On the Usage of DSCP and ECN Codepoints in Internet Backbone Traffic Traces for IPv4 and IPv6

Differentiated Services Code Points are values that can be used on IP packets to mark traffic and allow for different Quality of Service treatment during the traversal through a network. Explicit Congestion Notifications are used to indicate that congestion on a network occurred. Both values are encoded in the previously called Type of Service field in the IP header. In this paper, we look at codepoint values for DSCP and ECN in relation to the ports used on the transport layer, which lets us infer the application that is generating the traffic. We provide new measurement data by analyzing traffic from Internet backbone links collected by CAIDA from the months March, April, and May 2018 in New York City. Our results show that DSCP codepoints are rarely used in IPv4 but even less in IPv6. Moreover, most traffic using DSCP codepoints is only using default values and not values designed for prioritization of packets. ECN-enabled traffic is scarce in IPv4, while in IPv6 it appears to be neglectable. However, we could observe differences for certain application traffic in the usage of DSCP and ECN codepoints and elaborate on their distribution.