09CS 301: DATA COMMUNICATION QUESTION BANK

UNIT 1 Chapter: I

INTRODUCTION

1. Identify the five components of a data communications system.

2. What are the advantages of distributed processing?

3. What are the three criteria necessary for an effective and efficient network?

4. What are the advantages of a multipoint connection over a point-to-point

connection?

5. What are the two types of line configuration?

6. Categorize the four basic topologies in terms of line configuration.

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

8. Name the four basic network topologies, and cite an advantage of each type.

9. For n devices in a network, what is the number of cable links required for a mesh,ring, bus, and star topology?

10. What are some of the factors that determine whether a communication system is a LAN or WAN?

1I. What is an internet? What is the Internet?

12. Why are protocols needed?

13. Why are standards needed?

14. What is the maximum number of characters or symbols that can be represented by Unicode?

15. A color image uses 16 bits to represent a pixel. What is the maximum number of different colors that can be represented?

16. Assume six devices are arranged in a mesh topology. How many cables are needed?How many ports are needed for each device?

17. For each of the following four networks, discuss the consequences if a connection fails.

a. Five devices arranged in a mesh topology

b. Five devices arranged in a star topology (not counting the hub)

c. Five devices arranged in a bus topology

d. Five devices arranged in a ring topology

18. Draw a hybrid topology with a star backbone and three ring networks.

19. Draw a hybrid topology with a ring backbone and two bus networks.

20. Performance is inversely related to delay. When you use the Internet, which of the following applications are more sensitive to delay?

a. Sending an e-mail

b. Copying a file

c. Surfing the Internet

21. When a party makes a local telephone call to another party, is this a point-to-point or multipoint connection? Explain your answer.

22. Compare the telephone network and the Internet. What are the similarities? What are the differences?

Unit 1 Chapter 2

NETWORK MODEL

1. List the layers of the Internet model.

2. Which layers in the Internet model are the network support layers?

3. Which layer in the Internet model is the user support layer?

4. What is the difference between network layer delivery and transport layer delivery?

5. What is a peer-to-peer process?

6. How does information get passed from one layer to the next in the Internet

model?

7. What are headers and trailers, and how do they get added and removed?

8. What are the concerns of the physical layer in the Internet model?

9. What are the responsibilities of the data link layer in the Internet model?

10. What are the responsibilities of the network layer in the Internet model?

11. What are the responsibilities of the transport layer in the Internet model?

12. What is the difference between a port address, a logical address, and a physical

address?

13. Name some services provided by the application layer in the Internet model.

14. How do the layers of the Internet model correlate to the layers of the OSI model?

15. How are OSI and ISO related to each other?

16. Match the following to one or more layers of the OSI model:

a. Route determination

b. Flow control

c. Interface to transmission media

d. Provides access for the end user

I 7.Match the following to one or more layers of the OSI model:

a. Reliable process-to-process message delivery

b. Route selection

c. Defines frames

d. Provides user services such as e-mail and file transfer

e. Transmission of bit stream across physical medium

18. Match the following to one or more layers of the OSl model:

a. Communicates directly with user's application program

b. Error correction and retransmission

c. Mechanical, electrical, and functional interface

d. Responsibility for carrying frames between adjacent nodes

19. Match the following to one or more layers of the OSI model:

a. Format and code conversion services

b. Establishes, manages, and terminates sessions

c. Ensures reliable transmission of data

d. Log-in and log-out procedures

e. Provides independence from differences in data representation

22. Suppose a computer sends a frame to another computer on a bus topology LAN. The physical destination address of the frame is corrupted during the transmission. What happens to the frame? How can the sender be informed about the situation?

23. Suppose a computer sends a packet at the network layer to another computer

somewhere in the Internet. The logical destination address of the packet is cor-

rupted. What happens to the packet? How can the source computer be informed of

the situation?

24. Suppose a computer sends a packet at the transport layer to another computer

somewhere in the Internet. There is no process with the destination port address

running at the destination computer. What will happen?

25. If the data link layer can detect errors between hops, why do you think we need

another checking mechanism at the transport layer?

Unit: 2 Chapter 3

PHYSICAL LAYER AND MEDIA

1. What is the relationship between period and frequency?

2. What does the amplitude of a signal measure? What does the frequency of a signal measure? What does the phase of a signal measure?

3. How can a composite signal be decomposed into its individual frequencies?

4. Name three types of transmission impairment.?

5. Distinguish between baseband transmission and broadband transmission.?

6. Distinguish between a low-pass channel and a band-pass channel.?

7. What does the Nyquist theorem have to do with communications?

8. What does the Shannon capacity have to do with communications?

9. Why do optical signals used in fiber optic cables have a very short wave length?

10. Can we say if a signal is periodic or nonperiodic by just looking at its frequency domain plot? How?

11. Is the frequency domain plot of a voice signal discrete or continuous?

12. Is the frequency domain plot of an alarm system discrete or continuous?

13. We send a voice signal from a microphone to a recorder. Is this baseband or broadband transmission?

14. We send a digital signal from one station on a LAN to another station. Is this baseband or broadband transmission?

15. We modulate several voice signals and send them through the air. Is this baseband or broadband transmission?

16. Given the frequencies listed below, calculate the corresponding periods.

a. 24Hz

b. 8 MHz

c. 140 KHz

17. Given the following periods, calculate the corresponding frequencies.

a. 5 s

b. 12 Jls

c. 220 ns

18. What is the phase shift for the foIlowing?

a. A sine wave with the maximum amplitude at time zero

b. A sine wave with maximum amplitude after 1/4 cycle

c. A sine wave with zero amplitude after 3/4 cycle and increasing

19. What is the bandwidth of a signal that can be decomposed into five sine waves

with frequencies at 0, 20, 50, 100, and 200 Hz? All peak amplitudes are the same.

Draw the bandwidth.

20. A periodic composite signal with a bandwidth of 2000 Hz is composed of two sine waves. The first one has a frequency of 100 Hz with a maximum amplitude of 20 V,the second one has a maximum amplitude of 5 V. Draw the bandwidth.

21. Which signal has a wider bandwidth, a sine wave with a frequency of 100 Hz or a,sine wave with a frequency of 200 Hz?

22. What is the bit rate for each of the following signals?

a. A signal in which 1 bit lasts 0.001 s

b. A signal in which 1 bit lasts 2 ms

c. A signal in which 10 bits last 20 J-ls

23. A device is sending out data at the rate of 1000 bps.

a. How long does it take to send out 10 bits?

b. How long does it take to send out a single character (8 bits)?

c. How long does it take to send a file of 100,000 characters?

24. A signal travels from point A to point B. At point A, the signal power is 100 W. At point B, the power is 90W. What is the attenuation in decibels?

25. The attenuation of a signal is -10 dB. What is the final signal power if it was originally 5W?

26. A signal has passed through three cascaded amplifiers, each with a 4 dB gain.

What is the total gain? How much is the signal amplified?

27. If the bandwidth of the channel is 5 Kbps, how long does it take to send a frame of 100,000 bits out of this device? The light of the sun takes approximately eight minutes to reach the earth. What is the distance between the sun and the earth?

28. A signal has a wavelength of 1 11m in air. How far can the front of the wave travel during 1000 periods?

29. A line has a signal-to-noise ratio of 1000 and a bandwidth of 4000 KHz. What is the maximum data rate supported by this line?

30. We measure the performance of a telephone line (4 KHz of bandwidth). When the signal is 10 V, the noise is 5 mV. What is the maximum data rate supported by this telephone line?

31. A computer monitor has a resolution of 1200 by 1000 pixels. If each pixel uses

1024 colors, how many bits are needed to send the complete contents of a screen?

32. If the peak voltage value of a signal is 20 times the peak voltage value of the noise, what is the SNR? What is the SNR ?

33. We need to upgrade a channel to a higher bandwidth. Answer the following

questions: a. How is the rate improved if we double the bandwidth?

b. How is the rate improved if we double the SNR?

34. We have a channel with 4 KHz bandwidth. If we want to send data at 100 Kbps,what is the minimum SNR ?What is SNR?

35. What is the transmission time of a packet sent by a station if the length of the

packet is 1 million bytes and the bandwidth of the channel is 200 Kbps?

36. What is the length of a bit in a channel with a propagation speed of 2 x 10 mls if the channel bandwidth is

a. 1Mbps?

h. 10 Mbps?

c. 100 Mbps?

37. How many bits can fit on a link with a 2 ms delay if the bandwidth of the link is

a. 1Mbps?

b. 10 Mbps?

c. 100 Mbps?

UNIT 2:CHAPTER 4:

DIGITAL TRANSMISSION

1. List three techniques of digital-to-digital conversion.

2. Distinguish between a signal element and a data element.

3. Distinguish between data rate and signal rate.

4. Define baseline wandering and its effect on digital transmission.

5. Define a DC component and its effect on digital transmission.

6. Define the characteristics of a self-synchronizing signal.

7. List five line coding schemes discussed in this book.

8. Define block coding and give its purpose.

9. Define scrambling and give its purpose.

10. Compare and contrast PCM and DM.

11. What are the differences between parallel and serial transmission?

12. List three different techniques in serial transmission and explain the differences.

13. Calculate the value of the signal rate for each case in Figure 4.2 if the data rate is 1Mbps and c = 1/2.

14. In a digital transmission, the sender clock is 0.2 percent faster than the receiver clock. How many extra bits per second does the sender send if the data rate is 1Mbps?

15. Draw the graph of the NRZ-L scheme using each of the following data streams,

assuming that the last signa11evel has been positive. From the graphs, guess the

bandwidth for this scheme using the average number of changes in the signal level.

Compare your guess with the corresp.onding entry in Table 4.1.

a. 00000000

b. 11111111

c. 01010101

d. 00110011

16. Repeat Exercise 15 for the NRZ-I scheme.

17. Repeat Exercise 15 for the Manchester scheme.

18. Repeat Exercise 15 for the differential Manchester scheme.

19. Repeat Exercise 15 for the 2B1Q scheme, but use the following data streams.

a. 0000000000000000

b. 1111111111111111

c. 0101010101010101

d. 0011001100110011

20. Repeat Exercise 15 for the MLT-3 scheme, but use the following data streams.

a. 00000000

b. 11111111

c. 01010101

d. 00011000

21. An NRZ-I signal has a data rate of 100 Kbps. Using Figure 4.6, calculate the value of the normalized energy (P) for frequencies at 0 Hz, 50 KHz, and 100 KHz.

22. A Manchester signal has a data rate of 100 Kbps. Using Figure 4.8, calculate the value of the normalized energy (P) for frequencies at 0 Hz, 50 KHz, 100 KHz.

23. The input stream to a 4B/5B block encoder is 0100 0000 0000 0000 0000 OOOI. Answer the following questions:

a. What is the output stream?

b. What is the length of the longest consecutive sequence of Os in the input?

c. What is the length of the longest consecutive sequence of Os in the output?

24. How many invalid (unused) code sequences can we have in 5B/6B encoding? How many in 3B/4B encoding?

25. What is the result of scrambling the sequence 11100000000000 using one of the following scrambling techniques? Assume that the last non-zero signal level has been positive.

a. B8ZS

b. HDB3 (The number of nonzero pules is odd after the last substitution)

26. What is the Nyquist sampling rate for each of the following signals?

a. A low-pass signal with bandwidth of 200 KHz?

b. A band-pass signal with bandwidth of 200 KHz if the lowest frequency is 100 KHz?

27. We have sampled a low-pass signal with a bandwidth of 200 KHz using 1024 levels of quantization.

a. Calculate the bit rate of the digitized signal.

b. Calculate the SNR for this signal. dB

c. Calculate the PCM bandwidth of this signal.

28. What is the maximum data rate of a channel with a bandwidth of 200 KHz if we use four levels of digital signaling.

29. An analog signal has a bandwidth of 20 KHz. If we sample this signal and send it through a 30 Kbps channel what is the SNR ? dB

30. We have a baseband channel with a I-MHz bandwidth. What is the data rate for

this channel if we use one of the following line coding schemes?

a. NRZ-L

b. Manchester

c. MLT-3

d. 2B1Q

31. We want to transmit 1000 characters with each character encoded as 8 bits.

a. Find the number of transmitted bits for synchronous transmission.

b. Find the number of transmitted bits for asynchronous transmission.

c. Find the redundancy percent in each case.

Unit 2: Chapter 5

ANALOG TRANSMISSION

1. Define analog transmission.

2. Define carrier signal and its role in analog transmission.

3. Define digital-to-analog conversion.

4. Which characteristics of an analog signal are changed to represent the digital signal in each of the following digital-to-analog conversion?

a. ASK

b. FSK

c. PSK

d. QAM

5. Which of the four digital-to-analog conversion techniques (ASK, FSK, PSK or

QAM) is the most susceptible to noise? Defend your answer.

6. Define constellation diagram and its role in analog transmission.

7. What are the two components of a signal when the signal is represented on a constellation diagram? Which component is shown on the horizontal axis? Which is shown on the vertical axis?

8. Define analog-to-analog conversion?

9. Which characteristics of an analog signal are changed to represent the lowpass analog signal in each of the following analog-to-analog conversions?

a. AM

b. FM

c. PM

10. Which of the three analog-to-analog conversion techniques (AM, FM, or PM) is the most susceptible to noise? Defend your answer.

11. Calculate the baud rate for the given bit rate and type of modulation.

a. 2000 bps, FSK

b. 4000 bps, ASK

c. 6000 bps, QPSK

d. 36,000 bps, 64-QAM

12. Calculate the bit rate for the given baud rate and type of modulation.

a. 1000 baud, FSK

b. 1000 baud, ASK

c. 1000 baud, BPSK

d. 1000 baud, 16-QAM

13. What is the number of bits per baud for the following techniques?

a. ASK with four different amplitudes

b. FSK with 8 different frequencies

c. PSK with four different phases

d. QAM with a constellation of 128 points.

14. Draw the constellation diagram for the following:

a. ASK, with peak amplitude values of 1 and 3

b. BPSK, with a peak amplitude value of 2

c. QPSK, with a peak amplitude value of 3

d. 8-QAM with two different peak amplitude values, I and 3, and four different

phases.

15. Draw the constellation diagram for the following cases. Find the peak amplitude value for each case and define the type of modulation (ASK, FSK, PSK, or QAM).

The numbers in parentheses define the values of I and Q respectively.

a. Two points at (2, 0) and (3, 0).

b. Two points at (3, 0) and (-3, 0).

c. Four points at (2, 2), (-2, 2), (-2, -2), and (2, -2).

d. Two points at (0 , 2) and (0, -2).

16. How many bits per baud can we send in each of the following cases if the signal constellation has one of the following number of points?

a. 2

b. 4

c. 16

d. 1024

17. What is the required bandwidth for the following cases if we need to send 4000 bps? Let d = 1.

a. ASK

b. FSK with =4 KHz 2~f

c. QPSK

d. 16-QAM

18. The telephone line has 4 KHz bandwidth. What is the maximum number of bits we can send using each of the following techniques? Let d = O.

a. ASK

b. QPSK

c. 16-QAM

d.64-QAM

19. A corporation has a medium with a I-MHz bandwidth (lowpass). The corporation needs to create 10 separate independent channels each capable of sending at least 10 Mbps. The company has decided to use QAM technology. What is the mini-mum number of bits per baud for each channel? What is the number of points in the constellation diagram for each channel? Let d =O.

20. A cable company uses one of the cable TV channels (with a bandwidth of 6 MHz) to provide digital communication for each resident. What is the available data rate

0for each resident if the company uses a 64-QAM technique?

21. Find the total number of channels in the corresponding band allocated by FCC.

a. AM

b. FM

UNIT 2:CHAPTER 6

BANDWIDTH UTILIZATION

1. Describe the goals of multiplexing.

2. List three main multiplexing techniques mentioned in this chapter.

3. Distinguish between a link and a channel in multiplexing.

4. Which of the three multiplexing techniques is (are) used to combine analog signals?Which of the three multiplexing techniques is (are) used to combine digital signals?

5. Define the analog hierarchy used by telephone companies and list different levels of the hierarchy.

6. Define the digital hierarchy used by telephone companies and list different levels of the hierarchy.

7. Which of the three multiplexing techniques is common for fiber optic links?

Explain the reason.

8. Distinguish between multilevel TDM, multiple slot TDM, and pulse-stuffed TDM.

9. Distinguish between synchronous and statistical TDM.

10. Define spread spectrum and its goal. List the two spread spectrum techniques discussed in this chapter.

11. Define FHSS and explain how it achieves bandwidth spreading.

12. Define DSSS and explain how it achieves bandwidth spreading.

13. Assume that a voice channel occupies a bandwidth of 4 kHz. We need to multiplex 10 voice channels with guard bands of 500 Hz using FDM. Calculate the required bandwidth.

14. We need to transmit 100 digitized voice channels using a pass-band channel of

20 KHz. What should be the ratio of bits/Hz if we use no guard band?

15. In the analog hierarchy of Figure 6.9, find the overhead (extra bandwidth for guard band or control) in each hierarchy level (group, supergroup, master group, and jumbo group).

16. We need to use synchronous TDM and combine 20 digital sources, each of 100 Kbps. Each output slot carries 1 bit from each digital source, but one extra bit is added to each frame for synchronization. Answer the following questions:

a. What is the size of an output frame in bits?

b. What is the output frame rate?

c. What is the duration of an output frame?

d. What is the output data rate?

e. What is the efficiency of the system (ratio of useful bits to the total bits).

17. Repeat Exercise 16 if each output slot carries 2 bits from each source.

18. We have 14 sources, each creating 500 8-bit characters per second. Since only some of these sources are active at any moment, we use statistical TDM to combine these sources using character interleaving. Each frame carries 6 slots at a time, but we need to add four-bit addresses to each slot. Answer the following questions:

a. What is the size of an output frame in bits?

b. What is the output frame rate?

c. What is the duration of an output frame?

d. What is the output data rate?

19. Ten sources, six with a bit rate of 200 kbps and four with a bit rate of 400 kbps are to be combined using multilevel TDM with no synchronizing bits. Answer the following questions about the final stage of the multiplexing:

a. What is the size of a frame in bits?

b. What is the frame rate?

c. What is the duration of a frame?

d. What is the data rate?

20. Four channels, two with a bit rate of 200 kbps and two with a bit rate of 150 kbps, are to be multiplexed using multiple slot TDM with no synchronization bits. Answer the following questions:

a. What is the size of a frame in bits?

b. What is the frame rate?

c. What is the duration of a frame?

d. What is the data rate?

21. Two channels, one with a bit rate of 190 kbps and another with a bit rate of 180 kbps, are to be multiplexed using pulse stuffing TDM with no synchronization bits. Answer the following questions:

a. What is the size of a frame in bits?

b. What is the frame rate?

c. What is the duration of a frame?

d. What is the data rate?

22. Answer the following questions about a T-1 line:

a. What is the duration of a frame?

b. What is the overhead (number of extra bits per second)?

23. Show the contents of the five output frames for a synchronous TDM multiplexer that combines four sources sending the following characters. Note that the characters are sent in the same order that they are typed. The third source is silent.

a. Source 1message: HELLO

b. Source 2 message: HI

c. Source 3 message:

d. Source 4 message: BYE

24. Answer the following questions about the digital hierarchy in Figure 6.23:

a. What is the overhead (number of extra bits) in the DS-l service?

b. What is the overhead (number of extra bits) in the DS-2 service?

c. What is the overhead (number of extra bits) in the DS-3 service?

d. What is the overhead (number of extra bits) in the DS-4 service?

25. What is the minimum number of bits in a PN sequence if we use FHSS with a

channel bandwidth of B =4 KHz and Bss =100 KHz?

26. An FHSS system uses a 4-bit PN sequence. If the bit rate of the PN is 64 bits per second, answer the following questions:

a. What is the total number of possible hops?

b. What is the time needed to finish a complete cycle of PN?

27. We have a digital medium with a data rate of 10 Mbps. How many 64-kbps voice channels can be carried by this medium if we use DSSS with the Barker sequence?

UNIT 3: CHAPTER 7

TRANSMISSION MEDIA

1. What is the position of the transmission media in the OSI or the Internet model?

2. Name the two major categories of transmission media.

3. How do guided media differ from unguided media?

4. What are the three major classes of guided media?

5. What is the significance of the twisting in twisted-pair cable?

6. What is refraction? What is reflection?

7. What is the purpose of cladding in an optical fiber?

8. Name the advantages of optical fiber over twisted-pair and coaxial cable.

9. How does sky propagation differ from line-of-sight propagation?

10. What is the difference between omnidirectional waves and unidirectional waves?

11. If the power at the beginning of a 1 KIn 2.6/9.5 mm coaxial cable is 200 mw, what is the power at the end for frequencies 1 KHz, 10KHz, and 100 KHz?

12. Calculate the bandwidth of the light for the following wavelength ranges (assume a 8 propagation speed of 2 x 10 m):

a. 1000 to 1200 nm

b. 1000 to 1400 nm

20. A light signal is travelling through a fiber. What is the delay in the signal if the length of the fiber-optic cable is 10 m, 100 m, and 1 Km (assume a propagation 8 speed of 2 x 10 ill)?

21. A beam oflight moves from one medium to another medium with less density. The critical angle is 60°. Do we have refraction or reflection for each of the following incident angles? Show the bending of the light ray in each case.

a. 40°

b. 60°

c. 80

UNIT 3:CHAPTER 8

SWITCHING

I. Describe the need for switching and define a switch.

2. List the three traditional switching methods. What are the most common today?

3. What are the two approaches to packet-switching?

4. Compare and contrast a circuit-switched network and a packet-switched network.

5. What is the role of the address field in a packet traveling through a datagram

network?

6. What is the role of the address field in a packet traveling through a virtual-circuit network?

7. Compare space-division and time-division switches.

8. What is TSI and its role in a time-division switching?

9. Define blocking in a switched network.

10. List four major components of a packet switch and their functions.

11. A path in a digital circuit-switched network has a data rate of I Mbps. The exchange of 1000 bits is required for the setup and teardown phases. The distance between two parties is 5000 km. Answer the following questions if the propagataion speed is 2 X 108 m:

a. What is the total delay if 1000 bits of data are exchanged during the data transfer phase?

b. What is the total delay if 100,000 bits of data are exchanged during the data transfer phase?

c. What is the total delay if 1,000,000 bits of data are exchanged during the data transfer phase?

d. Find the delay per 1000 bits of data for each of the above cases and compare them. What can you infer?

14. We mentioned that two types of networks, datagram and virtual-circuit, need a

routing or switching table to find the output port from which the information belonging to a destination should be sent out, but a circuit-switched network has

no need for such a table. Give the reason for this difference.

above characteristics?

16. The minimum number of columns in a datagram network is two; the minimum number of columns in a virtual-circuit network is four. Can you explain the reason? Is the difference related to the type of addresses carried in the packets of each network?

17. Answer the following questions:

a. Can a routing table in a datagram network have two entries with the same destination address? Explain.

b. Can a switching table in a virtual-circuit network have two entries with the same input port number? With the same output port number? With the same incoming VCls?With the same outgoing VCls?With the same incoming values (port, VCI)? With the same outgoing values (port, VCI)?

18. Consider an n X k crossbar switch with n inputs and k outputs.

a. Can we say that switch acts as a multiplexer if n > k?

b. Can we say that switch acts as a demultiplexer if n < k?

19. We need a three-stage space-division switch with N=100. We use 10 crossbars a the first and third stages and 4 crossbars at the middle stage.

a. Draw the configuration diagram.

b. Calculate the total number of crosspoints.

c. Find the possible number of simultaneous connections.

d. Find the possible number of simultaneous connections if we use one single crossbar (100 x 100).

e. Find the blocking factor, the ratio of the number of connections in c and in d.

20. Redesign the configuration of Exercise 22 using the Clos criteria.

21. We need to have a space-division switch with 1000 inputs and outputs. What is the total number of crosspoints in each of the following cases?

a. Using one single crossbar.

b. Using a multi-stage switch based on the Close criteria

22. We need a three-stage time-space-time switch with N= 100. We use 10 TSIs at the first and third stages and 4 crossbars at the middle stage.

a. Draw the configuration diagram.

b. Calculate the total number of crosspoints.

c. Calculate the total number of memory locations we need for the TSIs.

UNIT 3:CHAPTER 9

USING TELEPHONE AND CABLE NETWORKS

1. What are the three major components of a telephone network?

2. Give some hierarchical switching levels of a telephone network.

3. What is LATA?What are intra-LATA and inter-LATA services?

4. Describe the SS7 service and its relation to the telephone network.

S. What are the two major services provided by telephone companies in the United

States?

6. What is dial-up modem technology? List some of the common modem standards

discussed in this chapter and give their data rates.

7. What is DSL technology?What are the services provided by the telephone companies using DSL? Distinguish between a DSL modem and a DSLAM.

8. Compare and contrast a traditional cable network with a hybrid fiber-coaxial network.

9. How is data transfer achieved using CATV channels?

10. Distinguish between CM and CMTS.

11. Using the discussion of circuit-switching in Chapter 8, explain why this type of

switching was chosen for telephone networks.

12. In Chapter 8, we discussed the three communication phases involved in a circuit-switched network. Match these phases with the phases in a telephone call between two parties.

13. In Chapter 8, we learned that a circuit-switched network needs end-to-end addressing during the setup and teardown phases. Define end-to-end addressing in a telephone network when two parties communicate.

14. When we have an overseas telephone conversation, we sometimes experience a

delay. Can you explain the reason?

15. Draw a barchart to compare the different downloading data rates of common modems.

16. Draw a barchart to compare the different downloading data rates of common DSL technology implementations (use minimum data rates).

17. Calculate the minimum time required to download one million bytes of information using each of the following technologies:

a. V32 modem

b. V32bis modem

c. V90 modem

18. Repeat Exercise 17 using different DSL implementations (consider the minimum rates).

19. Repeat Exercise 17 using a cable modem (consider the minimum rates).

20. What type of topology is used when customers in an area use DSL modems for

data transfer purposes? Explain.

21. What type of topology is used when customers in an area use cable modems for data transfer purposes? Explain.

UNIT 4: CHAPTER 10

DATA LINK LAYER

1. How does a single-bit error differ from a burst error?

2. Discuss the concept of redundancy in error detection and correction.

3. Distinguish between forward error correction versus error correction by retransmission.

4. What is the definition of a linear block code?What is the definition of a cyclic code?

5. What is the Hamming distance? What is the minimum Hamming distance?

6. How is the simple parity check related to the two-dimensional parity check?

7. In CRC, show the relationship between the following entities (size means the number of bits):

a. The size of the dataword and the size of the codeword

b. The size of the divisor and the remainder

c. The degree of the polynomial generator and the size of the divisor

d. The degree of the polynomial generator and the size of the remainder

8. What kind of arithmetic is used to add data items in checksum calculation?

9. What kind of error is undetectable by the checksum?

10. Can the value of a checksum be all Os (in binary)? Defend your answer. Can the value be allIs (in binary)? Defend your answer.

11. What is the maximum effect of a 2-ms burst of noise on data transmitted at the following rates?

a. 1500 bps

b. 12 kbps

c. 100 kbps

d. 100 Mbps

12. Apply the exclusive-or operation on the following pair of patterns (the symbol EB means XOR):

a. (10001) EB (10000)

b. (10001) EB (10001) (What do you infer from the result?)

c. (11100) EB (00000) (What do you infer from the result?)

d. (10011) EEl (11111) (What do you infer from the result?)

13. What is the Hamming distance for each of the following codewords:

a. d (10000, 00000)

b. d (10101, 10000)

c. d (11111,11111)

d. d (000, 000)

14. Find the minimum Hamming distance for the following cases:

a. Detection of two en-ors.

b. Correction of two errors.

c. Detection of 3 errors or correction of 2 errors.

d. Detection of 6 errors or correction of 2 errors.

15. Assuming even parity, find the parity bit for each of the following data units.

a. 1001011

b. 0001100

c. 1000000

d. 1110111

16. Given the dataword 1010011110 and the divisor 10111,

a. Show the generation of the codeword at the sender site (using binary division).

h. Show the checking of the codeword at the receiver site (assume no error)

UNIT 4:CHAPTER 11

DATA LINK CONTROL

1. Briefly describe the services provided by the data link layer.

2. Define framing and the reason for its need.

3. Compare and contrast byte-oriented and bit-oriented protocols. Which category

has been popular in the past (explain the reason)? Which category is popular now

(explain the reason)?

4. Compare and contrast byte-stuffing and bit-stuffing. Which technique is used in

byte-oriented protocols?Which technique is used in bit-oriented protocols?

5. Compare and contrast flow control and error control.

6. What are the two protocols we discussed for noiseless channels in this chapter?

7. What are the three protocols we discussed for noisy channels in this chapter?

8. Explain the reason for moving from the Stop-and-Wait ARQ Protocol to the 00-

Back-NARQ Protocol.

9. Compare and contrast the Go-Back-NARQ Protocol with Selective-RepeatARQ.

10. Compare and contrast HDLC with PPP. Which one is byte-oriented; which one is bit-oriented?

11. Define piggybacking and its usefulness.

12. Which of the protocols described in this chapter utilize pipelining?

UNIT 5:CHAPTER 12

MULTIPLE ACCESS & LANS

1. List three categories of multiple access protocols discussed in this chapter.

2. Define random access and list three protocols in this category.

3. Define controlled access and list three protocols in this category.

4. Define channelization and list three protocols in this category.

5. Explain why collision is an issue in a random access protocol but not in controlled access or channelizing protocols.

6. Compare and contrast a random access protocol with a controlled access protocol.

7. Compare and contrast a random access protocol with a channelizing protocol.

8. Compare and contrast a controlled access protocol with a channelizing protocol.

9. Do we need a multiple access protocol when we use the 1ocalloop of the telephone company to access the Internet? Why?

10. One hundred stations on a pure ALOHA network share a l-Mbps channel. If framesare 1000 bits long, find the throughput if each station is sending 10 frames per second.

UNIT 5:CHAPTER 13

1. How is the preamble field different from the SFD field?

2. What is the purpose of an NIC?

3. What is the difference between a unicast, multicast, and broadcast address?

4. What are the advantages of dividing an Ethernet LAN with a bridge?

5. What is the relationship between a switch and a bridge?

6. Why is there no need for CSMAlCD on a full-duplex Ethernet LAN?

7. Compare the data rates for Standard Ethernet, Fast Ethernet, Gigabit Ethernet, and Ten-Gigabit Ethernet.

8. What are the common Standard Ethernet implementations?

9. What are the common Fast Ethernet implementations?

10. What are the common Gigabit Ethernet implementations?

11. What are the common Ten-Gigabit Ethernet implementations?

12. What is the hexadecimal equivalent of the following Ethernet address?

01011010 00010001 01010101 00011000 10101010 00001111

13. How does the Ethernet address lA:2B:3CAD:5E:6F appear on the line in binary?

14. If an Ethernet destination address is 07:01:02:03:04:05, what is the type of the

address (unicast, multicast, or broadcast)?