The present invention relates to methods, systems and apparatus for providing efficient packet flow fillrate adjustments and providing protection against distributed denial of service attacks. One exemplary embodiment in accordance with the invention is a method of operating a communication system including the steps of receiving, at a session border controller, a first SIP invite request message; making a decision, at the session border controller, as to whether the first SIP invite request originated from an Integrated Access Device or an IP-PBX device; generating, at the SBC, a packet flow fillrate based on said decision as to whether the SIP invite request originated at an Integrated Access Device or an Internet Protocol-Private Branch Exchange (IP-PBX) device.