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Re: UBR at MAE-East ATM, anyone?

  • From: Alex Rubenstein
  • Date: Tue Apr 18 13:20:58 2000

On Tue, 18 Apr 2000, Kevin Oberman wrote:

> Alex,
> your description of how the MAE ATM NAPs work is not quite in line
> with either my understanding or the ATMF traffic management specs.

I'm not surprised, as I may not know what I am talking about :)

> As you state, the connections to the NAPS is ABR, but you then say 
> "with PCR being twice SCR". If the connection is ABR (and it is), there
> is not PCR or SCR. There is only MCR (minimum cell rate). This really
> means that you are guaranteed that the bandwidth reserved by the
> MCR will be available to you. Any traffic beyond this is treated on a
> best-effort basis, exactly as if it was UBR. The only limit on what
> you may inject (above MCR) is the line rate and there is no guarantee
> that any of this traffic will make it through the fabric.

I thought it was strange also, however my information comes from Wcom:


> 3) is it still VBR, or UBR/ABR now?

It's actually implemented as ABR, with the peak cell
rate enforced and set to twice the reserved rate.