On the Resource Efficiency of Explicit Congestion Notification

Explicit Congestion Notification (ECN) for IP networks has received considerable attention in recent years, and has been shown to improve TCP goodput. Previous studies have centered on scenarios in which TCP with ECN (TCP/ECN) traffic competes with ECN-unaware traffic. This paper presents case studies in which moderately short flows are all ECN-capable, and compare them with the corresponding cases where the flows are ECNunaware, running over drop tail and Random Early Detection routers. Using transmission overhead metrics, we show that TCP/ECN uses network resources more efficiently. We also consider the case of battery-operated devices and show that TCP/ECN is more power conserving than standard TCP. An unexpected outcome of our experiments is that goodput does not improve in an all-TCP/ECN environment.