Difference bet. Rate-Limit & Traffic-Shape Commands

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Nov 30th, 2007
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Can anybody explain me the exact difference between the below mentioned commands and which when should be used where in configuration.


1) rate-limit input 64000 8000 8000 conform-action transmit exceed-action drop


2)traffic-shape rate 64000 8000 8000 1000

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Edison Ortiz Fri, 11/30/2007 - 05:59
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Both policing and shaping mechanisms use the traffic descriptor for a packet-indicated by the classification of the packet-to ensure adherence and service.


Policers and shapers usually identify traffic descriptor violations in an identical manner. They usually differ, however, in the way they respond to violations, for example:


•A policer typically drops traffic. (For example, the CAR rate-limiting policer will either drop the packet or rewrite its IP precedence, resetting the type of service bits in the packet header.)


•A shaper typically delays excess traffic using a buffer, or queuing mechanism, to hold packets and shape the flow when the data rate of the source is higher than expected. (For example, GTS and Class-Based Traffic Shaping use a weighted fair queue to delay packets in order to shape the flow, and FRTS uses either a priority queue, a custom queue, or a FIFO queue for the same, depending on how you configure it.)


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http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/part20/qchpolsh.htm



bvsnarayana03 Sat, 12/01/2007 - 21:22
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In addition Edison's explanation, lets take a instance:


Suppose a FR network where the customer has contracted a CIR with ISP let it be 64Kbps. The physical link may be 1Mbps pipe. Thus customer may pump traffic at a much higher rate than CIR. This may congest the ISP network, thus ISP apllies a policer to drop customer's traffic above CIR.


Now what a customer does is to avoid the dropping of traffic at ISP, he would slower down the traffic towards ISP so that it doesnt exceed the contacted rate.


Link provided by Edison is really nice, you may refer it.

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