Wireshark logs

1. SIP Registration Process

The User Agent (192.168.105.110) periodically registers itself with the SIP server (192.168.105.105) to be reachable.

• Packet 1: REGISTER request from 192.168.105.110 to 192.168.105.105
• Packet 2: SIP Server responds with 100 Trying (Processing the request)
• Packet 3: SIP Server confirms registration with 200 OK

🔄 Re-Registration:

• SIP clients typically refresh their registration periodically (e.g., every 10, 40, 70, or 100 seconds, as seen in packets 4, 11, 24, and 1358).

 2. First Call Attempt (Invite & Decline - Call Rejected)

At timestamp 36.002756, the client (192.168.105.110) attempts to call SIP user 2504 at the server (192.168.105.105).

• Packet 7: INVITE sent to sip:2504@192.168.105.105
• Packet 8: 100 Trying (SIP Server acknowledges the request)
• Packet 9: 603 Decline (Call is rejected)
• Packet 10: ACK (Acknowledgment of rejection)

💡 Possible reasons for decline:

• User 2504 is unavailable.
• The server rejects the call due to policy, configuration, or network issues.

 3. Second Call Attempt (Successful Call Setup)

At timestamp 52.003970, another call is made to sip:2504@192.168.105.105, but this time the call is routed differently:

• Packet 14-15: INVITE and 100 Trying
• Packet 16: Server 192.168.105.105 sends an INVITE to sip:2504@192.168.105.110:5060 (redirecting the call).
• Packet 17: 100 Trying from 192.168.105.110
• Packets 18-19: 180 Ringing (Indicates the call is ringing)
• Packets 20-21: 200 OK (INVITE) (Call is accepted)
• Packets 22-23: ACK (Acknowledging the call setup)

🎯 Conclusion: The second call attempt was successful after redirection.