Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
Rob Shakir <rjs@rob.sh> Mon, 29 December 2014 09:08 UTC
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From: Rob Shakir <rjs@rob.sh>
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To: Peter Psenak <ppsenak@cisco.com>, Shraddha Hegde <shraddha@juniper.net>
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Subject: Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
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Peter, Shraddha, Primarily — I don’t think that use of the ‘B’ flag in the Adj-SID implies that there MUST be a backup route installed, it merely indicates that the Adj-SID MAY be subject to re-routing (and hence strict placement on an adjacency may not be honoured during link failures). For me, I’m unclear on what the practical use of not requesting backup for a {Node,Prefix}-SID could be — its very nature (“the shortest path to X” where X is a node/prefix) means that it is not well defined in terms of a route through the network, and hence is not well defined in terms of performance. This (to me) says that we cannot really rely on such a SID for performance-sensitive traffic, and hence must always be able to tolerate events such as FRR paths during protection. The fact that AdjSID maps deterministically to a particular link, about which the calculating entity (PCE/iLER) can know details of, means that performance can be inferred - and hence strict affinity to that path (and/or failure when it is not available) is of utility. Kind regards, r. > On 29 Dec 2014, at 08:56, Peter Psenak <ppsenak@cisco.com> wrote: > > Shraddha, > > I do not see how an originator of the node-sid can mandate a protection for the prefix on other routers. What if there is no backup available on a certain node along the path? > > The parallel with the B-flag in adj-sids is not right - in case of adj-sid the originator has the knowledge about the local adjacency protection and as such can signal it it it's LSA. > > thanks, > Peter > > > On 12/29/14 09:47 , Shraddha Hegde wrote: >> Peter, >> >> >> Pls see inline. >> >> Rgds >> Shraddha >> >> -----Original Message----- >> From: Peter Psenak [mailto:ppsenak@cisco.com] >> Sent: Monday, December 29, 2014 2:02 PM >> To: Shraddha Hegde; draft-ietf-ospf-segment-routing-extensions@tools.ietf.org; draft-ietf-isis-segment-routing-extensions@tools.ietf.org >> Cc: ospf@ietf.org; isis-wg@ietf.org >> Subject: Re: [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions >> >> Shraddha, >> >> I do not see how an originator can set any flag regarding the protection of the locally attached prefix. >> <Shraddha> The originator advertises 2 node-sids. One with p flag set and the other without the p-flag set. >> >> It's all the routers on the path towards such prefix that need to deal with the protection. >> <Shraddha> The receiving nodes will download protected path for the node-sid with p-flag set and download >> Unprotected path for the node-sid with p-flag unset. >> >> Signaling anything from the originator seems useless. >> <Shraddha> For node-sids it's the others who need to build the forwarding plane but it's only the originator who can signal which of >> Sid need to be built with protection and which not. Other routers on the path cannot signal this information. > > > >> >> With this you have two paths for the node. One is protected and the other is unprotected. This meets the requirement of having an un-protected path. >> >> It's very much in parallel to B-flag in adj-sids. It is similar to advertising multiple adj-sids one with B-flag on and other with b-flag off , to get protected and unprotected >> Adj-sids. >> >> thanks, >> Peter >> >> On 12/29/14 09:26 , Shraddha Hegde wrote: >>> Yes.You are right. >>> >>> Lets say a prefix sid has a flag "p flag". If this is on it means build a path and provide protection. >>> If this is off it means build a path with no protection. >>> The receivers of the prefix-sid will build forwarding plane based on this flag. >>> >>> The applications building the paths will either use prefix-sids with p flag on or off based on the need of the service. >>> Rgds >>> Shraddha >>> >>> >>> -----Original Message----- >>> From: Peter Psenak [mailto:ppsenak@cisco.com] >>> Sent: Monday, December 29, 2014 1:49 PM >>> To: Shraddha Hegde; >>> draft-ietf-ospf-segment-routing-extensions@tools.ietf.org; >>> draft-ietf-isis-segment-routing-extensions@tools.ietf.org >>> Cc: ospf@ietf.org; isis-wg@ietf.org >>> Subject: Re: [Isis-wg] Mail regarding >>> draft-ietf-ospf-segment-routing-extensions >>> >>> Shraddha, >>> >>> the problem is that the node that is advertising the node-sid can not advertise any data regarding the protection of such prefix, because the prefix is locally attached. >>> >>> thanks, >>> Peter >>> >>> On 12/29/14 09:15 , Shraddha Hegde wrote: >>>> Peter, >>>> >>>> If there is a service which has to use un-protected path and while >>>> building such a path if the node-sids Need to be used (one reason >>>> could be label stack compression) , then there has to be unprotected node-sid that this service can make use of. >>>> >>>> Prefix -sids could also be used to represent different service >>>> endpoints which makes it even more relevant to have A means of representing unprotected paths. >>>> >>>> Would be good to hear from others on this, especially operators. >>>> >>>> Rgds >>>> Shraddha >>>> >>>> >>>> -----Original Message----- >>>> From: Peter Psenak [mailto:ppsenak@cisco.com] >>>> Sent: Monday, December 29, 2014 1:35 PM >>>> To: Shraddha Hegde; >>>> draft-ietf-ospf-segment-routing-extensions@tools.ietf.org; >>>> draft-ietf-isis-segment-routing-extensions@tools.ietf.org >>>> Cc: ospf@ietf.org; isis-wg@ietf.org >>>> Subject: Re: [Isis-wg] Mail regarding >>>> draft-ietf-ospf-segment-routing-extensions >>>> >>>> Shraddha, >>>> >>>> node-SID is advertised by the router for the prefix that is directly attached to it. Protection for such local prefix does not mean much. >>>> >>>> thanks, >>>> Peter >>>> >>>> On 12/24/14 11:57 , Shraddha Hegde wrote: >>>>> Authors, >>>>> We have a "backup flag" in adjacency sid to indicate whether the >>>>> label is protected or not. >>>>> Similarly. I think we need a flag in prefix-sid as well to indicate >>>>> whether the node-sid is to be protected or not. >>>>> Any thoughts on this? >>>>> Rgds >>>>> Shraddha >>>>> >>>>> >>>>> _______________________________________________ >>>>> Isis-wg mailing list >>>>> Isis-wg@ietf.org >>>>> https://www.ietf.org/mailman/listinfo/isis-wg >>>>> >>>> >>>> . >>>> >>> >>> . >>> >> >> . >> > > _______________________________________________ > Isis-wg mailing list > Isis-wg@ietf.org > https://www.ietf.org/mailman/listinfo/isis-wg
- [OSPF] Mail regarding draft-ietf-ospf-segment-rou… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Rob Shakir
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Rob Shakir
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Rob Shakir
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Peter Psenak
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Pushpasis Sarkar
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Jeff Tantsura
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Pushpasis Sarkar
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Pushpasis Sarkar
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Pushpasis Sarkar
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Mitchell Erblich
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Shraddha Hegde
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Les Ginsberg (ginsberg)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Rob Shakir
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… stephane.litkowski
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… stephane.litkowski
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… stephane.litkowski
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… bruno.decraene
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… stephane.litkowski
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… bruno.decraene
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Henderickx, Wim (Wim)
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… stephane.litkowski
- Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-os… Henderickx, Wim (Wim)