Overview - Allied Telesis AT-8100L/8 User Manual

Chapter 102: QoS Storm Control Protection

Overview

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The QoS Storm Control Protection (QSP) feature uses QoS mechanisms
to classify traffic that is likely to cause a packet storm, which can consist of
broadcast, multicast, or unicast traffic, and decide which action to take
when a packet storm occurs. Without QSP, the per-port storm protection
mechanism discards traffic that exceeds the configured limit. However,
with QSP, the following actions are possible when a storm is detected:
 Removes a port from a VLAN
 Shuts down a port on the switch
 Disables the port in software
In addition to determining the action taken when a packet storm occurs,
the storm control commands allow you to determine:
 The length of time the port remains disabled after a packet storm

The data rate that triggers the storm control action

The frequency at which traffic is measured
This is a policy-based feature. As a result, you must configure a class map
(or multiple class maps) that identifies the broadcast, multicast, or unicast
traffic and assign it to a policy map before setting the storm control
commands. For instructions, see "Creating a Policy Map" on page 1652
and "Creating a Class Map" on page 1645.
One example of how the QSP commands work in conjunction with the
QoS policies is the method of assigning a policy map to a port. This
association is accomplished with the SERVICE-POLICY INPUT
command. (See "Assigning a Policy Map to a Port" on page 1653.) The
same port is affected by the setting for the storm control action if a packet
storm occurs.
In addition, the setting of the MATCH commands within the class maps
helps to determine what type of traffic triggers the storm control action. For
instance, the MATCH DSCP command contained within a class map
determines that the storm control settings affect specified DSCP traffic
during a packet storm. This setting is used in combination with the data
rate setting when the DSCP traffic reaches the configured data rate.
Consequently, the storm control action only applies when DSCP traffic
reaches the data rate. If other types of traffic exceed the data rate, the
storm control action is not triggered. (For a list of the MATCH commands,
see "Filtering Incoming Traffic" on page 1645.)