Session Description Protocol (SDP) Extension for Setting Audio and Video Media Streams over Circuit-Switched Bearers in the Public Switched Telephone Network (PSTN)
RFC 7195
Internet Engineering Task Force (IETF) M. Garcia-Martin
Request for Comments: 7195 Ericsson
Category: Standards Track S. Veikkolainen
ISSN: 2070-1721 Nokia
May 2014
Session Description Protocol (SDP) Extension for
Setting Audio and Video Media Streams over Circuit-Switched Bearers in
the Public Switched Telephone Network (PSTN)
Abstract
This memo describes use cases, requirements, and protocol extensions
for using the Session Description Protocol (SDP) offer/answer model
for establishing audio and video media streams over circuit-switched
bearers in the Public Switched Telephone Network (PSTN).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7195.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Garcia-Martin & Veikkolainen Standards Track [Page 1]
RFC 7195 PSTN Circuit-Switched Bearers in SDP May 2014
Table of Contents
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................4
3. Requirements ....................................................5
4. Overview of Operation ...........................................5
4.1. Example Call Flow ..........................................6
5. Protocol Description ............................................7
5.1. Level of Compliance ........................................7
5.2. Extensions to SDP ..........................................7
5.2.1. Connection Data .....................................7
5.2.2. Media Descriptions ..................................9
5.2.3. Correlating the PSTN Circuit-Switched
Bearer with SDP ....................................10
5.2.3.1. The "cs-correlation" Attribute ............11
5.2.3.2. Caller ID Correlation Mechanism ...........12
5.2.3.3. User-User Information Element
Correlation Mechanism .....................13
5.2.3.4. DTMF Correlation Mechanism ................14
5.2.3.5. External Correlation Mechanism ............15
5.2.3.6. Extensions to Correlation Mechanisms ......16
5.3. Negotiating the Correlation Mechanisms ....................17
5.3.1. Determining the Direction of the
Circuit-Switched Bearer Setup ......................17
5.3.2. Populating the "cs-correlation" Attribute ..........18
5.3.3. Considerations for Correlations ....................18
5.4. Considerations for Usage of Existing SDP ..................19
5.4.1. Originator of the Session ..........................19
5.4.2. Contact Information ................................20
5.5. Considerations for Usage of Third Party Call
Control (3PCC) ............................................20
5.6. Offer/Answer Mode Extensions ..............................20
5.6.1. Generating the Initial Offer .......................21
5.6.2. Generating the Answer ..............................23
5.6.3. Offerer Processing the Answer ......................26
5.6.4. Modifying the Session ..............................27
5.7. Formal Syntax .............................................28
6. Examples .......................................................30
6.1. Single PSTN Audio Stream ..................................30
6.2. Advanced SDP Example: Circuit-Switched Audio and
Video Streams .............................................32
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