Shared Appearances of a Session Initiation Protocol (SIP) Address of Record (AOR)
RFC 7463

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Internet Engineering Task Force (IETF)                  A. Johnston, Ed.
Request for Comments: 7463                                         Avaya
Updates: 3261, 4235                                 M. Soroushnejad, Ed.
Category: Standards Track                              V. Venkataramanan
ISSN: 2070-1721                                   Sylantro Systems Corp.
                                                              March 2015

       Shared Appearances of a Session Initiation Protocol (SIP)
                        Address of Record (AOR)

Abstract

   This document describes the requirements and implementation of a
   group telephony feature commonly known as Bridged Line Appearance
   (BLA) or Multiple Line Appearance (MLA), or Shared Call/Line
   Appearance (SCA).  When implemented using the Session Initiation
   Protocol (SIP), it is referred to as shared appearances of an Address
   of Record (AOR) since SIP does not have the concept of lines.  This
   feature is commonly offered in IP Centrex services and IP Private
   Branch Exchange (IPBX) offerings and is likely to be implemented on
   SIP IP telephones and SIP feature servers used in a business
   environment.  This feature allows several user agents (UAs) to share
   a common AOR, learn about calls placed and received by other UAs in
   the group, and pick up or join calls within the group.  This document
   discusses use cases, lists requirements, and defines extensions to
   implement this feature.  This specification updates RFCs 3261 and
   4235.

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/rfc7463.

Copyright Notice

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

Johnston, et al.             Standards Track                    [Page 1]
RFC 7463                 SIP Shared Appearances               March 2015

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   5
   3.  Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Executive/Assistant Arrangement . . . . . . . . . . . . .   5
     3.2.  Call Group  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Single Line Extension . . . . . . . . . . . . . . . . . .   6
     3.4.  Changing UAs  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Requirements and Implementation . . . . . . . . . . . . . . .   6
     4.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Implementation  . . . . . . . . . . . . . . . . . . . . .   8
   5.  Normative Description . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Elements  . . . . . . . . . . . . . . . . . . . . . . . .  11
     5.2.  Shared Appearance Dialog Package Extensions . . . . . . .  11
       5.2.1.  The <appearance> Element  . . . . . . . . . . . . . .  11
       5.2.2.  The <exclusive> Element . . . . . . . . . . . . . . .  12
       5.2.3.  The <joined-dialog> Element . . . . . . . . . . . . .  12
       5.2.4.  The <replaced-dialog> Element . . . . . . . . . . . .  13
     5.3.  Shared Appearance User Agents . . . . . . . . . . . . . .  13