Dual-rate class-based policing was introduced in Cisco IOS 12.2(4)T. With dual-rate policing, traffic policing can be enforced according to two separate rates: CIR and PIR. The use of these two rates can be specified, along with their corresponding values, by using two keywords, cir and pir, in the police command. The Bc and Be keywords and their associated arguments (conform-burst and peak-burst, respectively) are optional. If Bc is not specified, Bc (in bytes) will default to CIR / 32, or 1500 bytes, whichever is higher. If Be is not specified, Be (in bytes) will default to PIR / 32, or 1500 bytes, whichever is higher.
Example: Dual-Rate Class-Based Policing
Class-Based Policing Example: Dual Rate Class-Based Policing
In the example, dual-rate policing is configured on the HTTP traffic class to limit HTTP traffic to an average committed rate of 500 kbps and a peak rate of 1 Mbps.
Conforming traffic will be sent as-is, traffic exceeding 500 kbps (but not exceeding 1 Mbps) will be marked with IP Precedence 3 and then sent, and all traffic exceeding 1 Mbps will be dropped.
Because the Bc and Be are not specified, the default Bc in bytes will be CIR / 32 (Tc = 0.25 seconds), or 1500 bytes, whichever is higher. The default Be in bytes will be PIR / 32 (Tc = 0.25 seconds), or 1500 bytes, whichever is higher.
In this example, the default Bc = 500,000 / 32 = 15,625 bytes, and the default Be = 1,000,000 / 32 = 31,250 bytes.
The show policy-map command can be used to display the default settings of the Bc and Be parameters, as follows:
Router #show policy-map police-http Policy Map police-http Class silver police cir 500000 bc 15625 pir 1000000 be 31250
conform-action transmit exceed-action set-prec-transmit 3 violate-action drop
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