A Mechanism for Transporting User-to-User Call Control Information in SIP
RFC 7433

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Internet Engineering Task Force (IETF)                       A. Johnston
Request for Comments: 7433                                         Avaya
Category: Standards Track                                    J. Rafferty
ISSN: 2070-1721                                     Human Communications
                                                            January 2015

   A Mechanism for Transporting User-to-User Call Control Information
                                 in SIP

Abstract

   There is a class of applications that benefit from using SIP to
   exchange User-to-User Information (UUI) data during session
   establishment.  This information, known as call control UUI data, is
   a small piece of data inserted by an application initiating the
   session and utilized by an application accepting the session.  The
   syntax and semantics for the UUI data used by a specific application
   are defined by a UUI package.  This UUI data is opaque to SIP and its
   function is unrelated to any basic SIP function.  This document
   defines a new SIP header field, User-to-User, to transport UUI data,
   along with an extension mechanism.

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/rfc7433.

Johnston & Rafferty          Standards Track                    [Page 1]
RFC 7433                     SIP UUI for CC                 January 2015

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Requirements Discussion . . . . . . . . . . . . . . . . . . .   4
   4.  Normative Definition  . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Syntax for UUI Header Field . . . . . . . . . . . . . . .   6
     4.2.  Hex Encoding Definition . . . . . . . . . . . . . . . . .   7
     4.3.  Source Identity of UUI Data . . . . . . . . . . . . . . .   7
   5.  Guidelines for UUI Packages . . . . . . . . . . . . . . . . .   9
     5.1.  Extensibility . . . . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Registration of User-to-User Header Field . . . . . . . .  11
     6.2.  Registration of User-to-User Header Field Parameters  . .  11
     6.3.  Registration of UUI Packages  . . . . . . . . . . . . . .  11
     6.4.  Registration of UUI Content Parameters  . . . . . . . . .  12
     6.5.  Registration of UUI Encoding Parameters . . . . . . . . .  12
     6.6.  Registration of SIP Option Tag  . . . . . . . . . . . . .  13
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Other Possible Mechanisms  . . . . . . . . . . . . .  17
     A.1.  Why INFO is Not Used  . . . . . . . . . . . . . . . . . .  17
     A.2.  Why Other Protocol Encapsulation UUI Mechanisms Are Not
           Used  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
     A.3.  MIME Body Approach  . . . . . . . . . . . . . . . . . . .  17
     A.4.  URI Parameter . . . . . . . . . . . . . . . . . . . . . .  18
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

Johnston & Rafferty          Standards Track                    [Page 2]
RFC 7433                     SIP UUI for CC                 January 2015

1.  Overview

   This document describes the transport of UUI data using SIP
   [RFC3261].  It defines a mechanism for the transport of general
   application UUI data and for the transport of the call control