[c-nsp] Resilience in order of few hundreds of milliseconds

Tony Li tli at cisco.com
Tue Mar 6 15:46:45 EST 2007

> Any comments?
> (it is not necessary reach 50 to 100ms as in FRR; 200 to 400ms  
> would be
> fine, but network stability under high traffic is very important,  
> so no
> false positives needed)

Well, here's the problem.  The requirements that you have don't  
really match what FRR was designed for, and thus the overhead is  
uncomfortable.  Similarly, IGP timers were never intended to match  
your requirements either.

> When there is FRR support, we can use RSVP hellos; I am wondering way
> Cisco does not support RSVP hellos being a mechanism to indicate  
> failure
> on logical tunnel interface from headend to tailend. The headend would
> detect failure on option 1 and try option 2. (or if there are two  
> tunnel
> interfaces with diverse path and Multipath Routing, when one logical
> interface goes Down traffic would be carried by other interface)

That's theoretically possible, but if you choke down local failure  
detection, then the propagation delay works against you.

> Moving to other idea, what do you think about this OSPF tuning?
> -Send OSPF hellos at each 100ms, setting TspfDelay and TspfHold to 0.

I'm really not a big fan of IGP timing solutions as faster timers  
just make the IGP less robust.  But that's just me...


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