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 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)? Thanks! Dhruv [1] https://datatracker.ietf.org/doc/draft-voyer-pim-sr-p2mp-policy/ [2] https://mailarchive.ietf.org/arch/msg/pim/YyF7I02aaRtpZngf7uTno69IB90/ On Thu, Jul 2, 2020 at 12:05 PM Rishabh Parekh <risha...@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.i...@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 <risha...@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 <rob...@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 > > https://www.ietf.org/mailman/listinfo/spring > > _______________________________________________ > spring mailing list > spring@ietf.org > https://www.ietf.org/mailman/listinfo/spring _______________________________________________ spring mailing list spring@ietf.org https://www.ietf.org/mailman/listinfo/spring
