So, here's the guiding text:
2. Definition: message/sipfrag
A valid message/sipfrag part is one that could be obtained by
starting with some valid SIP message and deleting any of the
following:
o the entire start line
o one or more entire header fields
o the body
Thus, the body of any given sipfrag must be able to occur as the body
of some valid SIP message (that otherwise matches the rest of the
information in this given sipfrag of course).
So, for the particular example you are exploring, you are correct.
Advertising application/sdp and then only including a syntactically
incorrect SDP body would be incorrect. You'll need to put that
fractional SDP in something that makes sense from a MIME perspective:
either create an sdpfrag type, or shove it into a wrapper (text/plain?)
and make decoding it part of the semantics of whatever context you're
using such a thing in.
RjS
On Mon, 2004-06-21 at 11:19, Paul Kyzivat wrote:
> I received a question from a coworker regarding valid content for
> application/sipfrag. The question was:
>
> if the fragment represents part of a message that contained a body, can
> the fragment contain just a portion of the body?
>
> (I've generalized this - the actual question was whether the fragment
> could contain a Content-Type:application/sdp, and then contain just a
> portion of the actual sdp - a portion that was not syntactically correct
> SDP.)
>
> Based on my reading of rfc 3420, I think the answer is NO. But it does
> raise the question whether the answer (to the generalized question)
> *should* be YES. I'm undecided on this, and would like to hear other
> opinions, but I am inclined to be pretty lenient.
>
> In part there is an uncertainty principle here. How would you be able to
> tell a valid usage from an invalid one? Sipfrag is often used to relay
> messages received from others. It is possible that those received
> messages were ill-formed. In that case, a sipfrag that conveys the
> ill-formed message could appear identical to one that was obtained by
> invalid subsetting from a valid message. If you can't tell the
> difference, why ban the practice?
>
> Another reason is that there may be increasing reason to subset the body
> when building a sipfrag. For instance, the original message may have had
> a large multipart body. But for purposes of the sipfrag only one of the
> parts is significant.
>
> Paul
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