Hi Acee, Ketan and Aijun, I also agree that the introduction of source router ID could be a generic useful extension to OSPF, we already have this in IS-IS [RFC 7794].
As for the inter-area topology retrieval use case, I tend to agree that there can be multiple ways to achieve this, thus it would make sense to decouple this specific use case with the generic extension. Best regards, Jie > -----Original Message----- > From: Acee Lindem (acee) [mailto:[email protected]] > Sent: Tuesday, July 24, 2018 10:37 PM > To: Ketan Talaulikar (ketant) <[email protected]>; Peter Psenak (ppsenak) > <[email protected]>; Aijun Wang <[email protected]>; 'Rob Shakir' > <[email protected]> > Cc: Dongjie (Jimmy) <[email protected]>; [email protected]; [email protected] > Subject: Re: 答复: [Lsr] 答复: 答复: Regarding OSPF extension for inter-area > topology retrieval > > Hi Ketan, > > On 7/24/18, 7:44 AM, "Ketan Talaulikar (ketant)" <[email protected]> wrote: > > Hi Aijun, > > Your draft introduces the Source Router ID which is, by itself, an useful > protocol extension. > > I agree. What is the use case for advertisement in IS-IS? Perhaps this could > be > used as the primary motivation. > > > However, the use-case on inter-as topology retrieval has issues which has > been shared by many of us at the mike, offline and on the list. > > And this could be moved to an appendix or even completely. > > Thanks, > Acee > > Could you consider de-coupling the two? > > Also, if the proposal for learning inter-AS as described by you works for > your > own specific network design (and you don't think any of the points made affect > that decision), then please go ahead. However, I do not see the point of > trying to > get that as an IETF document? > > Thanks, > Ketan > > -----Original Message----- > From: Peter Psenak (ppsenak) > Sent: 24 July 2018 04:22 > To: Aijun Wang <[email protected]>; 'Rob Shakir' <[email protected]> > Cc: 'Dongjie (Jimmy)' <[email protected]>; [email protected]; Ketan > Talaulikar (ketant) <[email protected]>; [email protected]; Acee Lindem (acee) > <[email protected]> > Subject: Re: 答复: [Lsr] 答复: 答复: Regarding OSPF extension for > inter-area topology retrieval > > Hi Aijun, > > On 24/07/18 05:37 , Aijun Wang wrote: > > _Hi, Peter:_ > > > > For point-to-point interface, as described in OSPFv2(RFC2328 12.4.1.1. > Describing point-to-point interfaces) > <https://tools.ietf.org/html/rfc2328#page-130>, the router LSA will include > two > links description for each interface, within which the “type 3 link”(stub > network) > will describe the subnet mask of the point-to-point interface. > > > > For broadcast/NBMA interface, the DR will be elected and it will > > generate the network LSA which will include also the subnet mask of > > the connected interface. > > > > For unnumbered and virtual link, if you consider we should include > > them also for all possible scenarios even if we seldom use them in > > large network, we can consider expand the summary LSA to cover it, as > > done by this draft. > > there is no way to address unnumbered p2p case your way, because there is > no Summary LSA generated to other area in such case. > > Anyway, reconstructing a topology of a remote area based on the prefix > announcements that come from it is a broken concept. I have given you several > examples where your proposal does not work. > > thanks, > Peter > > > > > For Anycast prefixes situation that you described(although we seldom > > plan our network in such way), the PCE controller will not deduce the > > wrong information from the reported information------Different router > > advertise the same prefix, why can’t they be connected in logically? > > > > On summary, the ABR can know and report the originator of the > > connected interface’s prefixes, and also the connected information for > > the unnumbered/virtual link from the traditional router LSA/network > > LSA message, thus can transfer them to the router that run BGP-LS, > > then to the PCE controller to retrieval the topology. > > > > _To Rob: _ > > > > BGP-LS is one prominent method to get the underlay network topology > > and has more flexibility to control the topology export as described > > in RFC > > 7752 <https://tools.ietf.org/html/rfc7752#section-1>. > > > > Solution 1) that you proposed is possible, but we will not run two > > different methods to get the topology. > > > > Solution 2) is also one possible deployment, but it eliminates the > > advantage of the BGP-LS, in which it needs several interaction points > > with the underlay network. and such deployment is not belong to > > redundancy category as information got from different areaes are > different. > > > > Solution 3)--Streaming telemetry technology should be used mainly for > > the monitor of network devices, it requires the PCE controller to > > contact with every router in the network, is also not the optimal > > solution when compared with BGP-LS. > > > > We can update the current draft to include all possible scenarios that > > we are not aiming at beginning for integrity consideration. The > > proposed extension does not add to complexity of IGP. What we > > discussed here is the complexity of IGP protocol itself. > > > > Best Regards. > > > > Aijun Wang > > > > Network R&D and Operation Support Department > > > > China Telecom Corporation Limited Beijing Research Institute,Beijing, > China. > > > > *发件人:*Rob Shakir [mailto:[email protected]] > > *发送时间:*2018年7月24日7:04 > > *收件人:*Peter Psenak > > *抄送:*Dongjie (Jimmy); [email protected]; Ketan Talaulikar (ketant); > > Aijun Wang; [email protected]; Acee Lindem (acee) > > *主题:*Re: [Lsr] 答复: 答复: Regarding OSPF extension for inter-area > > topology retrieval > > > > +1 to Peter. We should not define fragile solutions within the IETF. > > > > There are also a multitude of other solutions here already: > > > > 1) IGP adjacency with one router in each area (at a minimum - probably > > two for a robust system) over a tunnel. Deployed in many networks for > > years. > > 2) BGP-LS to one router (ditto robustness comment) in each area. > > 3) streaming telemetry of the LSDB contents via gNMI. > > > > All these solutions exist in shipping implementations - please let’s > > not add to the system complexity of the IGP here. > > > > r. > > > > On Mon, Jul 23, 2018 at 12:30 Peter Psenak > > <[email protected] > > <mailto:[email protected]>> > > wrote: > > > > Hi Aijun, > > > > On 23/07/18 13:07 , Aijun Wang wrote: > > > Hi, Peter: > > > > > > For routers that connected by LAN, the router will establish > adjacent > > > neighbor with DR, but not only DR advertises the connected > prefixes. > > > > only the Network LSA includes the network mask, other routers > would > > include the interface address only. > > > > > > > DR and > > > DRother will all advertise type 1 and type 2 LSA with each other, > then the > > > process and proposal described in this draft will still work. > > > We seldom use the ip unnumbered features in our network, can we > ignore it > > > then? Or other persons has some idea on such situation? > > > > the fact that you do not use unnumbered is not really relevant. IETF > > defines solutions that MUST work for all possible scenarios, not > only > > for a specific one. > > > > > Anycast prefixes are often /32 long, this can be easily filtered > by > SDN > > > controller because the link prefixes between two routers will be > no > larger > > > than /32 for IPv4 network. > > > > protocol allows to advertise the same prefix with an arbitrary mask > from > > multiple routers without these routers being directly connected. > Your > > proposal is based on the assumptions that are incorrect. > > > > thanks, > > Peter > > > > > > > > Best Regards. > > > > > > Aijun Wang > > > Network R&D and Operation Support Department > > > China Telecom Corporation Limited Beijing Research > Institute,Beijing, China. > > > > > > -----邮件原件----- > > >发件人: Peter Psenak [mailto:ppsenak > > <mailto:ppsenak>[email protected] > > <mailto:[email protected]>] > > >发送时间: 2018年7月23日18:20 > > >收件人: Aijun Wang; 'Peter Psenak'; [email protected] > > <mailto:[email protected]> > > >抄送: [email protected] <mailto:[email protected]>; 'Ketan Talaulikar > > (ketant)'; 'Acee Lindem (acee)'; > > > 'Dongjie (Jimmy)' > > >主题: Re: [Lsr] 答复: Regarding OSPF extension for inter-area > topology > > > retrieval > > > > > > Hi Aijun, > > > > > > On 23/07/18 11:16 , Aijun Wang wrote: > > >> Hi, Peter: > > >> > > >> Actually, I consider mainly the point-to-point connection and the > > >> numbered interface, which are normal in our network. > > >> For the two situations that you mentioned, I will investigation > the > > >> possible solutions and feedback you later. > > >> > > >> For the point-to-point and numbered interface, do you have other > > >> questions then? > > > > > > the fact that two routers announce the same subnet, does not > mean they are > > > connected together by p2p link. Anycast prefix is an example. > > > > > > The idea you are proposing simply does not work. > > > > > > thanks, > > > Peter > > > > > > > > >> > > >> Best Regards. > > >> > > >> Aijun Wang > > >> Network R&D and Operation Support Department China Telecom > Corporation > > >> Limited Beijing Research Institute,Beijing, China. > > >> > > >> -----邮件原件----- > > >>发件人: Peter Psenak [mailto:ppsenak > > <mailto:ppsenak>[email protected] > > <mailto:[email protected]>] > > >>发送时间: 2018年7月23日16:15 > > >>收件人: Aijun Wang; [email protected] > <mailto:[email protected]> > > >>抄送: [email protected] <mailto:[email protected]>; 'Ketan Talaulikar > > (ketant)'; 'Acee Lindem (acee)'; > > >> 'Dongjie (Jimmy)' > > >>主题: Re: [Lsr] Regarding OSPF extension for inter-area topology > > >> retrieval > > >> > > >> Hi Aijun, > > >> > > >> you are trying to reconstruct the topology of the remote area > based on > > >> the fact that two routers are connected to the same subnet. It > does > > >> not work > > >> because: > > >> > > >> 1. connections between routers can be unnumbered 2. routers > can be > > >> connected via LAN, in which case only DR announces the prefix. > > >> > > >> In summary, what you propose does not work. > > >> > > >> thanks, > > >> Peter > > >> > > >> > > >> > > >> On 23/07/18 09:49 , Aijun Wang wrote: > > >>> (Sorry for my previous mail sent wrongly to the IDR mail list, > please > > >>> reply on this thread within the LSR wg) > > >>> > > >>> Hi, Peter: > > >>> > > >>> I am Aijun Wang from China Telecom, the author of draft about > “OSPF > > >>> extension for inter-area topology retrieval” > > >>> > <https://datatracker.ietf.org/doc/draft-wang-lsr-ospf-inter-area-topo > > >>> l ogy-ext/>, which is presented by Mr.Jie Dong during the > IETF102 > > >>> meeting. > > >>> > > >>> Thanks for your comments on the presentation material > > >>> > > >> > <https://datatracker.ietf.org/meeting/102/materials/slides-102-lsr-osp > > >> f-inte > > >> r-area-topology-retrieval-00>. > > >>> > > >>> Below are my explanation that regarding to the question about > “how it > > >>> retrievals the inter-area topology based on the extension > information”: > > >>> > > >>> Let’s see the graph that illustrates in Fig.1 at section 3 > > >>> > <https://tools.ietf.org/html/draft-wang-lsr-ospf-inter-area-topology- > > >>> e xt-00#section-3> of the draft(I copy it also below for your > > >>> conveniences ): > > >>> > > >>> Assuming we want to rebuild the connection between router S1 > and > > >>> router > > >>> S2 that locates in area 1: > > >>> > > >>> 1)Normally, router S1 will advertise prefix N1 within its > router LSA > > >>> > > >>> 2)When this router LSA reaches the ABR router R1, it will > convert > it > > >>> into summary LSA, add the “Source Router Information”, which > is > > >>> router id of S1 in this example, as proposed in this draft. > > >>> > > >>> 3)R1 then floods this extension summary LSA to R0, which is > running > > >>> BGP-LS protocol with IP SDN Controller. The controller then > knows the > > >>> prefixes of N1 is from S1. > > >>> > > >>> 4)Router S2 will do the similar process, and the controller > will also > > >>> knows the prefixes N1 is also from S2 > > >>> > > >>> 5)Then it can reconstruct the connection between S1 and S2, > which > > >>> prefix is N1. The topology within Area 1 can then be recovered > > >> accordingly. > > >>> > > >>> Does the above explanation can answer your question. if so, I > can add > > >>> it into the context of this draft in updated version. > > >>> > > >>> Best Regards. > > >>> > > >>> Aijun Wang > > >>> > > >>> Network R&D and Operation Support Department > > >>> > > >>> China Telecom Corporation Limited Beijing Research > Institute,Beijing, > > >> China. > > >>> > > >> > > >> _______________________________________________ > > >> Lsr mailing list > > >>[email protected] <mailto:[email protected]> > > >>https://www.ietf.org/mailman/listinfo/lsr > > >> > > >> _______________________________________________ > > >> Lsr mailing list > > >>[email protected] <mailto:[email protected]> > > >>https://www.ietf.org/mailman/listinfo/lsr > > >> > > > > > > _______________________________________________ > > > Lsr mailing list > > >[email protected] <mailto:[email protected]> > > >https://www.ietf.org/mailman/listinfo/lsr > > > > > > . > > > > > > > _______________________________________________ > > Lsr mailing list > > [email protected] <mailto:[email protected]> > > https://www.ietf.org/mailman/listinfo/lsr > > > > _______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
