Chapter 8
| Congestion Control
Automatic Traffic Control
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â—† When traffic exceeds the alarm fire threshold and the apply timer expires, a
traffic control response is applied, and a Traffic Control Apply Trap is sent and
logged.
◆ Alarm Clear Threshold – The lower threshold beneath which a control response
can be automatically terminated after the release timer expires. When ingress
traffic falls below this threshold, ATC sends a Storm Alarm Clear Trap and logs it.
â—† When traffic falls below the alarm clear threshold after the release timer
expires, traffic control (for rate limiting) will be stopped and a Traffic Control
Release Trap sent and logged. Note that if the control action has shut down a
port, it can only be manually re-enabled using Manual Control Release (see
page 237).
â—† The traffic control response of rate limiting can be released automatically or
manually. The control response of shutting down a port can only be released
manually.
Figure 131: Storm Control by Shutting Down a Port
The key elements of this diagram are the same as that described in the preceding
diagram, except that automatic release of the control response is not provided.
When traffic control is applied, you must manually re-enable the port.
Functional Limitations
Automatic storm control is a software level control function. Traffic storms can also
be controlled at the hardware level using Port Broadcast Control or Port Multicast
Control (as described on page 232). However, only one of these control types can
be applied to a port. Enabling automatic storm control on a port will disable
hardware-level storm control on that port.
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