A single CAR rate policy includes information about the rate limit, conform actions, and exceed actions. Each interface can have multiple CAR rate policies corresponding to different types of traffic. For example, low-priority traffic might be limited to a lower rate than high-priority traffic. When multiple rate policies exist, the router examines each policy in the order entered until the packet matches. If no match is found, the default action is to send.
Rate policies can be independent or cascading:
Independent— Each rate policy deals with a different type of traffic.
• Cascading— A packet might be compared to multiple different rate policies in succession.
Cascading of rate policies supports a series of rate limits to be applied to packets to specify more granular policies. For example, total traffic could be rate limited on an access link to a specified subrate bandwidth and then rate limit World Wide Web traffic on the same link to a given proportion of the subrate limit.
Match packets could be rate limited against an ordered sequence of policies until an applicable rate limit is encountered. For example, as the sequence of policies is applied, the rate limiting of several MAC addresses with different bandwidth allocations can occur at an exchange point.
Up to 100 rate policies can be configured on a subinterface.
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