Re: [OSPF] OSPFv2 SR draft
Peter Psenak <ppsenak@cisco.com> Thu, 25 August 2016 08:45 UTC
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Date: Thu, 25 Aug 2016 10:45:09 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: Chris Bowers <cbowers@juniper.net>, OSPF List <ospf@ietf.org>
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Subject: Re: [OSPF] OSPFv2 SR draft
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Hi Chris, On 24/08/16 20:31 , Chris Bowers wrote: > Peter, > > The text that you propose corresponds to part of the text that I proposed, and it seems good to me. > > However, the last sentence of the text that I proposed in not addressed. > ------ > If router B does not advertise the > SR-Algorithm TLV for algorithm X, then other routers should not > forward traffic destined for a prefix-SID for algorithm X advertised by > some router D using a path that would require router B to forward traffic using > algorithm X. > ------ > Is this an oversight? not that I disagree with the statement that you want to add. The question is whether that belongs to the IGP SR draft, or whether that should be specified in a different draft. There is already some text regarding the forwarding for a SR algorithm in draft-ietf-spring-segment-routing section 3.2.1., which may not be aligned with what you have in mind: "The ingress node of an SR domain validates that the path to a prefix, advertised with a given algorithm, includes nodes all supporting the advertised algorithm. In other words, when computing paths for a given algorithm, the transit nodes MUST compute the algorithm X on the IGP topology, regardless of the support of the algorithm X by the nodes in that topology. As a consequence, if a node on the path does not support algorithm X, the IGP-Prefix segment will be interrupted and will drop packet on that node. It's the responsibility of the ingress node using a segment to check that all downstream nodes support the algorithm of the segment." Maybe we should add/modify the text in draft-ietf-spring-segment-routing section 3.2.1, rather then adding anything to the OSPF/ISIS SR drafts. thanks, Peter > > Thanks, > Chris > > > -----Original Message----- > From: Peter Psenak [mailto:ppsenak@cisco.com] > Sent: Monday, August 22, 2016 2:32 AM > To: Chris Bowers <cbowers@juniper.net>; OSPF List <ospf@ietf.org> > Subject: Re: [OSPF] OSPFv2 SR draft > > Chris, > > what about this to be added in the Section 3.1: > > > "A router receiving a Prefix-SID (defined in section 5) from a remote node and with an SR algorithm value that such remote node has not advertised in the SR-Algorithm sub-TLV MUST ignore the Prefix-SID sub-TLV." > > thanks, > Peter > > > On 19/08/16 23:33 , Chris Bowers wrote: >> Peter, >> >> Please share the updated text that you plan to use with the WG, since this is a reasonably significant clarification. >> >> Thanks, >> Chris >> >> -----Original Message----- >> From: Peter Psenak [mailto:ppsenak@cisco.com] >> Sent: Tuesday, August 16, 2016 10:02 AM >> To: Chris Bowers <cbowers@juniper.net>; OSPF List <ospf@ietf.org> >> Subject: Re: [OSPF] OSPFv2 SR draft >> >> Hi Chris, >> >> I'll update the draft along those lines. >> >> thanks, >> Peter >> >> >> On 16/08/16 16:02 , Chris Bowers wrote: >>> Peter, >>> >>> I suggest changing the paragraph to read as below to make this clearer. >>> >>> ===== >>> The SR-Algorithm Sub-TLV is optional. It MAY only be advertised once >>> in the Router Information Opaque LSA. If the SID/Label Range TLV, as >>> defined in Section 3.2, is advertised, then the SR-Algorithm TLV MUST >>> also be advertised. If a router C advertises a Prefix-SID sub-TLV for algorithm X >>> but does not advertise the SR-Algorithm Sub-TLV with algorithm X, then >>> a router receiving that advertisement MUST ignore the Prefix-SID >>> advertisement from router C. If router B does not advertise the >>> SR-Algorithm TLV for algorithm X, then other routers should not >>> forward traffic destined for a prefix-SID for algorithm X advertised by >>> some router D using a path that would require router B to forward traffic using >>> algorithm X. >>> ===== >>> >>> Thanks, >>> Chris >>> >>> >>> >>> -----Original Message----- >>> From: Peter Psenak [mailto:ppsenak@cisco.com] >>> Sent: Monday, August 15, 2016 6:40 AM >>> To: Chris Bowers <cbowers@juniper.net>; OSPF List <ospf@ietf.org> >>> Subject: Re: [OSPF] OSPFv2 SR draft >>> >>> Hi Chris, >>> >>> sorry for the delay, I was on PTO during last two weeks. >>> Please see inline: >>> >>> On 03/08/16 16:45 , Chris Bowers wrote: >>>> Peter, >>>> >>>> Taking a looking at the whole paragraph into this sentence was >>>> added, I am not sure how to interpret it. >>>> >>>> The SR-Algorithm Sub-TLV is optional. It MAY only be advertised once >>>> in the Router Information Opaque LSA. If the SID/Label Range TLV, as >>>> defined in Section 3.2, is advertised, then the SR-Algorithm TLV MUST >>>> also be advertised. If the SR-Algorithm TLV is not advertised by the >>>> node, such node is considered as not being segment routing capable. >>>> >>>> Is this sentence intended to imply that if a router does not >>>> advertise the SR-Algorithm TLV including algorithm X, then any >>>> prefix-SIDs for algorithm X advertised by that router will be ignored by other routers? >>> >>> in OSPF we do not have the SR capability TLV. We use SR-Algorithm TLV >>> for that purpose. So if a router does not advertise the SR-Algorithm >>> TLV for algorithm X, other routers should not send any SR traffic >>> using SIDs that were advertised for algorithm X. >>> >>> If the router does not advertise any SR Algorithm TLV, then the node >>> is not SR capable and no SR traffic should be forwarded to such a node. >>> >>> thanks, >>> Peter >>> >>> >>>> >>>> If this is the intention, then it would be better to state is more explicitly. >>>> >>>> If not, then the intended meaning should be clarified. >>>> >>>> Thanks, >>>> Chris >>>> >>>> >>>> -----Original Message----- >>>> From: OSPF [mailto:ospf-bounces@ietf.org] On Behalf Of Peter Psenak >>>> Sent: Friday, July 22, 2016 3:30 AM >>>> To: OSPF List <ospf@ietf.org> >>>> Subject: [OSPF] OSPFv2 SR draft >>>> >>>> Hi All, >>>> >>>> following text has been added in the latest revision of the OSPFv2 >>>> SR draft, section 3.1. >>>> >>>> "If the SR-Algorithm TLV is not advertised by node, such node is >>>> considered as not being segment routing capable." >>>> >>>> Please let us know if there are any concerns regarding this addition. >>>> >>>> thanks, >>>> Peter >>>> >>>> _______________________________________________ >>>> OSPF mailing list >>>> OSPF@ietf.org >>>> https://www.ietf.org/mailman/listinfo/ospf >>>> . >>>> >>> >>> . >>> >> >> . >> > > . >
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- Re: [OSPF] OSPFv2 SR draft Peter Psenak
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- Re: [OSPF] OSPFv2 SR draft Peter Psenak
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- [OSPF] OSPFv2 SR draft Peter Psenak
- Re: [OSPF] OSPFv2 SR draft Peter Psenak
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- Re: [OSPF] OSPFv2 SR draft Peter Psenak
- Re: [OSPF] OSPFv2 SR draft Les Ginsberg (ginsberg)
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- Re: [OSPF] OSPFv2 SR draft Acee Lindem (acee)
- Re: [OSPF] OSPFv2 SR draft Chris Bowers
- Re: [OSPF] OSPFv2 SR draft Acee Lindem
- Re: [OSPF] OSPFv2 SR draft Chris Bowers