The 20 bps are caused by synchronizing the system time from server to the clients. The time is needed for dead reckoning. I admit that this is sort of superfluous when nothing moves. 20 bps are not much, but we'll change that so that nothing is sent when nothing moves or dead reckoning is switched off.

Setting the ping rate to 99999 won't have any effect. The ping rate is only used when no entity updates are sent.

DirectPlay causes not more traffic than Enet. The "overhead" of DirectPlay is a programming overhead, not a traffic overhead. The "bad Directplay traffic" is one of the typical rumors circulating among newbie developers. Some time ago there was a forum uproar about the use of Directplay and subsequently we tested DirectPlay against Enet in the engine. It turned out that there was no difference in traffic and packet length. Still, we'll probably switch to Enet or Raknet some day for psychological reasons.