[SNYPE00]

What type of internet connection are you running? That is one of the biggest factors in a smooth running server. You will need lots of bandwidth to run 20 player games. If you are running this one a cable modem you will have trouble with that many players.
Go to Bandwidthplace.com and test your server's connection upload speed. Next use this formula to determine how many players you can adequately run on your server: (#players)x(max_rate)<(svr conn upload speed/8). Your max_rate is set in your server.cfg file and by default is set at 9000. If you exceed the server connection's ability to upload data to clients then you are in for some serious lag and "Connection timed out" messages.