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378
ITG Engineering Guidelines
553-3001-202 Standard 1.00 April 2000
Other measurement considerations
The statistics described above measure the intranet prior to ITG
installation, which means that the measurement does not take into
consideration the expected load offered by the ITG users.
If the intranet capacity is tight and the ITG traffic significant, you should
consider making intranet measurements under load. Load can be applied
using traffic generator tools; the amount of load should match the ITG offered
traffic estimated in “ITG traffic engineering” on page 76.
Obtain QoS measurement tools
and are standard IP tools that are usually included with
a network host's TCP/IP stack. A survey of QoS measurement tools and
packages (including commercial ones) can be found in the home page of the
Cooperative Association for Internet Data Analysis (CAIDA) at
http://www.caida.org
. Some of these are delay monitoring tools that include
features like timestamping, plotting, and computation of standard deviation.
Decision: does the intranet meet expected ITG QoS?
At the end of this measurement and analysis, you should have a good
indicator whether the corporate intranet as it stands can deliver adequate
voice and fax services. Looking at the "Expected QoS level" column in
Figure 20, the craftsperson can gauge the QoS level for each site pair.
In order to offer voice and fax services over the intranet, the technician should
keep the network within a "Good" or "Excellent" QoS level at the Mean+σ
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 being “Good”,
the technician will need to evaluate the options and costs for upgrading the
intranet. Using Appendix A, the technician can estimate the amount of
one-way delay that needs to be reduced to raise the QoS level. “Fine-tune
Network QoS” on page 119 provides guidelines for reducing one-way delay.
Often this involves a link upgrade, a topology change, or implementation of
QoS in the network.