Qos Controls; Important Considerations - 3Com corebuilder 3500 Implementation Manual

QoS Controls

Important
Considerations
After you define a classifier, you assign it a control to apply one or more
of the following:
A rate limit (to limit the amount of input bandwidth the classifier uses)
A service level for conforming packets (a transmit priority that maps to
a particular transmit queue)
Whether packets conforming to the rate limit are loss eligible (that is,
discarded instead of queued when transmit queues back up beyond a
threshold)
An IEEE 802.1p priority tag value to apply to forwarded frames
A one-way filter to drop packets used to establish TCP connections
A time range that the QoS control has on the classified traffic
Review the following before configuring controls:
The system predefines controls 1 through 4 for some of the
predefined nonflow classifiers. You can also modify one of these
predefined controls.
There are several ways to create controls for classifiers. You can:
Apply one control to only one classifier.
Apply one control to multiple classifiers.
Assign a rate limit of none to a control and thereby emphasize the
service level and priority tag.
Assign a rate limit type of receivePort or aggregate to the control
and define multiple rate-limit values for different subsets of ports.
Each classifier can have only one control. Therefore, although you can
apply a control to a classifier that has multiple rate-limit values for
subsets of ports, that control can have only one priority specification
(for forwarded frames). You would have to use multiple classifiers to
use different priority levels.
For examples of how controls can be applied to classifiers, see "Examples
of Classifiers and Controls" later in this chapter. For information on
modifying or removing controls, see "Modifying and Removing Classifiers
and Controls" later in this chapter.
QoS Controls 489