Delay-gradient congestion control

Most of the dependence on packet-loss signaling is a consequence of not being able to trust the peer. Packet loss is a reliable signal, for a very specialized definition of "reliable". In cases where you control both ends of a connection, rate of change of transit time is a much better measure of congestion.

The problem with transit time as a measure is that the useful lifetime of a single measurement is less than an RTT, and the end that has the measurement is not the end that needs it. Control theory directly addresses that problem at its root: the sender needs a prediction of the transit time according to a model controlled by frequent updates from the receiver. Given a trusted remote endpoint, you can do much, much better by entirely ignoring packet loss.