SIP Session Establishment

 SIP Session Establishment


   This section details session establishment between two SIP User
   Agents (UAs): Alice and Bob.  Alice (sip:alice@atlanta.example.com)
   and Bob (sip:bob@biloxi.example.com) are assumed to be SIP phones or
   SIP-enabled devices.  The successful calls show the initial
   signaling, the exchange of media information in the form of SDP
   payloads, the establishment of the media session, then finally the
   termination of the call.

   HTTP Digest authentication is used by Proxy Servers to authenticate
   the caller Alice.  It is assumed that Bob has registered with Proxy
   Server Proxy 2 as per Section 2 to be able to receive the calls via
   the Proxy.


3.1.  Successful Session Establishment


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

     |                        |
     |       200 OK F3        |
     |<-----------------------|
     |         ACK F4         |
     |----------------------->|
     |   Both Way RTP Media   |
     |<======================>|
     |                        |
     |         BYE F5         |
     |<-----------------------|
     |       200 OK F6        |
     |----------------------->|

     |                        | 

 In this scenario, Alice completes a call to Bob directly.

   Message Details

   F1 INVITE Alice -> Bob

   INVITE sip:bob@biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>



Johnston, et al.         Best Current Practice                 [Page 12]

 
RFC 3665              SIP Basic Call Flow Examples         December 2003


   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:alice@client.atlanta.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 151

   v=0
   o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com
   s=-
   c=IN IP4 192.0.2.101
   t=0 0
   m=audio 49172 RTP/AVP 0
   a=rtpmap:0 PCMU/8000


   F2 180 Ringing Bob -> Alice

   SIP/2.0 180 Ringing
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>;tag=8321234356
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com;transport=tcp>
   Content-Length: 0


   F3 200 OK Bob -> Alice

   SIP/2.0 200 OK
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bf9
    ;received=192.0.2.101
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>;tag=8321234356
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 INVITE
   Contact: <sip:bob@client.biloxi.example.com;transport=tcp>
   Content-Type: application/sdp
   Content-Length: 147

   v=0
   o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
   s=-
   c=IN IP4 192.0.2.201
   t=0 0
   m=audio 3456 RTP/AVP 0
   a=rtpmap:0 PCMU/8000



Johnston, et al.         Best Current Practice                 [Page 13]

 
RFC 3665              SIP Basic Call Flow Examples         December 2003




   F4 ACK Alice -> Bob

   ACK sip:bob@client.biloxi.example.com SIP/2.0
   Via: SIP/2.0/TCP client.atlanta.example.com:5060;branch=z9hG4bK74bd5
   Max-Forwards: 70
   From: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   To: Bob <sip:bob@biloxi.example.com>;tag=8321234356
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 ACK
   Content-Length: 0

   /* RTP streams are established between Alice and Bob */

   /* Bob Hangs Up with Alice. Note that the CSeq is NOT 2, since
      Alice and Bob maintain their own independent CSeq counts.
      (The INVITE was request 1 generated by Alice, and the BYE is
      request 1 generated by Bob) */


   F5 BYE Bob -> Alice

   BYE sip:alice@client.atlanta.example.com SIP/2.0
   Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
   Max-Forwards: 70
   From: Bob <sip:bob@biloxi.example.com>;tag=8321234356
   To: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 BYE
   Content-Length: 0


   F6 200 OK Alice -> Bob

   SIP/2.0 200 OK
   Via: SIP/2.0/TCP client.biloxi.example.com:5060;branch=z9hG4bKnashds7
    ;received=192.0.2.201
   From: Bob <sip:bob@biloxi.example.com>;tag=8321234356
   To: Alice <sip:alice@atlanta.example.com>;tag=9fxced76sl
   Call-ID: 3848276298220188511@atlanta.example.com
   CSeq: 1 BYE

https://tools.ietf.org/html/rfc3665 

https://www.ietf.org/rfc/rfc3261.txt