UDP for data?

[Philipp Marek]

> I'm very interested in making SSH use UDP for large data chunks. Maybe
> you know FASP
> (https://en.wikipedia.org/wiki/Fast_and_Secure_Protocol), but that is
> proprietary, although the website says it's based upon open source
> methods.
> 
> Is it possible to make openssh work with UDP for this purpose?
I guess your original problem is

     SSH/SCP/RSYNC etc. is too slow.

The right solution to that depends on the exact use case.


a) High speed low latency connection (LAN, 10Gbit) -
    Tune your TCP stack and choose a _very_ fast encryption
    algorithm in SSH

    sysctl for Linux:
      net.ipv4.tcp_rmem = 65536        131072   6291456
      net.ipv4.tcp_wmem = 65536        131072   4194304


b) High speed high latency connection (WAN, 1Gbit) -
    Above, plus choose a different congestion control.
    $ sysctl net.ipv4.tcp_congestion_control
    will give the current set one; which are available
    depends on the installed kernel modules.
    ("depmod -n | grep tcp_" might be a first hint)

ISTR that there was/is a way to choose the congestion
control via iptables or per-program or so, but I don't
remember the details offhand.