[Isis-wg] 答复: 答复: 答复: WG Last Call for draft-ietf-isis-segment-routing-msd-07

Xuxiaohu <xuxiaohu@huawei.com> Sat, 23 December 2017 04:33 UTC

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From: Xuxiaohu <xuxiaohu@huawei.com>
To: Jeff Tantsura <jefftant.ietf@gmail.com>, "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>, Christian Hopps <chopps@chopps.org>, "isis-wg@ietf.org" <isis-wg@ietf.org>
CC: "isis-ads@ietf.org" <isis-ads@ietf.org>, "draft-ietf-isis-segment-routing-msd@ietf.org" <draft-ietf-isis-segment-routing-msd@ietf.org>
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Date: Sat, 23 Dec 2017 04:32:58 +0000
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Hi Jeff,

As for per-link MSD information, I have the following comments:

1) I wonder whether you have considered the implementation differences on the label stack imposition process among different vendors. More specially, some chooses to impose the label stack on ingress line-cards while others choose to impose the label stack on egress line-cards due to different tradeoffs. For example, when a packet arrives at interface A of linecard X while departuring from interface B of linecard Y, assume the MSD type 1 values of linecard A and B are different, which interface's MSD value should be taken into account when calculating a SR path. Does it require IGP or BGP-LS to be extended to advertise the manner of label stack imposition of a given node as well (i.e., imposition on ingress or egress linecard)?

2) In the SID-binding case, if the incoming interface or outgoing interface for a given packet received by the Binding-SID anchor node is changed on the fly due to whatever reasons (e.g., FRR or ECMP ), how to deal with such case?

Best regards,
Xiaohu 

> -----邮件原件-----
> 发件人: Jeff Tantsura [mailto:jefftant.ietf@gmail.com]
> 发送时间: 2017年12月23日 2:50
> 收件人: Xuxiaohu; Les Ginsberg (ginsberg); Ketan Talaulikar (ketant); Christian
> Hopps; isis-wg@ietf.org
> 抄送: isis-ads@ietf.org; draft-ietf-isis-segment-routing-msd@ietf.org
> 主题: Re: 答复: 答复: [Isis-wg] WG Last Call for
> draft-ietf-isis-segment-routing-msd-07
> 
> Xiaohu,
> 
> PCEP and ISIS(OSPF) are quite different in their functionality and not meant to
> do the same thing. Wrt SR ecosystem, PCEP is optional, while IGP’s are
> mandatory.
> When it comes to a node capability, PCEP and IGP’s provide same information
> and fully aligned, however more granular, per link information is only available
> in IGPs, and this is as per design (not a bug).
> PCEP SR draft (which I’m co-author of) will be last called soon, please make
> sure you provide your comments to the PCE WG.
> 
> The intention of this thread is to last call draft-ietf-isis-segment-routing-msd,
> that has Type 1 defined and creates IANA registry for the future Types.
> I’d appreciate your comments specifically to the draft, and if you have got any
> technical objection, would be happy to address them.
> 
> Thanks!
> 
> Cheers,
> Jeff
> 
> -----Original Message-----
> From: Xuxiaohu <xuxiaohu@huawei.com>
> Date: Thursday, December 21, 2017 at 16:42
> To: Jeff Tantsura <jefftant.ietf@gmail.com>om>, "Les Ginsberg (ginsberg)"
> <ginsberg@cisco.com>om>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>om>,
> Christian Hopps <chopps@chopps.org>rg>, "isis-wg@ietf.org" <isis-wg@ietf.org>
> Cc: "isis-ads@ietf.org" <isis-ads@ietf.org>rg>,
> "draft-ietf-isis-segment-routing-msd@ietf.org"
> <draft-ietf-isis-segment-routing-msd@ietf.org>
> Subject: 答复: 答复: [Isis-wg] WG Last Call for
> draft-ietf-isis-segment-routing-msd-07
> 
>     Jeff,
> 
>     IMHO, the MSD or the MSD(type 1) just indicates a certain label imposition
> capability which should be signaling-agnostic. More specially, the MSD or
> MSD(type1) capability could be signaled via IGP, BGP or PCEP.
> 
>     If the semantic of MSD (type 1) as defined in your IGP-MSD draft equals the
> semantics of MSD as defined in PCEP-SR draft, I believe it'd better to iron out
> such terminology inconsistency ASAP.
> 
>     Best regards,
>     Xiaohu
> 
>     > -----邮件原件-----
>     > 发件人: Jeff Tantsura [mailto:jefftant.ietf@gmail.com]
>     > 发送时间: 2017年12月22日 5:22
>     > 收件人: Xuxiaohu; Les Ginsberg (ginsberg); Ketan Talaulikar (ketant);
> Christian
>     > Hopps; isis-wg@ietf.org
>     > 抄送: isis-ads@ietf.org; draft-ietf-isis-segment-routing-msd@ietf.org
>     > 主题: Re: 答复: [Isis-wg] WG Last Call for
> draft-ietf-isis-segment-routing-msd-07
>     >
>     > Xuxiaohu,
>     >
>     > To clarify:
>     > The concept had been developed in both, in parallel, however PCEP
>     > implementation is limited (node only, PCC in question has to have PCEP
> sessions
>     > with the PCE), and this is clearly stated in the draft – if MSD is known
> from both
>     > sources (PCEP and IGP/BGP-LS) the later takes precedence. IGP drafts are
> the
>     > source of truth when it comes to semantics definitions.
> 
> 
> 
>     > Personally, I don’t see any confusion wrt name, all drafts have been
> around for
>     > quite some time, reviewed by many people, presented in academia and
>     > networking events, noone was ever confused…
>     >
>     > I’m not sure about value of your proposal either, and I’d leave the
> decision
>     > what to use to people who are the consumers of the technology, those
> who are
>     > going to implement it (at least 3 MSD implementations are on their
> ways).
>     >
>     > As the last point – we are not “considering” expanding, the draft is clear
> about
>     > the future extensions to come and encoding is done in a way to facilitate
> such
>     > extensions.
>     > This is the working group last call for the draft, not a discussion whether
> we
>     > should proceed with the technology:
>     > If you see any technical problems with the solution proposed – I’d be
> the first
>     > to listen to you and address them!
>     >
>     > Happy holidays!
>     >
>     > Cheers,
>     > Jeff
>     >
>     > -----Original Message-----
>     > From: Xuxiaohu <xuxiaohu@huawei.com>
>     > Date: Wednesday, December 20, 2017 at 18:40
>     > To: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>om>, "Ketan Talaulikar
> (ketant)"
>     > <ketant@cisco.com>om>, Christian Hopps <chopps@chopps.org>rg>,
> "isis-wg@ietf.org"
>     > <isis-wg@ietf.org>
>     > Cc: "isis-ads@ietf.org" <isis-ads@ietf.org>rg>,
>     > "draft-ietf-isis-segment-routing-msd@ietf.org"
>     > <draft-ietf-isis-segment-routing-msd@ietf.org>
>     > Subject: 答复: [Isis-wg] WG Last Call for
> draft-ietf-isis-segment-routing-msd-07
>     > Resent-From: <alias-bounces@ietf.org>
>     > Resent-To: <jefftant.ietf@gmail.com>om>, <uma.chunduri@huawei.com>om>,
>     > <aldrin.ietf@gmail.com>om>, <ginsberg@cisco.com>
>     > Resent-Date: Wed, 20 Dec 2017 18:40:16 -0800 (PST)
>     >
>     >     Hi Les,
>     >
>     >     If I understand it correctly, the MSD concept was originated from
>     > (https://tools.ietf.org/html/draft-ietf-pce-segment-routing-11#page-7) as
>     > described below:
>     >
>     >     "The "Maximum SID Depth" (1
>     >        octet) field (MSD) specifies the maximum number of SIDs (MPLS
> label
>     >        stack depth in the context of this document) that a PCC is
> capable of
>     >        imposing on a packet."
>     >
>     >     Before considering expanding the semantics of the MSD concept as
> defined
>     > in the above PCE-SR draft, how about first considering renaming the
> capability
>     > of imposing the maximum number of labels so as to eliminate possible
>     > confusions, e.g., Writable Label-stack Depth (WLD) as opposed to the
> Readable
>     > Label-stack Depth (RLD) as defined in
>     > (https://tools.ietf.org/html/draft-ietf-ospf-mpls-elc) and
>     > (https://tools.ietf.org/html/draft-ietf-isis-mpls-elc) ?
>     >
>     >     Best regards,
>     >     Xiaohu
>     >
>     >     > -----邮件原件-----
>     >     > 发件人: Isis-wg [mailto:isis-wg-bounces@ietf.org] 代表 Les
> Ginsberg
>     > (ginsberg)
>     >     > 发送时间: 2017年12月21日 4:02
>     >     > 收件人: Ketan Talaulikar (ketant); Christian Hopps;
> isis-wg@ietf.org
>     >     > 抄送: isis-ads@ietf.org;
> draft-ietf-isis-segment-routing-msd@ietf.org
>     >     > 主题: Re: [Isis-wg] WG Last Call for
> draft-ietf-isis-segment-routing-msd-07
>     >     >
>     >     > Ketan -
>     >     >
>     >     > Thanx for the comments.
>     >     > I think we do want to allow MSD support for values other than
> imposition
>     >     > values. We will revise the text so we are not restricted to only
> imposition
>     > cases.
>     >     >
>     >     >   Les
>     >     >
>     >     >
>     >     > > -----Original Message-----
>     >     > > From: Ketan Talaulikar (ketant)
>     >     > > Sent: Wednesday, December 20, 2017 1:51 AM
>     >     > > To: Christian Hopps <chopps@chopps.org>rg>; isis-wg@ietf.org
>     >     > > Cc: isis-ads@ietf.org;
> draft-ietf-isis-segment-routing-msd@ietf.org
>     >     > > Subject: RE: [Isis-wg] WG Last Call for
>     >     > > draft-ietf-isis-segment-routing-msd-07
>     >     > >
>     >     > > Hello,
>     >     > >
>     >     > > I support this document and would like to ask the authors and
> WG to
>     >     > > consider if we can expand the scope of this draft to not just
>     >     > > "imposition" of the SID stack but also other similar limits related
> to
>     > other
>     >     > actions (e.g.
>     >     > > reading, processing, etc.). With Segment Routing, we are coming
> across
>     >     > > various actions that nodes need to do with the SID stack for
> different
>     >     > > purposes and IMHO it would be useful to extend the MSD ability
> to
>     >     > > cover those as they arise.
>     >     > >
>     >     > > Thanks,
>     >     > > Ketan
>     >     > >
>     >     > > -----Original Message-----
>     >     > > From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of
> Christian
>     >     > > Hopps
>     >     > > Sent: 20 December 2017 14:03
>     >     > > To: isis-wg@ietf.org
>     >     > > Cc: isis-ads@ietf.org;
> draft-ietf-isis-segment-routing-msd@ietf.org
>     >     > > Subject: [Isis-wg] WG Last Call for
>     >     > > draft-ietf-isis-segment-routing-msd-07
>     >     > >
>     >     > >
>     >     > > The authors have asked for and we are starting a WG Last Call on
>     >     > >
>     >     > >
> https://datatracker.ietf.org/doc/draft-ietf-isis-segment-routing-msd/
>     >     > >
>     >     > > which will last an extended 4 weeks to allow for year-end PTO
> patterns.
>     >     > >
>     >     > > An IPR statement exists:
>     >     > >
>     >     > >
>     >     > >
> https://datatracker.ietf.org/ipr/search/?submit=draft&id=draft-ietf-is
>     >     > > is-
>     >     > > segment-routing-msd
>     >     > >
>     >     > > Authors please reply to the list indicating whether you are aware
> of
>     >     > > any
>     >     > > *new* IPR.
>     >     > >
>     >     > > Thanks,
>     >     > > Chris.
>     >     > >
>     >     > > _______________________________________________
>     >     > > Isis-wg mailing list
>     >     > > Isis-wg@ietf.org
>     >     > > https://www.ietf.org/mailman/listinfo/isis-wg
>     >     >
>     >     > _______________________________________________
>     >     > Isis-wg mailing list
>     >     > Isis-wg@ietf.org
>     >     > https://www.ietf.org/mailman/listinfo/isis-wg
>     >
>     >
> 
> 
>