Avoid unregistration of SIP users


As we know that each registered SIP user will register/unregister with SIP server for every couple of Milli seconds or seconds (qualify parameter). Is there any way to avoid unregistrations with SIP server? Even though, our internet works fine, and no disconnections, sip user phones are registering and unregistering with SIP server. When unregistration is happened, our sip users are unable to receive incoming calls at that point of time.

Any help would be appreciated.

Thanks in advance.

There is no capability in either chan_sip or res_pjsip to prevent unregistrations or binding expiration.