Nortel Networks NN43001-314 - Manual (Page 71)

Adaptive Network Bandwidth Management 71
to another Call Server, the available bandwidth is reduced automatically
between those two zones. When the QoS between the two zones improves,
then the bandwidth limit is allowed to return to normal.
When an IP Phone encounters degradation of the network, it informs the
Call Server through various QoS alarms. These QoS alarms (packet loss,
jitter, delay, and, for phase 2 IP Phones, R value) get reported to the Call
Server. Depending upon the rate of the incoming alarms and the value of
the alarms, the Call Server reduces the available bandwidth available to
make new calls. The Call Server will lower/limit the number of new calls
allowed, based on the available bandwidth. This prevents excessive calls
being placed on a network with limited bandwidth (resulting in poor voice
quality). Once the adjusted (lowered) bandwidth reaches its full capacity,
new calls are either routed to an alternate route (if available), using Network
Alternate Routing Service (NARS) or the Alternative Routing for NBWM
feature, or new calls are blocked. The Call Server continues to monitor the
network throughout the network degradation period. When the degradation
is removed or the performance of the network improves, the allowable
bandwidth returns to provisioned levels and the Call Server gradually starts
allowing new calls.
Essentially, Adaptive Network Bandwidth Management provides a fallback to
PSTN on QoS degradation for new calls. As a result, bandwidth is managed
and quality measured between all the zones across the entire network, and
when necessary corrective action is taken. Due to the real-time interaction
with the network, less maintenance is required for the network since the
system reacts automatically to network conditions.
With Adaptive Network Bandwidth Management, it is not necessary to
provision bandwidth parameters between every zone in the network. Rather,
the Call Server automatically learns of new zones in the network and applies
Adaptive Network Bandwidth Management to these new zones as required.
Therefore, as new Call Servers are added to the network, it is not necessary
to re-provision all the other Call Servers on the network to take into account
this new Call Server. Conversely, when Call Servers are removed from the
network, the remaining Call Servers age out the old Call Server information
and therefore, provide only up to date bandwidth information.
This feature operates between all IP Peer CS 1000 systems, including the
Media Gateway 1000B and Survivable Remote Gateway 50.
Nortel Communication Server 1000
Branch Office Installation and Commissioning
NN43001-314 01.02 Standard
Release 5.0 20 June 2007
Copyright © 2007, Nortel Networks
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