Cisco Catalyst 4500 Series Command Reference Manual page 569

Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches
Command History Release
12.2(40)SG
Usage Guidelines
Use the police command to mark a packet with different quality of service (QoS) values based on
conformance to the service-level agreement.
Traffic policing will not be executed for traffic that passes through an interface.
Specifying Multiple Actions
The police command allows you to specify multiple policing actions. When specifying multiple policing
actions when configuring the police command, note the following points:
•
•
Using the Police Command with the Traffic Policing Feature
The police command can be used with Traffic Policing feature. The Traffic Policing feature works with
a token bucket algorithm. Two types of token bucket algorithms are a single-token bucket algorithm and
a two-token bucket algorithm. A single-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.
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
command of the 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:
•
•
•
Token Bucket Algorithm with Two Token Buckets (Refer to RFC 2697)
The two-token bucket algorithm is used when the violate-action is specified in the police 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).
OL-27596 -01
You can specify a maximum of four actions at one time.
You cannot specify contradictory actions such as conform-action transmit and conform-action
drop.
Tokens are updated in the conform bucket. If the previous arrival of the packet was at T1 and the
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
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 (minus the packet size to be limited) is fewer than 0,
the exceed action is taken.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.4.0SG and IOS 15.1(2)SG)
Modification
This command was introduced on Catalyst 4900M and Supervisor
Engine 6E.
police
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