RE: BIRD / BGP-ORR experiences?

[Deepak Jain <deepak () ai net>]

> Do we even like BGP ORR?

I like it, I think ADD-PATH and ORR are mandatory features in modern RR infra. However proper interaction between them 
may not exist in every implementation. Basically you want

a) send all ECMPable paths
b) send one backup path

This will lead to superior to full-mesh by every reasonable metric:
- smaller rib (no routes that you don't need, but all the routes you care about)
- redundancy (one iBGP down, is not customer outage)
- less state changes, less code stress

ORR is not an RFC and there are some open questions. What to reflect, when next-hop is not in IGP? Do we hope that 
receiver would recurse to the same IGP next-hop? Juniper makes this assumption, which to me is decidedly the common 
case. Cisco makes no assumption and doesn't reflect if next-hop is not in IGP, but as I understand they will fix to the 
same assumption as Juniper.

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Thanks for your input. How do you handle next-hops? Tunnels between all eBGP speakers as if they were fully meshed as 
their potential next-hops? 

Deepak