Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Fri, 02 January 2015 16:36 UTC
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From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: "Peter Psenak (ppsenak)" <ppsenak@cisco.com>, Shraddha Hegde <shraddha@juniper.net>, "draft-ietf-ospf-segment-routing-extensions@tools.ietf.org" <draft-ietf-ospf-segment-routing-extensions@tools.ietf.org>, "draft-ietf-isis-segment-routing-extensions@tools.ietf.org" <draft-ietf-isis-segment-routing-extensions@tools.ietf.org>
Thread-Topic: [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
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Date: Fri, 02 Jan 2015 16:35:54 +0000
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Subject: Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
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Peter - The requirement Shraddha specified was to not allow a particular class of service ("heavy bandwidth services" was the example provided) to use certain links in the topology. My point is that advertising a flag for a given prefix which says "do not calculate a repair path for this prefix" does not help achieve this. Once the network reconverges following the failure of one of the links on which "heavy bandwidth services" is allowed/preferred it is quite likely that the new best path will be over a link on which "heavy bandwidth services" is NOT allowed/preferred. This will happen whether you have the new flag or not - so the flag will have no lasting effect. It would only affect traffic flow during the brief period during which the network is reconverging. I think you and I are actually in agreement - I am simply sending a stronger negative message - not only do I think the flag is not useful - I think it does not achieve the goal Shraddha has in mind. Les -----Original Message----- From: Peter Psenak (ppsenak) Sent: Friday, January 02, 2015 12:18 AM To: Les Ginsberg (ginsberg); 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 Hi Les, I believe the idea is not to exclude any particular link, it's actually much simpler - do not calculate backup for the prefix if the flag is set. I'm still not quite sure how useful above is, but technically it is possible. thanks, Peter On 12/30/14 17:22 , Les Ginsberg (ginsberg) wrote: > Shraddha - > > When performing a best path calculation whether a given link is in the set of best paths (to be protectedED) or not (could be used as a protectING path) is a function of the topology - not the link. If there is a topology change it is quite likely that a given link will change from being a protectED link to being a protectING link (or vice versa). So what you propose regarding node-SIDs would not work. > > In the use case you mention below if you don't want a certain class of traffic to flow on a given link it requires a link attribute which is persistent across topology changes. There are ways to do that - using Adj-SIDs is one of them. But using node-SIDs in the way you propose is NOT. > > Les > > -----Original Message----- > From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of Shraddha Hegde > Sent: Monday, December 29, 2014 10:12 PM > To: Peter Psenak (ppsenak); > 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: [OSPF] [Isis-wg] Mail regarding > draft-ietf-ospf-segment-routing-extensions > > Peter, > >> The requirement here is to get an un-protected path for services which do not want to divert the traffic on protected path in any case. > >> can you give an example of such a service and a reasoning why such service would want to avoid local protection along the path? > > Heavy bandwidth services are potential candidates. The network is well planned and well provisioned for primary path but same is not true for backup paths. > Diverting heavy bandwidth services along protection path can disrupt the other services on that path, they are better-off un-protected so that an event in the network Would result in disconnection and a retry for such services. > > Rgds > Shraddha > > -----Original Message----- > From: Peter Psenak [mailto:ppsenak@cisco.com] > Sent: Monday, December 29, 2014 4:35 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, > > On 12/29/14 10:06 , Shraddha Hegde wrote: >> Peter, >> >> The requirement here is to get an un-protected path for services which do not want to divert the traffic on protected path in any case. > > can you give an example of such a service and a reasoning why such service would want to avoid local protection along the path? > > thanks, > Peter > >> So when the originator of node-sid signals un-protected path requirement, there is always an unprotected path. >> >> Regarding the protected path, it is the default behavior as it exists today. You get protection if it's available otherwise you don't get protection. >> >> In fact, you can have the new flag to say "NP flag" meaning non-protected flag which can be set for the unprotected path. >> By default it remains off and gives the behavior as it exists today. >> >> >> Rgds >> Shraddha >> >> -----Original Message----- >> From: Peter Psenak [mailto:ppsenak@cisco.com] >> Sent: Monday, December 29, 2014 2:26 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 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 >>>>>> >>>>> >>>>> . >>>>> >>>> >>>> . >>>> >>> >>> . >>> >> >> . >> > > _______________________________________________ > OSPF mailing list > OSPF@ietf.org > https://www.ietf.org/mailman/listinfo/ospf > . >
- [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)