Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-ospf-ospfv3-segment-routing-extensions-20: (with DISCUSS and COMMENT)
Peter Psenak <ppsenak@cisco.com> Tue, 08 January 2019 16:09 UTC
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To: Benjamin Kaduk <kaduk@mit.edu>
References: <154398144445.4943.7198735398003216566.idtracker@ietfa.amsl.com> <5C079200.1030701@cisco.com> <20181217055358.GC94620@kduck.kaduk.org> <69190220-4994-f9c9-4adf-5016abf3a39b@cisco.com> <03e6354b-c606-fc4a-bbf2-3d59fa1cb774@cisco.com> <20181222042939.GW94620@kduck.kaduk.org> <8D31ADF0-FA83-4B23-805E-76145BF914C1@cisco.com> <f3dff5f1-434c-431d-15a3-5fa7462f5572@cisco.com> <20190108143354.GX28515@kduck.kaduk.org>
Cc: "Acee Lindem (acee)" <acee@cisco.com>, The IESG <iesg@ietf.org>, "draft-ietf-ospf-ospfv3-segment-routing-extensions@ietf.org" <draft-ietf-ospf-ospfv3-segment-routing-extensions@ietf.org>, "aretana.ietf@gmail.com" <aretana.ietf@gmail.com>, "lsr-chairs@ietf.org" <lsr-chairs@ietf.org>, "lsr@ietf.org" <lsr@ietf.org>
From: Peter Psenak <ppsenak@cisco.com>
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Date: Tue, 08 Jan 2019 17:09:01 +0100
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Subject: Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-ospf-ospfv3-segment-routing-extensions-20: (with DISCUSS and COMMENT)
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Hi Benjamin, Happy New Year! Please see inline: On 08/01/2019 15:33 , Benjamin Kaduk wrote: > Hi Peter, > > Happy new year, and my apologies to all for the heavy overlap between this > message and the reply to Acee sent just a few moments ago. > (inline) > > On Tue, Jan 08, 2019 at 09:13:52AM +0100, Peter Psenak wrote: >> Hi Benjamin, >> >> please see inline: >> >> >> On 22/12/2018 15:34 , Acee Lindem (acee) wrote: >>> Hi Ben, >>> >>> See inline. >>> >>> On 12/21/18, 11:29 PM, "Benjamin Kaduk" <kaduk@mit.edu> wrote: >>> >>> On Thu, Dec 20, 2018 at 01:07:59PM +0100, Peter Psenak wrote: >>> > Hi Benjamin, >>> > >>> > are you ok with my responses and proposed changed text for the range? >>> > >>> > thanks, >>> > Peter >>> > >>> > On 17/12/2018 12:32 , Peter Psenak wrote: >>> > > Hi Benjamin, >>> > > >>> > > please see inline (##PP): >>> > > >>> > > On 17/12/2018 06:53 , Benjamin Kaduk wrote: >>> > >> Sorry for the slow reply -- you caught me right as I was leaving for >>> > >> vacation. >>> > >> >>> > >> On Wed, Dec 05, 2018 at 09:53:20AM +0100, Peter Psenak wrote: >>> > >>> Hi Benjamin, >>> > >>> >>> > >>> please see inline: >>> > >>> >>> > >>> On 05/12/18 04:44 , Benjamin Kaduk wrote: >>> > >>>> ---------------------------------------------------------------------- >>> > >>>> DISCUSS: >>> > >>>> ---------------------------------------------------------------------- >>> > >>>> >>> > >>>> What is the extensibility model for the "AF" (address family) field >>> > >>>> in the >>> > >>>> OSPFv3 Extended Prefix Range TLV? That is, what do we need to say >>> > >>>> about >>> > >>>> current implementations' behavior to allow future changes? (I also a >>> > >>>> little bit wonder if we really need a full eight bits, but that's >>> > >>>> basically >>> > >>>> aesthetic.) >>> > >>> >>> > >>> I don't think OSPFv3 will ever support other then IPv6 or IPv4 AF. Also >>> > >>> the text says: >>> > >>> >>> > >>> "Prefix encoding for other address families is beyond the scope >>> > >>> of this specification." >>> > >> >>> > >> Perhaps it would be better encoded in a 1-bit field (rather than an 8-bit >>> > >> one), then? That would at least make the (lack of) semantics of the >>> > >> other >>> > >> 7 bits more clear, as the usual "MUST set to zero on transmit and >>> > >> ignore on >>> > >> receipt". >>> > > >>> > > ##PP >>> > > it's too late now to change the encoding. This draft has several years >>> > > of history and there are implementation shipping. Changing the encoding >>> > > would cause the backward compatibility issues. >>> >>> I didn't think I was suggesting changing the bits on the wire -- in an >>> 8-octet field, we're encoding the values 0 and 1 as: >>> >>> 00000000 >>> 00000001 >>> >>> I'm proposing to change the eight bits to be specified as "the first seven >>> bits are always set to 0 but should be ignored on receipt; the eighth bit >>> represents the 0 or 1 value". This makes it clear what needs to happen if >>> there's a need to use any of those seven bits (an Update to this document) >>> and also makes it more clear that there are not expected to be any >>> additional AFs defined anytime soon. >> >> currently the draft only supports 0 and 1. It says: >> >> "Prefix encoding for other address families is beyond the scope of this >> specification." > > Well, that would seem to imply that even though this specification doesn't > touch them, there is a possibility of using this for future additional > address families. So I think you need to say more about where it would be > in scope to do that work; this could involve making a registration in an > IANA registry for new family types, or a future IETF document that updates > this one, or probably some other mechanisms that I'm not thinking of right > now. The document says: "Prefix encoding for other address families is beyond the scope of this specification." So we do allow new specification to define a new AF if needed for the Range TLV. Although we do not see that happening very likely. > >> Given that we have other RFCs where 8-bit field is used for AF, can we >> leave it as we have it please? > > There are ways to resolve my discuss position that do not involve changing > the encoding or its description, yes. But see above. so what exactly would help to resolve the discuss? > > (And it would make the discussion of how to proceed easier if we had a > clear and solid answer about whether future extensions should be permitted > or not.) We are not precluding future extensions to AF if they happen. thanks, Peter > > -Benjamin > . >
- [Lsr] Benjamin Kaduk's Discuss on draft-ietf-ospf… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Acee Lindem (acee)
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Benjamin Kaduk
- Re: [Lsr] Benjamin Kaduk's Discuss on draft-ietf-… Peter Psenak