Re: [nsp] HSSI Card Limitations ?

From: mike holdsworth (mike.holdsworth@metrodata.co.uk)
Date: Tue Mar 13 2001 - 05:42:32 EST


Hi Jared,

The Cisco products are generally limited by the speed of the HDLC
controller. The speed limitations comes from hardware timing details and
from the DMA transfer speeds.

The HDLC logic in the Mueslix chip used in the original HSSI interfaces was
qualified at 52 Mbps. This speed was used as it is STS-1 or OC-1 at
51.84Mbps.

Cisco's formal answer is that they cannot go above 52Mbps, because HSSI was
not designed or tested above these speeds.

This is true for most Routers, though HSSI on a satellite modem and on our
equipment is maxing at 90Mbps.

I think the HSSI Line Rate of 16Mbps is simply one of the internal clocking
options. We have loads of customers all over the world who are plugging our
equipment into HSSI interfaces at 8.448Mbps, 34.368Mbps and 44.736Mbps.

Some clients were having problems with the lower spec Cisco Routers such as
the 3600 series. They said they don't perform that well at speeds such as
34.368Mbps. I'm not sure if this is true, and am happy to be proved
completely wrong.

Hope this helps.

Mike



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