Re: Request for RTGWG Working Group adoption for draft-bashandy-rtgwg-segment-routing-ti-lfa
Ahmed Bashandy <abashandy.ietf@gmail.com> Fri, 13 July 2018 19:29 UTC
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Subject: Re: Request for RTGWG Working Group adoption for draft-bashandy-rtgwg-segment-routing-ti-lfa
To: Stewart Bryant <stewart.bryant@gmail.com>, Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
Cc: "rtgwg-chairs@ietf.org" <rtgwg-chairs@ietf.org>, "pfrpfr@gmail.com" <pfrpfr@gmail.com>, "draft-bashandy-rtgwg-segment-routing-ti-lfa@ietf.org" <draft-bashandy-rtgwg-segment-routing-ti-lfa@ietf.org>, "daniel.voyer@bell.ca" <daniel.voyer@bell.ca>, "rtgwg@ietf.org" <rtgwg@ietf.org>, Robert Raszuk <robert@raszuk.net>, Chris Bowers <cbowers@juniper.net>
References: <1e42030f-3d68-fca3-500c-95ab7303e7cd@gmail.com> <F0098308-4F1E-4596-B3F9-B6740BA88F9A@gmail.com> <bfbe9775-ee81-b1fe-bb1f-a02392bc6fb5@gmail.com> <43389eec-6d63-ee35-54ed-19562b24562b@gmail.com> <12E9EB99-2970-49B6-9407-FE6AEAB3A0BB@gmail.com> <SN6PR05MB44305802FF3330DC2AE27F9CA96E0@SN6PR05MB4430.namprd05.prod.outlook.com> <CA+b+ERm=Jczivo0sJGuHWyP7UJbJFY=+N-vyQK7H_Es2anLGmQ@mail.gmail.com> <DB5PR0301MB1909BF5C925473CB3BC97BE79D6D0@DB5PR0301MB1909.eurprd03.prod.outlook.com> <27db8d16-6120-17e9-55fa-30d35be97b32@gmail.com> <DB5PR0301MB190910B15E3B74ED45B18CE19D5B0@DB5PR0301MB1909.eurprd03.prod.outlook.com> <2ff33bf0-cb23-9be2-99ac-25209876a5cf@gmail.com>
From: Ahmed Bashandy <abashandy.ietf@gmail.com>
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Date: Fri, 13 Jul 2018 12:29:33 -0700
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See inline #Ahmed Ahmed On 7/10/18 5:48 AM, Stewart Bryant wrote: > > > > On 10/07/2018 12:42, Alexander Vainshtein wrote: >> >> Ahmad and all, >> >> Lots of thanks for your response to my comments. >> >> Unfortunately I cannot say that it addresses all of them – please see >> */inline below/*for the details. >> >> Regards, >> >> Sasha >> >> Office: +972-39266302 >> >> Cell: +972-549266302 >> >> Email: Alexander.Vainshtein@ecitele.com >> >> *From:*Ahmed Bashandy [mailto:abashandy.ietf@gmail.com] >> *Sent:* Monday, July 9, 2018 10:54 PM >> *To:* Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>; Robert >> Raszuk <robert@raszuk.net>; Chris Bowers <cbowers@juniper.net> >> *Cc:* rtgwg-chairs@ietf.org; pfrpfr@gmail.com; >> draft-bashandy-rtgwg-segment-routing-ti-lfa@ietf.org; >> daniel.voyer@bell.ca; rtgwg@ietf.org; Stewart Bryant >> <stewart.bryant@gmail.com> >> *Subject:* Re: Request for RTGWG Working Group adoption for >> draft-bashandy-rtgwg-segment-routing-ti-lfa >> >> Thanks for the comments >> See the reply inline at #Ahmed >> >> Ahmed >> >> On 5/29/18 3:35 AM, Alexander Vainshtein wrote: >> >> Robert, Chris and all, >> >> I agree with Robert that it is up to the authors of an individual >> submission what they consider in or out of scope of the draft. >> >> However, I agree with Chris that the authors of an individual >> draft asking for its adoption by a specific WG should do their >> best to address the comments they have received from the WG members. >> >> #Ahmed: Thanks a lot >> >> From my POV this did not happen in the case of the draft in >> question – for the following reasons: >> >> 1.In his early RTG-DIR review >> <https://datatracker.ietf.org/doc/review-bashandy-rtgwg-segment-routing-ti-lfa-00-rtgdir-early-bryant-2017-05-31/> >> of the draft Stewart has pointed to the following issues with >> the -00 version of the draft (needless to say, I defer to Stewart >> regarding resolution of these issues): >> >> a.*No IPR disclosures for draft-bashandy*in spite of 3 IPR >> disclosures for its predecessor draft-francois. I have not seen >> any attempts to address this issue – at least, search of IPR >> disclosures for draft-bashandy did not yield any results today >> >> #Ahmed: Since draft-bashandy inherits draft-francois, then the IPR of >> the latter applies to the former. But if there is a spec that >> requires re-attaching the IPR of an inherited draft to the inheriting >> draft, it would be great to point it out or point out some other >> draft where that occurred so that I can follow the exact procedure. >> >> */[[Sasha]] Well, it looks like we have been both in error here: >> there is a Cisco IPR Disclosure >> <https://datatracker.ietf.org/ipr/3068/> for draft-bashandy dated >> 18-Sep17./**//**/This disclosure has been posted after Stewart’s >> early review, and I have been wrong not checking for it before >> sending this comment. But there is no “inheritance” from IPR >> Disclosures for draft-francois either. So I think this issue is now >> closed./**//* >> >> >> >> b.*Selecting the post-convergence path *(inheritance from >> draft-francois) does not provide for any benefits for traffic >> that will not pass via the PLR */after convergence/*. >> >> i.The authors claim to have addressed this issue by stating that >> “Protection applies to traffic which traverses the Point of Local >> Repair (PLR). Traffic which does NOT traverse the PLR remains >> unaffected.” >> >> ii.From my POV this is at best a misleading statement because it >> does not really address Stewart’s comment which was about traffic >> that */traversed the PLR before convergence/* but */would not >> traverse it after convergence/*. >> >> iii.This is not a fine distinction: actually it indicates that >> selecting post-convergence path for repair is more or less >> useless (unless the traffic originates at the PLR). >> >> #Ahmed: Thanks for pointing out this *additional benefit* of >> providing a post-convergence back path. If a flow starts to use the >> PLR after a failure, then the presence of a post convergence backup >> path on the PLR extends the benefits of using the post-convergence >> path to flows that did not use the PLR prior the topology change. I >> will modify the statement in the introduction to indicate that :) >> >> */[[Sasha]] Sorry, but this looks quite off the target to me. The >> repair path provided by TI-LFA is only relevant for the period >> between the actual failure (that triggers usage of this path) and >> re-convergence of IGP. I.e. traffic that did cross the PLR before >> failure but crosses it after failure AND IGP re-convergence cannot >> benefit in any way from selection of the repair path. At the same >> time, it is pretty easy to give an example of a setup in which:/* >> >> -*/Traffic between two nodes crosses the PLR before failure/* >> >> -*/The destination of this traffic is protected (say by a local LFA) >> and so will use the repair path in the interval between failure >> detection and IGP re-convergence/* >> >> -*/After IGP re-convergence traffic does not pass thru the original >> PLR anymore and thus does not experience any benefits from any >> possible selection of the repair path by the PLR./* >> >> */If you wish, I can send you a simple example topology. /* >> >> *//* >> >> */So, from my POV, this issue remains as open as before./* >> >> >> > SB> This concern has been a day one issue by pretty much everyone that > has seen this work. > > The draft really needs text to address it. #Ahmed: I replied to Sasha > >> >> c.*Selecting the post-convergence path is detrimental to >> scalability of the solution*. Please note that in RFC 7490 >> <https://tools.ietf.org/html/rfc7490> “the Q-space of E with >> respect to link S-E is used as a proxy for the Q-space of each >> destination” in order to provide a scalable solution – but this >> clearly is not the case of draft-bashandy if post-convergence >> paths are used. To the best of my understanding, the authors did >> not, so far, do anything to address this comment. >> >> #Ahmed: I fail to see why there is a scalability problem. >> draft-bashandy-rtgwg-segment-routing-ti-lfa just prefers particular >> node(s) in the Q space if that node(s) is (are) along the post >> convergence path. >> But if I am missing something, it would be great to point out exactly >> what aspect of scalability you are concerned about so that we can >> address it >> >> */[[Sasha]] Please take a look at the text from Section 5.2.1 of RFC >> 7490 <https://tools.ietf.org/html/rfc7490> (the relevant text is >> highlighted):/* >> >> Note that the Q-space calculation could be conducted for each >> >> individual destination and a per-destination repair tunnel end point >> >> determined. However, this would, in the worst case, require an SPF >> >> computation per destination that is not currently considered to be >> >> scalable. Therefore, the Q-space of E with respect to link S-E is >> >> used as a proxy for the Q-space of each destination. >> > > >> >> */[[Sasha]] The proxy approach described above works well enough with >> RLFA. But it is hardly compatible with the proposal to use prefer the >> repair paths that match post-convergence paths, because >> post-convergence paths are per affected destination. I do not see how >> this can be combined with selecting a single Q-space (and hence a >> single PQ node) for all destinations./* >> > > SB> That is a good point. > > - Stewart
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- Re: Request for RTGWG Working Group adoption for … Ahmed Bashandy
- Re: Request for RTGWG Working Group adoption for … Ahmed Bashandy
- Re: Request for RTGWG Working Group adoption for … Jeff Tantsura
- RE: Request for RTGWG Working Group adoption for … Chris Bowers
- Re: Request for RTGWG Working Group adoption for … Robert Raszuk
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … bruno.decraene
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … bruno.decraene
- RE: Request for RTGWG Working Group adoption for … bruno.decraene
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … bruno.decraene
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- Re: Request for RTGWG Working Group adoption for … Ahmed Bashandy
- Re: Request for RTGWG Working Group adoption for … Ahmed Bashandy
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- Re: Request for RTGWG Working Group adoption for … Alexander Vainshtein
- RE: Request for RTGWG Working Group adoption for … stephane.litkowski
- Re: Request for RTGWG Working Group adoption for … Stewart Bryant
- Re: Request for RTGWG Working Group adoption for … Ahmed Bashandy