Abstract
This paper outlines the results of an experimental investigation into the dynamics of RFC3168 based Explicit Congestion Notification (ECN), using congestion avoidance methods available in commercial routing equipment. Careful analysis of the packet exchanges and queuing conditions provide insight into TCP ECN's behaviour on production equipment using largely default parameters. We find that the relative performance of ECN and non-ECN enabled TCP depends heavily on the prevailing network conditions. The use of ECN leads to improved goodput and in most instances throughput. However, this improvement comes at the expense of volatile queues leading to instability and degraded performance under certain circumstances.