Switching to VoIP

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

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Chapter 6

CHAPTER 6

Replacing the Voice Circuit with VoIP

In circuit-switched voice networks, every time a call is placed, the network estab-

lishes a dedicated pathway from the calling endpoint through the network to the

receiving endpoint. This pathway is called a loop, and it always uses the same

amount of network resources (bandwidth) for the duration of the call, even if

nobody is speaking. Fortunately, VoIP provides a way of leveraging packet-switched

networks in order to make more economic use of available bandwidth.

This chapter describes the software and hardware elements of the voice loop as it

exists in Voice over IP so you can get the most out of it. Indeed, a VoIP admin can do

more to improve the quality and economics of his network by “tweaking the loop”

than he can by fiddling with any other aspect of the network.

The “Dumb” Transport

In a VoIP network, each loop, or pathway, from caller to receiver is virtualized and

controlled using software. So, during times of silence, for instance, the call’s path-

way doesn’t need to utilize a full amount of bandwidth, and the shared resources of

the network may be better utilized by another call—or perhaps by another applica-

tion altogether.

LAN and WAN data links, each capable of carrying TCP/IP, are just systems for

moving bits, ...