Nortel Networks NN43001-563 User Manual

Page 109

Factors that effect the real-time capacity

109

Media Card 32-port trunk card Leader 0 and DCHIP card real-time
capacity

The Media Card 32-port trunk card is based on the Intel StrongARM CPU.
The real-time capacity analysis of the Media Card 32-port Leader 0 card is
as follows. The following assumptions are made:

1. The minimum number of Follower cards required is a function of the call

rate (which is limited by the Leader and DCHIP card) and the Average
Hold Time (AHT) (which is a function of the number of channels per
card). The number of Follower cards is calculated by the number of
voice channels required (using Poisson 1 percent blocking Grade of
Service) divided by the number of channels per card. The number of
Follower cards required is affected by whether the Leader card has
the voice channels enabled or not.

2. Peakedness factor for call processing is equal to 1.3. This implies that

30% fluctuation is allowed in voice traffic.

3. Calls can terminate or originate on the Leader card. Voice ports are

allowed on the Leader card, depending on configuration for anticipated
traffic. Enabling the voice ports on a Leader or DCHIP card decreases
the number of Follower cards required by one card, but can substantially
affect the amount of traffic that can be handled for that node.

4. When VAD has been enabled in TM 3.1, the voice fluctuation factor

is equal to 1.5. A voice fluctuation factor of 1.5 implies that, during a
conversation, voice is on 50% more than the average, in contrast to
silence periods of a conversation. With VAD status equal to "off", the
voice fluctuation factor is equal to 1.1.

5. 15% of CPU real-time has been reserved for Network Monitoring

Module.

6. Gatekeeper-routed calls create a higher load on the card.

7. The values in the tables are valid for all Voice codecs and voice sample

size including G.711, 10 ms voice sample.

Recommendation

Nortel recommends that traffic on a single card Media Card 32-port trunk
card node never exceed the following:

• 4000 calls/hour – Gatekeeper-routed

• 5500 calls/hour – non-Gatekeeper-routed

In a multi-card node, the various roles necessary in processing calls,
such as Leader card, DCHIP card, and Follower card, can be divided

Nortel Communication Server 1000

IP Trunk Fundamentals

NN43001-563

01.01

Standard

Release 5.0

30 May 2007