Configuring Qos; Qos Transition Recovery - Nortel RLC Installation And Administration Manual

June 2005

Configuring QoS

This section shows you how to configure the RLC with quality and duration
values for Nortel's patented QoS Transitioning Technology.
QoS Transitioning Technology allows you to define acceptable voice QoS for
Remote Gateway 9100 Series telephone calls routed using Voice over Internet
Protocol (VoIP). The Signal Degrade slide control allows you to set the point
where poor voice QoS causes the RLC to transition calls to the PSTN for better
QoS. The Signal Recover slide control identifies the IP voice QoS level where
you want the RLC to recover calls to the IP network.
You can also define the following duration parameters:
The degrade duration is the time (in seconds) that QoS must remain below
the degrade threshold before the RLC transitions calls to the PSTN.
The recover duration is the time (in minutes) that QoS must remain above
the recover threshold before the RLC recovers the call to the IP network.
The units of the acceptable duration for recovery are minutes rather than seconds
in an attempt to minimize transition thrashing. Transition thrashing is the rapid
transition and recovery between networks. This can occur when QoS hovers
around configured degrade and recover thresholds. This phenomenon produces
higher than normal PSTN charges.
Note: QoS problems can sometimes be addressed through prioritization of voice
packets. For more information, refer to "QoS on shared networks" on page 19.

QoS transition recovery

Due to the requirement for on-demand router support, the IP network is not
continually tested during QoS transition situations. It is tested only when there
are active voice calls over the PSTN. As a result, transitioning needs active calls
for the user-configured recovery period in order to switch back to the IP
network.
RLC Installation and Administration Guide
Configuring the RLC
211