The MPLS WG Archive

[Bora Akyol <akyol@pluris.com>]

At 5:41 PM -0500 2/27/01, Bala Rajagopalan wrote:
>  >
>>  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

Bala

As I wrote in my previous email, there are other ways of getting this 
info. The point that I was trying to make is that when you add the 
router ID, things become clearer and simpler.

Bora