Subject: RE: [SIP] SIP App Components

From: [email-masked]
Date: Fri, 5 Jan 2001 01:05:54 -0700

As Sean said, multipart MIME shouldn't crash a UA. There is a defined
behavior for a UA that does not support a given MIME type (including
multipart/mixed or what have you) that it receives in a SIP request; namely,
responding with a 415 with an Accept header indicating the MIME types that
it does accept. Presumably, the sender of the request will resend, if
possible, limiting the included bodies to those specified in the Accept.
Minimal telephony SIP implementations might only Accept application/sdp,
certainly.

I'm not sure if this constitutes choking - it may slow session set-up time,
but it shouldn't result in crashes, undefined behavior, etc. In my
experience, even some small user agents (SIP phones) implement this 415
mechanism.

There is also the Content-Disposition header, which allows the sender of a
SIP message to indicate whether or not a given MIME body is necessary for
processing the session... but I'm not sure how widely implemented
Content-Disposition is to date. With Content-Disposition the session will
not be unnecessarily delayed by 415-style negotiation.

Jon Peterson
Level(3) Communications

-----Original Message-----
From: Eric Burger [mailto:[email-masked]]
Sent: Thursday, January 04, 2001 4:58 PM
To: [email-masked]
Subject: [SIP] SIP App Components

The SIP App Components infrastructure assumes that the SIP UA's understand
multipart MIME body parts.  This is a MAY in bis 02 (Section 8.2).

Is it safe to assume that the current SIP infrastructure won't choke on SIP
INVITES and potentially responses with multipart MIME, instead of
application/sdp, body parts?

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