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Cell Relay Retreat>List Archive>month:1998-Apr> msg00237



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Re: Low bit rate chip set?

  • From: pmandal@ix.netcom.com
  • Date: Fri, 24 Apr 1998 13:15:08 -0600

Richard and Paul,

If you're looking for UBR @ 256 Kbps, the BT8233 doesn't
do that.

Let me see if I understand this correctly ---
are you essentially looking to specify UBR with PCR
capabilities.

If so, one way of achieving this is specifying
VBR-RT with PCR set @ 256 and CDVT set to something
very large

(BTW, I think there is a new proposed QOS called UBR+
that allows you to specify UBR traffic with PCR, or
was it MCR?)

The BT8233 can handle the following QoS types:
* UBR
* VBR-RT
* VBR-NRT
* ABR
* CBR
* CBR Pipes (not an official Qos)

As far as the BT8222 goes, the nice thing about
this little piece of silicon is that it does a "lot".

The bad thing is that some of the modes are extremely
difficult to program.

Praveen Mandal
RedBack Networks
praveen@rback.com

In article <353F5462.6B04@xedia.com>,
  Paul Koning <pkoning@xedia.com> wrote:
>
> Richard S. Tsumaki wrote:
> >
> > Anyone know of a chip vendor that offers a SAR/ATM layer chip(s) that
> > can output UBR to a PHY at very low rate (256 Kbps)?  Along with that
> > requirement do they:
> >
> > - Have an eval. NIC, with the SAR/ATM layer chip implemented?
> > - Able step that output rate up if necessary?
> > - Have the SAR/ATM layer chip separate from the PHY layer?  I.e., not a
> > single chip SAR+ATM+PHY design.?
> > - SARs AAL5?
> > - Handles other QOS traffic too?
>
> Rockwell has a solution you might examine: the Bt8233 SAR.  It comes
> with a companion PHY (the Bt8222) which has some unusual capabilities,
> but it can use other PHYs as well.  I've had it running at rates that
> low
> (and lower)
>
> 	paul
>
> --
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