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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 reser ved 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
Copyright © 2007, Nortel Networks
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