Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-attr-reuse-00
Peter Psenak <ppsenak@cisco.com> Fri, 13 November 2015 17:24 UTC
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Date: Fri, 13 Nov 2015 18:24:44 +0100
From: Peter Psenak <ppsenak@cisco.com>
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To: julien.meuric@orange.com, "Acee Lindem (acee)" <acee@cisco.com>, Jeff Tantsura <jeff.tantsura@ericsson.com>
References: <D24CF2B7.37452%acee@cisco.com> <BLUPR05MB292E9628E4172C733C59BA8A9380@BLUPR05MB292.namprd05.prod.outlook.com> <5627CDF6.605@cisco.com> <BLUPR05MB292B99DA8B1B9E253A0E83BA9380@BLUPR05MB292.namprd05.prod.outlook.com> <5627F457.8020701@cisco.com> <BLUPR05MB2927E888C41831AF2786280A9270@BLUPR05MB292.namprd05.prod.outlook.com> <CAG4d1rctdk6QcrhjEj2n-1VM2HTzQJvFxgamneis+fsiH0rcTw@mail.gmail.com> <562917FE.6070100@cisco.com> <D252C136.384AC%acee@cisco.com> <E70EB200-09AE-464C-A0B2-38F480489F16@ericsson.com> <563B0F53.8010803@orange.com> <563B15E0.90101@cisco.com> <563B2978.10507@orange.com> <D263B0C8.3CC87%acee@cisco.com> <5642209B.3010304@orange.com> <56447BC1.9080409@cisco.com> <16755_1447433279_5646143F_16755_202_1_5646143E.8000701@orange.com>
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Subject: Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-attr-reuse-00
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Hi Julien, please see inline: On 11/13/15 17:47 , julien.meuric@orange.com wrote: > Hi Peter, > > See [JM] below. > > > Nov. 12, 2015 - ppsenak@cisco.com: >> Julien, >> >> On 11/10/15 17:51 , Julien Meuric wrote: >>> Hi Acee, >>> >>> I think we do not need to agree on the philosophical question whether >>> defining detour path by packet header instead of signaling states brings >>> the feature out of TE... >>> >>> Anyway we agree that consolidating information from 3 separates LSA is >>> not the most efficient processing. My point is that this slight >>> improvement does not balance the risk of inconsistent >>> advertisements/configuration that the current I-D does not (even try to) >>> prevent. >> >> let me disagree. Current I-D clearly states what TE Opaque LSAs are used >> for. > > [JM] I am happy to quote Jeff on this: "thanks to GMPLS IGP extensions > as per RFC's 4203 & 5307 SRLG info is there, it is up to implementation > how to use it." > (https://mailarchive.ietf.org/arch/msg/rtgwg/yURBLVi2LqrEz33wKkauV0j9cmA) Jeff is a co-author of the ospf-te-link-attr-reuse, so I let him express his opinion, but he has responded on the list already saying: "I'm familiar with at least 2 implementations which have this issue, this draft solves real problem." > >> >> The risk is when you do what you propose to do as it breaks the existing >> TE > > [JM] This is different from Acee's point: "usage of the TE LSAs for > non-TE purposes was NEVER standardized". It is not about breaking, it is > about documenting use cases beyond the original one. > > - e.g. you advertise the link in TE Opaque LSA and some remote router >> would try to establish a TE path via such link, even though the link is >> not enabled for that. Result is that the signaling would keep failing or >> in worst case, when signaling is not involved, traffic will be dropped >> when trying to use such link. > > [JM] Supposing I am an operator who is playful enough to manage a > network area using a topology for TE traffic that does not match the > IP/LDP topology (you may find this realistic, I do not). Then, a router > ignoring that an SRLG-enabled link has no available bandwidth/a specific > affinity/a non-PSC switching capability/etc. is misbehaving. well, that is not necessarily true, for example 0 bandwidth tunnels are often used. RFC3630 does not mandate bandwidth, affinity or any other link attributes in TE Opaque LSAs. Link Type and Link ID sub-TLVs are mandatory, rest are optional. > > Anyway, this moves beyond the issue at stake here. Acee states that some > implementations need new definitions to go beyond the original use case. > I would like to limit the number of fields opening the doors to > operational inconsistencies. In these regards, an "applicability > statement of TE LSA parameters beyond MPLS-TE" may be a way to address > our concerns. I'm afraid we can not afford to change the RCF that has been published 12 years back. This would make it backward incompatible. > > Enjoy the week-end, you too! thanks, Peter > > Julien > > >> >> >> regards, >> Peter >> >>> >>> Regards, >>> >>> Julien >>> >>> >>> Nov. 07, 2015 - acee@cisco.com: >>>> Hi Julien, >>>> >>>> One such non-TE application where there is a clear advantage of >>>> advertising these attributes is segment routing TI-LFA. In addition to >>>> all >>>> the detriments of requiring advertisement of TE LSAs when TE is not >>>> enabled, one would need to consolidate information for a link from 3 >>>> separate LSAs (the base Router-LSA, the prefix-list attribute LSA for >>>> the >>>> adjacency SID, and the TE LSA). Clearly, it is better to advertise the >>>> applicable attributes in the Prefix/Link Attribute LSA and reduce this >>>> burden. You will note that this advantage isn’t apparent in IS-IS where >>>> everything is advertised in one monolithic LSP. >>>> >>>> Thanks, >>>> Acee >>>> >>>> On 11/5/15, 7:03 PM, "OSPF on behalf of Julien Meuric" >>>> <ospf-bounces@ietf.org on behalf of julien.meuric@orange.com> wrote: >>>> >>>>> Hello Peter, >>>>> >>>>> Nov. 05, 2015 - ppsenak@cisco.com: >>>>>> Hi Julien, >>>>>> >>>>>> On 11/5/15 09:12 , Julien Meuric wrote: >>>>>>> Hi Jeff, >>>>>>> >>>>>>> Following the WG session yesterday, I'm glad to (lately) join the >>>>>>> thread. Please, see my comments below as [JM]. >>>>>>> >>>>>>> >>>>>>> Oct. 26, 2015 - jeff.tantsura@ericsson.com: >>>>>>>> Hi, >>>>>>>> No hats >>>>>>>> >>>>>>>> I'm familiar with at least 2 implementations which have this issue, >>>>>>>> this draft solves real problem. >>>>>>>> >>>>>>>> Regards, >>>>>>>> Jeff >>>>>>> >>>>>>> [JM] Then you may consider patching them to do parameter >>>>>>> duplication on >>>>>>> the receiver side, not on the wire and/or the emitter >>>>>>> configuration... >>>>>>> Do you imagine operational people tearing hair out while trying to >>>>>>> guess >>>>>>> if they need to configure SRLGs in here, there or both? All the >>>>>>> more as >>>>>>> two places would multiply configuration discrepancies. >>>>>> >>>>>> above is incorrect. >>>>>> Nobody is proposing to configure things like SRLG on multiple places. >>>>> [JM] Actually you do in the I-D: "it is expected that the information >>>>> would be identical. If they are different..." >>>>> >>>>>> You configure it on a single place, as you do today. If IGP is >>>>>> enabled >>>>>> for global SRLG protection, IGP pulls the SRLGs and advertise them in >>>>>> the Extended Prefix LSA. If TE is enabled and want to use SRLGs, it >>>>>> pulls it from the same place, form the TE Opaque LSA and asks IGP to >>>>>> flood it. >>>>> [JM] This reads to me like "in case both types of LSAs are used, >>>>> values >>>>> MUST be identical". This is very different from the loose text in your >>>>> I-D. >>>>> >>>>>> >>>>>>> >>>>>>> In the I-D, the beginning and the end of section 3.1 provide a good >>>>>>> summary: >>>>>>> - "One approach for advertising link attributes is to _continue_ to >>>>>>> use >>>>>>> TE Opaque LSA" >>>>>>> - advantages: "no additional standardization requirement", "link >>>>>>> attributes are only advertised once". >>>>>>> I cannot agree more on these. >>>>>> >>>>>> have you read the "disadvantage" section as well? >>>>> [JM] Of course not, since Shraddha already solved them in his original >>>>> e-mail. :-) >>>>> >>>>>>> >>>>>>> In other words, some new use cases, not matching the original >>>>>>> one, do >>>>>>> not justify to allocate new code points to the same information (cf. >>>>>>> IS-IS non-issue). In the IETF, uses cases aim at scoping protocol >>>>>>> work, >>>>>>> they aren't made to limit protocol future uses. >>>>>> >>>>>> I;m afraid you are missing the point. >>>>>> TE Opaquer LSA are defined as LSAs that advertise TE topology that is >>>>>> disjoint from the IGP topology (RFC3630). We can NOT make the link >>>>>> part >>>>>> of the TE topology, just because we want to advertise SRLG or some >>>>>> other >>>>>> attribute that is used by IGP for LFA - that would break the RFC3630. >>>>> [JM] Indeed, I am missing the point where a link state protocol is >>>>> forbidden to access the link parameters it is distributing in its link >>>>> state advertisements. Please, point me to the section from RFC 3630 it >>>>> "breaks". >>>>> >>>>>> >>>>>> thanks, >>>>>> Peter >>>>>> >>>>> [JM] You're welcome, >>>>> >>>>> Julien >>>>> >>>>>>> >>>>>>> Cheers, >>>>>>> >>>>>>> Julien >>>>>>> >>>>>>> _______________________________________________ >>>>>>> OSPF mailing list >>>>>>> OSPF@ietf.org >>>>>>> https://www.ietf.org/mailman/listinfo/ospf >>>>>>> . >>>>>>> >>>>>> >>>>> >>>>> _______________________________________________ >>>>> OSPF mailing list >>>>> OSPF@ietf.org >>>>> https://www.ietf.org/mailman/listinfo/ospf >>>> >>> . >>> >> > > _________________________________________________________________________________________________________________________ > > > 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. Si vous avez > recu ce message par erreur, veuillez le signaler > a l'expediteur et le detruire ainsi que les pieces jointes. Les messages > electroniques etant susceptibles d'alteration, > Orange decline toute responsabilite si ce message a ete altere, deforme > ou falsifie. Merci. > > This message and its attachments may contain confidential or privileged > information that may be protected by law; > they should not be distributed, used or copied without authorisation. > If you have received this email in error, please notify the sender and > delete this message and its attachments. > As emails may be altered, Orange is not liable for messages that have > been modified, changed or falsified. > Thank you. > > . >
- [OSPF] Regarding draft-ppsenak-ospf-te-link-attr-… Shraddha Hegde
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Chris Bowers
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Chris Bowers
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Chris Bowers
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Alia Atlas
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Jeff Tantsura
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Julien Meuric
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Julien Meuric
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Julien Meuric
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Julien Meuric
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… julien.meuric
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Peter Psenak
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Acee Lindem (acee)
- Re: [OSPF] Regarding draft-ppsenak-ospf-te-link-a… Jeff Tantsura