This paper proposes an efficient fair queuing algorithm, called Medium Starting Potential Fair Queuing (MSPFQ), which has O(1) complexity for the virtual time computation while it has delay and fairness properties similar to Starting-Potential Fair Queueing (SPFQ). The key idea of MSPFQ algorithm is that it recalibrates the system virtual time to the medium value of the minimum possible virtual start times of HOL packets in each backlogged session. We show that MSPFQ belongs to the class of Rate-Proportional Server (RPS). In addition, we analytically prove that our algorithm has good delay and fairness properties.

WFQ (Weighted Fair Queueing) is an ideal scheduling algorithm in terms of delay and fairness. However, timestamp computation complexity makes the implementation difficult. In this paper we propose an efficient and simple fair queueing algorithm, called Emulated Weighted Fair Queueing (EWFQ), which has O(1) complexity for the virtual time computation while it almost perfectly emulates the delay and fairness properties of WFQ. The key idea of EWFQ is that it calibrates the system virtual time only at the end of each packet transmission, while it calculates the system virtual time for a newly arrived packet by employing a linear approximation. By doing so, EWFQ has a rate-proportional property. EWFQ can be implemented in a router for supporting the differential and integrated services.

OpenFlow, originally proposed for campus and enterprise network experimentation, has become a promising SDN architecture that is considered as a widely-deployable production network node recently. It is, in a consequence, pointed out that OpenFlow cannot scale and replace today's versatile network devices due to its limited scalability and flexibility. In this paper, we propose OpenQFlow, a novel scalable and flexible variant of OpenFlow. OpenQFlow provides a fine-grained flow tracking while flow classification is decoupled from the tracking by separating the inefficiently coupled flow table to three different tables: flow state table, forwarding rule table, and QoS rule table. We also develop a two-tier flow-based QoS framework, derived from our new packet scheduling algorithm, which provides performance guarantee and fairness on both granularity levels of micro- and aggregate-flow at the same time. We have implemented OpenQFlow on an off-the-shelf microTCA chassis equipped with a commodity multicore processor, for which our architecture is suited, to achieve high-performance with carefully engineered software design and optimization.