BECN for congestion control in TCP/IP networks: study and comparative evaluation

Abstract

This paper evaluates the suitability of Backward Explicit Congestion Notification (BECN) for IP networks. The BECN mechanism has previously been used in non-IP networks, but there has been limited experimental investigation into the application of the BECN scheme as congestion control mechanism in IP networks. In this paper, we consider an enhanced algorithm for BECN which uses Internet Control Message Protocol (ICMP) Source Quenches for backward congestion notification in IP networks and undertake comparative performance evaluation of Random Early Detection (RED), Explicit Congestion Notification (ECN) and our enhanced BECN mechanism using both long-lived TCP bulk transfers and short-lived Web traffic workloads. Our results show that for Web traffic workloads, BECN offers only slight improvement in transfer delay while average goodput for bulk transfers is no worse than that of ECN. For paths that have a high bandwidth delay product our results show that not only can BECN offer significant improvement in average goodput for bulk transfers over the ECN mechanism, but packet drops and transfer delay for short-lived Web traffic connections are also comparatively reduced. Additional observations show that on such paths TCP (NewReno) with RED can offer higher goodput for bulk transfers compared to ECN. We investigate the overhead due to Source Quenches in a BECN capable network and find that for scenarios considered in this paper it does not significantly impact performance of BECN.