traffic-shape Question

Unanswered Question
Feb 1st, 2007

if i have to following configuration on a interface:

bandwidth 2048

no ip address

traffic-shape rate 512000 12800 12800 1000

Does it mean traffic will not go higher than 512000?

I have this problem too.
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drolemc Thu, 02/08/2007 - 11:12

This statement only shapes the traffice. It does not police. So the traffice can exceed 512000 by the burst size mentioned (12800) in the command.

dgahm Thu, 02/08/2007 - 11:33

Your traffic shaping will send sustained bits per interval of 12800, and excess bits per interval of 12800. Each default interval is 25ms, so 12800 times 40 (intervals per sec) gives you a sustained rate of 512000 plus burst of 512000 for a total of 1024000 per sec.

If you want this to run at 512000 with no burst use this:

traffic-shape rate 512000 12800 0

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ggovier Mon, 06/11/2007 - 19:41

Good, that's the way I was interpreting the docs. It seemed to me the Excess Burst would be available unless there was a congestion event. That can be signalled on Frame Relay VCs using BECN, but I was using 100BaseT Ethernet and it doesn't signal congestion, so I changed to Excess Burst = 0.

I have not been able to measure the results (live network), so I'm glad to see I'm on the right track.

But I do have a couple additional questions.

by default, the 2801 seems to select 25msec as the interval to use. Can you go to a shorter interval? What is the minimum?

and the last field is buffer, but expressed in bps (range 0 - 4096). What does that mean?

If traffic exceeds the shaped rate too long, eventually packets will be discarded when the buffer is full. How do I know how much buffering there is? and where would I look for a count of the dropped packets?

Thanks - Glen


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