Nortel Networks NN43001-563 User Manual download pdf (Page 165)

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 trafﬁc patterns, 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 Trunk 3.01 (and later) trafﬁc patterns.

•

Monitor and trend one-way delay and packet loss.

•

Perform changes in IP Trunk 3.01 (and later) and intranet when planning

thresholds are reached.

By instituting these new processes, the IP Trunk 3.01 (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 Trunk 3.01 (and later) network. This sets

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

the IP Trunk 3.01 (and later) network is ﬁrst installed, the design objective

expectations have been 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 delay and 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 with G.723 codec" (page 143), with the QoS measurements,

help determine what threshold levels are appropriate.

Table 34 "ITG QoS objectives" (page 165) describes examples of IP Trunk

3.01 (and later) QoS objectives.

Table 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 Trunk Fundamentals

NN43001-563 02.01 Standard

Release 5.5 21 December 2007

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