MIS 160 Chapter 4 Homework questions

One type of forward error correction is the Hamming code. True False

True

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. True False

True

The simplest method for error correction is retransmission. True False

True

_____________ is an effective way to prevent impulse noise, cross talk, and intermodulation noise. Shielding wires Adding fluorescent lights Adding repeaters to a circuit Adding amplifiers to a circuit Shorting a circuit

Adding fluorescent lights

When a signal is reflected back to the transmitting equipment, it is called a(n) _________. white noise echo crosstalk attenuation impulse noise

echo

____________ is an effective way to prevent attenuation. Shielding wires Adding fluorescent lights Adding repeaters or amplifiers to a circuit Changing multiplexing techniques Shorting a circuit

Adding repeaters or amplifiers to a circuit

Gaussian noise is a special type of attenuation. True False

False

Impulse noise is caused by the thermal agitation of electrons. True False

False

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. True False

False

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

False

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

False

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

False

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

False

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

False

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

False

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

False

______________ controls errors by detecting and correcting them at the receiving end without retransmission of the original message. Hamming code Huffman encoding Front end processing Wave division multiplexing Hub polling

Hamming code

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

True

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

True

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

True

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. True False

True

Undesirable stray electrical voltage can cause data communication errors. True False

True

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

True

Which of the following is not a type of synchronous protocol? SDLC VT100 HDLC Ethernet PPP

VT100

Stop-and-wait ARQ uses ___________ type of data flow. full simplex half complex full duplex half duplex full complex

half duplex

Contention is commonly used with Ethernet local area networks. True False

True

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

True

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

True

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

True

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

True

Forward error correction is commonly used in satellite transmission. True False

True

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

True

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

True

Which of the following is not a controlled access method of media access control? Token passing CSMA/CD polling roll call polling hub polling

CSMA/CD

Data transmission errors are typically uniformly distributed in time. True False

False

Which of the following is true with respect to the data link layer? It accepts streams of bits from the application layer. It is responsible for encoding the bit-stream as a series of electronic voltages. It performs error detection. It performs routing functions. It organizes data from the physical layer and passes these coherent messages directly to the application layer.

It performs error detection.

Attenuation refers to the loss of signal strength. True False

True

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

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: about 50% for either even or odd parity about 70% for even parity and 30% for odd parity about 30% for even parity and 70% for odd parity about 0% for either even or odd parity about 100% for either even or odd parity

about 50% for either even or odd parity

In a _________ , more than one data bit is changed by the error-causing condition. burst error data rate shift Trellis-coded modulation uniform distribution amplitude key shift

burst error

Another term for stop-and-wait ARQ is sliding window. True false

false

Which of the following media is least susceptible to noise? fiber optic cable coaxial cable twisted pair unshielded twisted pair shielded twisted pair

fiber optic cable

In communication protocols, _________ are used to convey the user's meaning. information bits overhead bits stop bits start bits flag bits

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: intermodulation noise attenuation echo white noise cross-talk

intermodulation noise

Media access control: is not very important in point-to-point with full duplex configuration is not very important in local area networks is not very important in a point-to-point with a half duplex configuration is not very important in a multipoint configuration does not control when computers transmit

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

Synchronous transmission: cannot be used on multipoint circuits is used to send one character at a time uses start bits before each character to be sent uses stop bits after each character to be sent is used to transmit a "frame" or "packet" of data at a time

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

Which of the following is true about the data link protocol, PPP? it is commonly used in WANs it is a bit-oriented protocol it uses block check characters for error detection it was developed in the 1960s it uses parity bits for error detection

it is commonly used in WANs

The two sublayers of the data link layer consist of the media access control sublayer and the________ . logical link control sublayer network control sublayer session sublayer physical sublayer transport sublayer

logical link control sublayer

Which of the following is way to reduce or eliminate crosstalk on a circuit? physically separating the cables from other communication cables adding repeaters or amplifiers to a circuit reducing the length of the cable adding fluorescent lights shorting a circuit

physically separating the cables from other communication cables

Another term for impulse noise is: Gaussian noise spikes attenuation crosstalk intermodulation noise

spikes

The primary source of error in data communications is: echoes intermodulation noise spikes attenuation cross-talk

spikes

With __________ ARQ, the sender pauses for a response from the receiver to alter each message or packet of data. open window halt and be recognized (HBR) sliding window stop and wait continuous

stop and wait

The familiar background static on radios and telephones is called: echoes intermodulation noise impulse noise crosstalk white noise

white noise