Re: [AVT] Re: Working group last call: draft-ietf-avt-evrc-smv-00.txt

Adam,

--> Stephen Casner writes:
>> (1) It does seem a little bit awkward to require that both format must be
>> supported when the wireless nodes will probably always use only one of them.
>>
>> However, I am not sure changing that word to "SHOULD" is going to either
>> make it look much better or eliminate the interoperability problem
>> completely.
>
>I agree, it does not eliminate the interoperability problem.  But I
>also believe it does not make the problem worse.  The interoperability
>problem stems from the fact that all parties concerned could not agree
>on a single format for all uses.  Hence, there are two formats and the
>possibility/probability that some implementations will support only
>the one that is appropriate for their perceived application
>environment.  This will be true whether the draft says MUST or
>SHOULD.
...
>> All it takes to add Type 1 support on top of Type 2 support (or vice versa)
>> for EVRC/SMV is to skipping a two octet header. "ptr += 2". My opinion is
>> that is a very small price to pay compare to the potential trouble and the
>> potential regret in the future.
>
>That is why I say SHOULD, not MAY.  But for an implementation in an
>environment where only one of the formats is feasible, e.g., if
>zero-byte header compression must be used, then it is not reasonable
>for the spec to say the implementation MUST include both as it does
>not meet the constrainst of RFC 2119 for that term.
>
>> Just my personal opinion though, and I am open to hear all
>> suggestions on this. If a "SHOULD" is what people thinks it should
>> be, I am allright with it.
>
>I would like to hear other opinions beyond mine and the authors'.

I largely agree with Steve on this issue. The MUST -> SHOULD change is to
reflect the reality that there will be non-interoperable implementations,
since there are some scenarios where one format doesn't make sense.

The trade-off is between optimizing the formats for particular uses and
maximizing interoperability. This draft choses the former: if that's not
an appropriate tradeoff, we should rethink the payload format design. If
it is appropriate, the draft should recognize the interoperability issue.

Colin

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