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Cell Relay Retreat>List Archive>month:1998-Apr> msg00285



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Re: UBR over ATM

  • From: brasuell_bill@tandem.com
  • Date: Tue, 28 Apr 1998 17:35:39 GMT

ronald h. davis wrote:
> 
> Richard S. Tsumaki wrote:
> >
> > · UBR specifies a PCR and CDVT, but in almost all implementations that's
> > just set to the constraints of the physical interface for any VCC.
> >
> 
> i'll go along with setting a pcr: it's an optional field but an actual
> implementation would want to use a value for it.  setting cdvt, however,
> doesn't make sense: the only reason for setting a cdvt limit is for
> carrying traffic with real time constraints, like cbr and rt-vbr.
> 
<snip>
> _/ (_(_) / (_(_/_/_(_/  .       ronald.h.davis@lucent.com

No, CDVT is to police PCR. It specifies how much clumping of cells is
permitted. If CDVT is not set PCR can be anything up to port speed.

Bill