Hack the Route Start free Open app TCP performance
Congestion window
The sender's own limit on data in flight, grown while all goes well and cut on loss.
TCP sends no more than the smaller of the receiver's window and its congestion window. It grows fast in
slow start, then more carefully, and is halved when a loss signals congestion. Halving takes more from a big
window than from a small one, which is how strangers come to share a link without coordinating, as long as the queue
drops packets rather than holding them all. ss -ti shows it.