Re: [icnrg] Adoption of 'Alternative Delta Time Encoding for CCNx Using Compact Floating-Point Arithmetic' (draft-gundogan-icnrg-ccnx-timetlv)

Hitoshi Asaeda <asaeda@ieee.org> Mon, 03 August 2020 09:20 UTC

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From: Hitoshi Asaeda <asaeda@ieee.org>
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Date: Mon, 3 Aug 2020 18:20:22 +0900
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References: <68D3AAD3-59E1-43AE-8722-06776AED4607@dkutscher.net> <E979BEAD-A9D1-484B-A46F-87069859F3B6@ieee.org> <874kpnj3d6.fsf@gundogan.net> <BA249AC5-3673-4377-9199-D9A7AE4E3519@dkutscher.net> <061E0BE0-AEB5-40F4-8C0C-F3163EEF58D7@parc.com>
To: Marc Mosko <mmosko@parc.com>
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Subject: Re: [icnrg] Adoption of 'Alternative Delta Time Encoding for CCNx Using Compact Floating-Point Arithmetic' (draft-gundogan-icnrg-ccnx-timetlv)
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Hi Marc,

Thanks for your proposal.
I have a few questions.

> On Aug 1, 2020, at 2:44, Marc Mosko <mmosko@parc.com> wrote:
> 
> Here are my thouhts on paths to encode the compressed time.  I think there are a few ways to go forward.  I'll discuss a few pros/cons after enumerating them.
> 
> 1) Add a new RFC that specifies the compressed time and have it grab its own TLV from IANA.  No modification of RFC8609 needed.   The new RFC should maintain the behavior that L=0 implies no response is expected (i.e. a purely push notification via Interest) -- or specify some other mechanism to indicate that condition if this new TLV is present.

This is one of the reasonable ideas.

> 2) Modify 8609 so InterestLifetime understands that L=1 implies compressed form and L > 1 implies normal (milliseconds).  This would update Sec 3.4.1.  I do not think 8569 needs modification.  

Dose this idea require 8609 modification? I think this idea simply requires adding new type values and coexists with the current ones. Am I wrong? If routers do not understand the new type values with L=1 (L=1?, not L=0?), they simply drops the packet or ignores the field. This commonly happens on old routers that do not support new RFCs in some phase and can be addressed by supporting the new RFCs later.

Regards,

Hitoshi


> 3) Modify 8609 so InterestLifetime uses some method to encode its encoding, e.g. 1 byte for a mechanism and 1+ bytes for value.  It defeats having a super-tiny encoding, but it's better than wrapping a TLV in a TLV.  Or you could do something more bit-oriented if you wanted to really compress it out, but I suspect that for anything practical it would spill over to 2 bytes anyway.
> 
> Regardless of option #1 or #2 or #3, forwarders need to be modified to understand the compressed time.  A possible PRO of #1 is that if an implementation does not understand it, it will assume some default InterestLifetime.   A possible CON of #2 is that if a router does not know of the update, it would assume the lifetime is some 1 - 255 msec value.
> 
> #3 has the same downsides as #2 -- a non-conforming router would think the value was those 2 bytes.   I'm not sure it has any advantages over #1.  At the moment, I think #1 is better than #3.
> 
> I do not think that 8569 needs modification to accommodate #1.  The specs already say how to add a new Hop-By-Hop header (https://tools.ietf.org/html/rfc8609#section-4.3).
> 
> I look forward to our interim meeting,
> Marc
> 
> On 7/31/20, 6:46 AM, "icnrg on behalf of Dirk Kutscher" <icnrg-bounces@irtf.org on behalf of ietf@dkutscher.net> wrote:
> 
>    Hi everyone,
> 
>    Hitoshi-san, let me ask you this way: what problems do you see with 
>    updating RFC8609?
> 
>    Best regards,
>    Dirk
> 
> 
>    On 31 Jul 2020, at 14:06, Cenk Gündoğan wrote:
> 
>> Hello Hitoshi,
>> 
>> thank you for your feedback, my comments follow further down inline.
>> 
>> On Fri, Jul 31 2020 at 11:51 +0200, Hitoshi Asaeda wrote:
>> 
>>> Hi,
>>> 
>>> I don't deny the proposal itself but have a concern about the 
>>> intention; "update" RFC8609.
>>> 
>>> Why does this draft update RFC8609? Why can't we keep RFC8609 as is 
>>> and propose the new type values for this proposal as the addition?
>>> The time TLV proposed in this document can coexist with RFC8609 if 
>>> you use the new type values. Why does this need to replace the time 
>>> TLV defined in 8609? Is there any errata reported for the time TLV 
>>> defined in 8609?
>> 
>> the current version of this document describes a few alternatives on 
>> how
>> to integrate the compressed time TLV into CCNx. One alternative 
>> proposes
>> to use the Length (L) field of the InterestLifetime TLV to identify 
>> the
>> included encoding (normal time (L>1) vs. compressed time (L==1)
>> representation). This would require a change in RFC8609 (Section 3.4.1
>> [1]).
>> 
>> Another alternative might update the message ABNF in Section 2.1 [2] 
>> of
>> RFC8569 to add a new top-level TLV for the compressed 
>> InterestLifeTime.
>> 
>> [1] https://tools.ietf.org/html/rfc8609#section-3.4.1
>> [2] https://tools.ietf.org/html/rfc8569#section-2.1
>> 
>>> 
>>> My comment is that it is better to discuss this document without an 
>>> intention of updating RFC8609.
>> 
>> All proposed integration alternatives display advantages and
>> disadvantages. Getting group feedback on this particular topic is 
>> quite
>> valuable for the progression of this work. Thanks! We could also
>> reiterate over the existing integration ideas again (on the list?) in
>> order to stimulate new ideas and solutions (comparable to a draft
>> presentation?).
>> 
>> Best,
>> Cenk
>> 
>>> 
>>> Regards,
>>> 
>>> Hitoshi
>>> 
>>> 
>>>> On Jul 29, 2020, at 21:39, Dirk Kutscher <ietf@dkutscher.net> wrote:
>>>> 
>>>> Hi ICNRG,
>>>> 
>>>> This draft 
>>>> (https://datatracker.ietf.org/doc/draft-gundogan-icnrg-ccnx-timetlv/) 
>>>> is intended as an update to RFC 8609 (CCNx Messages in TLV Format).
>>>> 
>>>> The authors have just submitted an update that addresses previously 
>>>> made technical comments.
>>>> 
>>>> We believe that it would be appropriate to give change control to 
>>>> the Research Group, so the chairs would like to solicit statements 
>>>> indicating support for adoption or concerns against it from people 
>>>> who are 1) not co-authors and 2) have read the latest version.
>>>> 
>>>> In case there are questions that you would like to discuss 
>>>> interactively, we should be able to make some time for that on the 
>>>> Monday Interim meeting -- let us know.
>>>> 
>>>> Thanks and best regards,
>>>> 
>>>> Chairs
>>>> 
>>>> _______________________________________________
>>>> icnrg mailing list
>>>> icnrg@irtf.org
>>>> https://www.irtf.org/mailman/listinfo/icnrg
>>> 
>>> _______________________________________________
>>> icnrg mailing list
>>> icnrg@irtf.org
>>> https://www.irtf.org/mailman/listinfo/icnrg
>> 
>> --
>> Cenk Gündoğan
>> 
>> Hamburg University of Applied Sciences
>> Dept. of Computer Science / Internet Technologies Group
>> Berliner Tor 7, 20099 Hamburg, Germany
>> Fon: +49 40 42875 - 8426
>> Mail: cenk.guendogan@haw-hamburg.de
>> Web: https://www.inet.haw-hamburg.de/
>> _______________________________________________
>> icnrg mailing list
>> icnrg@irtf.org
>> https://www.irtf.org/mailman/listinfo/icnrg
> 
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