I’m trying to improve my TCP throughput over a “high delay network” between Linux machines.
tcp_rmem to “8192 7061504 7061504”.
wmem_default to “7061504”.
txqueuelen to 10000.
tcp_congestion_control to “scalable”.
I’m using “nist” (cnistnet) to simulate a delay of 100ms, and the BW I reach is about 200mbps (without delay I reach about 790mbps).
I’m using iperf to perform the tests and TCPTrace to analyze the results, and here is what I got:
On the receiver side:
max win adv: 5294720 bytes
avg win adv: 5273959 bytes
sack pkts sent: 0
On the sender side:
actual data bytes: 3085179704
rexmt data bytes: 9018144
max owin: 5294577 bytes
avg owin: 3317125 bytes
RTT min: 19.2 ms
RTT max: 218.2 ms
RTT avg: 98.0 ms
Why do I reach only 200mbps? I suspect the “owin” has something to do with it, but I’m not sure (these results are of a test of 2 minute. A 1 minutes test had an “avg owin” of 1552900)…
Am I wrong to expect the throughput to be almost 790mbps even if the delay is 100ms?
(I tried using bigger numbers in the window configurations but it didn't seem to have an effect)