Subject: Re: [Sip] Draft defining the Accept-Disposition header field

From: Gonzalo Camarillo <[email-masked]>
Date: Tue, 01 Feb 2005 22:51:08 +0200

Hi Cullen,

inline:

Cullen Jennings wrote:

>>>I'm not really sure what the problem is that this solves.
>>
>>it lets a UA know whether the remote UA supports a particular
>>disposition type. Right now, UAs guess this information based on the
>>support for MIME types. For example, if the remote UA supports
>>application/sdp, my UA assumes that the remote UA supports the 'session'
>>disposition type... but what about 'early-session'?
>> 
> 
> Seems like Supported header is a better way to solve this particular issue

Yes, we can define new option tags for everything we want to 
negotiate... but defining an option tag that just means "I support this 
disposition type" seems like duplicating stuff unnecessary (e.g., 
defining an option tag that means that the UA supports the early-session 
disposition type).

In addition, we have an error response (415) that, per its definition, 
should be returned if the UAS does not support a MIME type or a 
disposition type in the request... we have a means to express which MIME 
types the UAS supports if the problem was an unknown MIME type, but we 
do not have anything to express which disposition types the UAS 
supports, in case the problem had to do with a disposition type. This 
information can come handy for debugging.

> I guess I am wondering if using the MIME dispositions is really the right
> way to basically tell the UA what you want it to do with a given SIP command
> - what does recipient-list mean in the context of email or other users of
> MIME?

Yes, it has already been pointed out that disposition types are context 
dependent. The issue is that, in email, any disposition type belongs to 
the same context: the reception of an email message. In SIP, we have 
different contexts. For example, the reception of a body whose 
disposition type is 'session' in an INVITE request makes sense, but what 
happens if it is received in a MESSAGE?

Gonzalo

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From: Gonzalo Camarillo <[email-masked]>
Date: Tue, 01 Feb 2005 22:53:09 +0200

Hi Cullen,

inline:

In any event, as Paul suggested, I believe it is good to analyze all the 
issues related to SIP and MIME stuff and make decisions in one way or 
another. At this point, there are issues that haven't got enough attention.

Gonzalo