Institut Eurécom Service Differentiation by Means of Packet Scheduling

This document presents Shortest Queue First (SQF) packet scheduling algorithm, as a solution to improve Internet access on ADSL links. This queuing policy provides implicit service differentiation, avoiding the need of packet marking and resource reservation associated to usual Quality of Service (QoS) architectures like Differentiated Services (DiffServ) and Integrated Services (IntServ). SQF is compared with two existing alternative disciplines, First In First Out (FIFO) and Stochastic Fairness Queuing (SFQ), and several experiments are performed in order to underline aspects of each algorithm in different scenarios. Some of the most significant results are presented here to help understand advantages and drawbacks of each scheduler and how they behave in these different situations. Results show that SQF fully meets its design goals, outperforming both FIFO and SFQ in all the tests. Effectiveness of the algorithm is also evaluated in a demo. Real-world programs are used in some common home scenarios: everyday usage situations are reproduced adopting different schedulers in order to highlight the difference in quality of service perceived by users. This provides a definitive proof of high performances given by SQF algorithm, making it the best candidate solution for QoS on ADSL Internet access.