Cisco ISE - Line Card ISE Configuration Manual page 95

Software Configuration of ATM ISE Line Cards for Cisco 12000 Series Routers
You can specify a maximum of four actions at one time.
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You cannot specify contradictory actions such as conform-action transmit and conform-action drop.
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Using the Police Command with the Traffic Policing Feature
The police rate command can be used with the Traffic Policing feature. The Traffic Policing feature
works with a token bucket algorithm. Two types of token bucket algorithms are in Cisco IOS Release
12.1(5)T: a one-token bucket algorithm and a two-token bucket algorithm. A one-token bucket system
is used when the violate-action option is not specified, and a two-token bucket system is used when the
violate-action option is specified.
The token bucket algorithm for the police command that was introduced in Cisco IOS Release 12.0(5)XE
is different from the token bucket algorithm for the police command introduced in Cisco IOS Release
12.1(5)T. For information on the token bucket algorithm introduced in Release 12.0(5)XE, refer to the
Traffic Policing document for Release 12.0(5)XE. This document is available on the New Features for
12.0(5)XE feature documentation index (under Modular QoS CLI-related feature modules) at
www.cisco.com.
The following are explanations of how the token bucket algorithms introduced in Cisco IOS Release
12.1(5)T work.
Token Bucket Algorithm with One Token Bucket
The one-token bucket algorithm is used when the violate-action option is not specified in the police rate
command command-line interface (CLI).
The conform bucket is initially set to the full size (the full size is the number of bytes specified as the
normal burst size).
When a packet of a given size (for example, "B" bytes) arrives at specific time (time "T") the following
actions occur:
Tokens are updated in the conform bucket. If the previous arrival of the packet was at T1 and the
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current time is T, the bucket is updated with (T - T1) worth of bits based on the token arrival rate.
The token arrival rate is calculated as follows:
(time between packets <which is equal to T - T1> * policer rate)/8 bytes
If the number of bytes in the conform bucket B is greater than or equal to 0, the packet conforms
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and the conform action is taken on the packet. If the packet conforms, B bytes are removed from the
conform bucket and the conform action is completed for the packet.
If the number of bytes in the conform bucket B is fewer than 0, the exceed action is taken.
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Token Bucket Algorithm with Two Token Buckets
The two-token bucket algorithm is used when the violate-action option is specified in the police rate
command CLI.
The conform bucket is initially full (the full size is the number of bytes specified as the normal burst
size).
The exceed bucket is initially full (the full exceed bucket size is the number of bytes specified in the
maximum burst size).
The tokens for both the conform and exceed token buckets are updated based on the token arrival rate,
or committed information rate (CIR).
When a packet of given size (for example, "B" bytes) arrives at specific time (time "T") the following
actions occur:
police rate
Cisco IOS Release 12.0(27)S
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