The Fast and the Spurious: Congestion Control Experimentation in Firefox's QUIC stack

This talk gives a rundown of various potential improvements being thought about and experimented on for the CUBIC Congestion Control implementation in Neqo, Firefox's QUIC stack. Detecting and recovering from Spurious Congestion Events -- network hiccups mistaken as congestion signal. Reacting differently to Explicit Congestion Notifications (ECN) than to packet loss. Optimizing the Slow Start exit point to avoid unnecessary loss through various heuristics.

While many of these make sense on paper and produce good results in simulations the reality of the internet is much more complicated. One ongoing challenge is designing metrics that measure impact of change in the real world without getting lost in the noise of wildly varying network conditions across millions of internet users to validate that those improvements genuinely make Firefox quic(k)er.