
Quality of Service 197
IP Telephony Configuration Guide
Decision: does the intranet meet IP telephony QoS needs?
The end of the measurement and analysis is a good indicator of whether the corporate intranet can
deliver acceptable voice and fax services. The Expected QoS level column in the table indicates to
the installer or administrator the QoS level for each site pair with the data.
Repeat this for each site pair. At the end of the measurements, the results are as shown in the
following table.
To provide voice and fax services over the intranet, keep the network within a Good or Excellent
QoS level at the Mean+σ operating area. Fax services must not travel on routes that have Fair or
Poor QoS levels.
If QoS levels of some or all routes fall short of being Good, evaluate options and costs for
upgrading the intranet. The evaluation often requires a link upgrade, a topology change, or
implementation of QoS in the network.
To maintain costs, you can accept a Fair QoS level for the time for a selected route. A calculated
trade-off in quality requires the installer or administrator to monitor the QoS level, reset needs
with the end users, and respond to user feedback.
Table 54 Expected QoS level per site
Destination pair
Measured one-way
delay (ms)
Measured packet loss
(%)
Expected QoS level
Mean Mean+σ Mean Mean+σ Mean Mean+σ
Santa Clara/Richardson Good Good
Santa Clara/Ottawa
Santa Clara/Tokyo
Richardson/Ottawa
Richardson/Tokyo
Ottawa/Tokyo
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