As a side note on the 7500 A3 ATM cards miscalculating the 1000 vs 1024
causes serious traffic loss. On 7200's you dont notice as much.
I got into a big arguement with my ATM group over what a megabit really
was over this and they like 1000 .
Regards,
Kevin
> > Not sure if its been changed in 12.0, but in 11.2, IOS output
> > traffic shaping against ATM interfaces is configured with respect
> > to 48 Byte Cell Payload.
> >
> > Therefore, with your PCR configured for 1536 kbps (kiloBITSpersecond):
> >
> > 1536 * 1000 = 1536000 bits per second
> > 1536000 / 8 = 192000 bytes per second
> > 192000 / 48 = 4000 cells per second
>
>I'm afraid this is incorrect. The Cisco kbps value is converted to cells
>using 53 bytes per cell, not 48. You can verify this for yourself by doing
>
>debug atm events
>
>and configuring a PVC. For instance:
>
>interface ATM2/0.1 point-to-point
> pvc 0/110
> vbr-nrt 2304 1536 100
>
>and you get as debug output the cell rates:
>
>VBR: pcr 5433, scr 3622, mbs 100
>
>1536 kbps gives you a cell rate of 3622 cps, not 4000.
>
>It's this way in 11.1CC, 12.0S and 12.1 - I don't believe 11.2 is any
>different.
>
>Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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