Switching to VoIP

This is the Title of the Book, eMatter Edition

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

Key Issues: What Can Go Wrong?

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second, independent IP network alongside your existing one. More than just a

VLAN, this network is an operationally independent network that has no bridges to

the other network, and therefore no way of comingling traffic with it.

Why would anybody go to such lengths for VoIP, when the IETF and IEEE have

invested so much time and effort into QoS? That’s a philosophical question that I’ll

leave to you.

If the skeptical decision-maker in your company has the mistaken

impression that all IP telephony sounds about as good as the share-

ware copy of Internet Phone that he used to use with Windows 95,

just give him a call from your Packet8 or BroadVoice service, and ask

how he thinks it sounds. The point is, most people can’t tell the differ-

ence between the sound of an IP phone call and the sound of a land-

line or cell phone call.

Key Issues: What Can Go Wrong?

• Echo is a problem that is exacerbated by latency and the use of hybrid inter-

faces—those that provide VoIP servers with a way of using legacy phone lines.

Avoid latency and legacy phone lines, and you solve the echo problem. If you

can’t avoid them, then use high-quality hybrid interfaces like those available for

Digium’s TDM400P or Intel Dialogic cards. Asterisk users can also enable

aggressive echo ...