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

From: "Anil Kumar S N (VRP Network BL)" <[email-masked]>
Date: Sat, 28 Mar 2015 13:10:18 +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

---

From: Chris Bowers <[email-masked]>
Date: Wed, 1 Apr 2015 01:10:29 +0000

Anil,

Thanks for your input and proposed text.  I added the text below (which is a slightly modified version of your proposed text) to the most recent version which is being maintained at:
https://github.com/cbowers/draft-ietf-rtgwg-mrt-frr-architecture

Tell me if you are OK with the final sentence that I added as well, or you can propose some other wording.

Thanks,
Chris

   TI-LFA:    Topology Independent Loop-free Alternate Fast Re-route
      (TI-LFA) [I-D.francois-spring-segment-routing-ti-lfa] aims to
      provide link and node protection of node and adjacency segments
      within the Segment Routing (SR) framework.  It has improved
      coverage over LFA 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 for the MPLS data plane due to the requirement for the PLR to
      impose an MPLS label stack on link failure.  On certain topologies
      the label stack size can grow significantly based on repair path.
      Note that TI-LFA requires shortest path forwarding based on SR
      Node-SIDs, as opposed to LDP labels, in order to construct label
      stacks for backups paths without relying on a large number of
      targeted LDP sessions to learn remote FEC-label bindings.

From: Anil Kumar S N (VRP Network BL) [mailto:[email-masked]]
Sent: Saturday, March 28, 2015 8:10 AM
To: Alia Atlas; Robert Kebler; Chris Bowers; [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked]
Subject: draft-ietf-rtgwg-mrt-frr-architecture-05.txt

Hi Authors,

1.  Introduction :

                                  Table 1

Thanks & Regards
Anil S N

---

From: "Anil Kumar S N (VRP Network BL)" <[email-masked]>
Date: Wed, 1 Apr 2015 05:29:17 +0000

Hi Chris,

                Its fine Chris, I am ok with the text.

Thanks & Regards
Anil S N

From: Chris Bowers [mailto:[email-masked]]
Sent: 01 April 2015 06:40
To: Anil Kumar S N (VRP Network BL); Alia Atlas; Robert Kebler; [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked]
Subject: RE: draft-ietf-rtgwg-mrt-frr-architecture-05.txt

Anil,

Thanks,
Chris

From: Anil Kumar S N (VRP Network BL) [mailto:[email-masked]]
Sent: Saturday, March 28, 2015 8:10 AM
To: Alia Atlas; Robert Kebler; Chris Bowers; [email-masked]<mailto:[email-masked]>; [email-masked]<mailto:[email-masked]>; [email-masked]<mailto:[email-masked]>; [email-masked]<mailto:[email-masked]>; [email-masked]<mailto:[email-masked]>
Subject: draft-ietf-rtgwg-mrt-frr-architecture-05.txt

Hi Authors,

1.  Introduction :

                                  Table 1

Thanks & Regards
Anil S N