double Facepalm Ok let's get cocky, I was speaking in a way that the user understand how it works. Not actually saying you will receive an ACK and yes SIP is based on that model but I can see you need exactly the name of each transaction.
No I'm not, again you are so pretentious let me go back with my mentors and the opensips course to tell them that we are wrong because you need the exact name of each transaction and more important we do not understand sip protocol because we think that is based in handshakes-responses-acks. Outrageous 
Did you read the thread? Did you saw the settings or you are only here to pretend?
Why in the IRC, the others don't deserve to see your skills, magic, expertise and have an answer for future use here?
And one more thing Mr SIP expert tell me what do you expect with the sip debug to see if you already know how exactly it works the OPTIONS sip message? I need to write it down so in my next course I can point to that as well...