Hi Tony, Just so we are on same page, I think you are agreeing on the overhead per MT (and even MI) that would be incurred using the approach proposed in I-D. draft-xie-lsr-isis-sr-vtn-mt to realize a forwarding treatment on a shared resource.
To you’re point on flex-algo producing disconnected topologies, I-D.draft-bestbar-lsr-spring-sa is NOT adding any **new** considerations or a change that would impact the behavior for computing per prefix SID paths as described in I-D.draft-ietf-lsr-flex-algo. It is only proposing to associate a SID with a forwarding treatment. Regards, Tarek On 3/8/21, 9:54 AM, "Tony Przygienda" <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> wrote: [External Email. Be cautious of content] This argument seems fairly bogus to me. if you use IGP to flood some stuff and then want the distributed computation stitch it together based on IGP topology to get you a nexthop you end in computation which is something like Bellman or Dijkstra or Boruvka. Unless you have some controller distributing next-hops but then it's really PCE and not IGP AFAIS. The difference in MI and MT is that MT carries the topology information everywhere (you don't have to compute if you're not part of [simple check on adjacencies] it but you still get stuff flooded). Some people like that (manageability), some don't. IS does only flood to nodes connected in MI. Operationally I learned ages ago that topologies disconnecting are some of the most vexing scenarios and there MT is @ an advantage since partitioned topology can be easily derived (and that's BTW why it's built that way with strict adjacency negotiation). Reading the bestbar draft and looking @ e.g. flex algo I am waiting to see how the "I cannot get there, why?" problems On Mon, Mar 8, 2021 at 3:43 PM Tarek Saad <ts...@juniper.net<mailto:ts...@juniper.net>> wrote: Hi authors, My understanding is the draft is proposing a separate MT topology (unique MT-ID) to identify a forwarding treatment to be enforced on a shared resource. While this may work for limited number of MT topologies (i.e. forwarding treatments), as described in RF5120 there is overhead with creating/advertising and managing and running separate SPF for each of the MT topology. This will restrict the scalability of such approach (number of forwarding treatments to be realized) using this approach. In I-D.draft-bestbar-lsr-spring-sa we are proposing carrying an independent ID (associated with the forwarding treatment) independent of the topology ID. This allows the # of forwarding treatmentst to be independent of the # of MT topologies that need to be managed by IGP; and hence, allow it to scale. Your feedback on this approach is welcome. Regards, Tarek On 3/8/21, 9:29 AM, "Lsr on behalf of Dongjie (Jimmy)" <lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org> on behalf of jie.d...@huawei.com<mailto:jie.d...@huawei.com>> wrote: Hi Gyan, Thanks for your comments. As you mentioned, both MT and MI can provide separate topologies and the topology based computation, and MI can provide separate LSDBs at some additional cost (separate adjacencies, etc.). In this document, the resource of VTN mainly refers to the forwarding plane resources, thus MT is chosen as it can provide the required functionality with less overhead. Hope this helps. Best regards, Jie From: Lsr [mailto:lsr-boun...@ietf.org<mailto:lsr-boun...@ietf.org>] On Behalf Of Gyan Mishra Sent: Monday, March 8, 2021 7:29 AM To: Tony Przygienda <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> Cc: Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org<mailto:40cisco....@dmarc.ietf.org>>; Chongfeng Xie <chongfeng....@foxmail.com<mailto:chongfeng....@foxmail.com>>; Acee Lindem (acee) <a...@cisco.com<mailto:a...@cisco.com>>; Robert Raszuk <rob...@raszuk.net<mailto:rob...@raszuk.net>>; lsr@ietf.org<mailto:lsr@ietf.org> Subject: Re: [Lsr] WG Adoption Poll for “Using IS-IS Multi-Topology (MT) for Segment Routing based Virtual Transport Network” - draft-xie-lsr-isis-sr-vtn-mt-03 Dear Authors Why was MT chosen and not MI for VTN underlay network slice underpinning. MT instances has separate topology but not separate LSDB where MI Multi instance RFC 6822 has a separate LSDB for resources isolation and I think would be a better fit for VTN underlay provisioning. MI https://tools.ietf.org/html/rfc6822<https://urldefense.com/v3/__https:/tools.ietf.org/html/rfc6822__;!!NEt6yMaO-gk!W0I8TTnvfmnvtp4AbIlYuPMM8_M1XF91FAbQTNSjvXvd9Qq8qoW8C7H7OSh6fw$> Thanks Gyan On Sun, Mar 7, 2021 at 10:34 AM Tony Przygienda <tonysi...@gmail.com<mailto:tonysi...@gmail.com>> wrote: Robert ruminated: That said I think perhaps we are indeed missing LROW WG (Local Routing Operations WG) where just like in GROW WG where mainly (Global) BGP operational aspects are discussed there could be good place to discuss operational aspects of link state protocols deployment and use cases. In fact perhaps it would also free some LSR bandwidth to really focus on protocol extensions. +1 IGPs grew a zoo of horns and bells by now and no'one tells the operators which spines are poisonous ;-) --- tony _______________________________________________ Lsr mailing list Lsr@ietf.org<mailto:Lsr@ietf.org> https://www.ietf.org/mailman/listinfo/lsr<https://urldefense.com/v3/__https:/www.ietf.org/mailman/listinfo/lsr__;!!NEt6yMaO-gk!W0I8TTnvfmnvtp4AbIlYuPMM8_M1XF91FAbQTNSjvXvd9Qq8qoW8C7HiECKYfg$> -- [图像已被发件人删除。]<https://urldefense.com/v3/__http:/www.verizon.com/__;!!NEt6yMaO-gk!W0I8TTnvfmnvtp4AbIlYuPMM8_M1XF91FAbQTNSjvXvd9Qq8qoW8C7FBSt5CLg$> Gyan Mishra Network Solutions Architect M 301 502-1347 13101 Columbia Pike Silver Spring, MD Juniper Business Use Only Juniper Business Use Only
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