I have few doubts regarding SIP IM:
1.Can SIP IM initiate a SIP dialog on its own? 
2.Without any INVITE or any Call established can SIP ua send a SIP IM?
3.Like Windowds Msgr , For the First SIP IM , x-ms-invite is sent which iniates the converation, But These session should be treated as same media session would have been iniated by any other INIVTE?
4.How should SIP Server respond to the Normal INIVITE and x-ms-invite? should treat same or diffrerent?
 
Hoping for your reply.
with Regards.
Abhijit