Nortel Networks NN43001-314

Adaptive Network Bandwidth Management 71

to another Call Server, the availablebandwidth 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 availableto

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 newcalls. 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 zonein thenetwork. 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 Ser versare added to the network, it is not necessar y

to re-provision all the other Call Servers on the network to takeinto 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 Gateway50.

Nortel Communication Server 1000

Branch Ofﬁce Installation and Commissioning

NN43001-314 01.02 Standard

Release 5.0 20June 2007