Evaluating Your Network - Nortel Remote Gateway 9110 Reference Manual

Standard 1.6

Evaluating your network

Now that you fully understand the effects of packet loss, jitter, and delay on the
audio quality that can be experienced on packetized voice equipment, the next
step is to ensure that the network is capable and configured to support
packetized voice.
A network is a dynamic entity – the characteristics change daily, hourly, by the
second as various applications push and pull data across it. The method of
evaluation best suited for packetized voice is testing with pseudo voice traffic
for extended periods of time.
There are numerous Personal Computer (PC) based software tools available that
generate a configured number of calls, using a specific Codec, for a configured
duration. The tool then provides various reports showing the jitter, packet loss,
and the equivalent audio quality (MOS or R-value). You can and should use this
tool before installing the VoIP equipment. You should run tests for an extended
period of time.
To ensure success, network evaluation is a critical step in engineering a VoIP
solution. Do not skip this critical step, as it is the foundation for the projects
success.
Nortel can provide network evaluation services, either directly or through our
business partners.
Network engineering for real time traffic
Packetized voice, or VoIP, is a form of real time traffic where delays and
retransmission cannot be tolerated. Typical PC and server traffic is non-real time
and, therefore, can tolerate a certain level of delay and retransmission. To ensure
that the VoIP traffic receives the most expedited treatment possible, there are a
number of techniques that you can use.
Let's look at the various techniques starting at the VoIP devices themselves and
working out into the Local Area Network (LAN) or Wide Area Network
(WAN).
Remote Gateway 9100 Series Network Engineering Guidelines
June 2005
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