When Zoiper gets received parameter on Contact Header , it sends re-registration with received IP parameter on Contact Header. So UA Server cannot understand that UAC is natted so dont sends Options packets! so after a while , Modem or Firewall closes Ports. and then UAC is Zoiper that Unreachable. There isnt anything about IETF!
Version 3.9
Windows 10
First Flow.
-----------
UAC sends Registration --->>
Contact : <sip:123456789@192.168.0.223:5060>
Kamailio answer for register <<---200 OK
Contact : <sip:123456789@192.168.0.223:5060>;received=195.8.8.10
Second Flow
------------
UAC sends re-registartion --->> (Oh God there is a received I must send registarion again!!)
Contact : <sip:123456789@195.8.8.10:5060>
Kamailio answer for register <<---200 OK (OK Bro! you aren't Natted. No problem. I dont send Options)
Contact : <sip:123456789@195.8.8.10:5060>
