Deck 6: Errors, Error Detection, and Error Control

Question 1

In a stop-and-wait error control system,a receiver may acknowledge multiple packets with a single ACK.

Answer 1

False

Question 2

The CRC method catches almost 100% of errors.

Answer 2

True

Question 3

Because white noise is relatively continuous,it can be reduced significantly but never completely eliminated.

Answer 3

True

Question 4

Sliding window protocols have been around since the 1970s.

Question 5

Telephone signal crosstalk was a more common problem before telephone companies used fiber-optic cables and other well-shielded wires.

Question 6

Simple parity can detect only an even number of erroneous bits per character.

Question 7

White noise is dependent on the temperature of the medium.

Question 8

If the impulse spike interferes with an analog signal,removing it without affecting the original signal is extremely easy.

Question 9

Echo error rarely occurs at junctions where wires are connected.

Question 10

Noise is a problem for both analog and digital signals.

Question 11

An unfortunate side effect of noise during a transmission is that the transmitting station has to slow down its transmission rate.

Question 12

If impulse noise interferes with a digital signal,often the original digital signal cannot be recognized and recovered.

Question 13

When a parity bit is assigned to ASCII,the Hamming distance becomes 4.

Question 14

The CRC error-detection method treats the packet of data to be transmitted as a large polynomial.

Question 15

Attenuation can be eliminated with the use of repeaters for analog systems.

Question 16

If jitter becomes too great,correcting it can require the transmitting devices to speed up their transmission rates.

Question 17

Installing special filters for analog signals and digital signal regeneration for digital signals helps in preventing white noise.

Question 18

TCP performs error detection at the end points of the connection.

Question 19

Returning a message was one of the first error-control techniques developed.

Question 20

NAK represents a positive acknowledgment.

Question 21

Typically,impulse noise is a(n)____ burst of energy.

A) digital
B) analog
C) binary
D) logical

Question 22

Twisted pair Category 5e/6 cable should not be longer than the recommended 100-meter (300-foot)distance when it's transmitting at ____ Mbps.

A) 100
B) 250
C) 500
D) 1000

Question 23

Longitudinal parity is sometimes called longitudinal redundancy check or ____ parity.

A) vertical
B) horizontal
C) random
D) binary

Question 24

The most basic error-detection techniques are parity checks,which are used with ____ connections.

A) synchronous
B) asynchronous
C) statistical
D) fiber-optic

Question 25

Impulse noise is also known as ____.

A) noise spike
B) jitter
C) attenuation
D) crosstalk

Question 26

Causes of jitter can include electromagnetic interference,____,passing the signal through too many repeaters,and the use of lower-quality equipment.

A) coding
B) sampling
C) compression
D) crosstalk

Question 27

Isolated single-bit errors occur ____ percent of the time.

A) 30 to 40
B) 40 to 50
C) 50 to 60
D) 60 to 70

Question 28

____ is not necessarily a form of error,but can indirectly lead to an increase in errors affecting the transmitted signal.

A) Impulse noise
B) Crosstalk
C) Attenuation
D) White noise

Question 29

High humidity and wet weather can cause an increase in electrical ____ over a telephone system.

A) compression
B) attenuation
C) jitter
D) crosstalk

Question 30

White noise is also called thermal noise or ____ noise.

A) crosstalk
B) jitter
C) Gaussian
D) spike

Question 31

Error detection can be performed in several places within a communications model.One of the most common places is the TCP/IP ____ layer.

A) network
B) application
C) network access/data link
D) physical

Question 32

____ means that if the transmitting modem sends data and the data arrives garbled,the receiving modem may ask the transmitting modem to fall back to a slower transmission speed.

A) Impulse negotiation
B) Fallback negotiation
C) Attenuation
D) Downlink

Question 33

In a sliding-winow error control system,a receiver may acknowledge multiple packets with a single ACK.

Question 34

Error bursts occur ____ percent of the time.

A) 2 to 5
B) 5 to 10
C) 8 to 10
D) 10 to 20

Question 35

To minimize the effect of echo,a device called a(n)____ can be attached to a line.

A) echo suppressor
B) repeater
C) amplifier
D) hub

Question 36

CRC-____ is found in Ethernet LANs.

A) 5
B) 12
C) 32
D) 64

Question 37

An arithmetic checksum _______ the individual characters to be transmitted.

A) adds
B) multiplies
C) inverts
D) divides

Question 38

Installing proper shielding on cables prevents ____.

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

Question 39

____ is the result of small timing irregularities that become magnified during the transmission of digital signals as the signals are passed from one device to another.

A) White noise
B) Jitter
C) Attenuation
D) Echo

Question 40

With ____ parity,the 0 or 1 added to the string produces an even number of binary 1s.

A) even
B) odd
C) longitudinal
D) binary

Question 41

A(n)____________________ is essentially a filter that allows the signal to pass in one direction only.

Question 42

____ error control is a technique usually associated with the Stop-and-wait flow control protocol.

A) Stop-and-wait
B) Timeout
C) Sliding window
D) ACK

Question 43

____ cable is the medium least prone to generating errors.

A) Fiber-optic
B) Coaxial
C) Twisted-pair
D) Copper-based

Question 44

____________________ is a relatively continuous type of noise and is much like the static you hear when a radio is being tuned between two stations.

Question 45

Simple parity comes in two basic forms: even parity and ____________________ parity.

Question 46

____________________ is the reflective feedback of a transmitted signal as the signal moves through a medium.

Question 47

____________________ is an unwanted coupling between two different signal paths.

Question 48

____________________ is the continuous loss of a signal's strength as it travels though a medium.

Question 49

If a receiver has just received one packet of data with bytes numbered 600 to 700,it will respond immediately with ____.

A) an ACK of 700
B) an ACK of 701
C) an ACK of 800
D) it will not respond just yet

Question 50

____ is a flow control scheme that allows a station to transmit a number of data packets at one time before receiving some form of acknowledgment.

A) Stop-and-wait
B) Sliding window
C) Timeout
D) ACK window

Question 51

With the sliding window protocol,a station that had a maximum window size of 7 could transmit only ____ data packets at one time before it had to stop and wait for an acknowledgment.

A) 5
B) 6
C) 7
D) 8

Question 52

____________________ is a noncontinuous noise and one of the most difficult errors to detect,because it can occur randomly.

Question 53

When working with stop-and-wait error control,the amount of time a station waits before retransmitting a packet is called ____.

A) stop time
B) ACK time
C) NAK time
D) timeout

Question 54

____ is probably the most common form of error control.

A) Toss the frame (do nothing)
B) Correct the error without retransmission
C) Sending a message back to the transmitter
D) Correct the error with retransmission

Question 55

For a receiver to be able to fix an error-in a process called ____-redundant information must be present so that the receiver knows which bit or bits are in error and what their original values were.

A) forward error correction
B) forward error detection
C) backward error correction
D) backward error detection

Question 56

A ____ protocol's function is simply to inform the transmitter what piece of data is expected next.

A) CRC-16
B) CRC-32
C) stop-and-wait
D) sliding window

Question 57

The simplest error-detection technique is ____________________ parity.

Question 58

____ for error control is becoming a mode of operation for some modern wide area network transmission techniques.

A) Returning a message
B) Toss the frame/packet
C) Correcting the error
D) Fixing the error

Question 59

When a digital signal is being transmitted,the rises and falls of the signal can start to shift,or become blurry,and thus produce ____________________.

Question 60

If a receiver correctly receives packets 2,3,and 4,it will respond with a(an)____ .

A) ACK 3
B) ACK 4
C) ACK 5
D) NAK

Question 61

With ____________________ parity,the 0 or 1 added to the string produces an odd number of binary 1s.

Question 62

A(n)_________________________ is an industry-approved bit string that is used to create the cyclic checksum remainder.

Question 63

How does frame relay control errors?

Question 64

The ____________________ of a code is the smallest number of bits by which character codes differ.

Question 65

Sliding window error control is based on the ____________________ protocol.

Question 66

How does longitudinal parity work?

Question 67

____________________ parity tries to solve the main weakness of simple parity-that all even numbers of errors are not detected.

Question 68

How does the cyclic redundancy checksum work?

Question 69

The ____________________ method typically adds 8 to 32 check bits to potentially large data packets and yields an error detection capability approaching 100 percent.

Question 70

In TCP/IP,if a receiver just received some data and wishes to send data back to the sender,then the receiver should include an ACK with the data it's about to send.This is called ____________________.

Question 71

A(n)____________________ code is a specially designed code in which special check bits have been added to data bits such that,if an error occurs during transmission,the receiver may be able to correct the error using the included check and data bits.

Question 72

List and briefly explain some error-prevention techniques.

Question 73

How does simple parity work?

Question 74

Once an error in the received data transmission stream is detected,the action that the receiver takes is called ____________________.

Question 75

____________________ is a process that keeps a transmitter from sending too much data to a receiver.