RE: Inter-domain FRR Facility backup - discussion

["Vijayanand C - CTD, Chennai." <vijayc@hcl.in>]

Can the ASBR help out here:
 - Can it advertise a route with itself as the next hop for the PLR into the
MPs domain whenever it sees a bypass tunnels path msg going through it ?

First of all, how is the bypass itself signalled without any issues ? The
PLR wont know the topology of the other domain to route the path msg to the
MP in a node disjoint way.

Regards,
Vijay

> -----Original Message-----
> From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org]On
> Behalf Of Arthi Ayyangar
> Sent: Tuesday, February 28, 2006 1:25 PM
> To: ccamp@ops.ietf.org
> Subject: Inter-domain FRR Facility backup - discussion
> 
> 
> Hi,
> 
> Currently the merging of Backup Paths using the Sender 
> Template-specific 
> method relies on a different src address, but same LSP ID in the 
> SENDER_TEMPLATE for the backup LSP compared to that of the 
> protected LSP. 
> (6.1.1 of rfc 4090). After a failure, during local repair, 
> backup LSP Path 
> msgs are "tunneled" over the bypass directly to the MP and 
> the Resv from 
> MP is IP routed back to the address set in the RSVP_HOP 
> (6.4.3) of the 
> backup LSP.
> 
> As per the spec, the src address used for backup LSP has to be some 
> address on the PLR. I am not sure what the usual practice is, 
> but from 
> what I understand, it would be okay currently, to put any 
> local interface 
> address on the PLR in the RSVP_HOP as per the spec.
> 
> However, when the bypass LSP traverses different domains, and 
> the PLR and 
> MP are internal nodes in different domains, the MP is 
> unlikely to have a 
> route back to the interface address set in the RSVP_HOP for 
> the backup 
> LSP. So it will be unable to route back the Resv to the PLR. 
> This will 
> prevent the backup LSP from coming up.
> 
> So the issue is finding a way to route back the Resv from MP to PLR.
> 
> We could say that in case of inter-domain LSPs, the address 
> that the PLR 
> chooses should be the router-id of the PLR. But this has the 
> following 
> issues:-
> i) If we wan't specific behavior recommendation for inter-domain LSPs,
>     then we need to specify conditions to define an LSP as an 
> inter-domain
>     LSP at an LSR.
> ii) Using router id could increase the chances of this sender template
>     (src addr + lsp id) being confused with that of some 
> other LSP being
>     originated from this router and terminating on the MP.
> ii) For inter-AS LSPs, it may not be common for nodes inside one AS to
>      have routes to router-ids (or loopbacks) of "internal nodes" in
>      another AS.
> 
> Do you see this as an issue worthy of discussion ?
> Any ideas / suggestions / recommendations ?
> 
> thanks,
> -arthi
> 
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