This paper looks at a mechanism related to Explicit Congestion Notification. It uses a single bit in the IP header to communicate the congestion at each hop in the path. Statistical estimators are used to work out the accuracy of the congestion estimation.
Protocols used in networking such as TCP or IP.
The central suggestion is that centrally controlled SDN networks are in a position to choose which version of TCP will work best. OpenTCP tunes TCP for traffic and network conditions. Different TCP flavours perform better at different times or in different conditions e.g. datacentre TCP (DCTCP).