[c-nsp] OIR on 7600s: Pretty much evil?

[Benjamin Lovell]

Yes the LC bus is isolated but in async mode the BFD packet must still be sent to the RP CPU and all BFD packets are generated from the RP CPU. 6500/7600 do not support distributed BFD like CRS and GSR where LC CPU handles BFD.

I assume that you were considering scenario where BFD in echo mode can still echo BFD back out where ingress LC is DFC, which it can. However, if you are not generating BFD out for far side to echo or cannot punt the echo to RP CPU on return BFD will still drop. 

There are a number of closed DDTS related to this and other protocols running tight timers dropping during OIR due to buss stall and not only on SUP32 or CFC scenario. 

-Ben


On Nov 11, 2010, at 12:52 PM, David Sinn wrote:

> I do have to question Ben's comments about a stall killing interrupts.  At least on the Sup720 the LC-bus is isolated from the backplane bus and so I can't see why the LC-bus would stall too (and experience shows that it's a non-event).  If we are talking about Sup32's or Sup2's without fabrics, the LC-bus is bridged to the backplane bus, so stalls will be visible.