Using tools
already available in Cisco IOS Software, these solutions help provide proactive mitigation solutions.
Committed Access Rate (CAR)
CAR is a multifaceted feature that embodies a rate-limiting feature for policing traffic, in addition to its packet
classification and marking feature. CAR can be used to mark packet streams, for example, setting different IP
precedence for selected packets entering or exiting the network. As the packet traverses through the network,
devices within the path can then use the adjusted IP precedence to determine how to treat the marked traffic.
The policing feature of CAR controls the maximum rate of traffic sent or received on an interface (bandwidth
management) for a network specifying traffic handling policies, when the traffic either conforms to or exceeds
the specified rate limits. This is achieved by ensuring that traffic falling within specified rate parameters is sent;
however, packets that exceed the acceptable amount of traffic are dropped or sent with a different level of
priority. By default, the action for traffic exceeding the specified rate limits is to drop or mark down packets.
Simple techniques such as CAR sometimes produce the best results.
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