An improved call admission control method and apparatus is provided in which a MAC layer parameter such as the FER is used as a basis for call admission control. According to some aspects of the invention, a \u201cslim\u201d TCP stack is provided which eliminates the socket layer found in a conventional TCP stack, thereby eliminating socket buffers and the associated buffer-to-buffer copying. The power module has a direct current power source, a pulse width modulation circuit connected to the DC power source for generating a pulse width modulation signal, an electronic switch connected to the pulse width modulation circuit for receiving the modulation signal so as to convert the DC power into a high-frequency alternating power supplied to the primary side of a transformer.