Technical Summary
The Early Session Disposition Type for the Session Initiation Protocol :
This document defines a new disposition type (early-session) for the
Content-Disposition header field in 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.
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 callee generates a final response. It may be unidirectional or
bi-directional, 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 DTMF
tones that drive interactive voice servers.
Early Media and Ringing Tone Generation in the Session Initiation Protocol
This documents describes some models for early media handling.
Working Group Summary
The design choice of using an early-session Content-Disposition
header field to parallel the session header field was not contentious.
The working group had a very long process of coming to consensus
on early media handling, given that there are real requirements for
it, but potential abuses as well. The Informational document's models
summarize the consensus that the group could reach.
Protocol Quality
Allison Mankin reviewed the documents for the IESG.
RFC Editor Notes:
In both documents:
Expand the first appearance of UAC to User Agent Client (UAC),
the first appearance of UAC to User Agent Server (UAS), and the
first appearance of UA to User Agent (UA).
Expand first instance of SRTP to Secure Realtime Transport Protocol (SRTP)
Expand first instance of STUN to Simple Traversal of the UDP Protocol through
NAT (STUN)
In draft-ietf-sipping-early-disposition:
Expand the first instance of PSTN to Public Switched Telephone Network
(PSTN)
Expand PIN to Personal Identification Number (PIN)
Expand GUI to Graphical User Interface (GUI)
In draft-ietf-sipping-early-media:
Expand ICE to Interactive Connectivity Establishment (ICE)
Expand SRTP to Secure Realtime Transport Protocol (SRTP)
OLD:
or DTMF tones to drive IVRs
NEW:
or dual tone multi-frequency (DTMF) tone to drive interactive
voice response (IVR) systems
OLD:
A POTS-like SIP UA
NEW:
A POTS ("Plain Old Telephone Service")-like SIP User Agent (UA)
OLD:
3G IMS
NEW:
3GPP IMS (Third Generation Partnership Project Internet
Multimedia System)