Re: [Lsr] 答复: 答复: Regarding OSPF extension for inter-area topology retrieval

[Tony Przygienda <[e-mail]>]

pretty obvious +1 here

--- tony

On Tue, Jul 24, 2018 at 3:41 AM Rob Shakir <[e-mail]> wrote:

> +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 <ppsenak=
> [e-mail]> 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=[e-mail]]
>> > 发送时间: 2018年7月23日 18:20
>> > 收件人: Aijun Wang; 'Peter Psenak'; [e-mail]
>> > 抄送: [e-mail]; '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=[e-mail]]
>> >> 发送时间: 2018年7月23日 16:15
>> >> 收件人: Aijun Wang; [e-mail]
>> >> 抄送: [e-mail]; '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.
>> >>>
>> >>
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