As per my understanding, it comes because of A-party cancellation of call ... 487 is the true cause code in SIP where as 100 (when we observe as cause code) means while trying message it got cancelled by A-Party...where as if we get 180 (ringing message) then it means A-Party (calling party) cancelled the call during ringing.
Regards,
Mike
Noc1
Please help me out!!
what are the possible solutions of SIP Errors 100 and 180 and why these errors occur?