Nortel Networks NN43001-563 - Manual (Page 105)

Factors that effect the real-time capacity 105
In a default QoS configuration, the Leader card must terminate and generate
a total of 50 probe packets per QoS-enabled ITG Trunk 2.x/IP Trunk 3.01
(and later) node every 15 seconds. These extra packets generated and
received use real-time capabilities that would otherwise be used for call
processing. If the number of nodes in a network that is being monitored
exceeds the capabilities of the Leader card, implement other VoIP QoS
methods.
For more information, see "Implement QoS in IP networks" (page 127) .
Endpoint type
The endpoint type has no effect on real-time capacity for calls already
established. The real-time capacity of the card is affected during call setup
for Outgoing calls that use a Gatekeeper. Each outgoing call that uses a
Gatekeeper sends an extra message, the ARQ message, to resolve a dialed
number to a destination IP address. On a properly configured IP Trunk 3.01
(and later) node, this does not limit the capabilities of the node, because the
outgoing call uses a Follower card which has more then sufficient resources.
The Average Hold Time (AHT) and distribution of incoming calls
The customer’s call flow impacts the real-time engineering considerations of
IP Trunk 3.01 (and later) in three ways, as follows:
1. Total active voice call time (CCS calculation):
If the active voice call time is lower, the call rate might be higher.
2. The nature of call establishment and termination:
Multiple simultaneous call setup/teardown events (less then half a
second between call setups across multiple ports) have a significant
impact on the peak CPU utilization of IP Trunk cards, especially in
multi-card nodes where the DCHIP card communication is across the
local IP LAN.
3. Call direction:
The IP Trunk Leader card real-time is impacted more on the
call-terminating side than the call-originating side. However, the relative
difference between terminating and originating IP trunk card CPU
utilization is also call-profile dependent. This can vary from 20% less
overhead on call origination to 0% less overhead.
Recommendation
Nortel recommends that if an IP Trunk 3.01 (and later) node has a mixture of
Media Card 32-port trunk cards and ITG-Pentium 24-port trunk cards, ensure
that the Leader 0 card is an ITG-Pentium 24-port trunk card. Additionally, in a
mixed-card node, the DCHIP card should be an ITG-Pentium 24-port trunk card.
The Media Card 32-port trunk card can be used as a Leader or DCHIP card
when the node contains all Media Cards 32-port trunk cards.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.