ISDS 409 Chapter 4

In general, controlled approaches do not require a host, server, or active monitor to assign media access control

False

In general, controlled approaches have many collisions

False

In general, controlled approaches work better than contention approaches for all sizes of networks

False

In general, controlled approaches work better than contention approaches for small networks that have low usage

False

Media access control does not control when computers transmit.

False

Media access control is not very important in a multipoint configuration.

False

Media access control is not very important in a point-to-point with a half-duplex configuration

False

Synchronous transmission cannot be used on multipoint circuits.

False

There are three commonly used controlled access techniques: access requests, access demands, and polling.

False

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

False

Using parity, the probability for detecting an error, given that one has occurred, is about 100% for either even or odd parity

False

Using parity, the probability for detecting an error, given that one has occurred, is about 20% for either even or odd parity.

False

Using parity, the probability for detecting an error, given that one has occurred, is about 25% for either even or odd parity

False

Using parity, the probability for detecting an error, given that one has occurred, is about 30% for even parity and 70% for odd parity

False

Using parity, the probability for detecting an error, given that one has occurred, is about 70% for even parity and 30% for odd parity

False

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

True

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

True

In general, controlled approaches work better than contention approaches for large networks that have high usage

True

One type of forward error correction is the Hamming code

True

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

True

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

True

The simplest method for error correction is retransmission

True

When the signals from two circuits combine to form a new signal that falls into a frequency band reserved for another signal, this is called intermodulation noise.

True

When we amplify the signal on an analog circuit, we also amplify any noise that is present on the circuit

True

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

True

Another term for continuous ARQ is sliding window

False

The data link protocol, Ethernet (IEEE 802.3) is not very popular

False

The thermal agitation of electrons causes impulse noise

False

The probability of detecting an error, provided that one has occurred, using cyclic redundancy checking is about: a. 0% b. 75% c. 50% d. > 99% e. exactly 100%

d. > 99%

____________ 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

_______ has essentially replaced SDLC. It offers a larger sliding window. a. Ethernet b. PPP c. Asynchronous transmission d. HDLC e. Full complex

d. HDLC

43. Which of the following is true about the data link protocol, Ethernet (IEEE 802.3)? a. It is not very popular. b. It is a bit-oriented protocol. c. it uses block check characters for error detection. d. Newer version permits jumbo frames. e. It uses parity bits for error detection.

d. Newer version permits jumbo frames.

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. Odd parity

d. Pulse code checking

Gaussian noise is a special type of attenuation.

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

False

Media access control is not very important in local area networks.

False

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

False

Most computer networks managed by a host mainframe computer tend to use a form of media access control called contention.

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.

False

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

False

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

False

Roll call polling cannot be modified to increase priority of clients or terminals

False

Roll call polling does not require a server, host, or special device that performs the polling

False

Roll call polling is a type of contention approach to media access control.

False

Synchronous transmission is used to send one character at a time

False

Synchronous transmission uses start bits before each character to be sent

False

Synchronous transmission uses stop bits after each character to be sent

False

The data link layer accepts streams of bits from the application layer.

False

The data link layer is responsible for encoding the bit-stream as a series of electronic voltages

False

The data link layer organizes data from the physical layer and passes these coherent messages directly to the application layer.

False

The data link layer performs routing functions

False

The data link protocol SDLC It uses a contention media access control protocol and is used in most LANs today

False

The data link protocol SDLC does not have any error detection capabilities

False

The data link protocol SDLC is a client-server protocol developed by Compaq in 1996

False

The data link protocol SDLC transmits each character independently of one another and includes start and stop bits for each character sent

False

The data link protocol, Ethernet (IEEE 802.3) is a bit-oriented protocol

False

The data link protocol, Ethernet (IEEE 802.3) uses block check characters for error detection.

False

The data link protocol, Ethernet (IEEE 802.3) uses parity bits for error detection

False

The data link protocol, PPP is a bit-oriented protocol.

False

The data link protocol, PPP uses block check characters for error detection.

False

The data link protocol, PPP uses parity bits for error detection.

False

The data link protocol, PPP was developed in the 1960s

False

The two categories of network errors are lost data and delimited data

False

With contention, a computer does not have to wait before it can transmit. A computer can transmit at any time

False

Regarding the data link protocol, Ethernet (IEEE 802.3), newer version permits jumbo frames

True

Roll call polling typically involves some waiting because the server has to wait for a response from the polled client or terminal

True

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

True

The data link layer performs error detection.

True

The data link protocol SDLC uses a special bit pattern called a flag at the beginning and end of every frame (or packet)

True

The data link protocol, PPP is commonly used in WANs

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

Undesirable stray electrical voltage can cause data communication errors

True

Using parity, the probability for detecting an error, given that one has occurred, is about 50% for either even or odd parity

True

14. 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.

11. 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. white noise b. echo c. crosstalk d. attenuation e. impulse noise

b. echo

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

b. repeaters

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

b. spikes

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 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

Roll call polling is also called token passing

False

Media access control is not very important in point-to-point with full duplex configuration.

True

Contention is widely used with Ethernet local area networks.

True

Controlled access MAC approaches work well in a large network with high usage

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

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

True

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

True

Forward error correction is commonly used in satellite transmission

True

Which of the following is not a type of synchronous protocol? a. SDLC b. VT100 c. HDLC d. Ethernet e. PPP

b. VT100

Data transmission errors typically are distributed uniformly in time

False

Attenuation refers to the loss of signal strength

True

______________ 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

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

a. It is commonly used in WANs.

The data link layer uses the ________ to recognize the source and destination addresses a. MAC address b. IP address c. URL d. Email address e. Local router

a. MAC address

__________ is a software-enabled technique that can change the hardcoded MAC address to any MAC address and thus overcome MAC address filtering. a. MAC address spoofing b. MAC address engaging c. Ethernet address regeneration d. Address regeneration e. MAC address cheesing

a. MAC address spoofing

Which of the following is way to reduce or eliminate crosstalk on a circuit? a. Physically separating the cables from other communication cables b. Adding repeaters or amplifiers to a circuit c. Reducing the length of the cable d. Adding fluorescent lights e. Shorting a circuit

a. Physically separating the cables from other communication cables

_____________ 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 circut

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.

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

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

3. 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 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. white noise e. cross-talk

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

12. The two sublayers of the data link layer consist of the media access control sublayer and the________. a. logical link control sublayer b. network control sublayer c. session sublayer d. physical sublayer e. transport sublayer

a. logical link control sublayer

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.

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

The probability of detecting an error, given that one has occurred, using parity checking is about: a. 0% b. 50% c. 75% d. 98% e. 100%

b. 50%

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

b. CSMA/CD

________ 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

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

b. work better than contention approaches for large networks that have high usage

_____________ 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

c. Amplitude shift keying

__________can obliterate a group of bits, causing a burst error. a. Cross-talk b. Attenuation c. Impulse noise d. Intermodulation noise e. Gray noise

c. Impulse noise

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 encoding the bit-stream as a series of electronic voltages. c. It performs error detection. d. It performs routing functions. e. It organizes data from the physical layer and passes these coherent messages directly to the application layer

c. It performs error detection.

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 transmits each character independently of one another and includes start and stop bits for each character sent. 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 and is used in most LANs today. e. It does not have any error detection capabilities

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. white noise 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. attenuation. e. cross-talk

c. spikes.

Which of the following is true about roll call polling? a. It cannot be modified to increase priority of clients or terminals. b. It does not require a server, 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 server has to wait for a response from the polled client or terminal

e. It typically involves some waiting because the 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

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. each character is transmitted independently of all other characters

e. each character is transmitted independently of all other characters

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. gray noise d. cross-talk e. white noise

e. white noise

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

false