Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
Peter Psenak <ppsenak@cisco.com> Sat, 03 January 2015 10:20 UTC
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Date: Sat, 03 Jan 2015 11:20:52 +0100
From: Peter Psenak <ppsenak@cisco.com>
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To: "Les Ginsberg (ginsberg)" <ginsberg@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>
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Subject: Re: [OSPF] [Isis-wg] Mail regarding draft-ietf-ospf-segment-routing-extensions
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Hi Les, On 1/2/15 17:35 , Les Ginsberg (ginsberg) wrote: > 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 understanding was different. I thought Shraddha simply wanted to avoid calculating a backup for the prefix. thanks, Peter > 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)