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An argument for increasing TCP's initial congestion window (2024)

Introduction Google has a long history of performing networking research, making changes, and pushing those changes to the entire internet. In 2011, they published one of my favorite papers, which described their decision to increase the TCP initial congestion window from 1 to 10 on their entire infrastructure. This was soon followed by an RFC filed with the IETF, and eventually became an internet standard. I think it’s time to revisit that paper and update Google’s recommendations for the modern Internet.

Eventually, in a long connection, the congestion window will settle in to a relatively narrow set of values, and this steady state condition is called convergence. Depending on the round trip time of the connection, convergence can occur within 1 or 2 seconds, which isn’t too long for a file transfer that’s expected to take several minutes. A packet trying to exit a low bandwidth link could be stuck waiting in that buffer for a long time before it makes it back onto the network.

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