University of Oslo University of Oslo Internet For Things (I4T) Research Group University of Aberdeen Recent Active Queue Management (AQM) mechanisms allow for burst tolerance while enforcing short queues to minimise the time that packets spend enqueued at a bottleneck. This can cause noticeable performance degradation for TCP connections traversing such a bottleneck, especially if there are only a few flows or their bandwidth-delay-product is large. An Explicit Congestion Notification (ECN) signal indicates that an AQM mechanism is used at the bottleneck, and therefore the bottleneck network queue is likely to be short. This document therefore proposes an update to RFC3168, which changes the TCP sender-side ECN reaction in congestion avoidance to reduce the Congestion Window (cwnd) by a smaller amount than the congestion control algorithm's reaction to inferred packet loss.