Subject: Re: [Sip] INFO method used for ISUP to SIP IW (2nd round)

From: [email-masked]
Date: Fri, 12 Aug 2005 10:22:56 EDT

In a message dated 8/12/2005 9:23:43 AM Eastern Daylight Time, 
[email-masked] writes:

> This point about when INFO can be used was one raised by Ericsson, and 
> actually resulted in delay of approval of the specification.  The view 
> was that INFO could not be sent until an early dialogue had been 
> established.  That has nothing to do with whether the 183 response is 
> reliable or not.
> 

I don't think there was ever a question that INFO could not be used before an 
early dialog. The issue is whether or not it can be used after an early 
dialog is established and before the confirmed dialog. After all the discussion, I 
don't believe that there was a solid answer, since IETF RFCs and Q.1912.5 seem 
to be contradictory (for the callee to caller direction).

There really isn't a clear statement in any RFC, except that INFO follows the 
rules for BYE. RFC 3261 (which was written later) says that the BYE can only 
be sent in the callee to caller direction on a confirmed dialog.

Q.1912.5 indicates that the INFO can be sent (callee to caller direction) 
before confirmed dialog is established.

So which is correct? Can the INFO be used during the early dialog state in 
the callee to caller direction? This is critically important for the operation 
of SIP-T.

Mike Pierce
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From: "Tom-PT Taylor" <[email-masked]>
Date: Fri, 12 Aug 2005 14:03:02 -0400

Once upon a time I figured I'd clarify the situation by updating the 
INFO specification.  I suppose I could still do that, but I was a bit 
nervous about what else might happen to that spec. if it were reopened.

Anyway, you've stated the ITU-T interpretation.