SIP Messages: Call Flow

SIP Messages: Call Flow

Step 1:User 1 Sends a Invite Message to UserB to Initiate Phone call


Step 2: UserB Recieves a request (his phone rings)

SIP/2.0 100 trying — your call is important to us


Step 3: When userB’s Phone is ringing, updates are being sent (Trying, Session Progress)

SIP/2.0 183 Session Progress


Step 4: UserB Picks up the phone and sends a OK response to the caller

SIP/2.0 200 OK


Step 5: UserA responds with a ACK acknowledgement


Step 6: The conversation is established directly between the two parties

RTP (Real Time Protocol) Packets are exchanged in both directions carrying the conversation

Step 7: UserB hangs up and sends a BYE message

Step 8: UserA accepts the BYE message and responds with a OK as an Acknowledgement

SIP/2.0 200 OK



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