Re: TCP: tcp_parse_options: Illegal window scaling value 15 > 14 received

[Casey Deccio <casey@deccio.net>]

On Sep 7, 2022, at 11:46 AM, Jim Popovitch <jim@k4vqc.com> wrote:

I saw some much of the verbose '15 > 14' logs that I just decided to
net.ipv4.tcp_window_scaling=0 and be done with it. Cleared up the
noise, haven't noticed any problems since. ymmv.

Sounds like you've seen a non-trivial amount of this?

Disabling window scaling with net.ipv4.tcp_window_scaling=0 will "fix" the logs, but of course, it will also disable window scaling, which means that you are limiting the size of your congestion window to 64KB.  This effectively limits the throughput of TCP sessions over "long, fat pipes".

Casey