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I had a high suspicion about something but today I made measurements. My feeling is that downloading data from OpenBSD use more "upload data" than on other OS
I originally thought about this issue when I found that using OpenVPN on OpenBSD was limiting my download speed because I was reaching the upload limit of my DSL line, but it was fine on Linux. From there, I've been thinking since then that OpenBSD was using more out data but I never measured anything before.
Now that I have an OpenBSD router it was easy to make the measures with a match rule and a label. I'll be downloading a specific file from a specific server a few times with each OS, so I'm adding a rule matching this connection.
match proto tcp from 10.42.42.32 to 145.238.169.11 label benchmark
Then, I've been downloading this file three times per OS and resetting counter after each download and saved the results from "pfctl -s labels" command.
OpenBSD comp70.tgz file from an OpenBSD mirror
The variance of each result per OS was very low, I used the average of each columns as the final result per OS.
OS total packets total bytes packets OUT bytes OUT packets IN bytes IN ----- ------------- ----------- ----------- --------- ---------- -------- OpenBSD 175348 158731602 72068 3824812 10328 154906790 OpenBSD 175770 158789838 72486 3877048 10328 154912790 OpenBSD 176286 158853778 72994 3928988 10329 154924790 Linux 154382 157607418 51118 2724628 10326 154882790 Linux 154192 157596714 50928 2713924 10326 154882790 Linux 153990 157584882 50728 2705092 10326 154879790
A quick look will show that OpenBSD sent +42% OUT packets compared to Linux and also +42% OUT bytes, meanwhile the OpenBSD/Linux IN bytes ratio is nearly identical (100.02%).
Chart showing the IN and OUT packets of Linux and OpenBSD side by side
I'm not sure what to conclude except that now, I'm sure there is something here requiring investigation.
