A communication interface controller for multiplexing data packet streams from a plurality of data packets to generate an output stream for transmission from an endpoint. The data packet streams may be multiplexed according to a QoS associated with each data packet stream and at a rate equal to or greater than a medium transmission rate. For the case of a 1 Gbps transfer rate or 125 MBps, the data packet streams may be multiplexed at a rate equal to or greater than 1 MHz, thereby providing gapless scheduling and transmission of the data packet streams.