Is explicit congestion notification usable with UDP?

This dataset contains initial measurements to determine if Explicit Congestion Notification (ECN) is usable with UDP traffic in the public Internet. Using measurements from the University of Glasgow, two residential networks in Glasgow, and virtual machines running on each of the nine regions of the Amazon EC2 service worldwide, we test reachability of 2500 servers from the public NTP server pool, using ECT(0) and not-ECT marked UDP packets. We show that an average of 98.97% of the NTP servers that are reachable using not-ECT marked packets are also reachable using ECT(0) marked UDP packets, and that ~98% of network hops pass ECT(0) marked packets without clearing the ECT bits. We compare reachability of the same hosts using ECN with TCP, finding that 82.0% of those reachable with TCP can successfully negotiate and use ECN. Our findings suggest that ECN is broadly usable with UDP traffic, and that support for use of ECN with TCP has increased. The data was collected from April-August 2015.