Nortel Networks 9150 - Manual (Page 109)

Remote Gateway 9150 Installation and Administration Guide 79
January 2005 Planning for Remote Gateway 9150 unit installation
Refer to “RLC connection configuration” on page 198 for the correct
procedures.
Translation tables within NAT routers control the communication path from the
private network to the public network. Most NAT devices contain timers that
monitor the translation table entries. Each time the device uses a translation table
entry, the timer restarts. Individual table entries are deleted if the
communications path is not used and the timer expires.
It is possible, when using a Remote Gateway 9150 unit behind a NAT device,
that prolonged periods of silence cause the NAT translation table entries to clear
and drop the audio path. An example of this would be a remote user listening to
a conference call with the user’s digital telephone set on mute. After five
minutes (the default NAT translation table timer on many NAT routers) the
remote user would not be able to hear the conference. To restore the NAT table
entry and recover the audio path, the remote user could go off mute and speak
into the digital telephone set.
To prevent the NAT translation table from dropping the audio path:
!
configure the translation tables on the NAT router with a large timer value
(for example, two hours)
!
configure a static translation table entry for UDP port 20480
Implementing QoS Transitioning Technology
When the QoS Transitioning Technology is implemented, calls transition:
!
to the PSTN when IP QoS degrades
!
back to the IP network when IP QoS returns to normal
To implement QoS Transitioning Technology:
1 To implement the QoS Transitioning Technology, you must understand
what your IP network is doing, such as
!
when the busy times are on the network
!
how much traffic is processed (during normal and busy traffic periods)
!
how to evaluate and adjust your network’s QoS