An application executing on a device communicates packet data with a server via an operating system (OS) on the device. The device receives information concerning a port mapping policy that specifies a plurality of applications. For each application, a predetermined assignable port space is defined within which an application specific port can be assigned. When the application is started, an OS specific port is assigned to the application. Additionally, an application specific port for the OS specific port is assigned in accordance with the port mapping policy. The device then translates data packets to be transmitted by the application, such that for a given OS specific source port, the device replaces the OS specific source port field of the packets to be transmitted with the assigned application specific port. The device then transmits the translated data packets with the assigned application specific source port.