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RFC 5359

 
 
 

Session Initiation Protocol Service Examples

Part 5 of 6, p. 113 to 146
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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         |      |
             |                |--------------------------->|      |
             |                |              INVITE F16           |
             |                |---------------------------------->|
             |                |            180 Ringing F17        |
             |     180 F18    |<----------------------------------|
             |<---------------|               200 OK F19          |
             |   200 OK F20   |<----------------------------------|
             |<---------------|                                   |
             |     ACK F21    |                                   |
             |--------------->|                 ACK F22           |
             |                |---------------------------------->|
             |               Both way RTP Established             |
             |<==================================================>|

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

   Alice's call to Bob will result in an attempt to locate Bob 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.

   Message Details

      F1 INVITE Alice -> Proxy

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

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


      F2 INVITE Proxy -> B1

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

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

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


      F3 (100 Trying) Proxy -> Alice

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


      F4 180 Ringing B1 -> Proxy

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

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      F5 180 Ringing Proxy -> Alice

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

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


      F6 CANCEL Proxy -> B1

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


      F7 200 OK B1 -> Proxy

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


      F8 487 Request Terminated B1 -> Proxy

      SIP/2.0 487 Request Terminated

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


      F9 ACK Proxy -> B1

      ACK sips:bob@client.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.1
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=765432
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F10 INVITE Proxy -> B2

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

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

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


      F11 480 Not Logged In B2 -> Proxy

      SIP/2.0 480 Not Logged In
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.2
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=314756
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F12 ACK Proxy -> B2

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


      F13 INVITE Proxy -> B3

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

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

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


      F14 486 Busy Here B3 -> Proxy

      SIP/2.0 486 Busy Here
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.3
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Content-Length: 0


      F15 ACK Proxy -> B3

      ACK sips:bob@client3.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.3
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7654321
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F16 INVITE Proxy -> B4

      INVITE sips:bob@client4.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.4
      Via: SIP/2.0/TLS client.atlanta.example.com:5061

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

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


      F17 180 Ringing B4 -> Proxy

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


      F18 180 Ringing Proxy -> Alice

      SIP/2.0 180 Ringing
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136

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      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Length: 0


      F19 200 OK B4 -> Proxy

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83749.4
       ;received=192.0.2.54
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      Record-Route: <sips:ss1.example.com;lr>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:bob@client4.biloxi.example.com>
      Content-Type: application/sdp
      Content-Length: ...

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


      F20 200 OK Proxy -> Alice

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

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


      F21 ACK Alice -> Proxy

      ACK sips:bob@client4.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf
      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=7137136
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 ACK
      Content-Length: 0


      F22 ACK Proxy -> B4

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

      /* RTP streams are established between Alice and B4. */

      /* User B4 hangs up with Alice. */


      F23 BYE B4 -> Proxy

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7

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      Route: <sips:ss1.example.com;lr>
      Max-Forwards: 70
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F24 BYE Proxy -> Alice

      BYE sips:alice@client.atlanta.example.com SIP/2.0
      Via: SIP/2.0/TLS ss1.example.com:5061
       ;branch=z9hG4bK83754
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      Max-Forwards: 69
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136
      To: Alice <sips:alice@atlanta.example.com>;tag=1234567
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 BYE
      Content-Length: 0


      F25 200 OK Alice -> Proxy

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


      F26 200 OK Proxy -> B4

      SIP/2.0 200 OK
      Via: SIP/2.0/TLS client4.biloxi.example.com:5061
       ;branch=z9hG4bKnashds7
       ;received=192.0.2.105
      From: Bob <sips:bob@biloxi.example.com>;tag=7137136

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

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2.13.  Call Management (Incoming Call Screening)

                                                      Announcement
           Alice           Proxy            Bob           Server

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

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

   Note that call screening cannot be done using the From header --
   instead some form of authentication credentials must be used.

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

   Message Details

      F1 INVITE Alice -> Bob

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

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


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

      F2 305 Use Proxy Bob -> Alice

      SIP/2.0 305 Use Proxy
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf9
       ;received=192.0.2.103
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=342123
      Call-ID: 12345600@atlanta.example.com
      CSeq: 1 INVITE
      Contact: <sips:ss1.example.com>
      Content-Length: 0

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      F3 ACK Alice -> Bob

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

      /* A retries the call through the proxy. */


      F4 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf0
      Max-Forwards: 70
      Route: <sips:ss1.example.com>
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 INVITE
      Contact: <sips:alice@client.atlanta.example.com>
      Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY
      Content-Type: application/sdp
      Content-Length: ...

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

      /* Proxy 1 challenges Alice for authentication. */


      F5 407 Proxy Authentication Required Proxy 1 -> Alice

      SIP/2.0 407 Proxy Authentication Required
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bf0
       ;received=192.0.2.103

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


      F6 ACK Alice -> Proxy 1

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

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


      F7 INVITE Alice -> Proxy 1

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

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


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

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


      F9 ACK Alice -> Proxy 1

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

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


      F10 INVITE Alice -> Proxy 1

      INVITE sips:screen-fail-term-ann@ms.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74bfj
      Max-Forwards: 70

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

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


   F11 200 OK Announcement Server -> Proxy 1

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

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


   F12 ACK Alice -> Announcement Server

      ACK sips:ms.biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b32

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      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=234934
      Call-ID: 12345600@atlanta.example.com
      CSeq: 4 ACK
      Content-Length: 0

      /* Announcement Server plays announcement then disconnects. */


      F13 BYE Announcement Server -> Alice

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


      F14 200 OK Alice -> Announcement Server

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

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2.14.  Call Management (Outgoing Call Screening)


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

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

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

   Message Details

      F1 INVITE Alice -> Proxy 1

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

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

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

      /* Proxy 1 challenges Alice for authentication. */


      F2 407 Proxy Authentication Required Proxy 1 -> Alice

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


      F3 ACK Alice -> Proxy 1

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

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


      F4 INVITE Alice -> Proxy 1

      INVITE sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>
      Call-ID: 12345600@atlanta.example.com

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

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


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

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


      F6 ACK Alice -> Proxy 1

      ACK sips:bob@biloxi.example.com SIP/2.0
      Via: SIP/2.0/TLS client.atlanta.example.com:5061
       ;branch=z9hG4bK74b4
      Max-Forwards: 70
      From: Alice <sips:alice@atlanta.example.com>;tag=1234567
      To: Bob <sips:bob@biloxi.example.com>;tag=18017
      Call-ID: 12345600@atlanta.example.com
      CSeq: 2 ACK
      Proxy-Authorization: Digest username="alice", realm="example.com",
       nonce="cb360afc54bbaec39f943bd820d9a45c", opaque="",
       uri="sips:bob@biloxi.example.com",
       response="b9d2e5bcdec9f69ab2a9b44f270285a6"
      Content-Length: 0

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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   |
             |              |              |              |
             |              |              | SUBSCRIBE F16|
             |              |              |<-------------|
             |              |              |  200 OK F17  |
             |              |              |------------->|
             |              |              |  NOTIFY F18  |
             |              |              |------------->|
             |              |              |  200 OK F19  |
             |              |              |<-------------|
             |           INVITE Replaces: Park Server F20 |
             |<-------------------------------------------|

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             |              |              |   200 F21    |
             |------------------------------------------->|
             |              |              |    ACK F22   |
             |<-------------------------------------------|
             |                  RTP Media                 |
             |<==========================================>|
             |           BYE F23           |              |
             |---------------------------->|              |
             |          200 OK F24         |              |
             |<----------------------------|              |
             |       No more RTP Music     |              |

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

   Carol wishes to retrieve the call, so she sends an INVITE containing
   the dialog identifiers to Alice, which replaces the session with the
   Park Server.  Alice accepts the call and sends a BYE to the Park
   Server.  Carol obtains the dialog identifiers from a NOTIFY from the
   Park Server.

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

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

   Message Details

   F1 INVITE Alice -> Bob

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

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   Content-Length: ...

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


   F2 180 Ringing Bob -> Alice

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


   F3 200 OK Bob -> Alice

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

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

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   F4 ACK Alice -> Bob

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

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


   F5 REFER Bob -> Park Server

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


   F6 202 Accepted Park Server -> Bob

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

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


   F7 NOTIFY Park Server -> Bob

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

   SIP/2.0 100 Trying


   F8 200 OK Bob -> Park Server

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

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


   F9 INVITE Park Server -> Alice

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

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   To: <sips:a8342043f@atlanta.example.com;gr>
   Call-ID: a5-75-34-12-76@server.example.com
   CSeq: 1 INVITE
   Referred-By: <sips:bob@biloxi.example.com>
   Contact: <sips:park@server.example.com>;automaton
       ;+sip.byeless;+sip.rendering="no"
   Require: replaces
   Replaces: 12345601@atlanta.example.com
    ;from-tag=314159;to-tag=1234567
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

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


   F10 200 OK Alice -> Park Server

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

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

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   F11 ACK Park Server -> Alice

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


   F12 BYE Alice -> Bob

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


   F13 200 OK Bob -> Alice

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

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


   F14 NOTIFY Park Server -> Bob

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

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   To: Bob <sips:bob@biloxi.example.com>;tag=02134
   Max-Forwards: 70
   From: Park Server <sips:park@server.example.com>;tag=56323
   Call-ID: 4802029847@biloxi.example.com
   CSeq: 2 NOTIFY
   Event: refer
   Subscription-State: terminated;reason=noresource
   Contact: <sips:park@server.example.com>;automaton
       ;+sip.byeless;+sip.rendering="no"
   Content-Type: message/sipfrag
   Content-Length: ...

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


   F15 200 OK Bob -> Park Server

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

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

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


   F16 SUBSCRIBE  Carol -> Park Server

   SUBSCRIBE sips:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TLS client.chicago.example.com:5061
    ;branch=z9hG4bK74b232

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   Max-Forwards: 70
   From: Carol <sips:carol@chicago.example.com>;tag=158x93461
   To: <sips:park@server.example.com>
   Call-ID: 2d6485356dfaj34dsf
   CSeq: 1 SUBSCRIBE
   Contact: <sips:carol@client.chicago.example.com>
   Event: dialog
   Expires: 0
   Accept: application/dialog-info+xml
   Content-Length: 0


   F17 200 OK Park Server -> Carol

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS client.chicago.example.com:5061
    ;branch=z9hG4bK74b232
    ;received=192.0.2.105
   From: Carol <sips:carol@chicago.example.com>;tag=158x93461
   To: <sips:park@server.example.com>;tag=3213j
   Call-ID: 2d6485356dfaj34dsf
   CSeq: 1 SUBSCRIBE
   Contact: <sips:park@server.example.com>;automaton
       ;+sip.byeless;+sip.rendering="no"
   Content-Length: 0


   F18 NOTIFY  Park Server -> Carol

   NOTIFY sips:carol@client.example.com SIP/2.0
   Via: SIP/2.0/TLS server.example.com:5061
    ;branch=z9hG4bK74b8skd
   Max-Forwards: 70
   To: Carol <sips:carol@chicago.example.com>;tag=158x93461
   From: <sips:park@server.example.com>;tag=3213j
   Call-ID: 2d6485356dfaj34dsf
   CSeq: 1 NOTIFY
   Contact: <sips:park@server.example.com>;automaton
       ;+sip.byeless;+sip.rendering="no"
   Event: dialog
   Subscription-State: terminated;reason=timeout
   Content-Type: application/dialog-info+xml
   Content-Length: ...
   <?xml version="1.0"?>
   <dialog-info xmlns="urn:ietf:params:xml:ns:dialog-info"
         version="0" state="full" entity="sips:park@server.example.com">
      <dialog id="439920143524"
         call-id="a5-75-34-12-76@server.example.com"

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         local-tag="0111" remote-tag="098594" direction="initiator">
        <duration>1</duration>
        <local>
           <target>sips:park@server.example.com</target>
        </local>
        <remote>
          <target>sips:a8342043f@atlanta.example.com;gr</target>
        </remote>
        <state>confirmed</state>
      </dialog>
    </dialog-info>


   F19 200 OK Carol -> Park Server

   SIP/2.0 200 OK
   Via: SIP/2.0/TLS server.example.com:5061
    ;branch=z9hG4bK74b8skd
    ;received=192.0.2.103
   To: Carol <sips:carol@chicago.example.com>;tag=158x93461
   From: <sips:park@server.example.com>;tag=3213j
   Call-ID: 2d6485356dfaj34dsf
   CSeq: 1 NOTIFY
   Contact: <sips:carol@client.chicago.example.com>
   Content-Length: 0


   F20 INVITE Carol -> Alice

   INVITE sips:alice@atlanta.example.com SIP/2.0
   Via: SIP/2.0/TLS client.chicago.example.com:5061
    ;branch=z9hG4bK74bQ2
   Max-Forwards: 70
   From: Carol <sips:carol@chicago.example.com>;tag=5893461
   To: Alice <sips:alice@atlanta.example.com>
   Call-ID: 6485356@chicago.example.com
   CSeq: 1 INVITE
   Contact: <sips:carol@client.chicago.example.com>
   Require: replaces
   Replaces: a5-75-34-12-76@server.example.com
    ;to-tag=098594;from-tag=0111
   Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER,
    SUBSCRIBE, NOTIFY
   Supported: replaces
   Content-Type: application/sdp
   Content-Length: ...

   v=0

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


   F21 200 OK Alice -> Carol

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

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


   F22 ACK Carol -> Alice

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

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

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   F23 BYE Alice -> Park Server

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


   F24 200 OK Park Server -> Alice

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


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