METHOD AND SYSTEM FOR MANAGING CONGESTION

PROBLEM TO BE SOLVED: To improve a service quality at the time of congestion by structuring a queue by relative priority so that a queue list may be traced in the lowering order of priority from the highest priority queue to the lowest priority queue. SOLUTION: A frame 16 is received by a receiver unit 18 of a network exchange 10 to judge a connection handle 20 according to a connection identifier 17 for identifying the length of the frame and the connection to obtain a connection descriptor 24. A rate managing logic part 48 sets a DE bit when the frame is in an guaranty band, and a frame queue inputting logic part 26 selects a queue based on information of the descriptor 24 and inputs the frame in the queue. A queue traverse logic part 40 selects the highest priority queue of the top of the queue list and when a prescribed condition is satisfied, the frame is fetched and transmitted. When the length of the selected queue is not shorter than a high level mark and the highest priority queue, the queue list is marked as in a congested state.