Rapid Startup of Congestion Control

This document defines Rapid Start, a congestion-control startup algorithm. It starts by pacing first full flight over a full RTT, allowing an initial window up to 2× that of classic paced slow start at a comparable sending rate. It then grows the window by 3× per RTT until queue buildup is observed, after which it reverts to classic 2× slow start growth. When congestion is signaled, Rapid Start smoothly converges the window based on delivered data, avoiding bursts and underutilization, before handing over to ordinary congestion avoidance.