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New Member

FRTS - Maximum Bc value on FR map-class

I would like to know what is the maximum value of Bc we can configure for a frame-relay map-class when using FRTS ?

I am currently using 12.2.1a.

Thanks for you support...

New Member

Re: FRTS - Maximum Bc value on FR map-class


the highest value is depending on the highest access line speed. The bc (commited

burst size) is the amount of data the router tries to send out during the measure

interval. You normaly should divied the CIR by 8. This is a good value for bc.

Note: On cisco router the CIR should be equal to the PIR in the network and the

mincir value should be equal to the CIR value in the network. If you set the router

cir value to the CIR value of the network the customer is no longer able to burst.

regards Ulrich Marzoli

New Member

Re: FRTS - Maximum Bc value on FR map-class

Hello Ulrich,

Thanks for your answer.

My concerns is about CIR >= 1024 K.

On my config, I have CIR >= 1024, and dividing by 8 is not working . I always get Tc set to max 64 ms.

With 64 ms, I can see TS is activated even below CIR, so I have a lot of packets delayed. To avoid this, I need to have higher value for Bc than 64 ms.

Do you know if any Cisco recommendations for Bc when CIR values are higher than 1024 K ?

Thanks again...Houdaifa


Re: FRTS - Maximum Bc value on FR map-class

Hi Houdaifa,

When using FRTS, the default Tc value depends on the frame-relay cir configured on the map class:

If CIR <= 640000 bps, then 10ms < Tc < 125ms

If CIR <= 1280000 bps, then 10ms < Tc < 63ms

If CIR <= 2048000 bps, then 10ms < Tc < 32 ms

For DATA PVCs, it is recommended that you do not configure the Bc, just let the router internally calculate Bc based on CIR / Tc. If this is causing the shaping to be active constantly, then need to look at what the internal Bc is for the router (byte limit value) and make sure you are not exceeding this every Tc!!

New Member

Re: FRTS - Maximum Bc value on FR map-class

Is there any gain for any traffic shapping, to have CIR = Port Bandwidth? Is there any difference for buffer allocation or queues management if CIR = Port Bandwidth?

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