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RFC 3666

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

Pages: 118
Best Current Practice: 76
Errata
Part 2 of 4 – Pages 23 to 54
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Top   ToC   RFC3666 - Page 23   prevText

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.
Top   ToC   RFC3666 - Page 24
   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
Top   ToC   RFC3666 - Page 25
   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
Top   ToC   RFC3666 - Page 26
   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
Top   ToC   RFC3666 - Page 27
   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
Top   ToC   RFC3666 - Page 28
   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
Top   ToC   RFC3666 - Page 29
   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
Top   ToC   RFC3666 - Page 30
   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>
Top   ToC   RFC3666 - Page 31
    ;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
Top   ToC   RFC3666 - Page 32

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
Top   ToC   RFC3666 - Page 33
   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=-
Top   ToC   RFC3666 - Page 34
   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
Top   ToC   RFC3666 - Page 35
   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   ToC   RFC3666 - 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   ToC   RFC3666 - 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   ToC   RFC3666 - 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   ToC   RFC3666 - 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. */
Top   ToC   RFC3666 - Page 40
   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   ToC   RFC3666 - 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
Top   ToC   RFC3666 - Page 42
   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
Top   ToC   RFC3666 - Page 43
   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>
Top   ToC   RFC3666 - Page 44
    ;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   ToC   RFC3666 - 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",
Top   ToC   RFC3666 - Page 46
    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   ToC   RFC3666 - 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 */
Top   ToC   RFC3666 - Page 48
   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
Top   ToC   RFC3666 - Page 49
   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.
Top   ToC   RFC3666 - Page 50
   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
Top   ToC   RFC3666 - Page 51
   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
Top   ToC   RFC3666 - Page 52
   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
Top   ToC   RFC3666 - Page 53
   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
Top   ToC   RFC3666 - Page 54
   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)

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