Name: 
 

CS-320 Data Communications Exam 4



True/False
Indicate whether the statement is true or false.
 

 1. 

Because white noise is relatively continuous, it can be reduced significantly but never completely eliminated.
 

 2. 

Telephone signal crosstalk was a more common problem before telephone companies used fiber-optic cables and other well-shielded wires.
 

 3. 

If jitter becomes too great, correcting it can require the transmitting devices to speed up their transmission rates.
 

 4. 

Attenuation can be eliminated with the use of repeaters for analog systems.
 

 5. 

Simple parity can detect only an even number of erroneous bits per character.
 

 6. 

The CRC method catches almost 100% of errors.
 

 7. 

Sliding window protocols have been around since the 1970s.
 

 8. 

In a stop-and-wait error control system, a receiver may acknowledge multiple packets with a single ACK.
 

 9. 

A local area network cannot interface with other local area networks.
 

 10. 

Most modern local area networks provide the capabilities of transferring video images and video streams.
 

 11. 

With the CSMA/CD protocol, only one workstation at a time can transmit.
 

 12. 

If the network is experiencing a high amount of traffic, the chances for collision are small.
 

 13. 

The hub, in most applications, has been replaced with the switch.
 

 14. 

Network operating systems are essential if the network is going to allow multiple users to share resources.
 

 15. 

In reality, a multitasking operating system runs only one program at a time.
 

 16. 

The resources that a network operating system must manage typically include one or more network servers.
 

 17. 

It is not possible to create a Windows Server network with multiple domains.
 

 18. 

Unix is often found with a text-based interface, although graphical user interfaces are available.
 

 19. 

White noise is dependent on the temperature of the medium.
 

 20. 

If impulse noise interferes with a digital signal, often the original digital signal cannot be recognized and recovered.
 

 21. 

Echo error rarely occurs at junctions where wires are connected.
 

 22. 

Installing special filters for analog signals and digital signal regeneration for digital signals helps in preventing white noise.
 

 23. 

The CRC error-detection method treats the packet of data to be transmitted as a large polynomial.
 

 24. 

When a parity bit is assigned to ASCII, the Hamming distance becomes 4.
 

 25. 

TCP performs error detection at the end points of the connection.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 1. 

Impulse noise is also known as ____.
a.
noise spike
c.
attenuation
b.
jitter
d.
crosstalk
 

 2. 

High humidity and wet weather can cause an increase in electrical ____ over a telephone system.
a.
compression
c.
jitter
b.
attenuation
d.
crosstalk
 

 3. 

____ is the result of small timing irregularities that become magnified during the transmission of digital signals as the signals are passed from one device to another.
a.
White noise
c.
Attenuation
b.
Jitter
d.
Echo
 

 4. 

Causes of jitter can include electromagnetic interference, ____, passing the signal through too many repeaters, and the use of lower-quality equipment.
a.
coding
c.
compression
b.
sampling
d.
crosstalk
 

 5. 

____ is not necessarily a form of error, but can indirectly lead to an increase in errors affecting the transmitted signal.
a.
Impulse noise
c.
Attenuation
b.
Crosstalk
d.
White noise
 

 6. 

____ means that if the transmitting modem sends data and the data arrives garbled, the receiving modem may ask the transmitting modem to fall back to a slower transmission speed.
a.
Impulse negotiation
c.
Attenuation
b.
Fallback negotiation
d.
Downlink
 

 7. 

Twisted pair Category 5e/6 cable should not be longer than the recommended 100-meter (300-foot) distance when it’s transmitting at ____ Mbps.
a.
100
c.
500
b.
250
d.
1000
 

 8. 

Installing proper shielding on cables prevents ____.
a.
white noise
c.
attenuation
b.
impulse noise
d.
crosstalk
 

 9. 

Error detection can be performed in several places within a communications model. One of the most common places is the TCP/IP ____ layer.
a.
network
c.
network access/data link
b.
application
d.
physical
 

 10. 

The most basic error-detection techniques are parity checks, which are used with ____ connections.
a.
synchronous
c.
statistical
b.
asynchronous
d.
fiber-optic
 

 11. 

With ____ parity, the 0 or 1 added to the string produces an even number of binary 1s.
a.
even
c.
longitudinal
b.
odd
d.
binary
 

 12. 

Isolated single-bit errors occur ____ percent of the time.
a.
30 to 40
c.
50 to 60
b.
40 to 50
d.
60 to 70
 

 13. 

Error bursts occur ____ percent of the time.
a.
2 to 5
c.
8 to 10
b.
5 to 10
d.
10 to 20
 

 14. 

An arithmetic checksum _______ the individual characters to be transmitted.
a.
adds
c.
inverts
b.
multiplies
d.
divides
 

 15. 

CRC-____ is found in Ethernet LANs.
a.
5
c.
32
b.
12
d.
64
 

 16. 

____ for error control is becoming a mode of operation for some modern wide area network transmission techniques.
a.
Returning a message
c.
Correcting the error
b.
Toss the frame/packet
d.
Fixing the error
 

 17. 

____ cable is the medium least prone to generating errors.
a.
Fiber-optic
c.
Twisted-pair
b.
Coaxial
d.
Copper-based
 

 18. 

____ is probably the most common form of error control.
a.
Toss the frame (do nothing)
b.
Correct the error without retransmission
c.
Sending a message back to the transmitter
d.
Correct the error with retransmission
 

 19. 

____ error control is a technique usually associated with the Stop-and-wait flow control protocol.
a.
Stop-and-wait
c.
Sliding window
b.
Timeout
d.
ACK
 

 20. 

With the sliding window protocol, a station that had a maximum window size of 7 could transmit only ____ data packets at one time before it had to stop and wait for an acknowledgment.
a.
5
c.
7
b.
6
d.
8
 

 21. 

The local area network software called a ____ server provides workstations with the authorization to access a particular printer, accepts and queues prints jobs, prints cover sheets, and allows users access to the job queue for routine administrative functions.
a.
application
c.
file
b.
database
d.
print
 

 22. 

The ____ topology consists of a simple cable, or bus, to which all devices attach.
a.
bus/tree
c.
ring star
b.
token ring
d.
star
 

 23. 

The most popular configuration for a local area network is the ____ topology.
a.
ring
c.
bus
b.
star-wired bus
d.
tree
 

 24. 

The ____ design of a network determines how the data moves around the network from workstation to workstation.
a.
electrical
c.
physical
b.
data
d.
logical
 

 25. 

When two or more hubs are interconnected and a workstation transmits data, all the workstations connected to all the hubs receive the data. This is an example of a(n) ____.
a.
wireless topology
c.
shared network
b.
switched network
d.
FDDI topology
 

 26. 

A(n) ____ protocol is the software that allows a workstation to place data onto a local area network.
a.
error control
c.
medium access control
b.
noise control
d.
flow control
 

 27. 

The ____ is used to connect local area networks to wide area networks.
a.
hub
c.
router
b.
repeater
d.
bridge
 

 28. 

A ____ is a device that interconnects two or more workstations in a star-wired bus local area network and immediately retransmits the data it receives from any workstation out to all other workstations connected.
a.
hub
c.
router
b.
switch
d.
repeater
 

 29. 

The switch operates in place of a ____.
a.
repeater
c.
router
b.
bridge
d.
hub
 

 30. 

In a ____ architecture, the data frame begins to exit the switch almost as soon as it begins to enter the switch.
a.
forward
c.
cut-through
b.
backward
d.
random-propagation
 

 31. 

Typically, impulse noise is a(n) ____ burst of energy.
a.
digital
c.
binary
b.
analog
d.
logical
 

 32. 

When working with stop-and-wait error control, the amount of time a station waits before retransmitting a packet is called ____.
a.
stop time
c.
NAK time
b.
ACK time
d.
timeout
 

 33. 

____ is a flow control scheme that allows a station to transmit a number of data packets at one time before receiving some form of acknowledgment.
a.
Stop-and-wait
c.
Timeout
b.
Sliding window
d.
ACK window
 

 34. 

A ____ protocol’s function is simply to inform the transmitter what piece of data is expected next.
a.
CRC-16
c.
stop-and-wait
b.
CRC-32
d.
sliding window
 

 35. 

For a receiver to be able to fix an error—in a process called ____—redundant information must be present so that the receiver knows which bit or bits are in error and what their original values were.
a.
forward error correction
c.
backward error correction
b.
forward error detection
d.
backward error detection
 

 36. 

If a receiver has just received one packet of data with bytes numbered 600 to 700, it will respond immediately with ____.
a.
an ACK of 700
c.
an ACK of 800
b.
an ACK of 701
d.
it will not respond just yet
 

Completion
Complete each statement.
 

 1. 

____________________ is a noncontinuous noise and one of the most difficult errors to detect, because it can occur randomly.
 

 

 2. 

Simple parity comes in two basic forms: even parity and ____________________ parity.
 

 

 3. 

With ____________________ parity, the 0 or 1 added to the string produces an odd number of binary 1s.
 

 

 4. 

Once an error in the received data transmission stream is detected, the action that the receiver takes is called ____________________.
 

 

 5. 

____________________ is a process that keeps a transmitter from sending too much data to a receiver.
 

 

 6. 

A(n) _________________________ is a communications network that interconnects a variety of data communications devices within a small geographic area and broadcasts data at high data transfer rates.
 

 

 7. 

A(n) ____________________ protocol is basically a first-come, first-served protocol.
 

 

 8. 

A(n) ____________________ occurs when two or more workstations listen to the medium at the same moment, hear nothing, and then transmit their data at the same moment.
 

 

 9. 

____________________ was designed to support 100-Mbps baseband signals using two pairs of Category 5 unshielded twisted pair.
 

 

 10. 

The ____________________ is a device that connects workstations to local area networks and retransmits the incoming frame.
 

 

 11. 

A(n) ____________________ is a logical subgroup within a local area network that is created via switches and software rather than by manually moving wiring from one network device to another.
 

 

 12. 

The ____________________ allows for a CSMA/CD network to simultaneously transmit and receive data to and from a workstation.
 

 

 13. 

One of the fastest growing segments of the software market is ____________________ software, the tool set to support Internet-related services.
 

 

 14. 

A(n) ____________________ license, operating system user license, and controlled number of concurrent users license all refer to essentially the same situation.
 

 

 15. 

The type of algorithm that tries to avoid collisions is called _____________________________________________.
 

 

 16. 

When a digital signal is being transmitted, the rises and falls of the signal can start to shift, or become blurry, and thus produce ____________________.
 

 

 17. 

____________________ is the continuous loss of a signal’s strength as it travels though a medium.
 

 

 18. 

The simplest error-detection technique is ____________________ parity.
 

 

 19. 

____________________ parity tries to solve the main weakness of simple parity—that all even numbers of errors are not detected.
 

 

 20. 

The ____________________ method typically adds 8 to 32 check bits to potentially large data packets and yields an error detection capability approaching 100 percent.
 

 

 21. 

Sliding window error control is based on the ____________________ protocol.
 

 



 
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