WFQ的两种简化实现方法及性能分析

结合OTPS（One Timestamp Per Session)，提出并实现了两种改进IP网络QoS的方法：基于系统时钟的TWFQ和基于虚拟已发送比特的BWFQ的分组公平排队算法。与WFQ相比，TWFQ的虚拟时间更新算法只需要为一个队列维护一个虚拟结束时间，存储和计算开销大幅降低；与TWFQ相比，只有当报文到达空队列时或者报文离开时该队列非空。BWFQ才更新系统虚拟时间，从而极大地减少了虚拟时间更新的次数。理论分析和计算机仿真结果证明了TWFQ可以获得和WFQ同样的性能，但运算开销下降。BWFQ运算量比TWFQ更小，对硬件要求更低，但由于引入一定的误差，使其不适合重负荷环境。

Two simple implementation algorithms of WFQ and their performance analysis

By considering One Timestamp Per session (OTPS), two new algorithms for improving the IP network Quality of Service (QoS), Time based Weighted Fair Queuing (TWFQ) algorithm and Bit based Weighted Fair Queuing (BWFQ) algorithm, are proposed and realized. The virtual times for TWFQ and BWFQ are obtained from the system clock and the virtual bits that the system has sent respectively. In TWFQ, by contrast with WFQ, only one virtual finish time is maintained for one queue, and the storage cost and computing cost are all decreased. In BWFQ, the virtual time is only updated when one packet arrives at an empty queue, or when the queue is not empty with its head packet leaving, which greatly reduces the system virtual time updating rate than WFQ and TWFQ. Both theoretical analysis and simulation show that TWFQ has the same performance as WFQ; however, it has a less computing overhead. Compared with TWFQ, BWFQ has a much less computing overhead and fewer requirements for hardware, but the cost of the system performance deterioration makes it unfit for high load situation.