Chapter 4 Multiple Choice Questions

______________ 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

a. Hamming code

_____________ 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

a. Shielding wires

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

a. a receiver that detects an error in a message simply asks the sender to retransmit the message until it is received without error

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

a. about 50% for either even or odd parity

On digital circuits, we use _________ to increase the strength of the signal and prevent attenuation. a. amplifiers b. repeaters c. multiplexers d. digitizers e. modems

a. amplifiers

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

a. burst error

Which of the following is way to reduce or eliminate crosstalk on a circuit, a. changing multiplexing techniques b. adding repeaters or amplifiers to a circuit c. reducing the length of the cable d. adding fluorescent lights e. shorting a circuit

a. changing multiplexing techniques

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

a. computers wait until the circuit is free before they send data

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)

a. continuous

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

a. fiber optic cable

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

a. information bits

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. jitter e. harmonic distortion

a. intermodulation noise

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

a. is not very important in point-to-point with full duplex configuration

Which of the following is true about the data link protocol, PPP? a. it is a byte-oriented protocol b. it is a bit-oriented protocol c. it uses block check characters for error detection d. it is a byte-count oriented protocol e. it uses parity bits for error detection

a. it is a byte-oriented protocol

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

a. occurs when one circuit picks up signals in another

In a dial-up network: a. the error rate will vary because the circuits will change with each dial-up b. the network is less prone to errors than private dedicated lines c. users might try to transmit the data at a higher speed to decrease the error rate d. constant transmission conditions will always create a constant error rate e. users might try to transmit the data at a lower speed to speed up the data transmission

a. the error rate will vary because the circuits will change with each dial-up

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

a. work better than contention approaches for small networks that have low usage

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

b. 00011011

Which of the following is not a controlled access method of media access control? a. Token access b. CSMA/CD c. polling d. roll call polling e. hub polling

b. CSMA/CD

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 getting a message from one computer to another (one node to another) without errors. c. It accepts messages from the physical layer. d. It performs routing functions. e. It organizes data from the physical layer and passes these coherent messages to the application layer.

b. It is responsible for getting a message from one computer to another (one node to another) without errors.

Which of the following is not a type of synchronous data link protocol? a. SDLC b. KERMIT c. PPP d. HDLC e. Ethernet (IEEE 802.3)

b. KERMIT

Which of the following is not a type of asynchronous file transfer protocol? a. XMODEM-CRC b. OSCAR c. XMODEM d. XMODEM-1K e. ZMODEM

b. OSCAR

________ 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

b. Polling

TRIB, an acronym that relates to throughput, stands for: a. Throughput Reduction of Information Barriers b. Transmission Rate of Information Bits c. Throughput Rate of Iso-synchronous Bytes d. Transmission Regulation for Inverse-multiplexing Bands e. Trellis-coded Regulation of Information Bits

b. Transmission Rate of Information Bits

A phase hit is likely to be: a. spikes b. a short term shift out of phase c. intermodulation noise d. white noise e. Gaussian noise

b. a short term shift out of phase

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

b. because of noise on the line

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

b. complex because many factors affect throughput

When a signal is reflected back to the transmitting equipment, it is called a(n) _________. a. jitter b. echo c. crosstalk d. attenuation e. impulse noise

b. echo

Another term for impulse noise is: a. Gaussian noise b. spikes c. attenuation d. cross-talk e. intermodulation noise

b. spikes

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%

c. 50%

_____________ 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

c. Adding repeaters or amplifiers to a circuit

____________ 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 f. 802.11g

c. Amplitude shift keying

__________can obliterate a group of bits, causing a burst error. a. Crosstalk b. Attenuation c. Impulse noise d. Intermodulation noise e. Jitter

c. Impulse noise

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 is a byte-count-oriented protocol 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 e. It does not have a problem with transparency

c. It uses a special bit pattern called a flag at the beginning and end of every frame (or packet)

The loss of power a signal suffers as it travels from the transmitting computer to a receiving computer is: a. jitter b. spiking c. attenuation d. intermodulation noise e. echo

c. attenuation

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

c. is sent by the recipient if the message contains an error

The primary source of error in data communications is: a. echoes b. intermodulation noise c. spikes d. jitter e. cross-talk

c. spikes

____________ 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

d. Flipped bits

Stop-and-wait ARQ uses ___________ type of data flow. a. full simplex b. half complex c. full duplex d. half duplex e. full complex

d. half duplex

Which of the following is true about the data link protocol, Ethernet (IEEE 802.3)? a. it is a byte-oriented protocol b. it is a bit-oriented protocol c. it uses block check characters for error detection d. it is a byte-count oriented protocol e. it uses parity bits for error detection

d. it is a byte-count oriented protocol

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

d. less likely to suffer from noise than electrical media

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. polynomial checking

d. pulse code checking

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

d. stop and wait

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%

e. > 99%

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 front-end processor or server has to wait for a response from the polled client or terminal.

e. It typically involves some waiting because the front-end processor or server has to wait for a response from the polled client or terminal.

_________________ 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

e. Transmission efficiency

When the output signal from an amplifier on a circuit is different from the input signal, this is called _________________. a. intermodulation noise b. attenuation c. echo d. jitter e. harmonic distortion

e. harmonic distortion

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. is also known as start-stop transmission

e. is also known as start-stop transmission

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

e. is used to transmit a "frame" or "packet" of data at a time

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

e. the physical and the network layers

The familiar background static on radios and telephones is called: a. echoes b. intermodulation noise c. line outages d. cross-talk e. white noise

e. white noise