[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 5359

SIPPING Working Group                                   A. Johnston, Ed.
Internet-Draft                                                     Avaya
Expires: July 27, 2007                                         R. Sparks
                                                        Estacado Systems
                                                           C. Cunningham
                                                              S. Donovan
                                                           Cisco Systems
                                                              K. Summers
                                                          Prodea Systems
                                                        January 23, 2007


              Session Initiation Protocol Service Examples
                 draft-ietf-sipping-service-examples-12

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on July 27, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document gives examples of Session Initiation Protocol (SIP)
   services.  This covers most features offered in so-called IP Centrex



Johnston, et al.          Expires July 27, 2007                 [Page 1]

Internet-Draft            SIP Service Examples              January 2007


   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.


Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Service Examples  . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Call Hold . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.2.  Consultation Hold . . . . . . . . . . . . . . . . . . . .  17
     2.3.  Music On Hold . . . . . . . . . . . . . . . . . . . . . .  35
     2.4.  Transfer - Unattended . . . . . . . . . . . . . . . . . .  48
     2.5.  Transfer - Attended . . . . . . . . . . . . . . . . . . .  55
     2.6.  Transfer - Instant Messaging  . . . . . . . . . . . . . .  68
     2.7.  Call Forwarding Unconditional . . . . . . . . . . . . . .  74
     2.8.  Call Forwarding - Busy  . . . . . . . . . . . . . . . . .  80
     2.9.  Call Forwarding - No Answer . . . . . . . . . . . . . . .  88
     2.10. 3-way Conference - Third Party is Added . . . . . . . . .  97
     2.11. 3-way Conference - Third Party Joins  . . . . . . . . . . 103
     2.12. Find-Me . . . . . . . . . . . . . . . . . . . . . . . . . 108
     2.13. Call Management (Incoming Call Screening) . . . . . . . . 120
     2.14. Call Management (Outgoing Call Screening) . . . . . . . . 128
     2.15. Call Park . . . . . . . . . . . . . . . . . . . . . . . . 131
     2.16. Call Pickup . . . . . . . . . . . . . . . . . . . . . . . 141
     2.17. Automatic Redial  . . . . . . . . . . . . . . . . . . . . 147
     2.18. Click to Dial . . . . . . . . . . . . . . . . . . . . . . 156
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . 159
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 160
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 160
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 160
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . 160
     6.2.  Informative References  . . . . . . . . . . . . . . . . . 162
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 162
   Intellectual Property and Copyright Statements  . . . . . . . . . 164










Johnston, et al.          Expires July 27, 2007                 [Page 2]

Internet-Draft            SIP Service Examples              January 2007


1.  Overview

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

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

   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
   SIP implementers, designers, and protocol researchers alike and will
   help further the goal of a standard implementation of RFC 3261 [2]
   and some of its extensions.

   These flows represent carefully checked and working group reviewed
   scenarios of SIP service examples as a companion to the
   specifications.

   These call flows are based on the current version 2.0 of SIP in RFC
   3261 [2] with SDP usage described in RFC 3264 [5] Other RFCs also
   form part of the SIP standard and are used and referenced in these
   call flows.

   The SIP specification and the other referenced documents are
   definitive as far as protocol issues are concerned.  Also, these
   flows do not represent the only way to implement these services -
   other approaches such as 3pcc (Third Party Call Control) [19] or
   Back-to-Back User Agents (B2BUA) may be more appropriate in some
   circumstances.  The peer-to-peer design and principles of these
   service examples are described in the Multiparty Framework document
   [12].

   These flows assume the functionality described in the SIP Call Flow
   Examples document [18], which explores basic SIP behavior.  Some of
   the scenarios described herein make use of the SIP method extension
   REFER [3] and the SIP header extension Replaces [4], and the SIP



Johnston, et al.          Expires July 27, 2007                 [Page 3]

Internet-Draft            SIP Service Examples              January 2007


   header extension Join [9].  The SIP Events document [6] describes the
   use of SUBSCRIBE and NOTIFY while the SIP Dialog Event Package [8]
   document describes the dialog event package.  Some examples make use
   of the GRUU (Globally Routable User Agent URI) [22] extension.

   These flows were prepared assuming a network of proxies, registrars,
   and other SIP servers.  The use of Secure SIP URIs (sips) is shown
   throughout this document, implying TLS transport on each hop with
   assumed certificate validation.  However, other security approaches
   can be used.  The use of Digest authentication is shown in some
   examples.

   The emphasis in these call flows is the SIP signaling exchange.  As a
   result, only very simple SDP offer/answer exchanges are shown with
   audio media.  These flows apply equally well for other media and
   multi-media sessions.  For more advanced examples of SDP offer/answer
   exchanges, refer to [23].

   Each call flow is presented with a textual description of the
   scenario, a message flow diagram showing the messages exchanged
   between separate network elements, and the detailed contents of each
   message shown in the diagram.

   1.1 Legend for Message Flows

   Dashed lines (---) represent control messages that are mandatory to
   the call scenario.  These control messages can be SIP signaling.

   Double dashed lines (===) represent media paths between network
   elements.

   Messages with parenthesis around name represent optional control
   messages.

   Messages are identified in the Figures as F1, F2, etc.  This
   references the message details in the table that follows the Figure.

   Lines longer than 72 characters are handled using the <allOneLine>
   convention defined in Section 2.1 of RFC 4475 [17].

   Comments in the message details are shown in the following form:

   /* Comments. */


2.  Service Examples

2.1.  Call Hold



Johnston, et al.          Expires July 27, 2007                 [Page 4]

Internet-Draft            SIP Service Examples              January 2007


            Alice           Proxy            Bob
             |                |              |
             |    INVITE F1   |              |
             |--------------->|              |
             |                |   INVITE F2  |
             |(100 Trying) F3 |------------->|
             |<---------------|              |
             |                |180 Ringing F4|
             | 180 Ringing F5 |<-------------|
             |<---------------|              |
             |                |  200 OK F6   |
             |    200 OK F7   |<-------------|
             |<---------------|              |
             |     ACK F8     |              |
             |--------------->|    ACK F9    |
             |                |------------->|
             |    Both way RTP Established   |
             |<=============================>|
             |                |INVITE(hold) F10
             |INVITE(hold) F11|<-------------|
             |<---------------|              |
             |    200 OK F12  |              |
             |--------------->|   200 OK F13 |
             |                |------------->|
             |                |     ACK F14  |
             |     ACK F15    |<-------------|
             |<---------------|              |
             |           No RTP Sent!        |
             |                |  INVITE F16  |
             |   INVITE F17   |<-------------|
             |<---------------|              |
             |   200 OK F18   |              |
             |--------------->|  200 OK F19  |
             |                |------------->|
             |                |    ACK F20   |
             |     ACK F21    |<-------------|
             |<---------------|              |
             |    Both way RTP Established   |
             |<=============================>|
             |     BYE F22    |              |
             |--------------->|   BYE F23    |
             |                |------------->|
             |                |   200 OK F24 |
             |    200 OK F25  |<-------------|
             |<---------------|              |
             |                |              |

   In this scenario, Alice calls Bob, then Bob places the call on hold.



Johnston, et al.          Expires July 27, 2007                 [Page 5]

Internet-Draft            SIP Service Examples              January 2007


   Bob then takes the call off hold, then Alice hangs up the call.  Note
   that hold is unidirectional in nature.  However, a UA that places the
   other party on hold will generally also stop sending media, resulting
   in no media exchange between the UAs.  Older UAs may set the
   connection address to 0.0.0.0 when initiating hold.  However, this
   behavior has been deprecated in favor of using the a=sendonly SDP
   attribute.

   Also note the use of the rendering feature tag defined in RFC 4235
   [8] used in F10 and F11 to indicate in that Bob's UA is no longer
   rendering media to Bob, i.e. that Bob has placed the call on hold.

   Message Details


      F1 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 INVITE Proxy 1 -> Bob

      INVITE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103



Johnston, et al.          Expires July 27, 2007                 [Page 6]

Internet-Draft            SIP Service Examples              January 2007


      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F3 (100 Trying) Proxy 1 -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F4 180 Ringing Bob -> Proxy 1

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE



Johnston, et al.          Expires July 27, 2007                 [Page 7]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:bob@client.biloxi.example.com>
      Content Length:0


      F5 180 Ringing Proxy 1 -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content Length: 0


      F6 200 OK Bob -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000





Johnston, et al.          Expires July 27, 2007                 [Page 8]

Internet-Draft            SIP Service Examples              January 2007


      F7 200 OK Proxy 1 -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 ACK Alice -> Proxy 1

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf92
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F9 ACK Proxy 1 -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837492.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061



Johnston, et al.          Expires July 27, 2007                 [Page 9]

Internet-Draft            SIP Service Examples              January 2007


       ;branch=z9hG4bK74bf92
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Bob places Alice on hold.  Note that the version is
         incremented in the o= field of the SDP  */

      F10 INVITE Bob -> Proxy 1

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F11 INVITE Proxy 1 -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0

      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1



Johnston, et al.          Expires July 27, 2007                [Page 10]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      /* Alice replies to hold */

      F12 200 OK Alice -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0



Johnston, et al.          Expires July 27, 2007                [Page 11]

Internet-Draft            SIP Service Examples              January 2007


      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F13 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F14 ACK Bob -> Proxy 1

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds72
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY



Johnston, et al.          Expires July 27, 2007                [Page 12]

Internet-Draft            SIP Service Examples              January 2007


      Supported: replaces
      Content-Length: 0


      F15 ACK Proxy 1 -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds72
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /*   Bob takes the call off hold */

      F16 INVITE Bob -> Proxy 1

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds73
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000



Johnston, et al.          Expires July 27, 2007                [Page 13]

Internet-Draft            SIP Service Examples              January 2007


      F17 INVITE Proxy 1 -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837493.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds73
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F18 200 OK Alice -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837493.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds73
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...



Johnston, et al.          Expires July 27, 2007                [Page 14]

Internet-Draft            SIP Service Examples              January 2007


      v=0
      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F19 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds73
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F20 ACK Bob -> Proxy 1

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds74
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces



Johnston, et al.          Expires July 27, 2007                [Page 15]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: 0


      F21 ACK Proxy 1 -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837494.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds74
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* RTP Media stream re-established.   Alice disconnects. */

      F22 BYE Alice -> Proxy 1

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf97
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F23 BYE Proxy 1 -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837497.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf97
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159



Johnston, et al.          Expires July 27, 2007                [Page 16]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F24 200 OK Bob -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837497.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf97
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F25 200 OK Proxy 1 -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf97
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0

2.2.  Consultation Hold

           Alice            Proxy           Bob                Carol
             |                |              |                   |
             |    INVITE F1   |              |                   |
             |--------------->|   INVITE F2  |                   |
             |                |------------->|                   |
             |(100 Trying) F3 |              |                   |
             |<---------------|180 Ringing F4|                   |
             |                |<-------------|                   |
             | 180 Ringing F5 |              |                   |
             |<---------------|  200 OK F6   |                   |
             |                |<-------------|                   |
             |    200 OK F7   |              |                   |
             |<---------------|              |                   |



Johnston, et al.          Expires July 27, 2007                [Page 17]

Internet-Draft            SIP Service Examples              January 2007


             |     ACK F8     |              |                   |
             |--------------->|     ACK F9   |                   |
             |                |------------->|                   |
             |     Both way RTP Established  |                   |
             |<=============================>|                   |
             |                |INVITE(hold) F10                  |
             |INVITE(hold) F11|<-------------|                   |
             |<---------------|              |                   |
             |    200 OK F12  |              |                   |
             |--------------->|   200 OK F13 |                   |
             |                |------------->|                   |
             |                |     ACK F14  |                   |
             |                |<-------------|                   |
             |    ACK F15     |              |                   |
             |<---------------|              |                   |
             |         No RTP Sent!          |                   |
             |                |   INVITE F16 |                   |
             |                |<-------------|                   |
             |                |              |    INVITE F17     |
             |                |--------------------------------->|
             |                |(100 Trying) F18                  |
             |                |------------->|                   |
             |                |              | 180 Ringing F19   |
             |                |<---------------------------------|
             |                | 180 Ringing F20                  |
             |                |------------->|                   |
             |                |              |    200 OK F21     |
             |                |<---------------------------------|
             |                |   200 OK F22 |                   |
             |                |------------->|                   |
             |                |    ACK F23   |                   |
             |                |<-------------|                   |
             |                |              |      ACK F24      |
             |                |--------------------------------->|
             |                |         Both way RTP Established |
             |                |              |<=================>|
             |                |   BYE F25    |                   |
             |                |<-------------|                   |
             |                |              |       BYE F26     |
             |                |--------------------------------->|
             |                |              |    200 OK F27     |
             |                |<---------------------------------|
             |                |   200 OK F28 |                   |
             |                |------------->|                   |
             |                |   INVITE F29 |                   |
             |    INVITE F30  |<-------------|                   |
             |<---------------|              |                   |
             |    200 OK F31  |              |                   |



Johnston, et al.          Expires July 27, 2007                [Page 18]

Internet-Draft            SIP Service Examples              January 2007


             |--------------->|   200 OK F32 |                   |
             |                |------------->|                   |
             |                |     ACK F33  |                   |
             |                |<-------------|                   |
             |    ACK F34     |              |                   |
             |<---------------|              |                   |
             |     Both way RTP Established  |                   |
             |<=============================>|                   |
             |    BYE F35     |              |                   |
             |--------------->|    BYE F36   |                   |
             |                |------------->|                   |
             |                |   200 OK F37 |                   |
             |                |<-------------|                   |
             |  200 OK F38    |              |                   |
             |<---------------|              |                   |
             |                |              |                   |

   In this scenario, Alice calls Bob. Bob places call on hold.  Bob
   calls Carol.  Bob then disconnects with Carol, then takes the call
   with Alice off hold.  The call ends when Alice hangs up.

   Also note the use of the rendering feature tag defined in RFC 4235
   [8] used in F10 to indicate in that Bob's UA is no longer rendering
   media to Bob, i.e. that Bob has placed the call on hold.

   Message Details


      F1 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com



Johnston, et al.          Expires July 27, 2007                [Page 19]

Internet-Draft            SIP Service Examples              January 2007


      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 INVITE Proxy 1 -> Bob

      INVITE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F3(100 Trying) Proxy 1 -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F4 180 Ringing Bob -> Proxy 1



Johnston, et al.          Expires July 27, 2007                [Page 20]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content Length:0


      F5 180 Ringing Proxy 1 -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content Length: 0


      F6 200 OK Bob -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces



Johnston, et al.          Expires July 27, 2007                [Page 21]

Internet-Draft            SIP Service Examples              January 2007


      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F7 200 OK Proxy 1 -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 ACK Alice -> Proxy 1

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf45
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com



Johnston, et al.          Expires July 27, 2007                [Page 22]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F9 ACK Proxy 1 -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837494.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf45
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Bob places  Alice on hold. */

      F10 INVITE Bob -> Proxy 1

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0



Johnston, et al.          Expires July 27, 2007                [Page 23]

Internet-Draft            SIP Service Examples              January 2007


      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F11 INVITE Proxy 1 -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837497.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F12 200 OK Alice -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837497.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com



Johnston, et al.          Expires July 27, 2007                [Page 24]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F13 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F14 ACK Bob -> Proxy 1

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061



Johnston, et al.          Expires July 27, 2007                [Page 25]

Internet-Draft            SIP Service Examples              January 2007


       ;branch=z9hG4bKnashdsg
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F15 ACK Proxy 1 -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8374.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdsg
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F16 INVITE Bob -> Proxy 1

      INVITE sips:carol@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com



Johnston, et al.          Expires July 27, 2007                [Page 26]

Internet-Draft            SIP Service Examples              January 2007


      t=0 0
      m=audio 50170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F17 INVITE Proxy 1 -> Carol

      INVITE sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749a.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 50170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F18 (100 Trying) Proxy 1 -> Bob

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F19 180 Ringing Carol -> Proxy 1



Johnston, et al.          Expires July 27, 2007                [Page 27]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749a.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Content Length:0


      F20 180 Ringing Proxy 1 -> Bob

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=client.chicago.example.com
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Content Length: 0


      F21 200 OK Carol -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749a.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces



Johnston, et al.          Expires July 27, 2007                [Page 28]

Internet-Draft            SIP Service Examples              January 2007


      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F22 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds22
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F23 ACK Bob -> Proxy 1

      ACK sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds24
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com



Johnston, et al.          Expires July 27, 2007                [Page 29]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F24 ACK Proxy 1 -> Carol

      ACK sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749b.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds24
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F25 BYE Bob -> Proxy 1

      BYE sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7j
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F26 BYE Proxy 1 -> Carol

      BYE sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749k.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7j
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309



Johnston, et al.          Expires July 27, 2007                [Page 30]

Internet-Draft            SIP Service Examples              January 2007


      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F27 200 OK Carol -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749k.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7j
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F28 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7j
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=456654
      Call-ID: 9876543210@biloxi.example.com
      CSeq: 2 BYE
      Content-Length: 0


      /* Bob takes the call off hold */

      F29 INVITE Bob -> Proxy 1

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7b
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE



Johnston, et al.          Expires July 27, 2007                [Page 31]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:bob@client.biloxi.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F30 INVITE Proxy 1 -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749q.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7b
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F31 200 OK Alice -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749q.1
       ;received=192.0.2.54



Johnston, et al.          Expires July 27, 2007                [Page 32]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7b
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F32 200 OK Proxy 1 -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7b
       ;received=192.0.2.105
      Record-Route: <sips:ss1.example.com;lr>
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000




Johnston, et al.          Expires July 27, 2007                [Page 33]

Internet-Draft            SIP Service Examples              January 2007


      F33 ACK Bob -> Proxy 1

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7d7
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F34 ACK Proxy 1 -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8374.1
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7d7
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F35 BYE Alice -> Proxy 1

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf10
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0





Johnston, et al.          Expires July 27, 2007                [Page 34]

Internet-Draft            SIP Service Examples              January 2007


      F36 BYE Proxy 1 -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8379.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf10
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F37 200 OK Bob -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8379.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf10
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F38 200 OK Proxy 1 -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf10
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0

2.3.  Music On Hold


           Alice             Bob       Music Server



Johnston, et al.          Expires July 27, 2007                [Page 35]

Internet-Draft            SIP Service Examples              January 2007


             |                |              |
             |    INVITE F1   |              |
             |--------------->|              |
             | 180 Ringing F2 |              |
             |<---------------|              |
             |    200 OK F3   |              |
             |<---------------|              |
             |     ACK F4     |              |
             |--------------->|              |
             |       RTP      |              |
             |<==============>|              |
             |                |              |
             |   Bob places Alice on hold    |
             |                |              |
             | INVITE (hold) F5              |
             |<---------------|              |
             |    200 OK F6   |              |
             |--------------->|              |
             |     ACK F7     |              |
             |<---------------|              |
             |    no RTP      |              |
             |                |              |
             |  Bob initiates music on hold  |
             |                |              |
             |                |   REFER Refer-To: A F8
             |                |------------->|
             |                |    202 F9    |
             |                |<-------------|
             |                |   NOTIFY F10 |
             |                |<-------------|
             |                |    200 F11   |
             |                |------------->|
             |  INVITE F12 Replaces: B       |
             |<------------------------------|
             |          200 OK F13           |
             |------------------------------>|
             |           ACK F14             |
             |<------------------------------|
             |           RTP Music           |
             |<==============================|
             |     BYE F15    |              |
             |--------------->|  NOTIFY F17  |
             |  200 OK F16    |<-------------|
             |<---------------|  200 OK F18  |
             |                |------------->|
             |                |              |
             | The music on hold is complete |
             |                |              |



Johnston, et al.          Expires July 27, 2007                [Page 36]

Internet-Draft            SIP Service Examples              January 2007


             |    Bob takes Alice off hold   |
             |                |              |
             |  INVITE Replaces: M F19       |
             |<---------------|              |
             |    200 OK F20  |              |
             |--------------->|              |
             |     ACK F21    |              |
             |<---------------|              |
             |       RTP      |              |
             |<==============>|              |
             |            BYE F22            |
             |------------------------------>|
             |          200 OK F23           |
             |<------------------------------|


   In this flow, Bob places Alice on hold with music.  This is performed
   by Bob sending a REFER to a Music Server which sends an INVITE with
   Replaces to Alice.  The Music Server then sends RTP music to Alice.
   Bob picks the call up from hold by sending an INVITE with Replaces to
   Alice.

   Note the use of the rendering feature tag defined in RFC 4235 [8]
   used in F5 to indicate in that Bob's UA is no longer rendering media
   to Bob, i.e. that Bob has placed the call on hold.  Feature tags are
   also used in F12 with the automaton (defined in RFC 3840 [10]) and
   byeless feature tags (defined in RFC 4235 [8]) to describe the
   capabilities of the Music Server.

   Should Alice not wish to receive music on hold, her UA could refuse
   F12 and she will remain on hold with Bob, but in silence.

   Message Details



      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY



Johnston, et al.          Expires July 27, 2007                [Page 37]

Internet-Draft            SIP Service Examples              January 2007


      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0



Johnston, et al.          Expires July 27, 2007                [Page 38]

Internet-Draft            SIP Service Examples              January 2007


      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Alice -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfd
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Bob places Alice on hold */

      F5 INVITE Bob -> Alice

      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bK874bk
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 712 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F6 200 OK Alice -> Bob




Johnston, et al.          Expires July 27, 2007                [Page 39]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bK874bk
       ;received=192.0.2.105
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 712 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F7 ACK Bob -> Alice

      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKq874b
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 712 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


   /*   Bob REFERs Music Server to establish session with Alice
           which replaces the established session between
           Alice and Bob. */

      F8 REFER Bob -> Music Server

      REFER sips:music@server.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds9
      Max-Forwards: 70



Johnston, et al.          Expires July 27, 2007                [Page 40]

Internet-Draft            SIP Service Examples              January 2007


      From: Bob <sips:bob@biloxi.example.com>;tag=02134
      To: Music Server <sips:music@server.example.com>
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 REFER
    <allOneLine>
      Refer-To: <sips:a8342043f@atlanta.example.com;gr?Replaces=
      12345600%40atlanta.example.com%3Bfrom-tag%3D23431
      %3Bto-tag%3D1234567&Require=replaces>
    </allOneLine>
      Referred-By: <sips:bob@biloxi.example.com>
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F9 202 Accepted Music Server -> Bob

      SIP/2.0 202 Accepted
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds9
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=02134
      To: Music Server <sips:music@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      Contact: <sips:music@server.example.com>
      CSeq: 1 REFER
      Content-Length: 0


      F10 NOTIFY Music Server -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bT6
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      Max-Forwards: 70
      From: Music Server <sips:music@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 NOTIFY
      Event: refer
      Subscription-State: active;expires=60
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 100 Trying


      F11 200 OK Bob -> Music Server




Johnston, et al.          Expires July 27, 2007                [Page 41]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bT6
       ;received=192.0.2.103
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      From: Music Server <sips:music@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 NOTIFY
      Content-Length: 0


      /* Music Server places call to Alice to replace session
         between Alice and Bob. */

      F12 INVITE Music Server -> Alice

      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
      Max-Forwards: 70
      From: <sips:music@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Referred-By: <sips:bob@biloxi.example.com>
      Contact: <sips:music@server.example.com>;automaton
       ;+sip.byeless;+sip.rendering="no"
      Require: replaces
      Replaces: 12345600@atlanta.example.com
       ;from-tag=23431;to-tag=1234567
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=MusicServer 2890844576 2890844576 IN IP4 server.example.com
      s=
      c=IN IP4 server.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F13 200 OK Alice -> Music Server

      SIP/2.0 200 OK



Johnston, et al.          Expires July 27, 2007                [Page 42]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
       ;received=192.0.2.103
      From: <sips:music@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly


      F14 ACK Music Server -> Alice

      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK7rfF
      Max-Forwards: 70
      From: <sips:music@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F15 BYE Alice -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0




Johnston, et al.          Expires July 27, 2007                [Page 43]

Internet-Draft            SIP Service Examples              January 2007


      F16 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      /*   Music Server reports success back to Bob by returning
           a 200 OK response.  Bob obtains the dialog identifiers
           from the headers included in the response. */

      F17 NOTIFY Music Server -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bf9
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      Max-Forwards: 70
      From: Music Server <sips:music@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 2 NOTIFY
      Event: refer
      Subscription-State: terminated;reason=noresource
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
       ;received=192.0.2.103
      From: <sips:music@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>


      F18 200 OK Bob -> Music Server

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bf9



Johnston, et al.          Expires July 27, 2007                [Page 44]

Internet-Draft            SIP Service Examples              January 2007


       ;received=192.0.2.103
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      From: Music Server <sips:music@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 2 NOTIFY
      Content-Length: 0


      /*  Alice is now parked at the Music Server */

      /* Bob picks up the call by sending an INVITE to Alice who
         replaces the existing session with the Music Server.   */


      F19 INVITE Bob -> Alice

      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bK74bf9
      From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr
      To: Alice <sips:a8342043f@atlanta.example.com;gr>
      Call-ID: uioewrjk2k2were
      CSeq: 42121 INVITE
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
       SUBSCRIBE, NOTIFY
      Replaces: a5-75-34-12-76@server.example.com
       ;to-tag=098594;from-tag=0111
      Contact: <sips:bob@client.biloxi.example.com>
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844631 2890844631 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendrecv


      F20 200 OK Alice -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.105



Johnston, et al.          Expires July 27, 2007                [Page 45]

Internet-Draft            SIP Service Examples              January 2007


      From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr
      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=6654323
      Call-ID: uioewrjk2k2were
      CSeq: 42121 INVITE
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
       SUBSCRIBE, NOTIFY
      Contact: <sips:alice@client.atlanta.example.com>
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844576 2890844576 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendrecv


      F21 200 ACK Bob -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKj974bf9
      From: Bob <sips:bob@biloxi.example.com>;tag=4i323pr
      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=6654323
      Call-ID: uioewrjk2k2were
      CSeq: 42121 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
       SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Length: 0


      F22 BYE Alice -> Music Server

      BYE sips:music@server.example.com SIP/2.0
      Max-Forwards: 70
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74rf
      To: <sips:music@server.example.com>;tag=0111
      From: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 15 BYE
      Content-Length: 0




Johnston, et al.          Expires July 27, 2007                [Page 46]

Internet-Draft            SIP Service Examples              January 2007


      F23 200 OK Music Server -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74rf
       ;received=192.0.2.103
      To: <sips:music@server.example.com>;tag=0111
      From: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 15 BYE
      Content-Length: 0


      /* Normal media session between Alice and Bob is resumed */





































Johnston, et al.          Expires July 27, 2007                [Page 47]

Internet-Draft            SIP Service Examples              January 2007


2.4.  Transfer - Unattended


          Alice                 Bob                 Carol
            |      INVITE F1     |                    |
            |<-------------------|                    |
            |   180 Ringing F2   |                    |
            |------------------->|                    |
            |      200 OK F3     |                    |
            |------------------->|                    |
            |        ACK F4      |                    |
            |<-------------------|                    |
            |        RTP         |                    |
            |<==================>|                    |
            |                    |                    |
            |  Alice performs unattended transfer     |
            |                    |                    |
            | REFER Refer-To:C F5|                    |
            |------------------->|                    |
            |  202 Accepted F6   |                    |
            |<-------------------|                    |
            |      NOTIFY F7     |                    |
            |<-------------------|                    |
            |      200 OK F8     |                    |
            |------------------->|                    |
            |       BYE F9       |                    |
            |------------------->|                    |
            |     200 OK F10     |                    |
            |<-------------------|                    |
            |   No RTP Session   | INVITE Referred-By: A F11
            |                    |------------------->|
            |                    |   180 Ringing F12  |
            |                    |<-------------------|
            |                    |     200 OK F13     |
            |                    |<-------------------|
            |                    |       ACK F14      |
            |                    |------------------->|
            |                    |        RTP         |
            |                    |<==================>|
            |      NOTIFY F15    |                    |
            |<-------------------|                    |
            |      200 OK F16    |                    |
            |------------------->|                    |
            |                    |                    |

   In this scenario, Bob calls Alice.  Alice then transfers Bob to
   Carol, then Alice disconnects with Bob. Bob establishes the session
   to Carol then reports the success back to Alice in the NOTIFY in F15.



Johnston, et al.          Expires July 27, 2007                [Page 48]

Internet-Draft            SIP Service Examples              January 2007


   If the transfer fails, Bob can send a new INVITE back to Alice to re-
   establish the session.

   Despite the BYE sent by Alice in F9, the dialog between Alice and Bob
   still exists until the subscription created by the REFER has
   terminated (either due to a NOTIFY containing a Subscription-State:
   terminated;reason=noresource header field, as in F15, or a 481
   response to a NOTIFY).

   For more about call transfer see the transfer [7] document.

   Message Details


      F1 INVITE Bob -> Alice

      INVITE sips:alice@atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Alice -> Bob

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com



Johnston, et al.          Expires July 27, 2007                [Page 49]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Length: 0


      F3 200 OK Alice -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Bob -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds2
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Session is established between Alice and Bob. */

      /* Alice performs unattended transfer of Bob to Carol */



Johnston, et al.          Expires July 27, 2007                [Page 50]

Internet-Draft            SIP Service Examples              January 2007


      F5 REFER Alice -> Bob

      REFER sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds8
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 101 REFER
      Refer-To: <sips:carol@chicago.example.com>
      Referred-By: <alice@atlanta.example.com>
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Length: 0


      F6 202 Accepted Bob -> Alice

      SIP/2.0 202 Accepted
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds8
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      Contact: <sips:bob@client.biloxi.example.com>
      CSeq: 101 REFER
      Content-Length: 0


      F7 NOTIFY Bob -> Alice

      NOTIFY sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds32
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 NOTIFY
      Event: refer
      Subscription-State: active;expires=60
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 100 Trying





Johnston, et al.          Expires July 27, 2007                [Page 51]

Internet-Draft            SIP Service Examples              January 2007


      F8 200 OK Alice -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds32
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 NOTIFY
      Content-Length: 0


      /* Alice now disconnects with Bob. */

      F9 BYE Alice -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds43
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 102 BYE
      Content-Length: 0


      F10 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds43
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 102 BYE
      Content-Length: 0


      /* Bob attempts the transfer to Carol */

      F11 INVITE Bob -> Carol

      INVITE sips:carol@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds1



Johnston, et al.          Expires July 27, 2007                [Page 52]

Internet-Draft            SIP Service Examples              January 2007


      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Referred-By: <alice@atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844539 2890844539 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F12 180 Ringing Carol -> Bob

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds1
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Content-Length: 0


      F13 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds1
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces



Johnston, et al.          Expires July 27, 2007                [Page 53]

Internet-Draft            SIP Service Examples              January 2007


      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890944542 2890844542 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F14 ACK Bob -> Carol

      ACK sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds9
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* Bob and Carol now have established a session.  Bob reports
         success to Alice which Alice probably ignores. */

      F15 NOTIFY Bob -> Alice

      NOTIFY sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds67
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 3 NOTIFY
      Event: refer
      Subscription-State: terminated;reason=noresource
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds1
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309



Johnston, et al.          Expires July 27, 2007                [Page 54]

Internet-Draft            SIP Service Examples              January 2007


      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Content-Type: application/sdp
      Content-Length: ...


      F16 200 OK Alice -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds6
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=314159
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345601@atlanta.example.com
      CSeq: 3 NOTIFY
      Content-Length: 0

2.5.  Transfer - Attended


           Alice             Bob          Carol
             |                |              |
             |    INVITE F1   |              |
             |--------------->|              |
             | 180 Ringing F2 |              |
             |<---------------|              |
             |    200 OK F3   |              |
             |<---------------|              |
             |     ACK F4     |              |
             |--------------->|              |
             |       RTP      |              |
             |<==============>|              |
             |INVITE (hold) F5|              |
             |<---------------|              |
             |    200 OK F6   |              |
             |--------------->|              |
             |     ACK F7     |              |
             |<---------------|              |
             |     No RTP     |              |
             |                |  INVITE F8   |
             |                |------------->|
             |                | 180 Ringing F9
             |                |<-------------|
             |                |  200 OK F10  |
             |                |<-------------|



Johnston, et al.          Expires July 27, 2007                [Page 55]

Internet-Draft            SIP Service Examples              January 2007


             |                |    ACK F11   |
             |                |------------->|
             |                |     RTP      |
             |                |<============>|
             |                |INVITE (hold) F12
             |                |------------->|
             |                | 200 OK F13   |
             |                |<-------------|
             |                |    ACK F14   |
             |                |------------->|
             |                |     No RTP   |
             | REFER Refer-To: C F15         |
             |<---------------|              |
             |202 Accepted F16|              |
             |--------------->|              |
             |   NOTIFY F17   |              |
             |--------------->|              |
             |   200 OK F18   |              |
             |<---------------|              |
             |     INVITE Replaces: B F19    |
             |------------------------------>|
             |            200 OK F20         |
             |<------------------------------|
             |             ACK F21           |
             |------------------------------>|
             |               RTP             |
             |<=============================>|
             |                |    BYE F22   |
             |                |<-------------|
             |                |  200 OK F23  |
             |                |------------->|
             |   NOTIFY F24   |              |
             |--------------->|              |
             |   200 OK F25   |              |
             |<---------------|              |
             |    BYE F26     |              |
             |<---------------|              |
             |   200 OK F27   |              |
             |--------------->|              |


   In this scenario, Alice calls Bob. Bob puts Alice on hold then calls
   Carol to announce transfer, then places Carol on hold.  Bob transfers
   Alice to Carol which replaces the session between Bob and Carol.
   Carol then disconnects session with Bob. Alice reports success of
   transfer to Bob, who then disconnects with Alice.  In this example,
   the Replaces header field [4] is inserted into the Refer-To URI by
   Bob. Note that the Refer-To URI is the Contact URI returned by Carol



Johnston, et al.          Expires July 27, 2007                [Page 56]

Internet-Draft            SIP Service Examples              January 2007


   in the 200 OK response F10.  This ensures that only the correct
   instance of Carol is reached.  The presence of the gr URI parameter
   in the Contact URI in message F10 indicates that the Contact URI is a
   GRUU [22] and will be globally routable outside of the dialog.
   Without knowing the Contact URI is a gruu, Bob must be prepared, if
   the triggered INVITE had failed, to retry the REFER with a Refer-To
   URI of the URI used to reach Carol but with a Require: replaces
   header escaped in the Refer-To header field, as discussed in the
   transfer [7] document.

   Message Details


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE



Johnston, et al.          Expires July 27, 2007                [Page 57]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Alice -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Alice and Bob have established a session.
          Bob puts Alice on Hold */

      F5 INVITE Bob -> Alice



Johnston, et al.          Expires July 27, 2007                [Page 58]

Internet-Draft            SIP Service Examples              January 2007


      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Content-Type: application/sdp
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F6 200 OK Alice -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly



Johnston, et al.          Expires July 27, 2007                [Page 59]

Internet-Draft            SIP Service Examples              January 2007


      F7 ACK Bob -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds3
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 ACK
      Content-Length: 0


      /* Bob calls Carol  */

      F8 INVITE Bob -> Carol

      INVITE sips:carol@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F9 180 Ringing Carol -> Bob

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3



Johnston, et al.          Expires July 27, 2007                [Page 60]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE
      Contact: <sips:39itp34klkd@chicago.example.com>
      Content-Length: 0


      F10 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE
      Contact: <sips:39itp34klkd@chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 ACK Bob -> Carol

      ACK sips:39itp34klkd@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashd5
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 ACK
      Content-Length: 0


      /* Bob puts Carol on hold */

      F12 INVITE Bob -> Carol




Johnston, et al.          Expires July 27, 2007                [Page 61]

Internet-Draft            SIP Service Examples              January 2007


      INVITE sips:39itp34klkd@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds0
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 43 INVITE
      Contact: <sips:bob@client.biloxi.example.com>;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 289084834 2890844835 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=sendonly


      F13 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds0
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 43 INVITE
      Contact: <sips:39itp34klkd@chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844923 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly



Johnston, et al.          Expires July 27, 2007                [Page 62]

Internet-Draft            SIP Service Examples              January 2007


      F14 ACK Bob -> Carol

      ACK sips:39itp34klkd@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash334
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 43 ACK
      Content-Length: 0


      /* Bob  Transfers  Alice to Carol.  */

      F15 REFER Bob -> Alice

      REFER sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds2g
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1025 REFER
    <allOneLine>
      Refer-To: <sips:39itp34klkd@chicago.example.com?Replaces=
      sdjfdjfskdf%40biloxi.example.com%3Bto-tag%3D5f35a3
      %3Bfrom-tag%3D8675309&Require=replaces>
    </allOneLine>
      Referred-By: <sips:bob@biloxi.example.com>
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F16 202 Accepted Alice -> Bob

      SIP/2.0 202 Accepted
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds2g
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      Contact: <sips:alice@client.atlanta.example.com>
      CSeq: 1025 REFER
      Content-Length: 0




Johnston, et al.          Expires July 27, 2007                [Page 63]

Internet-Draft            SIP Service Examples              January 2007


      F17 NOTIFY Alice -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfK
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 NOTIFY
      Contact: <sips:alice@client.atlanta.example.com>
      Event: refer
      Subscription-State: active;expires=60
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 100 Trying


      F18 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfK
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 NOTIFY
      Content-Length: 0


      /*  Alice establishes session with Carol which replaces the
          session between Bob and Carol */

      F19 INVITE Alice -> Carol

      INVITE sips:39itp34klkd@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKadfe4ko
      To: Carol <sips:39itp34klkd@chicago.example.com>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=3461
      Call-ID: 9435674543@atlanta.example.com
      CSeq: 1 INVITE
      Require: replaces
      Referred-By: <sips:bob@biloxi.example.com>
      Replaces: sdjfdjfskdf@biloxi.example.com



Johnston, et al.          Expires July 27, 2007                [Page 64]

Internet-Draft            SIP Service Examples              January 2007


       ;to-tag=5f35a3;from-tag=8675309
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844989 2890844989 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F20 200 OK Carol -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKadfe4ko
       ;received=192.0.2.103
      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a
      From: Alice <sips:alice@atlanta.example.com>;tag=3461
      Call-ID: 9435674543@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:39itp34klkd@chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844221 2890844221 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 49172 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F21 ACK Alice -> Carol

      ACK sips:39itp34klkd@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKadfe4kU3
      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a
      Max-Forwards: 70



Johnston, et al.          Expires July 27, 2007                [Page 65]

Internet-Draft            SIP Service Examples              January 2007


      From: Alice <sips:alice@atlanta.example.com>;tag=3461
      Call-ID: 9435674543@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      /* Carol then disconnects from Bob */

      F22 BYE Carol -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfE
      To: Bob <sips:bob@biloxi.example.com>;tag=8675309
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F23 200 OK Bob -> Carol

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfE
       ;received=192.0.2.123
      To: Bob <sips:bob@biloxi.example.com>;tag=8675309
      From: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 1 BYE
      Content-Length: 0


      /*  Alice tells Bob that the call has been
          successfully transferred */

      F24 NOTIFY Alice -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf2N
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com



Johnston, et al.          Expires July 27, 2007                [Page 66]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 3 NOTIFY
      Event: refer
      Subscription-State: terminated;reason=noresource
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKadfe4ko
       ;received=192.0.2.103
      To: Carol <sips:39itp34klkd@chicago.example.com>;tag=ff3a
      From: Alice <sips:alice@atlanta.example.com>;tag=3461
      Call-ID: 9435674543@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:39itp34klkd@chicago.example.com>


      F25 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 3 NOTIFY
      Content-Length: 0


      /* Bob disconnects with  Alice */

      F26 BYE Bob -> Alice

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7P
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1026 BYE
      Content-Length: 0


      F27 200 OK Alice -> Bob

      SIP/2.0 200 OK



Johnston, et al.          Expires July 27, 2007                [Page 67]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7P
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1026 BYE
      Content-Length: 0

2.6.  Transfer - Instant Messaging


            Alice          Bob                Carol
             |              |                   |
             |   INVITE F1  |                   |
             |------------->|                   |
             | 180 Ringing F2                   |
             |<-------------|                   |
             |  200 OK F3   |                   |
             |<-------------|                   |
             |    ACK F4    |                   |
             |------------->|                   |
             |  Both way RTP Established        |
             |<============>|                   |
             |              |     MESSAGE F5    |
             |              |------------------>|
             |              |     200 OK F6     |
             |              |<------------------|
             |              |                   |
             |       INVITE Replaces:A-B F7     |
             |<---------------------------------|
             |            200 OK F8             |
             |--------------------------------->|
             |               ACK F9             |
             |<---------------------------------|
             |   Both way RTP Established       |
             |<================================>|
             |    BYE F10   |                   |
             |------------->|                   |
             |  200 OK F11  |                   |
             |<-------------|                   |
             |                                  |

   In this scenario, Alice and Bob establish a session between them.
   Bob wants Carol to take the call so sends an Instant Message (IM) to
   Carol containing Alice's URI and an embedded Replaces header field.
   If Carol clicks on the URI, Carol's SIP UA sends an INVITE to Alice
   which replaces the session with Bob.



Johnston, et al.          Expires July 27, 2007                [Page 68]

Internet-Draft            SIP Service Examples              January 2007


   This scenario shows the use of the SIP MESSAGE [15] method to pass
   the URI.  However, another IM protocol or other method could have
   been used to pass the URI from Bob to Carol.

   Message Details


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice




Johnston, et al.          Expires July 27, 2007                [Page 69]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      Contact: <sips:bob@client.biloxi.example.com>
      CSeq: 1 INVITE
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Alice -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74r
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      CSeq: 1 ACK
      Content-Length: 0


      /* Bob IMs Carol  */

      F5 MESSAGE Bob -> Carol

      MESSAGE sips:carol@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>



Johnston, et al.          Expires July 27, 2007                [Page 70]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 MESSAGE
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE
      Supported: replaces
      Content-Type: text/html
      Content-Length: ...

      <HTML>Do you want to take this call from
    <allOneLine>
      <A HREF="sips:a8342043f@atlanta.example.com;gr?Replaces=
      12345600@atlanta.example.com%3Bto-tag%3D3145678
      %3Bfrom-tag%3D1234567&Require=replaces">
      Alice</A>?
    </allOneLine>
       </HTML>


      F6 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=5f35a3
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 MESSAGE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE
      Supported: replaces
      Content-Length: 0


   /* Carol takes the call from Bob */

      F7 INVITE  Carol -> Alice

      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS pc.biloxi.example.com:5061
       ;branch=z9hG4bK74HH
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=8675310
      To: Alice <sips:a8342043f@atlanta.example.com;gr>
      Call-ID: 563456212@b2.chicago.example.com
      CSeq: 1 INVITE
      Require: replaces
      Replaces: 12345600@atlanta.example.com
       ;to-tag=3145678;from-tag=1234567



Johnston, et al.          Expires July 27, 2007                [Page 71]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890843122 2890843122 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 5342 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      /* Alice matches the dialog information in the
         Replaces header and accepts the INVITE */

      F8 200 OK Alice -> Carol

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS pc.biloxi.example.com:5061
       ;branch=z9hG4bK74HH
       ;received=192.0.2.114
      From: Carol <sips:carol@chicago.example.com>;tag=8675310
      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=131256
      Call-ID: 563456212@b2.chicago.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 289084543 289084543 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49172 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F9 ACK  Carol -> Alice

      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS b2.biloxi.example.com:5061
       ;branch=z9hG4bK7435



Johnston, et al.          Expires July 27, 2007                [Page 72]

Internet-Draft            SIP Service Examples              January 2007


      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=8675310
      To: Alice <sips:a8342043f@atlanta.example.com;gr>;tag=131256
      Call-ID: 563456212@b2.chicago.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* RTP streams are established between Alice and Carol.
         Alice Hangs Up with Bob due to the Replaces header field. */

      F10 BYE Alice -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F11 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq:  2 BYE
      Content-Length: 0
















Johnston, et al.          Expires July 27, 2007                [Page 73]

Internet-Draft            SIP Service Examples              January 2007


2.7.  Call Forwarding Unconditional


            Alice           Proxy          Gateway
             |                |              |
             |    INVITE F1   |              |
             |--------------->|              |
             |(100 Trying) F2 |              |
             |<---------------|              |
             | (181 Call Is Being Forwarded) F3
             |<---------------|   INVITE F4  |
             |                |------------->|
             |                |180 Ringing F5|
             | 180 Ringing F6 |<-------------|
             |<---------------|  200 OK F7   |
             |    200 OK F8   |<-------------|
             |<---------------|              |
             |     ACK F9     |              |
             |--------------->|    ACK F10   |
             |                |------------->|
             |    Both way RTP Established   |
             |<=============================>|
             |     BYE F11    |              |
             |--------------->|   BYE F12    |
             |                |------------->|
             |                |   200 OK F13 |
             |    200 OK F14  |<-------------|
             |<---------------|              |
             |                |              |

   Bob wants all calls forwarded to the PSTN (which is just another URI
   to the proxy server).  Alice calls Bob. The proxy server rewrites the
   Request URI, and forwards the INVITE to a Gateway.  Details of
   messaging behind the Gateway are not shown.

   Note that the 181 Call is Being Forwarded response does not have a To
   tag added as the proxy does not wish to establish an early dialog
   with Alice.  Strictly speaking, the proxy is behaving as a User Agent
   in this case as a proxy can not generate non-100 provisional
   responses.

   Note also that forwarding could be accomplished using a redirect (302
   Moved Temporarily response).

   Message Details


      F1 INVITE Alice -> Proxy



Johnston, et al.          Expires July 27, 2007                [Page 74]

Internet-Draft            SIP Service Examples              January 2007


      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 (100 Trying) Proxy -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F3 (181 Call is Being Forwarded) Proxy -> Alice

      SIP/2.0 181 Call is Being Forwarded
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=9214d
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0





Johnston, et al.          Expires July 27, 2007                [Page 75]

Internet-Draft            SIP Service Examples              January 2007


      /* Proxy forwards call by rewriting Request-URI */

      F4 INVITE Proxy -> Gateway

      INVITE sips:+19727293660@gw1.example.com;user=phone SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F5 180 Ringing Gateway -> Proxy

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:+19727293660@gw1.example.com;user=phone>
      Content Length:0





Johnston, et al.          Expires July 27, 2007                [Page 76]

Internet-Draft            SIP Service Examples              January 2007


      F6 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:+19727293660@gw1.example.com;user=phone>
      Content Length: 0


      F7 200 OK Gateway -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:+19727293660@gw1.example.com;user=phone>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=GATEWAY1 2890844527 2890844527 IN IP4 gatewayone.example.com
      s=
      c=IN IP4 gatewayone.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9



Johnston, et al.          Expires July 27, 2007                [Page 77]

Internet-Draft            SIP Service Examples              January 2007


       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:+19727293660@gw1.example.com;user=phone>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=GATEWAY1 2890844527 2890844527 IN IP4 gatewayone.example.com
      s=
      c=IN IP4 gatewayone.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F9 ACK Alice -> Proxy

      ACK sips:+19727293660@gw1.example.com;user=phone SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf31
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F10 ACK Proxy -> Gateway

      ACK sips:+19727293660@gw1.example.com;user=phone SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749ws.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf31
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0



Johnston, et al.          Expires July 27, 2007                [Page 78]

Internet-Draft            SIP Service Examples              January 2007


      F11 BYE Alice -> Proxy

      BYE sips:+19727293660@gw1.example.com;user=phone SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfJe
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F12 BYE Proxy -> Gateway

      BYE sips:+19727293660@gw1.example.com;user=phone SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749G1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfJe
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F13 200 OK Gateway -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749G1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfJe
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F14 200 OK Proxy -> Alice




Johnston, et al.          Expires July 27, 2007                [Page 79]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfJe
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345600@atlanta.example.com
      CSeq:  2 BYE
      Content-Length: 0

2.8.  Call Forwarding - Busy


           Alice            Proxy          User B1             User B2
             |                |              |                   |
             |    INVITE F1   |              |                   |
             |--------------->|   INVITE F2  |                   |
             |                |------------->|                   |
             |(100 Trying) F3 |              |                   |
             |<---------------|  486 Busy F4 |                   |
             |                |<-------------|                   |
             |                |     ACK F5   |                   |
             |                |------------->|                   |
             |(181 Call is Being Forwarded) F6                   |
             |<---------------|              |    INVITE F7      |
             |                |--------------------------------->|
             |                |              | 180 Ringing F8    |
             |                |<---------------------------------|
             | 180 Ringing F9 |              |                   |
             |<---------------|              |      200 OK F10   |
             |                |<---------------------------------|
             |    200 OK F11  |              |                   |
             |<---------------|              |                   |
             |     ACK F12    |              |                   |
             |--------------->|              |     ACK F13       |
             |                |--------------------------------->|
             |               Both way RTP Established            |
             |<=================================================>|
             |    BYE F14     |              |                   |
             |--------------->|              |      BYE F15      |
             |                |--------------------------------->|
             |                |              |    200 OK F16     |
             |  200 OK F17    |<---------------------------------|
             |<---------------|              |                   |
             |                |              |                   |

   Bob wants calls to B1 forwarded to B2 if B1 is busy (this information
   is known to the proxy).  Alice calls B1, B1 is busy, the proxy server



Johnston, et al.          Expires July 27, 2007                [Page 80]

Internet-Draft            SIP Service Examples              January 2007


   places call to B2.

   Message Details


      F1 INVITE Alice -> Proxy

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 INVITE Proxy -> B1

      INVITE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...




Johnston, et al.          Expires July 27, 2007                [Page 81]

Internet-Draft            SIP Service Examples              January 2007


      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F3 (100 Trying) Proxy -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F4 486 Busy Here B1 -> Proxy

      SIP/2.0 486 Busy Here
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F5 ACK Proxy -> B1

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK



Johnston, et al.          Expires July 27, 2007                [Page 82]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: 0


      F6 (181 Call is Being Forwarded) Proxy -> Alice

      SIP/2.0 181 Call is Being Forwarded
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=9214d
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      /* The proxy now forwards the call to B2 */

      F7 INVITE Proxy -> B2

      INVITE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 180 Ringing B2 -> Proxy




Johnston, et al.          Expires July 27, 2007                [Page 83]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Content-Length: 0


      F9 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Content-Length: 0


      F10 200 OK B2 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp



Johnston, et al.          Expires July 27, 2007                [Page 84]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
      s=
      c=IN IP4 client2.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
      s=
      c=IN IP4 client2.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F12 ACK Alice -> Proxy

      ACK sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfX
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0



Johnston, et al.          Expires July 27, 2007                [Page 85]

Internet-Draft            SIP Service Examples              January 2007


      F13 ACK Proxy -> B2

      ACK sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83731
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfX
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* RTP streams are established between A and B2 */

      /*  Alice eventually hangs up with User B2. */

      F14 BYE Alice -> Proxy

      BYE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bW4
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F15 BYE Proxy -> B2

      BYE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837493
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bW4
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0



Johnston, et al.          Expires July 27, 2007                [Page 86]

Internet-Draft            SIP Service Examples              January 2007


      F16 200 OK B2 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837493
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bW4
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F17 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bW4
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq:  2 BYE
      Content-Length: 0
























Johnston, et al.          Expires July 27, 2007                [Page 87]

Internet-Draft            SIP Service Examples              January 2007


2.9.  Call Forwarding - No Answer


           Alice            Proxy         User B1             User B2
             |                |              |                   |
             |    INVITE F1   |              |                   |
             |--------------->|   INVITE F2  |                   |
             |(100 Trying) F3 |------------->|                   |
             |<---------------|180 Ringing F4|                   |
             | 180 Ringing F5 |<-------------|                   |
             |<---------------|              |                   |
             |                 Request Timeout                   |
             |                |              |                   |
             |                |   CANCEL F6  |                   |
             |                |------------->|                   |
             |                |   200 OK F7  |                   |
             |                |<-------------|                   |
             |                |     487 F8   |                   |
             |                |<-------------|                   |
             |                |     ACK F9   |                   |
             |                |------------->|                   |
             |(181 Call is Being Forwarded) F10                  |
             |<---------------|              |    INVITE F11     |
             |                |--------------------------------->|
             |                |              | 180 Ringing F12   |
             | 180 Ringing F13|<---------------------------------|
             |<---------------|              |      200 OK F14   |
             |                |<---------------------------------|
             |   200 OK F15   |              |                   |
             |<---------------|              |                   |
             |     ACK F16    |              |                   |
             |--------------->|              |     ACK F17       |
             |                |--------------------------------->|
             |               Both way RTP Established            |
             |<=================================================>|
             |    BYE F18     |              |                   |
             |--------------->|              |      BYE F19      |
             |                |--------------------------------->|
             |                |              |    200 OK F20     |
             |  200 OK F21    |<---------------------------------|
             |<---------------|              |                   |
             |                |              |                   |

   Bob wants calls to B1 forwarded to B2 if B1 is not answered
   (information is known to the proxy server).  Alice calls B1 and no
   one answers.  The proxy server then places the call to B2.

   Message Details



Johnston, et al.          Expires July 27, 2007                [Page 88]

Internet-Draft            SIP Service Examples              January 2007


      F1 INVITE Alice -> Proxy

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 INVITE Proxy -> B1

      INVITE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0



Johnston, et al.          Expires July 27, 2007                [Page 89]

Internet-Draft            SIP Service Examples              January 2007


      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F3 (100 Trying) Proxy -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F4 180 Ringing B1 -> Proxy

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F5 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0



Johnston, et al.          Expires July 27, 2007                [Page 90]

Internet-Draft            SIP Service Examples              January 2007


      /* B1 rings until a configurable timer expires in the Proxy. The
         Proxy sends Cancel and proceeds down the list of routes. */

      F6 CANCEL Proxy -> B1

      CANCEL sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 CANCEL
      Content-Length: 0


      F7 200 OK B1 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=329d823
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 CANCEL
      Content-Length: 0


      F8 487 Request Terminated B1 -> Proxy

      SIP/2.0 487 Request Terminated
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F9 ACK Proxy -> B1

      ACK sips:bob@client.biloxi.example.com SIP/2.0



Johnston, et al.          Expires July 27, 2007                [Page 91]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=3145678
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F10 (181 Call is Being Forwarded) Proxy -> Alice

      SIP/2.0 181 Call is Being Forwarded
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=9214d
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F11 INVITE Proxy -> B2

      INVITE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0



Johnston, et al.          Expires July 27, 2007                [Page 92]

Internet-Draft            SIP Service Examples              January 2007


      a=rtpmap:0 PCMU/8000


      F12 180 Ringing B2 -> Proxy

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Content-Length: 0


      F13 180 Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Content-Length: 0


      F14 200 OK B2 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432



Johnston, et al.          Expires July 27, 2007                [Page 93]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
      s=
      c=IN IP4 client2.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F15 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client2.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
      s=
      c=IN IP4 client2.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F16 ACK Alice -> Proxy

      ACK sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf3
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70



Johnston, et al.          Expires July 27, 2007                [Page 94]

Internet-Draft            SIP Service Examples              January 2007


      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F17 ACK Proxy -> B2

      ACK sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8374.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf3
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* RTP streams are established between A and B2.
         Alice Hangs Up with User B2. */

      F18 BYE Alice -> Proxy

      BYE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b3f
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F19 BYE Proxy -> B2

      BYE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b3f
       ;received=192.0.2.103



Johnston, et al.          Expires July 27, 2007                [Page 95]

Internet-Draft            SIP Service Examples              January 2007


      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F20 200 OK B2 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK837.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b3f
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F21 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b3f
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq:  2 BYE
      Content-Length: 0
















Johnston, et al.          Expires July 27, 2007                [Page 96]

Internet-Draft            SIP Service Examples              January 2007


2.10.  3-way Conference - Third Party is Added


            Alice           Bob            Carol
             |    INVITE F1   |              |
             |--------------->|              |
             | 180 Ringing F2 |              |
             |<---------------|              |
             |    200 OK F3   |              |
             |<---------------|              |
             |     ACK F4     |              |
             |--------------->|              |
             |       RTP      |              |
             |<==============>|              |
             |   INVITE F5    |              |
             |<---------------|              |
             |    200 OK F6   |              |
             |--------------->|              |
             |     ACK F7     |              |
             |<---------------|  INVITE F8   |
             |                |------------->|
             |                |    180 F9    |
             |                |<-------------|
             |                |  200 OK F10  |
             |                |<-------------|
             |                |  ACK F11     |
             |                |------------->|
             |                |       RTP    |
             |                |<============>|

   In this scenario, Alice and Bob are in a 2-party call (session) when
   Bob wishes to add Carol into the conversation.  Bob is capable of
   media mixing in a 3-party call.  Bob first sends a re-INVITE to Alice
   changing Contact URIs to one that indicates Bob's mixer and acts like
   a focus.  As a result, Bob includes the "isfocus" feature tag [10] as
   described in [11].  Bob then INVITEs Carol using the same Contact
   URI.  Note that Bob could wait to re-INVITE Alice until after Carol
   has answered.  Bob could also put Alice on hold before calling Carol

   Message Details


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70



Johnston, et al.          Expires July 27, 2007                [Page 97]

Internet-Draft            SIP Service Examples              January 2007


      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:b54gh42f5@biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice

      SIP/2.0 200 OK

      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:b54gh42f5@biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp



Johnston, et al.          Expires July 27, 2007                [Page 98]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Alice -> Bob

      ACK sips:b54gh42f5@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfL
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* Alice and Bob have established a session.
          Bob re-INVITEs changing Contact URIs */

      F5 INVITE Bob -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus
      Content-Type: application/sdp
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0



Johnston, et al.          Expires July 27, 2007                [Page 99]

Internet-Draft            SIP Service Examples              January 2007


      m=audio 49172 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F6 200 OK Alice -> Bob

      SIP/2.0 200 OK

      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F7 ACK Bob -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash3G
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 ACK
      Content-Length: 0


      /* Bob calls Carol  */

      F8 INVITE Bob -> Carol

      INVITE sips:carol@chicago.example.com SIP/2.0



Johnston, et al.          Expires July 27, 2007               [Page 100]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashJfd
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE
      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 48174 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F9 180 Ringing Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashJfd
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=341313
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F10 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashJfd
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=341313
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 INVITE



Johnston, et al.          Expires July 27, 2007               [Page 101]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 ACK Bob -> Carol

      ACK sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash431
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=341313
      Call-ID: sdjfdjfskdf@biloxi.example.com
      CSeq: 42 ACK
      Content-Length: 0


      /* User B's mixer know mixes media from both A and C
         to create the 3-way conference.  */





















Johnston, et al.          Expires July 27, 2007               [Page 102]

Internet-Draft            SIP Service Examples              January 2007


2.11.  3-way Conference - Third Party Joins


            Alice           Bob            Carol
             |    INVITE F1   |              |
             |--------------->|              |
             | 180 Ringing F2 |              |
             |<---------------|              |
             |    200 OK F3   |              |
             |<---------------|              |
             |     ACK F4     |              |
             |--------------->|              |
             |       RTP      |              |
             |<==============>|  INVITE Join:A-B F5
             |                |<-------------|
             |                |    180 F6    |
             |                |------------->|
             |   INVITE F7    |              |
             |<---------------|              |
             |    200 OK F8   |              |
             |--------------->|              |
             |     ACK F9     |              |
             |<---------------|              |
             |                |  200 OK F10  |
             |                |------------->|
             |                |  ACK F11     |
             |                |<-------------|
             |                |       RTP    |
             |                |<============>|


   In this scenario, Alice and Bob are in a 2 party call and Carol
   wishes to join resulting in a three party call.  Carol could have
   learned Bob's dialog identifier using some non-SIP means, or possibly
   from a NOTIFY with the dialog package sent by Bob. Carol sends an
   INVITE to Bob containing a Join header identifying the dialog between
   Alice and Bob. Bob re-INVITEs Alice to switch to focus mode and
   includes the "isfocus" feature tag [10] as described in [11].  Bob
   then accepts the INVITE from Carol, resulting in the 3-way call.

   Message Details


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9



Johnston, et al.          Expires July 27, 2007               [Page 103]

Internet-Draft            SIP Service Examples              January 2007


      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:b54gh42f5@biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:b54gh42f5@biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, join, gruu
      Content-Type: application/sdp



Johnston, et al.          Expires July 27, 2007               [Page 104]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 ACK Alice -> Bob

      ACK sips:b54gh42f5@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf6
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=23431
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /*  Alice and Bob have established a session.
          Carol requests to join the session */

      F5 INVITE Carol -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=8675309
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 452k499sk@chicago.example.com
      CSeq: 99 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, join
      Join: 12345600@atlanta.example.com;from-tag=1234567;to-tag=23431
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com



Johnston, et al.          Expires July 27, 2007               [Page 105]

Internet-Draft            SIP Service Examples              January 2007


      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F6 180 Ringing Bob -> Carol

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=120.
      From: Carol <sips:carol@chicago.example.com>;tag=8675309
      To: Bob <sips:bob@biloxi.example.com>;tag=0982
      Call-ID: 452k499sk@chicago.example.com
      CSeq: 99 INVITE
      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Length: 0


      F7 INVITE Bob -> Alice

      INVITE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdyKL
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus
      Content-Type: application/sdp
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, join, gruu
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 49172 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 200 OK Alice -> Bob




Johnston, et al.          Expires July 27, 2007               [Page 106]

Internet-Draft            SIP Service Examples              January 2007


      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdyKL
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F9 ACK Bob -> Alice

      ACK sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnash3g
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=23431
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1024 ACK
      Content-Length: 0


      F10 200 OK Bob -> Carol

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=120.
      From: Carol <sips:carol@chicago.example.com>;tag=8675309
      To: Bob <sips:bob@biloxi.example.com>;tag=0982
      Call-ID: 452k499sk@chicago.example.com
      CSeq: 99 INVITE
      Contact: <sips:bob-Mixer@client.biloxi.example.com>;isfocus
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY



Johnston, et al.          Expires July 27, 2007               [Page 107]

Internet-Draft            SIP Service Examples              January 2007


      Supported: replaces, join, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 48174 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 ACK OK Carol -> Bob

      ACK sips:bob-Mixer@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS chicago.example.com:5061
       ;branch=z9hG4bKnash4Gf
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=8675309
      To: Bob <sips:bob@biloxi.example.com>;tag=0982
      Call-ID: 452k499sk@chicago.example.com
      CSeq: 99 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces, join
      Content-Length:0



2.12.  Find-Me


             Alice           Proxy           User   User   User   User
                                              B1     B2     B3     B4
             |                |              |      |      |      |
             |    INVITE F1   |              |      |      |      |
             |--------------->|   INVITE F2  |      |      |      |
             |                |------------->|      |      |      |
             |(100 Trying) F3 |              |      |      |      |
             |<---------------|180 Ringing F4|      |      |      |
             |                |<-------------|      |      |      |
             | 180 Ringing F5 |              |      |      |      |
             |<---------------|              |      |      |      |
             |                |    Timeout   |      |      |      |
             |                |              |      |      |      |
             |                |   CANCEL F6  |      |      |      |
             |                |------------->|      |      |      |
             |                |   200 OK F7  |      |      |      |



Johnston, et al.          Expires July 27, 2007               [Page 108]

Internet-Draft            SIP Service Examples              January 2007


             |                |<-------------|      |      |      |
             |                |     487 F8   |      |      |      |
             |                |<-------------|      |      |      |
             |                |     ACK F9   |      |      |      |
             |                |------------->|      |      |      |
             |                |     INVITE F10      |      |      |
             |                |-------------------->|      |      |
             |                |480 Not Logged In F11|      |      |
             |                |<--------------------|      |      |
             |                |              ACK F12|      |      |
             |                |-------------------->|      |      |
             |                |          INVITE F13        |      |
             |                |--------------------------->|      |
             |                |      486 Busy Here F14     |      |
             |                |<---------------------------|      |
             |                |            ACK F15         |      |
             |                |--------------------------->|      |
             |                |              INVITE F16           |
             |                |---------------------------------->|
             |                |            180 Ringing F17        |
             |     180 F18    |<----------------------------------|
             |<---------------|               200 OK F19          |
             |   200 OK F20   |<----------------------------------|
             |<---------------|                                   |
             |     ACK F21    |                                   |
             |--------------->|                 ACK F22           |
             |                |---------------------------------->|
             |               Both way RTP Established             |
             |<==================================================>|
             |                |                  BYE F23          |
             |     BYE F24    |<----------------------------------|
             |<---------------|                                   |
             |    200 OK F25  |                                   |
             |--------------->|                 200 OK F26        |
             |                |---------------------------------->|
             |                |                                   |

   Alice's call to Bob will result in an attempt to locate that user by
   calling locations from a list of contacts.  The location to answer
   the call becomes the active set, no other sets may join the call.

   While this flow shows a sequential search, the search could be
   accomplished using parallel forking, as in the previous example.

   Message Details


      F1 INVITE Alice -> Proxy



Johnston, et al.          Expires July 27, 2007               [Page 109]

Internet-Draft            SIP Service Examples              January 2007


      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t= 0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 INVITE Proxy -> B1

      INVITE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t= 0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000





Johnston, et al.          Expires July 27, 2007               [Page 110]

Internet-Draft            SIP Service Examples              January 2007


      F3 (100 Trying) Proxy -> Alice

      SIP/2.0 100 Trying
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F4 180 Ringing B1 -> Proxy

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F5 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      /* B1 rings until a configurable timer in the Proxy
         expires.  The Proxy then sends Cancel and proceeds down



Johnston, et al.          Expires July 27, 2007               [Page 111]

Internet-Draft            SIP Service Examples              January 2007


         the list of routes. */

      F6 CANCEL Proxy -> B1

      CANCEL sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 CANCEL
      Content-Length: 0


      F7 200 OK B1 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 CANCEL
      Content-Length: 0


      F8 487 Request Terminated B1 -> Proxy

      SIP/2.0 487 Request Terminated
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F9 ACK Proxy -> B1

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061



Johnston, et al.          Expires July 27, 2007               [Page 112]

Internet-Draft            SIP Service Examples              January 2007


       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F10 INVITE Proxy -> B2

      INVITE sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 480 Not Logged In B2 -> Proxy

      SIP/2.0 480 Not Logged In
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314756
      Call-ID: 12345600@atlanta.example.com



Johnston, et al.          Expires July 27, 2007               [Page 113]

Internet-Draft            SIP Service Examples              January 2007


      CSeq: 1 INVITE
      Content-Length: 0


      F12 ACK Proxy -> B2

      ACK sips:bob@client2.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314756
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F13 INVITE Proxy -> B3

      INVITE sips:bob@client3.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.3
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F14 486 Busy Here B3 -> Proxy

      SIP/2.0 486 Busy Here
      Via: SIP/2.0/TLS ss1.example.com:5061



Johnston, et al.          Expires July 27, 2007               [Page 114]

Internet-Draft            SIP Service Examples              January 2007


       ;branch=z9hG4bK83749.3
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F15 ACK Proxy -> B3

      ACK sips:bob@client3.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83765
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F16 INVITE Proxy -> B4

      INVITE sips:bob@client4.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.4
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0



Johnston, et al.          Expires July 27, 2007               [Page 115]

Internet-Draft            SIP Service Examples              January 2007


      a=rtpmap:0 PCMU/8000


      F17 180 Ringing B4 -> Proxy

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.4
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Length: 0


      F18 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Length: 0


      F19 200 OK B4 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.4
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136



Johnston, et al.          Expires July 27, 2007               [Page 116]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com
      s=
      c=IN IP4 client4.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F20 200 OK Proxy -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com
      s=
      c=IN IP4 client4.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F21 ACK Alice -> Proxy

      ACK sips:bob@client4.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136



Johnston, et al.          Expires July 27, 2007               [Page 117]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F22 ACK Proxy -> B4

      ACK sips:bob@client4.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK8374
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* RTP streams are established between A and B4*/

      /* User B4 Hangs Up with User A. */

      F23 BYE B4 -> Proxy

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F24 BYE Proxy -> Alice

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83754
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Max-Forwards: 69



Johnston, et al.          Expires July 27, 2007               [Page 118]

Internet-Draft            SIP Service Examples              January 2007


      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F25 200 OK Alice -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83754
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F26 200 OK Proxy -> B4

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0

















Johnston, et al.          Expires July 27, 2007               [Page 119]

Internet-Draft            SIP Service Examples              January 2007


2.13.  Call Management (Incoming Call Screening)

                                                      Announcement
           Alice           Proxy            Bob           Server

             |                |              |              |
             |    INVITE F1   |              |              |
             |------------------------------>|              |
             | 305 Use Proxy F2              |              |
             |<------------------------------|              |
             |     ACK F3     |              |              |
             |------------------------------>|              |
             |    INVITE F4   |              |              |
             |--------------->|              |              |
             | 407 Proxy Authentication F5   |              |
             |<---------------|              |              |
             |     ACK F6     |              |              |
             |--------------->|              |              |
             |    INVITE F7   |              |              |
             |--------------->|              |              |
             | 403 Screening Failure (Terminating) Error-Info: URI F8
             |<---------------|              |              |
             |     ACK F9     |              |              |
             |--------------->|              |              |
             |    INVITE F10  |              |              |
             |--------------->|  INVITE F11                 |
             |                |---------------------------->|
             |                |   200 OK F12                |
             |    200 OK F13  |<----------------------------|
             |<---------------|                             |
             |     ACK F14    |                             |
             |--------------------------------------------->|
             |          Announcement Played to Caller       |
             |<=============================================|
             |                                    BYE F15   |
             |<---------------------------------------------|
             |     200 OK F16                               |
             |--------------------------------------------->|
             |                                              |
             |                                              |
             |                                              |

   Bob has an incoming call screening list, Alice is included on the
   list of addresses Bob will not accept calls from.  Alice attempts to
   call Bob. Messages F1, F2, and F3 are included to show that Bob does
   not accept INVITEs that have not been screened by the proxy.

   Note that call screening can not be done using the From header -



Johnston, et al.          Expires July 27, 2007               [Page 120]

Internet-Draft            SIP Service Examples              January 2007


   instead some form of authentication credentials must be used.

   The screening proxy inserts an announcement URI in an Error-Info
   header field which Alice accesses by sending an INVITE to listen to
   the Announcement.  The Announcement Server uses the automaton and
   rendering feature tags in F12 and F13 to indicate that it is a media
   server only capability of playing announcements.

   Message Details


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      /* Bob only accepts INVITEs that have been screened
         by the proxy */

      F2 305 Use Proxy Bob -> Alice

      SIP/2.0 305 Use Proxy
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=342123
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE



Johnston, et al.          Expires July 27, 2007               [Page 121]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:ss1.example.com>
      Content-Length: 0


      F3 ACK Alice -> Bob

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=342123
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* A retries the call through the proxy */

      F4 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf0
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      /* Proxy 1 challenges  Alice for authentication */

      F5 407 Proxy Authentication Required Proxy 1 -> Alice

      SIP/2.0 407 Proxy Authentication Required



Johnston, et al.          Expires July 27, 2007               [Page 122]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf0
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7886765
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Proxy-Authenticate: Digest realm="example.com",
       nonce="ea9c8e88df84f1cec4341ae6cbe5a359",
       qop="auth", nc=00000001, cnonce="0a4f113b",
       opaque="", stale=FALSE, qop="auth", algorithm=MD5
      Content-Length: 0


      F6 ACK Alice -> Proxy 1

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf0
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7886765
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 ACK
      Content-Length: 0


      /*  Alice responds by sending an INVITE with authentication
      credentials in it.  */

      F7 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf2
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 3 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Proxy-Authorization: Digest username="alice",
       realm="example.com", qop="auth",
       nc=00000001, cnonce="4gr84543ft2",
       nonce="ae9137be1c87d175c2dd63302a0d6e0a",
       opaque="", uri="sips:bob@biloxi.example.com",
       response="bbaec39f943bdcb3620d90afc548a45c"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY



Johnston, et al.          Expires July 27, 2007               [Page 123]

Internet-Draft            SIP Service Examples              January 2007


      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F8 403 Screening Failure (Terminating) Proxy 1 -> Alice

      SIP/2.0 403 Screening Failure (Terminating)
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf2
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=ffe254
      Call-ID: 12345600@atlanta.example.com
      CSeq: 3 INVITE
      Error-Info: <sips:screen-fail-term-ann@biloxi.example.com>
      Content-Length: 0


      F9 ACK Alice -> Proxy 1

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf2
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=ffe254
      Call-ID: 12345600@atlanta.example.com
      Proxy-Authorization: Digest username="alice",
       realm="example.com", nonce="ae9137be1c87d175c2dd63302a0d6e0a",
       opaque="", uri="sips:bob@biloxi.example.com",
       response="bbaec39f943bdcb3620d90afc548a45c"
      CSeq: 3 ACK
      Content-Length: 0


   /* To hear the recording, Alice connects to the Error-Info URI */

      F10 INVITE Alice -> Proxy 1

      INVITE sips:screen-fail-term-ann@biloxi.example.com SIP/2.0



Johnston, et al.          Expires July 27, 2007               [Page 124]

Internet-Draft            SIP Service Examples              January 2007


      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfj
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F11 INVITE Proxy 1 -> Announcement Server

      INVITE sips:s-f-term-ann@announce.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83743
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfj
       ;received=192.0.2.103
      Max-Forwards: 69
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000





Johnston, et al.          Expires July 27, 2007               [Page 125]

Internet-Draft            SIP Service Examples              January 2007


      F12 200 OK Announcement Server -> Proxy 1

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83743
       ;received=192.0.2.100
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfj
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=234934
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 INVITE
      Contact: <sips:announce.biloxi.example.com>
       ;automaton;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=annc 2890844543 2890844543 IN IP4 announce.biloxi.example.com
      s=
      c=IN IP4 announce.biloxi.example.com
      t=0 0
      m=audio 49174 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F13 200 OK Proxy 1 -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfj
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=234934
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 INVITE
      Contact: <sips:announce.biloxi.example.com>
        ;automaton;+sip.rendering="no"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=annc 2890844543 2890844543 IN IP4 announce.biloxi.example.com
      s=
      c=IN IP4 announce.biloxi.example.com



Johnston, et al.          Expires July 27, 2007               [Page 126]

Internet-Draft            SIP Service Examples              January 2007


      t=0 0
      m=audio 49174 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F14 ACK Alice -> Announcement Server

      ACK sips:announce.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b32
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=234934
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 ACK
      Content-Length: 0


     /* Announcement Server plays announcement then disconnects */

      F15 BYE Announcement Server -> Alice

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS announcement.example.com:5061
       ;branch=z9hG4bK74bKS
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=234934
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2334 BYE
      Content-Length: 0


      F16 200 OK Alice -> Announcement Server

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS announcement.example.com:5061
       ;branch=z9hG4bK74bKS
       ;received=192.0.2.103
      From: Bob <sips:bob@biloxi.example.com>;tag=234934
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2334 BYE
      Content-Length: 0







Johnston, et al.          Expires July 27, 2007               [Page 127]

Internet-Draft            SIP Service Examples              January 2007


2.14.  Call Management (Outgoing Call Screening)


           Alice            Proxy           Bob
             |                |              |
             |    INVITE F1   |              |
             |--------------->|              |
             | 407 Proxy Authentication F2    |
             |<---------------|              |
             |     ACK F3     |              |
             |--------------->|              |
             |    INVITE F4   |              |
             |--------------->|              |
             | 403 Screening Failure (Originating) F5
             |<---------------|              |
             |     ACK F6     |              |
             |--------------->|              |
             |                |              |

   Alice has an outgoing call screening list, Bob is included on the
   list of addresses Alice will not be able to place a call to.  Alice
   attempts to call Bob.

   Alice could establish a session to listen to the announcement in the
   Error-Info header field.

   Message Details


      F1 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com



Johnston, et al.          Expires July 27, 2007               [Page 128]

Internet-Draft            SIP Service Examples              January 2007


      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      /* Proxy 1 challenges  Alice for authentication */

      F2 407 Proxy Authentication Required Proxy 1 -> Alice

      SIP/2.0 407 Proxy Authentication Required
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=90210
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Proxy-Authenticate: Digest realm="example.com",
       nonce="ea9c8e88df84f1cec4341ae6cbe5a359",
       qop=auth, nc=00000001, cnonce="0a4f113b",
       opaque="", stale=FALSE, algorithm=MD5
      Content-Length: 0


      F3 ACK Alice -> Proxy 1

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=90210
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /*  Alice responds be sending an INVITE with authentication
          credentials in it.  */

      F4 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>



Johnston, et al.          Expires July 27, 2007               [Page 129]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Proxy-Authorization: Digest username="alice", realm="example.com",
       nonce="cb360afc54bbaec39f943bd820d9a45c", opaque="",
       uri="sips:bob@biloxi.example.com",
       response="b9d2e5bcdec9f69ab2a9b44f270285a6"
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F5 403 Screening Failure (Originating) Proxy 1 -> Alice

      SIP/2.0 403 Screening Failure (Originating)
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=18017
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Error-Info: <sips:screen-fail-orig-ann@announcement.example.com>
      Content-Length: 0


      F6 ACK Alice -> Proxy 1

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=18017
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 ACK
      Proxy-Authorization: Digest username="alice", realm="example.com",
       nonce="cb360afc54bbaec39f943bd820d9a45c", opaque="",
       uri="sips:bob@biloxi.example.com",
       response="b9d2e5bcdec9f69ab2a9b44f270285a6"



Johnston, et al.          Expires July 27, 2007               [Page 130]

Internet-Draft            SIP Service Examples              January 2007


      Content-Length: 0

2.15.  Call Park


           Alice           Bob        Park Server       Carol
             |              |              |              |
             |   INVITE F1  |              |              |
             |------------->|              |              |
             |180 Ringing F2|              |              |
             |<-------------|              |              |
             |  200 OK F3   |              |              |
             |<-------------|              |              |
             |    ACK F4    |              |              |
             |------------->|              |              |
             |  RTP Media   |              |              |
             |<============>|              |              |
             |      Bob Parks Call         |              |
             |              |   REFER Refer-To: A F5      |
             |              |------------->|              |
             |              |    202 F6    |              |
             |              |<-------------|              |
             |              |   NOTIFY F7  |              |
             |              |<-------------|              |
             |              |    200 F8    |              |
             |              |------------->|              |
             |  INVITE F9 Replaces: B      |              |
             |<----------------------------|              |
             |          200 OK F10         |              |
             |---------------------------->|              |
             |           ACK F11           |              |
             |<----------------------------|              |
             |           RTP Music         |              |
             |<===========================>|              |
             |     BYE F12  |              |              |
             |------------->|  NOTIFY F14  |              |
             |  200 OK F13  |<-------------|              |
             |<-------------|  200 OK F15  |              |
             |              |------------->|              |
             |              |   Carol picks up the call   |
             |              |              |              |
             |           INVITE Replaces: Park Server F16 |
             |<-------------------------------------------|
             |              |              |   200 F17    |
             |------------------------------------------->|
             |              |              |    ACK F18   |
             |<-------------------------------------------|
             |                  RTP Media                 |



Johnston, et al.          Expires July 27, 2007               [Page 131]

Internet-Draft            SIP Service Examples              January 2007


             |<==========================================>|
             |           BYE F19           |              |
             |---------------------------->|              |
             |          200 OK F20         |              |
             |<----------------------------|              |
             |       No more RTP Music     |              |

   In this example, Alice calls Bob. Bob then parks the call at the Park
   Server by sending a REFER to the Park Server.  The server sends an
   INVITE to Alice which replaces the session between Alice and Bob. The
   Park Server utilizes the automaton, rendering, and byeless feature
   tags in F9 to indicate its capabilities to Alice.  The call is
   accepted by Alice and causes Alice to send a BYE to Bob. Bob receives
   notification of the successful park, and also receives the dialog
   identifiers in the application/sip body of the NOTIFY response.

   Carol wishes to retrieve the call, so she sends an INVITE containing
   the dialog identifiers to Alice which replaces the session with the
   Park Server.  Alice accepts the call and sends a BYE to the Park
   Server.  Note that Carol needs the dialog identifiers to carry out
   this sequence.  This example assumes that Carol obtains them from
   Bob, who obtained them from a NOTIFY from the Park Server.  If the
   Park Server did not return the dialog identifiers (Call-ID, To and
   From tags) in the NOTIFY, Carol could send a SUBSCRIBE to retrieve
   this information.

   Note that this call flow is a special case of call transfer.

   Note also that this flow could also be used for Music on Hold.

   Message Details.


      F1 INVITE Alice -> Bob

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.alice.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...



Johnston, et al.          Expires July 27, 2007               [Page 132]

Internet-Draft            SIP Service Examples              January 2007


      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F2 180 Ringing Bob -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F3 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000





Johnston, et al.          Expires July 27, 2007               [Page 133]

Internet-Draft            SIP Service Examples              January 2007


      F4 ACK Alice -> Bob

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 1 ACK
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Length: 0


      /*   Bob REFERs Park Server to establish session with A
           which replaces the established session between A and B.
           Note that there is no session established between B
           and the Park Server. */

      F5 REFER Bob -> Park Server

      REFER sips:park@server.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds9
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=02134
      To: Park Server <sips:park@server.example.com>
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 REFER
    <allOneLine>
      Refer-To: <sips:a8342043f@atlanta.example.com;gr?Replaces=
      12345601%40atlanta.example.com%3Bfrom-tag%3D314159
      %3Bto-tag%3D1234567&Require=replaces>
    </allOneLine>
      Referred-By: <sips:bob@biloxi.example.com>
      Contact: <sips:bob@client.biloxi.example.com>
      Content-Length: 0


      F6 202 Accepted Park Server -> Bob

      SIP/2.0 202 Accepted
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds9
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=02134
      To: Park Server <sips:park@server.example.com>;tag=56323



Johnston, et al.          Expires July 27, 2007               [Page 134]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: 4802029847@biloxi.example.com
      Contact: <sips:park@server.example.com>
      CSeq: 1 REFER
      Content-Length: 0


      F7 NOTIFY Park Server -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bT6
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      Max-Forwards: 70
      From: Park Server <sips:park@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 NOTIFY
      Event: refer
      Subscription-State: active;expires=60
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 100 Trying


      F8 200 OK Bob -> Park Server

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bT6
       ;received=192.0.2.103
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      From: Park Server <sips:park@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 1 NOTIFY
      Content-Length: 0


      /* Park Server places call to Alice to replace session
         between Alice and Bob. */

      F9 INVITE Park Server -> Alice

      INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
      Max-Forwards: 70
      From: <sips:park@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>



Johnston, et al.          Expires July 27, 2007               [Page 135]

Internet-Draft            SIP Service Examples              January 2007


      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Referred-By: <sips:bob@biloxi.example.com>
      Contact: <sips:park@server.example.com>;automaton
          ;+sip.byeless;+sip.rendering="no"
      Require: replaces
      Replaces: 12345601@atlanta.example.com
       ;from-tag=314159;to-tag=1234567
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=ParkServer 2890844576 2890844576 IN IP4 Park.server.example.com
      s=
      c=IN IP4 server.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F10 200 OK Alice -> Park Server

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
       ;received=192.0.2.103
      From: <sips:park@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000
      a=recvonly





Johnston, et al.          Expires July 27, 2007               [Page 136]

Internet-Draft            SIP Service Examples              January 2007


      F11 ACK Park Server -> Alice

      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK7rfF
      Max-Forwards: 70
      From: <sips:park@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F12 BYE Alice -> Bob

      BYE sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      F13 200 OK Bob -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 12345601@atlanta.example.com
      CSeq: 2 BYE
      Content-Length: 0


      /*  Park Server reports success back to Bob by returning
           a 200 OK response.  Bob obtains the dialog identifiers
           from the headers included in the response. */

      F14 NOTIFY Park Server -> Bob

      NOTIFY sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bf9



Johnston, et al.          Expires July 27, 2007               [Page 137]

Internet-Draft            SIP Service Examples              January 2007


      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      Max-Forwards: 70
      From: Park Server <sips:park@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 2 NOTIFY
      Event: refer
      Subscription-State: terminated;reason=noresource
      Content-Type: message/sipfrag
      Content-Length: ...

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74rf
       ;received=192.0.2.103
      From: <sips:park@server.example.com>;tag=0111
      To: <sips:a8342043f@atlanta.example.com;gr>;tag=098594
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>


      F15 200 OK Bob -> Park Server

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS server.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      To: Bob <sips:bob@biloxi.example.com>;tag=02134
      From: Park Server <sips:park@server.example.com>;tag=56323
      Call-ID: 4802029847@biloxi.example.com
      CSeq: 2 NOTIFY
      Content-Length: 0


      /*  Alice is now parked at the Park Server */

      /* Carol picks up the call by sending an INVITE to A which
         replaces the existing session with the Park/Park Server.
         Carol needs to know the dialog information to construct
         the Replaces header. */

      F16 INVITE Carol -> Alice

      INVITE sips:alice@atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client.chicago.example.com:5061
       ;branch=z9hG4bK74bQ2
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=5893461



Johnston, et al.          Expires July 27, 2007               [Page 138]

Internet-Draft            SIP Service Examples              January 2007


      To: Alice <sips:alice@atlanta.example.com>
      Call-ID: 6485356@chicago.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Require: replaces
      Replaces: a5-75-34-12-76@server.example.com
       ;to-tag=098594;from-tag=0111
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
       SUBSCRIBE, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F17 200 OK Alice -> Carol

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.chicago.example.com:5061
       ;branch=z9hG4bK74bQ2
       ;received=192.0.2.105
      From: Carol <sips:carol@chicago.example.com>;tag=5893461
      To: Alice <sips:alice@atlanta.example.com>;tag=222
      Call-ID: 6485356@chicago.example.com
      CSeq: 1 INVITE
      Contact: <sips:a8342043f@atlanta.example.com;gr>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
      Supported: replaces, gruu
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=alice 2890844527 2890844527 IN IP4 client.atlanta.example.com
      s=
      c=IN IP4 client.atlanta.example.com
      t=0 0
      m=audio 49170 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F18 ACK Carol -> Alice



Johnston, et al.          Expires July 27, 2007               [Page 139]

Internet-Draft            SIP Service Examples              January 2007


      ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
      Via: SIP/2.0/TLS client.chicago.example.com:5061
       ;branch=z9hG4bK74bJ0
      Max-Forwards: 70
      From: Carol <sips:carol@chicago.example.com>;tag=5893461
      To: Alice <sips:alice@atlanta.example.com>;tag=222
      Call-ID: 6485356@chicago.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* A replaces the session to the Park Server with the new
         session with C and generates a BYE to disconnect the
         Park Server. */

      F19 BYE Alice -> Park Server

      BYE sips:park@server.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4N
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=098594
      To: <sips:park@server.example.com>;tag=0111
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F20 200 OK Park Server -> Alice

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4N
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=098594
      To: <sips:park@server.example.com>;tag=0111
      Call-ID: a5-75-34-12-76@server.example.com
      CSeq: 1 BYE
      Content-Length: 0












Johnston, et al.          Expires July 27, 2007               [Page 140]

Internet-Draft            SIP Service Examples              January 2007


2.16.  Call Pickup


            Alice          Bob                Bill
             |              |                   |
             |   INVITE F1  |                   |
             |------------->|                   |
             |180 Ringing F2|                   |
             |<-------------|                   |
             |              |   SUBSCRIBE F3    |
             |              |<------------------|
             |              |     200 OK F4     |
             |              |------------------>|
             |              |     NOTIFY F5     |
             |              |------------------>|
             |              |     200 OK F6     |
             |              |<------------------|
             |          INVITE Replaces:Bob  F7 |
             |<---------------------------------|
             |              |     200 OK F8     |
             |--------------------------------->|
             |   CANCEL F9  |                   |
             |------------->|                   |
             |  200 OK F10  |                   |
             |<-------------|                   |
             |    487 F11   |                   |
             |<-------------|                   |
             |    ACK F12   |                   |
             |------------->|                   |
             |                    ACK F13       |
             |<---------------------------------|
             |                                  |
             |    Two way RTP Established       |
             |<================================>|
             |                     BYE F14      |
             |--------------------------------->|
             |                   200 OK F15     |
             |<---------------------------------|
             |                                  |

   Bob and Bill are part of a work group at example.com that can pick up
   each other's calls.  Alice calls Bob who does not answer.  Bill
   wishes to pick up the call and sends a SUBSCRIBE to Bob to retrieve
   the dialog information.  Bill then generates an INVITE with a
   Replaces to Alice.  Alice answers the INVITE and sends a CANCEL to
   stop Bob's phone ringing.  Note that the relative order of the 487/
   ACK sequence (F11/F12) and the 200 OK to the CANCEL (F10) is not
   deterministic.



Johnston, et al.          Expires July 27, 2007               [Page 141]

Internet-Draft            SIP Service Examples              January 2007


   This call flow shows the use of the "early-only" parameter [4] in the
   Replaces header field of F7.  This parameter prevents Alice from
   accepting the INVITE if Bob has already accepted the INVITE.  If Bill
   had wished to "take" the call from Bob regardless of whether he had
   answered, the parameter would not have been present in F7.

   Also note that the subscription between Bob and Carol could have been
   established prior to Alice's call.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:a8342043f@atlanta.example.com;gr>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces, gruu
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:bob@client.biloxi.example.com>



Johnston, et al.          Expires July 27, 2007               [Page 142]

Internet-Draft            SIP Service Examples              January 2007


   Content-Length: 0


   /*   Bill decides to pick up the call. */

   F3 SUBSCRIBE  Bill -> Bob

   SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS pc.biloxi.example.com:5061
    ;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Bill <sips:bill@biloxi.example.com>;tag=8675309
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 SUBSCRIBE
   Contact: <sips:bill@pc.biloxi.example.com>
   Event: dialog
   Expires: 0
   Accept: application/dialog-info+xml
   Content-Length: 0


   F4 200 OK Bob -> Bill

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS pc.biloxi.example.com:5061
    ;branch=z9hG4bK74bf
    ;received=192.0.2.114
   Max-Forwards: 70
   From: Bill <sips:bill@biloxi.example.com>;tag=8675309
   To: Bob <sips:bob@biloxi.example.com>;tag=31451098
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 SUBSCRIBE
   Content-Length: 0


   F5 NOTIFY  Bob -> Bill

   NOTIFY sips:bill@pc.biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74br
   Max-Forwards: 70
   From: Bob <sips:bob@biloxi.example.com>;tag=31451098
   To: Bill <sips:bill@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 NOTIFY
   Contact: <sips:bob@client.biloxi.example.com>
   Event: dialog



Johnston, et al.          Expires July 27, 2007               [Page 143]

Internet-Draft            SIP Service Examples              January 2007


   Subscription-State: terminated;reason=timeout
   Content-Type: application/dialog-info+xml
   Content-Length: ...

   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
          version="0" state="full" entity="sips:bob@biloxi.example.com">
      <dialog id="94992014524" call-id="12345600@atlanta.example.com"
          local-tag="3145678" remote-tag="1234567"
                                              direction="recipient">
        <duration>1</duration>
        <local>
          <identity display="Bob">sips:bob@biloxi.example.com</identity>
          <target>sips:bob@client.biloxi.example.com</target>
        </local>
        <remote>
          <identity display="Alice">sips:alice@atlanta.example.com
                                                          </identity>
          <target>sips:a8342043@atlanta.example.com</target>
        </remote>
        <state>early</state>
      </dialog>
    </dialog-info>


   F6 200 OK  Bill -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74br
    ;received=192.0.2.105
   From: Bob <sips:bob@biloxi.example.com>;tag=31451098
   To: Bill <sips:bill@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 NOTIFY
   Contact: <sips:bill@pc.biloxi.example.com>
   Content-Length: 0


   F7 INVITE  Bill -> Alice

   INVITE sips:a8342043f@atlanta.example.com;gr SIP/2.0
   Via: SIP/2.0/TLS pc.biloxi.example.com:5061
    ;branch=z9hG4bK74HH
   Max-Forwards: 70
   From: Bill <sips:bill@biloxi.example.com>;tag=8675310
   To: Alice <sips:alice@atlanta.example.com>
   Call-ID: 563456212@b2.biloxi.example.com



Johnston, et al.          Expires July 27, 2007               [Page 144]

Internet-Draft            SIP Service Examples              January 2007


   CSeq: 1 INVITE
   Require: replaces
   Replaces: 12345600@atlanta.example.com
    ;from-tag=314578;to-tag=1234567;early-only
   Contact: <sips:bill@pc.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bill 2890843122 2890843122 IN IP4 pc.biloxi.example.com
   s=
   c=IN IP4 pc.biloxi.example.com
   t=0 0
   m=audio 5342 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   /* Alice matches the dialog information in the Replaces header
      and accepts the INVITE. */

   F8 200 OK  Alice -> Bill

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS pc.biloxi.example.com:5061
    ;branch=z9hG4bK74HH
    ;received=192.0.2.114
   From: Bill <sips:bill@biloxi.example.com>;tag=8675310
   To: Alice <sips:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sips:a8342043f@atlanta.example.com;gr>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces, gruu
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 289084543 289084543 IN IP4 client.atlanta.example.com
   s=
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   /* Alice stops Bob's phone from ringing by sending a CANCEL */



Johnston, et al.          Expires July 27, 2007               [Page 145]

Internet-Draft            SIP Service Examples              January 2007


   F9 CANCEL Alice -> Bob

   CANCEL sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F10 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F11 487 Request Terminated Bob -> Alice

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F12 ACK Alice -> Bob

   ACK sips:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.          Expires July 27, 2007               [Page 146]

Internet-Draft            SIP Service Examples              January 2007


   CSeq: 1 ACK
   Content-Length: 0


   F13 ACK  Bill -> Alice

   ACK sips:a8342043f@atlanta.example.com;gr SIP/2.0
   Via: SIP/2.0/TLS pc.biloxi.example.com:5061
    ;branch=z9hG4bK7435
   Max-Forwards: 70
   From: Bill <sips:bill@biloxi.example.com>;tag=8675310
   To: Alice <sips:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0


   /* RTP streams are established between Alice and Bill.
      Later, Alice Hangs Up with Bob. */

   F14 BYE Alice -> Bill

   BYE sips:bill@pc.biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf2
   Max-Forwards: 70
   To: Bill <sips:bill@biloxi.example.com>;tag=8675310
   From: Alice <sips:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F15 200 OK Bill -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf2
    ;received=192.0.2.105
   To: Bill <sips:bill@biloxi.example.com>;tag=8675310
   From: Alice <sips:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq:  1 BYE
   Content-Length: 0


2.17.  Automatic Redial




Johnston, et al.          Expires July 27, 2007               [Page 147]

Internet-Draft            SIP Service Examples              January 2007


           Alice             Bob
             |                |
             |    INVITE F1   |
             |--------------->|
             |486 Busy Here F2|
             |<---------------|    Bob is busy
             |     ACK F3     |
             |--------------->|
             |  SUBSCRIBE F4  |
             |--------------->|
             |   200 OK F5    |
             |<---------------|
             |    NOTIFY F6   |
             |<---------------|
             |   200 OK F7    |
             |--------------->|
             |                |
             |    NOTIFY F8   |    Bob is now available
             |<---------------|
             |   200 OK F9    |
             |--------------->|
             |                |
             |   INVITE F10   |
             |--------------->|   Session setup successfully
             | 180 Ringing F11|
             |<---------------|
             |   200 OK F12   |
             |<---------------|
             |     ACK F13    |
             |--------------->|
             |  Media Session |
             |<==============>|
             |                |
             |   NOTIFY F14   |
             |<---------------|
             |   200 OK F15   |
             |--------------->|
             |                |
             |  SUBSCRIBE F16 | Alice terminates subscription
             |--------------->|
             |   200 OK F17   |
             |<---------------|
             |   NOTIFY F18   |
             |<---------------|
             |   200 OK F19   |
             |--------------->|
             |                |




Johnston, et al.          Expires July 27, 2007               [Page 148]

Internet-Draft            SIP Service Examples              January 2007


   Bob is initially busy when Alice calls.  Alice subscribes to Bob's
   call state using a SUBSCRIBE F4.  Bob sends a NOTIFY F8 when Bob is
   available.  Alice is alerted, then Alice sends an INVITE to Bob to
   establish the session.  The subscription is terminated using
   SUBSCRIBE F16.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:alice@client.atlanta.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 486 Busy Here

   SIP/2.0 486 Busy Here
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=982039i4
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F3 ACK Alice -> Bob



Johnston, et al.          Expires July 27, 2007               [Page 149]

Internet-Draft            SIP Service Examples              January 2007


   ACK sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=1234567
   To: Bob <sips:bob@biloxi.example.com>;tag=982039i4
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F4 SUBSCRIBE Alice -> Bob

   SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74b8G
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=837348234
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 SUBSCRIBE
   Contact: sips:alice@client.atlanta.example.com
   Event: dialog
   Accept: application/dialog-info+xml
   Content-Length: 0


   F5 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74b8G
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=837348234
   To: Bob <sips:bob@biloxi.example.com>;tag=341123
   Call-ID: 4524526232@atlanta.example.com
   Expires: 60
   CSeq: 1 SUBSCRIBE
   Contact: sips:bob@client.biloxi.example.com
   Content-Length: 0


   F6 NOTIFY Bob -> Alice

   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74bn2
   Max-Forwards: 70



Johnston, et al.          Expires July 27, 2007               [Page 150]

Internet-Draft            SIP Service Examples              January 2007


   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 NOTIFY
   Contact: <sips:bob@client.biloxi.example.com>
   Event: dialog
   Subscription-State: active;expires=59
   Content-Type: application/dialog-info+xml
   Content-Length: ...

   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
          version="0" state="full" entity="sips:bob@biloxi.example.com">
      <dialog id="562623442g3">
         <duration>1</duration>
        <state>confirmed</state>
      </dialog>
    </dialog-info>


   F7 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74bn2
    ;received=192.0.2.105
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0


   /*   Bob is now available. */

   F8 NOTIFY Bob -> Alice

   NOTIFY sips:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74bVi
   Max-Forwards: 70
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 2 NOTIFY
   Event: dialog
   Subscription-State: active;expires=27
   Content-Type: application/dialog-info+xml



Johnston, et al.          Expires July 27, 2007               [Page 151]

Internet-Draft            SIP Service Examples              January 2007


   Content-Length: ...

   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
          version="0" state="full" entity="sips:bob@biloxi.example.com">
      <dialog id="562623442g3">
        <state>terminated</state>
      </dialog>
   </dialog-info>


   F9 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK74bVi
    ;received=192.0.2.105
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 2 NOTIFY
   Content-Length: 0


   F10 INVITE Alice -> Bob

   INVITE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bfq
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sips:bob@biloxi.example.com>
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:alice@client.atlanta.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844826 2890844826 IN IP4 client.atlanta.example.com
   s=
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000




Johnston, et al.          Expires July 27, 2007               [Page 152]

Internet-Draft            SIP Service Examples              January 2007


   F11 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bfq
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sips:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:bob@client.biloxi.example.com>
   Content-Length: 0


   F12 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bfq
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sips:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sips:bob@client.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890854527 2890854527 IN IP4 client.biloxi.example.com
   s=
   c=IN IP4 client.biloxi.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F13 ACK Alice -> Bob

   ACK sips:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK74bLBJ
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sips:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com



Johnston, et al.          Expires July 27, 2007               [Page 153]

Internet-Draft            SIP Service Examples              January 2007


   CSeq: 1 ACK
   Content-Length: 0


   F14 NOTIFY Bob -> Alice

   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK4bnd2
   Max-Forwards: 70
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 3 NOTIFY
   Contact: <sips:bob@client.biloxi.example.com>
   Event: dialog
   Subscription-State: active;expires=15
   Content-Type: application/dialog-info+xml
   Content-Length: ...

   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
          version="0" state="full" entity="sips:bob@biloxi.example.com">
      <dialog id="62d2623442g3">
         <duration>1</duration>
        <state>confirmed</state>
      </dialog>
    </dialog-info>


   F15 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bK4bnd2
    ;received=192.0.2.105
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 3 NOTIFY
   Content-Length: 0


   /* Alice terminates the subscription */

   F16 SUBSCRIBE Alice -> Bob

   SUBSCRIBE sips:bob@client.biloxi.example.com SIP/2.0



Johnston, et al.          Expires July 27, 2007               [Page 154]

Internet-Draft            SIP Service Examples              January 2007


   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK474b8
   Max-Forwards: 70
   From: Alice <sips:alice@atlanta.example.com>;tag=837348234
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 2 SUBSCRIBE
   Contact: sips:alice@client.atlanta.example.com
   Event: dialog
   Expires: 0
   Accept: application/dialog-info+xml
   Content-Length: 0


   F17 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.atlanta.example.com:5061
    ;branch=z9hG4bK474b8
    ;received=192.0.2.103
   From: Alice <sips:alice@atlanta.example.com>;tag=837348234
   To: Bob <sips:bob@biloxi.example.com>;tag=341123
   Call-ID: 4524526232@atlanta.example.com
   Expires: 0
   CSeq: 2 SUBSCRIBE
   Contact: sips:bob@client.biloxi.example.com
   Content-Length: 0


   F18 NOTIFY Bob -> Alice

   NOTIFY sips:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bKb5n2j
   Max-Forwards: 70
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 4 NOTIFY
   Contact: <sips:bob@client.biloxi.example.com>
   Event: dialog
   Subscription-State: terminated;reason=noresource
   Content-Type: application/dialog-info+xml
   Content-Length: ...

   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
          version="0" state="full" entity="sips:bob@biloxi.example.com">



Johnston, et al.          Expires July 27, 2007               [Page 155]

Internet-Draft            SIP Service Examples              January 2007


      <dialog id="62d2623442g3">
         <duration>3</duration>
        <state>confirmed</state>
      </dialog>
    </dialog-info>


   F19 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.biloxi.example.com:5061
    ;branch=z9hG4bKb5n2j
    ;received=192.0.2.105
   From: Bob <sips:bob@biloxi.example.com>;tag=341123
   To: Alice <sips:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 4 NOTIFY
   Content-Length: 0



2.18.  Click to Dial


        Bob's PC                Bob                Carol
            | REFER Refer-To:Carol F1                 |
            |------------------->|                    |
            |  202 Accepted F2   |                    |
            |<-------------------|                    |
            |                    |     INVITE F3      |
            |                    |------------------->|
            |                    |   180 Ringing F4   |
            |                    |<-------------------|
            |                    |     200 OK F5      |
            |                    |<-------------------|
            |                    |       ACK F6       |
            |                    |------------------->|
            |                    |         RTP        |
            |                    |<==================>|
            |                    |                    |

   In this example, while browsing the web on his PC, Bob clicks on
   Carol's SIP URI intending to establish a session with Carol.  Bob's
   web browser passes the SIP URI to the SIP client on Bob's PC.  The PC
   client is configured with the URI of Bob's SIP phone.  A REFER is
   sent to the SIP phone which results in the establishment of the
   session between Bob and Carol.




Johnston, et al.          Expires July 27, 2007               [Page 156]

Internet-Draft            SIP Service Examples              January 2007


   Note that Bob's PC requests that no REFER dialog be established by
   the use of the Refer-Sub: false header field [16].

   This flow is preferable to the 3pcc flow because the end-to-end SIP
   signaling is not interrupted by the 3pcc controller, and because
   Bob's experience of the call will not be marred by the lack of
   ringback tone or possible clipping.  Suitable authorization of the
   REFER and explicit authorization of the triggered INVITE by Bob is
   necessary.

   Message Details

   /* Bob's PC SIP Client sends a REFER to Bob's SIP phone */


      F1 REFER PC -> Bob

      REFER sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS pc.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
      Max-Forwards: 70
      From: <sips:pc.biloxi.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 1234560183434
      CSeq: 1 REFER
      Refer-To: <sips:carol@chicago.example.com>
      Refer-Sub: false
      Contact: <sips:pc.biloxi.example.com>
      Content-Length: 0


      F2 202 Accepted Bob -> PC

      SIP/2.0 202 Accepted
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.103
      From: <sips:pc.biloxi.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314159
      Call-ID: 1234560183434
      Contact: <sips:bob@client.biloxi.example.com>
      CSeq: 1 REFER
      Refer-Sub: false
      Content-Length: 0


      F3 INVITE Bob -> Carol




Johnston, et al.          Expires July 27, 2007               [Page 157]

Internet-Draft            SIP Service Examples              January 2007


      INVITE sips:carol@chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdK9
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client.biloxi.example.com>
      Referred-By: <sips:pc.biloxi.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=bob 2890844539 2890844539 IN IP4 client.biloxi.example.com
      s=
      c=IN IP4 client.biloxi.example.com
      t=0 0
      m=audio 3458 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F4 180 Ringing Carol -> Bob

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdK9
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:carol@client.chicago.example.com>
      Content-Length: 0


      F5 200 OK Carol -> Bob

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashdK9
       ;received=192.0.2.113
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 INVITE



Johnston, et al.          Expires July 27, 2007               [Page 158]

Internet-Draft            SIP Service Examples              January 2007


      Contact: <sips:carol@client.chicago.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Supported: replaces
      Content-Type: application/sdp
      Content-Length: ...

      v=0
      o=carol 2890844527 2890844527 IN IP4 client.chicago.example.com
      s=
      c=IN IP4 client.chicago.example.com
      t=0 0
      m=audio 3456 RTP/AVP 0
      a=rtpmap:0 PCMU/8000


      F6 ACK Bob -> Carol

      ACK sips:carol@client.chicago.example.com SIP/2.0
      Via: SIP/2.0/TLS client.biloxi.example.com:5061
       ;branch=z9hG4bKnashd43
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=8675309
      To: Carol <sips:carol@chicago.example.com>;tag=928287
      Call-ID: 7436222@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      /* Bob and Carol now have established a session. */


3.  Security Considerations

   Since many of the examples in this document involve SIP call control,
   either peer-to-peer or 3pcc, the security considerations in the
   Multiparty Framework document [12] apply.

   Many of the services shown in this document rely on a particular user
   agent being part of a group.  Members of a group could be, for
   example, employees within a particular department, a set of home
   phone extensions, members of a call center, etc.  As such, user
   agents which are part of the group permit other group members special
   privileges and features.  For example, while a user agent may not in
   general allow another user agent to learn detailed dialog
   information, this information might be shared with another group
   member in order to facilitate a service such as call pickup.  Group
   members must be authenticated using normal SIP means such as
   certificates or shared secrets.



Johnston, et al.          Expires July 27, 2007               [Page 159]

Internet-Draft            SIP Service Examples              January 2007


   The service examples in this document make extensive use of the SIP
   call control primitives REFER, Replaces, Join, and the dialog
   package.  The security considerations associated with each of these
   extensions apply to the scenarios in this document.


4.  IANA Considerations

   None.


5.  Acknowledgements

   The authors would like to thank the following reviewers of the
   document for their detailed comments and corrections: Vijay Gurbani,
   John Elwell, Joel Repiquet, Nagesh Kumar, Chandra Ravipati, Eric
   Burger, Jeroen Bemmel, Miguel Garcia, and Dale Worley.

   The Transfer - Instant Messaging call flow is based on the "IM-a-
   call" call flow by Jonathan Rosenberg and Henning Schulzrinne.  The
   Automatic Call Back call flow is based on a call flow by Adam Roach.
   The authors wish to thank the following individuals for their
   assistance and review of this call flows document: Joel Repiquet, Aki
   Neimi, Rohan Mahy, Jonathan Rosenberg, Hemant Agrawal, Henry
   Sinnreich, Dean Willis, David Devanatham, Joe Pizzimenti, Matt
   Cannon, John Hearty, the whole MCI WorldCom IPOP Design team, Scott
   Orton, Greg Osterhout, Pat Sollee, Doug Weisenberg, Danny Mistry,
   Steve McKinnon, and Denise Ingram, Denise Caballero, Tom Redman, Ilya
   Slain, Pat Sollee, John Truetken, and others from MCI WorldCom, 3Com,
   Cisco, Lucent and Nortel.


6.  References

6.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [3]   Sparks, R., "The Session Initiation Protocol (SIP) Refer
         Method", RFC 3515, April 2003.

   [4]   Mahy, R., Biggs, B., and R. Dean, "The Session Initiation
         Protocol (SIP) "Replaces" Header", RFC 3891, September 2004.



Johnston, et al.          Expires July 27, 2007               [Page 160]

Internet-Draft            SIP Service Examples              January 2007


   [5]   Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
         Session Description Protocol (SDP)", RFC 3264, June 2002.

   [6]   Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [7]   Sparks, R., "Session Initiation Protocol Call Control -
         Transfer", draft-ietf-sipping-cc-transfer-07 (work in
         progress), October 2006.

   [8]   Rosenberg, J., Schulzrinne, H., and R. Mahy, "An INVITE-
         Initiated Dialog Event Package for the Session Initiation
         Protocol (SIP)", RFC 4235, November 2005.

   [9]   Mahy, R. and D. Petrie, "The Session Initiation Protocol (SIP)
         "Join" Header", RFC 3911, October 2004.

   [10]  Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating
         User Agent Capabilities in the Session Initiation Protocol
         (SIP)", RFC 3840, August 2004.

   [11]  Johnston, A. and O. Levin, "Session Initiation Protocol (SIP)
         Call Control - Conferencing for User Agents", BCP 119,
         RFC 4579, August 2006.

   [12]  Mahy, R., "A Call Control and Multi-party usage framework for
         the Session Initiation  Protocol (SIP)",
         draft-ietf-sipping-cc-framework-06 (work in progress),
         March 2006.

   [13]  Campbell, B. and R. Sparks, "Control of Service Context using
         SIP Request-URI", RFC 3087, April 2001.

   [14]  Sparks, R., "Internet Media Type message/sipfrag", RFC 3420,
         November 2002.

   [15]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and
         D. Gurle, "Session Initiation Protocol (SIP) Extension for
         Instant Messaging", RFC 3428, December 2002.

   [16]  Levin, O., "Suppression of Session Initiation Protocol (SIP)
         REFER Method Implicit Subscription", RFC 4488, May 2006.

   [17]  Sparks, R., Hawrylyshen, A., Johnston, A., Rosenberg, J., and
         H. Schulzrinne, "Session Initiation Protocol (SIP) Torture Test
         Messages", RFC 4475, May 2006.





Johnston, et al.          Expires July 27, 2007               [Page 161]

Internet-Draft            SIP Service Examples              January 2007


6.2.  Informative References

   [18]  Johnston, A., Donovan, S., Sparks, R., Cunningham, C., and K.
         Summers, "Session Initiation Protocol (SIP) Basic Call Flow
         Examples", BCP 75, RFC 3665, December 2003.

   [19]  Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo,
         "Best Current Practices for Third Party Call Control (3pcc) in
         the Session Initiation Protocol (SIP)", BCP 85, RFC 3725,
         April 2004.

   [20]  Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
         Initiation Protocol (SIP) Event Package for Conference State",
         RFC 4575, August 2006.

   [21]  Rosenberg, J., "A Session Initiation Protocol (SIP) Event
         Package for Registrations", RFC 3680, March 2004.

   [22]  Rosenberg, J., "Obtaining and Using Globally Routable User
         Agent (UA) URIs (GRUU) in the  Session Initiation Protocol
         (SIP)", draft-ietf-sip-gruu-11 (work in progress),
         October 2006.

   [23]  Johnston, A. and R. Sparks, "Session Description Protocol (SDP)
         Offer/Answer Examples", RFC 4317, December 2005.


Authors' Addresses

   Alan Johnston (editor)
   Avaya
   St. Louis, MO  63124

   Email: alan@sipstation.com


   Robert J. Sparks
   Estacado Systems

   Email: RjS@estacado.net


   Chris Cunningham
   Cisco Systems

   Email: chrcunni@cisco.com





Johnston, et al.          Expires July 27, 2007               [Page 162]

Internet-Draft            SIP Service Examples              January 2007


   Steve Donovan
   Cisco Systems

   Email: srd@cisco.com


   Kevin Summers
   Prodea Systems
   Plano, TX  75093

   Email: kevin.summers@prodeasystems.com








































Johnston, et al.          Expires July 27, 2007               [Page 163]

Internet-Draft            SIP Service Examples              January 2007


Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Johnston, et al.          Expires July 27, 2007               [Page 164]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/