Avaya Nortel Communication Server 1000 Manual page 120

120 Features
NAT Mapping Keep Alive
The normal operation of the LTPS and the IP Phone requires the LTPS to
send a periodic Watchdog Reset UNIStim message. This message resets
the hardware watchdog timer running on the IP Phone and specifies the
period for the timeout. If the LTPS does not send the Watchdog Reset
message before the watchdog timer expires, the IP Phone resets and
begins a new registration cycle with the LTPS.
To avoid loss of the IP connection, the NAT Mapping Keep Alive function
sends the Watchdog Reset message more frequently. Default values are
recommended. However, if it is necessary to increase the frequency of the
Reset Watchdog message, increase the NAT Mapping Keep Alive timer
value.
NAT Traversal can be configured to provision the length of time the audio
and signaling port mapping is refreshed. This configuration can be done
in Element Manager, on the Call Server in LD 117, or in TM through a
window to the Call Server.
By default, all IP Phones behind a NAT device have the signaling and
audio path kept alive. The default value is 30 seconds. The value can be
decreased to 20 seconds or increased to 600 seconds.
Mute and Hold considerations
IP Line software has two special situations when interworking with NAT:
Mute and Hold.
Mute
Table 29 "Mute process" (page 120)
Table 29
Mute process
Description
Problem
1 When a user enables Mute, the LTPS sends a Mute Transmit (Tx) command to the IP
Phone. That command forces the IP Phone to generate silence in the transmit direction.
2 If the IP Phone is using an evocator that implements silence suppression, for example
G.729AB, the IP Phone sends one silence frame to the far end, and then stops sending
any further frames until Mute is cancelled.
3
Data sent from the IP Phone stops.
4 The NAT device sees that the IP Phone UDP connection is not active in the transmit
direction and starts aging the translation.
Copyright © 2003–2008, Nortel Networks
.
Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
describes the Mute process.