The MPLS WG Archive

[Bala Rajagopalan <BRaja@tellium.com>]

> 
> Think of an unnumbered ERO of the form <1,1,1,1,1,1,1,1>
> 
> Now somewhere in the middle, an LSR wants to calculate a fast reroute 
> LSP. Normally, one would ask the TE database the simple question of 
> avoid my next hop and would give the router ID of the next hop, but 
> in this case, first you have to find out who the router at the end of 
> the egress interface is. This is not hard, then you need to find out 
> who the router that is right after the immediate hop. This second one 
> is harder since you have to make a query into the TE database, to 
> find that. Then you have to make a third query into TED, to calculate 
> an LSP that avoids the immediate next hop but merges as soon as 
> possible with the main LSP. And finally, you calculate an ERO that 
> now is a mixture of both numbered and unnumbered interfaces possibly 
> and initiate signaling. As I describe here, this is not undoable, but 
> at what cost.
> 
> If one adds the extra four bytes of router ID as part of the ERO (as 
> we did in the EERO) this whole thing becomes trivial to implement.
> 

Just curious, to implement this type of fast reroute, can't intermediate
nodes
get downstream information from record route?

Bala