[nsp] C7200 Bandwidth Points

[Siva Valliappan]

the issue isn't very much what your average bus utilization is, but
the potential to oversubscribe the bus at peak utilization or spikes
in traffic (let's stay you get a packet ingress at the exact same nanosecond
on every one of your interfaces triggering a PCI bus request to move the
packet to packet memory).  you are creating the potential for the bus to be
not able to handle PCI requests and cause PCI timeouts in worst case
scenarios.  so TAC and development do not tend to support 7200s in
oversubscribed configuration because the behavior in this mode is
unknown and not predictable.

cheers
.siva

On Fri, 11 Jul 2003, Chris Parker wrote:

> At 02:30 PM 7/11/2003 -0400, Temkin, David wrote:
> >'nother question.  I understand how bandwidth points work on the 7200
> >series, however, if I'm building a system and I know that I won't be using
> >interfaces to their full potential (ie, there's an extra FE or DS-3
> >interface in it) and it exceeds the maximum amount of points per the NPE,
> >will the system run correctly or will it error?
>
> The router will complain, and I think TAC won't support it very well
> if that is the case, but it will not in my experience shut down any
> interfaces or refuse to run.
>
> It basically tells you that you're oversubscribing the bus, and can
> have problems, but as you note, if you aren't pushing near the full
> capacity, you probably won't overuse the bus.
>
> -Chris
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