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50 Cards in this Set

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



T or F

T

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




T or F

T

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




T or F

T

UDP always delivers messages in order




T or F

F

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



T or F

F

Clients identify a server machine by its IP address



T or F

T

Concurrent servers use a separate thread of control for each client




T or F

T

The server port number identifies an application running on the server




T or F

T

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




T or F

F

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




T or F

F

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




T or F

T

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




T or F

T

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




T or F

T

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




T or F

F

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




T or F

T

The Hamming distance for the strings 1001 and 0011 is 2




T or F

T

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




T or F

T

A RAC matrix can correct any single bit error




T or F

T

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




T or F

F

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




T or F

T

Built on TCP



stream or message

Stream

Used for video conferencing



stream or message

Message

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



place these 4 protocol headers in the correct order

Ethernet|IP|TCP|HTTP

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)

P, N_I, I, T, A

Name the layer that contains each protocol: TCP___


IP____


FTP___

transport


Internet


application

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

physical

modulation method in which signal strength is varied to send data

amplitude

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

TDM

multiplexing method where light waves are sent across optical fiber

wave division

uses a single wire and a metal shield



twisted pair, coaxial cable, fiber

coaxial cable

capable of the highest data rates



twisted pair, coaxial cable, fiber

fiber

CAT 5E is a category of this wire



twisted pair, coaxial cable, fiber

twisted pair

immune to electrical noise



twisted pair, coaxial cable, fiber

fiber

what two characteristics are of a signal are varied in QAM

amplitude and phase

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



how many bits does a single point represent?

256




8 since 28 =256

in HFC, fiber is used in the feeder circuit:



trunk or home

trunk

a head-end modem belongs to a



CMTS or DOCSIS or customer

CMTS

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



1 2 4 8

4

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



1 3 4 5

3

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



3 6 12 48

6

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



1 2 3 4

3

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



1 2 4 8

8

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.

D=2x8000xlog24=32,000 bits/sec

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.

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)

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

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

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.

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

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?

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).

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?

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.

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


1. 10000001 10000000

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

1 1 0 0


0 0 1 1


1 1 1 1