Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf-roll-turnon-rfc8138-14: (with DISCUSS and COMMENT)
Martin Duke <martin.h.duke@gmail.com> Tue, 10 November 2020 23:16 UTC
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References: <20200911162617.GQ89563@kduck.mit.edu> <8F19C753-DCA0-4A32-BA3B-A124B2F7F745@cisco.com> <MN2PR11MB3565F2602A0DC55DE9FF3604D83F0@MN2PR11MB3565.namprd11.prod.outlook.com> <CAM4esxQBL+4wNzJTZ_+QKMCGuo4fgyxZKxr3xmFDVEAn9J7HLQ@mail.gmail.com> <E8B2CE91-7FEE-4728-A280-935B69EF3E91@cisco.com> <CAM4esxQpcWROj9mMd3iUXr1EF8kvoF8Zmq-w4BPFVW+BtDU93w@mail.gmail.com> <117497.1600481093@dooku> <MN2PR11MB356549C173D8027709AAC777D8390@MN2PR11MB3565.namprd11.prod.outlook.com> <CAMMESswOs7ZQ3502dNYBN=qJp7O9Ddi=F3UL40Ce7JGknMq-wA@mail.gmail.com> <MN2PR11MB3565C3DB9AFAABD9E8F57CF4D8330@MN2PR11MB3565.namprd11.prod.outlook.com> <20201110033438.GE39170@kduck.mit.edu> <CO1PR11MB48815ED81CFBBF1EC97A2DB2D8E90@CO1PR11MB4881.namprd11.prod.outlook.com>
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From: Martin Duke <martin.h.duke@gmail.com>
Date: Tue, 10 Nov 2020 15:16:08 -0800
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To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>
Cc: Benjamin Kaduk <kaduk@mit.edu>, Alvaro Retana <aretana.ietf@gmail.com>, The IESG <iesg@ietf.org>, "draft-ietf-roll-turnon-rfc8138@ietf.org" <draft-ietf-roll-turnon-rfc8138@ietf.org>, Routing Over Low power and Lossy networks <roll@ietf.org>, "roll-chairs@ietf.org" <roll-chairs@ietf.org>, Michael Richardson <mcr+ietf@sandelman.ca>
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Subject: Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf-roll-turnon-rfc8138-14: (with DISCUSS and COMMENT)
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OK, We will eventually get there, but this will never stop being weird to me. :-) Imagine 5 types of DODAG nodes: Type 8138? this draft? MOP5? MOP 7? ------- ------- ------------ -------- ---------- A N N N N B Y N N N C Y Y N N D Y Y Y N E Y Y Y Y So if IIUC, the current state of play is that B can't gracefully deploy into a network with A, because they have to be statically configured to not-compress. As long as B is upgraded to this draft (C), it can gracefully deploy in a network with A, because compression will remain off until all the A is gone. C and B can function together without this draft, but they won't be able to dynamically change compression state, FWIW. Similarly, a hypothetical D can gracefully deploy with A, as it will have use of these flags, but doesn't really need the flags to work with B or C unless you want to dynamically change state for some reason. Meanwhile, E will *not *be able to gracefully deploy with A, because it does not have a means to change its compression state using the DODAG configuration. But because of the sentence we've discussing in this thread, networks with C and D will have no problem because they have this text to help them decide whether or not to compress. They will not have the ability to dynamically change compression state. So I guess the value of the MOP 7 behavior is... to recover the bit of the flags? Fine, I suppose, but this would appear to have two costs: 1) If A is still out there when E deploys, this bit would have been useful, but isn't. 2) I have no idea if the "dynamic change in compression state" use case is valuable it all, but it would certainly foreclose the possilbilty. Do I have this right? Martin On Tue, Nov 10, 2020 at 12:15 AM Pascal Thubert (pthubert) < pthubert@cisco.com> wrote: > Hello Benjamin: > > > That said, and my apologies for a hazy memory coming back to this after a > > couple months, in a year or N from now when mopex is finalized, how will > > someone looking at mopex know to use RFC8138 on links where 6LoWPAN > > Header Compression applies (and not use it otherwise)? We are claiming > in > > the -14 of this document that: > > > > For a MOP value of 7, [RFC8138] MUST be > > used on Links where 6LoWPAN Header Compression [RFC6282] applies and > > MUST NOT be used otherwise. > > > > but I am not sure (or have forgotten) what the chain of references is > supposed > > to lead someone who is implementing RPL plus MOP=7 to the requirement to > > use RFC 8138. I don't think we should just rely on the mopex text to do > so, > > since we are trying to impose the requirement with this document (which > > predates mopex by some time), and there's not anything (other than our > > collective memories, of course) requiring mopex to remain consistent with > > that requirement. > > Just to be clear for the other readers: MOPext does not exist as a > normative reference for this work. > The only field that exists is the MOP field in the DIO and that field is 3 > bits long, values 0..7. > > The normative reference that you are after is > https://datatracker.ietf.org/doc/draft-ietf-roll-useofrplinfo/ > This is the spec that updates RPL and changes the IANA registry to > indicate that 7 is not a MOP. > > There we have: > > " > > ... > > Anticipating future work to revise RPL relating to how the LLN and > DODAG is configured, this document changes the interpretation of the > [dodagcfg] Registry to be limited to Mode-of-Operation (MOP) > specific. The MOP is described in [RFC6550] section 6.3.1. The > Options Flags Registry is renamed, and applies to MOP values zero (0) > to six (6) only, leaving the flags reserved for MOP value seven (7). > > In addition, this document reserves MOP value 7 for future expansion. > > ... > > 11.3. Change MOP value 7 to Reserved > > This document changes the allocation status of the Mode of Operation > (MOP) [ianamop] from Unassigned to Reserved. This change is in > support of future work related to capabilities. > " > > So basically we tell the implementations from now on to test if MOP is 7, > and in that case, the Options Flags are undefined. In other words, if MOP > is 7, the stack must not use the option flags as if the MOP was <7. In > fact, 7 is no more a MOP value but a reserved thingy that can be overloaded > in the future. And yes, we intend to do just that in MOPExt. > > Until that happens, implementations are at a loss if they encounter when a > MOP field that is all ones. So we need to give them instructions to cope > with the situation. This draft derives whether to use RFC 8138 from whether > the 6LoWPAN compression applies to the link or not. > > This will stay true forever, unless another RFC amends it. When/if that > happens, the new RFC will have to consider backward compatibility with a > legacy implementation that implements the above. > > Note that this line of thought applies to 3 flags, defined respectively in: > - https://datatracker.ietf.org/doc/draft-ietf-roll-useofrplinfo/ > - https://datatracker.ietf.org/doc/draft-ietf-roll-turnon-rfc8138/ > - https://datatracker.ietf.org/doc/draft-ietf-roll-unaware-leaves/ > > Keep safe! > > Pascal > > > > > Thanks, > > > > Ben > > > > On Wed, Sep 30, 2020 at 04:25:10PM +0000, Pascal Thubert (pthubert) > wrote: > > > Hello Alvaro > > > > > > I uploaded both draft with the suggested update, please see > > > > > > https://tools.ietf.org/rfcdiff?url2=draft-ietf-roll-turnon-rfc8138-17. > > > txt > > > https://www.ietf.org/rfcdiff?url2=draft-ietf-roll-unaware-leaves-21.tx > > > t > > > > > > Keep safe > > > > > > Pascal > > > > > > > -----Original Message----- > > > > From: Alvaro Retana <aretana.ietf@gmail.com> > > > > Sent: jeudi 24 septembre 2020 17:49 > > > > To: Pascal Thubert (pthubert) <pthubert@cisco.com> > > > > Cc: Benjamin Kaduk <kaduk@mit.edu>; The IESG <iesg@ietf.org>; > > > > draft-ietf- roll-turnon-rfc8138@ietf.org; Martin Duke > > > > <martin.h.duke@gmail.com>; Routing Over Low power and Lossy networks > > > > <roll@ietf.org>; roll- chairs@ietf.org; Michael Richardson > > > > <mcr+ietf@sandelman.ca> > > > > Subject: Re: [Roll] Benjamin Kaduk's Discuss on > > > > draft-ietf-roll-turnon-rfc8138- > > > > 14: (with DISCUSS and COMMENT) > > > > > > > > On September 24, 2020 at 8:13:09 AM, Pascal Thubert wrote: > > > > > > > > > > > > Pascal: > > > > > > > > Hi! > > > > > > > > > Following the meeting last Monday and subsequent the update of > > > > > useofrplinfo by Michael (thanks Michael!) I published a new > > > > > version of the turnon RFC > > > > > 8138 draft. > > > > > > > > > > The major changes are > > > > > - removed the formal update to RFC 6550 > > > > > - refer to useofrplinfo as the justification why the flag is not > > > > > defined for MOP 7 > > > > > - defined the operation in MOP 7 as compression on iff the Link > > > > > uses 6LoPWAN HC. > > > > > > > > Thanks for these changes. > > > > > > > > Because we have to cycle useofrplinfo back through (when the WG is > > > > done with it), I asked Ben/Martin to wait for that before coming > > > > back to this document. It'll make it easier than tracking multiple > > > > changes. :-) > > > > > > > > > > > > OTOH, I do have comments on the recent change: > > > > > > > > OLD> > > > > Section 4.3 of [USEofRPLinfo] updates [RFC6550] to indicate that > > > > the > > > > definition of the Flags applies to Mode of Operation (MOP) values > > > > zero (0) to six (6) only, leaving the flags reserved for MOP > > > > value > > > > seven (7). For a MOP value of 7, the bit in position 2 is > > > > considered > > > > unallocated and [RFC8138] MUST be used on Links where 6LoWPAN > > > > Header > > > > Compression [RFC6282] applies and MUST NOT be used otherwise. > > > > > > > > NEW> > > > > > > > > Section 4.3 of [USEofRPLinfo] updates [RFC6550] to indicate that > > > > the > > > > definition of the Flags applies to Mode of Operation (MOP) values > > > > zero (0) > > > > to six (6) only. For a MOP value of 7, [RFC8138] MUST be used on > > > > Links > > > > where 6LoWPAN Header Compression [RFC6282] applies and MUST NOT > > > > be used > > > > otherwise. > > > > > > > > > > > > Thanks! > > > > > > > > Alvaro. >
- [Roll] Benjamin Kaduk's Discuss on draft-ietf-rol… Benjamin Kaduk via Datatracker
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Alvaro Retana
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Alvaro Retana
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Alvaro Retana
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Alvaro Retana
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- [Roll] Agenda for Monday (Re: MOP==7 live discuss… Michael Richardson
- Re: [Roll] Agenda for Monday (Re: MOP==7 live dis… Pascal Thubert (pthubert)
- Re: [Roll] Agenda for Monday (Re: MOP==7 live dis… Alvaro Retana
- Re: [Roll] Agenda for Monday (Re: MOP==7 live dis… Ines Robles
- Re: [Roll] Agenda for Monday (Re: MOP==7 live dis… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Alvaro Retana
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Benjamin Kaduk
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Pascal Thubert (pthubert)
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Michael Richardson
- Re: [Roll] Benjamin Kaduk's Discuss on draft-ietf… Martin Duke