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140 ITG engineering guidelines
Use the ESN TGAR, NCOS, and facility restriction levels to keep general
modem traffic off the IP Trunk 3.01 (and later) route.
Measure intranet QoS
End-to-end delay and error characteristics of the current state of the
intranet can be measured. These measurements help set acceptable QoS
standards when using the corporate intranet to transmit voice services.
QoS evaluation process overview
There are two main objectives when dealing with the QoS issue in an IP
Trunk 3.01 (and later) network:
1. to predict the expected QoS
2. to evaluate the QoS after integrating IP Trunk 3.01 (and later) traffic
into the intranet
The process for either case is similar; one is without IP Trunk 3.01 (and
later) traffic and one is with. The differences are discussed in this section.
In the process, it is assumed that the PING program is available on a PC, or
some network management tool is available to collect delay and loss data
and access the TLAN subnet that connects to the router to the intranet.
1. Use PING or an equivalent tool to collect round-trip delay (in ms) and
loss (in%) data.
2. Divide the delay by 2 to approximate one-way delay. Add 93 ms to
adjust for ITG processing and buffering time.
3. Use a QoS chart, or Table 33 "IP Trunk 3.01 (and later) QoS levels"
(page 150) on Table 33 "IP Trunk 3.01 (and later) QoS levels" (page
150), to predict the QoS categor ies: excellent, good, fair or poor.
4. If a customer wants to manage the QoS in a more detailed fashion,
re-balance the values of delay compared to loss by adjusting IP Trunk
3.01 (and later) system parameters, such as preferred codec, payload
size, and routing algorithm, to move resulting QoS among different
categories.
5. If the QoS objective is met, repeat the process periodically to make sure
the required QoS is maintained.
Set QoS expectations
The users of corporate voice and data services expect these services to
meet some perceived QoS, which in turn influences network design. The
goal is to design and allocate enough resources in the network to meet
users’ needs. QoS metrics or parameters are what quantifies the needs of
the "user" of the "service".
Nortel Communication Server 1000
IP Trunk Fundamentals
NN43001-563 01.01 Standard
Release 5.0 30 May 2007
Copyright © 2007, Nortel Networks
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