[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
Internet-Draft                                                  WorldCom
Expires: August 2, 2003                                        R. Sparks
                                                           C. Cunningham
                                                              S. Donovan
                                                             dynamicsoft
                                                              K. Summers
                                                                   Sonus
                                                           February 2003


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

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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 August 2, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This informational document gives examples of Session Initiation
   Protocol (SIP) services.  This covers most features offered in
   so-called Centrex offerings from local exchange carriers and PBX
   (Private Branch Exchange) features.  Most of the services shown in
   this document are implemented in the SIP User Agents, although some
   require the assistance of a SIP Proxy.  Some require some extensions
   to SIP including the REFER, SUBSCRIBE, and NOTIFY methods and the



Johnston, et al.         Expires August 2, 2003                 [Page 1]

Internet-Draft            SIP Service Examples             February 2003


   Replaces and Join headers. 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
   1.1  Legend for Message Flows . . . . . . . . . . . . . . . . . .   4
   2.   Service Examples . . . . . . . . . . . . . . . . . . . . . .   4
   2.1  Call Hold  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.2  Consultation Hold  . . . . . . . . . . . . . . . . . . . . .  15
   2.3  Music On Hold  . . . . . . . . . . . . . . . . . . . . . . .  31
   2.4  Unattended Transfer  . . . . . . . . . . . . . . . . . . . .  38
   2.5  Attended Transfer  . . . . . . . . . . . . . . . . . . . . .  45
   2.6  Call Forwarding Unconditional  . . . . . . . . . . . . . . .  58
   2.7  Call Forwarding - Busy . . . . . . . . . . . . . . . . . . .  64
   2.8  Call Forwarding - No Answer  . . . . . . . . . . . . . . . .  70
   2.9  3-way Conference – Third Party is Added  . . . . . . . . . .  79
   2.10 3-way Conference – Third Party Joins . . . . . . . . . . . .  85
   2.11 Single Line Extension  . . . . . . . . . . . . . . . . . . .  90
   2.12 Find-Me  . . . . . . . . . . . . . . . . . . . . . . . . . . 107
   2.13 Call Management (Incoming Call Screening)  . . . . . . . . . 118
   2.14 Call Management (Outgoing Call Screening)  . . . . . . . . . 122
   2.15 Call Park  . . . . . . . . . . . . . . . . . . . . . . . . . 125
   2.16 Call Pickup  . . . . . . . . . . . . . . . . . . . . . . . . 133
   2.17 Automatic Redial . . . . . . . . . . . . . . . . . . . . . . 140
   2.18 Click to Dial  . . . . . . . . . . . . . . . . . . . . . . . 147
   3.   Security Considerations  . . . . . . . . . . . . . . . . . . 150
   4.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 150
   5.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 150
   6.   Document History . . . . . . . . . . . . . . . . . . . . . . 151
   6.1  Changes since -03  . . . . . . . . . . . . . . . . . . . . . 151
        Informative References . . . . . . . . . . . . . . . . . . . 151
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 152
        Intellectual Property and Copyright Statements . . . . . . . 154















Johnston, et al.         Expires August 2, 2003                 [Page 2]

Internet-Draft            SIP Service Examples             February 2003


1. Overview

   This informational document provides 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
         Single-Line Extension         3-way Call
         Incoming Call Screening       Find-Me
         Call Pickup                   Call Park
         Outgoing Call Screening       Automatic Redial
         Click to Dial

   It is the hope of the authors that this document will be useful for
   SIP implementors, users, designers, and protocol researchers alike
   and will help further the goal of a standard SIP implementation for
   IP Telephony.  It is envisioned that as changes to the standard and
   additional RFCs are added that this document will reflect those
   changes and represent the current state of a standard SIP IP
   Telephony implementation.

   These flows use SIP as defined by RFC 2543bis [2] and [8]. Note that
   this document is informational, and nothing stated here should be
   taken as normative.  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)
   or Back-to-Back User Agents (B2BUA) may be more appropriate in some
   circumstances.  The design and principles of these service examples
   are described in the the Multiparty Framework document [12].

   These flows assume the functionality described in the SIP Call Flow
   Examples document [3], which explores basic behavior and PSTN
   internetworking. Some of the scenarios described herein make use of
   the SIP method extension REFER [4] and the SIP header extension
   Replaces [5], the SIP header extension Join [6], and some of the
   concepts in the 3pcc (third party call control) document [7].  The
   SIP Events document [11] describes the use of SUBSCRIBE and NOTIFY
   while the SIP Call Package document [10] describes the dialog event
   package.

   These flows were prepared assuming a network of proxies, registrars,
   PSTN gateways, and other SIP servers that have a pre-established
   trust relationship with each other, secured through other means than
   SIP. User agents wishing to use the services in this network are



Johnston, et al.         Expires August 2, 2003                 [Page 3]

Internet-Draft            SIP Service Examples             February 2003


   required to authenticate themselves with an edge proxy using SIP
   Digest. To improve the clarity of this document, authentication of
   User Agents is not explicitly shown in all flows, except where
   authentication directly relates to the service example.

   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 or PSTN
   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.
   Comments in the message details are shown in the following form:

   /* Comments. */

2. Service Examples

2.1 Call Hold


         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    |



Johnston, et al.         Expires August 2, 2003                 [Page 4]

Internet-Draft            SIP Service Examples             February 2003


          |                |------------->|
          |    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  |<-------------|
          |<---------------|              |
          |                |              |

   Alice calls Bob, then places the call on hold. Bob then takes call
   off hold.  Alice hangs up call.  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.

   Message Details


   F1 INVITE Alice -> Proxy 1

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345601@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                 [Page 5]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 INVITE Proxy 1 -> Bob

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE



Johnston, et al.         Expires August 2, 2003                 [Page 6]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: 0


   F4 180 Ringing Bob -> Proxy 1

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content Length:0


   F5 180 Ringing Proxy 1 -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content Length: 0


   F6 200 OK Bob -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...



Johnston, et al.         Expires August 2, 2003                 [Page 7]

Internet-Draft            SIP Service Examples             February 2003


   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 ACK Alice -> Proxy 1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F9 ACK Proxy 1 -> Bob

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



Johnston, et al.         Expires August 2, 2003                 [Page 8]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   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 sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly


   F11 INVITE Proxy 1 -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567



Johnston, et al.         Expires August 2, 2003                 [Page 9]

Internet-Draft            SIP Service Examples             February 2003


   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly


   /* A replies to hold */

   F12 200 OK Alice -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7



Johnston, et al.         Expires August 2, 2003                [Page 10]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly

   F14 ACK Bob -> Proxy 1

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F15 ACK Proxy 1 -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   /*   Bob takes the call off hold */




Johnston, et al.         Expires August 2, 2003                [Page 11]

Internet-Draft            SIP Service Examples             February 2003


   F16 INVITE Bob -> Proxy 1

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F17 INVITE Proxy 1 -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000





Johnston, et al.         Expires August 2, 2003                [Page 12]

Internet-Draft            SIP Service Examples             February 2003


   F18 200 OK Alice -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000





Johnston, et al.         Expires August 2, 2003                [Page 13]

Internet-Draft            SIP Service Examples             February 2003


   F20 ACK Bob -> Proxy 1

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 ACK
   Content-Length: 0


   F21 ACK Proxy 1 -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 ACK
   Content-Length: 0


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

   F22 BYE Alice -> Proxy 1

   BYE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F23 BYE Proxy 1 -> Bob

   BYE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103



Johnston, et al.         Expires August 2, 2003                [Page 14]

Internet-Draft            SIP Service Examples             February 2003


   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 |              |                   |



Johnston, et al.         Expires August 2, 2003                [Page 15]

Internet-Draft            SIP Service Examples             February 2003


          |<---------------|  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     |
          |                |--------------------------------->|
          |                |(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 |                   |
          |                |------------->|                   |



Johnston, et al.         Expires August 2, 2003                [Page 16]

Internet-Draft            SIP Service Examples             February 2003


          |                |   INVITE F29 |                   |
          |    INVITE F30  |<-------------|                   |
          |<---------------|              |                   |
          |    200 OK F31  |              |                   |
          |--------------->|   200 OK F32 |                   |
          |                |------------->|                   |
          |                |     ACK F33  |                   |
          |                |<-------------|                   |
          |    ACK F34     |              |                   |
          |<---------------|              |                   |
          |     Both way RTP Established  |                   |
          |<=============================>|                   |
          |    BYE F35     |              |                   |
          |--------------->|    BYE F36   |                   |
          |                |------------->|                   |
          |                |   200 OK F37 |                   |
          |                |<-------------|                   |
          |  200 OK F38    |              |                   |
          |<---------------|              |                   |
          |                |              |                   |

   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 Bob hangs up.

   Message Details


   F1 INVITE Alice -> Proxy 1

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000



Johnston, et al.         Expires August 2, 2003                [Page 17]

Internet-Draft            SIP Service Examples             February 2003


   F2 INVITE Proxy 1 -> Bob

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F4 180 Ringing Bob -> Proxy 1

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 18]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content Length:0


   F5 180 Ringing Proxy 1 -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content Length: 0


   F6 200 OK Bob -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9



Johnston, et al.         Expires August 2, 2003                [Page 19]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 ACK Alice -> Proxy 1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F9 ACK Proxy 1 -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   /* Bob  places  Alice on hold. */




Johnston, et al.         Expires August 2, 2003                [Page 20]

Internet-Draft            SIP Service Examples             February 2003


   F10 INVITE Bob -> Proxy 1

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly


   F11 INVITE Proxy 1 -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly



Johnston, et al.         Expires August 2, 2003                [Page 21]

Internet-Draft            SIP Service Examples             February 2003


   F12 200 OK Alice -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly



Johnston, et al.         Expires August 2, 2003                [Page 22]

Internet-Draft            SIP Service Examples             February 2003


   F14 ACK Bob -> Proxy 1

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F15 ACK Proxy 1 -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F16 INVITE Bob -> Proxy 1

   INVITE sip:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 50170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000




Johnston, et al.         Expires August 2, 2003                [Page 23]

Internet-Draft            SIP Service Examples             February 2003


   F17 INVITE Proxy 1 -> Carol

   INVITE sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844834 2890844834 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F19 180 Ringing Carol -> Proxy 1

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 24]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content Length:0


   F20 180 Ringing Proxy 1 -> Bob

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=client.chicago.example.com
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content Length: 0


   F21 200 OK Carol -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
   s=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7



Johnston, et al.         Expires August 2, 2003                [Page 25]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
   s=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F23 ACK Bob -> Proxy 1

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F24 ACK Proxy 1 -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F25 BYE Bob -> Proxy 1




Johnston, et al.         Expires August 2, 2003                [Page 26]

Internet-Draft            SIP Service Examples             February 2003


   BYE sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F26 BYE Proxy 1 -> Carol

   BYE sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=456654
   Call-ID: 9876543210@biloxi.example.com
   CSeq: 2 BYE



Johnston, et al.         Expires August 2, 2003                [Page 27]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: 0


   /* Bob  takes the call off hold */

   F29 INVITE Bob -> Proxy 1

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F30 INVITE Proxy 1 -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com



Johnston, et al.         Expires August 2, 2003                [Page 28]

Internet-Draft            SIP Service Examples             February 2003


   t=3034423619 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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Record-Route: <sip:ss1.example.com;lr>
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 29]

Internet-Draft            SIP Service Examples             February 2003


   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F33 ACK Bob -> Proxy 1

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 ACK
   Content-Length: 0


   F34 ACK Proxy 1 -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 ACK
   Content-Length: 0


   F35 BYE Alice -> Proxy 1

   BYE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F36 BYE Proxy 1 -> Bob

   BYE sip:bob@client.biloxi.example.com SIP/2.0



Johnston, et al.         Expires August 2, 2003                [Page 30]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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
          |                |              |
          |    INVITE F1   |              |
          |--------------->|              |
          | 180 Ringing F2 |              |
          |<---------------|              |
          |    200 OK F3   |              |
          |<---------------|              |



Johnston, et al.         Expires August 2, 2003                [Page 31]

Internet-Draft            SIP Service Examples             February 2003


          |     ACK F4     |              |
          |--------------->|              |
          |       RTP      |              |
          |<==============>|              |
          |                |              |
          | B places A on hold with music |
          |                |              |
          |                | INVITE no sdp F5
          |                |------------->|
          |                |200 OK sdpM F6|
          |                |<-------------|
          |INVITE (hold) F7|              |
          |<---------------|              |
          | 200 OK sdpA F8 |              |
          |--------------->|              |
          |     ACK F9     |              |
          |<---------------|              |
          |                | ACK sdpA F10 |
          |                |------------->|
          |               RTP             |
          |<==============================|
          |                |              |
          |    B Picks up the Call        |
          |                |    BYE F11   |
          |                |------------->|
          |                | 200 OK F12   |
          |                |<-------------|
          |    INVITE F13  |              |
          |<---------------|              |
          |    200 OK F14  |              |
          |--------------->|              |

          |     ACK F15    |              |
          |<---------------|              |
          |       RTP      |              |
          |<==============>|              |

   In this flow,B places A on hold with music. This is performed by B
   acting as a B2BUA (Back-to-Back User Agent) using 3pcc (third party
   call control) [7] to INVITE a Music Server into the session, which
   sends RTP music to A.  B picks the call up from hold by sending a BYE
   to the music server and taking A off of hold.

   Note that if A responds to the INVITE with hold SDP with hold SDP in
   the 200 OK, this call flow will not work properly.

   Note also that A will receive RTP packets from two different IP
   addresses during this call flow.



Johnston, et al.         Expires August 2, 2003                [Page 32]

Internet-Draft            SIP Service Examples             February 2003


   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>



Johnston, et al.         Expires August 2, 2003                [Page 33]

Internet-Draft            SIP Service Examples             February 2003


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

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   /* Bob  places A on hold with music by acting as a B2BUA and sending an INVITE to the Music Server  */

   F5 INVITE Bob -> Music Server

   INVITE sip:music@server.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Music <sip:music@server.example.com>
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F6 200 OK Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Music <sip:music@server.example.com>;tag=90210
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 1 INVITE



Johnston, et al.         Expires August 2, 2003                [Page 34]

Internet-Draft            SIP Service Examples             February 2003


   Contact: <sip:music@server.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=MusicServer 2890844576 2890844577 IN IP4 music.server.example.com
   s=Session SDP
   c=IN IP4 music.server.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly

   /* B re-INVITEs A on hold */

   F7 INVITE Bob -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844528 IN IP4 music.server.example.com
   s=Session SDP
   c=IN IP4 music.server.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly


   F8 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.atlanta.example.com>



Johnston, et al.         Expires August 2, 2003                [Page 35]

Internet-Draft            SIP Service Examples             February 2003


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

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly


   F9 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   /* B passes SDP of A to the Music Server to allow music to be sent from B to A */

   F10 ACK Bob -> Music Server

   ACK sip:music@server.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Music <sip:music@server.example.com>;tag=90210
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 1 ACK
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly




Johnston, et al.         Expires August 2, 2003                [Page 36]

Internet-Draft            SIP Service Examples             February 2003


   /* RTP music is now sent from the Music Server to A */

   /* B picks up the call from the Music Server */

   F11 BYE Bob -> Music Server

   BYE sip:music@server.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Music <sip:music@server.example.com>;tag=90210
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F12 200 OK Music Server -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Music <sip:music@server.example.com>;tag=90210
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 2 BYE
   Content-Length:0


   /* B re-INVITEs taking A off hold */

   F13 INVITE Bob -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844529 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0



Johnston, et al.         Expires August 2, 2003                [Page 37]

Internet-Draft            SIP Service Examples             February 2003


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


   F14 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:bob@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844528 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F15 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 ACK
   Content-Length: 0


   /* Normal media session between A and B is resumed */






2.4 Unattended Transfer





Johnston, et al.         Expires August 2, 2003                [Page 38]

Internet-Draft            SIP Service Examples             February 2003


       Alice                 Bob                 Carol
         |      INVITE F1     |                    |
         |<-------------------|                    |
         |   180 Ringing F2   |                    |
         |------------------->|                    |
         |      200 OK F3     |                    |
         |------------------->|                    |
         |        ACK F4      |                    |
         |<-------------------|                    |
         |        RTP         |                    |
         |<==================>|                    |
         |                    |                    |
         |  A 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 F14    |                    |
         |<-------------------|                    |
         |      200 OK F15    |                    |
         |------------------->|                    |
         |                    |                    |


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



Johnston, et al.         Expires August 2, 2003                [Page 39]

Internet-Draft            SIP Service Examples             February 2003


   Note that the BYE could be sent by Alice after the NOTIFY.  Also, if
   Alice has flushed all state information, the NOTIFY may receive a 481
   Call Leg Does Not Exist.

   Message Details

   F1 INVITE Bob -> Alice

   INVITE sip:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Length: 0


   F3 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113



Johnston, et al.         Expires August 2, 2003                [Page 40]

Internet-Draft            SIP Service Examples             February 2003


   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


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

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

   F5 REFER Alice -> Bob

   REFER sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 REFER
   Refer-To: <sip:carol@chicago.example.com>
   Referred-By: <alice@atlanta.example.com>
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Length: 0



Johnston, et al.         Expires August 2, 2003                [Page 41]

Internet-Draft            SIP Service Examples             February 2003


   F6 202 Accepted Bob -> Alice

   SIP/2.0 202 Accepted
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 REFER
   Content-Length: 0


   F7 NOTIFY Bob -> Alice

   NOTIFY sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip: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


   F8 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip: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 sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7



Johnston, et al.         Expires August 2, 2003                [Page 42]

Internet-Draft            SIP Service Examples             February 2003


   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 3 BYE
   Content-Length: 0


   F10 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 3 BYE
   Content-Length: 0


   /* Bob attempts the transfer to Carol */

   F11 INVITE Bob -> Carol

   INVITE sip:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423821 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F12 180 Ringing Carol -> Bob



Johnston, et al.         Expires August 2, 2003                [Page 43]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=928287
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content-Length: 0


   F13 200 OK Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=928287
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F14 ACK Bob -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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. */



Johnston, et al.         Expires August 2, 2003                [Page 44]

Internet-Draft            SIP Service Examples             February 2003


   F15 NOTIFY Bob -> Alice

   NOTIFY sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip: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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=928287
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 3 NOTIFY
   Content-Length: 0




2.5 Attended Transfer


        Alice             Bob          Carol
          |                |              |
          |    INVITE F1   |              |
          |--------------->|              |
          | 180 Ringing F2 |              |
          |<---------------|              |



Johnston, et al.         Expires August 2, 2003                [Page 45]

Internet-Draft            SIP Service Examples             February 2003


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



Johnston, et al.         Expires August 2, 2003                [Page 46]

Internet-Draft            SIP Service Examples             February 2003


          |                |  200 OK F23  |
          |                |------------->|
          |   NOTIFY F24   |              |
          |--------------->|              |
          |   200 OK F25   |              |
          |<---------------|              |
          |    BYE F26     |              |
          |<---------------|              |
          |   200 OK F27   |              |
          |--------------->|              |

   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 [5] is inserted into the Refer-To URL by Bob.  Note that the
   Refer-To URI is the Contact URI returned by Carol in the 200 OK
   response F10.  This ensures that only the correct instance of Carol
   is reached.  If the triggered INVITE had failed, Bob would have
   retried 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 [9].

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0



Johnston, et al.         Expires August 2, 2003                [Page 47]

Internet-Draft            SIP Service Examples             February 2003


   a=rtpmap:0 PCMU/8000


   F2 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 48]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 ACK
   Content-Length: 0


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

   F5 INVITE Bob -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1024 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1024 INVITE
   Contact: <sip: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



Johnston, et al.         Expires August 2, 2003                [Page 49]

Internet-Draft            SIP Service Examples             February 2003


   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly


   F7 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip: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 sip:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423645 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F9 180 Ringing Carol -> Bob




Johnston, et al.         Expires August 2, 2003                [Page 50]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content-Length: 0


   F10 200 OK Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F11 ACK Bob -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 ACK
   Content-Length: 0


   /* Bob  puts Carol on hold */



Johnston, et al.         Expires August 2, 2003                [Page 51]

Internet-Draft            SIP Service Examples             February 2003


   F12 INVITE Bob -> Carol

   INVITE sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 43 INVITE
   Contact: <sip: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 289084834 2890844835 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423645 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 43 INVITE
   Contact: <sip: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 2890844923 IN IP4 client.chicago.example.com
   s=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly



Johnston, et al.         Expires August 2, 2003                [Page 52]

Internet-Draft            SIP Service Examples             February 2003


   F14 ACK Bob -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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 sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431

   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 1025 REFER
   Refer-To: <sip:carol@client.chicago.example.com?Replaces=
    sdjfdjfskdf@biloxi.example.com%3Bto-tag%3D5f35a3%3Bfrom-tag%3D8675309>
   Referred-By: <sip:bob@biloxi.example.com>
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F16 202 Accepted Alice -> Bob

   SIP/2.0 202 Accepted
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=1234567
   To: Alice <sip:alice@atlanta.example.com>;tag=23431
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 1025 REFER
   Content-Length: 0


   F17 NOTIFY Alice -> Bob

   NOTIFY sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70



Johnston, et al.         Expires August 2, 2003                [Page 53]

Internet-Draft            SIP Service Examples             February 2003


   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 2 NOTIFY
   Event: refer
   Subscription-State: active;expires=60
   Content-Type: message/sipfrag
   Content-Length: ...

   SIP/2.0 100 Trying


   F18 200 OK Bob -> Carol

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=1234567
   From: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: 12345678900@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 sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bKadfe4ko
   To: Carol <sip:carol@client.chicago.example.com>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=3461
   Call-ID: 9435674543@atlanta.example.com
   CSeq: 1 INVITE
   Referred-By: <sip:bob@biloxi.example.com>
   Replaces: 12345600@atlanta.example.com;to-tag=23431;from-tag=8675309
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423643 0



Johnston, et al.         Expires August 2, 2003                [Page 54]

Internet-Draft            SIP Service Examples             February 2003


   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/UDP chicago.example.com:5060;branch=z9hG4bKadfe4ko
    ;received=192.0.2.123
   To: Carol <sip:carol@client.chicago.example.com>;tag=ff3a
   From: Alice <sip:alice@atlanta.example.com>;tag=3461
   Call-ID: 9435674543@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844221 2890844221 IN IP4 client.chicago.example.com
   s=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423452 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F21 ACK Alice -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bKadfe4ko
   To: Carol <sip:carol@client.chicago.example.com>;tag=ff3a
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=3461
   Call-ID: 9435674543@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   /* Carol then disconnects from Bob */

   F22 BYE Carol -> Bob

   BYE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Bob <sip:bob@biloxi.example.com>;tag=8675309
   Max-Forwards: 70



Johnston, et al.         Expires August 2, 2003                [Page 55]

Internet-Draft            SIP Service Examples             February 2003


   From: Carol <sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=8675309
   From: Carol <sip: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 sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9

   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345678900@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/UDP chicago.example.com:5060;branch=z9hG4bKadfe4ko
    ;received=192.0.2.123
   From: Carol <sip:carol@chicago.example.com>;tag=ff3a
   To: Alice <sip:alice@atlanta.example.com>;tag=3461

   Call-ID: 9435674543@chicago.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>


   F25 200 OK Bob -> Carol




Johnston, et al.         Expires August 2, 2003                [Page 56]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=1234567
   From: Carol <sip:carol@chicago.example.com>;tag=5f35a3
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 3 NOTIFY
   Content-Length: 0


   /* Bob disconnects with  Alice */

   F26 BYE Bob -> Alice

   BYE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 1026 BYE
   Content-Length: 0


   F27 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345678900@atlanta.example.com
   CSeq: 1026 BYE
   Content-Length: 0

















Johnston, et al.         Expires August 2, 2003                [Page 57]

Internet-Draft            SIP Service Examples             February 2003


2.6 Call Forwarding Unconditional


         Alice           Proxy          Gateway
          |                |              |
          |    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   |
          |<=============================>|
          |     BYE F10    |              |
          |--------------->|   BYE F11    |
          |                |------------->|
          |                |   200 OK F12 |
          |    200 OK F13  |<-------------|
          |<---------------|              |
          |                |              |

   Bob wants all calls forwarded to the PSTN.   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.

   Message Details


   F1 INVITE Alice -> Proxy

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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



Johnston, et al.         Expires August 2, 2003                [Page 58]

Internet-Draft            SIP Service Examples             February 2003


   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


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

   F2 INVITE Proxy -> Gateway

   INVITE sip:+19727293660@gw1.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F4 180 Ringing Gateway -> Proxy




Johnston, et al.         Expires August 2, 2003                [Page 59]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:+19727293660@gw1.example.com;user=phone>
   Content Length:0


   F5 180 Ringing Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103

   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:+19727293660@gw1.example.com;user=phone>
   Content Length: 0


   F6 200 OK Gateway -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:+19727293660@gw1.example.com;user=phone>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=GATEWAY1 2890844527 2890844527 IN IP4 gatewayone.example.com
   s=Session SDP



Johnston, et al.         Expires August 2, 2003                [Page 60]

Internet-Draft            SIP Service Examples             February 2003


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


   F7 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:+19727293660@gw1.example.com;user=phone>
   Content-Type: application/sdp
   Content-Length: ...

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


   F8 ACK Alice -> Proxy

   ACK sip:+19727293660@gw1.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F9 ACK Proxy -> Gateway

   ACK sip:+19727293660@gw1.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103



Johnston, et al.         Expires August 2, 2003                [Page 61]

Internet-Draft            SIP Service Examples             February 2003


   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F10 BYE Alice -> Proxy 1

   BYE sip:+19727293660@gw1.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:+19727293660@gw1.example.com;user=phone>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F11 BYE Proxy 1 -> Gateway

   BYE sip:+19727293660@gw1.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F12 200 OK Gateway -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0




Johnston, et al.         Expires August 2, 2003                [Page 62]

Internet-Draft            SIP Service Examples             February 2003


   F13 200 OK Proxy 1 -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345600@atlanta.example.com
   CSeq:  2 BYE
   Content-Length: 0









































Johnston, et al.         Expires August 2, 2003                [Page 63]

Internet-Draft            SIP Service Examples             February 2003


2.7 Call Forwarding - Busy


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

   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 places call to B2.

   Message Details


   F1 INVITE Alice -> Proxy

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567



Johnston, et al.         Expires August 2, 2003                [Page 64]

Internet-Draft            SIP Service Examples             February 2003


   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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


   F2 INVITE Proxy -> Bob1

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>



Johnston, et al.         Expires August 2, 2003                [Page 65]

Internet-Draft            SIP Service Examples             February 2003


   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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F5 ACK Proxy -> Bob1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


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

   F6 INVITE Proxy -> Bob2

   INVITE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...



Johnston, et al.         Expires August 2, 2003                [Page 66]

Internet-Draft            SIP Service Examples             February 2003


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


   F7 180 Ringing B2 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Length: 0


   F8 180 Ringing Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Length: 0


   F9 200 OK B2 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567



Johnston, et al.         Expires August 2, 2003                [Page 67]

Internet-Draft            SIP Service Examples             February 2003


   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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


   F10 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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


   F11 ACK Alice -> Proxy

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 68]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 ACK
   Content-Length: 0


   F12 ACK Proxy -> Bob2

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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. */

   F13 BYE Alice -> Proxy

   BYE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F14 BYE Proxy -> Bob2

   BYE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0




Johnston, et al.         Expires August 2, 2003                [Page 69]

Internet-Draft            SIP Service Examples             February 2003


   F15 200 OK B2 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F16 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq:  2 BYE
   Content-Length: 0



2.8 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   |                   |
          |                |------------->|                   |



Johnston, et al.         Expires August 2, 2003                [Page 70]

Internet-Draft            SIP Service Examples             February 2003


          |                |              |    INVITE F10     |
          |                |--------------------------------->|
          |                |              | 180 Ringing F11   |
          | 180 Ringing F12|<---------------------------------|
          |<---------------|              |      200 OK F13   |
          |                |<---------------------------------|
          |   200 OK F14   |              |                   |
          |<---------------|              |                   |
          |     ACK F15    |              |                   |
          |--------------->|              |     ACK F16       |
          |                |--------------------------------->|
          |               Both way RTP Established            |
          |<=================================================>|
          |    BYE F17     |              |                   |
          |--------------->|              |      BYE F18      |
          |                |--------------------------------->|
          |                |              |    200 OK F19     |
          |  200 OK F20    |<---------------------------------|
          |<---------------|              |                   |
          |                |              |                   |

   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

   F1 INVITE Alice -> Proxy

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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 August 2, 2003                [Page 71]

Internet-Draft            SIP Service Examples             February 2003


   F2 INVITE Proxy -> Bob1

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 72]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F5 180 Ringing Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


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

   F6 CANCEL Proxy -> Bob1

   CANCEL sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   From: Alice <sip:alice@atlanta.example.com>
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F8 487 Request Terminated B1 -> Proxy




Johnston, et al.         Expires August 2, 2003                [Page 73]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F9 ACK Proxy -> Bob1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F10 INVITE Proxy -> Bob2

   INVITE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69

   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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 August 2, 2003                [Page 74]

Internet-Draft            SIP Service Examples             February 2003


   F11 180 Ringing B2 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Length: 0


   F12 180 Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Length: 0


   F13 200 OK B2 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com



Johnston, et al.         Expires August 2, 2003                [Page 75]

Internet-Draft            SIP Service Examples             February 2003


   s=Session SDP
   c=IN IP4 client2.biloxi.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F14 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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


   F15 ACK Alice -> Proxy

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F16 ACK Proxy -> Bob2

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9



Johnston, et al.         Expires August 2, 2003                [Page 76]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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. */

   F17 BYE Alice -> Proxy

   BYE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F18 BYE Proxy -> Bob2

   BYE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F19 200 OK B2 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 77]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 2 BYE
   Content-Length: 0


   F20 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq:  2 BYE
   Content-Length: 0





































Johnston, et al.         Expires August 2, 2003                [Page 78]

Internet-Draft            SIP Service Examples             February 2003


2.9 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 A's mixer.  B then
   INVITEs Carol using the same Contact URI.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 79]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com



Johnston, et al.         Expires August 2, 2003                [Page 80]

Internet-Draft            SIP Service Examples             February 2003


   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1024 INVITE
   Contact: <sip:bob-Mixer@client.biloxi.example.com>
   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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=sendonly


   F6 200 OK Alice -> Bob

   SIP/2.0 200 OK



Johnston, et al.         Expires August 2, 2003                [Page 81]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113

   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1024 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly


   F7 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip: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 sip:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip:bob-Mixer@client.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY



Johnston, et al.         Expires August 2, 2003                [Page 82]

Internet-Draft            SIP Service Examples             February 2003


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

   v=0
   o=bob 28908445834 2890844834 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423645 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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=341313
   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip: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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=341313

   Call-ID: sdjfdjfskdf@biloxi.example.com
   CSeq: 42 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.chicago.example.com



Johnston, et al.         Expires August 2, 2003                [Page 83]

Internet-Draft            SIP Service Examples             February 2003


   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F11 ACK Bob -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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 August 2, 2003                [Page 84]

Internet-Draft            SIP Service Examples             February 2003


2.10 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 conference URI 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 Bob's mixer then
   accepts the INVITE from Carol, resulting in the 3-way call.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9



Johnston, et al.         Expires August 2, 2003                [Page 85]

Internet-Draft            SIP Service Examples             February 2003


   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces, join
   Content-Type: application/sdp
   Content-Length: ...



Johnston, et al.         Expires August 2, 2003                [Page 86]

Internet-Draft            SIP Service Examples             February 2003


   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Carol <sip:carol@chicago.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 452k499sk@chicago.example.com
   CSeq: 99 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000




Johnston, et al.         Expires August 2, 2003                [Page 87]

Internet-Draft            SIP Service Examples             February 2003


   F6 180 Ringing Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bKnashds7
    ;received=120.
   From: Carol <sip:carol@chicago.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>;tag=0982
   Call-ID: 452k499sk@chicago.example.com
   CSeq: 99 INVITE
   Contact: <sip:bob-Mixer@client.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces
   Content-Length: 0


   F7 INVITE Bob -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1024 INVITE
   Contact: <sip:bob-Mixer@client.biloxi.example.com>
   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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=23431

   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003                [Page 88]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1024 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   F9 ACK Bob -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=23431
   To: Alice <sip: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/UDP chicago.example.com:5060;branch=z9hG4bKnashds7
    ;received=120.
   From: Carol <sip:carol@chicago.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>;tag=0982
   Call-ID: 452k499sk@chicago.example.com
   CSeq: 99 INVITE
   Contact: <sip:bob-Mixer@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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423645 0
   m=audio 48174 RTP/AVP 0



Johnston, et al.         Expires August 2, 2003                [Page 89]

Internet-Draft            SIP Service Examples             February 2003


   a=rtpmap:0 PCMU/8000


   F11 ACK OK Bob -> Carol

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Carol <sip:carol@chicago.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>;tag=0982
   Call-ID: 452k499sk@chicago.example.com
   CSeq: 99 ACK
   Content-Length:0



2.11 Single Line Extension


          Alice      Forking Proxy       User   User   User
                                          B1     B2     B3
          |                |              |      |      |
          |    INVITE F1   |              |      |      |
          |--------------->|   INVITE F2  |      |      |
          |                |------------->|      |      |
          |                |       INVITE F3     |      |
          |                |-------------------->|      |
          |                |          INVITE F4  |      |
          |                |--------------------------->|
          | 100 Trying F5  |              |      |      |
          |<---------------|180 Ringing F6|      |      |
          |                |<-------------|      |      |
          | 180 Ringing F7 |              |      |      |
          |<---------------|              |      |      |
          |                | 480 Not Logged In F8|      |
          |                |<--------------------|      |
          |                |              ACK F9 |      |
          |                |-------------------->|      |
          |                |         180 Ringing F10    |
          |     180 F11    |<---------------------------|
          |<---------------|            200 OK F12      |
          |   200 OK F13   |<---------------------------|
          |<---------------|              |      |      |
          |                |   CANCEL 14  |      |      |
          |                |------------->|      |      |
          |                |  200 OK F15  |      |      |
          |                |<-------------|      |      |
          |                |    487 F16   |      |      |



Johnston, et al.         Expires August 2, 2003                [Page 90]

Internet-Draft            SIP Service Examples             February 2003


          |                |<-------------|      |      |
          |                |    ACK F17   |      |      |
          |                |------------->|      |      |
          |     ACK F18    |              |      |      |
          |--------------->|           ACK F19   |      |
          |                |--------------------------->|
          |               Both way RTP Established      |
          |<===========================================>|
          |                |          NOTIFY F20        |
          |                |<---------------------------|
          |                |   NOTIFY F21 |      |      |
          |                |------------->|      |      |
          |                |       NOTIFY F22    |      |
          |                |-------------------->|      |
          |                |          NOTIFY F23 |      |
          |                |--------------------------->|
          |                |   200 OK F24 |      |      |
          |                |<-------------|      |      |
          |                |          200 OK F25        |
          |                |--------------------------->|
          |                |   200 OK F26 |      |
          |                |<--------------------|      |
          |                |     482 Loop Detected F27  |
          |                |<---------------------------|
          |                |                            |
          |         User B2 wants to join the call      |
          |                |                            |
          |                |   INVITE Join:A-B3 F28     |
          |                |<--------------------|      |
          |                |   INVITE Join: A-B3 F29    |
          |                |------------->|      |      |
          |                |      INVITE Join: A-B3 F30 |
          |                |-------------------->|      |
          |                |          INVITE Join: A-B3 F31
          |                |--------------------------->|
          |                |    100 Trying F32   |      |

          |                |-------------------->|      |
          |                | 481 Dialog Does Not Exist F33
          |                |<-------------|      |      |
          |                |     ACK F34  |      |      |
          |                |------------->|      |      |
          |                | 482 Loop Detected F35      |
          |                |<--------------------|      |
          |                |            ACK F36  |      |
          |                |-------------------->|      |
          |                |               200 OK F37   |
          |                |<---------------------------|



Johnston, et al.         Expires August 2, 2003                [Page 91]

Internet-Draft            SIP Service Examples             February 2003


          |                |          200 OK F38 |      |
          |                |-------------------->|      |
          |                |                     |ACK F39
          |                |                     |----->|
          |                |             Both way RTP Established
          |                |                     |<====>|  B3 mixes RTP
          |                |                     |      |

   In Single Line Extension a call will ring several extensions at the
   same time (forking).  The extension to answer the call becomes the
   active set.  If other extensions pick up, the call becomes a
   conference call.

   In this flow, Alice calls Bob which results in the INVITE being
   forked to three devices, B1, B2, and B3.  B3 answers the call and is
   connected to A.  B3 sends a NOTIFY containing the dialog information
   to B, which is forked to B1 and B2. B2 wishes to join the call and
   sends an INVITE with a Join header field to B to request this.  This
   INVITE is forked and is accepted by B3 who then performs the mixing
   function.

   Note that if B3 is not capable of mixing the media, B3 would transfer
   both Alice and B2 to a conferencing bridge which would perform the
   mixing.

   The use of SUBSCRIBE and NOTIFY is defined in [11] while the dialog
   Event package is defined in [10].

   Message Details


   F1 INVITE Alice -> Proxy

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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



Johnston, et al.         Expires August 2, 2003                [Page 92]

Internet-Draft            SIP Service Examples             February 2003


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


   F2 INVITE Proxy -> Bob1

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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


   F3 INVITE Proxy -> Bob2

   INVITE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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



Johnston, et al.         Expires August 2, 2003                [Page 93]

Internet-Draft            SIP Service Examples             February 2003


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


   F4 INVITE Proxy -> Bob3

   INVITE sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.3
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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






   F5 100 Trying Proxy -> Alice

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F6 180 Ringing B1 -> Proxy

   SIP/2.0 180 Ringing



Johnston, et al.         Expires August 2, 2003                [Page 94]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F7 180 Ringing Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F8 480 Not Logged In B2 -> Proxy

   SIP/2.0 480 Not Logged In
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314756
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F9 ACK Proxy -> Bob2

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314756
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK



Johnston, et al.         Expires August 2, 2003                [Page 95]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: 0


   F10 180 Ringing B3 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=83749.3
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client3.biloxi.example.com>
   Content-Length: 0


   F11 180 Ringing B3 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client3.biloxi.example.com>
   Content-Length: 0


   F12 200 OK B3 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=83749.3
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client3.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client3.biloxi.example.com



Johnston, et al.         Expires August 2, 2003                [Page 96]

Internet-Draft            SIP Service Examples             February 2003


   s=Session SDP
   c=IN IP4 client3.biloxi.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F13 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com.115>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client3.biloxi.example.com
   s=Session SDP
   c=IN IP4 client3.biloxi.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   /* Forking Proxy cancels pending branch B1 */

   F14 CANCEL Proxy -> Bob1

   CANCEL sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F15 200 OK B1 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54



Johnston, et al.         Expires August 2, 2003                [Page 97]

Internet-Draft            SIP Service Examples             February 2003


   From: Alice <sip:alice@atlanta.example.com>
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F16 487 Request Terminated B1 -> Proxy

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F17 ACK Proxy -> Bob1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F18 ACK Alice -> Proxy

   ACK sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F19 ACK Proxy -> Bob3

   ACK sip:bob@client3.biloxi.example.com SIP/2.0



Johnston, et al.         Expires August 2, 2003                [Page 98]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.3
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 B3*/

   /* User B3 sends a NOTIFY to the group with established dialog information. */

   F20 NOTIFY B3 -> Proxy

   NOTIFY sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Event: dialog
   Subscription-State: active;expires=3600
   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="partial" entity="sip:bob@biloxi.example.com">
   <dialog id="2393lds3204" call-id="12345600@atlanta.example.com"
      local-tag="7137136" remote-tag="1234567" direction="recipient">
   <state event="2xx">confirmed</state>
   </dialog>
   </dialog-info>


   F21 NOTIFY Proxy -> Bob1

   NOTIFY sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>



Johnston, et al.         Expires August 2, 2003                [Page 99]

Internet-Draft            SIP Service Examples             February 2003


   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Event: dialog
   Subscription-State: active;expires=3600
   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="partial" entity="sip:bob@biloxi.example.com">
   <dialog id="2393lds3204" call-id="12345600@atlanta.example.com"
      local-tag="7137136" remote-tag="1234567" direction="recipient">
   <state event="2xx">confirmed</state>
   </dialog>
   </dialog-info>


   F22 Proxy -> Bob2

   NOTIFY sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.2
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Event: dialog
   Subscription-State: active;expires=3600
   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="partial" entity="sip:bob@biloxi.example.com">
   <dialog id="2393lds3204" call-id="12345600@atlanta.example.com"
      local-tag="7137136" remote-tag="1234567" direction="recipient">
   <state event="2xx">confirmed</state>
   </dialog>
   </dialog-info>


   F23 NOTIFY Proxy-> Bob3

   NOTIFY sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk



Johnston, et al.         Expires August 2, 2003               [Page 100]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.115
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Event: dialog
   Subscription-State: active;expires=3600
   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="partial" entity="sip:bob@biloxi.example.com">
   <dialog id="2393lds3204" call-id="12345600@atlanta.example.com"
      local-tag="7137136" remote-tag="1234567" direction="recipient">
   <state event="2xx">confirmed</state>
   </dialog>
   </dialog-info>


   F24 200 OK B1 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0


   F25 200 OK Proxy -> Bob3

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0


   F26 200 OK B2 -> Proxy



Johnston, et al.         Expires August 2, 2003               [Page 101]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0


   F27 200 OK B3 -> Proxy

   SIP/2.0 482 Loop Detected
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.115
   From: Bob <sip:bob@biloxi.example.com>;tag=w2Hu8sj
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 8458999275@biloxi.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0


   /* User B2 decided to join the call.  */

   F28 INVITE B2 -> Proxy

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Join: 12345600@atlanta.example.com;to-tag=765432;from-tag=1234567
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
   s=Session SDP
   c=IN IP4 client2.biloxi.example.com
   t=0 0




Johnston, et al.         Expires August 2, 2003               [Page 102]

Internet-Draft            SIP Service Examples             February 2003


   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F29 INVITE Proxy -> Bob1

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Join: 12345600@atlanta.example.com;to-tag=765432;from-tag=1234567
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
   s=Session SDP
   c=IN IP4 client2.biloxi.example.com
   t=0 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F30 INVITE Proxy -> Bob2

   INVITE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.2
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Join: 12345600@atlanta.example.com;to-tag=765432;from-tag=1234567
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
   s=Session SDP



Johnston, et al.         Expires August 2, 2003               [Page 103]

Internet-Draft            SIP Service Examples             February 2003


   c=IN IP4 client2.biloxi.example.com
   t=0 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000



   F31 INVITE Proxy -> Bob1

   INVITE sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client2.biloxi.example.com>
   Join: 12345600@atlanta.example.com;to-tag=765432;from-tag=1234567
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client2.biloxi.example.com
   s=Session SDP
   c=IN IP4 client2.biloxi.example.com
   t=0 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F32 100 Trying Proxy -> Bob2

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
      From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   /* B1 does not have an established dialog, so it returns a 481 */

   F33 481 Dialog Does Not Exist B1 -> Proxy




Johnston, et al.         Expires August 2, 2003               [Page 104]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 481 Dialog Does Not Exist
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=68324lk42jd
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F34 ACK Proxy -> Bob1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=68324lk42jd
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F35 482 Loop Detected B2 -> Proxy

   SIP/2.0 482 Loop Detected
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=134lkwe
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F36 ACK Proxy -> Bob2

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.2
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=134lkwe
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0





Johnston, et al.         Expires August 2, 2003               [Page 105]

Internet-Draft            SIP Service Examples             February 2003


   /* B3 has an existing dialog and agrees to mix B2 into the session. */

   F37 200 OK User B3 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK4558a.3
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=3891908734
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client3.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client3.biloxi.example.com
   s=Session SDP
   c=IN IP4 client3.biloxi.example.com
   t=0 0
   m=audio 3460 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F38 200 OK User B3 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
    ;received=192.0.2.114
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=3891908734
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client3.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client3.biloxi.example.com
   s=Session SDP
   c=IN IP4 client3.biloxi.example.com
   t=0 0
   m=audio 3460 RTP/AVP 0
   a=rtpmap:0 PCMU/8000




Johnston, et al.         Expires August 2, 2003               [Page 106]

Internet-Draft            SIP Service Examples             February 2003


   F39 ACK B2 -> Bob3

   ACK sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKq0qwli6ewlk
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=4524524312
   To: Bob <sip:bob@biloxi.example.com>;tag=3891908734
   Call-ID: 524251233@biloxi.example.com
   CSeq: 1 ACK
   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  |      |      |      |
          |                |<-------------|      |      |      |
          |                |     487 F8   |      |      |      |
          |                |<-------------|      |      |      |
          |                |     ACK F9   |      |      |      |
          |                |------------->|      |      |      |
          |                |     INVITE F10      |      |      |
          |                |-------------------->|      |      |
          |                |480 Not Logged In F11|      |      |
          |                |<--------------------|      |      |
          |                |              ACK F12|      |      |
          |                |-------------------->|      |      |
          |                |          INVITE F13        |      |
          |                |--------------------------->|      |
          |                |      486 Busy Here F14     |      |
          |                |<---------------------------|      |
          |                |            ACK F15         |      |
          |                |--------------------------->|      |



Johnston, et al.         Expires August 2, 2003               [Page 107]

Internet-Draft            SIP Service Examples             February 2003


          |                |              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

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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



Johnston, et al.         Expires August 2, 2003               [Page 108]

Internet-Draft            SIP Service Examples             February 2003


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


   F2 INVITE Proxy -> Bob1

   INVITE sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9



Johnston, et al.         Expires August 2, 2003               [Page 109]

Internet-Draft            SIP Service Examples             February 2003


    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F5 180 Ringing Proxy -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


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

   F6 CANCEL Proxy -> Bob1

   CANCEL sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   From: Alice <sip:alice@atlanta.example.com>
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL



Johnston, et al.         Expires August 2, 2003               [Page 110]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: 0


   F8 487 Request Terminated B1 -> Proxy

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F9 ACK Proxy -> Bob1

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=765432
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F10 INVITE Proxy -> Bob2

   INVITE sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

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



Johnston, et al.         Expires August 2, 2003               [Page 111]

Internet-Draft            SIP Service Examples             February 2003


   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/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314756
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F12 ACK Proxy -> Bob2

   ACK sip:bob@client2.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.2
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314756
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F13 INVITE Proxy -> Bob3

   INVITE sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.3
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...




Johnston, et al.         Expires August 2, 2003               [Page 112]

Internet-Draft            SIP Service Examples             February 2003


   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   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/UDP ss1.example.com:5060;branch=z9hG4bK83749.3
    ;received=192.0.2.54
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F15 ACK Proxy -> Bob3

   ACK sip:bob@client3.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.3
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7654321
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F16 INVITE Proxy -> Bob4

   INVITE sip:bob@client4.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=83749.4
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...



Johnston, et al.         Expires August 2, 2003               [Page 113]

Internet-Draft            SIP Service Examples             February 2003


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


   F17 180 Ringing B4 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=83749.4
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client4.biloxi.example.com>
   Content-Length: 0


   F18 180 Ringing B4 -> Proxy

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client4.biloxi.example.com>
   Content-Length: 0


   F19 200 OK B4 -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=83749.4
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003               [Page 114]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip:bob@client4.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com
   s=Session SDP
   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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Record-Route: <sip:ss1.example.com;lr>
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136

   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com.116>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client4.biloxi.example.com
   s=Session SDP
   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 sip:bob@client4.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7137136
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK



Johnston, et al.         Expires August 2, 2003               [Page 115]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: 0


   F22 ACK Proxy -> Bob4

   ACK sip:bob@client4.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   Max-Forwards: 69
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Route: <sip:ss1.example.com;lr>
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=7137136
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F24 BYE Proxy -> Alice

   BYE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   Max-Forwards: 69
   From: Bob <sip:bob@biloxi.example.com>;tag=7137136
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 BYE
   Content-Length: 0





Johnston, et al.         Expires August 2, 2003               [Page 116]

Internet-Draft            SIP Service Examples             February 2003


   F25 200 OK Alice -> Proxy

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
    ;received=192.0.2.54
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=7137136
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F26 200 OK Proxy -> Bob4

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=7137136
   To: Alice <sip:alice@atlanta.example.com>;tag=1234567
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 BYE
   Content-Length: 0



























Johnston, et al.         Expires August 2, 2003               [Page 117]

Internet-Draft            SIP Service Examples             February 2003


2.13 Call Management (Incoming Call Screening)


        Alice           Proxy            Bob
          |                |              |
          |    INVITE F1   |              |
          |------------------------------>|


          | 305 Use Proxy F2              |
          |<------------------------------|
          |     ACK F3     |              |
          |------------------------------>|
          |    INVITE F4   |              |
          |--------------->|              |
          | 407 Proxy Authorization F5    |
          |<---------------|              |
          |     ACK F6     |              |
          |--------------->|              |
          |    INVITE F7   |              |
          |--------------->|              |
          | 403 Screening Failure (Terminating) F8
          |<---------------|              |
          |     ACK F9     |              |
          |--------------->|              |
          |                |              |

   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 user B.  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 –
   instead some form of authentication credentials must be used.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE



Johnston, et al.         Expires August 2, 2003               [Page 118]

Internet-Draft            SIP Service Examples             February 2003


   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=342123
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:ss1.example.com>
   Content-Length: 0


   F3 ACK Alice -> Bob

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70



Johnston, et al.         Expires August 2, 2003               [Page 119]

Internet-Draft            SIP Service Examples             February 2003


   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   /* Proxy 1 challenges  Alice for authentication */

   F5 407 Proxy Authorization Required Proxy 1 -> Alice

   SIP/2.0 407 Proxy Authorization Required
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=7886765
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Proxy-Authenticate: Digest realm="example.com",
    domain="sip:ss1.example.com", nonce="ea9c8e88df84f1cec4341ae6cbe5a359",
    opaque="", stale=FALSE, algorithm=MD5
   Content-Length: 0


   F6 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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.  */



Johnston, et al.         Expires August 2, 2003               [Page 120]

Internet-Draft            SIP Service Examples             February 2003


   F7 INVITE Alice -> Proxy 1

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 3 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Proxy-Authorization: Digest username="alice",
    realm="example.com", nonce="ae9137be1c87d175c2dd63302a0d6e0a",
    opaque="", uri="sip:bob@biloxi.example.com",
    response="bbaec39f943bdcb3620d90afc548a45c"
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=ffe254
   Call-ID: 12345600@atlanta.example.com
   CSeq: 3 INVITE
   Error-Info: <sip:screen-failure-term-ann@annoucement.company.com>
   Content-Length: 0


   F9 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=ffe254
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003               [Page 121]

Internet-Draft            SIP Service Examples             February 2003


   Proxy-Authorization: Digest username="alice",
    realm="example.com", nonce="ae9137be1c87d175c2dd63302a0d6e0a",
    opaque="", uri="sip:bob@biloxi.example.com",
    response="bbaec39f943bdcb3620d90afc548a45c"
   CSeq: 3 ACK
   Content-Length: 0



2.14 Call Management (Outgoing Call Screening)


        Alice            Proxy           Bob
          |                |              |
          |    INVITE F1   |              |
          |--------------->|              |
          | 407 Proxy Authorization 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.

   Message Details


   F1 INVITE Alice -> Proxy 1

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...




Johnston, et al.         Expires August 2, 2003               [Page 122]

Internet-Draft            SIP Service Examples             February 2003


   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   /* Proxy 1 challenges  Alice for authentication */

   F2 407 Proxy Authorization Required Proxy 1 -> Alice

   SIP/2.0 407 Proxy Authorization Required
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=90210
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Proxy-Authenticate: Digest realm="example.com",
    domain="sip:ss1.example.com", nonce="ea9c8e88df84f1cec4341ae6cbe5a359",
    opaque="", stale=FALSE, algorithm=MD5
   Content-Length: 0


   F3 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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 sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>



Johnston, et al.         Expires August 2, 2003               [Page 123]

Internet-Draft            SIP Service Examples             February 2003


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

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=18017
   Call-ID: 12345600@atlanta.example.com
   CSeq: 2 INVITE
   Error-Info: <sip:screen-failure-orig-ann@annoucement.company.com>
   Content-Length: 0


   F6 ACK Alice -> Proxy 1

   ACK sip:bob@biloxi.example.com SIP/2.0

   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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="sip:bob@biloxi.example.com",
    response="b9d2e5bcdec9f69ab2a9b44f270285a6"
   Content-Length: 0




Johnston, et al.         Expires August 2, 2003               [Page 124]

Internet-Draft            SIP Service Examples             February 2003


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                 |
          |<==========================================>|
          |           BYE F19           |              |



Johnston, et al.         Expires August 2, 2003               [Page 125]

Internet-Draft            SIP Service Examples             February 2003


          |---------------------------->|              |
          |          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 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 Call-ID in the application/sip body of the NOTIFY response.
   Carol wishes to retrieve the call, a new INVITE is sent to Alice
   which replaces the session with the Park Server.   Alice accepts the
   call and sends a BYE to the Park Server. Note that 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 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 sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000





Johnston, et al.         Expires August 2, 2003               [Page 126]

Internet-Draft            SIP Service Examples             February 2003


   F2 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 ACK
   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. */



Johnston, et al.         Expires August 2, 2003               [Page 127]

Internet-Draft            SIP Service Examples             February 2003


   F5 REFER Bob -> Park Server

   REFER sip:park@server.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=02134
   To: Park Server <sip:park@server.example.com>
   Call-ID: 4802029847@biloxi.example.com
   CSeq: 1 REFER
   Refer-To: <sip:alice@client.atlanta.example.com?Replaces=
    12345601@atlanta.example.com%3Bfrom-tag%3D314159%3Bto-tag%3D1234567>
   Referred-By: <sip:bob@biloxi.example.com>
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F6 202 Accepted Park Server -> Bob

   SIP/2.0 202 Accepted
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Bob <sip:bob@biloxi.example.com>;tag=02134
   To: Park Server <sip:park@server.example.com>;tag=56323
   Call-ID: 4802029847@biloxi.example.com
   CSeq: 1 REFER
   Content-Length: 0


   F7 NOTIFY Park Server -> Bob

   NOTIFY sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Bob <sip:bob@biloxi.example.com>;tag=02134
   Max-Forwards: 70
   From: Park Server <sip: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



Johnston, et al.         Expires August 2, 2003               [Page 128]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=02134
   From: Park Server <sip: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 sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP server.example.com:5060
   Max-Forwards: 70
   From: <sip:park@server.example.com>;tag=0111
   To: <sip:alice@client.atlanta.example.com>
   Call-ID: a5-75-34-12-76@server.example.com
   CSeq: 1 INVITE
   Referred-By: <sip:bob@biloxi.example.com>
   Contact: <sip:park@server.example.com>
   Replaces: 12345601@atlanta.example.com;from-tag=314159;to-tag=1234567

   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=ParkServer 2890844576 2890844576 IN IP4 Park.server.example.com
   s=Session SDP
   c=IN IP4 music.server.example.com
   t=3034423619 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/UDP music.server.example.com:5060
   From: <sip:park@server.example.com>;tag=0111
   To: Alice <sip:alice@client.atlanta.example.com>;tag=098594
   Call-ID: a5-75-34-12-76@server.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Supported: replaces
   Content-Type: application/sdp



Johnston, et al.         Expires August 2, 2003               [Page 129]

Internet-Draft            SIP Service Examples             February 2003


   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000
   a=recvonly


   F11 ACK Park Server -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP music.server.example.com:5060
   Max-Forwards: 70
   From: <sip:park@server.example.com>;tag=0111
   To: Alice <sip:alice@client.atlanta.example.com>;tag=098594
   Call-ID: a5-75-34-12-76@server.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F12 BYE Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.105
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 2 BYE
   Content-Length: 0





Johnston, et al.         Expires August 2, 2003               [Page 130]

Internet-Draft            SIP Service Examples             February 2003


   /*  Park Server reports success back to B by returning all the SIP headers in 200 OK response  */

   F14 NOTIFY Park Server -> Bob

   NOTIFY sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   To: Bob <sip:bob@biloxi.example.com>;tag=02134
   Max-Forwards: 70
   From: Park Server <sip:park@server.example.com>;tag=56323
   Call-ID: 4802029847@biloxi.example.com
   CSeq: 1 NOTIFY
   Event: refer
   Subscription-State: terminated;reason=noresource
   Content-Type: message/sipfrag
   Content-Length: ...

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP music.server.example.com:5060
   From: <sip:park@server.example.com>;tag=0111
   To: Alice <sip:alice@client.atlanta.example.com>;tag=098594
   Call-ID: a5-75-34-12-76@server.example.com

   CSeq: 2 INVITE
   Contact: <sip:alice@client.atlanta.example.com>


   F15 200 OK Bob -> Park Server

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=02134
   From: Park Server <sip: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 sip:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP chicago.example.com:5060;branch=z9hG4bK74bf9



Johnston, et al.         Expires August 2, 2003               [Page 131]

Internet-Draft            SIP Service Examples             February 2003


   Max-Forwards: 70
   From: Carol <sip:carol@chicago.example.com>;tag=5893461
   To: Alice <sip:alice@atlanta.example.com>
   Call-ID: 6485356@chicago.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Replaces: a5-75-34-12-76@server.example.com;from-tag=098594;to-tag=0111
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com
   s=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.105
   From: Carol <sip:carol@chicago.example.com>;tag=5893461
   To: Alice <sip:alice@atlanta.example.com>;tag=222
   Call-ID: 6485356@chicago.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844527 2890844527 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F18 ACK Carol -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70



Johnston, et al.         Expires August 2, 2003               [Page 132]

Internet-Draft            SIP Service Examples             February 2003


   From: Carol <sip:carol@chicago.example.com>;tag=5893461
   To: Alice <sip: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 sip:park@server.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=098594
   To: <sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=098594
   To: <sip:park@server.example.com>;tag=0111
   Call-ID: a5-75-34-12-76@server.example.com
   CSeq: 1 BYE
   Content-Length: 0



2.16 Call Pickup


         Alice          Bob                Carol
          |              |                   |
          |   INVITE F1  |                   |
          |------------->|                   |
          |180 Ringing F2|                   |
          |<-------------|                   |
          |              |   SUBSCRIBE F3    |
          |              |<------------------|
          |              |     200 OK F4     |
          |              |------------------>|
          |              |     NOTIFY F5     |



Johnston, et al.         Expires August 2, 2003               [Page 133]

Internet-Draft            SIP Service Examples             February 2003


          |              |------------------>|
          |              |     200 OK F6     |
          |              |<------------------|
          |          INVITE Replaces:Bob  F7 |
          |<---------------------------------|
          |              |     200 OK F8     |
          |--------------------------------->|
          |   CANCEL F9  |                   |
          |------------->|                   |
          |  200 OK F10  |                   |
          |<-------------|                   |
          |    487 F11   |                   |
          |<-------------|                   |
          |    ACK F12   |                   |
          |------------->|                   |
          |                    ACK F13       |
          |<---------------------------------|
          |              |     NOTIFY F14    |
          |              |------------------>|
          |              |       481 F15     |
          |              |<------------------|
          |                                  |
          |   Both way RTP Established       |
          |<================================>|
          |                     BYE F16      |
          |--------------------------------->|
          |                   200 OK F17     |
          |<---------------------------------|
          |                                  |

   Bob and Carol are part of a work group at example.com that can pick
   up each others calls.  Alice calls Bob who does not answer.  Carol
   wishes to pick up the call and sends a SUBSCRIBE to B to retrieve the
   dialog information.  Carol 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 order of the CANCEL/ACK sequence in F11
   through F20 is not significant.

   Message Details

   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com



Johnston, et al.         Expires August 2, 2003               [Page 134]

Internet-Draft            SIP Service Examples             February 2003


   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000



   F2 180 Ringing B1 -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@Bob.biloxi.example.com>
   Content-Length: 0


   /*   Carol decides to pick up the call */

   F3 SUBSCRIBE  Carol -> Bob

   SUBSCRIBE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP pc.biloxi.example.com:5060;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Carol <sip:carol@biloxi.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@pc.biloxi.example.com>
   Event: dialog
   Subscription-State: active;expires=3600
   Accept: application/dialog-info+xml
   Content-Length: 0





Johnston, et al.         Expires August 2, 2003               [Page 135]

Internet-Draft            SIP Service Examples             February 2003


   F4 200 OK Bob -> Carol

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP pc.biloxi.example.com:5060;branch=z9hG4bK74bf
    ;received=192.0.2.114
   Max-Forwards: 70
   From: Carol <sip:carol@biloxi.example.com>;tag=8675309
   To: Bob <sip:bob@biloxi.example.com>;tag=31451098
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F5 NOTIFY  Bob -> Carol

   NOTIFY sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP Bob.biloxi.example.com:5060;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=31451098
   To: Carol <sip:carol@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 NOTIFY
   Contact: <sip:carol@Bob.biloxi.example.com>
   Event: dialog
   Subscription-State: active;expires=3600
   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="sip:bob@biloxi.example.com">
   <dialog id="94992014524" call-id="12345600@atlanta.example.com"
      local-tag="3145678" remote-tag="1234567" direction="recipient"
      remote-uri="alice@atlanta.example.com">
   <state>early</state>
   </dialog>
   </dialog-info>

   F6 200 OK  Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP Bob.biloxi.example.com:5060;branch=z9hG4bK74bf
   From: Bob <sip:bob@biloxi.example.com>;tag=31451098
   To: Carol <sip:carol@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 1 NOTIFY
   Contact: <sip:carol@Bob.biloxi.example.com>
   Content-Length: 0



Johnston, et al.         Expires August 2, 2003               [Page 136]

Internet-Draft            SIP Service Examples             February 2003


   F7 INVITE  Carol -> Alice

   INVITE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP pc.biloxi.example.com:5060;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Carol <sip:carol@biloxi.example.com>;tag=8675309
   To: Alice <sip:alice@atlanta.example.com>
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 INVITE
   Replaces: 12345600@atlanta.example.com;to-tag=314578;from-tag=1234567
   Contact: <sip:bob@client2.biloxi.example.com>
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=bob 2890843122 2890843122 IN IP4 pc.biloxi.example.com
   s=Session SDP
   c=IN IP4 client2.biloxi.example.com
   t=3034423619 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/UDP pc.biloxi.example.com:5060;branch=z9hG4bK74bf
    ;received=192.0.2.114
   From: Carol <sip:carol@atlanta.example.com>;tag=8675309
   To: Alice <sip:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 INVITE
   Contact: <sip: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 289084543 289084543 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0



Johnston, et al.         Expires August 2, 2003               [Page 137]

Internet-Draft            SIP Service Examples             February 2003


   a=rtpmap:0 PCMU/8000



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

   F9 CANCEL Alice -> Bob

   CANCEL sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F11 487 Request Terminated Bob -> Proxy

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F12 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.example.com:5060;branch=z9hG4bK83749.1
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567



Johnston, et al.         Expires August 2, 2003               [Page 138]

Internet-Draft            SIP Service Examples             February 2003


   To: Bob <sip:bob@biloxi.example.com>;tag=3145678
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   Content-Length: 0

   F13 ACK  Carol -> Alice

   ACK sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP b2.biloxi.example.com:5060;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Alice <sip:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F14 NOTIFY  Bob -> Carol

   NOTIFY sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP Bob.biloxi.example.com:5060;branch=z9hG4bK74bf
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=31451098
   To: Carol <sip:carol@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 2 NOTIFY
   Contact: <sip:carol@Bob.biloxi.example.com>
   Event: dialog
   Subscription-State: active;expires=3600
   Content-Type: application/dialog-info+xml
   Content-Length: ...

      <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
      version="1" state="partial" entity="sip:bob@biloxi.example.com">
   <dialog id="94992014524" call-id="12345600@atlanta.example.com"
      local-tag="3145678" remote-tag="1234567" direction="recipient">
   <state>terminated</state>
   </dialog>
   </dialog-info>


   F15 481 Dialog Does Not Exist  Carol -> Bob

   SIP/2.0 481 Dialog Does Not Exist



Johnston, et al.         Expires August 2, 2003               [Page 139]

Internet-Draft            SIP Service Examples             February 2003


   Via: SIP/2.0/UDP bob.biloxi.example.com:5060;branch=z9hG4bK74bf
   From: Bob <sip:bob@biloxi.example.com>;tag=31451098
   To: Carol <sip:carol@biloxi.example.com>;tag=8675309
   Call-ID: rt4353gs2egg@pc.biloxi.example.com
   CSeq: 2 NOTIFY
   Contact: <sip:carol@bob.biloxi.example.com>
   Content-Length: 0



   /* RTP streams are established between Alice and Carol.     Alice Hangs Up with Bob. */

   F16 BYE Alice -> Proxy

   BYE sip:carol@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   To: Bob <sip:bob@biloxi.example.com>;tag=8675309
   From: Alice <sip:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F17 200 OK Carol -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   To: Bob <sip:bob@biloxi.example.com>;tag=8675309
   From: Alice <sip:alice@atlanta.example.com>;tag=131256
   Call-ID: 563456212@b2.biloxi.example.com
   CSeq:  2 BYE
   Content-Length: 0



2.17 Automatic Redial













Johnston, et al.         Expires August 2, 2003               [Page 140]

Internet-Draft            SIP Service Examples             February 2003


        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 |
          |<==============>|
          |                |

   Bob is initially busy when  Alice calls.   Alice subscribes to User
   B’s call state using a SUBSCRIBE F4.  Bob sends a NOTIFY F8 when
   Bob is available.  A is alerted, then Alice sends an INVITE to B to
   establish the session.

   Message Details


   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567



Johnston, et al.         Expires August 2, 2003               [Page 141]

Internet-Draft            SIP Service Examples             February 2003


   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=982039i4
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F3 ACK Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=1234567

   To: Bob <sip:bob@biloxi.example.com>;tag=982039i4
   Call-ID: 12345600@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F4 SUBSCRIBE Alice -> Bob

   SUBSCRIBE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=837348234
   To: Bob <sip:bob@biloxi.example.com>



Johnston, et al.         Expires August 2, 2003               [Page 142]

Internet-Draft            SIP Service Examples             February 2003


   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 SUBSCRIBE
   Contact: alice@client.atlanta.example.com
   Event: dialog
   Subscription-State: active;expires=3600
   Accept: application/dialog-info+xml
   Content-Length: 0


   F5 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   From: Alice <sip:alice@atlanta.example.com>;tag=837348234
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 SUBSCRIBE
   Contact: alice@client.biloxi.example.com
   Content-Length: 0


   F6 NOTIFY Bob -> Alice

   NOTIFY sip:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=341123
   To: Alice <sip:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 1 NOTIFY
   Event: dialog

   Subscription-State: active;expires=3600
   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="sip:bob@biloxi.example.com">

   <dialog id="562623442g3">
   <state>confirmed</state>
   </dialog>
   </dialog-info>


   F7 200 OK Alice -> Bob




Johnston, et al.         Expires August 2, 2003               [Page 143]

Internet-Draft            SIP Service Examples             February 2003


   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   From: Bob <sip:bob@biloxi.example.com>;tag=341123
   To: Alice <sip: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 sip:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=341123
   To: Alice <sip:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 2 NOTIFY
   Event: dialog
   Subscription-State: active;expires=3600
   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="sip: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/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   From: Bob <sip:bob@biloxi.example.com>;tag=341123
   To: Alice <sip:alice@atlanta.example.com>;tag=837348234
   Call-ID: 4524526232@atlanta.example.com
   CSeq: 2 NOTIFY
   Content-Length: 0


   <figure><artwork><![CDATA[
   Message Details




Johnston, et al.         Expires August 2, 2003               [Page 144]

Internet-Draft            SIP Service Examples             February 2003


   F10 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com>
   Content-Type: application/sdp
   Content-Length: ...

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=Session SDP
   c=IN IP4 client.atlanta.example.com
   t=3034423619 0
   m=audio 49170 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F11 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Length: 0


   F12 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.103
   From: Alice <sip:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com>
   Content-Type: application/sdp
   Content-Length: ...




Johnston, et al.         Expires August 2, 2003               [Page 145]

Internet-Draft            SIP Service Examples             February 2003


   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F13 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=f23fkg14k
   To: Bob <sip:bob@biloxi.example.com>;tag=23431
   Call-ID: aoij4i9okitr@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0
































Johnston, et al.         Expires August 2, 2003               [Page 146]

Internet-Draft            SIP Service Examples             February 2003


2.18 Click to Dial


     Bob's PC                Bob                Carol
         | REFER Refer-To:Carol F1                 |
         |------------------->|                    |
         |  202 Accepted F2   |                    |
         |<-------------------|                    |
         |      NOTIFY F3     |                    |
         |<-------------------|                    |
         |      200 OK F4     |                    |
         |------------------->|                    |
         |                    |     INVITE F5      |
         |                    |------------------->|
         |                    |   180 Ringing F6   |
         |                    |<-------------------|
         |                    |     200 OK F7      |
         |                    |<-------------------|
         |                    |       ACK F8       |
         |                    |------------------->|
         |                    |         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.

   Note that Bob's SIP phone immediately terminates the dialog by
   indicating in the NOTIFY (F3) that the subscription is terminated.

   Message Details

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

   F1 REFER PC -> Bob

   REFER sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/UDP pc.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: <sip:pc.biloxi.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 REFER



Johnston, et al.         Expires August 2, 2003               [Page 147]

Internet-Draft            SIP Service Examples             February 2003


   Refer-To: <sip:carol@chicago.example.com>
   Contact: <sip:pc.client.atlanta.example.com>
   Content-Length: 0


   F2 202 Accepted Bob -> PC

   SIP/2.0 202 Accepted
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: <sip:pc.biloxi.example.com>;tag=1234567
   To: Bob <sip:bob@biloxi.example.com>;tag=314159
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 REFER
   Content-Length: 0


   F3 NOTIFY Bob -> Alice

   NOTIFY sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: <sip:pc.biloxi.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 NOTIFY
   Event: refer
   Subscription-State: terminated;reason=noresource
   Content-Type: message/sipfrag
   Content-Length: ...

   SIP/2.0 100 Trying


   F4 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=314159
   To: <sip:pc.biloxi.example.com>;tag=1234567
   Call-ID: 12345601@atlanta.example.com
   CSeq: 1 NOTIFY
   Content-Length: 0







Johnston, et al.         Expires August 2, 2003               [Page 148]

Internet-Draft            SIP Service Examples             February 2003


   F5 INVITE Bob -> Carol

   INVITE sip:carol@chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip: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=Session SDP
   c=IN IP4 client.biloxi.example.com
   t=3034423821 0
   m=audio 3458 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F6 180 Ringing Carol -> Bob

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=928287
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>
   Content-Length: 0


   F7 200 OK Carol -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.113
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip:carol@chicago.example.com>;tag=928287
   Call-ID: 7436222@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:carol@client.chicago.example.com>



Johnston, et al.         Expires August 2, 2003               [Page 149]

Internet-Draft            SIP Service Examples             February 2003


   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=Session SDP
   c=IN IP4 client.chicago.example.com
   t=3034423619 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 ACK Bob -> Carol

   ACK sip:carol@client.chicago.example.com SIP/2.0
   Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8675309
   To: Carol <sip: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.

4. IANA Considerations

   None.

5. Acknowledgements

   The Automatic Call Back call flow is based on a call flow by Adam
   Roach.  The Single Line Extension call flow is based on a call flow
   by Jonathan Rosenberg.  The authors wish to thank the following
   individuals for their assistance and review of this call flows
   document: Rohan Mahey, Jonathan Rosenberg, Hemant Agrawal, Henry
   Sinnreich, Dean Willis, David Devanatham, Joe Pizzimenti,  Matt
   Cannon, John Hearty, the whole MCI WorldCom IPOP Design team, Scott



Johnston, et al.         Expires August 2, 2003               [Page 150]

Internet-Draft            SIP Service Examples             February 2003


   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. Document History

   The first version of this document was the Internet-Draft
   draft-sparks-sip-service-examples October 1999.

   The next version was combined with the SIP Telephony Call Flows
   document into the draft-ietf-sip-call-flows April 2000.

   The current version was renamed as a work item of the SIPPING WG.

6.1 Changes since -03


   - Added Click to Dial Call Flow

   - Changed URIs and display names

   - Added a=recvonly attribute in hold SDP answers

Informative References

   [1]   Bradner, S., "The Internet Standards Process -- Revision 3",
         BCP 9, RFC 2026, October 1996.

   [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]   Johnston, A., "Session Initiation Protocol Basic Call Flow
         Examples", draft-ietf-sipping-basic-call-flows-01 (work in
         progress), October 2002.

   [4]   Sparks, R., "The SIP Refer Method", draft-ietf-sip-refer-07
         (work in progress), December 2002.

   [5]   Dean, R., Biggs, B. and R. Mahy, "The Session Inititation
         Protocol (SIP) 'Replaces' Header", draft-ietf-sip-replaces-02
         (work in progress), May 2002.

   [6]   Mahy, R. and D. Petrie, "The Session Inititation Protocol (SIP)
         'Join' Header", draft-ietf-sip-join-00 (work in progress),
         October 2002.




Johnston, et al.         Expires August 2, 2003               [Page 151]

Internet-Draft            SIP Service Examples             February 2003


   [7]   Rosenberg, J., Schulzrinne, H., Camarillo, G. and J. Peterson,
         "Best Current Practices for Third Party Call Control in the
         Session  Initiation Protocol", draft-ietf-sipping-3pcc-02 (work
         in progress), June 2002.

   [8]   Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
         Session Description Protocol (SDP)", RFC 3264, June 2002.

   [9]   Sparks, R. and A. Johnston, "Session Initiation Protocol Call
         Control - Transfer", draft-ietf-sipping-cc-transfer-01 (work in
         progress), February 2003.

   [10]  Rosenberg, J. and H. Schulzrinne, "A Session Initiation
         Protocol (SIP) Event Package for Dialog State",
         draft-ietf-sipping-dialog-package-00 (work in progress), June
         2002.

   [11]  Roach, A., "Session Initiation Protocol (SIP)-Specific Event
         Notification", RFC 3265, June 2002.

   [12]  Mahy, R., "A Multi-party Application Framework for SIP",
         draft-ietf-sipping-cc-framework-01 (work in progress), July
         2002.


Authors' Addresses

   Alan Johnston
   WorldCom
   100 South 4th Street
   St. Louis, MO  63104

   EMail: alan.johnston@wcom.com


   Robert J. Sparks
   dynamicsoft
   5100 Tennyson Parkway
   Suite 1200
   Plano, TX  75024

   EMail: rsparks@dynamicsoft.com









Johnston, et al.         Expires August 2, 2003               [Page 152]

Internet-Draft            SIP Service Examples             February 2003


   Chris Cunningham
   dynamicsoft
   5100 Tennyson Parkway
   Suite 1200
   Plano, TX  75024

   EMail: ccunningham@dynamicsoft.com


   Steve Donovan
   dynamicsoft
   5100 Tennyson Parkway
   Suite 1200
   Plano, TX  75024

   EMail: sdonovan@dynamicsoft.com


   Kevin Summers
   Sonus
   1701 North Collins Blvd
   Suite 3000
   Richardson, TX  75080

   EMail: kevin.summers@sonusnet.com


























Johnston, et al.         Expires August 2, 2003               [Page 153]

Internet-Draft            SIP Service Examples             February 2003


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property 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; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication 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 implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.


Full Copyright Statement

   Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



Johnston, et al.         Expires August 2, 2003               [Page 154]

Internet-Draft            SIP Service Examples             February 2003


   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































Johnston, et al.         Expires August 2, 2003               [Page 155]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/