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:[email protected]] > 发送时间: 2017年12月23日 2:50 > 收件人: Xuxiaohu; Les Ginsberg (ginsberg); Ketan Talaulikar (ketant); Christian > Hopps; [email protected] > 抄送: [email protected]; [email protected] > 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 <[email protected]> > Date: Thursday, December 21, 2017 at 16:42 > To: Jeff Tantsura <[email protected]>, "Les Ginsberg (ginsberg)" > <[email protected]>, "Ketan Talaulikar (ketant)" <[email protected]>, > Christian Hopps <[email protected]>, "[email protected]" <[email protected]> > Cc: "[email protected]" <[email protected]>, > "[email protected]" > <[email protected]> > 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:[email protected]] > > 发送时间: 2017年12月22日 5:22 > > 收件人: Xuxiaohu; Les Ginsberg (ginsberg); Ketan Talaulikar (ketant); > Christian > > Hopps; [email protected] > > 抄送: [email protected]; [email protected] > > 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 <[email protected]> > > Date: Wednesday, December 20, 2017 at 18:40 > > To: "Les Ginsberg (ginsberg)" <[email protected]>, "Ketan Talaulikar > (ketant)" > > <[email protected]>, Christian Hopps <[email protected]>, > "[email protected]" > > <[email protected]> > > Cc: "[email protected]" <[email protected]>, > > "[email protected]" > > <[email protected]> > > Subject: 答复: [Isis-wg] WG Last Call for > draft-ietf-isis-segment-routing-msd-07 > > Resent-From: <[email protected]> > > Resent-To: <[email protected]>, <[email protected]>, > > <[email protected]>, <[email protected]> > > 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:[email protected]] 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; > [email protected] > > > 抄送: [email protected]; > [email protected] > > > 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 <[email protected]>; [email protected] > > > > Cc: [email protected]; > [email protected] > > > > 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:[email protected]] On Behalf Of > Christian > > > > Hopps > > > > Sent: 20 December 2017 14:03 > > > > To: [email protected] > > > > Cc: [email protected]; > [email protected] > > > > 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 > > > > [email protected] > > > > https://www.ietf.org/mailman/listinfo/isis-wg > > > > > > _______________________________________________ > > > Isis-wg mailing list > > > [email protected] > > > https://www.ietf.org/mailman/listinfo/isis-wg > > > > > > > _______________________________________________ Isis-wg mailing list [email protected] https://www.ietf.org/mailman/listinfo/isis-wg
