The MPLS WG Archive

[Nic Neate <Nic.Neate@dataconnection.com>]

> -----Original Message-----
> From: David Charlap [mailto:David.Charlap@marconi.com]
> Sent: Friday, May 07, 2004 3:10 PM
> To: IETF MPLS List
> Subject: Re: FW: Fast Reroute question
> 
> 
> What I'm still not clear on, however, is how a merge point 
> can identify 
> which protected LSP (arriving on a normal interface) 
> corresponds to what 
> protected LSP (arriving through a bypass).
> 
> It would seem that all LSPs in the same session with the same 
> LSP ID are 
> assumed to be be backups of one another.  But it seems that 
> there can be 
> situations where this will match when the LSPs don't have a primary/ 
> backup relationship (for example, if extended tunnel ID of 
> zero is used 
> to signal a many-to-one multicast LSP - which is perfectly valid.)
> 

Right, I see your point.  This is an issue with the SenderTemplate specific
merge rules then.

Note from section 7.1.1 of the FRR draft that LSPs in the same session with
differing SenderTemplates are only merged if their LSP IDs, outgoing
interfaces, next hops, and downstream EROs are identical.  I've not come
across anyone doing many-to-one multicast in the way you describe so I'm not
sure what the applications are and whether this merging would be acceptable.
I'll leave it to someone with more experience in that area to comment.

Nic


> Or is this simply a category of LSP that is effectively deprecated in 
> the eyes of the working group?
> 
> > That's how I understand it anyway.  Hope that make sense 
> and I've not
> > missed anything critical.
> 
> -- David
>