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Unit 2: LAN Configurations

Lesson 2-2: Data Transmission

At a Glance

In this lesson, the process of transmitting data is examined. Computers encode and transmit data, voice, and video over networks via various transmission media. Encoding is the process of transforming information into digital and analog signals. This lesson covers the basics of how data is encoded, decoded, and transmitted. Data packet structure and its relationship to the OSI layers is also covered.

What You Will learn

After completing this lesson, you will be able to: · · · · · Define technical terms associated with data signaling and transmission. Describe the characteristics of digital and analog signaling. Explain how packets and frames are structured, and describe their relationship to the OSI model. Convert binary and hexadecimal digits to decimal digits. Use Sniffer Basic software to capture and analyze packets.

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Tech Talk

· · AmplitudeCharacteristic of a wave measuring wave height from the base to the peak of a waveform. Indicates the strength of the signal. Analog SignalAnalog signals change continuously as opposed to digital signals, which are discretely valued. For example, sound is an analog signal; it is continuous and varies in strength. ASCII CodeAmerican Standard Code for Information Interchange. A 7-bit coding scheme that assigns unique numeric values to letters, numbers, punctuation, and control characters. Baudot CodeA 5-bit coding scheme used for transmitting data. Binary NumbersA number system based on two states, 0 and 1. Computers use combinations of binary numbers to represent and encode all kinds of data including words, sounds, colors, and pictures. Connection-Oriented CommunicationA form of network communication, where the transmitting device must establish a connection with the receiving device before data can be transmitted, (for example, telephone). In connection-oriented communication, the receiving device acknowledges receipt of the data. Connectionless CommunicationA form of communication over networks where the transmitting device can send a message without establishing a connection with the receiving device (for example, radio). Signals are sent, but there is no mechanism for acknowledging receipt. Digital SignalData transmitted in discrete states, for example, on and off. These discrete states can be represented by binary numbers, and vice versa. Full-DuplexTwo-way, simultaneous data transmission. Each device has a separate communication channel. EBCDIC CodeExtended Binary Coded Decimal Interchange Code. An 8-bit coding scheme used by IBM for data representation in mainframe environments. Logical AddressAn OSI model Layer 3 address. FrameBasic unit of data transfer at OSI Layer 2. Half- DuplexTwo-way data transmission that is not simultaneous. Only one device can communicate at a time. PacketBasic unit of data transfer at OSI Layer 3. Physical AddressA OSI model Layer 2 address.

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Data Transmission

Data is transmitted over networks using signals, which are transformed, or encoded, by computers into the voice, video, graphics, and/or the print we see on our computer screens. The signals used by computers to transmit data are either digital or analog. · Analog signals are continuous signals that vary in strength. Sound is an example of an analog signal. Sound is actually a wave and is quite similar, or analogous, to electromagnetic waves, hence the name analog. Telephones have transmitters that encode sound waves into electromagnetic waves, which then travel over wires toward their destination. The receiving telephone decodes the electromagnetic waves back into sound waves. Our brains then decode the sound waves into the words we hear. Computer modems use the same principle. Analog signals can be represented digitally. For instance, a high electromagnetic voltage could be interpreted as 1 and low voltage as 0.

Telephone Encoding/Decoding

Encode

Decode

Cable Source

·

Destination

Digital signals are discrete rather than continuous. Either there is a signal or there isn't a signal. Telegraphs transmit data with discrete signals. You either hear a tap or you do not hear a tap. Discrete signals can be represented by on and off pulses. The duration of a discrete signal can be varied, as with dots and dashes in Morse Code.

Telegraph Encoding/Decoding

Encode

Decode

Cable Source Destination

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Discrete signals can also be represented digitally. The presence of a signal could be coded as a 1 and the absence of a signal coded as a 0. The digits 0 and 1 are used because computer circuitry is based on binary digital data. Codes are used to group a set number of bits together and have a group of bits represent a letter, number, or other character. The computer's brain, the central processing unit (CPU), transforms these codes of 0s and 1s into the voice, video and data we see. One coding scheme, ASCII, codes an "a" as the binary number 0110-0001. Digital data is based on two states, on or off. The binary numbering system uses only two digits, 0 and 1, so it makes sense to use the binary numbering system. One digit, 0 represents off, the other digit represents on. A single 0 or 1 is called a bit. One byte is equal to eight bits (also called an octet when discussing TCP/IP). In ASCII code, one octet is the equivalent of one alphabetic or numeric character. In order to appreciate how computers communicate over networks, it is necessary to be aware of how they encode information.

Connection-Oriented and Connectionless Transmissions

Data transmission may be: · · Connection-oriented Connectionless

The main difference between the two is that with a connection-oriented transmission, the destination device acknowledges receipt. Whereas, with connectionless, there is no acknolwedgement. In connection-oriented transmissions, the sending (source) device establishes a connection with the receiving (destination) device. The connection is continued until all data packets have been transmitted and the source device receives notification that the data was received by the destination device and has been checked for errors. A telephone conversation is an example of a connection-oriented transmission. When a call is made, data is transmitted across phone lines, the receiving party picks up the phone, and a conversation takes place. The individual making the call knows that it arrived at the correct destination and that it was understood. In a connectionless transmission, the source device transmits data but the connection is not maintained. The source device does not wait for notification that the destination device actually received the information accurately. This method is faster than connection-oriented, however less reliable since there is no notification of whether the data is received or not. It is more common to find connectionless transmissions on LANs. To understand a connectionless transmission, think of a radio broadcast: A radio disc jockey tells his/her friends to be sure to listen to her/his program

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at 9:00 p.m. At that time the disk jockey broadcasts a message to them. Did they receive the message? Although it is quite likely, the disk jockey cannot be sure that they turned the radio on, listened, or understood the message.

Synchronous and Asynchronous Transmission

Computers need to know when to expect data and where a character begins and ends. When receiving data, timing on both computer devices must be coordinated if they are to work together efficiently. This coordination is called clocking, timing, or framing. There are two protocols for the timing or coordination of data signals: · · Synchronous Asynchronous

When transferring data, both the transmitting and receiving nodes need to agree when the signal begins and ends so the signals can be correctly measured and interpreted. This timing process is called bit synchronization, framing, or clocking. Imaginehowdifficultitwouldbetoreadifyoudidnotknowwhenawordstartedan dwhenawordendediftherewerenopunctuationandnospacesyoucandoitbecaus ethereareseveraldifferentcharactersanditisnotincodewhatifthiswerecodedas zerosandonesthenyouwouldhaverealproblems. As you can see, synchronization of data is very important. Clocking is somewhat like timing in music. There are a specific number of beats expected per bar. When computer devices are synchronized, a specific number of signals or "beats" are expected within a set amount of time. Timing is important because it helps you be prepared. In many schools, every 50 minutes, a new class period starts. Students watch the clock and expect a signal. Usually, they are already prepared to leave the classroom. That is because they expected the signal. Synchronous transmission requires the communicating devices to maintain synchronous clocks during the entire connection. The sending device transmits on a specific schedule and the receiving device accepts the data on that same fixed schedule. The receiving device knows the timing of the sending device because the timing information is embedded within the preamble of the frame. Synchronous transmissions are common in internal computer communications and usually are sent as entire frames. Synchronous transmission is common when large blocks of data are transferred, since it is efficient and has a low overhead (number of bytes of data/control + data bytes). Asynchronous data transmission does not involve synchronizing the clocks of the sending and receiving devices. Instead, start and stop bits are used for synchronization of data signals. The start and stop bits tell the

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receiving device how to interpret the data. Asynchronous sends one character at a time. Data transmission may be half-duplex; meaning data is transferred in only one direction at a time. An example of half-duplex is a CB radio where only one person can talk at a time. Or, transmission may be full duplex, transmitted in two directions simultaneously. A telephone conversation illustrates full-duplex communication.

Check Your Understanding

Why do the variations in data transmission signals need to be synchronized?

Explain how the two binary numbers, 0s and 1s, are used to interpret data.

Distinguish between connectionless and connection-oriented data transmissions. Give an example of when you think a connectionoriented transmission might be useful.

Analog Signals

Analog signals, which are electromagnetic waves, are continuous and look like a copy of the original sound wave. Transmission of data is accomplished by varying one or more the waves' properties.

Analog Signal

Analog

+ 0 -

All waves have three characteristics, amplitude (strength), frequency, and phase. Variations, called modulations, in wave characteristics are used to encode analog signals to digital signals. Amplitude-Shift Keying (variations in strength) and Frequency-Shift Keying are two examples.

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Amplitude-Shift Keying uses a change of the voltages for interpretation. When there is a voltage change from high to low, the binary digit represented changes. If high voltage were 1 then low voltage would be 0.

Amplitude-Shift Keying

1 0 0

1 0

ASK

Frequency-Shift Keying uses the frequency of the waves for interpretation. When there is a frequency change from high to low, the binary digit changes. If high frequency were 1 then low frequency would be 0 .

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Frequency-Shift Keying

1

0 0

1

FSK

Digital Signals

With digital signaling, either there is or there isn't a signal. There are various encoding schemes that use the "on" "off" signal to represent data.

Digital + 0 -

Depending upon the type of network, different digital encoding schemes are used. For example, Ethernet and Token Ring LANs do not use the same encoding scheme. For computer devices to interpret the data correctly, both the transmitter and receiver must agree on the encoding scheme in order to determine data elements and their values. When new technologies are invented, new encoding protocols often need to be established.

Check Your Understanding

What are the three characteristics of waves that are used when transmitting data?

Why will new technologies need new encoding schemes?

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Data Transmission and the OSI Model

When transmitting data over networks, conforming to the OSI model is important. As discussed in the previous lesson, data travels vertically through the seven OSI layers. Data is encapsulated at each layer of the transmitting device from top to bottom and stripped at the receiving device in the reverse direction. The protocols of the OSI model are used to organize the data into packets, with headers and trailers. OSI Model Original Data with Headers and Trailers

Data Hp Hs Ht Hn Hd Data Data Data Data Data Data T T

Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer

OSI communication is as follows: · · · Each layer communicates with layers both immediately above and below it. Each layer from the sending (source) station also communicates with its peer layer at the receiving (destination) computer. Data starts at the application layer of the source device and descends through the remaining layers before being transmitted to the destination device. As each layer receives the data from the layer above, it adds, in the form of headers, its data. This data contains various protocols that enable communication. The original data, with the new header and the headers from the previous layers, is then sent to the next layer down. When the data reaches the Physical Layer, it is transmitted across various media to the destination device.

·

· ·

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· ·

The destination device receives the entire frame and sends it up through the layers, one after the other in sequence. Each layer strips the header added by its peer layer at the source device.

Ethernet packets can contain approximately 1,000 bytes. If the data being transmitted is larger than 1,000 bytes then the computer breaks it down into packets. Each packet is transmitted and received separately. Packets are sequentially numbered. This allows the receiving computer to recreate the data in the correct order. Depending upon the protocols used, packet size can change.

Transmission of Data through the OSI Layers

Data transfer begins at the application layer of the source device and each OSI layer adds header and/or trailer information to help ensure efficient, error free transfer of data. The destination device receives the data and the data is transferred up through the layers. Each strips the information added by its peer layer and moves the remaining data to the next layer. Eventually, the data is returned to its original form at the application layer.

Application Layer

Data

The application layer serves as an interface between user applications and network services, such as electronic mail. Data input by the user is then sent to the next layer, the presentation layer.

Presentation Layer

Hp

Data

Header information is added by presentation layer protocols. This layer is responsible for translation, encryption, and compression of data. If necessary, it is this layer that translates local data, such as ASCII and EBCDIC.

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Session Layer

Hs Hp

Data

At the session layer, checkpoints are built in to ensure successful data transmission. If transmissions are proceeding smoothly, they continue. If not, retransmission of data takes place. This layer provides the user interface, in the form of passwords and logins, which allow network access.

Transport Layer

H t Hs Hp

Data

The transport layer provides for message segmentation and ensures errorfree delivery, without loss or duplication.

Network Layer

Hn H t H s Hp

Data

At the network layer, header information identifies the "logical" source and destination addresses of the network. The logical network differs from the physical MAC address. The logical address assists with the routing of data from network to network. Factors affecting routing decisions include cost, speed, network conditions, and priorities.

Data Link Layer

Hd Hn H t Hs Hp

Data

T

Frames are built at the data link layer. The headers and trailers added at this layer control error handling and synchronization over the local segment. This is where the "physical" address of the destination and the source address of the sender are added.

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Physical Layer

The physical layer of the OSI controls the electrical aspects of data transfer, such as voltage levels, signal timing, and encoding. Physical Layer Frame with Preamble, Headers, and Trailers

Transport Header Data Link Presentation Header Header

Hd Hn H t Hs Hp

Data

T

Physical Preamble Session Header Header Network Header

Trailer

Although real network applications don't always incorporate protocols from every layer, or sometimes combine the functions of two layers, it is important to understand how the OSI model is used as a framework for the protocols used when transmitting data. Transmission of data packets occurs in both directions. Peer layers communicate back and forth when a data packet is being sent. What is actually taking place is a checking sequence. For example, does the address match, is there any congestion, which is the best route, are the destination and source devices synchronized, is it time to terminate the connection? All of this takes place in a fraction of a second.

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Check Your Understanding

What is the difference between half-duplex and full duplex transmission?

How is sending a registered letter through the mail similar to sending data over a network?

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Try It Out Converting Binary and Hexadecimal to Decimal Numerals

Computers are electrical devices. Electrical pulses can be turned "on" or "off." Binary digits 0 and 1 can be used to represent "on" and "off" pulses. Computers use these 0s and 1s to represent data, which they then interpret using various codes. In computer language, each 0 or 1 is considered a bit and eight bits are equal to an octet (byte). One octet generally represents one character of data. We use and understand a base-10 numbering system in everyday life. Base-10 uses the digits 0-9. In order to understand how computers transmit data, it is necessary to understand two additional numbering systems, base-2 and base-16. Two digits, 0 and 1, are used for base-2 numbering and 10 digits plus 6 characters from our alphabet are used for base-16 numbering. ASCII code uses the base-2, or binary, numbering system and hexadecimal code, uses the base-16, or hex, numbering system. In hexadecimal numbering, there are 16 symbols for the decimal numbers 0-15. The numbers 0 to 9 represent the decimal numerals 0 to 9. The decimal numbers 10 to 15 are represented by the alphabetic characters A to F, e.g., A=10, B=11, C=12, D=13, E=14, F=15. Hexadecimal numbers can be used to represent 8 bits as two hexadecimal digits. MAC addresses, which you will learn about later in this course, use hex numbers for address identification.

Materials Needed

·

None

In this activity, you will attempt to convert decimal, binary, and hexadecimal numbers. Use the data from the following tables to help with conversions.

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Number Equivalents Decimal 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Binary 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F

When numbering, we give each digit column a name or positional value. We do this for convenience when reading numbers. The column value is determined by raising the base (decimal, binary, or hexadecimal) to a power as shown in the charts below.

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When using a base-10 number such as 34,752, each of the numbers has a decimal positional value based on the powers of 10. 2 is in the 1s position, 5 in the 10s position, 7 in the 100s position, 4 in the 1,000 position, and 3 in the 10,000 position.

Decimal (Base 10) Positional (Column) Values

100 = 1s column/position 101 = 10s column/position 102 = 100s column/position 103 = 1,000s column/position 104 = 10,000s column/position Or: 3 4, 7 5 2 Ones position Tens position Hundreds position Thousands position Ten thousands position Binary (Base 2) Positional (Column) Values When you use a base-2 number such as 11011001, each of the numbers has a decimal positional value based on the powers of 2. Starting from the right, 1 is in the 1s position, 0 in the 2s position, 0 in the 4s position, 1 in the 8s position, and 1 in the 16s position, 0 in the 32s position, 1 in the 64s position, and 1 in the 128s position. 20 21 22 23 24 28 216 2128 = 1s column = 2s column = 4s column = 8s column = 16s column = 32s column = 64s column = 128s column

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Or, 1 1 0 1 1 0 0 1 1s 2s 4s 8s 16s 32s 64s 128s Hexadecimal (Base 16) Positional (Column) Values When you use a base-16 number such as B620A each of the numbers has a decimal positional value based on the powers of 16. Starting from the right, A is in the 1s position, 0 in the 16s position, 2 in the 256s position, 6 in the 4,096 position, and B in the 65,536s position. 160 161 162 163 164 = 1s column/position = 16s column/position = 256s column/position = 4,096s column/position = 65,536s column/position

Or, B 6 2 0 A Ones position Sixteens position Two hundred fifty-sixes position Four thousand ninety-sixes position Sixty-five thousands, five hundred thirty-sixes position

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Converting a Binary Number to a Decimal Number

Example: Convert the Binary number 101100 to a decimal number. 1. To change from a binary number to a decimal number you must first determine the binary digit's positional value, see chart on previous page. Start at the right: 0=1, 0=2, 1=4, 1=8, 0=16, and 1=32. Binary Digit Value

0 0 1 1 0 1

Positional Value

1 2 4 8 16 32

2. Multiply the binary digit value and the positional value for each digit. 0x1=0, 0x2=0, 1x4=4, 1x8=8, 1x32=32. Binary Digit Value

0 0 1 1 0 1

Positional Value

1 2 4 8 16 32

Product of Binary Digit and Positional Values

0 0 4 8 0 32

3. Add the products together: 0 + 0 + 4 + 8 + 0 + 32 = 44. 4. The sum of the products of the binary digit and positional values is equal to the decimal number. Binary number 101100 is equal to a decimal value of 44.

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Convert the following binary numbers to decimals. Follow the steps above. Show your work. a. 110011

b. 0011

c. 010101

d. 1111

e. 01010101

Converting a Hexadecimal Number to a Decimal Number

Example: Convert the hex number 5B6A to a decimal number. 1. To change from a hexadecimal number to a decimal number you must first change the hex value to a decimal value. Look on the number equivalents chart and change the hex digits to decimal digits. 5 = 5; B= 11; 6 = 6; A = 10. Hexadecimal Value

5 B 6 A

Decimal Value

5 11 6 10

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2. Determine the positional value for each hex digit (see Positional Value Tables): 5 is in the fourth position so the positional value is 4,096. B is in the third position so the positional value is 256; 6 is in the second position so the positional value is 16; and A is in the first position so the positional value is 1. Hexadecimal Value

5 B 6 A

Decimal Value

5 11 6 10

Hex Positional Value

4,096 256 16 1

3. Multiply the decimal value and the positional value for each hexadecimal. 5 x 4,096 = 20,480; 11 x 256 = 2,816; 6 x 16 = 96; 10 x 1 = 10. Hexadecimal Value

5 B 6 A

Decimal Value

5 11 6 10

Hex Positional Value

4,096 256 16 1

Product of Decimal and Hex Positional Values

20,480 2,816 96 10

4. Step 4: Add the products together. 20,480 + 2,816 + 96 + 10 = 23,402. Hexadecimal Value

5 B 6 A

Decimal Value

5 11 6 10

Hex Positional Value

4,096 256 16 1

Product of Decimal and Hex Positional Values

20,480 2,816 96 10

5. Step 5: The sum of the products of the decimal and hex positional values is equal to the decimal number. Hexadecimal number 5B6A = decimal number 23,402.

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Try the following hexadecimal numbers to decimal numbers. Follow the steps listed above. Show your work. a. 237AF

b. 57

c. 392

d. FFF

e. BB41A

Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score

Accurate conversions All work shown TOTAL

40 60 100

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Stretch Yourself: Launching Sniffer Basic Capturing Packets

Sniffer Basic is software used by information services technicians to help analyze networks and locate problems. In this activity, data packets will be captured and stored. If Sniffer Basic is not installed on your computer, see your instructor. Be sure you are connected to a network when completing this activity.

Materials Needed

· · ·

Basic Sniffer Software (NetXRay) Network Connection Internet Connection (optional)

1. Double-click the Sniffer Basic desktop icon, or select it from the Start menu/Programs list. If you have more than one NIC adapter, a screen similar to the one below will be displayed and you will be prompted to choose an adapter to monitor.

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2. From the toolbar, select Help Topics. A screen similar to the following will appear. Should you have any problems when you use Sniffer Basic, the help menu is very useful.

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3. Close the Help window. 4. On the Capture menu, click Start. In the Profile box, select default and click to start capture.

5. You should see a screen similar to the following:

Is the packet capture gauge incrementing?

6. Spend some time exploring this software. You will be using it throughout the course. 7. In the Capture Panel window, click to stop capture. Then click .

8. In the View window, you will notice three separate windows: · · · The top window lists the packets that were captured. The middle window lists all packet specific information in a verbal description. The bottom window displays the actual packet data in hexadecimal.

9. Print each of these screens and save.

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Generating Traffic

1. Keep Sniffer Basic in capture mode. You are going to generate some traffic over your network. 2. From your desktop, double-click the Network Neighborhood icon: You will recognize a list of the computers in your network (if not, notify your instructor). 3. Double-click one of the names. What workstation's node name did you choose? 4. Copy a file from your local PC to the computer you chose in step 2. 5. Now verify the file copy was successful. How did you do this?

Viewing Captured Data

Return to the Sniffer Basic application. 10. In the Capture Panel window, click to stop capture. Then click .

11. In the View window, you will notice three separate windows: · · · The top window lists the packets that were captured. The middle window lists all packet specific information in verbal description. The bottom window displays the actual packet data in hexadecimal.

12. Print each of these screens and save. 13. In the top window, select a row that has NetBIOS in the Layer column. 14. Scroll down through the information in the middle window and look for workstation node names. Find the one that you copied your file to.

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15. Scroll to the top of the middle window to the address field. There are two MAC addresses, the one on the left is the source address, and the one on the right is the destination address. What is the node name in the packet you are viewing?

What are the source and destination MAC addresses? What do you think the source and destination addresses are for?

What data link protocol is being used?

Protocol Distribution

1. Close the packet capture window and do not save the data. 2. From the toolbar, click Tools, then Protocol Distribution button. 3. After a few seconds, you should see several different protocols being displayed. Which protocol do you see?

Which protocol generated the most traffic? 4. Go back and copy that file back from the computer you copied it to. Notice how the chart changes. 5. If you are connected to the Internet, use your browser and hit several web sites. Again notice the changes on the chart. Describe changes you noticed. Why do you think there are so many changes?

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Host Table

7. From the toolbar, select Tools then click the Host Table button. This displays, in pie chart fashion, the busiest nodes on the network. 8. From the toolbar on the left of this window, you can change the display to a bar chart, outline, or detail view. How many hardware addresses are listed?

Which nodes do they represent?

How can you find out which nodes are represented by each hardware address?

The data represented by the Host Table is from which layer of the OSI model?

Summary

In this lab, you launched Sniffer Basic and captured network traffic to view packets, determine the type of protocols used, and the amount of traffic generated in your network. Save the printed data from the three windows and place them in your portfolio. How do you think a network administrator uses this information to assist him/her with the job of managing and planning network expansions? Write a short essay on this topic and submit it to your teacher.

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Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score

Essay on how a network administrator would use information gathered from Sniffer Basic software. Directions followed, data recorded as specified, and questions answered completely and accurately. Printed materials placed in portfolio Participation and active engagement TOTAL

40 35

10 15 100

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Network Wizards Code Research

Select one of the following topics to research.

Materials Needed

· ·

Internet Connection ASCII code from another source

1. Search the Internet for the code for interpreting ASCII. 2. Using ASCII code, write the following sentence: Hello, how are you? Look at the length of the code. Search the Internet to determine how much time it takes for a byte of information to be sent over a network. How long would it take to send this message? Calculate how many bytes are in your name. How long would it take for your name to be sent over the network? Can you see why computers need to break data into packets? Explain why this is the case. Prepare a one-page summary of your findings. Present your findings to the class. Create a visual display for your presentation. 3. Baudot, ASCII, and EBCDIC are three codes used for the transmission of data. Research these codes and their history. Prepare a one-page summary of your findings. Present your findings to the class. Create a visual display for your presentation.

Rubric: Suggested Evaluation Criteria and Weightings Criteria % Your Score

On time delivery of assignment Content and quality of one-page summary Content and quality of class presentation Creativity, originality, and quality of visual aid Organization, spelling, and grammar TOTAL

10 25 25 25 15 100

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Summary

In this lesson, you learned the following: · · · · · Technical definitions associated with data signaling and transmission. The characteristics of digital signaling, analog signaling. What packets and frames are, how they are structured, and their relationship to the OSI model. How to convert binary and hexadecimal digits to decimal digits. How to use Sniffer Basic software to capture and analyze packets.

Review Questions

Lesson 2-2: Data Transmission

Part A

Name___________________

1. Describe analog signals. How are they used to transmit data?

2. Describe digital signals.

3. Describe synchronous data transmission.

4. Describe asynchronous data transmission.

5. What is the difference between half-duplex and full duplex transmissions?

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6. There is a timing process that signals the beginning and ending of data so it can be correctly measured. This process is called what? a. Digital signaling b. Analog signaling c. Bit synchronization d. Asynchronous e. Synchronous

7. Which type of signaling scheme represents data sent as discrete signals? a. Digital signaling b. Analog signaling c. Asynchronous d. Synchronous

8. Which type of signaling scheme represents continuously changing data? a. Digital signaling b. Analog signaling c. Asynchronous d. Synchronous

9. Which type of bit synchronization transmission requires both a start bit and a stop bit for clocking purposes? a. Digital signaling b. Analog signaling c. Asynchronous d. Synchronous

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10. Group of bits, including data and control signals, arranged in a specific format and transmitted as a whole, are called what? a. Clocking b. Sequencing c. Synchronization d. Packets

Part B

1. Describe the difference between analog and digital signaling waves/pulses.

2. What is binary notation and how is it used to transfer data signals over network media?

3. List three characteristics of waves that are used to encode data.

Part C

1. Use the OSI model as your reference and explain how data packets are structured. Give several examples of information that may be contained within headers . Draw a diagram showing packet addition at each layer.

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Scoring

Rubric: Suggested Evaluation Criteria and Weightings

Criteria Part A: Technical definitions associated with data signaling and transmission. Part B: Describe the characteristics of digital signaling, analog signaling. Part C: What packets and frames are, how they are structured, and their relationship to the OSI model. TOTAL Try It Out: How to convert binary and hexadecimal digits to decimal digits. Stretch Yourself: How to use Sniffer Basic software to capture and analyze packets. Network Wizards FINAL TOTAL

% 30 35 35

Your Score

100 100 100 100 400

Resources

Aschermann, Robert (1998). MCSE Networking Essentials for Dummies. IDG Books Worldwide, Inc. Forest City, California. Baker, R. (1996). Data Communications Home Page. Available: www.georcoll.on.ca/staff/rbaker /intro.sht [1999, May 13]. Bert Glen (1998). MCSE Networking Essentials: Next Generation Training Second Edition. New Riders Publishing. Indianapolis Indiana. Chellis, James; Perkins, Charles; & Strebe Matthew (1997). MCSE Networking Essentials Study Guide. Sybex Inc. Alameda California CMP Media, Inc. (1999). FDDI fundamentals. In Data Communications Tech Tutorials [Online]. Available: www.data.com/Tutorials/FDDI_Fundamentals [1999, April 20]. Computer and Information Science, Ohio State University (No date). Data Communications Cabling FAQ. [Online].Available: www.cis.ohiostate.edu/hypertext/faq/usenet/LANs/cabling-faq/faq.html [1999, May 13].

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Derfler, Jr., Frank J., & Freed, L. (1998). How Networks Work, Fourth Edition. Macmillan Computer Publishing/Que Corporation. Indianapolis, Indiana. Hayden, Matt. (1998). Sam's Teach Yourself Networking in 24 Hours. Sam's Publishing, Indianapolis, Indiana. Microsoft Corporation (1998). Dictionary of Computer Terms, Microsoft Press, Redmond, Washington. Nortel Networks (1998). Internetworking Fundamentals: Student Guide. Bay Networks Inc. Billerica, Massachusetts. Palmer , Michael J. (1998) Hands-On Networking Essentials with Projects, Course Technology, Inc. Cambridge, Massachusetts.

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