Test 2 Data Communications Chapter 4 Quiz

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

transmission efficiency

Background static on radios and telephones is called:

white noise

Using odd parity (the parity bit is illustrated in bold) with a 7-bit ASCII code, which of the following is incorrect? 01101011 00011011 10110101 00100101

00011011

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

50%

_____ is an effective way to prevent attenuation.

Adding repeaters or amplifiers to a circuit

Which of the following is not a controlled access method of media access control? (a)polling (b)token passing (c)CSMA/CD (d)hub rolling

CSMA/CD

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

False

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

False

__________ refers to bits that have been changed from 1 to 0, or vice versa, during data transmission between sender and receiver.

Flipped bits

An example of _______ is when a signal with a frequency of 500 MHz combines with another signal of 1500 MHz and they form a new signal of 2000 MHz.

Intermodulation noise

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

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

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

True

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

True

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

True

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

True

ARQ means that:

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

Which of the following is a data link layer error detection method? (a)parity checking (b)cyclic redundancy checking (c)checksums

all of the above

Which of the following is not a function of a data link protocol? (a)message delineation (b)error control (c)media access control (d)amplitude shift keying

amplitude shift keying

With contention:

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

The most common source of data communications errors is/are _____.

impulse noise

In the textbook's five layer model, the data link layer sits between the:

network and physical

Given that one has occurred, the probability of detecting an error using cyclic redundancy checking is:

over 99%

_____ is the process of sending a signal to a client that gives it permissiion to transmit or asks it to receive.

polling

On digital circuits, ______ are used to reshape the incoming signal and prevent attenuation.

repeaters

The most common cause of burst errors is _____.

spikes