Improving soft guarantee service without sacrificing hard delay bound

Supporting a wide range of QoS requirements is becoming increasingly important in packet-switching networks. Many packet scheduling algorithms have been proposed in the literature to provide a hard end-to-end delay bound along a network path. However, we found these algorithms inadequate at supporting a wide range of QoS requirements. Nonwork-conserving algorithms are inefficient because a certain amount of bandwidth is wasted as the server may be idle even when there are packets to be transmitted. Most WFQ-like work-conserving algorithms are imprudent due to their inflexible nature in sharing spare bandwidth. In these algorithms, the spare bandwidth is divided according to the weights of various flows, that is often called fair-sharing, which is in fact the cause of the inflexibility. A new work-conserving algorithm called the biased virtual clock (BVC) algorithm is proposed to alleviate this inadequacy of the work-conserving algorithms through judicious sharing of the spare server capacity. The BVC algorithm substantially improves the performance of soft guarantee service without sacrificing the delay guarantee to hard-delay-bound flows.