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Esempi

Un esempio di chiamata da rete PSTN a SIP

Sfruttando quando definito nella RFC 3666, possiamo vedere un esempio di chiamata tra Alice e Bob:

   Switch A       	   NGW 1         	  Proxy 1         		   Bob

     |     IAM F1     |                |                |
     |--------------->|   INVITE F2    |                |
     |                |--------------->|   INVITE F3    |
     |                |     100  F4    |--------------->|
     |                |<---------------|                |
     |                |                |      180 F5    |
     |                |    180 F6      |<---------------|
     |     ACM F7     |<---------------|                |
     |<---------------|                |                |
     |  One Way Voice |                |                |
     |<===============|                |                |
     |  Ringing Tone  |                |      200 F8    |
     |<===============|    200 F9      |<---------------|
     |                |<---------------|                |
     |                |     ACK F10    |                |
     |     ANM F12    |--------------->|     ACK F11    |
     |<---------------|                |--------------->|
     | Both Way Voice |        Both Way RTP Media       |
     |<==============>|<===============================>|
     |     REL F13    |                |                |
     |--------------->|                |                |
     |     RLC F14    |                |                |
     |<---------------|     BYE F15    |                |
     |                |--------------->|     BYE F16    |
     |                |                |--------------->|
     |                |                |     200 F17    |
     |                |     200 F18    |<---------------|
     |                |<---------------|                |

I passaggi salienti della comunicazione sono:

   F1 IAM Alice -> NGW 1
   IAM
   CgPN=314-555-1111,NPI=E.164,NOA=National
   CdPN=972-555-2222,NPI=E.164,NOA=National

F2 INVITE Alice -> Proxy 1

  INVITE sip:+19725552222@ss1.a.example.com;user=phone SIP/2.0
  Via: SIP/2.0/UDP ngw1.a.example.com:5060;branch=z9hG4bKlueha2
  Max-Forwards: 70
  From: <sip:+13145551111@ngw1.a.example.com;user=phone>;tag=7643kals
  To: <sip:+19725552222@ss1.a.example.com;user=phone>
  Call-ID: 4Fde34wkd11wsGFDs3@ngw1.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

F3 INVITE Proxy 1 -> Bob

  INVITE sip:bob@client.b.example.com SIP/2.0    
  Via: SIP/2.0/UDP ss1.a.example.com:5060;branch=z9hG4bK2d4790.1    
  Via: SIP/2.0/UDP ngw1.a.example.com:5060;branch=z9hG4bKlueha2     
  ;received=192.0.2.103 Max-Forwards: 69    
  Record-Route: <sip:ss1.a.example.com;lr>    
  From: <sip: 13145551111@ngw1.a.example.com;user=phone>;tag=7643kals    
  To: <sip: 19725552222@ss1.a.example.com;user=phone>    
  Call-ID: 4Fde34wkd11wsGFDs3@ngw1.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 200 OK Bob -> 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
  Via: SIP/2.0/UDP ngw1.a.example.com:5060;branch=z9hG4bKlueha2
   ;received=192.0.2.103
  Record-Route: <sip:ss1.a.example.com;lr>
  From: <sip:+13145551111@ngw1.a.example.com;user=phone>;tag=7643kals
  To: <sip:+19725552222@ss1.a.example.com;user=phone>;tag=314159
  Call-ID: 4Fde34wkd11wsGFDs3@ngw1.a.example.com
  Contact: <sip:bob@client.b.example.com>
  CSeq: 1 INVITE
  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

Possiamo osservare che la comunicazione avviene tramite protocollo SIP ed ogni interlocutore ha assegnato un proprio numero E.164 dal provider a.example.com.

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