Subject: [Sip] REFER failures

From: "Henning G. Schulzrinne" <[email-masked]>
Date: Fri, 29 Jun 2001 10:31:54 -0400

One issue that has come up in implementing REFER is that the failure
indication is not quite as unambiguous as I'd like. Currently, it is
hard to distinguish whether the referred call failed or whether the
target of the REFER couldn't or wouldn't execute the REFER, if this
failure isn't immediate. Typical example: the recipient of the REFER
will probably get a pop-up window asking whether it actually wants to
make that call. However, a final response to the REFER needs to be
returned immediately, so only NOTIFY can be used to indicate that the
REFER failed later, e.g., because the REFER recipient refused to act on
the REFER.

We can fake this by including the status response of the REFER recipient
in the NOTIFY body (e.g., 603), but that's ambiguous as to who declined.
One solution is that the NOTIFY always includes the full SIP response,
so that it's clear what this refers to. For late failures of the REFER
(rather than the request triggered by it), it would be the final
response that would have been sent, e.g.,

SIP/2.0 603 Refused
From: sender of REFER
To: recipient of REFER
Call-ID: of original REFER
CSeq: something REFER

Whether it makes sense to use 202 as the final response in this case is
another, more secondary question.
-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs

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---

From: "Bob Penfield" <[email-masked]>
Date: Fri, 29 Jun 2001 11:11:47 -0400

----- Original Message -----
From: "Henning G. Schulzrinne" <[email-masked]>
To: <[email-masked]>
Sent: Friday, June 29, 2001 10:31 AM
Subject: [Sip] REFER failures

> Call-ID: of original REFER

We've been discussing the idea of a Reason header in BYE and CANCEL
requests. Would that be useful in a NOTIFY request to convey the "603
Refused"?