The Early Session Disposition Type for the Session Initiation Protocol (SIP)
RFC 3959
| Document | Type | RFC - Proposed Standard (December 2004; Errata) | |
|---|---|---|---|
| Author | Gonzalo Camarillo | ||
| Last updated | 2015-10-14 | ||
| Stream | Internent Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 3959 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | rohan@cisco.com, dean.willis@softarmor.com | ||
Network Working Group G. Camarillo
Request for Comments: 3959 Ericsson
Category: Standards Track December 2004
The Early Session Disposition Type for
the Session Initiation Protocol (SIP)
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document defines a new disposition type (early-session) for the
Content-Disposition header field in the Session Initiation Protocol
(SIP). The treatment of "early-session" bodies is similar to the
treatment of "session" bodies. That is, they follow the offer/answer
model. Their only difference is that session descriptions whose
disposition type is "early-session" are used to establish early media
sessions within early dialogs, as opposed to regular sessions within
regular dialogs.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Issues Related to Early Media Session Establishment . . . . . 2
4. The Early Session Disposition Type . . . . . . . . . . . . . . 4
5. Preconditions . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Option tag . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informational References . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 11
Camarillo Standards Track [Page 1]
RFC 3959 Early Session Disposition Type December 2004
1. Introduction
Early media refers to media (e.g., audio and video) that is exchanged
before a particular session is accepted by the called user. Within a
dialog, early media occurs from the moment the initial INVITE is sent
until the User Agent Server (UAS) generates a final response. It may
be unidirectional or bidirectional, and can be generated by the
caller, the callee, or both. Typical examples of early media
generated by the callee are ringing tone and announcements (e.g.,
queuing status). Early media generated by the caller typically
consists of voice commands or dual tone multi-frequency (DTMF) tones
to drive interactive voice response (IVR) systems.
The basic SIP specification (RFC 3261 [2]) only supports very simple
early media mechanisms. These simple mechanisms have a number of
problems related to forking and security, and do not satisfy the
requirements of most applications. RFC 3960 [8] goes beyond the
mechanisms defined in RFC 3261 [2] and describes two models of early
media using SIP: the gateway model and the application server model.
Although both early media models described in RFC 3960 [8] are
superior to the one specified in RFC 3261 [2], the gateway model
still presents a set of issues. In particular, the gateway model
does not work well with forking. Nevertheless, the gateway model is
needed because some SIP entities (in particular, some gateways)
cannot implement the application server model.
The application server model addresses some of the issues present in
the gateway model. This model uses the early-session disposition
type specified in this document.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in BCP 14, RFC 2119 [1] and indicate requirement levels for
compliant implementations.
3. Issues Related to Early Media Session Establishment
Traditionally, early media sessions have been established in the same
way as regular sessions. That is, using an offer/answer exchange
where the disposition type of the session descriptions is "session".
Application servers perform an offer/answer exchange with the User
Agent Client (UAC) to exchange early media exclusively, while UASs
Show full document text