Nortel Networks NN43001-563 - Manual (Page 153)

Measure intranet QoS 153
To calculate R = 94 - lc - ld - lp, use Table 29 "Impairment factors of codecs"
(page 149) , Table 30 "Impairment factors due to network delay" (page 149) ,
and Table 31 "Impairment factors due to packet loss" (page 149) :
• G.711 codec: lc = 11
• 20 msec network delay: ld = 5
• 0.5% packet loss: lp = 8
Then:
R = 94 - 11 - 5 - 8
R = 70
Using Table 33 "IP Trunk 3.01 (and later) QoS levels" (page 150) , a value of
70 means some users are dissatisfied.
Does the intranet meet expected IP Trunk 3.01 (and later) QoS?
At the end of this measurement and analysis, there should be a good
indication if the corporate intranet in its present state can deliver adequate
voice and fax services. Looking at the "Expected QoS level" column in
Table
28 "Sample measurement results for G.729A codec" (page 147) , the QoS
level for each site pair can be gauged.
In order to offer voice and fax services over the intranet, keep the network
within a "Good" or "Excellent" QoS level at the Mean+s operating region.
Fax services should not be offered on routes that have only "Fair" or "Poor"
QoS levels.
If the expected QoS levels of some or all routes fall short of "Good", evaluate
the options and costs for upgrading the intranet. Estimate the amount of
one-way delay that must be reduced to raise the QoS level. The section
"Fine-tune network QoS" (page 133) provides guidelines for reducing
one-way delay. Often this involves a link upgrade, a topology change, or
implementation of QoS in the network.
A decision can be made to keep costs down and accept a temporary "Fair"
QoS level for a selected route. In that case, having made a calculated
trade-off in quality, carefully monitor the QoS level, reset expectations with
the end users and be receptive to user feedback.
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
.