Hi Shasha,
See inline.
Regards,
Dirk
1. 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?
At least in SR over MPLS, the Adj-SID does not belong to a specific FlexAlgo.
As such, protected Adj-SIDs may have a backup path that exits the
Flex Algo topology, in which case it violates the constrains of
the Flex Algo Definition (FAD)
Regards,
Dirk
________________________________
Van: Alexander Vainshtein <Alexander.Vainshtein=40rbbn....@dmarc.ietf.org>
Verzonden: donderdag 14 november 2024 12:45
Aan: Ahmed Bashandy <abashandy.i...@gmail.com>
CC: John Scudder <j...@juniper.net>; Clarence Filsfils <cfils...@cisco.com>;
Stephane Litkowski <slitk...@cisco.com>; Pierre Francois
<pierre.franc...@insa-lyon.fr>; RTGWG <rtgwg@ietf.org>; rtgwg-chairs
<rtgwg-cha...@ietf.org>
Onderwerp: [rtgwg] Re: [EXTERNAL] Re: New Version Notification for
draft-ietf-rtgwg-segment-routing-ti-lfa-18.txt
CAUTION: This is an external email. Please be very careful when clicking links
or opening attachments. See the URL nok.it/ext for additional information.
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
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
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
> 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
> Diff:
> 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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