapsulated Message
Start Flag (start of message indicator)
Recipient (destination identifier)
Sender (source identifier)
Encapsulated data (bits)
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3.2.4 Message Formatting
Diagram 3, Activity
The diagram depicts an activity in which you must match the components of the following voice messages to the proper locations within a frame.
The matching blocks of information are listed below:
Frame Composition
One.Destination location address
Two.Source location address
Three.Start of message flag
Four.Destination identifier address
Five.Message
Six.Source identifier address
Seven. End of message flag
Human Communication Components
A:Bye
B:Hello
C:This is Chris. Can you tell me what the math assignment is for today?
D:Tasha
E:000 555 2000
F:Chris
G:000 555 1000
3.2.5 Message Size
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Imagine what it would be like to read this course if it all appeared as one long sentence; it would not be easy to read and comprehend. When people communicate with each other, the messages that they send are usually broken into smaller parts or sentences. These sentences are limited in size to what the receiving person can process at one time. An individual conversation may be made up of many smaller sentences to ensure that each part of the message is received and understood.
Likewise, when a long message is sent from one host to another over a network, it is necessary to break the message into smaller pieces. The rules that govern the size of the pieces, or frames, communicated across the network are very strict. They can also be different, depending on the channel used. Frames that are too long or too short are not delivered.
The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements. Each piece is encapsulated in a separate frame with the address information, and is sent over the network. At the receiving host, the messages are de-encapsulated and put back together to be processed and interpreted.
3.2.5 Message Size
Diagram 1, Animation
Human Communication
The diagram depicts a man and a woman communicating with each other. The woman starts the conversation with a sentence that is spoken very rapidly with no separation between words. The man receives this message and replies, I cannot understand. The woman receives this information and repeats the message, speaking at the correct speed. The man receives the information again, and this time he understands the message.
Computer Communication
The diagram depicts the communication between two computers. Computer 1 has an image it wants to send to Computer 2 located on the network. Computer 1 sends the image to Computer 2 as a complete transmission, which is one block of information. It sends this stream of information to Computer 2 who receives it and replies, I cannot understand the data you sent me as it is not formatted correctly or in the appropriate sizing blocks for me to understand. Computer 1 takes in this message from Computer 2 and resizes the image into smaller blocks of Information. The smaller blocks are re-assembled at the destination, or on Computer 2 in this case, so the image can be viewed as a single entity.
3.2.6 Message Timing
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One factor that affects how well a message is received and understood is timing. People use timing to determine when to speak, how fast or slow to talk, and how long to wait for a response. These are the rules of engagement.
Access Method
Access Method determines when someone is able to send a message. These timing rules are based on the environment. For example, you may be able to speak whenever you have something to say. In this environment, a person must wait until no one else is talking before speaking. If two people talk at the same time, a collision of information occurs and it is necessary for the two to back off and start again. These rules ensure communication is successful. Likewise, it is necessary for computers to define an access method. Hosts on a network need an access method to know when to begin sending messages and how to respond when errors occur.
Flow Control
Timing also effects how much information can be sent and the speed that it can be delivered. If one person speaks too quickly, it is difficult for the other person to hear and understand the message. The receiving person must ask the sender to slow down. In network communication, a sending host can transmit messages at a faster rate than the destination host can receive and process. Source and destination hosts use flow control to negotiate correct timing for successful communication.
Response Timeout
If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly. The person may repeat the question, or may go on with the conversation. Hosts on the network also have rules that specify how long to wait for responses and what action to take if a response timeout occurs.
3.2.6 Message Timing
Single Diagram
Diagram 1, Interaction
The diagram depicts three different aspects of message timing that are commonly used to control the flow of data between hosts, as described below:
Access Method
The man and the woman are communicating with each other. The woman begins the communication with a question, What time is the movie? The man also starts to talk. His question to the woman is, What time are we meeting for dinner? Because both are speaking (transmitting) at the same time, the message received by each person (or computer host) is not clear, so the message must be repeated (a re transmit is required). Both the man and the woman reply to their first attempt at communicating by saying to each other, Sorry, I did not understand you.
Flow Control
The woman and the man are communicating by telephone. The woman sends three quick messages, Hello, can you hear me?, Hello, can you hear me?, Hello, can you hear me? The man receives these messages but does not have an opportunity to respond, and cannot distinguish the beginning and the end of the message. He is unsure if the content has been received in its entirety or whether there has been a corruption in the stream of information that has caused the repetition.
Hence the mans reply is the symbol of a question mark.
Response Timeout
The diagram depicts a man and a woman on the telephone. The woman queries the man, Hello, can you hear me? The man does not respond. She repeats her question but there is still no response from the man. The woman tries one last time to communicate with the man. She is resolved at this point to stop her communication with the man, due to his lack of response.
3.2.7 Message Patterns
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Sometimes, a person wants to communicate information to a single individual. At other times, the person may need to send information to a group of people at the same time, or even to all people in the same area. A conversation between two people is an example of a one-to-one pattern of communication. When a group of recipients need to receive the same message simultaneously, a one-to-many or one-to-all message pattern is necessary.
There are also times when the sender of a message needs to be sure that the message is delivered successfully to the destination. In these cases, it is necessary for the recipient to return an acknowledgement to the sender. If no acknowledgement is required, the message pattern is referred to as unacknowledged.
Hosts on a network use similar message patterns to communicate.
A one-to-one message pattern is referred to as a unicast, meaning that there is only a single destination for the message.
When a host needs to send messages using a one-to-many pattern, it is referred to as a multicast. Multicasting is the delivery of the same message to a group of host destinations simultaneously.
If all hosts on the network need to receive the message at the same time, a broadcast is used. Broadcasting represents a one-to-all message pattern. Additionally, hosts have requirements for acknowledged versus unacknowledged messages.
3.2.7 Message Patterns
Single Diagram
Diagram 1, Interactive
The diagram depicts the three types of message patterns with reference to a single message source and one or more destinations. The definitions for unicast, multicast, and broadcast for both Human and Computer communication are as follows:
Human Communication
Unicast: Sent from the source person to one single person within the group.
Multicast: Sent from the source person to multiple people within the group.
Broadcast: Sent from the source person to all the people within the group.
Computer Communication
Unicast: Sent from the source to a single destination within a broadcast domain or a group of potential destinations.
Multicast: Sent from the source to multiple destinations within the broadcast domain or group of destinations.
Broadcast: Sent from the source to all the hosts within the broadcast domain or group of destinations.
3.2.8 Protocol Use in Communication
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All communication, both human and computer, is governed by pre-established rules, or protocols. These protocols are determined by the characteristics of the source, channel and destination. Based on the source, channel and destination, the protocols define the details for the issues of message format, message size, timing, encapsulation, encoding and standard message pattern.
3.2.8 Protocol Use in Communication
Two Diagrams
Diagram 1, Image
The diagram depicts a box at the center of a star arrangement surrounded by six other boxes, acting as nodes. The center box is labeled Protocols, and the other six boxes are labeled Encoding, Message Pattern, Timing, Message Size, Encapsulation, and Message Format. The diagram illustrates that all of these characteristics are defined by the protocol.
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3.2.8 Protocol Use in Communication
Diagram 2, Activity
The diagram depicts an activity in which you must match four keywords to thee definitions. Below is a list of keywords and the definitions that have to be matched:
KEYWORDS
A:Message Format
B:Timing
C:Encoding
D:Message Size
DEFINITIONS
One.Fred went to an auction and the auctioneer was talking so fast that Fred was unable to understand her.
Two.Andrea writes a letter and posts it to her friend. Unfortunately, Andrea mis addressed the letter and it never arrived.
Three.Mark is writing an English term paper at college. His instructor grades the paper and comments that his grade was reduced due to the excessive use of run on sentences and poor punctuation.
Four.An English only speaking individual on vacation in Germany could not order dinner with a German only speaking waiter.
3.3 Communicating on a Local Wired Network
3.3.1 Importance of Protocols
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Computers, just like humans, use rules, or protocols, in order to communicate.
Protocols are especially important on a local network. In a wired environment, a local network is defined as an area where all hosts must "speak the same language" or in computer terms "share a common protocol".
If everyone in the same room spoke a different language they would not be able to communicate. Likewise, if devices in a local network did not use the same protocols they would not be able to communicate.
The most common set of protocols used on local wired networks is Ethernet.
The Ethernet protocol defines many aspects of communication over the local network, including: message format, message size, timing, encoding, and message patterns.
3.3.1 Importance of Protocols
Single Diagram
Diagram 1, Image
The diagram depicts three people within a single room, communicating with each other in Japanese. The need for a universal protocol to be established between the communicating parties is necessary so that all participants understand each other. The diagram for the local area network (LAN) depicts four PC's connected to a switch. Within a LAN, the established language is Ethernet.
3.3.2 Standardization of Protocols
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In the early days of networking, each vendor used their own, proprietary methods of interconnecting network devices and networking protocols. Equipment from one vendor could not communicate with equipment from another.
As networks became more widespread, standards were developed that defined rules by which network equipment from different vendors operated. Standards are beneficial to networking in many ways:
* Facilitate design
* Simplify product development
* Promote competition
* Provide consistent interconnections
* Facilitate training
* Provide more vendor choices for customers
There is no official local networking standard protocol, but over time, one technology, Ethernet, has become more common than the others. It has become a de facto standard.
3.3.2 Standardization of Protocols
Two Diagrams
Diagram 1, Image
The diagram depicts the network communications protocols that were first developed by companies as proprietary protocols, and were for the most part vendor specific. The protocols established in the early 1970's were by IBM, NCR, Xerox, D E C, and HP. As time progressed, the 1980's brought about the development of major standardized protocols, such as Ethernet IEEE 8 0 2 dot 3, ARCnet 8 0 2 dot 4, and Token Ring 8 0 2 dot 5. With widespread expansion of the Internet in the 1990's, the eventual winner in the protocol race was Ethernet 8 0 2 dot 3 (circa 2000).
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The Institute of Electrical and Electronic Engineers, or IEEE (pronounced eye-triple-e), maintains the networking standards, including Ethernet and wireless standards. IEEE committees are responsible for approving and maintaining the standards for connections, media requirements and communications protocols. Each technology standard is assigned a number that refers to the committee that is responsible for approving and maintaining the standard. The committee responsible for the Ethernet standards is 802.3.
Since the creation of Ethernet in 1973, standards have evolved for specifying faster and more flexible versions of the technology. This ability for Ethernet to improve over time is one of the main reasons that it has become so popular. Each version of Ethernet has an associated standard. For example, 802.3 100BASE-T represents the 100 Megabit Ethernet using twisted pair cable standards. The standard notation translates as:
* 100 is the speed in Mbps
* BASE stands for baseband transmission
* T stands for the type of cable, in this case, twisted pair.
Early versions of Ethernet were relatively slow at 10 Mbps. The latest versions of Ethernet operate at 10 Gigabits per second and faster. Imagine how much faster these new versions are than the original Ethernet networks.
3.3.2 Standardization of Protocols
Diagram 2, Slider Graphic
The diagram depicts a timeline of the development of the Ethernet protocols. As the scroll bar is moved to the right into the more recent Ethernet protocols, a pipe transmitting packets continues to get larger and becomes capable of carrying more packets. Listed below is the date, the standard developed, and the description of the event:
1973: Ethernet Developed by Dr Robert Metcalf at Xerox Corp.
1980: D I X standard Digital Equipment Corp, Intel, and Xerox release a standard for 10Mbps Ethernet over coaxial
1983: IEEE 8 0 2 dot 3, 10BASE 5, 10Mbps Ethernet over thick coaxial cable
1985: IEEE 8 0 2 dot 3a, 10BASE 2, 10Mbps over thin coaxial cable
1990: IEEE 8 0 2 dot 3i, 10BASE T, 10Mbps Ethernet over twisted pair (TP)
1993: IEEE 8 0 2 dot 3j, 10BASE F, 10Mbps Ethernet over fiber optic
1995: IEEE 8 0 2 dot 3u, 100BASE xx, Fast Ethernet: 100Mbps Ethernet over twisted pair (TP) and fiber (various standards)
1998: IEEE 8 0 2 dot 3z, 1000BASE x, Gigabit Ethernet over fiber optic
1999: IEEE 8 0 2 dot 3a b, 1000BASE T, Gigabit Ethernet over twisted pair (TP)
2002: IEEE 8 0 2 dot 3a e, 10G BASE xx, 10 Gigabit Ethernet over fiber (various standards)
2006: IEEE 8 0 2 dot 3a n, 10G BASE T, 10 Gigabit Ethernet over twisted pair (TP)
3.3.3 Physical Addressing
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All communication requires a way to identify the source and destination. The source and destination in human communication are represented by names.
When a name is called, the person with that name listens to the message and responds. Other people in the room may hear the message, but they ignore it because it is not addressed to them.
On Ethernet networks, a similar method exists for identifying source and destination hosts. Each host connected to an Ethernet network is assigned a physical address which serves to identify the host on the network.
Every Ethernet network interface has a physical address assigned to it when it is manufactured. This address is known as the Media Access Control (MAC) Address. The MAC address identifies each source and destination host on the network.
Ethernet networks are cable based, meaning that a copper or fiber optic cable connects hosts and networking devices. This is the channel used for communications between the hosts.
When a host on an Ethernet network communicates, it sends frames containing its own MAC address as the source and the MAC address of the intended recipient. Any hosts that receive the frame will decode the frame and read the destination MAC address. If the destination MAC address matches the address configured on the NIC, it will process the message and store it for the host application to use. If the destination MAC address does not match the host MAC address, the NIC will ignore the message.
3.3.3 Physical Addressing
Two Diagrams
Diagram 1, Animation
The diagram depicts a hub at the center of a star topology with four PC's surrounding the hub. The PC's have been named H1 through H4 and have MAC (Media Access Control) addresses assigned as shown in the list below:
H1 AA:AA:AA:AA:AA:AA
H2 BB:BB:BB:BB:BB:BB
H3 CC:CC:CC:CC:CC:CC
H4 DD:DD:DD:DD:DD:DD
H1 is the source, and H3 is the destination. A speech bubble above H1 says, I need to send information to H3. The message transmits to all hosts on the network. There is a text box indicating the parameters of the framing of the transmission, as listed below:
Frame parameters
Frame Addressing (next 2 items)
Destination Address CC:CC:CC:CC:CC:CC
Source Address AA:AA:AA:AA:AA:AA
Data encapsulated data
All machines on the network reply in speech bubbles. After the transmission has reached them, H2 and H4 reply, This is not addressed to me, I shall ignore it. H3 replies, This is mine, and keeps the message.
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Lab Activity
Use the ipconfig /all command to display the MAC address of your computer.
Click the lab icon to begin.
3.3.3 Physical Addressing
Diagram 2, Lab Activity
Link to a Hands On Lab: Determine the MAC Address of a Host
3.3.4 Ethernet Communication
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The Ethernet protocol standards define many aspects of network communication including frame format, frame size, timing and encoding.
When messages are sent between hosts on an Ethernet network, the hosts format the messages into the frame layout that is specified by the standards. Frames are also referred to as Protocol Data Units (PDUs).
The format for Ethernet frames specifies the location of the destination and source MAC addresses, and additional information including:
* Preamble for sequencing and timing
* Start of frame delimiter
* Length and type of frame
* Frame check sequence to detect transmission errors
The size of Ethernet frames is limited to a maximum of 1518 bytes and a minimum size of 64 bytes from the Destination MAC Address field through the Frame Check Sequence. Frames that do not match these limits are not processed by the receiving hosts. In addition to the frame formats, sizes and timing, Ethernet standards define how the bits making up the frames are encoded onto the channel. Bits are transmitted as either electrical impulses over copper cable or as light impulses over fiber optic cable.
3.3.4 Ethernet Communication
Two Diagrams
Diagram 1, Image
The diagram depicts the structure of an Ethernet frame. Listed below, from left to right, is the structure of a frame:
Structure of the Ethernet Frame
Preamble, 7 bytes Defines pattern of alternating 1 and 0 bits used to synchronize timing.
Start of Frame Delimiter (SFD), 1 byte. Marks the end of the timing information and start of the frame.
Destination MAC Address, 6 bytes. Contains the destination MAC address (receiver). The destination MAC address can be unicast, multicast, or broadcast.
Source MAC Address, 6 bytes. Contains the source MAC address (sender). This is the address of the Ethernet node that transmitted the data.
Length/Type, 2 bytes. Supports two different uses. A type value indicates which protocol will receive data. The length indicates the number of bytes of data that follows this field.
Encapsulated Data, 46 to 1500 bytes. The payload and sizing requirements stipulate between 64 to 1518 bytes for the entire Ethernet frame.
Frame Check Sequence (FCS), 4 bytes. Contains a four byte value that is created by the device that sends the frame and is recalculated by the destination device to check for damage to the frame.
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3.3.4 Ethernet Communication
Diagram 2, Activity
The diagram depicts an activity in which you must build a standard IEEE 802.3 Ethernet frame based on the source and destination device. The star topology has been configured with a switch at the center and five hosts attached. The source has the MAC address AA:AA:AA:AA:AA:AA and the destination host has the MAC address BB:BB:BB:BB:BB:BB. Place the fields below in the correct order:
One.Preamble
Two.DATA (Encapsulated Packet)
Three.Length/Type Field
Four.BB:BB:BB:BB:BB:BB
Five.AA:AA:AA:AA:AA:AA
Six.Frame Check Sequence (FCS)
Seven.Start of Frame Delimiter (SFD)
3.3.5 Hierarchical Design of Ethernet Networks
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Imagine how difficult communication would be if the only way to send a message to someone was to use the person's name. If there were no street addresses, cities, towns, or country boundaries, delivering a message to a specific person across the world would be nearly impossible.
On an Ethernet network, the host MAC address is similar to a person's name. A MAC address indicates the individual identity of a specific host, but it does not indicate where on the network the host is located. If all hosts on the Internet (over 400 million of them) were each identified by only their unique MAC address, imagine how difficult it would be to locate a single one.
Additionally, Ethernet technology generates a large amount of broadcast traffic in order for hosts to communicate. Broadcasts are sent to all hosts within a single network. Broadcasts consume bandwidth and slow network performance. What would happen if the millions of hosts attached to the Internet were all in one Ethernet network and were using broadcasts?
For these two reasons, large Ethernet networks consisting of many hosts are not efficient. It is better to divide larger networks into smaller, more manageable pieces. One way to divide larger networks is to use a hierarchical design model.
3.3.5 Hierarchical Design of Ethernet Networks
Diagram 1, Interactive
The diagram depicts an image of the world. It is primarily focused on North America. The image zooms in to Canada to indicate that there are specific boundaries to countries, just like there are boundaries within the addressing parameters of a network. This is otherwise known as hierarchical addressing. The image zooms again, this time it is focused on Nova Scotia, which is a province in Canada. The town of Halifax is shown next, and the end result shows a street and a specific location, namely a house address, which represents a host IP address on a network.
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In networking, hierarchical design is used to group devices into multiple networks that are organized in a layered approach. It consists of smaller, more manageable groups that allow local traffic to remain local. Only traffic that is destined for other networks is moved to a higher layer.
A hierarchical, layered design provides increased efficiency, optimization of function, and increased speed. It allows the network to scale as required because additional local networks can be added without impacting the performance of the existing ones.
The hierarchical design has three basic layers:
* Access Layer - to provide connections to hosts in a local Ethernet network.
* Distribution Layer - to interconnect the smaller local networks.
* Core Layer - a high-speed connection between distribution layer devices.
With this new hierarchical design, there is a need for a logical addressing scheme that can identify the location of a host. This is the Internet Protocol (IP) addressing scheme.
3.3.5 Hierarchical Design of Ethernet Networks
Diagram 2, Image
The diagram depicts a network that has been segmented into three hierarchical layers, the Access Layer, The Distribution Layer, and the Core Layer. Refer to the text body for details.
3.3.6 Logical Addressing
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A person's name usually does not change. A person's address on the other hand, relates to where they live and can change. On a host, the MAC address does not change; it is physically assigned to the host NIC and is known as the physical address. The physical address remains the same regardless of where the host is placed on the network.
The IP address is similar to the address of a person. It is known as a logical address because it is assigned logically based on where the host is located. The IP address, or network address, is assigned to each host by a network administrator based on the local network.
IP addresses contain two parts. One part identifies the local network. The network portion of the IP address will be the same for all hosts connected to the same local network. The second part of the IP address identifies the individual host. Within the same local network, the host portion of the IP address is unique to each host.
Both the physical MAC and logical IP addresses are required for a computer to communicate on a hierarchical network, just like both the name and address of a person are required to send a letter.
3.3.6 Logical Addressing
Diagram 1, Interactive
The diagram depicts two network clouds, both connected by a router. Directly connected to the router are hubs, one for each cloud, that act as concentrators for each network. Network 1 has a network address of 192.168.200.0, and network 2 has a network address of 192.168.1.0. Network 192.168.200.0 has four computers named H1 through H4 and have been assigned the addresses 192.168.200.1 through 192.168.200.4 respectively. Network 192.168.1.0 has four connected computers and they have been named H5 through H8 and have been assigned the addresses 192.168.1.1 through 192.168.1.4 respectively. H3 and H8 have been highlighted and an information box appears defining which parts of their corresponding IP address is dedicated to the network, and which part is dedicated to the host. The information that appears in the box is listed below:
H3 192.168.200 (Network portion), .3 (host portion)
H8 192.168.1 (Network portion), .4 (host portion)
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Lab Activity
Use the ipconfig /all command to display the IP address of your computer.
Click the lab icon to begin.
3.3.6 Logical Addressing
Diagram 2, Lab Activity
Link to Hands on Lab: Determine the IP Address of a Computer
3.3.7 Access and Distribution Layers and Devices
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IP traffic is managed based on the characteristics and devices associated with each of the three layers: Access, Distribution and Core. The IP address is used to determine if traffic should remain local or be moved up through the layers of the hierarchical network.
Access Layer
The Access Layer provides a connection point for end user devices to the network and allows multiple hosts to connect to other hosts through a network device, usually a hub or switch. Typically, all devices within a single Access Layer will have the same network portion of the IP address.
If a message is destined for a local host, based on the network portion of the IP address, the message remains local. If it is destined for a different network, it is passed up to the Distribution Layer. Hubs and switches provide the connection to the Distribution Layer devices, usually a router.
Distribution Layer
The Distribution Layer provides a connection point for separate networks and controls the flow of information between the networks. It typically contains more powerful switches than the Access Layer as well as routers for routing between networks. Distribution Layer devices control the type and amount of traffic that flows from the Access Layer to the Core Layer.
Core Layer
The Core Layer is a high-speed backbone layer with redundant (backup) connections. It is responsible for transporting large amounts of data between multiple end networks. Core Layer devices typically include very powerful, high-speed switches and routers. The main goal of the Core Layer is to transport data quickly.
Hubs, switches, and routers are discussed in more detail in the next two sections.
3.3.7 Access and Distribution Layer Devices
Two Diagrams
Diagram 1, Interactive
The diagram depicts a network that has been segmented into three layers: Access Layer, Distribution Layer, and Core Layer. Listed below are the devices supported at each layer:
Access Layer devices, IP phones, host computers, switches, and hubs
Distribution Layer devices, Routers
Core Layer devices, Switch route processors
Clicking a highlighted devices displays a photograph of the actual device.
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3.3.7 Access and Distribution Layer Devices
Diagram 2, Activity
The diagram depicts an activity in which you must select the addresses that are needed, the devices involved, and the layer on which the task occurs for each scenario.
Choices for each scenario:
Addresses: MAC, IP
Devices: Hub/Switch, Router
Layers: Access, Distribution, Core
Scenarios
One. Josh shares a file with another user on the network.
Two. Timar downloads a file from a server located in another country.
Three. Natalie sends an email from her email account at school to a student at a different school.
Four. Rhonda connects to the school network in order to download a file for her term report. The server is located on a different local network than her computer.
3.4 Building the Access Layer of an Ethernet Network
3.4.1 Access Layer
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The Access Layer is the most basic level of the network. It is the part of the network in which people gain access to other hosts and to shared files and printers. The Access Layer is composed of host devices, as well as the first line of networking devices to which they are attached.
Networking devices enable us to connect many hosts with each other and also provide those hosts access to services offered over the network. Unlike the simple network consisting of two hosts connected by a single cable, in the Access Layer, each host is connected to a networking device. This type of connectivity is shown in the graphic.
Within an Ethernet network, each host is able to connect directly to an Access Layer networking device using a point-to-point cable. These cables are manufactured to meet specific Ethernet standards. Each cable is plugged into a host NIC and then into a port on the networking device. There are several types of networking devices that can be used to connect hosts at the Access Layer, including Ethernet hubs and switches.
3.4.1 Access Layer
Single Diagram
Diagram 1, Image
The diagram depicts a network, which has been split into three layers: Access Layer, Distribution Layer, and Core Layer. The focus is on the Access Layer, which includes all host computers, switches, hubs, and IP phones.
3.4.2 Function of Hubs
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A hub is one type of networking device that is installed at the Access Layer of an Ethernet network. Hubs contain multiple ports that are used to connect hosts to the network. Hubs are simple devices that do not have the necessary electronics to decode the messages sent between hosts on the network. Hubs cannot determine which host should get any particular message. A hub simply accepts electronic signals from one port and regenerates (or repeats) the same message out all of the other ports.
Remember that the NIC on a host accepts messages only addressed to the correct MAC address. Hosts ignore messages that are not addressed to them. Only the host specified in the destination address of the message processes the message and responds to the sender.
All of the ports on the Ethernet hub connect to the same channel to send and receive messages. Because all hosts must share the bandwidth available on that channel, a hub is referred to as a shared-bandwidth device.
3.4.2 Function of Hubs
Three Diagrams
Diagram 1, Interactive
The diagram depicts the function of a hub. The source sends a packet to the destination, the hub receives the packet, and sends it to all other ports, except the source.
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Only one message can be sent through an Ethernet hub at a time. It is possible for two or more hosts connected to a hub to attempt to send a message at the same time. If this happens, the electronic signals that make up the messages collide with each other at the hub.
A collision causes the messages to become garbled and unreadable by the hosts. A hub does not decode the messages; therefore it does not detect that the message is garbled and repeats it out all the ports. The area of the network where a host can receive a garbled message resulting from a collision is known as a collision domain.
Inside a collision domain, when a host receives a garbled message, it detects that a collision has occurred. Each sending host waits a short amount of time and then attempts to send, or retransmit, the message again. As the number of hosts connected to the hub increases, so does the chance of collisions. More collisions cause more retransmissions. Excessive retransmissions can clog up the network and slow down network traffic. For this reason, it is necessary to limit the size of a collision domain.
3.4.2 Function of Hubs
Diagram 2, Interactive
The diagram depicts a hub with hosts attached to form a collision domain.
In this collision domain, all hosts will receive the garbled message when a collision occurs.
The diagram depicts a collision. Two sources send a packet to a destination. The hub receives both packets at the same time. The hub sends a garbled message to all devices.
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3.4.2 Function of Hubs
The diagram depicts an activity in which you must answer the questions for each scenario. Two hubs that are connected, each with four PC's attached.
Hub A has Hosts H1, H2, H3 and H4 connected.
Hub B has Hosts H5, H6, H7 and H8 connected.
3.4.3 Function of Switches
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An Ethernet switch is a device that is used at the Access Layer. Like a hub, a switch connects multiple hosts to the network. Unlike a hub, a switch can forward a message to a specific host. When a host sends a message to another host on the switch, the switch accepts and decodes the frames to read the physical (MAC) address portion of the message.
A table on the switch, called a MAC address table, contains a list of all of the active ports and the host MAC addresses that are attached to them. When a message is sent between hosts, the switch checks to see if the destination MAC address is in the table. If it is, the switch builds a temporary connection, called a circuit, between the source and destination ports. This new circuit provides a dedicated channel over which the two hosts can communicate. Other hosts attached to the switch do not share bandwidth on this channel and do not receive messages that are not addressed to them. A new circuit is built for every new conversation between hosts. These separate circuits allow many conversations to take place at the same time, without collisions occurring.
3.4.3 Function of Switches
Four Diagrams
Diagram 1, Interactive
The diagram depicts the function of a switch. The source sends a packet to the destination. The switch receives a packet and checks the MAC table for a port to which the destination is connected. The packet is sent to the destination port.
The diagram depicts a MAC table, which includes the fields Port Number and MAC Address of device connected.
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What happens when the switch receives a frame addressed to a new host that is not yet in the MAC address table? If the destination MAC address is not in the table, the switch does not have the necessary information to create an individual circuit. When the switch cannot determine where the destination host is located, it uses a process called flooding to forward the message out to all attached hosts. Each host compares the destination MAC address in the message to its own MAC address, but only the host with the correct destination address processes the message and responds to the sender.
How does the MAC address of a new host get into the MAC address table? A switch builds the MAC address table by examining the source MAC address of each frame that is sent between hosts. When a new host sends a message or responds to a flooded message, the switch immediately learns its MAC address and the port to which it is connected. The table is dynamically updated each time a new source MAC address is read by the switch. In this way, a switch quickly learns the MAC addresses of all attached hosts.
3.4.3 Function of Switches
Diagram 2, Interactive
The diagram depicts the function of a switch. The source sends a packet to a destination. The switch receives the packet and checks the MAC table for a port to which the destination is connected. If the MAC address is not in the table, the switch sends the packet to all ports, except the source. If the MAC address is in the table, the switch sends the packet only to the destination.
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Sometimes, it is necessary to connect another networking device, like a hub, to a switch port. This is done to increase the number of hosts that can be connected to the network. When a hub is connected to a switch port, the switch associates the MAC addresses of all hosts connected to that hub with the single port on the switch. Occasionally, one host on the attached hub sends a message to another host attached to the same hub. In this case, the switch receives the frame and checks the table to see where the destination host is located. If both the source and destination hosts are located on the same port, the switch discards the message.
When a hub is connected to a switch port, collisions can occur on the hub. The hub forwards to all ports the damaged messages resulting from a collision. The switch receives the garbled message, but, unlike a hub, a switch does not forward the damaged messages caused by collisions. As a result, every switch port creates a separate collision domain. This is a good thing. The fewer hosts contained in a collision domain, the less likely it is that a collision will occur.
3.4.3 Function of Switches
Diagram 3, Interactive
The diagram depicts how a collision is treated using switches.
There are two connected switches, Switch 1 and Switch 2. Switch 1 is connected to a hub, which has eight attached PC's labeled H1 through H8.
Switch 2 has eight attached PC's, also labeled H1 through H8.
Scenarios
One.
Two hosts on the hub that are attached to Switch 1 send a packet at the same time, causing a collision.
The hub on Switch 1 broadcasts the garbled packet to all hosts, including Switch 1.
Switch 1 discards the packet and does not forward it to Switch 2.
Two.
A host on the Switch 1 hub sends a packet to a host on Switch 2.
The hub on Switch1 broadcasts the packet to all ports, except the source.
Switch 1 sends packet to Switch 2.
Switch 2 sends packet to the destination host on the hub.
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3.4.3 Function of Switches
The diagram depicts an activity in which you must answer the questions for each of the scenarios. There are two switches, labeled Switch 1 and Switch 2. There is one hub, labeled Hub 1.
Switch 1 is connected to Switch 2.
Switch 1 is also connected to Hub 1.
Hub 1 has four PCs connected, labeled H1 through H4.
Switch 1 has four PCs connected, labeled H5 through H8.
Switch 2 has four PCs connected, labeled H9 through H12.
Scenarios
One.What occurs if H9 and H12 send a message across Switch 2 at the same time?
The two frames will collide and the switch will forward a garbled massage to all hosts on the network.
The two frames will collide and the switch will forward a garbled message to the source and intended destination hosts only.
The two frames will be forwarded to the correct destination device without a collision occurring.
Two hosts cannot send information across the switch at the same time because the hosts must wait for a request for data frame from the switch.
Two.If H9 sends a message to H6, and the destination MAC address is in the MAC table for both Switch 1 and Switch 2, which host devices will receive the message?
only H6
all hosts connected to Switch 1
all hosts connected to Hub 1 and hosts connected to Switch 1
all hosts on the network
Three.In this network, how many collision domains exist?
There is one collision domain.
There are two collision domains.
There are three collision domains.
There are 10 collision domains.
There are 12 collision domains.
Four.If H8 sends a message to H1, and the destination MAC address is in the switch MAC table, which host devices will receive the message?
only H1
all hosts connected to Hub 1
all hosts connected to Switch 1
all hosts connected to Hub 1 and hosts connected to Switch 1
all hosts on the network
3.4.4 Broadcast Messaging
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When hosts are connected using either a hub or a switch, a single local network is created. Within the local network it is often necessary for one host to be able to send messages to all the other hosts at the same time. This can be done using a message known as a broadcast. Broadcasts are useful when a host needs to find information without knowing exactly what other host can supply it or when a host wants to provide information to all other hosts in the same network in a timely manner.
A message can only contain one destination MAC address. So, how is it possible for a host to contact every other host on the local network without sending out a separate message to each individual MAC?
To solve this problem, broadcast messages are sent to a unique MAC address that is recognized by all hosts. The broadcast MAC address is actually a 48-bit address made up of all ones. Because of their length, MAC addresses are usually represented in hexadecimal notation. The broadcast MAC address in hexadecimal notation is FFFF.FFFF.FFFF. Each F in the hexadecimal notation represents four ones in the binary address.
3.4.4 Broadcast Messaging
Two Diagrams
Diagram 1, Animation
The diagram depicts a message broadcast. The source sends a message to every other node on the network.
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When a host receives a message addressed to the broadcast address, it accepts and processes the message as though the message was addressed directly to it. When a host sends a broadcast message, hubs and switches forward the message to every connected host within the same local network. For this reason, a local network is also referred to as a broadcast domain.
If too many hosts are connected to the same broadcast domain, broadcast traffic can become excessive. The number of hosts and the amount of network traffic that can be supported on the local network is limited by the capabilities of the hubs and switches used to connect them. As the network grows and more hosts are added, network traffic, including broadcast traffic, increases. It is often necessary to divide one local network, or broadcast domain, into multiple networks to improve performance.
3.4.4 Broadcast Messaging
Diagram 2, Image
The diagram depicts three sections of a company: Sales, Production, and Marketing. Each of the three sections is a separate broadcast domain.
3.4.5 Switch Behavior
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3.4.5 Switch Behavior
Single Diagram
Diagram 1, Activity
The diagram depicts an activity in which you must answer the question for each scenario.
The diagram depicts a 12-port switch with the following devices attached to the given ports:
FA 1 - 0A
FA 3 - 0B
FA 5 - 0C
FA 7 - 0D
FA 9 - hub with 0E, 0F attached
For each practice problem, a sample frame is generated with a source and destination address shown. The MAC table is also populated with various entries for the practice problem. Based on the source and destination address in the frame and the addresses learned in the switch MAC table, select each port to which the frame will be forwarded for Question 1. Select which statements are true based on the scenario for Question 2.
Scenarios
One. Where will the switch forward the frame?
The choices are FA 1 through FA 12.
Two. When the switch forwards the frame, which of the following statements are true?
Switch adds the source MAC address to the MAC table.
Frame is a broadcast frame and will be forwarded to all ports.
Frame is a unicast frame and will be sent to a specific port only.
Frame is a unicast frame and will be flooded to all ports.
Frame is a unicast frame but it will be dropped at the switch.
3.4.6 MAC and IP
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On a local Ethernet network, a NIC only accepts a frame if the destination address is either the broadcast MAC address, or else corresponds to the MAC address of the NIC.
Most network applications, however, rely on the logical destination IP address to identify the location of the servers and clients.
What if a sending host only has the logical IP address of the destination host? How does the sending host determine what destination MAC address to place within the frame?
The sending host can use an IP protocol called address resolution protocol (ARP) to discover the MAC address of any host on the same local network.
3.4.6 MAC and IP
Single Diagram
Diagram 1, Image
The diagram depicts a switch with four PC's attached, H1 through H4.
H1 - 192.168.1.5
H2 - 192.168.1.6
H3 - 192.168.1.7
H4 - 192.168.1.8
There are speech bubbles in the diagram. H1 says, I need to send information to 192.168.1.7, but I only have the IP address. I do not know which device has that IP.The PC will need to use Address Resolution Protocol (ARP) to discover the MAC address of the host with IP address 192.168.1.7, in order to communicate with it.
3.4.7 Address Resolution Protocol (ARP)
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ARP uses a three step process to discover and store the MAC address of a host on the local network when only the IP address of the host is known.
1. The sending host creates and sends a frame addressed to a broadcast MAC address. Contained in the frame is a message with the IP address of the intended destination host.
2. Each host on the network receives the broadcast frame and compares the IP address inside the message with its configured IP address. The host with the matching IP address sends its MAC address back to the original sending host.
3. The sending host receives the message and stores the MAC address and IP address information in a table called an ARP table.
Once the sending host has the MAC address of the destination host in its ARP table, it can send frames directly to the destination without doing an ARP request.
3.4.7 Address Resolution Protocol (ARP)
Single Diagram
Diagram 1, Animation
The animation demonstrates the use of ARP to find the MAC address of a destination host, when an IP address is known. Example is from 3.4.6. The process is explained within the body text.
3.5 Building the Distribution Layer of Network
3.5.1 Distribution Layer
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As networks grow, it is often necessary to divide one local network into multiple Access Layer networks. There are many ways to divide networks based on different criteria, including:
* Physical location
* Logical function
* Security requirements
* Application requirements
The Distribution Layer connects these independent local networks and controls the traffic flowing between them. It is responsible for ensuring that traffic between hosts on the local network stays local. Only traffic that is destined for other networks is passed on. The Distribution Layer can also filter incoming and outgoing traffic for security and traffic management.
Networking devices that make up the Distribution Layer are designed to interconnect networks, not individual hosts. Individual hosts are connected to the network via Access Layer devices, such as hubs and switches. The Access Layer devices are connected to each other via the Distribution Layer device, such as routers.
3.5.1 Distribution Layer
Single Diagram
Diagram 1, Interactive
The diagram depicts four boxes, each labeled with following headings: Broadcast Containment, Security, Locations, and Logical Grouping. More information is given below.
Broadcast Containment
Routers in the Distribution Layer can limit broadcasts to the local network where they need to be heard. Although broadcasts are necessary, too many hosts connected on the same local network can generate excessive broadcast traffic and slow down the network.
Security
Routers in the Distribution Layer can separate and protect certain groups of computers where confidential information resides. Routers can also hide the addresses of internal computers from the outside world to help prevent attacks and control who can get into or out of the local network.
Locations
Routers in the Distribution Layer can be used to interconnect local networks at various locations of an organization that are geographically separated.
Logical Grouping
Routers in the Distribution Layer can be used to logically group users, such as departments within a company, who have common needs or for access to resources.
3.5.2 Function of Routers
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A router is a networking device that connects a local network to other local networks. At the Distribution Layer of the network, routers direct traffic and perform other functions critical to efficient network operation. Routers, like switches, are able to decode and read the messages that are sent to them. Unlike switches, which only decode (unencapsulate) the frame containing the MAC address information, routers decode the packet that is encapsulated within the frame.
The packet format contains the IP addresses of the destination and source hosts, as well as the message data being sent between them. The router reads the network portion of the destination IP address and uses it to find which one of the attached networks is the best way to forward the message to the destination.
Anytime the network portion of the IP addresses of the source and destination hosts do not match, a router must be used to forward the message. If a host located on network 1.1.1.0 needs to send a message to a host on network 5.5.5.0, the host will forward the message to the router. The router receives the message and unencapsulates it to read the destination IP address. It then determines where to forward the message. It re-encapsulates the packet back into a frame, and forwards the frame on to its destination.
3.5.2 Function of Routers
Three Diagrams
Diagram 1, Animation
The diagram depicts an IP packet encapsulated in an Ethernet Frame.
The Ethernet frame consists of the destination MAC address (moving left to right within the frame), followed by the source MAC address. The destination and source MAC address sections of the frame are read by Layer 2 devices, such as a switch or bridge.
The source and destination MAC addresses are as follows:
Source MAC address AA:AA:AA:AA:AA:AA.
Destination MAC BB:BB:BB:BB:BB:BB
The next fields in the frame are the destination IP and the source IP addresses. Depending on the subnet mask, some bits belong to the network portion and some belong to the host portion.
For example, with the address 192.168.1.5, the first three octets (192.168.1) belong to the network, and .5 belongs to the host.
In addition to the source and destination IP address, the IP packet contains the user data. The data is also known as the payload. The last part of the Ethernet frame is the trailer. The trailer finishes the encapsulation of the frame.
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Lab Activity
Assign different IP addresses on a peer-to-peer network, and view the effects on network communication.
Click the lab icon to begin.
3.5.2 Function of Routers
Diagram 2, Lab Activity
Link to Hands-on Lab: IP Addresses and Network Communication
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How does the router determine what path to send the message to get to the destination network?
Each port, or interface, on a router connects to a different local network. Every router contains a table of all locally-connected networks and the interfaces that connect to them. These routing tables can also contain information about the routes, or paths, that the router uses to reach other remote networks that are not locally attached.
When a router receives a frame, it decodes the frame to get to the packet containing the destination IP address. It matches the address of the destination to all of the networks that are contained in the routing table. If the destination network address is in the table, the router encapsulates the packet in a new frame in order to send it out. It forwards the new frame out of the interface associated with the path, to the destination network. The process of forwarding the packets toward their destination network is called routing.
Router interfaces do not forward messages that are addressed to the local network broadcast IP address. As a result, local network broadcasts are not sent across routers to other local networks.
3.5.2 Function of Routers
Diagram 3, Animation
The diagram depicts a network with a central router and three switches attached. Each switch has a number of hosts attached. Connected to the first switch are hosts H1 through H3. This switch connects to the router FA0/0 interface. The routers FA0/2 connects to another switch with host H4 attached. Another connection from the router connects to a switch with hosts H5 and H6 attached. The IP addresses are as follows:
H1 10.0.0.1
H2 10.0.0.2
H3 10.0.0.3
H4 192.168.1.2
H5 172.16.0.2
H6 172.16.0.1
H1 sends a packet out onto the network for the H4 client with the address 192.168.1.2. First, the message traverses the network based on forwarding decisions made by the switch. The switch examines the MAC address table to see if the entry is on the local network. If the MAC is not found, the packet is then forwarded to the default gateway. The router examines the routing table to see if the IP address entry exists, and whether there is a path to the destination network in the routing table. Once the path has been determined, the router sends the packet out of the appropriate interface so the message reaches the destination IP 192.168.1.2. If host H1 sends a broadcast message, all hosts connected to the switch on the 10.0.0.0 network receives the message. The router connected to this switch also receives the message but does not forward the broadcast. The message is discarded at the router.
3.5.3 Default Gateway
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The method that a host uses to send messages to a destination on a remote network differs from the way a host sends messages on the same local network. When a host needs to send a message to another host located on the same network, it will forward the message directly. A host will use ARP to discover the MAC address of the destination host. It includes the destination IP address within the packet and encapsulates the packet into a frame containing the MAC address of the destination and forwards it out.
On the other hand, when a host needs to send a message to a remote network, it must use the router. The host includes the IP address of the destination host within the packet just like before. However, when it encapsulates the packet into a frame, it uses the MAC address of the router as the destination for the frame. In this way, the router will receive and accept the frame based on the MAC address.
How does the source host determine the MAC address of the router? A host is given the IP address of the router through the default gateway address configured in its TCP/IP settings. The default gateway address is the address of the router interface connected to the same local network as the source host. All hosts on the local network use the default gateway address to send messages to the router. Once the host knows the default gateway IP address, it can use ARP to determine the MAC address. The MAC address of the router is then placed in the frame, destined for another network.
It is important that the correct default gateway be configured on each host on the local network. If no default gateway is configured in the host TCP/IP settings, or if the wrong default gateway is specified, messages addressed to hosts on remote networks cannot be delivered.
3.5.3 Default Gateway
Two Diagrams
Diagram 1, Interactive
The diagram depicts three hosts, H1, H2, and H3, connected to a switch. The switch is connected to a router. The router acts as the default gateway to the adjoining network segment. The default gateway IP address is 192.168.1.254. The default gateway is the near-side interface of the boundary router. Clicking on each host displays its IP address (192.168.1.x), subnet mask (255.255.255.0), and the address of the default gateway (192.168.1.254).
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3.5.3 Default Gateway
Diagram 2, Activity
The diagram depicts an activity in which you must enter the correct default gateway IP address for each host so that packets may traverse the network.
The router at the center of this network has three Fast Ethernet ports. Host H1 is connected to a switch, and the switch in turn is connected to the router on IP address 192.168.1.1. H2 is connected to a switch, and the switch in turn is connected to the router, IP address 10.0.0.1. H3 is connected to a switch, and the switch in turn is connected to the router, IP address 172.16.0.50. Clicking each host displays the TCP/IP Properties window where the default gateway address for H1, H2, and H3 may be entered.
3.5.4 Tables Maintained by Routers
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Routers move information between local and remote networks. To do this, routers must use both ARP and routing tables to store information. Routing tables are not concerned with the addresses of individual hosts. Routing tables contain the addresses of networks and the best path to reach those networks. Entries can be made to the routing table in two ways: dynamically updated by information received from other routers in the network, or manually entered by a network administrator. Routers use the routing tables to determine which interface to use to forward a message to its intended destination.
If the router cannot determine where to forward a message, it will drop it. Network administrators configure a routing table with a default route to keep a packet from being dropped because the path to the destination network is not in the routing table. A default route is the interface through which the router forwards a packet containing an unknown destination IP network address. This default route usually connects to another router that can forward the packet towards its final destination network.
3.5.4 Tables Maintained by Routers
Three Diagrams
Diagram 1, Interactive
The diagram depicts a network with one router, two switches, and four hosts per switch. The hosts are labeled H1 through H8. The routers Fast Ethernet FA0/0 is connected to Switch 1. The IP addressing scheme for the four clients connected to the switch are 10.1.21.1 through 10.1.21.4. The routers second Fast Ethernet FA0/1 is connected to Switch 2. The IP addressing scheme for the four clients H5 through H8 is 172.16.1.3 through 172.16.1.6, respectively. Two tables are kept and updated by the router: the Address Resolution Protocol (ARP) table and the Routing table. The entries into these tables are listed below:
ARP TABLE
AddressHardware AddressInterface
10.1.21.1 0002.a5ec.c7f9 Fast Ethernet 0/0
10.1.21.2 0012.3fec.fb0d Fast Ethernet 0/0
10.1.21.3 0014.220e.dac5 Fast Ethernet 0/0
10.1.21.4 00c0.9f4b.8b76 Fast Ethernet 0/0
172.16.1.3 0ac3.a56c.d7f5 Fast Ethernet 0/1
172.16.1.4 0a2f.4fed.dd0d Fast Ethernet 0/1
172.16.1.5 0b03.3002.ea2d Fast Ethernet 0/1
172.16.1.6 0d00.a94b.8caa Fast Ethernet 0/1
ROUTING TABLE
TypeNetwork Port
C10.0.0.0/8 FastEthernet0/0
C172.16.0.0/8 FastEthernet0/1
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A router forwards a frame to one of two places: a directly connected network containing the actual destination host, or to another router on the path to reach the destination host. When a router encapsulates the frame to forward it out of an Ethernet interface, it must include a destination MAC address.
This is the MAC address of the actual destination host, if the destination host is part of a network locally connected to the router. If the router must forward the packet to another router, it will use the MAC address of the connected router. Routers obtain these MAC addresses from ARP tables.
Each router interface is part of the local network to which it is attached and maintains its own ARP table for that network. The ARP tables contain the MAC addresses and IP addresses of all of the individual hosts on that network.
3.5.4 Tables Maintained by Routers
Diagram 2, Animation
The diagram is a two-part animation. The diagram depicts three local networks joined to a router. The topology is as follows: H1 through H3 are connected to Switch 1, which in turn connects to the router. H4 through H6 are connected to Switch 2, which in turn connects to the router. H7 through H9 are connected to Switch 3, which in turn connects to the router. There are speech bubbles in the diagram, as follows:
The first part shows the step to send a packet from one host to another host on the local network.
LOCAL NETWORK
H1 says, I need to send a packet to IP address 192.168.1.3. That IP is in my local network.
The IP and MAC addresses are in my ARP table, I will forward it directly.
Note that the packet does not leave the local network.
The second part of the animation shows the steps to send a packet from a host on one local network to a host on a remote local network:
REMOTE NETWORK
H1 says, I need to send a packet to IP address 192.168.2.1 (H4). That IP is not in my local network. This packet must be sent to my default gateway for forwarding. I have the default gateways IP and MAC address in my ARP table.
Router 1 says, This host (H4) is on a network directly connected on one of my other interfaces. I will check my ARP table. There he is, now I can forward the packet.
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3.5.4 Tables Maintained by Routers
Diagram 3, Activity
The diagram depicts an activity in which you must determine how the router forwards a packet based on the source and destination IP address in the frame (encapsulated IP packet) and the information in the route table.
Route Table
The route table entries do not change and are as follows:
Type Network PortNext Hop Metric
C192.168.3.0/24 Ethernet 0/0--0/0
C172.16.1.0/24 Ethernet 0/1--0/0
C10.5.5.0/24 Ethernet 0/2--0/0
Frame
In the activity, random practice problems are generated with different source and destination IP addresses in the Frame.
An example of a practice scenario includes the following frame IP address information:
Destination IP: 192.168.3.5
Source IP: 10.5.5.8
Scenarios
One. What is the default gateway address used to forward this packet to the router?
192.168.3.1
172.16.1.1
10.5.5.1
Two. When the router receives this packet, to which interface will the router forward the packet?
Ethernet1/1
Ethernet1/2
Ethernet1/3
3.5.5 Local Area Network (LAN)
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The term Local Area Network (LAN) refers to a local network, or a group of interconnected local networks that are under the same administrative control. In the early days of networking, LANs were defined as small networks that existed in a single physical location. While LANs can be a single local network installed in a home or small office, the definition of LAN has evolved to include interconnected local networks consisting of many hundreds of hosts, installed in multiple buildings and locations.
The important thing to remember is that all of the local networks within a LAN are under one administrative control. Other common characteristics of LANs are that they typically use Ethernet or wireless protocols, and they support high data rates.
The term Intranet is often used to refer to a private LAN that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization.
3.5.5 Local-Area Network (LAN)
Two Diagrams
Diagram1, Interactive
The diagram depicts two networks, a network that has multiple local networks and a network that is a single local network. The topology for each of these networks is as follows:
Multiple Local Network
The router is at the center of this topology with three switches directly connected to the router. Switch 1 has three computers connected, H1 through H3, and a network address of 192.168.1.0. Switch 2 has three computers connected, H4 through H6, and a network address of 192.168.2.0. The final network has Switch 3 with three hosts connected, H7 through H9, and a network address of 192.168.3.0. The router acts as the joining point for the three networks.
Single Local Network
The single local network consists of three switches and nine hosts. The router has been removed. Switch 1 is directly connected to Switch 3. Switch 2 is also directly connected to Switch 3. Switch 1 has three computers connected, H1 through H3. Switch 2 has three computers connected, H4 through H6, and Switch 3 has three connected, H7 through H9. The network address assigned to this network is 192.168.1.0. All hosts share this network number.
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3.5.5 Local-Area Network (LAN)
Diagram 2, Activity
The diagram depicts an activity in which you must identify how many local networks are in the LAN in the diagram. The topology is as follows:
A router is at the center. Directly connected to the router are four switches. Connected to Switch 1 is another switch with four computers. Switch 1 also has three computers directly connected to it. Switch 2 has three computers directly connected to it. Switch 3 has two computers directly connected to it. Switch 4 has a hub and three computers directly connected to it. Directly connected to the hub are two more computers.
3.5.6 Adding Hosts to Local and Remote Networks
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Within a LAN, it is possible to place all hosts on a single local network or divide them up between multiple networks connected by a Distribution Layer. The answer depends on desired results. Placing all hosts on a single local network allows them to be seen by all other hosts. This is because there is one broadcast domain and hosts use ARP to find each other.
In a simple network design it may be beneficial to keep all hosts within a single local network. However, as networks grow in size, increased traffic will decrease network performance and speed. In this case, it may be beneficial to move some hosts onto a remote network.
Placing additional hosts on a remote network will decrease the impact of traffic demands. However, hosts on one network will not be able to communicate with hosts on the other without the use of routing. Routers increase the complexity of the network configuration and can introduce latency, or time delay, on packets sent from one local network to the other.
3.5.6 Adding Hosts to Local and Remote Networks
Single Diagram
Diagram 1, Interactive
The diagram depicts two network topologies: a LAN consisting of a single local network, and a LAN consisting of multiple local networks connected by a central router. The conditions and characteristics for each of these networks are as follows:
LAN with all hosts on a single local network
In the diagram of a LAN with all hosts on a single local network topology, two switches directly connected to each other. Each switch is connected to five clients. Switch 1 has clients H1 through H5, and Switch 2 has clients H6 through H10.
ADVANTAGES
Appropriate for simpler networks.
Less complexity and lower network cost.
Allows devices to be "seen" by other devices.
Faster data transfer because of more direct communication.
Ease of device access.
DISADVANTAGES
All hosts are in one broadcast domain which causes more traffic on the segment and may slow network performance.
LAN with hosts on different networks.
In the diagram of a LAN with hosts on different networks, a single router has its two Fast Ethernet ports directly connected to two Layer 2 switches. Switch 1 has three hosts, H4 through H6, and Switch 2 has three hosts, H10 through H12.
ADVANTAGES
Appropriate for larger, more complex networks.
Splits up broadcast domains and decreases traffic.
Can improve performance on each segment.
Makes the machines invisible to those on other local network segments.
Can provide increased security.
Can improve network organization.
DISADVANTAGES
Requires the use of routing (Distribution Layer).
Router can slow traffic between segments.
More complexity and expense (requires router).
3.5.7 Learn to Use Packet Tracer
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3.5.7 Learn to Use Packet Tracer
Two Diagrams
Diagram 1, Animated Simulation
The diagram is an animated simulation.
Packet Tracer Window
Packet Tracer is a graphical learning and simulation tool Cisco developed to help model and understand how networks function. It enables you to build network topologies and test them by sending packets between devices and observing the interactions of protocols in use.
The diagram depicts the Packet Tracer application window in Windows XP. The animation demonstrates the use of the main Packet Tracer user interface features.
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Packet Tracer Activity
Become familiar with the user interface of Packet Tracer. Model a simple network and observe network behavior. Create an Ethernet network using two hosts and a hub and observe ARP, broadcast and ping (ICMP) traffic.
Click the Packet Tracer icon to begin.
3.5.7 Learn to Use Packet Tracer
Diagram 2, Packet Tracer Activity
Link to Packet Tracer Activity: Learn to Use Packet Tracer
Note: Packet Tracer is available for download from the Cisco Systems Academy homepage. On the right side of the page, there is the TOOLS option, where Packet Tracer can be found. Packet Tracer is currently being re-authored for use by the vision impaired and will be available shortly.
3.6 Plan and Connect a Local Network
3.6.1 Plan and Document an Ethernet Network
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Most local networks are based on Ethernet technology. This technology is both fast and efficient when used in a properly designed and constructed network. The key to installing a good network is planning before the network is actually built.
A network plan starts with the gathering of information about how the network will be used. This information includes:
* The number and type of hosts to be connected to network
* The applications to be used
* Sharing and Internet connectivity requirements
* Security and privacy considerations
* Reliability and uptime expectations
* Connectivity requirements including, wired and wireless
3.6.1 Plan and Document an Ethernet Network
Two Diagrams
Diagram 1, Interactive
The diagram depicts a man sitting at a desk in front of computer planning the physical topology and logical addressing scheme for a network. Network planning is crucial to installing a good network.
A network plan starts with the gathering of information about how the network will be used, as follows:
Number and type of hosts to be connected to network.
Where are the end users located? What type of hardware are they using? Where are the servers, printers, and other devices located?
Applications to be used.
What type of applications are running on the network?
Data and devices to be shared Who requires access to which files and network resources, such as printers?
Bandwidth requirements (speed) What is an acceptable speed for the end users? Do all users require the same throughput? What affect will the applications have on the throughput?
Security and privacy considerations.
Is the data being moved on the network of a personal or sensitive nature? Could unauthorized access to this information cause harm to anyone?
Reliability and up time expectations.
How important is the network? Does it need to be available 100% of the time, (this is known as up time)? How much downtime can be tolerated?
Connectivity requirements, including wired and wireless Do any or all of the end users require wireless connectivity?
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There are many considerations that must be taken into account when planning for a network installation. The logical and physical topology maps of the network need to be designed and documented before the networking equipment is purchased and the hosts are connected. Some things to consider include:
Physical environment where the network will be installed:
* Temperature control: all devices have specific ranges of temperature and humidity requirements for proper operation
* Availability and placement of power outlets
Physical configuration of the network:
* Physical location of devices such as routers, switches, and hosts
* How all devices are interconnected
* Location and length of all cable runs
* Hardware configuration of end devices such as hosts and servers
Logical configuration of the network:
* Location and size of broadcast and collision domains
* IP addressing scheme
* Naming scheme
* Sharing configuration
* Permissions
3.6.1 Plan and Document an Ethernet Network
Diagram 2, Interactive
The diagram depicts a campus network with two types of topologies, Physical and Logical.
Physical Topology
The physical topology encompasses all the physical media and devices that may be found in a network. Included in the physical topology is the physical location of devices, such as routers, switches, and hosts, as well as how all devices are interconnected. Also pertinent to design is the location and length of all cable runs, and hardware configuration of end devices such as hosts and servers.
Logical Topology
The logical topology defines the addressing scheme used to name and address all machines on the network. Logical topology includes the IP addressing scheme, naming scheme, sharing configuration, permissions, and the location and size of broadcast and collision domains.
3.6.2 Prototypes
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Once the network requirements are documented, and the physical and logical topology maps created, the next step in the implementation process is to test the network design. One of the ways to test a network design is to create a working model, or prototype, of the network.
Prototyping is essential as networks grow in size and complexity. A prototype allows a network administrator to test whether or not the planned network will operate as expected, before money is spent on equipment and installation. Documentation should be maintained on all aspects of the prototyping process.
Various tools and techniques are available for network prototyping; this includes real equipment set up in a lab environment, modeling and simulation tools. Packet Tracer is one example of a simulation and modeling tool that can be used for prototyping.
3.6.2 Prototypes
Three Diagrams
Diagram 1, Image
The diagram depicts a screen shot from Packet Tracer, which is a simulation program used for physical and logical network topology configuration so that issues in planning can be quickly corrected before implementation of the network takes place. Tools and techniques are available for network prototyping, including a lab environment set up with real equipment, and various simulation and modeling tools. Packet Tracer is an example of a simulation and modeling tool that can be used for prototyping.
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3.6.2 Prototypes
Diagram 2, Animated Simulation
The diagram depicts Packet Tracer in use. A prototype network topology is being designed, captured as a flash movie. As the file plays, several network devices are added to the blank topology work area. The scenario that the network is being planned for is a web server and two computers linked to the Ethernet switch portion of a Linksys WRT300N wireless router and Access Point (AP). These network devices are as follows, a Linksys WRT300N Wireless Router and 3 computers. After the network devices are added, the links between the devices are configured in terms of the media being used. Each host is connected to the switch portion of the WRT300N so a wired FastEthernet link icon is selected and used to connect the devices. Now that the physical topology is complete, the logical topology needs to be configured. Each network device on the page is selected and an appropriate IP address, subnet mask and default gateway is configured.
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Packet Tracer Activity
Prototype a simple network consisting of two hosts and a switch.
Click the Packet Tracer icon to begin.
3.6.2 Prototypes
Diagram 3, Packet Tracer Activity
Link to Packet Tracer Activity: Prototyping a Network
The diagram depicts a launch window for Packet Tracer. Clicking the icon will start Packet Tracer and open the exercise associated with this online page.
Note: For further assistance with this exercise, please refer to the VI Packet Tracer program that will be available online.
3.6.3 Multi-function Device
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Most home and small business networks do not require high-volume devices used in large business environments; smaller scale devices may well be suitable. However, the same functionality of routing and switching is required. This need has led to the development of products that have the functionality of multiple network devices, such as a router with switching functionality and a wireless access point. For the purpose of this course, multi-function devices will be referred to as integrated routers. Integrated routers can range from small devices designed for home office and small business applications to more powerful devices that can support enterprise branch offices.
An integrated router is like having several different devices connected together. For example, the connection between the switch and the router still occurs, but it occurs internally. When a broadcast is received on a switch port, the integrated router forwards the broadcast to all ports including the internal router connection. The router portion of the integrated router stops the broadcasts from going any further.
There are low-cost multi-function devices available for home and small business networks that offer integrated routing, switching, wireless and security capabilities. An example of this type of integrated router is a Linksys wireless router. They are simple in design and do not typically have separate components. In the event of a failure, it is not possible to replace any single failed component. As such, they create a single point of failure, and are not optimized for any one function.
Another example of an integrated router is the Cisco integrated services router or ISR. The Cisco ISR product family offers a wide range of products, including those designed for small office and home office environments as well as those designed for larger networks. Many of the ISRs offer modularity and have separate components for each function, such as a switch component and a router component. This enables individual components to be added, replaced and upgraded as necessary.
3.6.3 MultiFunction Devices
Single Diagram
Diagram 1, Animation
The diagram depicts a Linksys WRT300N Wireless Router AP. This multifunction device contains three network devices that, when combined into one unit reduces costs and raises the level of functionality. It combines a switch, router, and access point (AP) into the one unit. Multifunction devices are useful because they combine the functions of many devices into a singular device.
3.6.4 Connecting the Linksys Router
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3.6.4 Connecting the Linksys Router
The diagram depicts the front and back view of the Linksys WRT300N Wireless Router. The views and the indicators are as follows:
Front View
Light Emitting Diodes (L E D) Descriptions
Power L E D - Indicates the presence of power to the device. It is a solid green L E D.
W LAN L E D Indicates status of wireless connections.
Ethernet L E D's (1-4) Indicates status of the wired Ethernet connections.
Internet L E D Indicates status of the Internet connection.
Color Status of L E D's:
Green indicates a connection has been made with an end device.
Red or Yellow usually indicates that there is problem with an end device.
Blinking indicates activity on the port.
Rear View
Internet Port:
A single port that is connected to the router portion of the multifunction device. This is used to connect the device to another network, such as the Internet. The router portion of a multifunction device maintains routing tables. There is an internal connection from the routing portion of the multifunction device to the switch portion. The Internet port is connected to a different network than the Ethernet.
Ethernet Ports:
Multiple ports that are connected to the internal switch portion of the multifunction device. These are usually labeled, Ethernet. All devices connected to the switch ports are on the same local network. There is also an internal connection from the switch port to the router port (Internet port).
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All devices connected to the switch ports should be in the same broadcast domain. This means that all devices must have an IP address from the same network. Any device that has a different network portion within the IP address will not be able to communicate.
Additionally, Microsoft Windows makes use of computer names to identify other devices on the network. It is important to use these names as well as all IP address information in the planning and documentation to assist in future troubleshooting.
To display the current IP configuration in Microsoft Windows, use the command ipconfig. More detailed information, including host name, is available with the ipconfig /all. Document all information from the connection and configuration process.
Once hosts are communicating across the network, it is important to document network performance. This is known as determining the baseline for the network, and is used as an indication of normal operations. When comparing future network performance with the baseline, it can indicate if possible issues exist.
3.6.4 Connecting the Linksys Router
Diagram 2, Image
The diagram depicts the TCP/IP Properties window found in the Windows XP operating system.
The configuration of specific parameters are made using this window. All devices connected to the switch ports should be in the same broadcast domain. This means that all devices must have an IP address from the same network. Any device that has a different network portion within the IP address will not be able to communicate.
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Lab Activity
Build and document a simple pre-planned network using a networking device and two hosts and verify IP configuration.
Click the lab icon to begin.
3.6.4 Connecting the Linksys Router
Diagram 3, Lab Activity
Link to Hands-on Lab: Connect and Configure Hosts
Note: The document that pertains to this lab is available for download from the CAVI website.
3.6.5 Sharing Resources
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One of the most common purposes of networking is to share resources such as files and printers. Windows XP enables remote users to access a local machine and its resources through Sharing. It is important to consider security issues, and to assign specific permissions to shared resources.
By default, Windows XP uses a process known as Simple File Sharing. With Simple File Sharing, specific users and groups cannot be prevented from accessing shared files.
Simple File Sharing can be disabled so that more specific security access levels can be assigned. When this is done, the following permissions are available to assign to resources:
* Full Control
* Modify
* Read & Execute
* List Folder Contents
* Read
* Write
When a user accesses a file on a remote device, Windows Explorer allows the user to map a drive to a remote folder or resource. This maps a specific drive letter, for example M:, to the remote resource. This enables the user to treat the resource as though it was locally connected.
3.6.5 Sharing Resources
Three Diagrams
Diagram 1, Image
The diagram depicts a hand with an open folder in it. The open folder indicates that the person holding the folder wants to share information or resources with those around them.
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3.6.5 Sharing Resources
Diagram 2, Animated Simulation
The diagram depicts the Windows XP operating system desktop. The start menu has been selected. The flash file, when played, shows the steps taken to create a Share Folder on the local machine. A text file is then authored and copied to the Share Folder so that it can be accessed. It is then modified on the other network computer. This is done to show that the share folder can be seen and manipulated from another machine on the network.
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Lab Activity
Map a network drive and share a file.
Click the lab icon to begin.
3.6.5 Sharing Resources
Diagram 3, Lab Activity
Link to Hands-on Lab: Sharing Resources
Note: The document that pertains to this lab is available for download from the CAVI website.
3.7 Chapter Summary
3.7.1 Summary
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3.7.1 Summary
Eight Diagrams, Slider Graphic
Diagram 1, Image
The diagram depicts voice, video, and data converged networks.
Diagram 1 text
This chapter discussed basic concepts and benefits of networking, and the characteristics of local Ethernet networks.
Information networks can carry voice, video, and data.
Information networks consist of peripherals, hosts, network devices, and media.
Topology diagrams used to depict both logical and physical network design.
Hosts can play the role of client, server, or both.
Diagram 2, Image
The diagram depicts protocol characteristics.
Diagram 2 text
All communication has a source, a destination, and a channel.
Computer communications operate under special rules, called protocols.
Protocols define the characteristics of a message including: encoding, formatting, encapsulation, size, timing, and patterns.
Diagram 3, Image
The diagram depicts the network protocol evolution.
Diagram 3 text
To communicate on a local network requires the computers share a common protocol.
The most common protocol used on local wired networks is industry standard Ethernet.
Each local host in an Ethernet network is identified by a physical MAC address, which is pre configured into a hosts NIC.
Proprietary Vendor Protocols (1970's) IBM, NCR, Xerox, D E C, HP
Limited Number of standards (1980's and 1990's) Ethernet (IEEE 8 0 2 dot 3), ARCnet (IEEE 8 0 2 dot 4), Token Ring (IEEE 8 0 2 dot 5)
And the winner is Ethernet (2000)
Diagram 4, Image
The diagram depicts hierarchical network design.
Diagram 4 text
It is common to divide larger networks into smaller, more manageable ones using a layered hierarchical design, which can include the following layers:
Access
Distribution
Core
Each of these layers has a primary function and associated devices.
Diagram 5, Image
The diagram depicts routed network using logical and physical addressing.
Diagram 5 text
Logical IP addresses are used to identify the location of a host within this hierarchical design.
To deliver a packet to an individual host requires both a physical MAC address and a logical IP address.
ARP is used to resolve an IP address to a MAC address for local delivery.
Diagram 6, Image
The diagram depicts hierarchical network design.
Diagram 6 text
Access Layer
The Access Layer is the first point of entry into the network for all hosts.
Hosts are usually directly connected using Ethernet cables to an Access Layer device, such as a hub or switch.
MAC address and IP addresses are used on the local network at the Access Layer.
Distribution Layer
The Distribution Layer connects independent local networks and controls traffic between them.
Individual hosts are not usually connected directly to the Distribution Layer devices.
Routers are the main networking device within the Distribution Layer and use IP addresses to move packets between networks.
Diagram 7, Image
The diagram depicts network planning.
Diagram 7 text
A network plan starts with the gathering of information about how the network will be used. This information includes the following parameters:
The number and type of hosts to be connected to the network.
The applications to be used.
Sharing and Internet connectivity requirements.
Security and privacy considerations.
Reliability and up time expectations.
Connectivity requirements, including wired and wireless.
Diagram 8, Image
The diagram depicts a WRT300N wireless router multifunction device.
Diagram 8 text
Cisco ISR's, and other multifunction networking devices connect home and small business networks in order for multiple hosts to share resources and to connect to the Internet.
A home networking device is a simplified low cost device commonly used in small networks.
These devices typically provide the functionality of a switch, router, and wireless access point in one device.
3.8 Chapter Quiz
3.8.1 Quiz
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Take the chapter quiz to check your knowledge.
Click the quiz icon to begin.
3.8.1 Quiz
12 Questions
1.The diagram depicts an IP telephone connected to a switch. Also connected to the switch are two computers, directly connected to one of the computers is a standalone printer.
Refer to the description above. What two types of devices are the printer and the IP phone? (Choose two.)
The IP phone is a peripheral.
The IP phone is a host.
The IP phone is a network device.
The printer is a peripheral.
The printer is a host.
The printer is a network device.
2. Determine if the characteristics listed are an advantage or disadvantage of a peer to peer network.
Advantages
Disadvantages
Provide minimal security.
No centralized administration.
Inexpensive.
Potential impact on performance.
Easy to set up.
No special hardware.
3.List whether the statements below are related to a Logical Topology Map or a Physical Topology Map.
Logical Topology Map
Physical Topology Map
Shows wiring installations.
Shows location of networking devices.
Shows host names and host addresses.
Shows group information and applications used.
Shows location of each host and how they connect to the network.
Shows location of broadcast and collision domains.
4. Match the situation with the correct type of message that would be used.
Unicast
Multicast
Broadcast
A host device sends a hello message to all computers on the network.
A host device sends an email to another host device.
A host device joins a group to receive video conferencing.
A host device requests a web page and displays the results.
A host device sends out an ARP request looking for the MAC address for a specific IP address.
A router forwards its routing table to a specific group of routers on the network.
5. Which two statements accurately describe a router ARP table and routing table? (Choose two)
The ARP table contains information about individual devices, not networks.
The ARP table contains information about networks, not individual devices.
The ARP table contains information about networks and individual devices.
The routing table contains information about individual devices, not networks.
The routing table contains information about networks, not individual devices.
The routing table contains information about networks and individual devices.
6.What process can a user perform on the host so that a folder on a remote server is treated as if it were a local resource?
mapping a drive
sharing a drive
enabling a remote user
setting share permissions
7.Determine if the tasks performed would be considered the role of a client, server, or both. Match the task with the role of Client, Server or Both Client and Server.
Client
Server
Client and Server
Share files with another device.
Download a music file from a website.
Play a video game with a friend across a network.
Participate in a videoconference with another computer.
Connect to an e learning site to learn networking
Store e-mail and deliver it upon request.
8.The diagram depicts two switches named Switch A and Switch B directly connected to each other. H1 and H2 are directly connected to switch A and H3 and H4 are directly connected to switch B.
Refer to the description above. If H1 on Switch A needs to forward to H3 on Switch B, which MAC address is used as the destination MAC within the frame?
MAC address of H1
MAC address of Switch A
MAC address of Switch B
MAC address of H3
9.The diagram depicts two network segments, LAN A and LAN B, directly connect to Router1 via Switch1 and Switch2. Computer1 is located on Switch1 and Computer10 is located on Switch2.
Refer to the description above. When Router1 receives a message with a source address of Computer1 on LAN A and a destination address of Computer10 on LAN B, what will be the action of Router 1?
The router checks its ARP table to determine where to forward the packet to reach Computer10.
The router checks it ARP table to determine the appropriate IP address of Computer10.
The router checks its routing table to determine where to forward the packet to reach Computer10.
The router checks its routing table to determine the appropriate MAC address of Computer10.
10.Which three pieces of information are included in a network physical map? (Choose three)
IP addressing scheme.
Computer naming scheme.
Location and length of cable runs.
Physical location of all networking devices.
Location and size of broadcast and collision domains.
Hardware configuration of end devices such as hosts and services.
11.When using Windows XP, which command shows information about the computer, including IP address, subnet mask, default gateway, and additional details about DHCP and DNS?
i p config
win i p cfg
i p config/all
win i p cfg/all
12.In what area of a network can traffic from other hosts cause a sending host to stop transmitting, then wait a random amount of time before resending a message?
access layer
broadcast domain
collision domain
distribution layer
peer to peer network
3 Connecting to the Network
3.0 Chapter Introduction
3.0.1 Introduction
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3.0.1 Introduction
Single Diagram
Diagram 1, Slide show
More and more, it is networks that connect us. People communicate online from everywhere.
Conversations in coffeehouses spill into chat rooms. Online debates continue at school.
Efficient, reliable technology enables networks to be available whenever and wherever we need them.
In this chapter, you will learn how communication occurs over a network and about the many different components that need to operate together to make it work.
After completion of this chapter, you should be able to:
Explain the concept of networking and the benefits of networks.
Explain the concept of communication protocols.
Explain how communication occurs across a local Ethernet network.
Describe Access Layer devices and communication methods on a local Ethernet network.
Describe Distribution Layer devices and communication methods across networks.
Plan, implement, and verify a local network.
3.1 Introduction to Networking
3.1.1 What is a Network?
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There are many types of networks that provide us with different kinds of services. In the course of a day, a person might make a phone call, watch a television show, listen to the radio, look up something on the Internet, or even play a video game with someone in another country. All of these activities depend on robust, reliable networks. Networks provide the ability to connect people and equipment no matter where they are in the world. People use networks without ever thinking about how they work or what it would be like if the networks did not exist.
This picture of the airport illustrates people using networks to share information, use resources and communicate with others. There are multiple types of networks shown in this scene. How many can you find?
3.1.1 What is a Network?
Two Diagrams
Diagram 1, Interactive
The diagram depicts people using the following network types. Hovering the mouse over items in the picture displays the text associated with that item.
Computer/Data Network
Provides communications between computer users via copper, fiber optic and wireless connections.
Television Network
Provides regular and high definition broadcasts over the air via cable and satellite networks.
Telephone Network
Connects callers and allows modem connections via traditional land lines.
Mobile Phone Network
Connects mobile callers to voice, text, and Internet via the mobile phone system.
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Communication technology in the 1990s, and before, required separate, dedicated networks for voice, video and computer data communications. Each of these networks required a different type of device in order to access the network. Telephones, televisions, and computers used specific technologies and different dedicated network structures, to communicate. But what if people want to access all of these network services at the same time, possibly using a single device?
New technologies create a new kind of network that delivers more than a single type of service. Unlike dedicated networks, these new converged networks are capable of delivering voice, video and data services over the same communication channel or network structure.
New products are coming to market that take advantage of the capabilities of converged information networks. People can now watch live video broadcasts on their computers, make a telephone call over the Internet, or search the Internet using a television. Converged networks make this possible.
In this course, the term network refers to these new multi-purpose, converged information networks.
3.1.1 What is a Network?
Diagram 2, Animation
The diagram depicts the following independent network types, Voice Network, Computer Network, and Video Network, and shows how all three converge to become a single Information Network that carries all three types of traffic.
3.1.2 Benefits of Networking
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Networks come in all sizes. They can range from simple networks consisting of two computers, to networks connecting millions of devices. Networks installed in small offices, or homes and home offices, are referred to as SOHO networks. SOHO networks enable sharing of resources, such as printers, documents, pictures and music between a few local computers.
In business, large networks can be used to advertise and sell products, order supplies, and communicate with customers. Communication over a network is usually more efficient and less expensive than traditional forms of communication, such as regular mail or long distance phone calls. Networks allow for rapid communication such as email and instant messaging, and provide consolidation, storage, and access to information on network servers.
Business and SOHO networks usually provide a shared connection to the Internet. The Internet is considered a "network of networks" because it is literally made up of thousands of networks that are connected to each other.
Here are other uses of a network and the Internet:
* Sharing music and video files
* Research and on-line learning
* Chatting with friends
* Planning vacations
* Purchasing gifts and supplies
Can you think of other ways people use networks and the Internet in their daily lives?
3.1.2 Benefits of Networking
Single Diagram
Diagram 1, Interactive
Small Home Networks
Small home networks connect a few computers to each other and the Internet.
Small Office/Home Office Networks
The Small Office/Home Office (SOHO) network enables computers within a home or remote office to connect to a corporate network, and have access to centralized, shared resources.
Medium to Large Networks
Medium to large networks, such as those used by corporations and schools, can have many locations with hundreds or thousands of interconnected computers.
Worldwide Networks
The Internet is a network of networks that connects hundreds of millions of computers worldwide.
3.1.3 Basic Network Components
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There are many components that can be part of a network, for example personal computers, servers, networking devices, and cabling. These components can be grouped into four main categories:
* Hosts
* Shared peripherals
* Networking devices
* Networking media
The network components that people are most familiar with are hosts and shared peripherals. Hosts are devices that send and receive messages directly across the network.
Shared peripherals are not directly connected to the network, but instead are connected to hosts. The host is then responsible for sharing the peripheral across the network. Hosts have computer software configured to enable people on the network to use the attached peripheral devices.
The network devices, as well as networking media, are used to interconnect hosts.
Some devices can play more than one role, depending on how they are connected. For example, a printer directly connected to a host (local printer) is a peripheral. A printer directly connected to a network device and participates directly in network communications is a host.
3.1.3 Basic Network Components
Two Diagrams
Diagram 1, Interactive
The diagram depicts several networking devices, including a PC, scanner, local printer, hub, switch, network printer, laptop, server, and webcam. There is a brief description about each of the categories that the devices belong to.
Peripherals
Shared peripheral devices do not communicate directly on the network. Instead, peripherals rely on their connected host to perform all network operations. Examples of peripherals are cameras, scanners, and locally attached printers. Printers and scanners can be shared.
Hosts
Hosts send and receive user traffic. A host is a generic name for most end user devices. A host has an IP network address. Examples of hosts are personal computers and network attached printers.
Network Devices
Networking devices connect other devices, mainly hosts. These devices move and control network traffic. Examples of network devices include hubs, switches, and routers.
Network Media
Network media provides connections between hosts and network devices. Network media can be wired, such as copper and fiber optic, or use wireless technologies.
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3.1.3 Basic Network Components
Diagram 2, Activity
The diagram depicts an activity in which you must match different types of networking components with the correct category.
Category
One.Peripheral
Two.Host
Three.Network Media
Four.Network Device
Devices
A:Network Printer
B:Switch
C:Hub
D:MP3 Player
E:PC
F:Laptop
G:Local Printer
H:Network Cable
I:Server
3.1.4 Computer Roles in a Network
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All computers connected to a network that participate directly in network communication are classified as hosts. Hosts can send and receive messages on the network. In modern networks, computer hosts can act as a client, a server, or both. The software installed on the computer determines which role the computer plays.
Servers are hosts that have software installed that enable them to provide information, like email or web pages, to other hosts on the network. Each service requires separate server software. For example, a host requires web server software in order to provide web services to the network.
Clients are computer hosts that have software installed that enable them to request and display the information obtained from the server. An example of client software is a web browser, like Internet Explorer.
3.1.4 Computer Roles in a Network
Three Diagrams
Diagram 1, Interactive
The diagram depicts common network server and client device pairs and gives a brief description of how they interact.
Email Server and Email Client
The email server runs server software. The client uses mail client software, such as Microsoft Outlook, to access email on the server.
Web Server and Browser Client
The web server runs server software. Clients use browser software, such as Windows Internet Explorer, to access web pages on the server.
File Server and File Access Client
The file server stores the files. A client device accesses the file with client software, such as Windows Explorer.
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A computer with server software can provide services simultaneously to one or many clients.
Additionally, a single computer can run multiple types of server software. In a home or small business, it may be necessary for one computer to act as a file server, a web server, and an email server.
A single computer can also run multiple types of client software. There must be client software for every service required. With multiple clients installed, a host can connect to multiple servers at the same time. For example, a user can check email and view a web page while instant messaging and listening to Internet radio.
3.1.4 Computer Roles in a Network
Diagram 2, Image
The diagram depicts a server running email services, web services, and file sharing services. The server has four clients attached, which are using the following services:
Computer 1 Web Browser, Email Client, File Access Client
Computer 2 Web Browser, File Access Client
Computer 3 File Access Client
Computer 4 Web Browser, Email Client
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3.1.4 Computer Roles in a Network
Diagram 3, Activity
The diagram depicts an activity in which you must identify the correct server, depending on the services a client wishes to use.
Client 1 Web Browser
Client 2 Email Client, Web Browser
Client 3 FTP Client, File Access Client
Client 4 Email Client
Server 1 Web Server, Email Server
Server 2 FTP Server, Email Server
Server 3 Web Server
Server 4 Web Server, File Server
3.1.5 Peer-to-Peer Networks
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Client and server software usually runs on separate computers, but it is also possible for one computer to carry out both roles at the same time. In small businesses and homes, many computers function as the servers and clients on the network. This type of network is called a peer-to-peer network.
The simplest peer-to-peer network consists of two directly connected computers using a wired or wireless connection.
Multiple PCs can also be connected to create a larger peer-to-peer network but this requires a network device, such as a hub, to interconnect the computers.
The main disadvantage of a peer-to-peer environment is that the performance of a host can be slowed down if it is acting as both a client and a server at the same time.
In larger businesses, due to the potential for high amounts of network traffic, it is often necessary to have dedicated servers to support the number of service requests.
3.1.5 Peer to Peer Networks
Three Diagrams
Diagram 1, Image/Tabular
The diagram depicts two connected PC's. PC1 is connected to a printer.
There are speech bubbles in the diagram, as follows:
PC1 says, I have a printer to share.
PC2 says, I have files to share.
The advantages of peer to peer networking:
Easy to set up.
Less complexity.
Lower cost since network devices and dedicated servers may not be required.
Can be used for simple tasks such as transferring files and sharing printers.
The disadvantages of peer to peer networking:
No centralized administration.
Not as secure.
Not scalable.
All devices may act as both clients and servers, which can slow their performance.
Tip Popup
Microsoft operating systems have built in server software which allows any computer to share stored files with other computers on the network. When you share a file, your computer is acting as a server. Also, Microsoft computer operating systems have built in client software which allows any computer to access shared files on another computer. When you access a shared file, your computer is acting as a client.
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3.1.5 Peer to Peer Networks
Diagram 2, Activity
The diagram depicts an activity in which you must identify different roles in a peer to peer network. For each of the four scenarios, indicate whether the computer is acting as a client, server, or both.
Scenarios
One.Trishna connects to the Internet and downloads a file from a site using a protocol called File Transfer Protocol. Is Trishna's computer acting as a client, server, or both?
Two.Juan connects into an e learning website to learn about networking. Is Juan's computer acting as a client, server, or both?
Three.Noriko has a dedicated computer used for sharing her files. Carlos is downloading a folder from Noriko's computer. Is Noriko's computer acting as a client, server, or both?
Four.Patti has a video game loaded on her computer. Donald has the same video game loaded on his computer. They are playing each other over the network. Is Donald's computer acting as a client, server, or both?
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Lab Activity
Build a simple peer-to-peer network using two PCs and an Ethernet crossover cable.
Click the lab icon to begin.
3.1.5 Peer to Peer Networks
Diagram 3, Lab Activity
Link to Hands on Lab: Building a Simple Peer to Peer Network
3.1.6 Network Topologies
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In a simple network consisting of a few computers, it is easy to visualize how all of the various components connect. As networks grow, it is more difficult to keep track of the location of each component, and how each is connected to the network. Wired networks require lots of cabling and network devices to provide connectivity for all network hosts.
When networks are installed, a physical topology map is created to record where each host is located and how it is connected to the network. The physical topology map also shows where the wiring is installed and the locations of the networking devices that connect the hosts. Icons are used to represent the actual physical devices within the topology map. It is very important to maintain and update physical topology maps to aid future installation and troubleshooting efforts.
In addition to the physical topology map, it is sometimes necessary to also have a logical view of the network topology. A logical topology map groups hosts by how they use the network, no matter where they are physically located. Host names, addresses, group information and applications can be recorded on the logical topology map.
The graphics illustrate the difference between logical and physical topology maps.
3.1.6 Network Topologies
Single Diagram
Diagram 1, Interactive
Physical Topology
The diagram depicts the physical layout of the network. For example, what is connected to what.
Logical Topology
The diagram depicts a diagram of the logical topology of the network, such as IP addressing.
3.2 Principles of Communication
3.2.1 Source, Channel, and Destination
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The primary purpose of any network is to provide a method to communicate information. From the very earliest primitive humans to the most advanced scientists of today, sharing information with others is crucial for human advancement.
All communication begins with a message, or information, that must be sent from one individual or device to another. The methods used to send, receive and interpret messages change over time as technology advances.
All communication methods have three elements in common. The first of these elements is the message source, or sender. Message sources are people, or electronic devices, that need to communicate a message to other individuals or devices. The second element of communication is the destination, or receiver, of the message. The destination receives the message and interprets it. A third element, called a channel, provides the pathway over which the message can travel from source to destination.
3.2.1 Source, Channel, and Destination
Single Diagram
Diagram 1, Animation
The diagram depicts the flow of information with respect to communication between two humans and then between two computers. In both cases, the message starts at the message source and is converted to a signal by the transmitter. The signal is transmitted over the transmission media and received by the receiver. At this point, it is reassembled as a message for the message destination.
3.2.2 Rules of Communication
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In any conversation between two people, there are many rules, or protocols, that the two must follow in order for the message to be successfully delivered and understood. Among the protocols for successful human communication are:
* Identification of sender and receiver
* Agreed-upon medium or channel (face-to-face, telephone, letter, photograph)
* Appropriate communication mode (spoken, written, illustrated, interactive or one-way)
* Common language
* Grammar and sentence structure
* Speed and timing of delivery
Imagine what would happen if no protocols or rules existed to govern how people communicate with each other. Would you be able to understand them? Are you able to read the paragraph that does not follow commonly accepted protocols?
3.2.2 Rules of Communication
Two Diagrams
Diagram 1, Interactive
The diagram depicts several lines of text that are difficult to understand if there are no protocols governing the structure of the information. The example below shows text that is displayed without using agreed upon protocols:
Humans communications between govern rules.
Itisverydifficulttounderstandmessagesthatarenotformattedanddonotfollowtheestablishedrulesandprotocols.
A estrutura da gramatica, da lingua, da pontuacao e do sentance faz a configuracao humana compreensivel por muitos individuos differentes.
Clicking the Translate button applies the protocol and translated text appears below:
Rules govern communications between humans.
It is very difficult to understand messages that are not correctly formatted and do not allow the established rules and protocols.
The structure of the grammar, the language, the punctuation, and the sentence make the configuration humanly understandable for many different individuals.
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Protocols are specific to the characteristics of the source, channel and destination of the message. The rules used to communicate over one medium, like a telephone call, are not necessarily the same as communication using another medium, such as a letter.
Protocols define the details of how the message is transmitted, and delivered. This includes issues of:
* Message format
* Message size
* Timing
* Encapsulation
* Encoding
* Standard message pattern
Many of the concepts and rules that make human communication reliable and understandable also apply to computer communication.
3.2.2 Rules of Communication
Diagram 2, Image
The diagram depicts a box at the center of a star arrangement surrounded by six boxes, acting as nodes. The center box is labeled Protocols. The other six boxes are labeled: Encoding, Message Pattern, Timing, Message Size, Encapsulation, and Message Format. The diagram is suggesting that all of these characteristics are associated with protocols.
3.2.3 Message Encoding
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One of the first steps to sending a message is encoding it. Written words, pictures, and spoken languages each use a unique set of codes, sounds, gestures, and/or symbols to represent the thoughts being shared. Encoding is the process of converting thoughts into the language, symbols, or sounds, for transmission. Decoding reverses this process in order to interpret the thought.
Imagine a person watching a sunset and then calling someone else to talk about how beautiful the sunset looks. To communicate the message, the sender must first convert, or encode, their thoughts and perceptions about the sunset into words. The words are spoken into the telephone using the sounds and inflections of spoken language that convey the message. On the other end of the telephone line, the person listening to the description, receives and decodes the sounds in order to visualize the image of the sunset described by the sender.
Encoding also occurs in computer communication. Encoding between hosts must be in an appropriate form for the medium. Messages sent across the network are first converted into bits by the sending host. Each bit is encoded into a pattern of sounds, light waves, or electrical impulses depending on the network media over which the bits are transmitted. The destination host receives and decodes the signals in order to interpret the message.
3.2.3 Message Encoding
Single Diagram
Diagram 1, Animation
The diagram depicts two people standing next to each other conversing. The conversation flow is broken down into the following steps:
Human Communication
One.The girl begins the conversation. She is determined to be the message source.
Two.The girl processes the thought and begins the encoding of the message into English.
Three.The girl begins to speak in English to the boy. She defines herself at this stage as the transmitter. The audible signal generated by the girl as conversation is received by the boy. The transmission medium is the link between the boy and the girl, and this is defined as the channel.
Four.The receiver receives the communication from the girl and decodes the signal so he can understand the content.
Five.The receiver is known as the destination where decoding occurs.
Computer Communication
One.PC1 begins the communication. It is determined to be the message source.
Two.PC1 begins encoding of the message and transmits it to PC2.
Three.The digital signal generated by PC1 as a data stream is received by PC2. The transmission medium is the link between PC1 and PC2, which is defined as the channel.
Four.The receiver, PC2, receives the communication from PC1, and decodes the signal so it can understand the content.
Five.The receiver is known as the destination where decoding occurs.
3.2.4 Message Formatting
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When a message is sent from source to destination, it must use a specific format or structure. Message formats depend on the type of message and the channel that is used to deliver the message.
Letter writing is one of the most common forms of written human communication. For centuries, the agreed format for personal letters has not changed. In many cultures, a personal letter contains the following elements:
* An identifier of the recipient
* A salutation or greeting
* The message content
* A closing phrase
* An identifier of the sender
In addition to having the correct format, most personal letters must also be enclosed, or encapsulated, in an envelope for delivery. The envelope has the address of the sender and receiver on it, each located at the proper place on the envelope. If the destination address and formatting are not correct, the letter is not delivered.
The process of placing one message format (the letter) inside another message format (the envelope) is called encapsulation. De-encapsulation occurs when the process is reversed by the recipient and the letter is removed from the envelope.
3.2.4 Message Formatting
Three Diagrams
Diagram 1, Animation
Message Formatting
The diagram depicts the addressing and content of a letter being posted by snail mail from the sender to the receiver. This demonstrates the concepts of formatting and encapsulation and is depicted as an envelope and a letter inside the envelope. The components and addressing are as follows:
Envelope Addressing
One.Recipient (destination), Location Address: 1400 Main St, Canton, Ohio, 44203.
Two.Sender (source), Location Address: 4085 SE Pine St, Ocala, Florida, 34471.
Encapsulated Letter
Three.Salutation (start of message indicator), Dear
Four.Recipient (destination identifier), Jane
Five.Content of letter (encapsulated data), I just returned from my trip. I thought you might like to see my pictures.
Six.Sender (source identifier), John
Seven.End of frame (end of message indicator), Stamp and postmark
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A letter writer uses an accepted format to ensure that the letter is delivered and understood by the recipient. In the same way, a message that is sent over a computer network follows specific format rules for it to be delivered and processed. Just as a letter is encapsulated in an envelope for delivery, so computer messages are encapsulated. Each computer message is encapsulated in a specific format, called a frame, before it is sent over the network. A frame acts like an envelope; it provides the address of the intended destination and the address of the source host.
The format and contents of a frame are determined by the type of message being sent and the channel over which it is communicated. Messages that are not correctly formatted are not successfully delivered to or processed by the destination host.
3.2.4 Message Formatting
Diagram 2, Image
The diagram depicts the composition of a computer message sent from the sender to the recipient. The frame composition is as follows:
Frame Addressing
Destination (physical hardware address)
Source (physical hardware address)
End of Frame (end of message indicator)
Encapsulated Message
Start Flag (start of message indicator)
Recipient (destination identifier)
Sender (source identifier)
Encapsulated data (bits)
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3.2.4 Message Formatting
Diagram 3, Activity
The diagram depicts an activity in which you must match the components of the following voice messages to the proper locations within a frame.
The matching blocks of information are listed below:
Frame Composition
One.Destination location address
Two.Source location address
Three.Start of message flag
Four.Destination identifier address
Five.Message
Six.Source identifier address
Seven. End of message flag
Human Communication Components
A:Bye
B:Hello
C:This is Chris. Can you tell me what the math assignment is for today?
D:Tasha
E:000 555 2000
F:Chris
G:000 555 1000
3.2.5 Message Size
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Imagine what it would be like to read this course if it all appeared as one long sentence; it would not be easy to read and comprehend. When people communicate with each other, the messages that they send are usually broken into smaller parts or sentences. These sentences are limited in size to what the receiving person can process at one time. An individual conversation may be made up of many smaller sentences to ensure that each part of the message is received and understood.
Likewise, when a long message is sent from one host to another over a network, it is necessary to break the message into smaller pieces. The rules that govern the size of the pieces, or frames, communicated across the network are very strict. They can also be different, depending on the channel used. Frames that are too long or too short are not delivered.
The size restrictions of frames require the source host to break a long message into individual pieces that meet both the minimum and maximum size requirements. Each piece is encapsulated in a separate frame with the address information, and is sent over the network. At the receiving host, the messages are de-encapsulated and put back together to be processed and interpreted.
3.2.5 Message Size
Diagram 1, Animation
Human Communication
The diagram depicts a man and a woman communicating with each other. The woman starts the conversation with a sentence that is spoken very rapidly with no separation between words. The man receives this message and replies, I cannot understand. The woman receives this information and repeats the message, speaking at the correct speed. The man receives the information again, and this time he understands the message.
Computer Communication
The diagram depicts the communication between two computers. Computer 1 has an image it wants to send to Computer 2 located on the network. Computer 1 sends the image to Computer 2 as a complete transmission, which is one block of information. It sends this stream of information to Computer 2 who receives it and replies, I cannot understand the data you sent me as it is not formatted correctly or in the appropriate sizing blocks for me to understand. Computer 1 takes in this message from Computer 2 and resizes the image into smaller blocks of Information. The smaller blocks are re-assembled at the destination, or on Computer 2 in this case, so the image can be viewed as a single entity.
3.2.6 Message Timing
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One factor that affects how well a message is received and understood is timing. People use timing to determine when to speak, how fast or slow to talk, and how long to wait for a response. These are the rules of engagement.
Access Method
Access Method determines when someone is able to send a message. These timing rules are based on the environment. For example, you may be able to speak whenever you have something to say. In this environment, a person must wait until no one else is talking before speaking. If two people talk at the same time, a collision of information occurs and it is necessary for the two to back off and start again. These rules ensure communication is successful. Likewise, it is necessary for computers to define an access method. Hosts on a network need an access method to know when to begin sending messages and how to respond when errors occur.
Flow Control
Timing also effects how much information can be sent and the speed that it can be delivered. If one person speaks too quickly, it is difficult for the other person to hear and understand the message. The receiving person must ask the sender to slow down. In network communication, a sending host can transmit messages at a faster rate than the destination host can receive and process. Source and destination hosts use flow control to negotiate correct timing for successful communication.
Response Timeout
If a person asks a question and does not hear a response within an acceptable amount of time, the person assumes that no answer is coming and reacts accordingly. The person may repeat the question, or may go on with the conversation. Hosts on the network also have rules that specify how long to wait for responses and what action to take if a response timeout occurs.
3.2.6 Message Timing
Single Diagram
Diagram 1, Interaction
The diagram depicts three different aspects of message timing that are commonly used to control the flow of data between hosts, as described below:
Access Method
The man and the woman are communicating with each other. The woman begins the communication with a question, What time is the movie? The man also starts to talk. His question to the woman is, What time are we meeting for dinner? Because both are speaking (transmitting) at the same time, the message received by each person (or computer host) is not clear, so the message must be repeated (a re transmit is required). Both the man and the woman reply to their first attempt at communicating by saying to each other, Sorry, I did not understand you.
Flow Control
The woman and the man are communicating by telephone. The woman sends three quick messages, Hello, can you hear me?, Hello, can you hear me?, Hello, can you hear me? The man receives these messages but does not have an opportunity to respond, and cannot distinguish the beginning and the end of the message. He is unsure if the content has been received in its entirety or whether there has been a corruption in the stream of information that has caused the repetition.
Hence the mans reply is the symbol of a question mark.
Response Timeout
The diagram depicts a man and a woman on the telephone. The woman queries the man, Hello, can you hear me? The man does not respond. She repeats her question but there is still no response from the man. The woman tries one last time to communicate with the man. She is resolved at this point to stop her communication with the man, due to his lack of response.
3.2.7 Message Patterns
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Sometimes, a person wants to communicate information to a single individual. At other times, the person may need to send information to a group of people at the same time, or even to all people in the same area. A conversation between two people is an example of a one-to-one pattern of communication. When a group of recipients need to receive the same message simultaneously, a one-to-many or one-to-all message pattern is necessary.
There are also times when the sender of a message needs to be sure that the message is delivered successfully to the destination. In these cases, it is necessary for the recipient to return an acknowledgement to the sender. If no acknowledgement is required, the message pattern is referred to as unacknowledged.
Hosts on a network use similar message patterns to communicate.
A one-to-one message pattern is referred to as a unicast, meaning that there is only a single destination for the message.
When a host needs to send messages using a one-to-many pattern, it is referred to as a multicast. Multicasting is the delivery of the same message to a group of host destinations simultaneously.
If all hosts on the network need to receive the message at the same time, a broadcast is used. Broadcasting represents a one-to-all message pattern. Additionally, hosts have requirements for acknowledged versus unacknowledged messages.
3.2.7 Message Patterns
Single Diagram
Diagram 1, Interactive
The diagram depicts the three types of message patterns with reference to a single message source and one or more destinations. The definitions for unicast, multicast, and broadcast for both Human and Computer communication are as follows:
Human Communication
Unicast: Sent from the source person to one single person within the group.
Multicast: Sent from the source person to multiple people within the group.
Broadcast: Sent from the source person to all the people within the group.
Computer Communication
Unicast: Sent from the source to a single destination within a broadcast domain or a group of potential destinations.
Multicast: Sent from the source to multiple destinations within the broadcast domain or group of destinations.
Broadcast: Sent from the source to all the hosts within the broadcast domain or group of destinations.
3.2.8 Protocol Use in Communication
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All communication, both human and computer, is governed by pre-established rules, or protocols. These protocols are determined by the characteristics of the source, channel and destination. Based on the source, channel and destination, the protocols define the details for the issues of message format, message size, timing, encapsulation, encoding and standard message pattern.
3.2.8 Protocol Use in Communication
Two Diagrams
Diagram 1, Image
The diagram depicts a box at the center of a star arrangement surrounded by six other boxes, acting as nodes. The center box is labeled Protocols, and the other six boxes are labeled Encoding, Message Pattern, Timing, Message Size, Encapsulation, and Message Format. The diagram illustrates that all of these characteristics are defined by the protocol.
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3.2.8 Protocol Use in Communication
Diagram 2, Activity
The diagram depicts an activity in which you must match four keywords to thee definitions. Below is a list of keywords and the definitions that have to be matched:
KEYWORDS
A:Message Format
B:Timing
C:Encoding
D:Message Size
DEFINITIONS
One.Fred went to an auction and the auctioneer was talking so fast that Fred was unable to understand her.
Two.Andrea writes a letter and posts it to her friend. Unfortunately, Andrea mis addressed the letter and it never arrived.
Three.Mark is writing an English term paper at college. His instructor grades the paper and comments that his grade was reduced due to the excessive use of run on sentences and poor punctuation.
Four.An English only speaking individual on vacation in Germany could not order dinner with a German only speaking waiter.
3.3 Communicating on a Local Wired Network
3.3.1 Importance of Protocols
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Computers, just like humans, use rules, or protocols, in order to communicate.
Protocols are especially important on a local network. In a wired environment, a local network is defined as an area where all hosts must "speak the same language" or in computer terms "share a common protocol".
If everyone in the same room spoke a different language they would not be able to communicate. Likewise, if devices in a local network did not use the same protocols they would not be able to communicate.
The most common set of protocols used on local wired networks is Ethernet.
The Ethernet protocol defines many aspects of communication over the local network, including: message format, message size, timing, encoding, and message patterns.
3.3.1 Importance of Protocols
Single Diagram
Diagram 1, Image
The diagram depicts three people within a single room, communicating with each other in Japanese. The need for a universal protocol to be established between the communicating parties is necessary so that all participants understand each other. The diagram for the local area network (LAN) depicts four PC's connected to a switch. Within a LAN, the established language is Ethernet.
3.3.2 Standardization of Protocols
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In the early days of networking, each vendor used their own, proprietary methods of interconnecting network devices and networking protocols. Equipment from one vendor could not communicate with equipment from another.
As networks became more widespread, standards were developed that defined rules by which network equipment from different vendors operated. Standards are beneficial to networking in many ways:
* Facilitate design
* Simplify product development
* Promote competition
* Provide consistent interconnections
* Facilitate training
* Provide more vendor choices for customers
There is no official local networking standard protocol, but over time, one technology, Ethernet, has become more common than the others. It has become a de facto standard.
3.3.2 Standardization of Protocols
Two Diagrams
Diagram 1, Image
The diagram depicts the network communications protocols that were first developed by companies as proprietary protocols, and were for the most part vendor specific. The protocols established in the early 1970's were by IBM, NCR, Xerox, D E C, and HP. As time progressed, the 1980's brought about the development of major standardized protocols, such as Ethernet IEEE 8 0 2 dot 3, ARCnet 8 0 2 dot 4, and Token Ring 8 0 2 dot 5. With widespread expansion of the Internet in the 1990's, the eventual winner in the protocol race was Ethernet 8 0 2 dot 3 (circa 2000).
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The Institute of Electrical and Electronic Engineers, or IEEE (pronounced eye-triple-e), maintains the networking standards, including Ethernet and wireless standards. IEEE committees are responsible for approving and maintaining the standards for connections, media requirements and communications protocols. Each technology standard is assigned a number that refers to the committee that is responsible for approving and maintaining the standard. The committee responsible for the Ethernet standards is 802.3.
Since the creation of Ethernet in 1973, standards have evolved for specifying faster and more flexible versions of the technology. This ability for Ethernet to improve over time is one of the main reasons that it has become so popular. Each version of Ethernet has an associated standard. For example, 802.3 100BASE-T represents the 100 Megabit Ethernet using twisted pair cable standards. The standard notation translates as:
* 100 is the speed in Mbps
* BASE stands for baseband transmission
* T stands for the type of cable, in this case, twisted pair.
Early versions of Ethernet were relatively slow at 10 Mbps. The latest versions of Ethernet operate at 10 Gigabits per second and faster. Imagine how much faster these new versions are than the original Ethernet networks.
3.3.2 Standardization of Protocols
Diagram 2, Slider Graphic
The diagram depicts a timeline of the development of the Ethernet protocols. As the scroll bar is moved to the right into the more recent Ethernet protocols, a pipe transmitting packets continues to get larger and becomes capable of carrying more packets. Listed below is the date, the standard developed, and the description of the event:
1973: Ethernet Developed by Dr Robert Metcalf at Xerox Corp.
1980: D I X standard Digital Equipment Corp, Intel, and Xerox release a standard for 10Mbps Ethernet over coaxial
1983: IEEE 8 0 2 dot 3, 10BASE 5, 10Mbps Ethernet over thick coaxial cable
1985: IEEE 8 0 2 dot 3a, 10BASE 2, 10Mbps over thin coaxial cable
1990: IEEE 8 0 2 dot 3i, 10BASE T, 10Mbps Ethernet over twisted pair (TP)
1993: IEEE 8 0 2 dot 3j, 10BASE F, 10Mbps Ethernet over fiber optic
1995: IEEE 8 0 2 dot 3u, 100BASE xx, Fast Ethernet: 100Mbps Ethernet over twisted pair (TP) and fiber (various standards)
1998: IEEE 8 0 2 dot 3z, 1000BASE x, Gigabit Ethernet over fiber optic
1999: IEEE 8 0 2 dot 3a b, 1000BASE T, Gigabit Ethernet over twisted pair (TP)
2002: IEEE 8 0 2 dot 3a e, 10G BASE xx, 10 Gigabit Ethernet over fiber (various standards)
2006: IEEE 8 0 2 dot 3a n, 10G BASE T, 10 Gigabit Ethernet over twisted pair (TP)
3.3.3 Physical Addressing
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All communication requires a way to identify the source and destination. The source and destination in human communication are represented by names.
When a name is called, the person with that name listens to the message and responds. Other people in the room may hear the message, but they ignore it because it is not addressed to them.
On Ethernet networks, a similar method exists for identifying source and destination hosts. Each host connected to an Ethernet network is assigned a physical address which serves to identify the host on the network.
Every Ethernet network interface has a physical address assigned to it when it is manufactured. This address is known as the Media Access Control (MAC) Address. The MAC address identifies each source and destination host on the network.
Ethernet networks are cable based, meaning that a copper or fiber optic cable connects hosts and networking devices. This is the channel used for communications between the hosts.
When a host on an Ethernet network communicates, it sends frames containing its own MAC address as the source and the MAC address of the intended recipient. Any hosts that receive the frame will decode the frame and read the destination MAC address. If the destination MAC address matches the address configured on the NIC, it will process the message and store it for the host application to use. If the destination MAC address does not match the host MAC address, the NIC will ignore the message.
3.3.3 Physical Addressing
Two Diagrams
Diagram 1, Animation
The diagram depicts a hub at the center of a star topology with four PC's surrounding the hub. The PC's have been named H1 through H4 and have MAC (Media Access Control) addresses assigned as shown in the list below:
H1 AA:AA:AA:AA:AA:AA
H2 BB:BB:BB:BB:BB:BB
H3 CC:CC:CC:CC:CC:CC
H4 DD:DD:DD:DD:DD:DD
H1 is the source, and H3 is the destination. A speech bubble above H1 says, I need to send information to H3. The message transmits to all hosts on the network. There is a text box indicating the parameters of the framing of the transmission, as listed below:
Frame parameters
Frame Addressing (next 2 items)
Destination Address CC:CC:CC:CC:CC:CC
Source Address AA:AA:AA:AA:AA:AA
Data encapsulated data
All machines on the network reply in speech bubbles. After the transmission has reached them, H2 and H4 reply, This is not addressed to me, I shall ignore it. H3 replies, This is mine, and keeps the message.
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Lab Activity
Use the ipconfig /all command to display the MAC address of your computer.
Click the lab icon to begin.
3.3.3 Physical Addressing
Diagram 2, Lab Activity
Link to a Hands On Lab: Determine the MAC Address of a Host
3.3.4 Ethernet Communication
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The Ethernet protocol standards define many aspects of network communication including frame format, frame size, timing and encoding.
When messages are sent between hosts on an Ethernet network, the hosts format the messages into the frame layout that is specified by the standards. Frames are also referred to as Protocol Data Units (PDUs).
The format for Ethernet frames specifies the location of the destination and source MAC addresses, and additional information including:
* Preamble for sequencing and timing
* Start of frame delimiter
* Length and type of frame
* Frame check sequence to detect transmission errors
The size of Ethernet frames is limited to a maximum of 1518 bytes and a minimum size of 64 bytes from the Destination MAC Address field through the Frame Check Sequence. Frames that do not match these limits are not processed by the receiving hosts. In addition to the frame formats, sizes and timing, Ethernet standards define how the bits making up the frames are encoded onto the channel. Bits are transmitted as either electrical impulses over copper cable or as light impulses over fiber optic cable.
3.3.4 Ethernet Communication
Two Diagrams
Diagram 1, Image
The diagram depicts the structure of an Ethernet frame. Listed below, from left to right, is the structure of a frame:
Structure of the Ethernet Frame
Preamble, 7 bytes Defines pattern of alternating 1 and 0 bits used to synchronize timing.
Start of Frame Delimiter (SFD), 1 byte. Marks the end of the timing information and start of the frame.
Destination MAC Address, 6 bytes. Contains the destination MAC address (receiver). The destination MAC address can be unicast, multicast, or broadcast.
Source MAC Address, 6 bytes. Contains the source MAC address (sender). This is the address of the Ethernet node that transmitted the data.
Length/Type, 2 bytes. Supports two different uses. A type value indicates which protocol will receive data. The length indicates the number of bytes of data that follows this field.
Encapsulated Data, 46 to 1500 bytes. The payload and sizing requirements stipulate between 64 to 1518 bytes for the entire Ethernet frame.
Frame Check Sequence (FCS), 4 bytes. Contains a four byte value that is created by the device that sends the frame and is recalculated by the destination device to check for damage to the frame.
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3.3.4 Ethernet Communication
Diagram 2, Activity
The diagram depicts an activity in which you must build a standard IEEE 802.3 Ethernet frame based on the source and destination device. The star topology has been configured with a switch at the center and five hosts attached. The source has the MAC address AA:AA:AA:AA:AA:AA and the destination host has the MAC address BB:BB:BB:BB:BB:BB. Place the fields below in the correct order:
One.Preamble
Two.DATA (Encapsulated Packet)
Three.Length/Type Field
Four.BB:BB:BB:BB:BB:BB
Five.AA:AA:AA:AA:AA:AA
Six.Frame Check Sequence (FCS)
Seven.Start of Frame Delimiter (SFD)
3.3.5 Hierarchical Design of Ethernet Networks
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Imagine how difficult communication would be if the only way to send a message to someone was to use the person's name. If there were no street addresses, cities, towns, or country boundaries, delivering a message to a specific person across the world would be nearly impossible.
On an Ethernet network, the host MAC address is similar to a person's name. A MAC address indicates the individual identity of a specific host, but it does not indicate where on the network the host is located. If all hosts on the Internet (over 400 million of them) were each identified by only their unique MAC address, imagine how difficult it would be to locate a single one.
Additionally, Ethernet technology generates a large amount of broadcast traffic in order for hosts to communicate. Broadcasts are sent to all hosts within a single network. Broadcasts consume bandwidth and slow network performance. What would happen if the millions of hosts attached to the Internet were all in one Ethernet network and were using broadcasts?
For these two reasons, large Ethernet networks consisting of many hosts are not efficient. It is better to divide larger networks into smaller, more manageable pieces. One way to divide larger networks is to use a hierarchical design model.
3.3.5 Hierarchical Design of Ethernet Networks
Diagram 1, Interactive
The diagram depicts an image of the world. It is primarily focused on North America. The image zooms in to Canada to indicate that there are specific boundaries to countries, just like there are boundaries within the addressing parameters of a network. This is otherwise known as hierarchical addressing. The image zooms again, this time it is focused on Nova Scotia, which is a province in Canada. The town of Halifax is shown next, and the end result shows a street and a specific location, namely a house address, which represents a host IP address on a network.
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In networking, hierarchical design is used to group devices into multiple networks that are organized in a layered approach. It consists of smaller, more manageable groups that allow local traffic to remain local. Only traffic that is destined for other networks is moved to a higher layer.
A hierarchical, layered design provides increased efficiency, optimization of function, and increased speed. It allows the network to scale as required because additional local networks can be added without impacting the performance of the existing ones.
The hierarchical design has three basic layers:
* Access Layer - to provide connections to hosts in a local Ethernet network.
* Distribution Layer - to interconnect the smaller local networks.
* Core Layer - a high-speed connection between distribution layer devices.
With this new hierarchical design, there is a need for a logical addressing scheme that can identify the location of a host. This is the Internet Protocol (IP) addressing scheme.
3.3.5 Hierarchical Design of Ethernet Networks
Diagram 2, Image
The diagram depicts a network that has been segmented into three hierarchical layers, the Access Layer, The Distribution Layer, and the Core Layer. Refer to the text body for details.
3.3.6 Logical Addressing
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A person's name usually does not change. A person's address on the other hand, relates to where they live and can change. On a host, the MAC address does not change; it is physically assigned to the host NIC and is known as the physical address. The physical address remains the same regardless of where the host is placed on the network.
The IP address is similar to the address of a person. It is known as a logical address because it is assigned logically based on where the host is located. The IP address, or network address, is assigned to each host by a network administrator based on the local network.
IP addresses contain two parts. One part identifies the local network. The network portion of the IP address will be the same for all hosts connected to the same local network. The second part of the IP address identifies the individual host. Within the same local network, the host portion of the IP address is unique to each host.
Both the physical MAC and logical IP addresses are required for a computer to communicate on a hierarchical network, just like both the name and address of a person are required to send a letter.
3.3.6 Logical Addressing
Diagram 1, Interactive
The diagram depicts two network clouds, both connected by a router. Directly connected to the router are hubs, one for each cloud, that act as concentrators for each network. Network 1 has a network address of 192.168.200.0, and network 2 has a network address of 192.168.1.0. Network 192.168.200.0 has four computers named H1 through H4 and have been assigned the addresses 192.168.200.1 through 192.168.200.4 respectively. Network 192.168.1.0 has four connected computers and they have been named H5 through H8 and have been assigned the addresses 192.168.1.1 through 192.168.1.4 respectively. H3 and H8 have been highlighted and an information box appears defining which parts of their corresponding IP address is dedicated to the network, and which part is dedicated to the host. The information that appears in the box is listed below:
H3 192.168.200 (Network portion), .3 (host portion)
H8 192.168.1 (Network portion), .4 (host portion)
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Lab Activity
Use the ipconfig /all command to display the IP address of your computer.
Click the lab icon to begin.
3.3.6 Logical Addressing
Diagram 2, Lab Activity
Link to Hands on Lab: Determine the IP Address of a Computer
3.3.7 Access and Distribution Layers and Devices
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IP traffic is managed based on the characteristics and devices associated with each of the three layers: Access, Distribution and Core. The IP address is used to determine if traffic should remain local or be moved up through the layers of the hierarchical network.
Access Layer
The Access Layer provides a connection point for end user devices to the network and allows multiple hosts to connect to other hosts through a network device, usually a hub or switch. Typically, all devices within a single Access Layer will have the same network portion of the IP address.
If a message is destined for a local host, based on the network portion of the IP address, the message remains local. If it is destined for a different network, it is passed up to the Distribution Layer. Hubs and switches provide the connection to the Distribution Layer devices, usually a router.
Distribution Layer
The Distribution Layer provides a connection point for separate networks and controls the flow of information between the networks. It typically contains more powerful switches than the Access Layer as well as routers for routing between networks. Distribution Layer devices control the type and amount of traffic that flows from the Access Layer to the Core Layer.
Core Layer
The Core Layer is a high-speed backbone layer with redundant (backup) connections. It is responsible for transporting large amounts of data between multiple end networks. Core Layer devices typically include very powerful, high-speed switches and routers. The main goal of the Core Layer is to transport data quickly.
Hubs, switches, and routers are discussed in more detail in the next two sections.
3.3.7 Access and Distribution Layer Devices
Two Diagrams
Diagram 1, Interactive
The diagram depicts a network that has been segmented into three layers: Access Layer, Distribution Layer, and Core Layer. Listed below are the devices supported at each layer:
Access Layer devices, IP phones, host computers, switches, and hubs
Distribution Layer devices, Routers
Core Layer devices, Switch route processors
Clicking a highlighted devices displays a photograph of the actual device.
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3.3.7 Access and Distribution Layer Devices
Diagram 2, Activity
The diagram depicts an activity in which you must select the addresses that are needed, the devices involved, and the layer on which the task occurs for each scenario.
Choices for each scenario:
Addresses: MAC, IP
Devices: Hub/Switch, Router
Layers: Access, Distribution, Core
Scenarios
One. Josh shares a file with another user on the network.
Two. Timar downloads a file from a server located in another country.
Three. Natalie sends an email from her email account at school to a student at a different school.
Four. Rhonda connects to the school network in order to download a file for her term report. The server is located on a different local network than her computer.
3.4 Building the Access Layer of an Ethernet Network
3.4.1 Access Layer
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The Access Layer is the most basic level of the network. It is the part of the network in which people gain access to other hosts and to shared files and printers. The Access Layer is composed of host devices, as well as the first line of networking devices to which they are attached.
Networking devices enable us to connect many hosts with each other and also provide those hosts access to services offered over the network. Unlike the simple network consisting of two hosts connected by a single cable, in the Access Layer, each host is connected to a networking device. This type of connectivity is shown in the graphic.
Within an Ethernet network, each host is able to connect directly to an Access Layer networking device using a point-to-point cable. These cables are manufactured to meet specific Ethernet standards. Each cable is plugged into a host NIC and then into a port on the networking device. There are several types of networking devices that can be used to connect hosts at the Access Layer, including Ethernet hubs and switches.
3.4.1 Access Layer
Single Diagram
Diagram 1, Image
The diagram depicts a network, which has been split into three layers: Access Layer, Distribution Layer, and Core Layer. The focus is on the Access Layer, which includes all host computers, switches, hubs, and IP phones.
3.4.2 Function of Hubs
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A hub is one type of networking device that is installed at the Access Layer of an Ethernet network. Hubs contain multiple ports that are used to connect hosts to the network. Hubs are simple devices that do not have the necessary electronics to decode the messages sent between hosts on the network. Hubs cannot determine which host should get any particular message. A hub simply accepts electronic signals from one port and regenerates (or repeats) the same message out all of the other ports.
Remember that the NIC on a host accepts messages only addressed to the correct MAC address. Hosts ignore messages that are not addressed to them. Only the host specified in the destination address of the message processes the message and responds to the sender.
All of the ports on the Ethernet hub connect to the same channel to send and receive messages. Because all hosts must share the bandwidth available on that channel, a hub is referred to as a shared-bandwidth device.
3.4.2 Function of Hubs
Three Diagrams
Diagram 1, Interactive
The diagram depicts the function of a hub. The source sends a packet to the destination, the hub receives the packet, and sends it to all other ports, except the source.
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Only one message can be sent through an Ethernet hub at a time. It is possible for two or more hosts connected to a hub to attempt to send a message at the same time. If this happens, the electronic signals that make up the messages collide with each other at the hub.
A collision causes the messages to become garbled and unreadable by the hosts. A hub does not decode the messages; therefore it does not detect that the message is garbled and repeats it out all the ports. The area of the network where a host can receive a garbled message resulting from a collision is known as a collision domain.
Inside a collision domain, when a host receives a garbled message, it detects that a collision has occurred. Each sending host waits a short amount of time and then attempts to send, or retransmit, the message again. As the number of hosts connected to the hub increases, so does the chance of collisions. More collisions cause more retransmissions. Excessive retransmissions can clog up the network and slow down network traffic. For this reason, it is necessary to limit the size of a collision domain.
3.4.2 Function of Hubs
Diagram 2, Interactive
The diagram depicts a hub with hosts attached to form a collision domain.
In this collision domain, all hosts will receive the garbled message when a collision occurs.
The diagram depicts a collision. Two sources send a packet to a destination. The hub receives both packets at the same time. The hub sends a garbled message to all devices.
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3.4.2 Function of Hubs
The diagram depicts an activity in which you must answer the questions for each scenario. Two hubs that are connected, each with four PC's attached.
Hub A has Hosts H1, H2, H3 and H4 connected.
Hub B has Hosts H5, H6, H7 and H8 connected.
3.4.3 Function of Switches
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An Ethernet switch is a device that is used at the Access Layer. Like a hub, a switch connects multiple hosts to the network. Unlike a hub, a switch can forward a message to a specific host. When a host sends a message to another host on the switch, the switch accepts and decodes the frames to read the physical (MAC) address portion of the message.
A table on the switch, called a MAC address table, contains a list of all of the active ports and the host MAC addresses that are attached to them. When a message is sent between hosts, the switch checks to see if the destination MAC address is in the table. If it is, the switch builds a temporary connection, called a circuit, between the source and destination ports. This new circuit provides a dedicated channel over which the two hosts can communicate. Other hosts attached to the switch do not share bandwidth on this channel and do not receive messages that are not addressed to them. A new circuit is built for every new conversation between hosts. These separate circuits allow many conversations to take place at the same time, without collisions occurring.
3.4.3 Function of Switches
Four Diagrams
Diagram 1, Interactive
The diagram depicts the function of a switch. The source sends a packet to the destination. The switch receives a packet and checks the MAC table for a port to which the destination is connected. The packet is sent to the destination port.
The diagram depicts a MAC table, which includes the fields Port Number and MAC Address of device connected.
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What happens when the switch receives a frame addressed to a new host that is not yet in the MAC address table? If the destination MAC address is not in the table, the switch does not have the necessary information to create an individual circuit. When the switch cannot determine where the destination host is located, it uses a process called flooding to forward the message out to all attached hosts. Each host compares the destination MAC address in the message to its own MAC address, but only the host with the correct destination address processes the message and responds to the sender.
How does the MAC address of a new host get into the MAC address table? A switch builds the MAC address table by examining the source MAC address of each frame that is sent between hosts. When a new host sends a message or responds to a flooded message, the switch immediately learns its MAC address and the port to which it is connected. The table is dynamically updated each time a new source MAC address is read by the switch. In this way, a switch quickly learns the MAC addresses of all attached hosts.
3.4.3 Function of Switches
Diagram 2, Interactive
The diagram depicts the function of a switch. The source sends a packet to a destination. The switch receives the packet and checks the MAC table for a port to which the destination is connected. If the MAC address is not in the table, the switch sends the packet to all ports, except the source. If the MAC address is in the table, the switch sends the packet only to the destination.
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Sometimes, it is necessary to connect another networking device, like a hub, to a switch port. This is done to increase the number of hosts that can be connected to the network. When a hub is connected to a switch port, the switch associates the MAC addresses of all hosts connected to that hub with the single port on the switch. Occasionally, one host on the attached hub sends a message to another host attached to the same hub. In this case, the switch receives the frame and checks the table to see where the destination host is located. If both the source and destination hosts are located on the same port, the switch discards the message.
When a hub is connected to a switch port, collisions can occur on the hub. The hub forwards to all ports the damaged messages resulting from a collision. The switch receives the garbled message, but, unlike a hub, a switch does not forward the damaged messages caused by collisions. As a result, every switch port creates a separate collision domain. This is a good thing. The fewer hosts contained in a collision domain, the less likely it is that a collision will occur.
3.4.3 Function of Switches
Diagram 3, Interactive
The diagram depicts how a collision is treated using switches.
There are two connected switches, Switch 1 and Switch 2. Switch 1 is connected to a hub, which has eight attached PC's labeled H1 through H8.
Switch 2 has eight attached PC's, also labeled H1 through H8.
Scenarios
One.
Two hosts on the hub that are attached to Switch 1 send a packet at the same time, causing a collision.
The hub on Switch 1 broadcasts the garbled packet to all hosts, including Switch 1.
Switch 1 discards the packet and does not forward it to Switch 2.
Two.
A host on the Switch 1 hub sends a packet to a host on Switch 2.
The hub on Switch1 broadcasts the packet to all ports, except the source.
Switch 1 sends packet to Switch 2.
Switch 2 sends packet to the destination host on the hub.
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3.4.3 Function of Switches
The diagram depicts an activity in which you must answer the questions for each of the scenarios. There are two switches, labeled Switch 1 and Switch 2. There is one hub, labeled Hub 1.
Switch 1 is connected to Switch 2.
Switch 1 is also connected to Hub 1.
Hub 1 has four PCs connected, labeled H1 through H4.
Switch 1 has four PCs connected, labeled H5 through H8.
Switch 2 has four PCs connected, labeled H9 through H12.
Scenarios
One.What occurs if H9 and H12 send a message across Switch 2 at the same time?
The two frames will collide and the switch will forward a garbled massage to all hosts on the network.
The two frames will collide and the switch will forward a garbled message to the source and intended destination hosts only.
The two frames will be forwarded to the correct destination device without a collision occurring.
Two hosts cannot send information across the switch at the same time because the hosts must wait for a request for data frame from the switch.
Two.If H9 sends a message to H6, and the destination MAC address is in the MAC table for both Switch 1 and Switch 2, which host devices will receive the message?
only H6
all hosts connected to Switch 1
all hosts connected to Hub 1 and hosts connected to Switch 1
all hosts on the network
Three.In this network, how many collision domains exist?
There is one collision domain.
There are two collision domains.
There are three collision domains.
There are 10 collision domains.
There are 12 collision domains.
Four.If H8 sends a message to H1, and the destination MAC address is in the switch MAC table, which host devices will receive the message?
only H1
all hosts connected to Hub 1
all hosts connected to Switch 1
all hosts connected to Hub 1 and hosts connected to Switch 1
all hosts on the network
3.4.4 Broadcast Messaging
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When hosts are connected using either a hub or a switch, a single local network is created. Within the local network it is often necessary for one host to be able to send messages to all the other hosts at the same time. This can be done using a message known as a broadcast. Broadcasts are useful when a host needs to find information without knowing exactly what other host can supply it or when a host wants to provide information to all other hosts in the same network in a timely manner.
A message can only contain one destination MAC address. So, how is it possible for a host to contact every other host on the local network without sending out a separate message to each individual MAC?
To solve this problem, broadcast messages are sent to a unique MAC address that is recognized by all hosts. The broadcast MAC address is actually a 48-bit address made up of all ones. Because of their length, MAC addresses are usually represented in hexadecimal notation. The broadcast MAC address in hexadecimal notation is FFFF.FFFF.FFFF. Each F in the hexadecimal notation represents four ones in the binary address.
3.4.4 Broadcast Messaging
Two Diagrams
Diagram 1, Animation
The diagram depicts a message broadcast. The source sends a message to every other node on the network.
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When a host receives a message addressed to the broadcast address, it accepts and processes the message as though the message was addressed directly to it. When a host sends a broadcast message, hubs and switches forward the message to every connected host within the same local network. For this reason, a local network is also referred to as a broadcast domain.
If too many hosts are connected to the same broadcast domain, broadcast traffic can become excessive. The number of hosts and the amount of network traffic that can be supported on the local network is limited by the capabilities of the hubs and switches used to connect them. As the network grows and more hosts are added, network traffic, including broadcast traffic, increases. It is often necessary to divide one local network, or broadcast domain, into multiple networks to improve performance.
3.4.4 Broadcast Messaging
Diagram 2, Image
The diagram depicts three sections of a company: Sales, Production, and Marketing. Each of the three sections is a separate broadcast domain.
3.4.5 Switch Behavior
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3.4.5 Switch Behavior
Single Diagram
Diagram 1, Activity
The diagram depicts an activity in which you must answer the question for each scenario.
The diagram depicts a 12-port switch with the following devices attached to the given ports:
FA 1 - 0A
FA 3 - 0B
FA 5 - 0C
FA 7 - 0D
FA 9 - hub with 0E, 0F attached
For each practice problem, a sample frame is generated with a source and destination address shown. The MAC table is also populated with various entries for the practice problem. Based on the source and destination address in the frame and the addresses learned in the switch MAC table, select each port to which the frame will be forwarded for Question 1. Select which statements are true based on the scenario for Question 2.
Scenarios
One. Where will the switch forward the frame?
The choices are FA 1 through FA 12.
Two. When the switch forwards the frame, which of the following statements are true?
Switch adds the source MAC address to the MAC table.
Frame is a broadcast frame and will be forwarded to all ports.
Frame is a unicast frame and will be sent to a specific port only.
Frame is a unicast frame and will be flooded to all ports.
Frame is a unicast frame but it will be dropped at the switch.
3.4.6 MAC and IP
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On a local Ethernet network, a NIC only accepts a frame if the destination address is either the broadcast MAC address, or else corresponds to the MAC address of the NIC.
Most network applications, however, rely on the logical destination IP address to identify the location of the servers and clients.
What if a sending host only has the logical IP address of the destination host? How does the sending host determine what destination MAC address to place within the frame?
The sending host can use an IP protocol called address resolution protocol (ARP) to discover the MAC address of any host on the same local network.
3.4.6 MAC and IP
Single Diagram
Diagram 1, Image
The diagram depicts a switch with four PC's attached, H1 through H4.
H1 - 192.168.1.5
H2 - 192.168.1.6
H3 - 192.168.1.7
H4 - 192.168.1.8
There are speech bubbles in the diagram. H1 says, I need to send information to 192.168.1.7, but I only have the IP address. I do not know which device has that IP.The PC will need to use Address Resolution Protocol (ARP) to discover the MAC address of the host with IP address 192.168.1.7, in order to communicate with it.
3.4.7 Address Resolution Protocol (ARP)
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ARP uses a three step process to discover and store the MAC address of a host on the local network when only the IP address of the host is known.
1. The sending host creates and sends a frame addressed to a broadcast MAC address. Contained in the frame is a message with the IP address of the intended destination host.
2. Each host on the network receives the broadcast frame and compares the IP address inside the message with its configured IP address. The host with the matching IP address sends its MAC address back to the original sending host.
3. The sending host receives the message and stores the MAC address and IP address information in a table called an ARP table.
Once the sending host has the MAC address of the destination host in its ARP table, it can send frames directly to the destination without doing an ARP request.
3.4.7 Address Resolution Protocol (ARP)
Single Diagram
Diagram 1, Animation
The animation demonstrates the use of ARP to find the MAC address of a destination host, when an IP address is known. Example is from 3.4.6. The process is explained within the body text.
3.5 Building the Distribution Layer of Network
3.5.1 Distribution Layer
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As networks grow, it is often necessary to divide one local network into multiple Access Layer networks. There are many ways to divide networks based on different criteria, including:
* Physical location
* Logical function
* Security requirements
* Application requirements
The Distribution Layer connects these independent local networks and controls the traffic flowing between them. It is responsible for ensuring that traffic between hosts on the local network stays local. Only traffic that is destined for other networks is passed on. The Distribution Layer can also filter incoming and outgoing traffic for security and traffic management.
Networking devices that make up the Distribution Layer are designed to interconnect networks, not individual hosts. Individual hosts are connected to the network via Access Layer devices, such as hubs and switches. The Access Layer devices are connected to each other via the Distribution Layer device, such as routers.
3.5.1 Distribution Layer
Single Diagram
Diagram 1, Interactive
The diagram depicts four boxes, each labeled with following headings: Broadcast Containment, Security, Locations, and Logical Grouping. More information is given below.
Broadcast Containment
Routers in the Distribution Layer can limit broadcasts to the local network where they need to be heard. Although broadcasts are necessary, too many hosts connected on the same local network can generate excessive broadcast traffic and slow down the network.
Security
Routers in the Distribution Layer can separate and protect certain groups of computers where confidential information resides. Routers can also hide the addresses of internal computers from the outside world to help prevent attacks and control who can get into or out of the local network.
Locations
Routers in the Distribution Layer can be used to interconnect local networks at various locations of an organization that are geographically separated.
Logical Grouping
Routers in the Distribution Layer can be used to logically group users, such as departments within a company, who have common needs or for access to resources.
3.5.2 Function of Routers
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A router is a networking device that connects a local network to other local networks. At the Distribution Layer of the network, routers direct traffic and perform other functions critical to efficient network operation. Routers, like switches, are able to decode and read the messages that are sent to them. Unlike switches, which only decode (unencapsulate) the frame containing the MAC address information, routers decode the packet that is encapsulated within the frame.
The packet format contains the IP addresses of the destination and source hosts, as well as the message data being sent between them. The router reads the network portion of the destination IP address and uses it to find which one of the attached networks is the best way to forward the message to the destination.
Anytime the network portion of the IP addresses of the source and destination hosts do not match, a router must be used to forward the message. If a host located on network 1.1.1.0 needs to send a message to a host on network 5.5.5.0, the host will forward the message to the router. The router receives the message and unencapsulates it to read the destination IP address. It then determines where to forward the message. It re-encapsulates the packet back into a frame, and forwards the frame on to its destination.
3.5.2 Function of Routers
Three Diagrams
Diagram 1, Animation
The diagram depicts an IP packet encapsulated in an Ethernet Frame.
The Ethernet frame consists of the destination MAC address (moving left to right within the frame), followed by the source MAC address. The destination and source MAC address sections of the frame are read by Layer 2 devices, such as a switch or bridge.
The source and destination MAC addresses are as follows:
Source MAC address AA:AA:AA:AA:AA:AA.
Destination MAC BB:BB:BB:BB:BB:BB
The next fields in the frame are the destination IP and the source IP addresses. Depending on the subnet mask, some bits belong to the network portion and some belong to the host portion.
For example, with the address 192.168.1.5, the first three octets (192.168.1) belong to the network, and .5 belongs to the host.
In addition to the source and destination IP address, the IP packet contains the user data. The data is also known as the payload. The last part of the Ethernet frame is the trailer. The trailer finishes the encapsulation of the frame.
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Lab Activity
Assign different IP addresses on a peer-to-peer network, and view the effects on network communication.
Click the lab icon to begin.
3.5.2 Function of Routers
Diagram 2, Lab Activity
Link to Hands-on Lab: IP Addresses and Network Communication
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How does the router determine what path to send the message to get to the destination network?
Each port, or interface, on a router connects to a different local network. Every router contains a table of all locally-connected networks and the interfaces that connect to them. These routing tables can also contain information about the routes, or paths, that the router uses to reach other remote networks that are not locally attached.
When a router receives a frame, it decodes the frame to get to the packet containing the destination IP address. It matches the address of the destination to all of the networks that are contained in the routing table. If the destination network address is in the table, the router encapsulates the packet in a new frame in order to send it out. It forwards the new frame out of the interface associated with the path, to the destination network. The process of forwarding the packets toward their destination network is called routing.
Router interfaces do not forward messages that are addressed to the local network broadcast IP address. As a result, local network broadcasts are not sent across routers to other local networks.
3.5.2 Function of Routers
Diagram 3, Animation
The diagram depicts a network with a central router and three switches attached. Each switch has a number of hosts attached. Connected to the first switch are hosts H1 through H3. This switch connects to the router FA0/0 interface. The routers FA0/2 connects to another switch with host H4 attached. Another connection from the router connects to a switch with hosts H5 and H6 attached. The IP addresses are as follows:
H1 10.0.0.1
H2 10.0.0.2
H3 10.0.0.3
H4 192.168.1.2
H5 172.16.0.2
H6 172.16.0.1
H1 sends a packet out onto the network for the H4 client with the address 192.168.1.2. First, the message traverses the network based on forwarding decisions made by the switch. The switch examines the MAC address table to see if the entry is on the local network. If the MAC is not found, the packet is then forwarded to the default gateway. The router examines the routing table to see if the IP address entry exists, and whether there is a path to the destination network in the routing table. Once the path has been determined, the router sends the packet out of the appropriate interface so the message reaches the destination IP 192.168.1.2. If host H1 sends a broadcast message, all hosts connected to the switch on the 10.0.0.0 network receives the message. The router connected to this switch also receives the message but does not forward the broadcast. The message is discarded at the router.
3.5.3 Default Gateway
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The method that a host uses to send messages to a destination on a remote network differs from the way a host sends messages on the same local network. When a host needs to send a message to another host located on the same network, it will forward the message directly. A host will use ARP to discover the MAC address of the destination host. It includes the destination IP address within the packet and encapsulates the packet into a frame containing the MAC address of the destination and forwards it out.
On the other hand, when a host needs to send a message to a remote network, it must use the router. The host includes the IP address of the destination host within the packet just like before. However, when it encapsulates the packet into a frame, it uses the MAC address of the router as the destination for the frame. In this way, the router will receive and accept the frame based on the MAC address.
How does the source host determine the MAC address of the router? A host is given the IP address of the router through the default gateway address configured in its TCP/IP settings. The default gateway address is the address of the router interface connected to the same local network as the source host. All hosts on the local network use the default gateway address to send messages to the router. Once the host knows the default gateway IP address, it can use ARP to determine the MAC address. The MAC address of the router is then placed in the frame, destined for another network.
It is important that the correct default gateway be configured on each host on the local network. If no default gateway is configured in the host TCP/IP settings, or if the wrong default gateway is specified, messages addressed to hosts on remote networks cannot be delivered.
3.5.3 Default Gateway
Two Diagrams
Diagram 1, Interactive
The diagram depicts three hosts, H1, H2, and H3, connected to a switch. The switch is connected to a router. The router acts as the default gateway to the adjoining network segment. The default gateway IP address is 192.168.1.254. The default gateway is the near-side interface of the boundary router. Clicking on each host displays its IP address (192.168.1.x), subnet mask (255.255.255.0), and the address of the default gateway (192.168.1.254).
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3.5.3 Default Gateway
Diagram 2, Activity
The diagram depicts an activity in which you must enter the correct default gateway IP address for each host so that packets may traverse the network.
The router at the center of this network has three Fast Ethernet ports. Host H1 is connected to a switch, and the switch in turn is connected to the router on IP address 192.168.1.1. H2 is connected to a switch, and the switch in turn is connected to the router, IP address 10.0.0.1. H3 is connected to a switch, and the switch in turn is connected to the router, IP address 172.16.0.50. Clicking each host displays the TCP/IP Properties window where the default gateway address for H1, H2, and H3 may be entered.
3.5.4 Tables Maintained by Routers
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Routers move information between local and remote networks. To do this, routers must use both ARP and routing tables to store information. Routing tables are not concerned with the addresses of individual hosts. Routing tables contain the addresses of networks and the best path to reach those networks. Entries can be made to the routing table in two ways: dynamically updated by information received from other routers in the network, or manually entered by a network administrator. Routers use the routing tables to determine which interface to use to forward a message to its intended destination.
If the router cannot determine where to forward a message, it will drop it. Network administrators configure a routing table with a default route to keep a packet from being dropped because the path to the destination network is not in the routing table. A default route is the interface through which the router forwards a packet containing an unknown destination IP network address. This default route usually connects to another router that can forward the packet towards its final destination network.
3.5.4 Tables Maintained by Routers
Three Diagrams
Diagram 1, Interactive
The diagram depicts a network with one router, two switches, and four hosts per switch. The hosts are labeled H1 through H8. The routers Fast Ethernet FA0/0 is connected to Switch 1. The IP addressing scheme for the four clients connected to the switch are 10.1.21.1 through 10.1.21.4. The routers second Fast Ethernet FA0/1 is connected to Switch 2. The IP addressing scheme for the four clients H5 through H8 is 172.16.1.3 through 172.16.1.6, respectively. Two tables are kept and updated by the router: the Address Resolution Protocol (ARP) table and the Routing table. The entries into these tables are listed below:
ARP TABLE
AddressHardware AddressInterface
10.1.21.1 0002.a5ec.c7f9 Fast Ethernet 0/0
10.1.21.2 0012.3fec.fb0d Fast Ethernet 0/0
10.1.21.3 0014.220e.dac5 Fast Ethernet 0/0
10.1.21.4 00c0.9f4b.8b76 Fast Ethernet 0/0
172.16.1.3 0ac3.a56c.d7f5 Fast Ethernet 0/1
172.16.1.4 0a2f.4fed.dd0d Fast Ethernet 0/1
172.16.1.5 0b03.3002.ea2d Fast Ethernet 0/1
172.16.1.6 0d00.a94b.8caa Fast Ethernet 0/1
ROUTING TABLE
TypeNetwork Port
C10.0.0.0/8 FastEthernet0/0
C172.16.0.0/8 FastEthernet0/1
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A router forwards a frame to one of two places: a directly connected network containing the actual destination host, or to another router on the path to reach the destination host. When a router encapsulates the frame to forward it out of an Ethernet interface, it must include a destination MAC address.
This is the MAC address of the actual destination host, if the destination host is part of a network locally connected to the router. If the router must forward the packet to another router, it will use the MAC address of the connected router. Routers obtain these MAC addresses from ARP tables.
Each router interface is part of the local network to which it is attached and maintains its own ARP table for that network. The ARP tables contain the MAC addresses and IP addresses of all of the individual hosts on that network.
3.5.4 Tables Maintained by Routers
Diagram 2, Animation
The diagram is a two-part animation. The diagram depicts three local networks joined to a router. The topology is as follows: H1 through H3 are connected to Switch 1, which in turn connects to the router. H4 through H6 are connected to Switch 2, which in turn connects to the router. H7 through H9 are connected to Switch 3, which in turn connects to the router. There are speech bubbles in the diagram, as follows:
The first part shows the step to send a packet from one host to another host on the local network.
LOCAL NETWORK
H1 says, I need to send a packet to IP address 192.168.1.3. That IP is in my local network.
The IP and MAC addresses are in my ARP table, I will forward it directly.
Note that the packet does not leave the local network.
The second part of the animation shows the steps to send a packet from a host on one local network to a host on a remote local network:
REMOTE NETWORK
H1 says, I need to send a packet to IP address 192.168.2.1 (H4). That IP is not in my local network. This packet must be sent to my default gateway for forwarding. I have the default gateways IP and MAC address in my ARP table.
Router 1 says, This host (H4) is on a network directly connected on one of my other interfaces. I will check my ARP table. There he is, now I can forward the packet.
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3.5.4 Tables Maintained by Routers
Diagram 3, Activity
The diagram depicts an activity in which you must determine how the router forwards a packet based on the source and destination IP address in the frame (encapsulated IP packet) and the information in the route table.
Route Table
The route table entries do not change and are as follows:
Type Network PortNext Hop Metric
C192.168.3.0/24 Ethernet 0/0--0/0
C172.16.1.0/24 Ethernet 0/1--0/0
C10.5.5.0/24 Ethernet 0/2--0/0
Frame
In the activity, random practice problems are generated with different source and destination IP addresses in the Frame.
An example of a practice scenario includes the following frame IP address information:
Destination IP: 192.168.3.5
Source IP: 10.5.5.8
Scenarios
One. What is the default gateway address used to forward this packet to the router?
192.168.3.1
172.16.1.1
10.5.5.1
Two. When the router receives this packet, to which interface will the router forward the packet?
Ethernet1/1
Ethernet1/2
Ethernet1/3
3.5.5 Local Area Network (LAN)
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The term Local Area Network (LAN) refers to a local network, or a group of interconnected local networks that are under the same administrative control. In the early days of networking, LANs were defined as small networks that existed in a single physical location. While LANs can be a single local network installed in a home or small office, the definition of LAN has evolved to include interconnected local networks consisting of many hundreds of hosts, installed in multiple buildings and locations.
The important thing to remember is that all of the local networks within a LAN are under one administrative control. Other common characteristics of LANs are that they typically use Ethernet or wireless protocols, and they support high data rates.
The term Intranet is often used to refer to a private LAN that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization.
3.5.5 Local-Area Network (LAN)
Two Diagrams
Diagram1, Interactive
The diagram depicts two networks, a network that has multiple local networks and a network that is a single local network. The topology for each of these networks is as follows:
Multiple Local Network
The router is at the center of this topology with three switches directly connected to the router. Switch 1 has three computers connected, H1 through H3, and a network address of 192.168.1.0. Switch 2 has three computers connected, H4 through H6, and a network address of 192.168.2.0. The final network has Switch 3 with three hosts connected, H7 through H9, and a network address of 192.168.3.0. The router acts as the joining point for the three networks.
Single Local Network
The single local network consists of three switches and nine hosts. The router has been removed. Switch 1 is directly connected to Switch 3. Switch 2 is also directly connected to Switch 3. Switch 1 has three computers connected, H1 through H3. Switch 2 has three computers connected, H4 through H6, and Switch 3 has three connected, H7 through H9. The network address assigned to this network is 192.168.1.0. All hosts share this network number.
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3.5.5 Local-Area Network (LAN)
Diagram 2, Activity
The diagram depicts an activity in which you must identify how many local networks are in the LAN in the diagram. The topology is as follows:
A router is at the center. Directly connected to the router are four switches. Connected to Switch 1 is another switch with four computers. Switch 1 also has three computers directly connected to it. Switch 2 has three computers directly connected to it. Switch 3 has two computers directly connected to it. Switch 4 has a hub and three computers directly connected to it. Directly connected to the hub are two more computers.
3.5.6 Adding Hosts to Local and Remote Networks
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Within a LAN, it is possible to place all hosts on a single local network or divide them up between multiple networks connected by a Distribution Layer. The answer depends on desired results. Placing all hosts on a single local network allows them to be seen by all other hosts. This is because there is one broadcast domain and hosts use ARP to find each other.
In a simple network design it may be beneficial to keep all hosts within a single local network. However, as networks grow in size, increased traffic will decrease network performance and speed. In this case, it may be beneficial to move some hosts onto a remote network.
Placing additional hosts on a remote network will decrease the impact of traffic demands. However, hosts on one network will not be able to communicate with hosts on the other without the use of routing. Routers increase the complexity of the network configuration and can introduce latency, or time delay, on packets sent from one local network to the other.
3.5.6 Adding Hosts to Local and Remote Networks
Single Diagram
Diagram 1, Interactive
The diagram depicts two network topologies: a LAN consisting of a single local network, and a LAN consisting of multiple local networks connected by a central router. The conditions and characteristics for each of these networks are as follows:
LAN with all hosts on a single local network
In the diagram of a LAN with all hosts on a single local network topology, two switches directly connected to each other. Each switch is connected to five clients. Switch 1 has clients H1 through H5, and Switch 2 has clients H6 through H10.
ADVANTAGES
Appropriate for simpler networks.
Less complexity and lower network cost.
Allows devices to be "seen" by other devices.
Faster data transfer because of more direct communication.
Ease of device access.
DISADVANTAGES
All hosts are in one broadcast domain which causes more traffic on the segment and may slow network performance.
LAN with hosts on different networks.
In the diagram of a LAN with hosts on different networks, a single router has its two Fast Ethernet ports directly connected to two Layer 2 switches. Switch 1 has three hosts, H4 through H6, and Switch 2 has three hosts, H10 through H12.
ADVANTAGES
Appropriate for larger, more complex networks.
Splits up broadcast domains and decreases traffic.
Can improve performance on each segment.
Makes the machines invisible to those on other local network segments.
Can provide increased security.
Can improve network organization.
DISADVANTAGES
Requires the use of routing (Distribution Layer).
Router can slow traffic between segments.
More complexity and expense (requires router).
3.5.7 Learn to Use Packet Tracer
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3.5.7 Learn to Use Packet Tracer
Two Diagrams
Diagram 1, Animated Simulation
The diagram is an animated simulation.
Packet Tracer Window
Packet Tracer is a graphical learning and simulation tool Cisco developed to help model and understand how networks function. It enables you to build network topologies and test them by sending packets between devices and observing the interactions of protocols in use.
The diagram depicts the Packet Tracer application window in Windows XP. The animation demonstrates the use of the main Packet Tracer user interface features.
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Packet Tracer Activity
Become familiar with the user interface of Packet Tracer. Model a simple network and observe network behavior. Create an Ethernet network using two hosts and a hub and observe ARP, broadcast and ping (ICMP) traffic.
Click the Packet Tracer icon to begin.
3.5.7 Learn to Use Packet Tracer
Diagram 2, Packet Tracer Activity
Link to Packet Tracer Activity: Learn to Use Packet Tracer
Note: Packet Tracer is available for download from the Cisco Systems Academy homepage. On the right side of the page, there is the TOOLS option, where Packet Tracer can be found. Packet Tracer is currently being re-authored for use by the vision impaired and will be available shortly.
3.6 Plan and Connect a Local Network
3.6.1 Plan and Document an Ethernet Network
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Most local networks are based on Ethernet technology. This technology is both fast and efficient when used in a properly designed and constructed network. The key to installing a good network is planning before the network is actually built.
A network plan starts with the gathering of information about how the network will be used. This information includes:
* The number and type of hosts to be connected to network
* The applications to be used
* Sharing and Internet connectivity requirements
* Security and privacy considerations
* Reliability and uptime expectations
* Connectivity requirements including, wired and wireless
3.6.1 Plan and Document an Ethernet Network
Two Diagrams
Diagram 1, Interactive
The diagram depicts a man sitting at a desk in front of computer planning the physical topology and logical addressing scheme for a network. Network planning is crucial to installing a good network.
A network plan starts with the gathering of information about how the network will be used, as follows:
Number and type of hosts to be connected to network.
Where are the end users located? What type of hardware are they using? Where are the servers, printers, and other devices located?
Applications to be used.
What type of applications are running on the network?
Data and devices to be shared Who requires access to which files and network resources, such as printers?
Bandwidth requirements (speed) What is an acceptable speed for the end users? Do all users require the same throughput? What affect will the applications have on the throughput?
Security and privacy considerations.
Is the data being moved on the network of a personal or sensitive nature? Could unauthorized access to this information cause harm to anyone?
Reliability and up time expectations.
How important is the network? Does it need to be available 100% of the time, (this is known as up time)? How much downtime can be tolerated?
Connectivity requirements, including wired and wireless Do any or all of the end users require wireless connectivity?
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There are many considerations that must be taken into account when planning for a network installation. The logical and physical topology maps of the network need to be designed and documented before the networking equipment is purchased and the hosts are connected. Some things to consider include:
Physical environment where the network will be installed:
* Temperature control: all devices have specific ranges of temperature and humidity requirements for proper operation
* Availability and placement of power outlets
Physical configuration of the network:
* Physical location of devices such as routers, switches, and hosts
* How all devices are interconnected
* Location and length of all cable runs
* Hardware configuration of end devices such as hosts and servers
Logical configuration of the network:
* Location and size of broadcast and collision domains
* IP addressing scheme
* Naming scheme
* Sharing configuration
* Permissions
3.6.1 Plan and Document an Ethernet Network
Diagram 2, Interactive
The diagram depicts a campus network with two types of topologies, Physical and Logical.
Physical Topology
The physical topology encompasses all the physical media and devices that may be found in a network. Included in the physical topology is the physical location of devices, such as routers, switches, and hosts, as well as how all devices are interconnected. Also pertinent to design is the location and length of all cable runs, and hardware configuration of end devices such as hosts and servers.
Logical Topology
The logical topology defines the addressing scheme used to name and address all machines on the network. Logical topology includes the IP addressing scheme, naming scheme, sharing configuration, permissions, and the location and size of broadcast and collision domains.
3.6.2 Prototypes
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Once the network requirements are documented, and the physical and logical topology maps created, the next step in the implementation process is to test the network design. One of the ways to test a network design is to create a working model, or prototype, of the network.
Prototyping is essential as networks grow in size and complexity. A prototype allows a network administrator to test whether or not the planned network will operate as expected, before money is spent on equipment and installation. Documentation should be maintained on all aspects of the prototyping process.
Various tools and techniques are available for network prototyping; this includes real equipment set up in a lab environment, modeling and simulation tools. Packet Tracer is one example of a simulation and modeling tool that can be used for prototyping.
3.6.2 Prototypes
Three Diagrams
Diagram 1, Image
The diagram depicts a screen shot from Packet Tracer, which is a simulation program used for physical and logical network topology configuration so that issues in planning can be quickly corrected before implementation of the network takes place. Tools and techniques are available for network prototyping, including a lab environment set up with real equipment, and various simulation and modeling tools. Packet Tracer is an example of a simulation and modeling tool that can be used for prototyping.
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3.6.2 Prototypes
Diagram 2, Animated Simulation
The diagram depicts Packet Tracer in use. A prototype network topology is being designed, captured as a flash movie. As the file plays, several network devices are added to the blank topology work area. The scenario that the network is being planned for is a web server and two computers linked to the Ethernet switch portion of a Linksys WRT300N wireless router and Access Point (AP). These network devices are as follows, a Linksys WRT300N Wireless Router and 3 computers. After the network devices are added, the links between the devices are configured in terms of the media being used. Each host is connected to the switch portion of the WRT300N so a wired FastEthernet link icon is selected and used to connect the devices. Now that the physical topology is complete, the logical topology needs to be configured. Each network device on the page is selected and an appropriate IP address, subnet mask and default gateway is configured.
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Packet Tracer Activity
Prototype a simple network consisting of two hosts and a switch.
Click the Packet Tracer icon to begin.
3.6.2 Prototypes
Diagram 3, Packet Tracer Activity
Link to Packet Tracer Activity: Prototyping a Network
The diagram depicts a launch window for Packet Tracer. Clicking the icon will start Packet Tracer and open the exercise associated with this online page.
Note: For further assistance with this exercise, please refer to the VI Packet Tracer program that will be available online.
3.6.3 Multi-function Device
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Most home and small business networks do not require high-volume devices used in large business environments; smaller scale devices may well be suitable. However, the same functionality of routing and switching is required. This need has led to the development of products that have the functionality of multiple network devices, such as a router with switching functionality and a wireless access point. For the purpose of this course, multi-function devices will be referred to as integrated routers. Integrated routers can range from small devices designed for home office and small business applications to more powerful devices that can support enterprise branch offices.
An integrated router is like having several different devices connected together. For example, the connection between the switch and the router still occurs, but it occurs internally. When a broadcast is received on a switch port, the integrated router forwards the broadcast to all ports including the internal router connection. The router portion of the integrated router stops the broadcasts from going any further.
There are low-cost multi-function devices available for home and small business networks that offer integrated routing, switching, wireless and security capabilities. An example of this type of integrated router is a Linksys wireless router. They are simple in design and do not typically have separate components. In the event of a failure, it is not possible to replace any single failed component. As such, they create a single point of failure, and are not optimized for any one function.
Another example of an integrated router is the Cisco integrated services router or ISR. The Cisco ISR product family offers a wide range of products, including those designed for small office and home office environments as well as those designed for larger networks. Many of the ISRs offer modularity and have separate components for each function, such as a switch component and a router component. This enables individual components to be added, replaced and upgraded as necessary.
3.6.3 MultiFunction Devices
Single Diagram
Diagram 1, Animation
The diagram depicts a Linksys WRT300N Wireless Router AP. This multifunction device contains three network devices that, when combined into one unit reduces costs and raises the level of functionality. It combines a switch, router, and access point (AP) into the one unit. Multifunction devices are useful because they combine the functions of many devices into a singular device.
3.6.4 Connecting the Linksys Router
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3.6.4 Connecting the Linksys Router
The diagram depicts the front and back view of the Linksys WRT300N Wireless Router. The views and the indicators are as follows:
Front View
Light Emitting Diodes (L E D) Descriptions
Power L E D - Indicates the presence of power to the device. It is a solid green L E D.
W LAN L E D Indicates status of wireless connections.
Ethernet L E D's (1-4) Indicates status of the wired Ethernet connections.
Internet L E D Indicates status of the Internet connection.
Color Status of L E D's:
Green indicates a connection has been made with an end device.
Red or Yellow usually indicates that there is problem with an end device.
Blinking indicates activity on the port.
Rear View
Internet Port:
A single port that is connected to the router portion of the multifunction device. This is used to connect the device to another network, such as the Internet. The router portion of a multifunction device maintains routing tables. There is an internal connection from the routing portion of the multifunction device to the switch portion. The Internet port is connected to a different network than the Ethernet.
Ethernet Ports:
Multiple ports that are connected to the internal switch portion of the multifunction device. These are usually labeled, Ethernet. All devices connected to the switch ports are on the same local network. There is also an internal connection from the switch port to the router port (Internet port).
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All devices connected to the switch ports should be in the same broadcast domain. This means that all devices must have an IP address from the same network. Any device that has a different network portion within the IP address will not be able to communicate.
Additionally, Microsoft Windows makes use of computer names to identify other devices on the network. It is important to use these names as well as all IP address information in the planning and documentation to assist in future troubleshooting.
To display the current IP configuration in Microsoft Windows, use the command ipconfig. More detailed information, including host name, is available with the ipconfig /all. Document all information from the connection and configuration process.
Once hosts are communicating across the network, it is important to document network performance. This is known as determining the baseline for the network, and is used as an indication of normal operations. When comparing future network performance with the baseline, it can indicate if possible issues exist.
3.6.4 Connecting the Linksys Router
Diagram 2, Image
The diagram depicts the TCP/IP Properties window found in the Windows XP operating system.
The configuration of specific parameters are made using this window. All devices connected to the switch ports should be in the same broadcast domain. This means that all devices must have an IP address from the same network. Any device that has a different network portion within the IP address will not be able to communicate.
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Lab Activity
Build and document a simple pre-planned network using a networking device and two hosts and verify IP configuration.
Click the lab icon to begin.
3.6.4 Connecting the Linksys Router
Diagram 3, Lab Activity
Link to Hands-on Lab: Connect and Configure Hosts
Note: The document that pertains to this lab is available for download from the CAVI website.
3.6.5 Sharing Resources
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One of the most common purposes of networking is to share resources such as files and printers. Windows XP enables remote users to access a local machine and its resources through Sharing. It is important to consider security issues, and to assign specific permissions to shared resources.
By default, Windows XP uses a process known as Simple File Sharing. With Simple File Sharing, specific users and groups cannot be prevented from accessing shared files.
Simple File Sharing can be disabled so that more specific security access levels can be assigned. When this is done, the following permissions are available to assign to resources:
* Full Control
* Modify
* Read & Execute
* List Folder Contents
* Read
* Write
When a user accesses a file on a remote device, Windows Explorer allows the user to map a drive to a remote folder or resource. This maps a specific drive letter, for example M:, to the remote resource. This enables the user to treat the resource as though it was locally connected.
3.6.5 Sharing Resources
Three Diagrams
Diagram 1, Image
The diagram depicts a hand with an open folder in it. The open folder indicates that the person holding the folder wants to share information or resources with those around them.
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3.6.5 Sharing Resources
Diagram 2, Animated Simulation
The diagram depicts the Windows XP operating system desktop. The start menu has been selected. The flash file, when played, shows the steps taken to create a Share Folder on the local machine. A text file is then authored and copied to the Share Folder so that it can be accessed. It is then modified on the other network computer. This is done to show that the share folder can be seen and manipulated from another machine on the network.
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Lab Activity
Map a network drive and share a file.
Click the lab icon to begin.
3.6.5 Sharing Resources
Diagram 3, Lab Activity
Link to Hands-on Lab: Sharing Resources
Note: The document that pertains to this lab is available for download from the CAVI website.
3.7 Chapter Summary
3.7.1 Summary
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3.7.1 Summary
Eight Diagrams, Slider Graphic
Diagram 1, Image
The diagram depicts voice, video, and data converged networks.
Diagram 1 text
This chapter discussed basic concepts and benefits of networking, and the characteristics of local Ethernet networks.
Information networks can carry voice, video, and data.
Information networks consist of peripherals, hosts, network devices, and media.
Topology diagrams used to depict both logical and physical network design.
Hosts can play the role of client, server, or both.
Diagram 2, Image
The diagram depicts protocol characteristics.
Diagram 2 text
All communication has a source, a destination, and a channel.
Computer communications operate under special rules, called protocols.
Protocols define the characteristics of a message including: encoding, formatting, encapsulation, size, timing, and patterns.
Diagram 3, Image
The diagram depicts the network protocol evolution.
Diagram 3 text
To communicate on a local network requires the computers share a common protocol.
The most common protocol used on local wired networks is industry standard Ethernet.
Each local host in an Ethernet network is identified by a physical MAC address, which is pre configured into a hosts NIC.
Proprietary Vendor Protocols (1970's) IBM, NCR, Xerox, D E C, HP
Limited Number of standards (1980's and 1990's) Ethernet (IEEE 8 0 2 dot 3), ARCnet (IEEE 8 0 2 dot 4), Token Ring (IEEE 8 0 2 dot 5)
And the winner is Ethernet (2000)
Diagram 4, Image
The diagram depicts hierarchical network design.
Diagram 4 text
It is common to divide larger networks into smaller, more manageable ones using a layered hierarchical design, which can include the following layers:
Access
Distribution
Core
Each of these layers has a primary function and associated devices.
Diagram 5, Image
The diagram depicts routed network using logical and physical addressing.
Diagram 5 text
Logical IP addresses are used to identify the location of a host within this hierarchical design.
To deliver a packet to an individual host requires both a physical MAC address and a logical IP address.
ARP is used to resolve an IP address to a MAC address for local delivery.
Diagram 6, Image
The diagram depicts hierarchical network design.
Diagram 6 text
Access Layer
The Access Layer is the first point of entry into the network for all hosts.
Hosts are usually directly connected using Ethernet cables to an Access Layer device, such as a hub or switch.
MAC address and IP addresses are used on the local network at the Access Layer.
Distribution Layer
The Distribution Layer connects independent local networks and controls traffic between them.
Individual hosts are not usually connected directly to the Distribution Layer devices.
Routers are the main networking device within the Distribution Layer and use IP addresses to move packets between networks.
Diagram 7, Image
The diagram depicts network planning.
Diagram 7 text
A network plan starts with the gathering of information about how the network will be used. This information includes the following parameters:
The number and type of hosts to be connected to the network.
The applications to be used.
Sharing and Internet connectivity requirements.
Security and privacy considerations.
Reliability and up time expectations.
Connectivity requirements, including wired and wireless.
Diagram 8, Image
The diagram depicts a WRT300N wireless router multifunction device.
Diagram 8 text
Cisco ISR's, and other multifunction networking devices connect home and small business networks in order for multiple hosts to share resources and to connect to the Internet.
A home networking device is a simplified low cost device commonly used in small networks.
These devices typically provide the functionality of a switch, router, and wireless access point in one device.
3.8 Chapter Quiz
3.8.1 Quiz
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Take the chapter quiz to check your knowledge.
Click the quiz icon to begin.
3.8.1 Quiz
12 Questions
1.The diagram depicts an IP telephone connected to a switch. Also connected to the switch are two computers, directly connected to one of the computers is a standalone printer.
Refer to the description above. What two types of devices are the printer and the IP phone? (Choose two.)
The IP phone is a peripheral.
The IP phone is a host.
The IP phone is a network device.
The printer is a peripheral.
The printer is a host.
The printer is a network device.
2. Determine if the characteristics listed are an advantage or disadvantage of a peer to peer network.
Advantages
Disadvantages
Provide minimal security.
No centralized administration.
Inexpensive.
Potential impact on performance.
Easy to set up.
No special hardware.
3.List whether the statements below are related to a Logical Topology Map or a Physical Topology Map.
Logical Topology Map
Physical Topology Map
Shows wiring installations.
Shows location of networking devices.
Shows host names and host addresses.
Shows group information and applications used.
Shows location of each host and how they connect to the network.
Shows location of broadcast and collision domains.
4. Match the situation with the correct type of message that would be used.
Unicast
Multicast
Broadcast
A host device sends a hello message to all computers on the network.
A host device sends an email to another host device.
A host device joins a group to receive video conferencing.
A host device requests a web page and displays the results.
A host device sends out an ARP request looking for the MAC address for a specific IP address.
A router forwards its routing table to a specific group of routers on the network.
5. Which two statements accurately describe a router ARP table and routing table? (Choose two)
The ARP table contains information about individual devices, not networks.
The ARP table contains information about networks, not individual devices.
The ARP table contains information about networks and individual devices.
The routing table contains information about individual devices, not networks.
The routing table contains information about networks, not individual devices.
The routing table contains information about networks and individual devices.
6.What process can a user perform on the host so that a folder on a remote server is treated as if it were a local resource?
mapping a drive
sharing a drive
enabling a remote user
setting share permissions
7.Determine if the tasks performed would be considered the role of a client, server, or both. Match the task with the role of Client, Server or Both Client and Server.
Client
Server
Client and Server
Share files with another device.
Download a music file from a website.
Play a video game with a friend across a network.
Participate in a videoconference with another computer.
Connect to an e learning site to learn networking
Store e-mail and deliver it upon request.
8.The diagram depicts two switches named Switch A and Switch B directly connected to each other. H1 and H2 are directly connected to switch A and H3 and H4 are directly connected to switch B.
Refer to the description above. If H1 on Switch A needs to forward to H3 on Switch B, which MAC address is used as the destination MAC within the frame?
MAC address of H1
MAC address of Switch A
MAC address of Switch B
MAC address of H3
9.The diagram depicts two network segments, LAN A and LAN B, directly connect to Router1 via Switch1 and Switch2. Computer1 is located on Switch1 and Computer10 is located on Switch2.
Refer to the description above. When Router1 receives a message with a source address of Computer1 on LAN A and a destination address of Computer10 on LAN B, what will be the action of Router 1?
The router checks its ARP table to determine where to forward the packet to reach Computer10.
The router checks it ARP table to determine the appropriate IP address of Computer10.
The router checks its routing table to determine where to forward the packet to reach Computer10.
The router checks its routing table to determine the appropriate MAC address of Computer10.
10.Which three pieces of information are included in a network physical map? (Choose three)
IP addressing scheme.
Computer naming scheme.
Location and length of cable runs.
Physical location of all networking devices.
Location and size of broadcast and collision domains.
Hardware configuration of end devices such as hosts and services.
11.When using Windows XP, which command shows information about the computer, including IP address, subnet mask, default gateway, and additional details about DHCP and DNS?
i p config
win i p cfg
i p config/all
win i p cfg/all
12.In what area of a network can traffic from other hosts cause a sending host to stop transmitting, then wait a random amount of time before resending a message?
access layer
broadcast domain
collision domain
distribution layer
peer to peer network
