What ss -timem is actually showing

8 February 2026

ss -timem on a long-lived flow is the closest I get to a bench without adding a probe. rtt, rttvar, cwnd, bytes_acked, bytes_retrans, and the pacing rate are the fields I copy. A large cwnd with rising retransmits is the path, not the application. A tiny cwnd after idle is slow-start-after-idle, which I turn off for these flows.

I do not sample once. I sample at the beginning, after a second, and when the transfer is bored. The first sample is the handshake. The last one is the path I am trying to describe.

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