Data Communications - Ch 4

In a _________ , more than one data bit is changed by the error-causing condition. 1. burst error 2. data rate shift 3. Trellis-coded modulation 4. uniform distribution 5. amplitude key shift

1

Which of the following media is least susceptible to noise? 1. fiber optic cable 2. coaxial cable 3. twisted pair 4. unshielded twisted pair 5. shielded twisted pair

1

With contention: 1. computers wait until the circuit is free before they send data 2. the server or front end processor works consecutively through a list of clients to determine who should have access to the media 3. the front end processor must wait for a response from the polled client or terminal 4. one computer starts the poll and passes it to the next computer on the multipoint circuit 5. there is never a chance for "collision," or two computers trying to send data at the same time

1

With odd parity and a 7-bit ASCII code, 0110011, what is the parity bit?

1

_____________ is an effective way to prevent impulse noise, cross talk, and intermodulation noise. 1. Shielding wires 2. Adding fluorescent lights 3. Adding repeaters to a circuit 4. Adding amplifiers to a circuit 5. Shorting a circuit

1

Errors on a network can occur: 1. only on dial-up type of circuits 2. because of noise on the line 3. only on poorly maintained networks 4. only due to Gaussian noise 5. only due to lightning strikes

2

When a signal is reflected back to the transmitting equipment, it is called a(n) _________. 1. white noise 2. echo 3. crosstalk 4. attenuation 5. impulse noise

2

Consider case study IV (Alpha Corp) on page 106. How many bits per second are generated by web accesses. Give your answer in whole number kbps.

267

Consider case study IV (Alpha Corp) on page 106. How many bits per second are generated by both email and web applications? Give your answer in whole number kbps.

270

The primary source of error in data communications is: 1. echoes 2. intermodulation noise 3. spikes 4. attenuation 5. cross-talk

3

____________ is not a function of a data link protocol. 1. Media access control 2. Message delineation 3. Amplitude shift keying 4. Indicating when a message starts and stops 5. Error control

3

Asynchronous transmission uses 7 bits for transmitting a character and 1 start bit and 1 parity bit for each character. What is the transmission efficiency in % (rounded to the nearest whole number)?

78

We transmit 1000 bytes using Ethernet 802.3ac frame (see Figure 4.8a on page99). Assume VLAN tag is not used and the control field is 1 byte long. Ignore interframe spacing. What is the transmission efficiency? Round your answer to the nearest whole number percentage.

97

Contention MAC approaches work better in a large network with high usage.

False

Impulse noise is caused by the thermal agitation of electrons.

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

Attenuation refers to the loss of signal strength.

True

Contention is commonly used with Ethernet local area networks.

True

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

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

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

True