4.2 - Error Control

Question 1

These kinds of errors (ex: mistake in typing a number) are usually controlled through the app or program (through app validation and error messages)

Answer 1

Human errors

Question 2

These kinds of errors are controlled by the network hardware and software (ex: transmission error)

Answer 2

Network errors

Question 3

Two categories of network errors:

Answer 3

1. Corrupted data
2. Lost data

Question 4

Networks should be designed to ________, ________, and _________ both corrupted data and lost data

Answer 4

prevent…detect…correct

Question 5

Introduced by equipment or natural disturbances, and it degrades the performance of a communication circuit

Answer 5

Noise

Question 6

Noise manifests itself as:

Answer 6

1. Extra bits
2. Missing bits
3. Bits that have been “flipped”

Question 7

Sources of error:

Answer 7

1. White Noise
2. Impluse Noise
3. Crosstalk
4. Echo
5. Attenuation
6. Intermodulation Noise

Question 8

Movement of electrons

Answer 8

Cause of white noise:

Question 9

Sudden increases in electricity (e.g., lightning, surges)

Answer 9

Cause of impulse noise:

Question 10

Multiplexer guardbands too small or wires too close together

Answer 10

Cause of crosstalk:

Question 11

Poor connections

Answer 11

Cause of echo:

Question 12

Gradual decrease in signal over distance

Answer 12

Cause of attenuation:

Question 13

Signals from several circuits combine

Answer 13

Cause of intermodulation noise:

Question 14

Techniques to prevent errors:

Answer 14

1. Shielding
2. Moving Cables
3. Use of Repeaters/Amplifiers

Question 15

______________ is the process of protecting wires by covering them with an insulating coating

Answer 15

Shielding

Question 16

Shielding is one of the best ways to prevent:

Answer 16

1. Impulse noise
2. Crosstalk
3. Intermodulation noise

Question 17

______________ away from sources of noise can also reduce impulse noise, crosstalk, and intermodulation noise

Answer 17

Moving cables

Question 18

For _____________ — avoiding lights and heavy machinery

Answer 18

impulse noise

Question 19

For ___________ — physically separating the cables from other communication cables

Answer 19

crosstalk

Question 20

For ______, ________ —- tune transmission equipment and redo connections

Answer 20

echoes….white noise

Question 21

To avoid ______________, telephone circuits have repeaters or amplifiers spaced throughout their length

Answer 21

attentuation

Question 22

The only way to do error detection is to send ______________ with each message

Answer 22

extra data

Question 23

These error-detection data are added to each message by the ______________ layer of the sender on the basis of some mathematical calculations performed on the message

Answer 23

data link

Question 24

The ___________ performs the same mathematical calculations on the message it receives and matches its results with the message

Answer 24

receiver

Question 25

The rate at which a system, process, or operation can produce, process, or deliver units of output within a given time period

Answer 25

Thoroughput

Question 26

One of the oldest and simplest error-detection methods is ___________

Answer 26

parity

Question 27

The ______________ is to make the total number of 1s in the byte (including the parity bit) either an even number or an odd number

Answer 27

parity bit

Question 28

The value of this additional ______________ is based on the number of 1s in each byte transmitted

Answer 28

parity bit

Question 29

Parity can detect errors only when an ______ number of bits have been switched; any even number of errors cancel one another out

Answer 29

odd

Question 30

The probability of detecting an error is only about 50%

Answer 30

Parity checking

Question 31

With a checksum technique, a ____________ (typically 1 byte) is added to the end of the message

Answer 31

checksum

Question 32

______________ is calculated by adding the decimal value of each character in the message, dividing the sum by 255, and using the remainder as the checksum

Answer 32

Checksum

Question 33

Use of ______________ detects close to 95% of the errors for multiple-bit burst errors

Answer 33

checksum

Question 34

With ______________, a message is treated as one long binary number, which is divided by a preset number, and the remainder is used as the CRC code

Answer 34

cyclic redundancy check (CRC)

Question 35

It adds 8, 16, 24, or 32 bits to the message

Answer 35

cyclic redundancy check (CRC)

Question 36

Probability of detecting error is 99 - 100%

Answer 36

cyclic redundancy check (CRC)

Question 37

The simplest, most effective, least expensive, and most commonly used method for error correction is ______________

Answer 37

retransmission