CAR

From: Darrin K. Pierce (darrin@dkpierce.com)
Date: Thu Feb 22 2007 - 02:29:55 ART


In reference to Committed Access Rate (CAR) feature:

How is the burst-normal and burst-max determined?

To configure CAR policy on an interface:
Router(config-if)# rate-limit {input | output} [dscp dscp-value]
[access-group [rate-limt] acl-index] bps burst-normal burst-max
conform-action conform-action exceed-action exceed-action

The recommendations on Doc CD Command References
"http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hqos_
r/qos_q1h.htm#wp1080850"

When policing traffic with CAR, Cisco recommends the following values for
the normal and extended burst parameters:
        normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
        extended burst = 2 * normal burst

Do not match with the examples on
"http://www.cisco.com/univercd/cc/td/doc/product/software/ios111/cc111/car.h
tm"

Meanwhile, other examples point to:
  Bc = Tc * CIR
  Be = Bc for a Single Rate, Dual Buck policer.

Example:
Router(config-if0# rate-limit input rate-limit access-group 101 20000000
24000 32000 conform-action set-mpls-exp-transmit 5 exceed-action
set-mpls-exp-transmit 0

Example:
Router(config-if)# rate-limit input 8000 1000 1000 access-group
conform-action set mpls-exp-transmit 5 exceed-action set-mpls-exp-transmit 5



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