Re: [Roll] trickle-mcast-04 - Clarify scope value of 3 - subnet-local

Robert Cragie <robert.cragie@gridmerge.com> Fri, 26 July 2013 07:46 UTC

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Date: Fri, 26 Jul 2013 08:46:00 +0100
From: Robert Cragie <robert.cragie@gridmerge.com>
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Subject: Re: [Roll] trickle-mcast-04 - Clarify scope value of 3 - subnet-local
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+1 to all Ralph says below.

I support draft-droms-6man-multicast-scopes-00 with the addition of 
using MPL as an example.

Robert

On 25/07/2013 15:46, Ralph Droms (rdroms) wrote:
> On Jul 25, 2013, at 4:07 PM 7/25/13, Michael Richardson <mcr+ietf@sandelman.ca> wrote:
>
>> Ralph Droms (rdroms) <rdroms@cisco.com> wrote:
>>>> Ralph Droms (rdroms) <rdroms@cisco.com> wrote:
>>>>>> I would still like an explanation of why "subnet" is the wrong term.
>>>>>>
>>>>>> When would scope-3 would be used such that it would not correspond to the set
>>>>>> of links on which a "/64" (or other size) is used?
>>>>> Hm, I thought I responded but apparently not...
>>>>> This change to scope 0x03 is not just for MPL, so we don't know how
>>>>> else it might be used in the future.
>>>> I understand, but perhaps it would be better, if, when another use case comes
>>>> along, they write a document explaining why scope-3 is correct and
>>>> non-conflicting with the trickle mcast use case.
>>> I don't agree; in my opinion, it's better to release scope 0x03 from
>>> "reserved" state and give guidelines for its use.
>> I think that we agree about what we want.
> Sorry, I disagree.  I simply want to release the scope from "(reserved)" state and write down whatever constraints needed for consistency with other scopes.
>
> Jinmei-san (if I may make an inference from his e-mail) supports writing this definition into  and made the helpful suggestion to add the MPL use case as an example, which I support.
>
>> What I see you saying is that you want a definition which I find rather
>> (technically) vague, in anticipation of uses which are not yet well defined,
>> and may never come to pass.
>>
>> I'm saying, let's make the MPL scope-3 use case clear and precise, and if
>> another situation comes along for which scope-3 is appropriate, let's extend
>> the definition at that time.
>>
>> Otherwise, this reminds of site-local scope:
>>   We defined it in what we thought were clear terms for a human, but which
>>   turned out to be too vague for machines, with the result that it could never
>>   be discovered/used.
>>
>> Meanwhile, I think that MPL is hung up waiting for this to be properly
>> clarified.
> Really?  I suggest MPL is hung up waiting author revisions for several last call comments, including this one - none of which have been addressed since the last call back in March.  This issue could be addressed directly in the roll WG by explicitly writing down the behavior of scope 0x03 for MPL forwarding in the MPL spec, which is, in my opinion, where it belongs.
>
> My point is that, in my opinion, reserving scope 0x03 for MPL is not the right thing to do.
>
> - Ralph
>
>> --
>> Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
>>
>>
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