Subject: draft-ietf-rtgwg-mrt-frr-architecture-05.txt

From: "Anil Kumar S N (VRP Network BL)" <[email-masked]>
Date: Sat, 28 Mar 2015 11:54:51 +0000

Hi Authors,

      In  "comparison of IP/LDP FRR Methods" section of the document , I feel we should add comparison with TI-LFA (draft-francois-spring-segment-routing-ti-lfa-01) where TI-LFA approach achieves guaranteed coverage  against link or node failure, in any IGP network, relying on the  flexibility of SR. This will give readers better picture and enables them with more information so that they can choose MRT if they feel it suites their requirement better; compared to IT-LFA.
Changes :

1.  Introduction :

   Other existing or proposed solutions are partial solutions or have
   significant issues, as described below.

                 Summary Comparison of IP/LDP FRR Methods

   +---------+-------------+-------------+-----------------------------+
   |  Method |   Coverage  |  Alternate  |    Computation (in SPFs)    |
   |         |             |   Looping?  |                             |
   +---------+-------------+-------------+-----------------------------+
   | MRT-FRR |     100%    |     None    |         less than 3         |
   |         |  Link/Node  |             |                             |
   |         |             |             |                             |
   |   LFA   |   Partial   |   Possible  |         per neighbor        |
   |         |  Link/Node  |             |                             |
   |         |             |             |                             |
   |  Remote |   Partial   |   Possible  |    per neighbor (link) or   |
   |   LFA   |  Link/Node  |             |  neighbor's neighbor (node) |
   |         |             |             |                             |
   | Not-Via |     100%    |     None    |      per link and node      |
   |         |  Link/Node  |             |                             |
   |         |             |             |                             |
   | TI-LFA  |     100%    |   Possible  |    per neighbor (link) or   |
   |         |  Link/Node  |             |  neighbor's neighbor (node) |
   |         |             |             |                             |
   +---------+-------------+-------------+-----------------------------+

                                  Table 1

   TI-LFA: Topology Independent Loop-free Alternate Fast
   Re-route (TI-LFA), aimed at providing link and node protection of
   node and adjacency segments within the Segment Routing (SR)
   framework [draft-francois-spring-segment-routing-ti-lfa-01].
   Has improved coverage over LFAs and Remote LFA for link and node
   protection and also guarantees complete coverage. The trade-off
   of looping traffic to improve coverage is still made.
  The computation required is quite high with added complexity.
   TI-LFA is supported only MPLS data plane with a requirement to
   carry additional MPLS label stack on the link failure; on certain
   topologies stack size can grow significantly based repair path.

Thanks & Regards
Anil S N

"Be liberal in what you accept, and conservative in what you send" - Jon Postel