Veth devices where created --
ip link add name tstveth mtu 65535 type veth peer name tstveth0 mtu 65535
65535 is the highest MTU these devices support.
They where moved to different namespaces --
ip netns add transfertest
ip link set netns transfertest dev tstveth0
IPs where added to it --
ip netns exec transfertest ip a add fc00::2:2/112 dev tstveth0
ip a add fc00::2:1/112 dev tstveth
sshd was listening on fc00::2:1 with compression disabled.
This command was run to test throughoutput of ssh and the sys CPU utilization --
ip netns exec transfertest ssh -i /etc/mypc/my.key -p 80 de@fc00::2:1 dd bs=10M if=/dev/zero > /dev/null
ip netns exec transfertest ssh -i /etc/mypc/my.key -p 80 de@fc00::2:1 dd bs=10M count=103 if=/dev/zero > /dev/null
For the 65535 MTU, CPU was between 6 and 7, sometimes 5 also. Throughoutput was around 140MB/s
When the MTU was lowered to 1500, the CPU utilization dropped to between 5 and 6%, sometimes goes to 7% and the throughoutput was a little higher.
I blame it on chance, but overall, it doesn't make a difference.