A method of delivering QoS on TCP data networks: This is a de-facto method, built into the operation of most TCP/IP routers. It begins with a set of queues with different priority ratings. Queues are then serviced in strict order of queue priority, so the high priority queue is always serviced first, then the next-lower priority, and so on. This method is good for simple needs such as moving important traffic but fails badly in high-traffic applications.