Ahmed, and all,

  1.  From my POV the changes made in the -18 revision of the draft resolve 
inconsistency between the Abstract and the body of the draft.
  2.  I have a question about usage of protected and unprotected Adj-SIDs in 
TI-LFA:
     *   In Section 
10<https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-segment-routing-ti-lfa#section-10>
 “Usage of Adjacency segments in the repair list”, the draft says that “To 
avoid the possibility of this double FRR activation, an implementation of 
TI-LFA MAY pick only nonprotected adjacency segments when building the repair 
list”
     *   At the same time, in Section 9 “TI-LFA and SR algorithms” in the part 
that discusses using TI-LFA with FlexAlgo, the draft says “If an implementation 
uses the constrained SPF algorithm bound to the FlexAlgo, then the 
implementation MUST only use Node-SIDs bound to the FlexAlgo and/or Adj-SIDs 
that are unprotected”.
Can you please explain why usage of unprotected Adj-SID in TI-LFA repair paths 
in the case of the default SPF is OPTIONAL, while in the case of constrained 
SPFs it is MANDATORY?

Regards, and lots of thanks in advance,
Sasha

From: Ahmed Bashandy <abashandy.i...@gmail.com>
Sent: Wednesday, November 13, 2024 10:01 PM
To: Bruno Decraene <bruno.decra...@orange.com>; Clarence Filsfils 
<cfils...@cisco.com>; Dan Voyer <daniel.vo...@bell.ca>; Pierre Francois 
<pierre.franc...@insa-lyon.fr>; Stephane Litkowski <slitk...@cisco.com>; RTGWG 
<rtgwg@ietf.org>; rtgwg-chairs <rtgwg-cha...@ietf.org>; James Guichard 
<james.n.guich...@futurewei.com>
Cc: John Scudder <j...@juniper.net>; superu...@gmail.com
Subject: [EXTERNAL] [rtgwg] Re: New Version Notification for 
draft-ietf-rtgwg-segment-routing-ti-lfa-18.txt

Hi

I uploaded version 18 of the ti-lfa draft to address the two DISCUSS
items in
https://datatracker.ietf.org/doc/draft-ietf-rtgwg-segment-routing-ti-lfa/ballot/<https://datatracker.ietf.org/doc/draft-ietf-rtgwg-segment-routing-ti-lfa/ballot>

- To address John Scudder's Discuss, I made the modifications to remove
the word "key" from the abstract as suggested by Sasha at
https://mailarchive.ietf.org/arch/msg/rtgwg/nWR4uYaT3T30XRiyRdAoIqO22AM/<https://mailarchive.ietf.org/arch/msg/rtgwg/nWR4uYaT3T30XRiyRdAoIqO22AM>
and Pierre at
https://mailarchive.ietf.org/arch/msg/rtgwg/zHP2qvP2Ew1oWl5G7Gq8niu8vy8/<https://mailarchive.ietf.org/arch/msg/rtgwg/zHP2qvP2Ew1oWl5G7Gq8niu8vy8>

- To address Murray Discuss (as well as as comments from others) I
removed the word "SHOULD" from sections 6.2, 6.3, and 9 as I suggested
during my presentation during the rtgwg meeting last Tuesday Nov/5/24.
The entire recording of the RTGWG meeting can be found in
https://meetecho-player.ietf.org/playout/?session=IETF121-RTGWG-20241105-0930<https://meetecho-player.ietf.org/playout/?session=IETF121-RTGWG-20241105-0930>

The slides that I presented in in PDF format can be found in
https://datatracker.ietf.org/meeting/121/materials/slides-121-rtgwg-02-tilfa-bgppic-00.pdf<https://datatracker.ietf.org/meeting/121/materials/slides-121-rtgwg-02-tilfa-bgppic-00.pdf>


Please take a look and see if the modifications are  good to address the
two DISCUSS Items


Thanks

Ahmed


On 11/13/24 11:16 AM, internet-dra...@ietf.org<mailto:internet-dra...@ietf.org> 
wrote:
> A new version of Internet-Draft draft-ietf-rtgwg-segment-routing-ti-lfa-18.txt
> has been successfully submitted by Ahmed Bashandy and posted to the
> IETF repository.
>
> Name: draft-ietf-rtgwg-segment-routing-ti-lfa
> Revision: 18
> Title: Topology Independent Fast Reroute using Segment Routing
> Date: 2024-11-13
> Group: rtgwg
> Pages: 27
> URL: 
> https://www.ietf.org/archive/id/draft-ietf-rtgwg-segment-routing-ti-lfa-18.txt<https://www.ietf.org/archive/id/draft-ietf-rtgwg-segment-routing-ti-lfa-18.txt>
> Status: 
> https://datatracker.ietf.org/doc/draft-ietf-rtgwg-segment-routing-ti-lfa/<https://datatracker.ietf.org/doc/draft-ietf-rtgwg-segment-routing-ti-lfa>
> HTMLized: 
> https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-segment-routing-ti-lfa<https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-segment-routing-ti-lfa>
> Diff: 
> https://author-tools.ietf.org/iddiff?url2=draft-ietf-rtgwg-segment-routing-ti-lfa-18<https://author-tools.ietf.org/iddiff?url2=draft-ietf-rtgwg-segment-routing-ti-lfa-18>
>
> Abstract:
>
> This document presents Topology Independent Loop-free Alternate Fast
> Reroute (TI-LFA), aimed at providing protection of node and adjacency
> segments within the Segment Routing (SR) framework. This Fast
> Reroute (FRR) behavior builds on proven IP Fast Reroute concepts
> being LFAs, remote LFAs (RLFA), and remote LFAs with directed
> forwarding (DLFA). It extends these concepts to provide guaranteed
> coverage in any two-connected networks using a link-state IGP.
> Although not a TI-LFA requirement or constraint, TI-LFA also brings
> the benefit of the ability to provide a backup path that follows the
> expected post-convergence path, reducing the operational need to
> control the tie-breaks among various FRR options.
>
>
>
> The IETF Secretariat
>
>

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