Systems and methods are disclosed for differentiated handling of VoIP call control messages according to their importance and functionality, thus providing to VoIP infrastructures a level of robust call control similar to that in PSTN networks. SIP messages are classified by their type or content, and resources of a VoIP call control server are allocated to the SIP messages according to a policy. The scheme also provides overload protection and prioritized handling of certain kinds of requests in VoIP call control servers.