Nortel Networks NN43001-563 Endpoint type, The Average Hold Time (AHT) and distribution of incoming calls

Factors that effectthe real-time capacity 105

In a defaultQoS conﬁguration,the Leader card must ter minate and generate

a total of 50 probe packets per QoS-enabled ITG Trunk2.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 VoIPQoS

methods.

For more information, see "Implement QoS in IP networks" (page 126).

Endpoint type

The endpoint type has no effect on real-time capacity forcalls 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 extramessage, 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 Trunk3.01 (and later) in three ways, as follows:

1. Totalactive voice call time (CCS calculation):

If the active voicecall 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 TrunkFundamentals

NN43001-563 02.01 Standard

Release 5.5 21December 2007