Archive for October 2017

Synchronous transmission:

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



Answer: E

Asynchronous transmission:

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. is also known as start-stop transmission



Answer: E

ARQ means that:

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



Answer: A

Using parity, the probability for detecting an error, given that one has occurred, is:

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



Answer: A

_________ is an effective way to prevent attenuation.

_________ 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



Answer: C

Cross-talk:

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



Answer: A

Another term for impulse noise is:

Another term for impulse noise is: 




a. Gaussian noise
b. spikes
c. attenuation
d. cross-talk
e. intermodulation noise



Answer: B

Harmonic distortion can be prevented by

Harmonic distortion can be prevented by 



a. tuning equipment
b. moving wires
c. increasing guardbands
d. increasing signal strength
e. using a high-speed circuit


Answer: A

Errors on a network can occur:

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


Answer: B

In general, controlled approaches:

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



Answer: B

With contention:

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



Answer: A

Which of the following is true about roll call polling?

Which of the following is true about roll call polling? 




a. It can not be modified to increase priority of clients or terminals.
b. It does not require a server or 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.



Answer: E

Media access control:

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


Answer: A

______ is not a function of a data link protocol.

______ 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


Answer: C

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

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 getting a message from one computer to another (one node to another) without errors.
c. It does not perform error detection.
d. It performs routing functions.
e. It organizes data from the physical layer and passes these coherent messages to the application layer.



Answer: B
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