draft-ietf-sipping-early-disposition-00.txt   draft-ietf-sipping-early-disposition-01.txt 
SIPPING Working Group G. Camarillo SIPPING Working Group G. Camarillo
Internet-Draft Ericsson Internet-Draft Ericsson
Expires: May 18, 2004 November 18, 2003 Expires: July 13, 2004 January 13, 2004
The Early Session Disposition Type for the Session Initiation The Early Session Disposition Type for the Session Initiation
Protocol (SIP) Protocol (SIP)
draft-ietf-sipping-early-disposition-00.txt draft-ietf-sipping-early-disposition-01.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
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This Internet-Draft will expire on May 18, 2004. This Internet-Draft will expire on July 13, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
This document defines a new disposition type (early-session) for the This document defines a new disposition type (early-session) for the
Content-Disposition header field in SIP. The treatment of Content-Disposition header field in SIP. The treatment of
"early-session" bodies is similar to the treatment of "session" "early-session" bodies is similar to the treatment of "session"
bodies. That is, they follow the offer/answer model. Their only bodies. That is, they follow the offer/answer model. Their only
difference is that session descriptions whose disposition type is difference is that session descriptions whose disposition type is
"early-session" are used to establish early media sessions within "early-session" are used to establish early media sessions within
early dialogs, as opposed to regular sessions within regular dialogs. early dialogs, as opposed to regular sessions within regular dialogs.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Issues Related to Early Media Session Establishment . . . . . . 3 3. Issues Related to Early Media Session Establishment . . . . . . 3
4. The Early Session Disposition Type . . . . . . . . . . . . . . . 4 4. The Early Session Disposition Type . . . . . . . . . . . . . . . 4
5. Preconditions . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Preconditions . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Option tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Option tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8
Normative References . . . . . . . . . . . . . . . . . . . . . . 8 Normative References . . . . . . . . . . . . . . . . . . . . . . 8
Informational References . . . . . . . . . . . . . . . . . . . . 8 Informational References . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . 9
1. Introduction 1. Introduction
A SIP [2] user agent establishing an INVITE dialog may need to A SIP [2] user agent establishing an INVITE dialog may need to
exchange media with the destination user agent (or user agents if the exchange media with the destination user agent (or user agents if the
INVITE forks) or with application servers in the path before the INVITE forks) or with application servers in the path before the
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We define a new disposition type for the Content-Disposition header We define a new disposition type for the Content-Disposition header
field: early-session. User agents MUST use early-session bodies to field: early-session. User agents MUST use early-session bodies to
establish early media sessions in the same way as they use session establish early media sessions in the same way as they use session
bodies to establish regular sessions, as described in RFC 3261 [2] bodies to establish regular sessions, as described in RFC 3261 [2]
and in RFC 3264 [3]. Particularly, early-session bodies MUST follow and in RFC 3264 [3]. Particularly, early-session bodies MUST follow
the offer/answer model and MAY appear in the same messages as session the offer/answer model and MAY appear in the same messages as session
bodies do with the exceptions of 2xx responses for an INVITE and bodies do with the exceptions of 2xx responses for an INVITE and
ACKs. Nevertheless, it is NOT RECOMMENDED to include early offers in ACKs. Nevertheless, it is NOT RECOMMENDED to include early offers in
INVITEs because they can fork, and the UAC could receive multiple INVITEs because they can fork, and the UAC could receive multiple
early answers establishing early media streams at roughly the same early answers establishing early media streams at roughly the same
time. time. It is also NOT RECOMMENDED to use the same transport address
(IP address plus port) in a session body and in an early-session
body. Using different transport addresses (e.g., different ports) to
receive early and regular media makes it easy to detect the start of
the regular media.
If a UA needs to refuse an early-session offer, it MUST to so by If a UA needs to refuse an early-session offer, it MUST to so by
refusing all the media streams in it. When SDP [5] is used, this is refusing all the media streams in it. When SDP [5] is used, this is
done by setting the port number of all the media streams to zero. done by setting the port number of all the media streams to zero.
This is the same mechanism that UACs use to refuse regular offers This is the same mechanism that UACs use to refuse regular offers
that arrive in a response to an empty INVITE. that arrive in a response to an empty INVITE.
An early media session established using early-session bodies MUST be An early media session established using early-session bodies MUST be
terminated when its corresponding early dialog is terminated or it terminated when its corresponding early dialog is terminated or it
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be obtained from the IETF Secretariat. be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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