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146 Cards in this Set

  • Front
  • Back
In ________ framing, we need a delimiter (flag) to define the boundary of two frames.
variable-size
In _________ protocols, we use ________.
character-oriented; byte stuffing
Flow control mechanisms with sliding windows have control variables at:
Both sender and receiver sites.
_________ enables a receiver to regulate the flow of data from a sender so that the receiver's buffers do not overflow.
Flow control
The time it takes for a station to emit all of the bits of a frame onto the medium is the __________ time.
transmission
A sender send a series of packets to the same destination using 5-bit sequence numbers. If the sequence number starts with 0, what is the sequence number to be used after sending 100 packets?
4
For Stop-and-Wait ARQ, for 10 data packets sent, _______ acknowledgments are needed
exactly 10
If two stations exchange data, each needs to maintain two windows, one for transmit and one for receive, and each side needs to send the data and acknowledgments to the other. To provide efficient support for this requirement a feature known as __________
is typically provided
Piggybacking
In a data link control protocol, _________ control is achieved by retransmission of damaged frames
error
In a Go-Back-N ARQ, if the window size is 63, what is the range of sequence numbers?
0 to 63
In Go-Back-N ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the receive window must be _____
1
In Go-Back-N ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the send window must be _____
31
In Go-Back-N ARQ, if frames 4, 5, and 6 are received successfully, the receiver sends an ACK _______ to the sender.
7
In Selective Repeat ARQ, if 5 is the number of bits for the sequence number, then the maximum size of the receive window must be _____
16
In the _________Protocol, if no acknowledgment for a frame has arrived, we resend all outstanding frames.
Go-Back-N ARQ
In the _____ Protocol, the sender sends one frame, stops until it receives confirmation from the receiver, and then sends the next frame.
Stop-and-Wait
In the Go-Back-N Protocol, if the size of the sequence number field is 8, the sequence numbers are in ________ arithmetic,
modulo-256
Since there is no assurance that the flag field pattern will not appear somewhere inside the HDLC frame, a procedure known as _________ is used to prevent destroying synchronization.
Bit stuffing
The ___________ time is the time it takes for a bit to traverse the link between source and destination.
propagation
The flow control in which the destination can stop the flow of data simply by withholding acknowledgment of the receipt of a frame is ____________ flow control
stop-and-wait
The form of flow control where A and B are connected via a full-duplex link, A maintains a list of sequence numbers that it is allowed to send without receiving any acknowledgment and B maintains a list of sequence numbers that it is prepared to receive is __________ flow control.
sliding-window
HDLC is an acronym for _______.
High-level data link control
According to the PPP transition state diagram exchange of user control and data packets occurs in ____________state.
Open
In modulo-2 arithmetic, we use the ______ operation for both addition and subtraction.
XOR
The ________ between two words is the number of differences between corresponding bits.
Hamming distance
If the Hamming distance between a dataword and the corresponding codeword is three, there are _____ bits in error.
3
The Hamming distance between 100 and 001 is ________.
2
A generator that contains a factor of ____ can detect all odd-numbered errors.
x + 1
In modulo-11 arithmetic, we use only the integers in the range ______, inclusive.
0 to 10
In one's complement arithmetic, if positive 7 is 0111, then negative 7 is ________.
1000
To guarantee correction of up to 5 errors in all cases, the minimum Hamming distance in a block code must be
11
A simple parity-check code can detect __________ errors.
an odd-number of
Checksums use _________ arithmetic.
one's complement arithmetic
What is the maximum effect (maximum number of bits crrupted) of 2 ms burst of noise on data transmitted at 1 Mbps?
2000 bits
In cyclic redundancy checking, what is the CRC?
The remainder
Suppose that we intend to send ASCII-E characters of 8 bits. For that purpose we use a code that can correct one single error. How many bits of redundancy are required?
4
The divisor in a cyclic code is normally called the _________.
generator
We add r redundant bits to each block to make the length n = m + r. The resulting n-bit blocks are called _________.
codewords
A _________ error means that two or more bits in the data unit have changed.
burst
By rearranging the order of bit transmission of the data units, the Hamming code can _____________________________.
correct burst errors
If the data unit is 111101, the divisor 1101, what is the dividend at the transmitter?
111101000
In ________ error correction, the receiver corrects errors without requesting retransmission.
forward
If in certain transmission the message is: 111011101 and the received message is 101011111, then the polynomial that represent E(X), the error, will be:
X7 + X
Calculate the IP Checksum for the following header (given in hexadecimal) F4 F5 F2 03 01 00 F6 F7 00 00.
The check sum will substitute the 00 00 as the check sum. Give the answer in hexadecimal
210E
___________ multiplexing is commonly used for multiplexing digitized voice streams and data streams.
Synchronous time division
________ can be achieved by using multiplexing; ______ can be achieved by using spreading.
Efficiency; privacy and antijamming
Which multiplexing technique transmits digital signals?
TDM
_______ is designed to be used in wireless applications in which stations must be able to share the medium without interception by an eavesdropper and without being subject to jamming from a malicious intruder.
Spread spectrum
In ________ TDM, each input connection has an allotment in the output even if it is not sending data.
synchronous
In a multiplexed system, __ lines share the bandwidth of ____ link.
n; 1
In synchronous TDM, for n signal sources of the same data rate, each frame contains _______ slots.
n
The ___________ accepts the multiplexed data stream, separates the data according to channel, and delivers data to the appropriate output lines.
demultiplexer
The __________ multiplexing is the most heavily used. A familiar example is broadcast and cable television.
frequency division
The _______ technique uses M different carrier frequencies that are modulated by the source signal. At one moment, the sign modulates one carrier frequency; at the next moment, the signal modulates another carrier frequency.
FHSS
The ______ technique expands the bandwidth of a signal by replacing each data bit with n bits.
DSSS
The transmitted data in synchronous TDM are organized into _________ .
frames
Which multiplexing technique involves signals composed of light beams?
WDM
Which multiplexing technique transmits analog signals?
FDM &
WDM

NOT TDM
With __________ , multiplexing time slots are not preassigned to particular data sources. Rather, user data are buffered and transmitted as rapidly as possible using available time slots.
statistical time division
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.
Give the answer in kHz (Kilohertz)
44.5
We need to use synchronous TDM and combine 20 digital sources, each of 100Kbps. 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:
1. What is the size of output frame in bits?
2. What is the output frame rate in frame /sec?
3. What is the duration of an output frame in microseconds?
4. What is the output data rate in Mbps?
5. What is the efficiency of the system (ratio of useful bits to total bits - give result as a percentage)?
1. 21
2. 100000
3. 10
4. 2.1
5. 95.2%
We have 14 sources, each creating 500 8-bit characters per second. Since only some of the 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:
1. What is the size of an output frame in bits?
2. What is the output frame rate (in frames/sec)?
3. What is the duration of an output frame (in milliseconds)?
4. What is the output data rate (in kilobits per seconds)?
1. 72
2. 500
3. 2
4. 36
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:
1. What is the total number of possible hops?
2. What is the time needed to finish a complete cycle of PN?
1. 16
2. 1
________ is the process of converting digital data to a digital signal.
Line coding
PCM is an example of _______ conversion.
analog-to-digital
The Nyquist theorem specifies the minimum sampling rate to be_______.
twice the highest frequency of a signal
The first step in PCM is ________.
sampling
Which of the following quantization level results in a more faithful reproduction of the signal?
32
If the frequency spectrum of a signal has a bandwidth of 300 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to the Nyquist theorem?
1200 samples/s
In _________ transmission, we send bits one after another without start or stop bits or gaps. It is the responsibility of the receiver to group the bits.
synchronous
The ________ rate defines the number of data elements sent in 1s; the ______ rate is the number of signal elements sent in 1s.
data; signal
The minimum bandwidth of Manchester and differential Manchester is ____ that of NRZ.
twice
In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for __________.
synchronization
In _______encoding, we use three levels: positive, zero, and negative.
bipolar
________ is normally referred to as mB/nB coding; it replaces each m-bit group with an n-bit group.
Block coding
________ provides synchronization without increasing the number of bits.
Scrambling
_______ encoding has a transition at the middle of each bit.
RZ
Manchester
Differential Manchester
_______ provides redundancy to ensure synchronization and inherent error detection.
Block coding
Block coding can help in _______ at the receiver.
Synchronization
Error detection
In _______ transmission, a start bit and a stop bit frame a character byte.
asynchronous serial
In _______ transmission, bits are transmitted simultaneously, each across its own wire.
Parallel
In asynchronous transmission, the gap time between bytes is _______.
variable
______ substitutes eight consecutive zeros with 000VB0VB.
B8ZS
Which encoding method uses alternating positive and negative values for 1s?
AMI
In _______ transmission, bits are transmitted over a single wire, one at a time.
asynchronous serial
synchronous serial
Which of the following encoding methods does not provide for synchronization?
NRZ-L
_________ media transport electromagnetic waves without the use of a physical conductor.
Unguided
________ are used for short-range communications such as those between a PC and a peripheral device.
Infrared waves
_____ cable can carry signals of higher frequency ranges than _____ cable.
Coaxial; twisted-pair
A parabolic dish antenna is a(n) _______ antenna.
unidirectional
In a fiber-optic cable, the signal is propagated along the inner core by _______.
reflection
Radio waves are _________.
omnidirectional
Signals with a frequency above 30 MHz use _______propagation.
line-of-sight
Transmission media lie below the _______ layer.
physical
What is the major factor that makes coaxial cable less susceptible to noise than twisted-pair cable?
outer conductor
What is the time between samples for a voice channel using PCM? Give the answer in microseconds.
Hint: Use the Nyquist sampling theorem on a 4 KHz voice channel
125
Data can be ________.
analog
digital
_______ data are continuous and take continuous values.
analog
_______ data have discrete states and take discrete values.
Digital
A periodic signal completes one cycle in 0.01 s. What is the frequency?
100 Hz
As frequency increases, the period ________.
decreases
A signal is measured at two different points. The power is P1 at the first point and P2 at the second point. The dB is 0. This means ________.
P2 equals P1
A sine wave in the ______ domain can be represented by one single spike in the _____ domain.
time; frequency
A sine wave is ________.
periodic and continuous
Before data can be transmitted, they must be transformed to ________.
electromagnetic signals
For a ______ channel, the Nyquist bit rate formula defines the theoretical maximum bit rate.
noiseless
For a ______ channel, we need to use the Shannon capacity to find the maximum bit rate.
noisy
Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is ________ that of A.
twice
If the bandwidth of a signal is 15 KHz and the lowest frequency is 52 KHz, what is the highest frequency?
67 KHz
If the maximum amplitude of a sine wave is 2 V, the minimum amplitude is ________ V.
-2
In a frequency-domain plot, the horizontal axis measures the ________.
frequency
What is the bandwidth of a signal that ranges from 10 MHz to 45 MHz?
35 MHz
In a time-domain plot, the horizontal axis is a measure of ________.
time
The _________ product defines the number of bits that can fill the link.
bandwidth-delay
________ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal.
Noise
________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium.
Attenuation
________ is a type of transmission impairment in which the signal loses strength due to the different propagation speeds of each frequency that makes up the signal.
Distortion
The _____ of a composite signal is the difference between the highest and the lowest frequencies contained in that signal.
bandwidth
_______ describes the position of the waveform relative to time 0.
Phase
Baseband transmission of a digital signal is possible only if we have a ____ channel.
low-pass
When propagation speed is multiplied by propagation time, we get the ________.
distance a signal or bit has traveled
A ________________ connection provides a dedicated link between two devices.
point-to-point
One of the primary disadvantages in a ___________________ topology is that one break in the cable media can stop all data transmissions on the network segment.
Bus
The ______________________ is the physical path over which a message travels.
medium
As the data packet moves from the upper to the lower layers, headers are _______.
Added
In the OSI model, as a data packet moves from the lower to the upper layers, headers are _______.
removed
In the OSI model, encryption and decryption are functions of the ________ layer.
presentation
In the OSI model, what is the main function of the transport layer?
process-to-process message delivery
In the OSI model, when data is transmitted from device A to device B, the header from A's layer 5 is read by B's _______ layer.
session
The ________ address, also known as the link address, is the address of a node as defined by its LAN or WAN.
physical
The _______ layer changes bits into electromagnetic signals.
Physical
The _______ layer lies between the network layer and the application layer.
Transport
The ______ layer adds a header to the packet coming from the upper layer that includes the logical addresses of the sender and receiver.
network
The ______ layer is responsible for moving frames from one hop (node) to the next.
data link
The Internet model consists of _______ layers.
Five
The Internetworking Protocol (IP) is a ________ protocol.
NOT reliable
NOT connection-oriented
*none of the above*
The OSI model consists of _______ layers.
seven
The physical layer is concerned with the movement of _______ over the physical medium.
bits
The process-to-process delivery of the entire message is the responsibility of the _______ layer.
Transport
To deliver a message to the correct application program running on a host, the _______ address must be consulted.
port
When a host on network A sends a message to a host on network B, which address does the router look at?
logical
When data are transmitted from device A to device B, the header from A's layer 4 is read by B's _______ layer.
Transport
Which of the following is an application layer service?
Remote log-in
File transfer and access
Mail service
Why was the OSI model developed?
Standards were needed to allow any two systems to communicate
A port address in TCP/IP is ______ bits long.
16
Ethernet uses a ______ physical address that is imprinted on the network interface card (NIC).
6-byte