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A question on Cisco traffic shape example in QOS student guide

This is an example copied from Cisco QOS course.I think the number Be here is wrong.

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An ISP wants to control the amount of traffic injected into the Frame Relay WAN by the customer. The SP service uses an E1 line as the access line, limits the customer to 256 Kbps on the average, but also permits bursts of up to thirty seconds at the E1 line rate.

The parameters are calculated based on the service requirements. CIR (the average bit rate) is set at the specified average rate, the burst size is set to one eighth of the CIR (32000 bits), and the excess burst size reflects the allowed thirtysecond

burst at full E1 line rate.

The excess burst size was calculated using the following formula:

1. Each second of transmission at line-speed requires 2 Mbits

2. Thirty second burst therefore requires 30 x 2 Mbits

3. The excess burst size is 30 x 2048000 = 61440000

configuration in the material is following:

in serial 0

traffice shape rate 256000 32000 61440000.

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I think this is wrong. Be(Excess busrt size) is defined as bits/interval. How come the Be is 61440000? Thanks

2 REPLIES
Silver

Re: A question on Cisco traffic shape example in QOS student gui

I agree with you, the Excess burst should be in bits and not bits/interval. The value 61440000 seems to be incorrect. Shouldnt it be 32000/30 bits ?

Community Member

Re: A question on Cisco traffic shape example in QOS student gui

http://www.cisco.com/en/US/tech/tk713/tk237/technologies_configuration_example09186a00800942f8.shtml

I think the concept in FRTS almost same as GTS. welcome joinging this discusstion to give me a clear answer.

Thanks

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