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Weighted fair queueing (WFQ) is a data packet scheduling algorithm used by network schedulers. WFQ is both a packet based implementation of the generalized processor sharing policy (GPS), and a natural generalization of fair queuing (FQ): whereas FQ shares the link's capacity in equal subparts, WFQ allows to specify, for each flow, which fraction of the capacity will be given. Weighted fair queuing (WFQ) is also known as Packet-by-Packet GPS (PGPS or P-GPS) since it approximates generalized processor sharing "to within one packet transmission time, regardless of the arrival patterns." In WFQ, a scheduler handling flows is configured with one weight for each flow. Then, the flow of number will achieve an average data rate of . A WFQ scheduler where all weights are equals is a FQ scheduler. Like all fair-queuing schedulers, each flow is protected from the others, and it can be proven that if a data flow is leaky bucket constrained, an end-to-end delay bound can be guaranteed. == Parametrisation and Fairness == Like other GPS-like scheduling algorithm, the choice of the weights is left to the network administrator. By regulating the WFQ weights dynamically, WFQ can be utilized for controlling the quality of service, for example to achieve guaranteed data rate. As presented for fair queueing, there is no unique definition on what is "fair". Proportional fairness can be achieved by setting the weights to , where is the cost per data bit of data flow . For example in CDMA spread spectrum cellular networks, the cost may be the required energy (the interference level), and in dynamic channel allocation systems, the cost may be the number of nearby base station sites that can not use the same frequency channel, in view to avoid co-channel interference. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Weighted fair queueing」の詳細全文を読む スポンサード リンク
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