Re: [Sip] Support for Multipart/MIME

[Gonzalo Camarillo <[e-mail]>]

Hi Paul,

I have added a few guidelines about this in Section 5 of the new version 
of the draft:

http://users.piuha.net/gonzalo/temp/draft-camarillo-sip-body-handling-01.txt

With those guidelines and the behavior defined in other sections, we 
should be OK. Let me know if you agree or want to add further 
clarifications or behavior.

Thanks,

Gonzalo


Paul Kyzivat wrote:
> Revising one point:
> 
> Paul Kyzivat wrote:
> 
>> - What "handling" value should be used for multipart bodies and the 
>> contained body parts?
>>
>> If a body part is referenced by a cid: url in a header (or in another 
>> body part I suppose), then the handling of the body part should be 
>> required.
> 
> On reflection, this is tricky.
> 
> If the header containing the reference is optional (as most are), then 
> recipients that don't understand the header will have no need for the 
> referenced part. If it were required and they don't support the type, 
> then they would fail the request. This is bad.
> 
> So if processing of the header is optional, then the referenced body 
> part should have optional handling.
> 
> But then there could be a problem if the recipient does understand and 
> process the header, but doesn't understand the body part, and so because 
> it is optional doesn't process it. In that case, the cid reference will 
> be unsatisfied. This could also result in an inappropriate error.
> 
> I think the solution here is that if a header contains a cid url, and if 
> that url cannot be resolved to a body part that is supported, then the 
> UA should treat it the same as if the header itself was not understood - 
> typically ignoring it unless there is a Require in effect that demands 
> failing the request.
> 
> An alternative is to require that Content-ID be remembered even for 
> parts that are not understood, so that references can be resolved even 
> if they can't be processed. This would allow more precise errors to be 
> generated. This wouldn't be so hard at an outer level, but it might be 
> troublesome in conjunction with nesting.
> 
>     Paul



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