[c-nsp] Reliable static routes and 12.2S

[sthaug at nethelp.no]

> > You're looking for BFD (bi-directional forwarding detection). As far as
> > I know not yet implemented by Cisco, and in JunOS only used for IGP
> > yet (IS-IS, not sure about OSPF). Provides end2end failure detection
> > down to milliseconds time-to-detect (I've seen 50ms - this is SONET/SDH
> > ring wrap time).
> 
> I'm not sure whether I want to imagine what happens to a SDSL line if
> you put enough BFD packets on it to get 50ms failover times...

If somebody is stupid enough to use BFD for that, they deserve what
they get.

On the other hand, BFD sure looks interesting for those cases where
you have router - switch - router on GigE, and the loss of link on one
side of the switch won't lead to a corresponding loss of link on the
other.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no