Example of SIP Call session between 2 phones


A sip call session between 2 phones is established as follows:

  • The calling phone sends out an invite
  • The called phone sends an information response 100 – Trying – back.
  • When the called phone starts ringing a response 180 – Ringing – is sent back
  • When the caller picks up the phone, the called phone sends a response 200 – OK
  • The calling phone responds with ACK – acknowledgement
  • Now the actual conversation is transmitted as data via RTP
  • When the person calling hangs up, a BYE request is sent to the calling phone
  • The calling phone responds with a 200 – OK.

It’s as simple as that! The SIP protocol is easy to understand and logical.

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