NETWORK DEVICE

PROBLEM TO BE SOLVED: To preferentially transfer a low-delay packet of a specific user while keeping a contracted bandwidth for each user. SOLUTION: In order to allow priority transfer (fluctuation) over VLL packets while keeping each contracted bandwidth constantly, a leaky bucket system is expanded to have a threshold 1509 for permitting transmission of a packet (e.g. a WFQ packet) other than an LLQ packet and additionally a threshold 1501 (larger than the threshold 1509) for permitting transmission of the LLQ packet (two-threshold leaky bucket system). In this manner, even when a WFQ cannot be transmitted, an LLQ can be transmitted with priority. In addition, while the total bandwidth of the WFQ and LLQ, i.e. the bandwidth of the VLL contains fluctuation, the contracted bandwidth can be kept. The circuit of this two-threshold leaky bucket system is provided in LLQ and WFQ transmission appointed time calculating circuits so as to calculate respective transmission appointed time points so that an LLQ/WFQ is selected and a packet is selected based on these time points considering priority. COPYRIGHT: (C)2011,JPO&INPIT