Improving video streaming over WAN

BBRv3 vastly improves reliability of video streaming over a high latency link.

CachyOS is the only Linux distro that has this builtin to its kernel. It must be enabled manually.

Some sysctls are needed to increase TCP buffer sizes. See also this thread:

# BBRv3
net.ipv4.tcp_congestion_control = bbr
net.core.default_qdisc = fq
# Needed for cloudflared quic:
# https://github.com/cloudflare/cloudflared/issues/1176
# It may also be needed for BBR:
# https://groups.google.com/g/bbr-dev/c/Yj2_WCBtXpQ/m/S2976NUzEQAJ
# Note: Setting _default settings affects non-IP sockets as well.
net.core.rmem_max=900000000
net.core.wmem_max=900000000
net.ipv4.tcp_wmem=4096 262144 900000000
net.ipv4.tcp_rmem=4096 540000 900000000

iperf3 examples

Without BBRv3 (default Debian 12 kernel)

[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec  1.15 MBytes  9.67 Mbits/sec
[  5]   1.00-2.00   sec  2.52 MBytes  21.1 Mbits/sec
[  5]   2.00-3.00   sec  1.78 MBytes  15.0 Mbits/sec
[  5]   3.00-4.00   sec  2.30 MBytes  19.3 Mbits/sec
[  5]   4.00-5.00   sec  1.24 MBytes  10.4 Mbits/sec
[  5]   5.00-6.00   sec  1.24 MBytes  10.4 Mbits/sec
[  5]   6.00-7.00   sec  1.55 MBytes  13.0 Mbits/sec
[  5]   7.00-8.00   sec  1.36 MBytes  11.4 Mbits/sec
[  5]   8.00-9.00   sec  1.37 MBytes  11.5 Mbits/sec
[  5]   9.00-10.00  sec  1.58 MBytes  13.3 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.17  sec  19.1 MBytes  15.7 Mbits/sec  288             sender
[  5]   0.00-10.00  sec  16.1 MBytes  13.5 Mbits/sec                  receiver

With BBRv3

me@client:~$ iperf3 -c my.server.org -R
Reverse mode, remote host my.server.org is sending
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   764 KBytes  6.26 Mbits/sec
[  5]   1.00-2.00   sec  14.3 MBytes   120 Mbits/sec
[  5]   2.00-3.00   sec  13.7 MBytes   115 Mbits/sec
[  5]   3.00-4.00   sec  10.1 MBytes  85.0 Mbits/sec
[  5]   4.00-5.00   sec  12.2 MBytes   103 Mbits/sec
[  5]   5.00-6.00   sec  11.1 MBytes  93.0 Mbits/sec
[  5]   6.00-7.00   sec  12.4 MBytes   104 Mbits/sec
[  5]   7.00-8.00   sec  11.7 MBytes  98.1 Mbits/sec
[  5]   8.00-9.00   sec  13.6 MBytes   114 Mbits/sec
[  5]   9.00-10.00  sec  13.7 MBytes   115 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.16  sec   117 MBytes  96.3 Mbits/sec  900             sender
[  5]   0.00-10.00  sec   114 MBytes  95.3 Mbits/sec                  receiver