3Com CoreBuilder 3500, Руководство по внедрению, Страница: 482 / 592

482 C
HAPTER
17: Q
O
S
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RSVP
Key Guidelines for
Implementation
Consider the following guidelines when you configure QoS on your
system.
Procedural Guidelines Configure classifiers and controls in the following order:
1 Define a classifier, or choose a predefined classifier. Identify a particular
type of traffic that you want to regulate and define a classifier for this
traffic via the Administration Console or the Web Management Traffic
Policy Wizard. The rules for defining classifiers are different for flow
versus nonflow classifiers.
2 Create a control to apply to the classifier(s) you defined. The control
enables the system to direct the traffic to one of the available transmit
queues or drop the traffic. As part of defining a control, you can:
a Assign a rate limit to the incoming classified traffic (optionally, on a
per-port basis).
b If you specify a rate limit, define what should be done with the
nonconforming excess (traffic that exceeds the rate-limit parameters).
c Apply an IEEE 802.1p priority tag value to forwarded traffic.
General Guidelines
■
You must define a classifier before you can assign a control to it.
■
A classifier does not affect traffic scheduling until you configure a
control for that classifier.
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Traffic that is not classified and controlled is treated with a transmit
priority of best (best effort) using the default classifier (499) and
control (1). In this case, all packets are conforming packets.
■
You cannot remove or modify the default classifier
(499).
■
You cannot remove the default control (1) , but you can modify it.
■
When you specify a TCP or UDP port range for a flow classifier, limit
the range as much as possible (for example, to a single TCP or UDP
port or a small range of ports). If the classifier applies to a wide range
of TCP or UDP ports, you increase the amount of classified traffic on
the system and consume valuable QoS resources (cache entries).
■
If you have defined a control and you want to remove or modify the
associated classifier, you must remove the control before you can
remove or modify the classifier.