Abstract: The strategy of differentiated service based on process allocation only concerns connection delay, but when the bandwidth of Web server is over-subscribed, such method is ineffective because the processing delay becomes the dominant factor of client perceived delay. This paper proposed a QoS strategy using two-level fuzzy control,by adjusting the bandwidth of virtual hosts that sever the different priority requests, the self-tuning fuzzy controller could affect the processing delay and achieve the proportional delay guarantee. The stability analysis and experimental results demonstrate that the proposed approach achieves a better performance in terms of the proportional delay variance to the target. The self-tuning fuzzy controller outperforms the static fuzzy controller by 40% on average.

Key words: Differentiated service,Self-tuning fuzzy control,Proportional delay guarantee