Switching to VoIP

This is the Title of the Book, eMatter Edition

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

The power went out and so did all the phones

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Calls across a wide area call path have dropouts in the audio

As a rule, this means that the latency or jitter on the call path’s route is a problem. If

the wide area link in question is used for voice and data, use routers that support IP

precedence to promote VoIP over non-VoIP traffic. If the link is running at capacity,

consider increasing its capacity or using a bandwidth-reservation QoS measure

across the link. Also, make sure that, for call paths that have limited bandwidth, calls

are selecting a thrifty codec (not G.711).

You and your caller find yourself interrupting each other a lot

This problem is either caused by latency on the call path or poor conversational

manners. Most often, latency is the culprit. Do what you can to decrease latency on

this call path. Are you using a small packet interval? What about packet-loss conceal-

ment? Do you need to be using it? What about jitter buffering? How fast is the link?

Is the call path a VPN? All of these things contribute to latency.

When a caller begins to speak, you can’t hear the first word or two of his

sentences

Normally, this problem is caused by poor silence suppression techniques. Silence

suppression conserves bandwidth by not transmitting sound frames during periods

of silence. ...