Hi,
We're using test devices with iOS 13+ to test our VoLTE network as these devices (13+) has default VoLTE profile which works without device certification.
After successful initial SIP registration, iPhone is sending SIP Re-Register with integrity-protection=no, then network (cscf) is terminating existing registration and returning 401 to challenge Re-Register and dropping active call as it deletes active registration.
we wonder; 1-) why iPhone is sending SIP Re-Register frequently. Although Reg-expire timer in successful initial Registration is 7200 seconds, Phone is sending periodical SIP Re-registers at almost 1 min intervals.
2-) Network forces iPhone to enable integrity-protection in initial SIP Registration and iPhone accepts this. Although, integrity-protection is used in initial SIP Registration, why does iPhone send SIP Re-Register with integrity-protection=no?
Thanks Regards
