Nortel VoIP Gateway, Руководство по настройке

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188 Measuring Intranet QoS
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Notice from the Ping output the difference of rtt. The repeated sampling of rtt allows you to
receive a delay characteristic of the intranet. To get a delay distribution, include the Ping tool in a
script which controls the frequency of the Ping probes, which timestamps and stores the samples in
a raw data file.
The file can be analyzed by the administrator using spreadsheets and other statistics packages. The
installer can check if the intranet network management software has any delay measurement
modules which can cause a delay-distribution measurement for specific site pairs.
Delay characteristics vary depending on the site pair and the time of day. The evaluation of the
intranet includes taking delay measurements for each site pair. If there are important changes of
traffic in the intranet, include some Ping samples during the peak hour. For a more complete
evaluation of the intranet delay characteristics, get Ping measurements over a period of at least a
week.
Measuring end-to-end packet loss
The
Ping
program also reports if the packet made its round trip correctly. Use the same
Ping
host
setup to measure end-to-end errors. Use the same packet size.
Sampling error rate, require taking multiple
Ping
samples (at least 30). An accurate error
distribution requires data collection over a greater period of time. The error rate statistic from
multiple
Ping
samples is the packet loss rate.
Recording routes
As part of the network evaluation, record routing information for all source destination pairs. Use
the Traceroute tool to record routing information. A sample of the output of the Traceroute tool
follows:
C:\WINDOWS>tracert 10.10.10.15
Tracing route to 10.10.10.15 over a maximum of 30 hops:
1 3 ms 1 ms <10 ms tftzraf1.ca.nortel.com [10.10.10.1]
2 1 ms 1 ms 1 ms 10.10.10.57
3 7 ms 2 ms 3 ms tcarrbf0.ca.nortel.com [10.10.10.2]
4 8 ms 7 ms 5 ms bcarha56.ca.nortel.com [10.10.10.15]
Trace complete.