Re: [Idr] [spring] Comments: Route Origin Community in SR Policy(draft-ietf-spring-segment-routing-policy)
Gyan Mishra <hayabusagsm@gmail.com> Mon, 01 June 2020 13:33 UTC
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From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Mon, 01 Jun 2020 09:32:44 -0400
Message-ID: <CABNhwV0CXK2dTqG9WSZ05yan4vbbPwLbNpbdscBky09MU8cbNw@mail.gmail.com>
To: "Ketan Talaulikar (ketant)" <ketant@cisco.com>
Cc: "Chengli (Cheng Li)" <c.l@huawei.com>, Fangsheng <fangsheng@huawei.com>, Robert Raszuk <robert@raszuk.net>, SPRING WG <spring@ietf.org>, Yangang <yangang@huawei.com>, "draft-ietf-spring-segment-routing-policy@ietf.org" <draft-ietf-spring-segment-routing-policy@ietf.org>, idr wg <idr@ietf.org>, stefano previdi <stefano@previdi.net>
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Subject: Re: [Idr] [spring] Comments: Route Origin Community in SR Policy(draft-ietf-spring-segment-routing-policy)
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On Thu, May 28, 2020 at 6:32 AM Ketan Talaulikar (ketant) <ketant@cisco.com> wrote: > Hi Gyan, > > > > Could I refer you to the examples in > https://tools.ietf.org/html/draft-filsfils-spring-sr-policy-considerations-05#section-4 > as that might clarify the various options for signalling redundant > information (both as different BGP NLRI, via redundant BGP paths, or via > multiple protocol sources). > > Gyan> Thanks Ketan. So this scenario would be example 2 recommended with > “auto RD” type 1 unique by loopback so both paths are installed in BGP sent > to SR-TE for instantiation which now picks greater candidate path number as > Active path. > > Thanks, > > Ketan > > > > *From:* Gyan Mishra <hayabusagsm@gmail.com> > > *Sent:* 22 May 2020 00:48 > *To:* Robert Raszuk <robert@raszuk.net> > *Cc:* Chengli (Cheng Li) <c.l@huawei.com>; Fangsheng <fangsheng@huawei.com>; > Ketan Talaulikar (ketant) <ketant@cisco.com>; SPRING WG <spring@ietf.org>; > Yangang <yangang@huawei.com>; > draft-ietf-spring-segment-routing-policy@ietf.org; idr wg <idr@ietf.org>; > stefano previdi <stefano@previdi.net> > *Subject:* Re: [spring] [Idr] Comments: Route Origin Community in SR > Policy(draft-ietf-spring-segment-routing-policy) > > > > > > On Wed, May 20, 2020 at 8:59 AM Robert Raszuk <robert@raszuk.net> wrote: > > Hi, > > > > > the node-address is generated by CSG1 > > > > I don't think CSG1 needs to "generate" anything. Peers which send you > particular policy are well known at CSG1. > > > > > The process described above will result in a waste of redundant > candidate paths on CSG1, > > > > Well what you call "waste" I call redundancy. Sure keeping extra paths > requires some cost, but building redundancy in control plane pays off. > > > > Gyan> I agree with Robert that the additional candidate path sent by > the RR could be used for redundancy. However, I think the context of SR > TE is that each candidate path is a single path option not multiple as the > redundancy is provided by different candidate paths. That is the issue I > am guessing. > > > > > > Thx, > R. > > > > > > > > > > On Wed, May 20, 2020 at 2:32 PM Fangsheng <fangsheng@huawei.com> wrote: > > Hi Robert, > > Take the following picture as an example, I think you can understand our > problem more easily. > > The controller needs to notify the headend CSG1 through BGP SR Policy to > create a candidate path of SR Policy. This BGP SR Policy route will be > advertised to CSG1 through RR1 and RR2. > > According to the definition in draft, the key of a candidate path is > <Protocol-Origin, originator, discriminator>, where originator = <ASN, > node-address>, so a complete candidate path key is <Protocol-Origin, ASN, > node-address , discriminator>. > > However, in this specific example, the node-address is generated by CSG1, > and because CSG1 receives BGP SR Policy routes from RR1 and RR2, > respectively, CSG1 will get two different node-addresses. CSG1 thinks that > it is necessary to create two candidate paths, and the controller does not > know what the node-address CSG1 will eventually generate. Maybe: > > Candidate path 1’ key: <*BGP,RR1’s ASN, RR1’ BGP Router ID, > discriminator1*> > > Candidate path 2’ key: <*BGP,RR2’s ASN, RR2’ BGP Router ID, > discriminator2*> > > The process described above will result in a waste of redundant candidate > paths on CSG1, > > At the same time, when CSG1 needs to announce the SR Policy information to > the controller through BGP LS, it needs to carry the keys of the candidate > path in it, and the controller cannot recognize these keys. > > > > > > > > To solve these problems, We recommend carrying the Route Origin Community > (defined in RFC 4360) directly when the controller advertises BGP routes. > > In this way, the key of the CP is determined by the controller and will > not change during the advertisement of BGP routes. > > > > > > > > > > *发件人**:* Ketan Talaulikar (ketant) [mailto:ketant@cisco.com] > *发送时间**:* 2020年5月18日 20:00 > *收件人**:* Robert Raszuk <robert@raszuk.net> > *抄送**:* Chengli (Cheng Li) <c.l@huawei.com>; > draft-ietf-spring-segment-routing-policy@ietf.org; idr wg <idr@ietf.org>; > SPRING WG <spring@ietf.org>; Fangsheng <fangsheng@huawei.com>; stefano > previdi <stefano@previdi.net> > *主题**:* RE: [Idr] Comments: Route Origin Community in SR > Policy(draft-ietf-spring-segment-routing-policy) > > > > Hi Robert, > > > > You are right that the “Originator” is not used in BGP best path and is > just for a tie-breaking logic in SRTE between paths from different > protocols and controllers. I doubt if there is a functional issue here. > > > > I thought that Chengli was bringing in some new/different requirement for > the “Originator” field for some deployment design. I haven’t seen a > response/clarification from him as yet, and so perhaps I misunderstood him > in which case we are ok here. > > > > Thanks, > > Ketan > > > > *From:* Robert Raszuk <robert@raszuk.net> > *Sent:* 30 April 2020 14:46 > *To:* Ketan Talaulikar (ketant) <ketant@cisco.com> > *Cc:* Chengli (Cheng Li) <chengli13@huawei.com>; > draft-ietf-spring-segment-routing-policy@ietf.org; idr wg <idr@ietf.org>; > SPRING WG <spring@ietf.org>; Fangsheng <fangsheng@huawei.com>; stefano > previdi <stefano@previdi.net> > *Subject:* Re: [Idr] Comments: Route Origin Community in SR > Policy(draft-ietf-spring-segment-routing-policy) > > > > Hi Chengli and Ketan, > > > > Well I think (perhaps to your surprise) the current text is actually > correct. > > > > See the overall idea of section 2.4 is not to define the real source of > the candidate path. That is done in section 2.5 The idea here is to keep > multiple *paths or versions* of the candidate paths in the local system > uniquely. > > > > See if you continue reading section 2.6 demystifies the real objective: > > > > The tuple <Protocol-Origin, originator, discriminator> uniquely > > identifies a candidate path. > > > > So the real originator is encoded in discriminator and here it just means the peer candidate path was > > received from. And if you read on this entire exercise only servers best path selection as described in section 2.9. > > > > .... the following order until only one valid best path is selected: > > > > 1. Higher value of Protocol-Origin is selected. > > > > 2. If specified by configuration, prefer the existing installed > > path. > > > > 3. Lower value of originator is selected. > > > > 4. Finally, the higher value of discriminator is selected. > > > > + > > The originator allows an operator to have multiple redundant > > controllers and still maintain a deterministic behaviour over > > which of them are preferred even if they are providing the same > > candidate paths for the same SR policies to the headend. > > > > Thx, > R. > > > > On Thu, Apr 30, 2020 at 10:46 AM Ketan Talaulikar (ketant) <ketant= > 40cisco.com@dmarc.ietf.org> wrote: > > Hi Cheng, > > > > I assume you are recommending the use of Route Origin Extended Community ( > https://tools.ietf.org/html/rfc4360#section-5) for conveying the “ > Originator” when the SR Policy update is propagated over eBGP sessions > via other eBGP/iBGP sessions instead of direct peering with the headend. > > > > I believe it does address the scenario you describe given that it is > expected that SR Policy propagation via BGP is happening within a single > administrative domain even if it comprises of multiple ASes. > > > > Also copying the IDR WG for inputs since this would likely need to be > updated in draft-ietf-idr-segment-routing-te-policy. > > > > Thanks, > > Ketan > > > > *From:* spring <spring-bounces@ietf.org> *On Behalf Of *Chengli (Cheng Li) > *Sent:* 30 April 2020 07:34 > *To:* draft-ietf-spring-segment-routing-policy@ietf.org > *Cc:* SPRING WG <spring@ietf.org>; huruizhao <huruizhao@huawei.com>; > Fangsheng <fangsheng@huawei.com> > *Subject:* [spring] Comments: Route Origin Community in SR > Policy(draft-ietf-spring-segment-routing-policy) > > > > Hi authors, > > > > In section 2.4 of [draft-ietf-spring-segment-routing-policy-06], > introduced how the node-address of "Originator of CP(Candidate Path)" is > generated when the Protocol-Origin is BGP. It says: > > “Protocol-Origin is BGP SR Policy, it is provided by the BGP > component on the headend and is: > > o the BGP Router ID and ASN of the node/controller signalling the > candidate path when it has a BGP session to the headend, OR > > o the BGP Router ID of the eBGP peer signalling the candidate path > along with ASN of origin when the signalling is done via one or more > intermediate eBGP routers, OR > > o the BGP Originator ID [RFC4456] and the ASN of the > node/controller when the signalling is done via one or more > route-reflectors over iBGP session.” > > > > In the operator's network, in order to reduce the number of BGP sessions > in controller and achieve scalability, the controller only establishes eBGP > peer with the RR. And the RR establishes iBGP peers with the headends.. As > mentioned in the draft, the headend will use the RR's Router ID as the CP's > node-address (the signaling is done via route transmission from RR to the > headend instead of route reflection). The headend needs to carry the CP's > key when reporting the SR Policy status to the controller through BGP-LS. > And there is a problem that the controller may not recognize the key > because the node-address is generated by the RR node. > > > > For network robustness, two or more RRs are usually deployed. This will > introduce another problem.. When the same CP advertised by the controller > is delivered to the headend through different RRs, the headend cannot > distinguish whether it is the same CP because the node-address in the CPs' > key comes from different RRs. > > > > To solve these problems, We recommend carrying the Route Origin Community > (defined in RFC 4360) directly when the controller advertises BGP routes. > In this way, the key of the CP is determined by the controller and will > not change during the advertisement of BGP routes. > > > > Thanks, > > Cheng > > _______________________________________________ > Idr mailing list > Idr@ietf.org > https://www.ietf.org/mailman/listinfo/idr > > _______________________________________________ > spring mailing list > spring@ietf.org > https://www.ietf.org/mailman/listinfo/spring > > -- > > <http://www.verizon.com/> > > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > > *Gyan Mishra* > > *Network Solutions Architect * > > > > *M 301 502-1347 13101 Columbia Pike > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > *Silver Spring, MD > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > > > -- <http://www.verizon.com/> *Gyan Mishra* *Network Solutions A**rchitect * *M 301 502-134713101 Columbia Pike *Silver Spring, MD
- Re: [Idr] Comments: Route Origin Community in SR … Ketan Talaulikar (ketant)
- Re: [Idr] Comments: Route Origin Community in SR … Robert Raszuk
- Re: [Idr] Comments: Route Origin Community in SR … Ketan Talaulikar (ketant)
- [Idr] 答复: Comments: Route Origin Community in SR … Fangsheng
- Re: [Idr] Comments: Route Origin Community in SR … Robert Raszuk
- Re: [Idr] Comments: Route Origin Community in SR … Fangsheng
- Re: [Idr] Comments: Route Origin Community in SR … Ketan Talaulikar (ketant)
- Re: [Idr] Comments: Route Origin Community in SR … Fangsheng
- [Idr] 答复: [spring] Comments: Route Origin Communi… Aijun Wang
- Re: [Idr] Comments: Route Origin Community in SR … Ketan Talaulikar (ketant)
- Re: [Idr] [spring] Comments: Route Origin Communi… Ketan Talaulikar (ketant)
- [Idr] 答复: [spring] Comments: Route Origin Communi… Aijun Wang
- Re: [Idr] [spring] Comments: Route Origin Communi… Ketan Talaulikar (ketant)
- Re: [Idr] [spring] Comments: Route Origin Communi… Gyan Mishra
- Re: [Idr] [spring] Comments: Route Origin Communi… Ketan Talaulikar (ketant)
- Re: [Idr] Comments: Route Origin Community in SR … Ketan Talaulikar (ketant)
- Re: [Idr] [spring] Comments: Route Origin Communi… Gyan Mishra
- Re: [Idr] [spring] Comments: Route Origin Communi… Gyan Mishra
- Re: [Idr] [spring] Comments: Route Origin Communi… Ketan Talaulikar (ketant)
- Re: [Idr] [spring] Comments: Route Origin Communi… Ketan Talaulikar (ketant)
- Re: [Idr] [spring] Comments: Route Origin Communi… Gyan Mishra
- Re: [Idr] Comments: Route Origin Community in SR … Chengli (Cheng Li)