[c-nsp] Flow Control and 10GE interfaces

[Kevin Graham]

> This is exactly the *only* situation, where classic flow control makes sense and

> does really help, since it properly triggers output queueing at the sending side
> when the real data-path speed is reached.

OK, the vitriol towards .3x in this thread was so strong I was concerned I had
somehow misunderstood it.

> Any other usage is likely to cause more problems than benefits.

Documentation that I could find is vague at best, but are any switches actually
doing end-to-end .3x and signaling ingress ports on a congested egress queue?
(inferring that this is the 'problems' everyone is citing?)

At least for simple flowcontrol, propagating across the bus/fabric seems wholly
broken and unnecessarily complex. However, sending a pause on a congested port
complex (ie. on PINNACLE's interface's to the bus or MEDUSA/HYPERION) towards
the port strikes me as both desirable and the most-likely form of implementation.