Well so it does not look like I can fix this lag,
This is a info I get from the firewall,
You can see there 21G got dropped as first from that rule - dropping everything which comes from port 19.
While et got only 35M
3 160 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp spt:19
538K 35M ACCEPT udp -- * * 0.0.0.0/0 0.0.0.0/0 udp dpt:27960
So basically interserver will have to fix this hole. As I got also packet loss from a device which comes before b1 - probably a router. Sudd3n will be soon informed.. so fingers crossed.