Cosc 350 - Exam 1

Front 1

Protocols can specify message headers or actions to take if a message is lost

T or F

Back 1

T

Front 2

A layer at the receiver hands packets to the layer above after removing the relevant header

T or F

Back 2

T

Front 3

In the OSI 7-layer model, layer 3 is the network layer

T or F

Back 3

T

Front 4

UDP always delivers messages in order

T or F

Back 4

F

Front 5

The last step in a connection-oriented mechanism such as TCP is to send data

T or F

Back 5

F

Front 6

Clients identify a server machine by its IP address

T or F

Back 6

T

Front 7

Concurrent servers use a separate thread of control for each client

T or F

Back 7

T

Front 8

The server port number identifies an application running on the server

T or F

Back 8

T

Front 9

When a browser connects to a server, a DNS request provides the server’s MAC address

T or F

Back 9

F

Front 10

The 16-bit Internet checksum is computed using 2s complement arithmetic

T or F

Back 10

F

Front 11

For the CRC polynomial x16+x12+x5+1, the total number of bits in the CRC is 16

T or F

Back 11

T

Front 12

A CRC of high degree used in real systems can detect most burst errors

T or F

Back 12

T

Front 13

If the maximum number of detectable errors is 6, the minimum Hamming distance dmin=7

T or F

Back 13

T

Front 14

For a (10, 5) encoding scheme, the number of data bits is 10

T or F

Back 14

F

Front 15

For a (10, 5) encoding scheme, the code rate is 1/2

T or F

Back 15

T

Front 16

The Hamming distance for the strings 1001 and 0011 is 2

T or F

Back 16

T

Front 17

If 11000101 à 10001101, the length of the burst error is 4

T or F

Back 17

T

Front 18

A RAC matrix can correct any single bit error

T or F

Back 18

T

Front 19

A SONET frame on an STS-3 circuit is transferred in 3*125 μseconds

T or F

Back 19

F

Front 20

ADSL selects frequencies and modulation techniques to adapt to line quality:

T or F

Back 20

T

Front 21

Built on TCP

stream or message

Back 21

Stream

Front 22

Used for video conferencing

stream or message

Back 22

Message

Front 23

Packets captured by Wireshark when running a browser include TCP, Ethernet, IP, and HTTP headers

place these 4 protocol headers in the correct order

Back 23

Ethernet|IP|TCP|HTTP

Front 24

List these 5 layers in order with the lowest layer first and highest layer last:

TCP/IP model layers are Internet (I), Transport (T), Application (A), Physical (P), Network_Interface (N_I)

Back 24

P, N_I, I, T, A

Front 25

Name the layer that contains each protocol: TCP___

IP____

FTP___

Back 25

transport

Internet

application

Front 26

Name the layer that specifies low-level details such as modulation, frequencies and voltages

Back 26

physical

Front 27

modulation method in which signal strength is varied to send data

Back 27

amplitude

Front 28

multiplexing method where sources take turns and a slot is unfilled if its source has not data

Back 28

TDM

Front 29

multiplexing method where light waves are sent across optical fiber

Back 29

wave division

Front 30

uses a single wire and a metal shield

twisted pair, coaxial cable, fiber

Back 30

coaxial cable

Front 31

capable of the highest data rates

twisted pair, coaxial cable, fiber

Back 31

fiber

Front 32

CAT 5E is a category of this wire

twisted pair, coaxial cable, fiber

Back 32

twisted pair

Front 33

immune to electrical noise

twisted pair, coaxial cable, fiber

Back 33

fiber

Front 34

what two characteristics are of a signal are varied in QAM

Back 34

amplitude and phase

Front 35

in 256QAM, how many points are in the constellation diagram?

how many bits does a single point represent?

Back 35

256

8 since 28 =256

Front 36

in HFC, fiber is used in the feeder circuit:

trunk or home

Back 36

trunk

Front 37

a head-end modem belongs to a

CMTS or DOCSIS or customer

Back 37

CMTS

Front 38

In phase shift modulation, to send 2 bits per shift, the total number of shifts is:

1 2 4 8

Back 38

4

Front 39

If max and min frequencies of a signal are 4 KHz and 1 KHz, its bandwidth in KHz is:

1 3 4 5

Back 39

3

Front 40

If a system operates at 3000 baud and uses 4 signal levels, the bit rate in Kbps is:

3 6 12 48

Back 40

6

Front 41

An 8-PSK mechanism has x times the data rate of a 2-PSK mechanism, where x=

1 2 3 4

Back 41

3

Front 42

The number of signal levels in a 1000-baud system that sends at 3000 bits/s is:

1 2 4 8

Back 42

8

Front 43

If a transmission system has bandwidth B=8000 Hz and uses 4 values of voltage, find the maximum data rate in bits per second using the Nyquist formula D=2B log2 K, where D is the maximum data rate in bits per second and K is the number of values of voltage.

Back 43

D=2x8000xlog24=32,000 bits/sec

Front 44

If a transmission system has bandwidth B = 5000 Hz and an S/N ratio equivalent to 20 dB, find the maximum data rate C in bits per second using the Shannon formula C = B log2 (1+S/N), where the S/N ratio is equivalent to 10 log10 S/N in dB.

Back 44

10xlog10S/N=20 à log10S/N=2 àS/N=100

C=5000xlog2(1+100)=5000xlog2101, which is less than 35,000 bits/sec (33291 bits/sec)

Front 45

How many milliseconds does it take to send a 10 Megabyte file at 100 Mbps?

Back 45

((10x106x8)/(100x106))x103=800 ms (could also use 1 MB= 220 bytes to get = 838.9 ms)

Front 46

A satellite is 1500 km above the earth’s surface. How many milliseconds does it take for a signal to travel from the satellite to the user? The speed of light is 3x108 meters/s.

Back 46

((1500x103)/(3x108))x103=5 ms

Front 47

In CDM, suppose the A’s chip sequence is (0, 1) and B’s chip sequence is (1, 0). If A sends 1 and B sends 0, what is the value computed by C to receive A’s data?

Back 47

Received signal is (-1, 1)1+(1,-1)-1=(-2, 2). To recover the bit sent, C computes (-2, 2)*(-1, 1)=2+2=4. Since 4>0, the bit sent is a 1 (positive value interpreted as a 1 as on p. 193-194).

Front 48

The PCM voice standard uses 8000 samples/s. If 16 bits per sample are used, into how many levels is the range of the signal divided, and at what rate is data generated for a call?

Back 48

16 bits have 216 possible values, which is the number of levels. The data rate is: 8000 samples/s * 16 bits/sample = 128, 000 bits/s = 128 kbps.

Front 49

Given the two bytes 10000000 (MSByte) and 10000001 (LSByte), assume the leftmost bit in each byte is MSbit and the rightmost bit in each byte is LSbit.

1. 10000001 10000000 2. 10000001 00000001

3. 10000000 10000001 4. 00000001 10000001

Back 49

1. 10000001 10000000

Front 50

Generate a RAC parity matrix for a (12, 6) coding of the dataword 110001 (arrange dataword in 2 rows).

Back 50

1 1 0 0

0 0 1 1

1 1 1 1