Re: [Lsr] Rtgdir last call review of draft-ietf-ospf-mpls-elc-13
Peter Psenak <ppsenak@cisco.com> Wed, 06 May 2020 16:00 UTC
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To: Dhruv Dhody <dhruv.ietf@gmail.com>
Cc: rtg-dir@ietf.org, draft-ietf-ospf-mpls-elc.all@ietf.org, lsr@ietf.org, last-call@ietf.org
References: <158867189453.14412.14632358918213286203@ietfa.amsl.com> <8dd49248-84bd-a546-8fee-767ab75a182a@cisco.com> <CAB75xn65wcH23q1XO7EtONc7C38dyu43pMiWb0KoZspo7jdKmg@mail.gmail.com>
From: Peter Psenak <ppsenak@cisco.com>
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Date: Wed, 06 May 2020 17:59:55 +0200
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Subject: Re: [Lsr] Rtgdir last call review of draft-ietf-ospf-mpls-elc-13
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Hi Dhruv, please see inline: On 06/05/2020 17:40, Dhruv Dhody wrote: > Hi Peter, > > Thanks for your reply, snipping to points that need further discussion... > >> What about: >> >> Segment Routing with the MPLS Data Plane relies on Interior Gateway >> Protocols (IGP) such as OSPFv2 [RFC8665] and OSPFv3 [RFC8666] to signal >> labels. >> > > Much better. > > >>> (3) Section 4 >>> >>> The absence of ERLD-MSD advertisements indicates only that the >>> advertising node does not support advertisement of this capability. >>> >>> Do you mean to differentiate between support for the capability itself v/s >>> support for 'advertisement' only. But RFC 8662 says that ERLD value is >>> advertised only when following conditions are met: >> >> What is meant is that even though all the below conditions are set, if >> the node does not support the advertisement, one can not conclude what >> its ERLD is. >> >> If the node supports the advertisement of the ERLD, but the below >> conditions are not met, the node should not advertise the ELC capability >> in a first place. >> > > There are two things here - (a) the actual load balancing capability > of a node (b) the capability to advertise the ELC/ERLD. Usually > capability and the advertisement of the capability go together. In > this case we want to be explicit that the absence of ERLD-MSD > indicates just (b) and not (a). > > You do use the word "only", so may its all fine! I will leave it to > you/shepherd. yes, the absence of ERLD-MSD advertisements only indicates that a node does not support advertisement of (b). It can not be interpreted that (b) is not supported. Old nodes that do not advertise ERLD-MSD can not be assumed not to support non-zero ERLD. The "only" is there to express the above. > >>> >>> * MUST be entropy label capable and, as a consequence, MUST apply >>> the data-plane procedures defined in [RFC6790]. >>> >>> * MUST be able to read an ELI/EL, which is located within its ERLD >>> value. >>> >>> * MUST take into account an EL within the first ERLD labels in its >>> load-balancing function. >>> >>> Thus, I am not sure about this sentence. Maybe you mean to say that the >>> absence only indicates that the ERLD-MSD value of the node is unknown (and >>> it might still be capable of handling ELI/EL)? >>> >>> (4) Section 4 >>> >>> What would be the behavior if an OSPF router receives a ERLD of the node >>> but no ELC set for the corresponding prefix? That would be an error as per >>> RFC 8662, we should specify how one handles it within OSPF. If it is to >>> just ignore the ERLD, we should explicitly say that. >> >> the behavior is specified in the RFC 8662. OSPF is just a messenger, >> not the consumer of this information. >> > > Is there some text in RFC 8662 the clarify what one does on the > receiving side? I found only the sending conditions in section 4. How > does a receiving node behaves when he receives conflicting > information, which one does he trust (no ELC present or ERLD=10). We > could have interop issues here if you leave it open. well, if the node does not support ELC, then ERLD value is irrelevant. It's like having a speed limit for a road with no entry. But that is something that does not belong to protocol drafts. thanks, Peter > > Thanks! > Dhruv > > PS. Since the comments are the same for the IS-IS I-D, no need duplicate them. > >
- [Lsr] Rtgdir last call review of draft-ietf-ospf-… Dhruv Dhody via Datatracker
- Re: [Lsr] Rtgdir last call review of draft-ietf-o… Peter Psenak
- Re: [Lsr] Rtgdir last call review of draft-ietf-o… Dhruv Dhody
- Re: [Lsr] Rtgdir last call review of draft-ietf-o… Peter Psenak
- Re: [Lsr] Rtgdir last call review of draft-ietf-o… Acee Lindem (acee)