On Tue, 2008-12-02 at 11:59 +0100, Ian Elz wrote: > Section 3.2 Attended Transfers > > In F8, INVITE to Carol you have included a References header with > “rel-xfer”. > > How does Bob’s UA know to include this header at this time? Bob has > an existing session with Alice but at the time of the INVITE to Carol, > F8, the UA does not know that a transfer is intended. The INVITE may > be an enquiry call with no intent to transfer. Are you proposing that > all INVITE requests when you have another session on hold will include > this header in case you decide to transfer later?
In the phones that I am familiar with, the first step of the consultative transfer process (putting the first leg on hold) is done by invoking a specific consultative transfer operation. In this case, the phone can annotate the INVITE of the second leg as being part of a consultative transfer process. I had not thought of the case were the phone was not aware that a consultative transfer was in progress until after the second leg had been established. I suppose that in this case, we could rely on the remaining messages in the consultative transfer process to carry the dialog correlations (section 3.2): An attended transfer normally involves three different dialogs. If the transfer completes, and the REFER that completes the transfer has a References header, the References header in the REFER and the Replaces header in the resulting INVITE will suffice to connect the three dialogs. (Although that text is not correct: The REFER does not need a References header. The INVITE starting the third (final) dialog will contain a References header naming the leg that carried the REFER, and it will also carry a Replaces header (derived from the Replaces header-parameter in the Refer-To URI of the REFER) that names the other leg.) > Section 3.3 Call Pick-up > > F3 is a Subscribe using the dialog event package. RFC 4235 requires > that the dialog event package includes a Call-id and a To-tag. Am I > missing something here? Perhaps there is another request which is not > included in your diagram? > > Can you please clarify? I'm not sure I understand what you mean. The dialog event package will be the body of the NOTIFY (F5), which is not illustrated. The SUBSCRIBE (F3) is illustrated with a Call-Id and from-tag. (It has no to-tag because it is out-of-dialog.) Dale _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
