Subject: RE: [Sip] SIP session without SDP

From: "Eric Burger" <[email-masked]>
Date: Fri, 28 Oct 2005 16:24:27 -0400

I actually do know of a situation where you would setup a call with no
media: KPML.

Let's say you want to establish a signaling-only session for
transporting digits only.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Paul Kyzivat
Sent: Thursday, October 06, 2005 9:30 AM
To: Christer Holmberg (JO/LMF)
Cc: [email-masked]
Subject: Re: [Sip] SIP session without SDP

Christer Holmberg (JO/LMF) wrote:
> Hi,
> 
> Chapter 13.2.1 in RFC3261 says that, if the INVITE does not contain an
session description offer, the response  (reliable) MUST contain an
session description answer.
> 
> First, it is not said that the session description must be a SDP body,
so I assume something else could be used too?
> 
> Second, assume that I want to set up a session without SDP (or,
another type of session description)? If I include an empty Accept
header (or an Accept header where application/sdp is not listed) I don't
think the UAS should be mandated to include an SDP offer in the
response.
> 
> So, I think the rules in 13.2.1 shall be applicable IF I am using a
session description, but I should NOT be mandated to use session
description.

So you want to set up a session that has no description? Why would you 
want to do that?

That seems *so* wrong! The whole point of INVITE is to negotiate the 
details of the session.

Yes, you could use something else besides SDP - the obvious candidate is

SDPng. But using none doesn't seem to fit the intent of INVITE.

You can get much the effect you seem to be seeking simply by using SDP 
that has no m= lines.

	Paul

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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 28 Oct 2005 18:11:42 -0400

> transporting digits only.

Am I missing something? If that is all you want to do, then simply send 
a subscription for the KPML event package. You don't need a media-less 
INVITE to do that.

	Paul