Nortel Networks NN43001-563 - Manual (Page 166)

166 ITG engineering guidelines
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 140) . 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 143) and Figure
30 "QoS level with G.723 codec" (page 144) , with the QoS measurements,
help determine what threshold levels are appropriate.
Table 34 "ITG QoS objectives" (page 166) 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 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.