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RFC 3666

 
 
 

Session Initiation Protocol (SIP) Public Switched Telephone Network (PSTN) Call Flows

Part 2 of 4, p. 23 to 54
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2.3.  Successful SIP to ISUP PSTN call with overflow

   Alice          Proxy 1         NGW 1          NGW 2        Switch B
    |              |              |              |              |
    |  INVITE F1   |              |              |              |
    |------------->|              |              |              |
    |              |  INVITE F2   |              |              |
    |    100  F3   |------------->|              |              |
    |<-------------|    503 F4    |              |              |
    |              |<-------------|              |              |
    |              |    ACK F5    |              |              |
    |              |------------->|              |              |
    |              |   INVITE F6                 |              |
    |              |---------------------------->|     IAM F7   |
    |              |                             |------------->|
    |              |                             |     ACM F8   |
    |              |            183 F9           |<-------------|
    |   183 F10    |<----------------------------|              |
    |<-------------|                             |              |
    |               Two Way RTP Media            | One Way Voice|
    |<==========================================>|<=============|
    |              |                             |    ANM F11   |
    |              |           200 F12           |<-------------|
    |    200 F13   |<----------------------------|              |
    |<-------------|                             |              |
    |    ACK F14   |                             |              |
    |------------->|            ACK F15          |              |
    |              |---------------------------->|              |
    |             Both Way RTP Media             |Both Way Voice|
    |<==========================================>|<============>|
    |    BYE F16   |                             |              |
    |------------->|           BYE F17           |              |
    |              |---------------------------->|              |
    |              |           200 F18           |              |
    |    200 F19   |<----------------------------|    REL F20   |
    |<-------------|                             |------------->|
    |              |                             |    RLC F21   |
    |              |                             |<-------------|
    |              |                             |              |

   Alice calls Bob through Proxy 1.  Proxy 1 tries to route to a Network
   Gateway NGW 1.  NGW 1 is not available and responds with a 503
   Service Unavailable (F4).  The call is then routed to Network Gateway
   NGW 2.  Bob answers the call.  The call is terminated when Alice
   disconnects the call.  NGW 2 and Bob's telephone switch use ANSI ISUP
   signaling.

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   NGW 2 also only accepts SIP messages that come through Proxy 1, so
   the Contact URI sip:ngw2@a.example.com is used in this flow.

   This flow shows UDP transport.

   Message Details

   F1 INVITE Alice -> Proxy 1

   INVITE sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com>
   Proxy-Authorization: Digest username="alice",
    realm="a.example.com", nonce="b59311c3ba05b401cf80b2a2c5ac51b0",
    opaque="", uri="sip:+19725552222@ss1.a.example.com;user=phone",
    response="ba6ab44923fa2614b28e3e3957789ab0"
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   /* Proxy 1 uses a Location Service function to determine where B is
   located.  Proxy 1 receives a primary route NGW 1 and a secondary
   route NGW 2.  NGW 1 is tried first */


   F2 INVITE Proxy 1 -> NGW 1

   INVITE sip:+19725552222@ngw1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl

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   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F3 100 Trying Proxy 1 -> Alice

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F4 503 Service Unavailable NGW 1 -> Proxy 1

   SIP/2.0 503 Service Unavailable
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=123456789
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0

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   F5 ACK Proxy 1 -> NGW 1

   ACK sip:ngw1@a.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com>;user=phone>
    ;tag=123456789
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0

   /* Proxy 1 now tries secondary route to NGW 2 */


   F6 INVITE Proxy 1 -> NGW 2

   INVITE sip:+19725552222@ngw2.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F7 IAM NGW 2 -> Bob

   IAM
   CdPN=972-555-2222,NPI=E.164,NOA=National
   CgPN=314-555-1111,NPI=E.164,NOA=National

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   F8 ACM Bob -> NGW 2

   ACM


   F9 183 Session Progress NGW 2 -> Proxy 1

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw2@a.example.com>
   Content-Type: application/sdp
   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw2.a.example.com
   s=-
   c=IN IP4 ngw2.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   /* RTP packets are sent by GW to A for audio (e.g. ring tone) */


   F10 183 Session Progress Proxy 1 -> Alice

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw2@a.example.com>
   Content-Type: application/sdp

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   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw2.a.example.com
   s=-
   c=IN IP4 ngw2.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F11 ANM Bob -> NGW 2

   ANM


   F12 200 OK NGW 2 -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw2@a.example.com>
   Content-Type: application/sdp
   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw2.a.example.com
   s=-
   c=IN IP4 ngw2.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F13 200 OK Proxy 1 -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101

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   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw2@a.example.com>
   Content-Type: application/sdp
   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw2.a.example.com
   s=-
   c=IN IP4 ngw2.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F14 ACK Alice -> Proxy 1

   ACK sip:ngw2@a.example.com SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   Route: <ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F15 ACK Proxy 1 -> NGW 2

   ACK sip:ngw2@a.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK

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   Content-Length: 0

   /* RTP streams are established between A and B(via the GW) */

   /* Alice Hangs Up with Bob. */


   F16 BYE Alice -> Proxy 1

   BYE sip:ngw2@a.example.com SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   Route: <ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F17 BYE Proxy 1 -> NGW 2

   BYE sip:ngw2@a.example.com SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F18 200 OK NGW 2 -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.2
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>

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    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F19 200 OK Proxy 1 -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 BYE
   Content-Length: 0


   F20 REL NGW 2 -> B

   REL
   CauseCode=16 Normal


   F21 RLC B -> NGW 2

   RLC

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2.4.  Successful SIP to SIP using ENUM Query

   Alice         DNS Server         Proxy 3            Bob
     |                |                |                |
     |  ENUM Query F1 |                |                |
     |--------------->|                |                |
     |   Response F2  |                |                |
     |<---------------|                |                |
     |            INVITE F3            |                |
     |-------------------------------->|    INVITE F4   |
     |             100 F5              |--------------->|
     |<--------------------------------|      180 F6    |
     |             180 F7              |<---------------|
     |<--------------------------------|                |
     |                                 |     200 F8     |
     |             200 F9              |<---------------|
     |<--------------------------------|                |
     |             ACK F10             |                |
     |-------------------------------->|     ACK F11    |
     |                                 |--------------->|
     |                Both Way RTP Media                |
     |<================================================>|
     |                                 |     BYE F12    |
     |             BYE F13             |<---------------|
     |<--------------------------------|                |
     |             200 F14             |                |
     |-------------------------------->|     200 F15    |
     |                                 |--------------->|
     |                                 |                |

   In this scenario, Alice places a call to Bob by dialing Bob's
   telephone number (9725552222).  Alice's UA converts the phone number
   to an E.164 number (+19725552222), and performs an ENUM query [9] on
   the E.164 number (2.2.2.2.5.5.5.2.7.9.1.e164.arpa), which returns a
   NAPTR record containing a SIP AOR URI for Bob
   (sip:+19725552222@b.example.com).  As a result, Alice's UA sends an
   INVITE and the call completes over IP bypassing the PSTN.

   The call is terminated when Bob sends a BYE message.

   Message Details

   F1 ENUM Query Alice -> DNS Server

   2.2.2.2.5.5.5.2.7.9.1.e164.arpa

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   F2 ENUM NAPTR Set DNS Server -> Alice

   $ORIGIN 2.2.2.2.5.5.5.2.7.9.1.e164.arpa.
         IN NAPTR 100 10 "u" "sip+E2U"
                "!^.*$!sip:+19725552222@b.example.com!".


   F3 INVITE Alice -> Proxy 3

   INVITE sip:+19725552222@b.example.com SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+13145551111@client.a.example.com>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 INVITE Proxy 3 -> Bob

   INVITE sip:+19725552222@client.b.example.com SIP/2.0
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+13145551111@client.a.example.com>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=UserA 2890844526 2890844526 IN IP4 client.a.example.com
   s=-

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   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F5 100 Trying Proxy 3 -> Alice

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Content-Length: 0


   F6 180 Ringing B -> Proxy 3

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
    ;received=192.0.2.233
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+19725552222@client.b.example.com>
   Content-Length: 0


   F7 180 Ringing Proxy 3 -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+19725552222@client.b.example.com>
   Content-Length: 0

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   F8 200 OK Bob -> Proxy 3

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
    ;received=192.0.2.233
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+19725552222@client.b.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 151

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


   F9 200 OK Proxy -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 INVITE
   Contact: <sip:+19725552222@client.b.example.com>
   Content-Type: application/sdp
   Content-Length: 151

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.b.example.com
   s=-
   c=IN IP4 192.0.2.100
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

Top      Up      ToC       Page 36 
   F10 ACK Alice -> Proxy 3

   ACK sip:+19725552222@client.b.example.com SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bq9
   Max-Forwards: 70
   Route: <sip:ss3.b.example.com;lr>
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 ACK
   Content-Length: 0


   F11 ACK Proxy 3 -> Bob

   ACK sip:+19725552222@client.b.example.com SIP/2.0
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bq9
    ;received=192.0.2.101
   Max-Forwards: 69
   From: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   To: <tel:+19725552222>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 2 ACK
   Content-Type: application/sdp
   Content-Length: 0

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

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


   F12 BYE Bob -> Proxy 3

   BYE sip:+13145551111@client.a.example.com SIP/2.0
   Via: SIP/2.0/UDP client.b.example.com:5060;branch=z9hG4bKfgaw2
   Max-Forwards: 70
   Route: <sip:ss3.b.example.com;lr>
   From: <tel:+19725552222>;tag=314159
   To: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F13 BYE Proxy 3 -> Alice

   BYE sip:+13145551111@client.a.example.com SIP/2.0

Top      Up      ToC       Page 37 
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
    ;received=192.0.2.100
   Via: SIP/2.0/UDP client.b.example.com:5060;branch=z9hG4bKfgaw2
   Max-Forwards: 69
   From: <tel:+19725552222>;tag=314159
   To: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F14 200 OK Alice -> Proxy 3

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss3.b.example.com:5060;branch=z9hG4bK721e418c4.1
    ;received=192.0.2.233
   Via: SIP/2.0/UDP client.b.example.com:5060;branch=z9hG4bKfgaw2
    ;received=192.0.2.100
   From: <tel:+19725552222>;tag=314159
   To: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F15 200 OK Proxy 3 -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.b.example.com:5060;branch=z9hG4bKfgaw2
    ;received=192.0.2.100
   From: <tel:+19725552222>;tag=314159
   To: <sip:+13145551111@a.example.com>;tag=9fxced76sl
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 BYE
   Content-Length: 0

Top      Up      ToC       Page 38 
2.5.  Unsuccessful SIP to PSTN call: Treatment from PSTN

   Alice            Proxy 1           NGW 1            Bob
     |                |                |                |
     |   INVITE F1    |                |                |
     |--------------->|                |                |
     |     100  F2    |                |                |
     |<---------------|   INVITE F3    |                |
     |                |--------------->|                |
     |                |     100  F4    |                |
     |                |<---------------|     IAM F5     |
     |                |                |--------------->|
     |                |                |     ACM F6     |
     |                |     183 F7     |<---------------|
     |     183 F8     |<---------------|                |
     |<---------------|                |                |
     |         Two Way RTP Media       |  One Way Voice |
     |<===============================>|<===============|
     |                 Treatment Applied                |
     |<=================================================|
     |   CANCEL F9    |                |                |
     |--------------->|                |                |
     |     200 F10    |                |                |
     |<---------------|   CANCEL F11   |                |
     |                |--------------->|                |
     |                |     200 F12    |                |
     |                |<---------------|     REL F13    |
     |                |                |--------------->|
     |                |                |     RLC F14    |
     |                |     487 F15    |<---------------|
     |                |<---------------|                |
     |                |     ACK F16    |                |
     |     487 F17    |--------------->|                |
     |<---------------|                |                |
     |     ACK F18    |                |                |
     |--------------->|                |                |
     |                |                |                |

   Alice calls Bob in the PSTN through a proxy server Proxy 1 and a
   Network Gateway NGW 1.  The call is rejected by the PSTN with an
   in-band treatment (tone or recording) played.  Alice hears the
   treatment and then hangs up, which results in a CANCEL (F9) being
   sent to terminate the call.  (A BYE is not sent since no final
   response was ever received by Alice.)

Top      Up      ToC       Page 39 
   Message Details

   F1 INVITE Alice -> Proxy 1

   INVITE sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com>
   Proxy-Authorization: Digest username="alice",
    realm="a.example.com", nonce="01cf8311c3b0b2a2c5ac51bb59a05b40",
    opaque="", uri="sip:+19725552222@ss1.a.example.com;user=phone",
    response="e178fbe430e6680a1690261af8831f40"
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 100 Trying Proxy 1 -> A

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0

   /* Proxy 1 uses a Location Service function to determine where B is
   located.  Based upon location analysis the call is forwarded to NGW
   1.  Client for A prepares to receive data on port 49172 from the
   network. */

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   F3 INVITE Proxy 1 -> NGW 1

   INVITE sip:+19725552222@ngw1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 100 Trying NGW 1 -> Proxy 1

   SIP/2.0 100 Trying
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F5 IAM NGW 1 -> Bob

   IAM
   CdPN=972-555-2222,NPI=E.164,NOA=National
   CgPN=314-555-1111,NPI=E.164,NOA=National

Top      Up      ToC       Page 41 
   F6 ACM Bob -> NGW 1

   ACM


   F7 183 Session Progress NGW 1 -> Proxy 1

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw1@a.example.com>
   Content-Type: application/sdp
   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw1.a.example.com
   s=-
   c=IN IP4 ngw1.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 183 Session Progress Proxy 1 -> Alice

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw1@a.example.com>
   Content-Type: application/sdp
   Content-Length: 146

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   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw1.a.example.com
   s=-
   c=IN IP4 ngw1.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   /* Caller hears the recorded announcement, then hangs up */


   F9 CANCEL Alice -> Proxy 1

   CANCEL sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F10 200 OK Proxy 1 -> A

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F11 CANCEL Proxy 1 -> NGW 1

   CANCEL sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 CANCEL
   Content-Length: 0

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   F12 200 OK NGW 1 -> Proxy 1

   SIP/2.0 200 OK
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 CANCEL
   Content-Length: 0


   F13 REL NGW 1 -> B

   REL
   CauseCode=18 No user responding


   F14 RLC B -> NGW 1

   RLC


   F15 487 Request Terminated NGW 1 -> Proxy 1

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F16 ACK Proxy 1 -> NGW 1

   ACK sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>

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    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F17 487 Request Terminated Proxy 1 -> A

   SIP/2.0 487 Request Terminated
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F18 ACK Alice -> Proxy 1

   ACK sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/UDP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0

Top      Up      ToC       Page 45 
2.6.  Unsuccessful SIP to PSTN: REL w/Cause from PSTN

   Alice            Proxy 1           NGW 1           Switch B
     |                |                |                |
     |   INVITE F1    |                |                |
     |--------------->|                |                |
     |     100  F2    |                |                |
     |<---------------|   INVITE F3    |                |
     |                |--------------->|                |
     |                |     100  F4    |                |
     |                |<---------------|     IAM F5     |
     |                |                |--------------->|
     |                |                |    REL(1) F6   |
     |                |                |<---------------|
     |                |                |     RLC F7     |
     |                |     404 F8     |--------------->|
     |                |<---------------|                |
     |                |     ACK F9     |                |
     |                |--------------->|                |
     |     404 F10    |                |                |
     |<---------------|                |                |
     |     ACK F11    |                |                |
     |--------------->|                |                |
     |                |                |                |

   Alice calls PSTN Bob through a Proxy Server Proxy 1 and a Network
   Gateway NGW 1.  The call is rejected by the PSTN with a ANSI ISUP
   Release message REL containing a specific Cause code.  This cause
   value (1) is mapped by the Gateway to a SIP 404 Address Incomplete
   response which is proxied back to Alice.  For more details of ISUP
   cause value to SIP response mapping, refer to [4].

   Message Details

   F1 INVITE Alice -> Proxy 1

   INVITE sip:+44-1234@ss1.a.example.com;user=phone  SIP/2.0
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com;transport=tcp>
   Proxy-Authorization: Digest username="alice",
    realm="a.example.com", nonce="j1c3b0b01cf832da2c5ac51bb59a05b40",
    opaque="", uri="sip:+44-1234@ss1.a.example.com;user=phone",

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    response="a451358d46b55512863efe1dccaa2f42"
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 100 Trying Proxy 1 -> A

   SIP/2.0 100 Trying
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0

   /* Proxy 1 uses a Location Service function to determine where B is
   located.  Based upon location analysis the call is forwarded to NGW1.
   Client for A prepares to receive data on port 49172 from the network.
   */


   F3 INVITE Proxy 1 -> NGW 1

   INVITE sip:+44-1234@ngw1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 154

Top      Up      ToC       Page 47 
   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 100 Trying NGW 1 -> Proxy 1

   SIP/2.0 100 Trying
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F5 IAM NGW 1 -> Bob

   IAM
   CdPN=44-1234,NPI=E.164,NOA=International
   CgPN=314-555-1111,NPI=E.164,NOA=National


   F6 REL Bob -> NGW 1

   REL
   CauseValue=1 Unallocated number


   F7 RLC NGW 1 -> Bob

   RLC

   /* Network Gateway maps CauseValue=1 to the SIP message 404 Not
      Found */

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   F8 404 Not Found NGW 1 -> Proxy 1

   SIP/2.0 404 Not Found
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Error-Info: <sip:not-found-ann@ann.a.example.com>
   Content-Length: 0


   F9 ACK Proxy 1 -> NGW 1

   ACK sip:+44-1234@ngw1.a.example.com;user=phone SIP/2.0
   Max-Forwards: 70
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F10 404 Not Found Proxy 1 -> Alice

   SIP/2.0 404 Not Found
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Error-Info: <sip:not-found-ann@ann.a.example.com>
   Content-Length: 0


   F11 ACK Alice -> Proxy 1

   ACK sip:+44-1234@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70

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   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+44-1234@ss1.a.example.com;user=phone>;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0

2.7.  Unsuccessful SIP to PSTN: ANM Timeout

   Alice           Proxy 1           NGW 1           Switch B
     |                |                |                |
     |   INVITE F1    |                |                |
     |--------------->|                |                |
     |     100  F2    |                |                |
     |<---------------|   INVITE F3    |                |
     |                |--------------->|                |
     |                |     100  F4    |                |
     |                |<---------------|     IAM F5     |
     |                |                |--------------->|
     |                |                |     ACM F6     |
     |                |      183 F7    |<---------------|
     |     183 F8     |<---------------|                |
     |<---------------|                |                |
     |                |      Timer on NGW 1 Expires     |
     |                |                |                |
     |                |                |     REL F9     |
     |                |                |--------------->|
     |                |                |    RLC F10     |
     |                |     480 F11    |<---------------|
     |                |<---------------|                |
     |                |     ACK F12    |                |
     |                |--------------->|                |
     |     480 F13    |                |                |
     |<---------------|                |                |
     |     ACK F14    |                |                |
     |--------------->|                |                |

   Alice calls Bob in the PSTN through a proxy server Proxy 1 and
   Network Gateway NGW 1.  The call is released by the Gateway after a
   timer expires due to no ANswer Message (ANM) being received.  The
   Gateway sends an ISUP Release REL message to the PSTN and a 480
   Temporarily Unavailable response to Alice in the SIP network.

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   Message Details

   F1 INVITE Alice -> Proxy 1

   INVITE sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com;transport=tcp>
   Proxy-Authorization: Digest username="alice",
    realm="a.example.com", nonce="da2c5ac51bb59a05j1c3b0b01cf832b40",
    opaque="", uri="sip:+19725552222@ss1.a.example.com;user=phone",
    response="579cb9db184cdc25bf816f37cbc03c7d"
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   /* Proxy 1 uses a Location Service function to determine where B is
   located.  Based upon location analysis the call is forwarded to NGW
   1.  Client for A prepares to receive data on port 49172 from the
   network.*/


   F2 100 Trying Proxy 1 -> A

   SIP/2.0  100 Trying
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0

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   F3 INVITE Proxy 1 -> NGW 1

   INVITE sip:+19725552222@ngw1.a.example.com;user=phone SIP/2.0
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Max-Forwards: 69
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.a.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 154

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.a.example.com
   s=-
   c=IN IP4 client.a.example.com
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F4 100 Trying NGW 1 -> Proxy 1

   SIP/2.0  100 Trying
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Content-Length: 0


   F5 IAM NGW 1 -> Bob

   IAM
   CdPN=972-555-2222,NPI=E.164,NOA=National
   CgPN=314-555-1111,NPI=E.164,NOA=National

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   F6 ACM Bob -> NGW 1

   ACM


   F7 183 Session Progress NGW 1 -> Proxy 1

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw1@a.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 146

   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw1.a.example.com
   s=-
   c=IN IP4 ngw1.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F8 183 Session Progress Proxy 1 -> Alice

   SIP/2.0 183 Session Progress
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   Record-Route: <sip:ss1.a.example.com;lr>
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Contact: <sip:ngw1@a.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 146

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   v=0
   o=GW 2890844527 2890844527 IN IP4 ngw1.a.example.com
   s=-
   c=IN IP4 ngw1.a.example.com
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000

   /* After NGW 1's timer expires, Network Gateway sends REL to ISUP
   network and 480 to SIP network */


   F9 REL NGW 1 -> Bob

   REL

   CauseCode=18 No user responding


   F10 RLC Bob -> NGW 1

   RLC


   F11 480 Temporarily Unavailable NGW 1 -> Proxy 1

   SIP/2.0 480 Temporarily Unavailable
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
    ;received=192.0.2.111
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Error-Info: <sip:temp-unavail-ann@ann.a.example.com>
   Content-Length: 0


   F12 ACK Proxy 1 -> NGW 1

   ACK sip:ngw1@a.example.com SIP/2.0
   Via: SIP/2.0/TCP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1
   Max-Forwards: 70
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl

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   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0


   F13 480 Temporarily Unavailable F13 Proxy 1 -> Alice

   SIP/2.0 480 Temporarily Unavailable
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 INVITE
   Error-Info: <sip:temp-unavail-ann@ann.a.example.com>
   Content-Length: 0


   F14 ACK Alice -> Proxy 1

   ACK sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
   Max-Forwards: 70
   Via: SIP/2.0/TCP client.a.example.com:5060;branch=z9hG4bK74bf9
   From: Alice <sip:+13145551111@ss1.a.example.com;user=phone>
    ;tag=9fxced76sl
   To: Bob <sip:+19725552222@ss1.a.example.com;user=phone>
    ;tag=314159
   Call-ID: 2xTb9vxSit55XU7p8@a.example.com
   CSeq: 1 ACK
   Content-Length: 0



(page 54 continued on part 3)

Next RFC Part