Abstract: A zero-setting QoS system, which is designed with priority session and bandwidth technologies in an undifferentiated network, such that the packets for universal or dedicated network can obtain priority transmission services. As a QoS system of priority levels, the network packets are received from the inlet, and 802.1q tag and 802.1p tag are loaded onto the packets, so that the packets can be transmitted by priority levels, then 802.1q tag and 802.1p tag are removed from the outlet of the system, enabling easy operation in an undifferentiated network environment; therefore, the system with rapid transmission capability can allocate and transmit the network packets within a shorter response time and by better priority levels.