Selective packet dropping for VoIP and TCP flows

The adoption of the IP protocol for serving diverse applications arises the need for mechanisms to prevent network congestion in scenarios with different traffic types (responsive and unresponsive) sharing limited network resources. To deal with this issue, a number of algorithms for active queue management (AQM) have been proposed. However, most of them do not observe the traffic type and usually disregard this knowledge. In this way, the provided service could not comply with the distinctive requirements of the different type of traffic, such as VoIP services, which demand bounded packet latency and loss rate. This paper proposes a new approach to be applied for preventing network congestion in AQM routers. Our scheme includes a procedure for selecting the packet to be dropped that improves the fairness among different classes of flows. We evaluate the use of this approach on distinct AQM schemes in scenarios with different degrees of UDP and TCP traffic mix. Objective and subjective performance measurements are reported. The experimental evaluation indicates that our approach improves the fairness among different traffic classes without using any packet scheduler. In fact, it also improves the VoIP traffic performance in terms of packet dropping probability, MOS (Mean Opinion Score) and intelligibility. We also show that our approach has no negative impact on the packet delay. Moreover, it is not achieved at the expense of TCP responsive traffic. This work has been partially supported by the Spanish Science and Innovations Ministry (MICINN) Project TIN2009-13992-C02-02, and by the University of Granada (SPAIN)—Plan Propio 2009. E.P. Alvarez-Flores · J.J. Ramos-Munoz · P. Ameigeiras · J.M. Lopez-Soler ( ) ETSI Informática y de Telecomunicación, 18071 Granada, Spain e-mail: [email protected]