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TCP congestion control is one of the main offenders in holding back high speed broadband. It can take minutes for TCP to discover the link bandwidth and a singl

• wtallis 10y ago
  Congestion control is as important as ever. Your packets can traverse links of just a few Mbps then 1Gbps then back down to a few Mbps, all within your own house on the way from your computer to your ISP's network. Common consumer networking equipment will do extremely stupid things in the face of congestion, such as storing packets in a FIFO buffer more than one second long. Initial window sizes still need to be small because there will always be users at the fringes of a wireless network where speeds are low enough that a burst of a few dozen full-size packets is a major call-dropping problem. The best solution is for AQM and ECN to be deployed widely, so that congestion can be identified and dealt with before it gets bad enough to require drastic rate decreases. QUIC currently cannot use ECN because those bits of the IP header typically aren't accessible from the APIs for UDP. Modern TCPs operating on networks that keep buffering delays low and signal congestion without dropping packets don't have trouble determining link bandwidth quickly.