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0 pointsjandrese6mo ago0 comments

TCP uses the worst congestion control algorithm for general networks except for all of the others that have been tried. The biggest change I can think of is adjusting the window based on RTT instead of packet loss to avoid bufferbloat (Vegas).

Unless you have some kind of special circumstance you can leverage it's hard to beat TCP. You would not be the first to try.

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paulsutter6mo ago· 2 in thread

For serving web pages, TCP is only used by legacy servers.

The fundamental congestion control issue is that after you drop to half, the window is increased by /one packet/, which for all sorts of artificial reasons is about 1500 bytes. Which means the performance gets worse and worse the greater the bandwidth-delay product (which have increased by tens of orders of magnitude). Not to mention head-of-line blocking etc.

The reason for QUIC's silent success was the brilliant move of sidestepping the political quagmire around TCP congestion control, so they could solve the problems in peace

jandreseOP6mo ago

TCP Reno fixed that problem. QUIC is more about sending more parts of the page in parallel. It does do its own flow control, but that's not where it gets the majority of the improvement.

paulsutter6mo ago

TCP Reno Vegas etc all addressed congestion control with various ideas, but were all doomed by the academic downward spiral pissing contest.

QUIC is real and works great, and they sidestepped all of that and just built it and tuned it and has basically won. As for QUIC "sending more parts of the page in parallel" yes thats what I referred to re head of line blocking in TCP.

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