Re: [Lsr] Question about draft-ppsenak-lsr-igp-ureach-prefix-announce
Robert Raszuk <robert@raszuk.net> Fri, 05 August 2022 13:09 UTC
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From: Robert Raszuk <robert@raszuk.net>
Date: Fri, 05 Aug 2022 15:09:03 +0200
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To: Peter Psenak <ppsenak=40cisco.com@dmarc.ietf.org>
Cc: Huzhibo <huzhibo@huawei.com>, "lsr@ietf.org" <lsr@ietf.org>
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Subject: Re: [Lsr] Question about draft-ppsenak-lsr-igp-ureach-prefix-announce
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Peter, Side question ... Assume PE participates in 10 end to end flex-algos. However BGP advertises 100K service routes with base 0 nh 1.1.1.1/32 Are you stating that BGP should advertise 100K routes 10 times with different IP address ? Note that mapping to flex-algo may not be prefix based on the number of forwarding paradigms. Yet UPA seems to be only prefix based. Was this case discussed in any document/thread so far ? Thx, R. . On Fri, Aug 5, 2022 at 12:16 PM Peter Psenak <ppsenak= 40cisco.com@dmarc.ietf.org> wrote: > Zhibo, > > On 05/08/2022 05:49, Huzhibo wrote: > > Peter: > > > >> -----Original Message----- > >> From: Peter Psenak [mailto:ppsenak@cisco.com] > >> Sent: Friday, August 5, 2022 1:55 PM > >> To: Huzhibo <huzhibo@huawei.com> > >> Cc: lsr@ietf.org > >> Subject: Re: Question about draft-ppsenak-lsr-igp-ureach-prefix-announce > >> > >> Zhibo, > >> > >> On 03/08/2022 21:09, Huzhibo wrote: > >>> Hi Peter: > >>> Please see inline. > >>> > >>>> -----Original Message----- > >>>> From: Peter Psenak [mailto:ppsenak@cisco.com] > >>>> Sent: Wednesday, August 3, 2022 11:20 PM > >>>> To: Huzhibo <huzhibo@huawei.com> > >>>> Cc: lsr@ietf.org > >>>> Subject: Re: Question about > >>>> draft-ppsenak-lsr-igp-ureach-prefix-announce > >>>> > >>>> Hi Zhibo, > >>>> > >>>> On 29/07/2022 20:49, Huzhibo wrote: > >>>>> Hi Peter: > >>>>> > >>>>> Supplement to yesterday's online questions, If a node that does not > >>>>> support IP Flexalgo, which has a default route, should the node > >>>>> process the IP Flexalgo prefix as a UPA? > >>>> > >>>> - I assume you are talking about the algo 0 default route. Because IP > >>>> Flex-algo default route does not make much sense really. > >>>> > >>>> - If the node does not support IP flex-algo, than it would not use > >>>> any IP algo prefix as BGP service endpoint or for any other purpose. > >>>> > >>> > >>> Which IP Algo prefix as BGP service endpoint is not determined by the > ingress > >> node, Such as VXLAN and SRv6 VPN. > >>> When the ingress node receives an BGP Service cayyied a IP algo prefix > >>> as endpoint and it has a algo 0 default route, it should be process > this BGP > >> service. and this can not be affected by the IGP Flexalgo prefix. > >> > >> sorry, but above is completely wrong. > >> > >> When you want to use IP flex-algo forwarding, you must advertise the > prefix as > >> algo prefix, relying on the algo 0 default would not give you algo > forwarding. > >> > >> Advertising IP algo prefix at the egress and relying in algo 0 default > at the > >> ingress is going to cause all sorts of problems. You CAN NOT mix/change > algos > >> along the path through the network - if you do, you may end up in a > permanent > >> loop. > > > > If the ingress node does not support Flexalgo, the ingress node does > not cause a > > permanent loop because once the packet is forwarded to the Flexalgo > node, it always > > follows Flexalgo forwarding. If the packet does not reach the Flexalgo > node, it always follows > > Algo 0 forwarding. > > well, flex-algo was design for end to end forwarding. Switching between > algos as packet traverses the network is not guaranteed to be loop free. > If you don't trust me, I let you figure that out yourself when you do > such a thing and it breaks. > > > > >> > >>> Therefore, > >>> the IGP does only not generate the RIB/Fib for LSinfinity Metric > prefix, but can > >> not trigger BGP Service Down. > >>> In addition, LSinfinity Metric may be applied to other scenarios in > >>> the future. We cannot guarantee that LSinfinity Metric will not > conflict with > >> other purposes when being processed as a UPA. > >> > >> no, it can not, because the LSinfinity has a very strict definition - > it means > >> unreachable, which is exactly what the UPA is about. > >> > > I believe you are confusing a concept. The LSInfinity metric defined in > RFC 5308 > > can be considered as zero route, but PUA/UPA actually defines a negative > route. > > It's not consistent > > I'm not confusing anything: > > rfc2328: > > LSInfinity > The metric value indicating that the destination described by an > LSA is unreachable. > > regards, > Peter > > > > > > >> Peter > >> > >>> > >>>> - If such node receives the IP algo prefix and even if it treats it > >>>> as UPA, given that such IP algo prefix was never reachable before on > >>>> this node, the UPA would result in no action. > >>>> > >>>> thanks, > >>>> Peter > >>>>> > >>>>> Thanks > >>>>> > >>>>> Zhibo > >>>>> > >>>> > >>> > >>> > >> > > > > > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr >
- [Lsr] Question about draft-ppsenak-lsr-igp-ureach… Huzhibo
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Huzhibo
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Aijun Wang
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Huzhibo
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Robert Raszuk
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Robert Raszuk
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Robert Raszuk
- Re: [Lsr] Question about draft-ppsenak-lsr-igp-ur… Peter Psenak