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Switching to VoIP
book

Switching to VoIP

by Theodore Wallingford
June 2005
Intermediate to advanced
502 pages
21h 48m
English
O'Reilly Media, Inc.
Content preview from Switching to VoIP
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
Dial-Plan and PBX Design
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91
or voice mail port, but most don’t. Fortunately, VoIP is not as geared around exten-
sion numbers as legacy PBX systems are.
Extensions just because
Some users may request a particular extension because it’s the extension number
they had on their former employer’s system or because it’s easy to remember. Other
extension numbers may be baggage from generations of phone system upgrades.
There may even be a hodgepodge of geography or legacy issues and special number
requests cluttering your dial-plan today, before you’ve even had a chance to add
VoIP to the dial-plan mix. Fortunately, VoIP networks can be eminently more pro-
grammable than the old PBX system.
Dial-Tone Trunks
Dial-tone trunks are the PSTN pathways of a PBX. Outbound or PSTN-bound traffic
flows to the dial-tone trunks, and inward traffic flows across them to the PBX. Tradi-
tional dial-tone trunks can be POTS, Centrex, BRI channels, or PRI DS0 channels.
Chapter 12 discusses the impact of voice applications on the selection
of PSTN trunk technologies and sizing.
It could make sense to have a very large dial-tone trunk group to make sure the rest
of the world never gets a busy signal when calling in to your phone system. But the
cost of phone lines—or T1 circuits—adds up quickly. There’s an easy ...
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Publisher Resources

ISBN: 0596008686Catalog PageErrata