DATA AND COMPUTER COMMUNICATIONS Essay

6603 Words Mar 31st, 2014 27 Pages
SOLUTIONS MANUAL
DATA AND COMPUTER
COMMUNICATIONS
EIGHTH EDITION
CHAPTERS 1 - 12

WILLIAM STALLINGS

Copyright 2007: William Stallings

© 2007 by William Stallings
All rights reserved. No part of this document may be reproduced, in any form or by any means, or posted on the Internet, without permission in writing from the author. Selected solutions may be shared with students, provided that they are not available, unsecured, on the Web.
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NOTICE

This manual contains solutions to all of the review questions and homework problems in Data and Computer Communications, Eighth
Edition. If you spot an error in a solution or in the wording of a problem, I would greatly appreciate it if you would forward the
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The road provides the physical path for delivery.
2.2 a.
French PM

Chinese PM

Translator (F → E)

Translator (E → C)

Telephone

Telephone
Telephone line

The PMs speak as if they are speaking directly to each other. For example, when the
French PM speaks, he addresses his remarks directly to the Chinese PM. However, the message is actually passed through two translators via the phone system. The
French PM's translator translates his remarks into English and telephones these to the Chinese PM's translator, who translates these remarks into Chinese.
b.
French PM

Chinese PM

Tr (F → G)

Tr (G → J)

Tr (J → C)

Phone

Phone Phone

Phone

Telephone line

An intermediate node serves to translate the message before passing it on. Note that the intermediate node handles the message only up to the second level; a minister's level is not needed.
2.3 Perhaps the major disadvantage is the processing and data overhead. There is processing overhead because as many as seven modules (OSI model) are invoked to move data from the application through the communications software. There is data overhead because of the appending of multiple headers to the data. Another possible disadvantage is that there must be at least one protocol standard per layer.
With so many layers, it takes a long time to develop and promulgate the standards.
2.4 No. There is no way to be assured that the last message gets through, except by

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