Session Initiation Protocol (SIP) URIs for Applications such as Voicemail and Interactive Voice Response (IVR)
RFC 4458

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• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 06

Network Working Group                                        C. Jennings
Request for Comments: 4458                                 Cisco Systems
Category: Informational                                         F. Audet
                                                         Nortel Networks
                                                               J. Elwell
                                                             Siemens plc
                                                              April 2006

        Session Initiation Protocol (SIP) URIs for Applications
         such as Voicemail and Interactive Voice Response (IVR)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Session Initiation Protocol (SIP) is often used to initiate
   connections to applications such as voicemail or interactive voice
   recognition systems.  This specification describes a convention for
   forming SIP service URIs that request particular services based on
   redirecting targets from such applications.

Jennings, et al.             Informational                      [Page 1]
RFC 4458                   SIP Voicemail URI                  April 2006

Table of Contents

   1. Introduction ....................................................3
   2. Mechanism (User Agent Server and Proxy) .........................4
      2.1. Target .....................................................4
      2.2. Cause ......................................................4
      2.3. Retrieving Messages ........................................5
   3. Interaction with Request History Information ....................5
   4. Limitations of Voicemail URI ....................................6
   5. Syntax ..........................................................6
   6. Examples ........................................................7
      6.1. Proxy Forwards Busy to Voicemail ...........................7
      6.2. Endpoint Forwards Busy to Voicemail ........................9
      6.3. Endpoint Forwards Busy to TDM via a Gateway ...............11
      6.4. Endpoint Forwards Busy to Voicemail with History Info .....13
      6.5. Zero Configuration UM System ..............................14
      6.6. Call Coverage .............................................15
   7. IANA Considerations ............................................15
   8. Security Considerations ........................................16
      8.1. Integrity Protection of Forwarding in SIP .................16
      8.2. Privacy Related Issues on the Second Call Leg .............17
   9. Acknowledgements ...............................................18
   10. References ....................................................18
      10.1. Normative References .....................................18
      10.2. Informative References ...................................18

Jennings, et al.             Informational                      [Page 2]
RFC 4458                   SIP Voicemail URI                  April 2006

1.  Introduction

   Many applications such as Unified Messaging (UM) systems and
   Interactive Voice Recognition (IVR) systems have been developed out
   of traditional telephony.  They can be used for storing and
   interacting with voice, video, faxes, email, and instant messaging
   services.  Users often use SIP to initiate communications with these
   applications.  When a SIP call is routed to an application, it is
   necessary that the application be able to obtain several bits of
   information from the session initiation message so that it can
   deliver the desired services.

   For the purpose of this document, we will use UM as the main example,
   but other applications may use the mechanism defined in this
   document.  The UM needs to know what mailbox should be used and
   possible reasons for the type of service desired from the UM.  Many
   voicemail systems provide different greetings depending whether the
   call went to voicemail because the user was busy or because the user
   did not answer.  All of this information can be delivered in existing
   SIP signaling from the call control that retargets the call to the
   UM, but there are no conventions for describing how the desired
   mailbox and the service requested are expressed.  It would be
   possible for every vendor to make this configurable so that any site
   could get it to work; however, this approach is unrealistic for
   achieving interoperability among call control, gateway, and unified
   messaging systems from different vendors.  This specification
   describes a convention for describing this mailbox and service
   information in the SIP URI so that vendors and operators can build
   interoperable systems.