Subject: [SIP] Transfer Primitives

From: Billy Biggs <[email-masked]>
Date: Mon, 22 Jan 2001 13:12:00 -0500

Here is my vision for SIP transfer primitives.  This is my personal
opinion, and is not reflected in any of the current drafts.

  I see three distinct primitives:

  1. HANDOFF
      - 3-way call handoff and blind transfer with recovery-on-fail.
      - Transferee never mixes, media stops when HANDOFF accepted.
      - Status is sent using a header in BYE (leave old call) or
        re-INVITE (regain old call).

  2. JOIN
      - Transferee-mixes attended transfer.
      - Request a conference bridge to call-in another party.
      - Status is optionally sent using a NOTIFY (implicit subscribe).

  3. REFER
      - Refer a person to a URL.
      - Useful to refer someone to an HTTP URL, or tell someone a SIP
        URL for their address book.
      - Interactive pop-up with a 'view in browser' or 'save to
        bookmarks' etc.
      - Status is never sent (doesn't make sense with most URL schemes).

  I believe that the implementation of these is sufficiently distinct to
warrant seperate methods.  I expect everybody to implement HANDOFF for
basic call transfer, and a smaller group to implement REFER/JOIN for
more advanced services.

-- 
Billy Biggs                     [email-masked]
http://www.billybiggs.com/      [email-masked]

_______________________________________________
This list is for continuing development of the SIP protocol.
The sip-implementer's list is the place to discuss implementation,
and to receive advice on understanding existing sip.
To subscribe to it, send mail to [email-masked] with
"subscribe sip-implementors" in the body.