Alibaba.com offers 1,068 overload generator products. About 5% of these are Diesel Generators, 0% are Gasoline Generators, and 0% are Generator Parts & Accessories. A wide variety of overload generator options are available to you, such as usage, type, and certification.
This essentially overloads the server, and players are left with the 'Reliable Packet 1' error notification on their screen. A single server can only accommodate a fixed amount of players, and until someone leaves, the chances of 'Reliable Packet 1' error popping up is pretty high.
A server overload is one type of DoS, but DoS can mean any type of denial of service, whether it its CPU, network, disk or other service. Mitigation is a good idea, but the problem with DDoS is that an attacker can use thousands of devices to attack you, which means your mitigation strategy needs to be very robust, not only dealing with load but deflection techniques.