Switching to VoIP

This is the Title of the Book, eMatter Edition

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

Voice Channels

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T1s are prevalent mainly in North America. In many other parts of the

world, high-density digital voice links are called E1 and allow 31

simultaneous phone calls.

Of course, all of VoIP’s economy and flexibility come at a price: sophistication of

infrastructure. Many traditional telephone technicians aren’t hip to what TCP/IP

brings to the table: disaster survivability, a uniform addressing scheme, data link

independence, and better integration with directory services. So, a lot of so-called

“phone guys” bash IP telephony, dismiss it as a fad, or even claim that it doesn’t

work. If you’ve done the first several projects in this book, then you know how

incorrect those claims are—because you’ve already used a simple VoIP network suc-

cessfully.

Voice Channels

A VoIP softswitch has two main functions: call management (or switching), which is

covered in the next chapter, and voice transmission.

Voice transmission—the packaging, transmittal, receiving, and reconstruction of dig-

itized voice data—occurs inside virtualized pathways across the TCP/IP network.

Many softPBX systems, Asterisk included, call them channels. The word channel

does mean different things to different vendors, though. Keep that in mind as you

read VoIP documentation. It also means different things at ...