Nortel Networks SRG 50 NN43001-307 - Manual (Page 96)

96 Bandwidth Management
IP Peer Networking supports the per-call selection of codec standards,
based on the type of call (interzone or intrazone). IP Peer Networking
supports the following codecs (with supported payload sizes in parentheses,
with the default value in bold):
• G.711 A/mu-law (10 ms, 20 ms, and 30 ms)
• G.729 A (10 ms, 20 ms, 30 ms, 40 ms, and 50 ms)
• G.729 AB (10 ms, 20 ms, 30 ms, 40 ms, and 50 ms)
• G.723.1 (30 ms) (though it can limit the number of DSP channels
available)
SRG 50 does not support G.723 codec.
• T.38 for fax
ATTENTION
The G.XXX series of codecs are standards defined by the International
Telecommunications Union (ITU).
By default, the G.711 codec must be supported at both ends of a call.
Codec configuration is performed for each node and is independent of the
signaling gateway that is used on the node.
The payload size on the CS 1000 must be set to 30 msec in order to work
with the SRG.
IP Peer Networking performs codec negotiation by providing a list of codecs
that the devices can support. Use CS 1000 Element Manager to configure
the list of codec capabilities. See IP Peer Networking Installation and
Commissioning (NN43001-313) for instructions on configuring codecs.
The codec preference sequence sent over SIP/H.323 depends on the
bandwidth policy selected for the Virtual Trunk zone and the involved
telephones. For “Best Quality”, the list is sorted from best to worst voice
quality. For Best Bandwidth, the list is sorted from best to worst bandwidth
usage.
The G.711 codec delivers “toll quality” audio at 64 kbit/s. This codec is
optimal for speech quality, as it has the smallest delay and is resilient to
channel errors. However, the G.711 codec uses the largest bandwidth.
The G.729A codec provides near toll quality voice at a low delay. The
G.729A codec uses compression at 8 kbit/s. The G.729AB codec also
uses compression at 8 kbit/s.
The G.723.1 codec provides the greatest compression.
Nortel Communication Server 1000
Main Office Configuration Guide for SRG 50
NN43001-307 02.02 Standard
Release 5.0 3 December 2007
Copyright © 2005-2007, Nortel Networks
.