Deck 4: Data Link Layer

Question 1

The physical and data link layers of wired Ethernet have been refined over the years as a collection of standards under the IEEE 802.3 workgroup.

Answer 1

True

Question 2

Attenuation refers to the loss of signal strength.

Answer 2

True

Question 3

When the signals from two circuits combine to form a new signal that falls into a frequency band reserved for another signal, this is called intermodulation noise.

Answer 3

True

Question 4

With contention, a computer does not have to wait before it can transmit.A computer can transmit at anytime.

Question 5

With roll-call polling, a server polls clients in a consecutive, pre-arranged priority list.

Question 6

Contention is commonly used with Ethernet local area networks.

Question 7

Impulse noise is caused by the thermal agitation of electrons.

Question 8

Gaussian noise is a special type of attenuation.

Question 9

Crosstalk occurs when the signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

Question 10

Undesirable stray electrical voltage can cause data communication errors.

Question 11

The two categories of network errors are: lost data and delimited data.

Question 12

Media access controls refer to the need to control when computers transmit.

Question 13

Most computer networks managed by a host mainframe computer use contention media access control.

Question 14

Polling is the process of permitting all clients to transmit or receive at any time.

Question 15

Controlled access MAC approaches work better in a large network with high usage.

Question 16

Token passing is a term that refers to hub polling, in which one computer starts a poll and passes it to the next computer on a multipoint circuit.

Question 17

Data transmission errors are typically uniformly distributed in time.

Question 18

Only the sender of a data transmission needs to be concerned about the rules or protocols that govern how it communicates with the receiver.

Question 19

The data link layer accepts messages from the network layer and controls the hardware that transmits them.

Question 20

If a computer transmits a message containing "ABC" and the destination computer receives "abc" as the message, the message is corrupted.

Question 21

Overhead bits are used for error checking and marking the start and end of characters and packets.

Question 22

____________ is not a function of a data link protocol.

A)Media access control
B)Message delineation
C)Amplitude shift keying
D)Indicating when a message starts and stops
E)Error control

Question 23

One type of forward error correction is the Hamming code.

Question 24

Forward error correction is commonly used in satellite transmission.

Question 25

Cyclical redundancy check is one of the most popular polynomial error-checking schemes.

Question 26

The distance between repeaters or amplifiers on a telephone circuit is determined by the amount of power gained per unit length of the transmission.

Question 27

Which of the following is true about roll call polling?

A)It can not be modified to increase priority of clients or terminals.
B)It does not require a server or host or special device that performs the polling.
C)It is also called token passing.
D)It is a type of contention approach to media access control.
E)It typically involves some waiting because the server has to wait for a response from the polled client or terminal.

Question 28

Parity checking can only detect an error when an even number of bits are switched.

Question 29

In an odd parity-checking scheme, the parity bit is set to make the total number of ones in the byte including the parity bit) an even number.

Question 30

When we amplify the signal on an analog circuit, we also amplify any noise that is present on the circuit.

Question 31

For effective error detection and correction, extra error detection "data" must be included with each message

Question 32

The simplest method for error correction is retransmission.

Question 33

Media access control:

A)is not very important in point-to-point with full duplex configuration
B)is not very important in local area networks
C)is not very important in a point-to-point with a half duplex configuration
D)is not very important in a multipoint configuration
E)does not control when computers transmit

Question 34

Which of the following is true with respect to the data link layer?

A)It accepts streams of bits from the application layer.
B)It is responsible for encoding the bit-stream as a series of electronic voltages.
C)It performs error detection.
D)It performs routing functions.
E)It organizes data from the physical layer and passes these coherent messages directly to the application layer.

Question 35

Transmission efficiency refers to the percentage of bits transmitted without errors.

Question 36

________ is the process of sending a signal to a client that gives its permission to transmit or asks it to receive.

A)Contention
B)Polling
C)Pooling
D)Carrier sense
E)CRC

Question 37

Another term for continuous ARQ is sliding window.

Question 38

HDLC is very similar to the SDLC synchronous data link protocol.

Question 39

Which of the following is not a controlled access method of media access control?

A)Token passing
B)CSMA/CD
C)polling
D)roll call polling
E)hub polling

Question 40

As part of the five-layer network model used in this textbook, the data link layer sits directly between:

A)the physical and the application layers
B)the network and the application layers
C)the network and transport layers
D)the physical and the application layers
E)the physical and the network layers

Question 41

Optical media is:

A)more likely to suffer from noise than electrical media
B)has about the same likelihood of suffering from noise as electrical media
C)has about the same likelihood of suffering from noise as coaxial cable
D)less likely to suffer from noise than electrical media
E)more prone to noise than twisted pair media

Question 42

When a signal is reflected back to the transmitting equipment, it is called an) _________.

A)white noise
B)echo
C)crosstalk
D)attenuation
E)impulse noise

Question 43

The loss of power a signal suffers as it travels from the transmitting computer to a receiving computer is:

A)white noise
B)spiking
C)attenuation
D)intermodulation noise
E)echo

Question 44

The two sublayers of the data link layer consist of the media access control sublayer and the________ .

A)logical link control sublayer
B)network control sublayer
C)session sublayer
D)physical sublayer
E)transport sublayer

Question 45

Which of the following is way to reduce or eliminate crosstalk on a circuit?

A)physically separating the cables from other communication cables
B)adding repeaters or amplifiers to a circuit
C)reducing the length of the cable
D)adding fluorescent lights
E)shorting a circuit

Question 46

If a signal with a frequency of 500 MHz combines with a another signal of 1500 MHz and they form a new signal of 2000 MHz; this is an example of:

A)intermodulation noise
B)attenuation
C)echo
D)white noise
E)cross-talk

Question 47

Another term for impulse noise is:

A)Gaussian noise
B)spikes
C)attenuation
D)cross-talk
E)intermodulation noise

Question 48

Which of the following media is least susceptible to noise?

A)fiber optic cable
B)coaxial cable
C)twisted pair
D)unshielded twisted pair
E)shielded twisted pair

Question 49

The familiar background static on radios and telephones is called:

A)echoes
B)intermodulation noise
C)impulse noise
D)cross-talk
E)white noise

Question 50

____________ refers to bits that have been changed, in error, from 1 to 0, or vice versa, in a data transmission.

A)Contracted bits
B)Polled bits
C)Inverse multiplexed bits
D)Flipped bits
E)Bit delineation

Question 51

Errors on a network can occur:

A)only on dial-up type of circuits
B)because of noise on the line
C)only on poorly maintained networks
D)only due to Gaussian noise
E)only due to lightning strikes

Question 52

With contention:

A)computers wait until the circuit is free before they send data
B)the server or front end processor works consecutively through a list of clients to determine who should have access to the media
C)the front end processor must wait for a response from the polled client or terminal
D)one computer starts the poll and passes it to the next computer on the multipoint circuit
E)there is never a chance for "collision," or two computers trying to send data at the same time

Question 53

In a _________ , more than one data bit is changed by the error-causing condition.

A)burst error
B)data rate shift
C)Trellis-coded modulation
D)uniform distribution
E) amplitude key shift

Question 54

Cross-talk:

A)occurs when one circuit picks up signals in another
B)is always bothersome because it has a high signal strength
C)decreases with increased proximity of two wires
D)decreases during wet or damp weather
E)increases with lower frequency signals

Question 55

On digital circuits, we use _________ to reshape the incoming signal and prevent attenuation.

A)amplifiers
B)repeaters
C)multiplexers
D)digitizers
E)modems

Question 56

__________can obliterate a group of bits, causing a burst error.

A)Cross-talk
B)Attenuation
C)Impulse noise
D)Intermodulation noise
E)White noise

Question 57

_____________ is an effective way to prevent attenuation.

A)Shielding wires
B)Adding fluorescent lights
C)Adding repeaters or amplifiers to a circuit
D)Changing multiplexing techniques
E)Shorting a circuit

Question 58

The primary source of error in data communications is:

A)echoes
B)intermodulation noise
C)spikes
D)attenuation
E)cross-talk

Question 59

In general, controlled approaches:

A)work better than contention approaches for small networks that have low usage
B)work better than contention approaches for large networks that have high usage
C)work better than contention approaches for all sizes of networks
D)do not require a host, server, or active monitor to assign media access control
E)have many collisions

Question 60

_____________ is an effective way to prevent impulse noise, cross talk, and intermodulation noise.

A)Shielding wires
B)Adding fluorescent lights
C)Adding repeaters to a circuit
D)Adding amplifiers to a circuit
E)Shorting a circuit

Question 61

In communication protocols, _________ are used to convey the user's meaning.

A)information bits
B)overhead bits
C)stop bits
D)start bits
E)flag bits

Question 62

In ARQ, a NAK:

A)is sent by the recipient if the message was received without error
B)is sent by the sender at the same time as it sends a data packet
C)is sent by the recipient if the message contains an error
D)refers to non-asynchronous Kermit technique
E)means that the sender should continue with sending the next message

Question 63

Synchronous transmission:

A)cannot be used on multipoint circuits
B)is used to send one character at a time
C)uses start bits before each character to be sent
D)uses stop bits after each character to be sent
E)is used to transmit a "frame" or "packet" of data at a time

Question 64

Using parity, the probability for detecting an error, given that one has occurred, is:

A)about 50% for either even or odd parity
B)about 70% for even parity and 30% for odd parity
C)about 30% for even parity and 70% for odd parity
D)about 0% for either even or odd parity
E)about 100% for either even or odd parity

Question 65

With __________ ARQ, the sender immediately sends the next message or packet of data.

A)continuous
B)immediate
C)open window
D)stop-and-wait
E)halt and be recognized HBR)

Question 66

With __________ ARQ, the sender pauses for a response from the receiver to alter each message or packet of data.

A)open window
B)halt and be recognized HBR)
C)sliding window
D)stop and wait
E)continuous

Question 67

Which of the following is true about the data link protocol, PPP?

A)it is commonly used in WANs
B)it is a bit-oriented protocol
C)it uses block check characters for error detection
D)it was developed in the 1960s
E)it uses parity bits for error detection

Question 68

________ has essentially replaced SDLC and offers a larger sliding window.

A)Ethernet
B)PPP
C)Asynchronous transmission
D)HDLC
E)full complex

Question 69

Calculating the actual throughput of a data communication network is:

A)not normally required for synchronous networks because they are so fast
B)complex because many factors affect throughput
C)simple because packet size is the primary factor affecting throughput
D)not needed for satellite-based networks
E)far less complicated if the system operates on a contention basis

Question 70

Which of the following is not an error detection method used in the data link layer?

A)parity checking
B)cyclic redundancy checking
C)CRC-32
D)pulse code checking
E)odd parity

Question 71

_________________ is defined as the total number of information bits divided by the total number of bits in the transmission.

A)Asynchronous rate
B)Protocol percentage
C)Throughput
D)Transmission Rate of Information Bits
E)Transmission efficiency

Question 72

______________ controls errors by detecting and correcting them at the receiving end without retransmission of the original message.

A)Hamming code
B)Huffman encoding
C)Front end processing
D)Wave division multiplexing
E)Hub polling

Question 73

The probability of detecting an error, given that one has occurred, using parity checking is about:

A)100%
B)0%
C)50%
D)75%
E)98%

Question 74

Which of the following is true about the data link protocol, SDLC:

A)It is a client-server protocol developed by Compaq in 1996.
B)It transmits each character independently of one another and includes start and stop bits for each character sent.
C)It uses a special bit pattern called a flag at the beginning and end of every frame or packet).
D)It uses a contention media access control protocol and is used in most LANs today.
E)It does not have any error detection capabilities.

Question 75

The probability of detecting an error, provided that one has occurred, using cyclic redundancy checking is about:

A)75%
B)0%
C)exactly 100%
D)50%
E)> 99%

Question 76

ARQ means that:

A)a receiver that detects an error in a message simply asks the sender to retransmit the message until it is received without error
B)the common carrier Automatically Returns Queries to the subscriber upon receipt of such queries
C)a sender is using a data link protocol called Asynchronous Repeating reQuest
D)a fiber optic cable meets the American Registered Quality, a certification standard for use in high-quality data communication transmission lines
E)a sender is using a parity scheme called Array Resource Quality

Question 77

Which of the following is true about the data link protocol, Ethernet IEEE 802.3)?

A)it is not very popular
B)it is a bit-oriented protocol
C)it uses block check characters for error detection
D)newer version permits jumbo frames
E)it uses parity bits for error detection

Question 78

Which of the following is not a type of synchronous protocol?

A)SDLC
B)VT100
C)HDLC
D)Ethernet
E)PPP

Question 79

With odd parity assume that the parity bit in bold) has been placed at the end of each of the following) and a 7-bit ASCII code, which of the following is incorrect?

A)01101011
B)00011011
C)00100101
D)10110110
E)11111110

Question 80

Asynchronous transmission:

A)is used to transmit each character simultaneously with all other characters
B)has a pre-determined, fixed time between sending characters
C)is typically used on multipoint half duplex circuits
D)uses a continuous series of start bits as an idle signal
E)each character is transmitted independently of all other characters