SIP "cause" URI Parameter for Service Number Translation
RFC 8119

Document Type RFC - Informational (March 2017; No errata)
Updates RFC 4458
Last updated 2017-03-15
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Internet Engineering Task Force (IETF)                         M. Mohali
Request for Comments: 8119                                        Orange
Updates: 4458                                                  M. Barnes
Category: Informational                      MLB@Realtime Communications
ISSN: 2070-1721                                               March 2017

        SIP "cause" URI Parameter for Service Number Translation

Abstract

   RFC 4458 (regarding SIP URIs for applications) defines a "cause" URI
   parameter, which may appear in the Request-URI of a SIP request, that
   is used to indicate a reason why the request arrived to the User
   Agent Server (UAS) receiving the message.  This document updates RFC
   4458 by creating a new predefined value for the "cause" URI parameter
   to cover service number translation for cases of retargeting due to
   specific service action leading to the translation of a called
   service access number.  This document also provides guidance, which
   was missing in RFC 4458, for using the "cause" URI parameter within
   the History-Info header field, since this use is mandatory in some IP
   networks' implementations.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 7841.

   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/rfc8119.

Mohali & Barnes               Informational                     [Page 1]
RFC 8119          Cause for Service Number Translation        March 2017

Copyright Notice

   Copyright (c) 2017 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.  Introduction, Terminology, and Overview . . . . . . . . . . .   2
   2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Guidelines  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Interaction with Request History Information  . . . . . .   4
     3.2.  Handling and Processing the Service Number Translation
           "cause" URI Parameter Value . . . . . . . . . . . . . . .   5
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction, Terminology, and Overview

   [RFC4458] defines a mechanism to identify retargeting due to call
   forwarding supplementary services.  The "cause" URI parameter in the
   target URI identifies the reason for retargeting and has defined
   values equivalent to the TDM (Time Division Multiplexing) Redirecting
   Reasons [ITU-T_Q.763].  The concept of "retargeting" is defined in
   [RFC7044].

   In the Public Switched Telephone Network (PSTN ) / Integrated
   Services Digital Network (ISDN), there is another kind of retargeting
   introduced by the Intelligent Network (IN) services based on a
   translation of the called number as mentioned in [ITU-T_Q.1214].
   Indeed, IN aims to ease the introduction of new services (i.e.,
   Universal Personal Telecommunication (UPT), Virtual Private Network
   (VPN), Freephone, etc.) based on greater flexibility and new

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