Features Page 165 of 910
IP Line Description, Installation and Maintenance
4The NAT device sees that the IP Phone’s UDP connection is not active in the
transmit direction and starts aging the translation.
5Depending on the length of time the call is muted and the duration of the NAT’s
translation aging timeout value, the NAT device might time-out the translation and
drop the connection.
6All packets coming from the far end are dropped by the NAT device.
7When mute is cancelled, the IP Phone starts transmitting again.
8NAT considers this to be a new connection and creates a new translation. NAT
sends data to the far end using this new translation, resulting in half-duplex voice
connection between the IP Phone and the far-end device.
9Data sent to the far end device gets there but the data coming back is lost.
Solution
1The IP Phone periodically sends an extra non-RTP packet to the far end to keep
the NAT translation alive, ensuring that the NAT’s session time-out does not
expire.
2The non-RTP packet is constructed to fail any RTP validation tests so it is not
played out by the far-end device (IP Phone or gateway channel.
Table 26
Mute process (Part 2 of 2)
Description