Re: [spring] Understanding the replication draft
"Xiejingrong (Jingrong)" <xiejingrong@huawei.com> Tue, 14 July 2020 11:55 UTC
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From: "Xiejingrong (Jingrong)" <xiejingrong@huawei.com>
To: Rishabh Parekh <rishabhp@gmail.com>, Jeff Tantsura <jefftant.ietf@gmail.com>
CC: Dhruv Dhody <dhruv.ietf@gmail.com>, "bruno.decraene@orange.com" <bruno.decraene@orange.com>, "spring@ietf.org" <spring@ietf.org>, Alexander Vainshtein <Alexander.Vainshtein@rbbn.com>
Thread-Topic: [spring] Understanding the replication draft
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Date: Tue, 14 Jul 2020 11:55:07 +0000
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References: <94415742-fc4e-1774-bf96-01eac3672bfb@joelhalpern.com> <CABjMoXYCsXb-iP55PsNWHBG187Lm7-2PXfgD3qRn_aD6ppDuMw@mail.gmail.com> <b3aaaa47-af61-6fc0-1086-bfd59efea061@joelhalpern.com> <CABjMoXY5S1Bx3rQM-0eyJfzh9iOgAZoGshs1wFqebnkVZ++G0w@mail.gmail.com> <CAOj+MMFsjRCgbY1V5idoKmqKR7W5gwM7ui7cp6W12GQm0XEHyQ@mail.gmail.com> <CABjMoXbka+L3STNd4EPOfT5KA35ECZQt3jk=g0m=GU9VUj9csA@mail.gmail.com> <baaf7a09-f20d-4863-b7f7-36118e11cc4b@Spark> <CABjMoXZaiED+++2ij6CB_MH6dqGgs=t829XgsYy+6HHC69SDrQ@mail.gmail.com> <CAB75xn7f0RaMPhmN2KH26Z--8pp-ioGCMGSC+0MOx1T=Ugp+xg@mail.gmail.com> <32104_1594114929_5F044371_32104_68_5_53C29892C857584299CBF5D05346208A48EC8CCE@OPEXCAUBM43.corporate.adroot.infra.ftgroup> <CAB75xn6CQsTEtDfR_UoRQCfgYUAFcjDyxBn1SidZx2EwK+9WTA@mail.gmail.com> <DB7PR03MB4505877740699D5EFD4EA64A9D660@DB7PR03MB4505.eurprd03.prod.outlook.com> <3d5c2f1b-d033-41ca-a59d-6c74addcc08c@Spark> <CABjMoXZ=+g0+4tv=U_nG+_85h830gfG7D7mQuAw09wQOvtgTWw@mail.gmail.com>
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Subject: Re: [spring] Understanding the replication draft
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Hi The rev-04 says “The Replication SID MUST be the last SID (at the bottom of stack for SR-MPLS) in a packet that is steered out from a Replication node of a Replication Segment.”. I feel a little hard to understand …… My question is: Can an “MPLS packet” be carried over the P2MP policy ? say a packet like this: { Replication SID, (VPN Label, IPv4/IPv6 C-multicast packet) } ? In my understanding, with an imagined topology comprising of Replication Node R1/R2/R3/R4, the picture is like this: The Replication Node R2 receives such a packet (from R1), sees the Replication SID<R2> on the “Top” of the label stack, performs the corresponding action of “replication”, replicates the packet to downstream Replication Nodes R3 and R4, SWAPs the Replication SID<R2> to Replication SID<R3> and Replication SID<R4> respectively. The Replication Node R3 receives the packet { Replication SID<R3>, (VPN Label, IPv4/IPv6 C-multicast packet) }. The Replication Node R4 receives the packet { Replication SID<R4>, (VPN Label, IPv4/IPv6 C-multicast packet) }. Thanks Jingrong From: spring [mailto:spring-bounces@ietf.org] On Behalf Of Rishabh Parekh Sent: Saturday, July 11, 2020 4:46 AM To: Jeff Tantsura <jefftant.ietf@gmail.com> Cc: Dhruv Dhody <dhruv.ietf@gmail.com>; bruno.decraene@orange.com; spring@ietf.org; Alexander Vainshtein <Alexander.Vainshtein@rbbn.com> Subject: Re: [spring] Understanding the replication draft All, We have posted revision 04<https://tools.ietf.org/html/draft-voyer-spring-sr-replication-segment-04> of the draft. This addresses comments on this thread and adds an example illustrating replication segment. Diff from rev 03: https://tinyurl.com/y96ueb9h Some WG members also wanted to understand how Replication segments are stitched together to form a P2MP tree based on SR P2MP policy in the PIM draft. We have posted revision 02<https://tools.ietf.org/html/draft-voyer-pim-sr-p2mp-policy-02> of PIM P2MP policy draft that adds examples of how these things tie together. I hope that helps clarify the relationship. Diff from rev 01: https://tinyurl.com/yban2jp6 Please review, -Rishabh On Tue, Jul 7, 2020 at 2:16 PM Jeff Tantsura <jefftant.ietf@gmail.com<mailto:jefftant.ietf@gmail.com>> wrote: Thanks Rishabh! +1 to the above comments and looking forward to the updated draft. Cheers, Jeff On Jul 7, 2020, 7:35 AM -0700, Alexander Vainshtein <Alexander.Vainshtein@rbbn.com<mailto:Alexander.Vainshtein@rbbn.com>>, wrote: Dhruv, Bruno and all, Regarding the statement " What is missing in the spring I-D is some very high level discussion in terms of architecture on how replication segment and SR P2MP policy come together" - I cannot agree more. My 2c, Sasha Office: +972-39266302 Cell: +972-549266302 Email: Alexander.Vainshtein@ecitele.com<mailto:Alexander.Vainshtein@ecitele.com> -----Original Message----- From: spring <spring-bounces@ietf.org<mailto:spring-bounces@ietf.org>> On Behalf Of Dhruv Dhody Sent: Tuesday, July 7, 2020 1:02 PM To: bruno.decraene@orange.com<mailto:bruno.decraene@orange.com> Cc: spring@ietf.org<mailto:spring@ietf.org> Subject: Re: [spring] Understanding the replication draft Hi Bruno, Yes, thanks! I was just making sure that we have an agreement that PIM is the right place to define SR P2MP Policy. What is missing in the spring I-D is some very high level discussion in terms of architecture on how replication segment and SR P2MP policy come together. The current I-D tries to define a replication segment as an independent entity that could be used on its own but it makes it difficult to visualize without some high level text or an example. Thanks! Dhruv On Tue, Jul 7, 2020 at 3:12 PM <bruno.decraene@orange.com<mailto:bruno.decraene@orange.com>> wrote: > > Hi Dhruv, > > > -----Original Message----- > > From: spring [mailto:spring-bounces@ietf.org<mailto:spring-bounces@ietf.org>] On Behalf Of Dhruv > > Dhody > > Subject: Re: [spring] Understanding the replication draft > > > > Hi WG, > > > > Reading the I-D and based on the discussion on this thread I believe > > more description is required. As Joel pointed out, clarity on what > > is legal/illegal (or out of scope for now) is needed. > > I leave this for the authors to reply. > > > I have no strong opinion if that needs to be done before or after adoption! > > > > I do not follow PIM closely and just realized that the SR P2MP > > Policy in the PIM I-D [1] is adopted by the PIM WG, but not yet posted [2]. > > I wanted to make sure that it has been decided that PIM is the right > > place to define SR P2MP policy (discussed either in the WG and/or > > between chairs/AD)? > > draft-voyer-pim-sr-p2mp-policy-00 is to be worked in the PIM WG. > The PIM WG is waiting for the SPRING WG to adopt draft-voyer-spring-sr-replication-segment, since the -pim- document has a dependency on the -spring- document. > > Quoting the PIM chairs: "We have solid support to adopt this draft.. [...] We are waiting to hear back from the spring chairs as to the wg status of the local replication draft of which your draft is dependent.. So please hold off on submitting the new draft-ietf-pim-sr-p2mp-policy until they give us the green light." > > Does this answer your question? > > --Bruno > > > Thanks! > > Dhruv > > > > [1] > > https://clicktime.symantec.com/36sxrNPFssiaB8jE9mzzZDd6H2?u=https%3A > > %2F%2Fdatatracker.ietf.org<http://2Fdatatracker.ietf.org>%2Fdoc%2Fdraft-voyer-pim-sr-p2mp-policy%2F > > [2] > > https://clicktime.symantec.com/3LtBxbxRK3NkuKYc3FC7rr46H2?u=https%3A > > %2F%2Fmailarchive.ietf.org<http://2Fmailarchive.ietf.org>%2Farch%2Fmsg%2Fpim%2FYyF7I02aaRtpZngf7uTn > > o69IB90%2F > > > > > > > > On Thu, Jul 2, 2020 at 12:05 PM Rishabh Parekh <rishabhp@gmail...com<mailto:rishabhp@gmail...com>> > > wrote: > > > > > > Jeff, > > > Your explanation of distinct Transport SIDs and service labels > > > (which appear at BoS) applies to Point-to-Point services. Same > > > model can be applied when a Point-to-Multipoint service is > > > realized by one end-to-end replication segment; "Downstream > > > Replication SID" as specified in draft is effectively the service > > > label at a specific downstream node of a Replication segment with > > > Transport SIDs imposed on top to take replicated packet to that node. > > > > > > However, when a Point-to-Multipoint service is over replication > > > segments stitched together to form a P2MP tree, as described in > > > PIM WG draft, this model no longer holds since all service egress > > > nodes would have to agree on one common service label. So P2MP > > > services implicitly map the P2MP transport label (Replication SID > > > at BoS in this case) to the P2MP service. Of course, this implies > > > one-to-one association between a P2MP service and a P2MP > > > transport. There are techniques to share one P2MP transport across > > > different P2MP services using either upstream assigned label or a > > > global context from "Domain-wide Common Block" > > > (draft-ietf-bess-mvpn-evpn-aggregation-label). These and other > > > gory details are described in Section 2 of PIM WG draft and to > > > some extent in BESS MVPN-EVPN draft. > > > > > > -Rishabh > > > > > > On Wed, Jul 1, 2020 at 5:50 PM Jeff Tantsura > > > <jefftant.ietf@gmail.com<mailto:jefftant.ietf@gmail.com>> > > wrote: > > > > > > > > Rishabh, > > > > > > > > Transport SID with a service on top can’t be a BoS label, > > > > there’s s service > > label below, since a service is associated with a particular node, > > there would be at least a N-SID associated with the service node. > > > > It seems like B-SID behavior is the correct one, when R-SID is > > > > looked up > > and popped, it would yield: replication (as programmed by a > > controller, since there’s no state) + new label stack associated > > with the new, post replication/branching path that is imposed on top > > of existing label stack, so service label ( + optionally more transport labels) are preserved. > > > > > > > > Cheers, > > > > Jeff > > > > On Jul 1, 2020, 12:40 PM -0700, Rishabh Parekh > > > > <rishabhp@gmail.com<mailto:rishabhp@gmail.com>>, > > wrote: > > > > > > > > Robert, > > > > > > > > A) Firmly state that replication SID MUST be the last one on the > > > > stack > > > > B) Instead of real SID after the replication SID provide a > > > > binding SID which > > locally will be mapped to a different SID list imposed to each replicated flow. > > > > > > > > > > > > We would be fine with A), but we don't want to exclude > > > > possibility of something like what you describe in B. > > > > > > > > -Rishabh > > > > > > > > On Wed, Jul 1, 2020 at 12:27 PM Robert Raszuk > > > > <robert@raszuk.net<mailto:robert@raszuk.net>> > > wrote: > > > > > > > > > > > > Hi Rishabh, > > > > > > > > Of course, care must be > > > > taken to avoid the "explosion" as you describe it.. G-SID-2 has > > > > to map to a unique node; for example, it may be an Anycast-SID > > > > that takes packet to distinct nodes from each of the downstream > > > > node, or the downstream nodes can be border nodes connecting to > > > > other segment routing domains where G-SID-2 resolves to distinct > > > > nodes in each domain. > > > > > > > > > > > > I think you are stretching it too thin. > > > > > > > > See even if G-SID-2 is anycast SID you have zero assurance that > > > > physical > > nodes packets will land on would be at all diverse. > > > > > > > > Likewise crossing domains yet providing identical global SID now > > > > to be a > > different node in each such domain to me is not a realistic example. > > > > > > > > I think we have two options: > > > > > > > > A) Firmly state that replication SID MUST be the last one on the > > > > stack > > > > > > > > B) Instead of real SID after the replication SID provide a > > > > binding SID which > > locally will be mapped to a different SID list imposed to each replicated flow. > > > > > > > > What is currently in the draft seems to be very counterintuitive > > > > and IMHO > > will result in operational difficulties. > > > > > > > > Thx a lot, > > > > R. > > > > > > > > > > > > _______________________________________________ > > > > spring mailing list > > > > spring@ietf.org<mailto:spring@ietf.org> > > > > https://clicktime..symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https<https://clicktime.symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https> > > > > %3A%2F%2Fwww.ietf.org<http://2Fwww.ietf.org>%2Fmailman%2Flistinfo%2Fspring > > > > > > _______________________________________________ > > > spring mailing list > > > spring@ietf.org<mailto:spring@ietf.org> > > > https://clicktime.symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https%3<https://clicktime.symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https%253> > > > A%2F%2Fwww.ietf.org<http://2Fwww.ietf.org>%2Fmailman%2Flistinfo%2Fspring > > > > _______________________________________________ > > spring mailing list > > spring@ietf.org<mailto:spring@ietf.org> > > https://clicktime.symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https%3A%<https://clicktime.symantec.com/3U9X5zkPbKst7T8373JWnS6H2?u=https%3A%25> > > 2F%2Fwww.ietf..org<http://2Fwww.ietf.org>%2Fmailman%2Flistinfo%2Fspring > > ______________________________________________________________________ > ___________________________________________________ > > Ce message et ses pieces jointes peuvent contenir des informations > confidentielles ou privilegiees et ne doivent donc pas etre diffuses, > exploites ou copies sans autorisation. 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- [spring] Understanding the replication draft Joel M. Halpern
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Joel Halpern Direct
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Robert Raszuk
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Joel M. Halpern
- Re: [spring] Understanding the replication draft Joel M. Halpern
- Re: [spring] Understanding the replication draft Robert Raszuk
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Joel M. Halpern
- Re: [spring] Understanding the replication draft Jeff Tantsura
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Dhruv Dhody
- Re: [spring] Understanding the replication draft bruno.decraene
- Re: [spring] Understanding the replication draft Dhruv Dhody
- Re: [spring] Understanding the replication draft Alexander Vainshtein
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Jeff Tantsura
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Xiejingrong (Jingrong)
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Xiejingrong (Jingrong)
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Xiejingrong (Jingrong)
- Re: [spring] Understanding the replication draft Rishabh Parekh
- Re: [spring] Understanding the replication draft Xiejingrong (Jingrong)