Just got me a new 100Mbit fiber which is connected to a PC running RouterOS. We are having some performance issues that our telco claims is caused by our firewall. In general we have less than 10% CPU load on the firewall so this is not the issue. Telco claims that the TCP recieve window of the NAT engine is too low to really use the potential of the line. Now i wonder where to set the TCP recieve window? This can be done easily on Win/Linux..