To rephrase what Eric is saying here in base principles: _inferring_
what can be done with INFO by examining supported content types is a "Do
What I Mean" mechanism (as opposed to a "Do What I Say" mechanism). "Do
What I Mean" is a well-known recipe for interoperability failure. (For a
well constructed discussion of this, see Jonathan's service indication
draft).
This is, for example, why we have an "Event" header field in RFC 3265
instead of simply inferring the event package from MIME type. (In fact,
this is why I started the draft that became 3265 in the first place --
with the dual uses of PINT and presence threatening to take the
SUBSCRIBE method down the path that INFO unfortunately ended up taking,
an intervention was necessary).
To re-cast Eric's example from a slightly different angle: imagine that
a desired usage of INFO most naturally used application/sdp as its
payload. How would one indicate support for such a usage?
/a
Christer Holmberg (JO/LMF) wrote:
Hi,
I still don't get it, but let's take it face-to-face at some point :)
Regards,
Christer
-----Original Message-----
From: Eric Burger [mailto:[EMAIL PROTECTED]
Sent: 22. heinäkuuta 2007 10:14
To: Christer Holmberg (JO/LMF); IETF SIP
Subject: Re: [Sip] INFO and Content Negotiation
That is the point - people have been saying, "I can negotiate
INFO by using Content-Type." This is a tiny example where
using Content-Type to negotiate "INFO Packages" falls apart.
On 7/22/07 3:10 AM, "Christer Holmberg (JO/LMF)"
<[EMAIL PROTECTED]> wrote:
Why would I be expecting KPML, if I have only indicated
that I support
DTMF-over-INFO?
If I was to expect KPML, I would first need to establish a
subscription for KPML (or, in our "controlled network", the
subscription would be established by default, and I would
know you are going to send KPML).
Regards,
Christer
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