The fun of using TCP for an MMORPG

ABSTRACT

Massive multi-player online games have become a popular, fast growing, multi-million industry with a very high user mass supporting hundreds or thousands of concurrent players. In many cases, these games are centralized and every player communicates with the central server through a time-critical unicast event stream. Funcom's Anarchy Online is one of these; it is based on TCP. We find that its kind of traffic has some interesting properties that inspire changes to protocol or architecture.

In these game streams, TCP does not back off, using TCP does not have to be slower than using UDP, and almost only repeated timeouts ruin the game experience. Improving the latter in the sender implementation does not impose any remarkable penalty on the network. Alternatively, a proxy architecture for multiplexing could save about 40% resources at the server, allow congestion control to work and also reduce the lag of the game.

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INDEX TERMS

Keywords:
MMORPGs, TCP performance, thin streams