[c-nsp] BFD on 7600

[Justin Shore]

MKS wrote:
> Can you share your experience with BFD on the 7600 platform and sw release?

I use it and like it.  However beginning with SRB2 Cisco removed support 
for running BFD on SVIs.  To date there is no workaround and the feature 
hasn't been added back to SR.  Otherwise it works fine in my experience.

> The document hints that BFD runs in hardware on the following
> modules,but does not explicitly say so. Can someone clarify this for
> me?

To the best of my knowledge BFD is 100% software driven.  Generating 
echo requests, processing those requests, receiving the echo replies and 
processing them aren't things that ASICs are suited for I don't believe. 
    I could be mistaken and someone else may chime in with more detailed 
knowledge, but I wouldn't expect something like BFD to be handled in 
hardware.

That's not necessarily a reason to not use BFD.  BFD is meant to be 
lightweight.  That may be a reason not to run several thousand instances 
of it on a single router of course...

Justin