Nortel Networks NN43001-563 Set ITG QoS objectives

Post-installation network measurements 165

expectations and networking technology – can render a design obsolete or

non-compliant with QoS objectives. Review the design periodically against

prevailing and trended network conditions and trafﬁcpatter ns, at least once

every two to three weeks initially,then eventually on a quarterly basis.

It is assumed that the customer’s organization already has processes in

place to monitor, analyze,and re-design both the system network and the

corporate intranet, so that both networks continue to conform to internal

QoS standards. When operating VoIP services, the customer’s organization

needs to incorporate additional monitoring and planing processes, as

follows:

•Collect, analyze, and trend IP Trunk3.01 (and later) trafﬁc patter ns.

•Monitor and trend one-way delay and packetloss.

•Performchanges in IP Trunk3.01 (and later) and intranet when planning

thresholds are reached.

By instituting these new processes, the IP Trunk3.01 (and later) network

can be managed to ensure that desired QoS objectives are always met.

Set ITG QoS objectives

State the design objective of the IP Trunk3.01 (and later) network. This sets

the standard for evaluating compliance to meeting users’ needs. When

the IP Trunk3.01 (and later) network is ﬁrst installed, the design objective

expectations havebeen set, based on the work done in "Measure intranet

QoS" (page 139). Initially, set the QoS objective so that for each destination

pair, the mean+s of one-way delayand packet loss is below some threshold

value to maintain calls between those two sites at a required QoS level. The

graphs of Figure 29 "QoS level with G.711 codec" (page 142) and Figure

30 "QoS level withG.723 codec" (page 143), with the QoS measurements,

help determine what threshold levels are appropriate.

Table34 "ITG QoS objectives" (page 165) describes examples of IP Trunk

3.01 (and later) QoS objectives.

Tabl e 34

ITG QoS objectives

Site Pair IP Trunk 3.01 (and later) QoS objective

Fallback

threshold

setting

Santa Clara/

Richardson Mean (one-way delay) + σ(one-way delay) < 120 ms

Mean (packet loss) + σ(packet loss) < 0.3% Excellent

Santa Clara/

Ottawa Mean (one-way delay) + σ(one-way delay) < 120 ms

Mean (packet loss) + σ(packet loss) < 1.1% Excellent

Nortel Communication Server 1000

IP TrunkFundamentals

NN43001-563 02.01 Standard

Release 5.5 21December 2007