RE: WG Adoption Call for draft-psarkar-rtgwg-rlfa-node-protection

[<[e-mail]>]

Hi authors,

This is an interesting work, thanks for the draft and the rtgwg presentation.


1)      Regarding node protection, have you considered/evaluated the use of the algorithm proposed in TI-LFA (draft-francois-segment-routing-ti-lfa)?
Namely: computing the backup path with a (C)SPF (without the protected node), and enforcing this explicit path using multiple segments/labels?
Clearly, using TI-LFA in the absence of Segment Routing (more precisely the absence of adjacency segments/labels), 100% coverage is not possible. But this is also not possible with draft-psarkar. It's a priori not clear to me if the coverage would be increased or decreased. On the pro side, the use of multiple segments increases the coverage by allowing reaching more Q nodes. On the con side, the additional constraints added during the computation (namely enforcing the post convergence path (only)) decreases the coverage as this specific path may require an adjacency segment to cross a high metric link.
Evaluating this option would probably be interesting (in term of coverage, control plane computation, label stack depth, routing optimality, number of T-LDP sessions).


2)      On a related note, a possible heuristic for draft-psarkar to pick a node protecting PQ, would be to pick the PQ on the post convergence SPF (as per above/TI-LFA). That's simple, computationally not expensive (one SPF), and reduce the set of Candidate Node-Protecting PQ to a single element at most (not considering ECMP, to simply). If the set has one node, a node protecting PQ node has been found (on the optimal path, as a free property). If the set is empty, you may choose to fall back on draft-psarkar (picking a subset of PQ using heuristic and running SPF on those PQ).

Thanks,
Regards,
Bruno

From: rtgwg [mailto:[e-mail]] On Behalf Of Alvaro Retana (aretana)
Sent: Friday, March 14, 2014 6:02 AM
To: [e-mail]
Cc: [e-mail]
Subject: WG Adoption Call for draft-psarkar-rtgwg-rlfa-node-protection

Hi!

During the meeting in London the authors asked for the WG to adopt this draft.

This message officially starts the call for adoption for draft-psarkar-rtgwg-rlfa-node-protection.  Please indicate your position about adopting it by end-of-day on March 28, 2014.

http://tools.ietf.org/html/draft-psarkar-rtgwg-rlfa-node-protection

Thanks!

Alvaro.

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