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Understanding Data Communications: From Fundamentals to Networking

Gilbert Held

Chapter 12

Increasing WAN Line Utilization - all with Video Answers

Educators

Chapter Questions

Problem 1

What are the major differences between time division multiplexing and frequency division multiplexing?

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Problem 2

How many 300 bps data sources could be multiplexed by a frequency division multiplexer and by a traditional time division multiplexer?

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Problem 3

Why does frequency division multiplexing inherently provide multidrop transmission capability without requiring addressable terminals and poll and select software?

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Problem 4

Assume that your organization has two computer systems, one located in city A and another located in city B. Suppose that your organization has eight terminals in city C and 10 terminals in city B, with the following computer access requirements:
Table Can't Copy

Draw a network schematic diagram illustrating the use of time division hubbypass multiplexing to connect the terminals to the appropriate computers.

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Problem 5

Why is a front-end processor substitution for a multiplexer at a computer site the exception rather than the rule?

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Problem 6

Assume that the cost of communications equipment and facilities is as follows:

8-channel TDM at $$\$ 500$$
28800 modem at $$\$ 400$$
leased line city A to city B $$\$1000/month$$
If twelve 2400 bps terminals are located in city A and the computer is located in city $B$, draw a schematic of the multiplexing network required to permit the terminals to access the computer, assuming each terminal can be directly connected to the multiplexer. What is the cost of this network for one year of operation?

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01:15

Problem 7

Assume that the requirements of Question 6 are modified, resulting in all twelve terminals being located beyond cabling distance of the multiplexer. Assume the following cost of communications equipment and facilities:
$$
\begin{array}{ll}
8 \text { position rotary } & \$ 50 / \text { month } \\
\text { telephone lines at } & \$ 30 / \text { month } \\
2400 \text { bps modems at } & \$ 30
\end{array}
$$
Draw a revised schematic of the multiplexing network.What is the cost of this network for one year of operation?

Kratika Bhadauria
Kratika Bhadauria
Numerade Educator

Problem 8

Why must a statistical multiplexer add addressing information to the data it multiplexes?

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Problem 9

Why are most statistical multiplexers ill-suited for multiplexing multidrop circuits?

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Problem 10

Assume that the statistical muiltiplexer you are considering using has an efficiency 2.5 times that of a conventional TDM. If you anticipate connecting the multiplexer to a 28800 bps modem, how many 2400 bps data sources should the multiplexer multiplex.

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Problem 11

Assume that the multiplexer discussed in Question 10 services synchronous data by the use of a bandpass channel. What would be the effect upon the number of 2400 bps asynchronous data sources supported in Question 10 if you must service a 9600 bps synchronous data source by the use of a bandpass channel?

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Problem 12

Assume that you are considering the use of an intelligent multiplexer that has an efficiency three times that of a conventional multiplexer for asynchronous data traffic and 1.5 that of a conventional multiplexer for synchronous data traffic. If you have to multiplex 181200 bps asynchronous terminals and four 2400 bps synchronous terminals on a line operating at 9600 bps , could the multiplexer support you requirement? Why?

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Problem 13

How could you use the statistical loading data available from an intelligent multiplexer to determine if the vendor's literature concerning its efficiency in comparison to a conventional TDM is reasonable?

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Problem 14

Draw a network schematic showing how the port contention option of a multiplexer could be used in a hub-bypass network.

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Problem 15

You are comparing the cost of inverse multiplexing to using wideband facilities to transmit data at 38400 bps , and you determine the monthly cost of the following facilities and devices.
$$
\begin{array}{cc}
\text { Facility/device } & \text { Monthly cost } \\
\text { Wideband line } & \$ 2820 \\
\text { Voice-grade line } & \$ 750 \\
\text { Inverse multiplexer at } & \$ 225 \\
19200 \mathrm{bps} \text { modem at } & \$ 35
\end{array}
$$
Would it be economical with these figures to use inverse multiplexers?

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Problem 16

What are the primary advantages of inverse multiplexing in comparison to wideband transmission?

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Problem 17

Describe two applications suitable for a bandwidth on demand multiplexes.

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01:12

Problem 18

What is the major difference between a channel-attached and a link-attached communications controller?

Aditya Sood
Aditya Sood
Numerade Educator
01:02

Problem 19

Assume the cost of a fractional T1 (FT1) line operating at 384 kbps between New York and Chicago is $$\$ 2100$$ per month. If the use of 64 kbps ISDN costs 10 cents/minute, how many minutes per month can you operate a 384 kbps videoconference between locations prior to exceeding the cost of the FT1 line? (For the problem, do not consider the cost of inverse multiplexers.)

Ashley Hanson
Ashley Hanson
Numerade Educator

Problem 20

Why is it difficult to attach RS-232/V.24 devices to an IBM 327 g Information Display System network? Discuss some of the products one can obtain to connect RS-232/V. 24 devices into a 3279 network to include their operational features.

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