Session Initiation Protocol Service Examples
RFC 5359

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Network Working Group                                   A. Johnston, Ed.
Request for Comments: 5359                                         Avaya
BCP: 144                                                       R. Sparks
Category: Best Current Practice                                  Tekelec
                                                           C. Cunningham
                                                              S. Donovan
                                                           Cisco Systems
                                                              K. Summers
                                                                   Sonus
                                                            October 2008

              Session Initiation Protocol Service Examples

Status of This Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Abstract

   This document gives examples of Session Initiation Protocol (SIP)
   services.  This covers most features offered in so-called IP Centrex
   offerings from local exchange carriers and PBX (Private Branch
   Exchange) features.  Most of the services shown in this document are
   implemented in the SIP user agents, although some require the
   assistance of a SIP proxy.  Some require some extensions to SIP
   including the REFER, SUBSCRIBE, and NOTIFY methods and the Replaces
   and Join header fields.  These features are not intended to be an
   exhaustive set, but rather show implementations of common features
   likely to be implemented on SIP IP telephones in a business
   environment.

Johnston, et al.         Best Current Practice                  [Page 1]
RFC 5359                  SIP Service Examples              October 2008

Table of Contents

   1. Overview ........................................................3
      1.1. Legend for Message Flows ...................................4
   2. Service Examples ................................................6
      2.1. Call Hold ..................................................6
      2.2. Consultation Hold .........................................19
      2.3. Music on Hold .............................................38
      2.4. Transfer - Unattended .....................................50
      2.5. Transfer - Attended .......................................58
      2.6. Transfer - Instant Messaging ..............................71
      2.7. Call Forwarding Unconditional .............................77
      2.8. Call Forwarding - Busy ....................................84
      2.9. Call Forwarding - No Answer ...............................92
      2.10. 3-Way Conference - Third Party Is Added .................101
      2.11. 3-Way Conference - Third Party Joins ....................107
      2.12. Find-Me .................................................113
      2.13. Call Management (Incoming Call Screening) ...............125
      2.14. Call Management (Outgoing Call Screening) ...............132
      2.15. Call Park ...............................................135
      2.16. Call Pickup .............................................147
      2.17. Automatic Redial ........................................154
      2.18. Click to Dial ...........................................163
   3. Security Considerations .......................................166
   4. Acknowledgements ..............................................166
   5. References ....................................................167
      5.1. Normative References .....................................167
      5.2. Informative References ...................................168

Johnston, et al.         Best Current Practice                  [Page 2]
RFC 5359                  SIP Service Examples              October 2008

1.  Overview

   This document provides example call flows detailing a SIP
   implementation of the following traditional telephony services:

           Call Hold                        3-Way Conference
           Consultation Hold                Find-Me
           Music on Hold                    Incoming Call Screening
           Unattended Transfer              Outgoing Call Screening
           Attended Transfer                Call Park
           Instant Messaging Transfer       Call Pickup
           Unconditional Call Forwarding    Automatic Redial
           Call Forwarding on Busy          Click to Dial
           Call Forwarding on No Answer

   Note that the Single Line Extension call flow has been removed from
   this document and will be covered in a separate document.

   The call flows shown in this document were developed in the design of
   a SIP IP communications network.  They represent an example set of
   so-called IP Centrex services or PBX services.

   It is the hope of the authors that this document will be useful for