id's lead programmer John Carmack updated his .plan with his experiences while playing Quake III Arena on a 28.8 modem, resulting in finding "a case of the stuck-at-awaiting-gamestate problem" that should now be fixed. There is a series of tips for modem players to help them still find a good game, and the long update concludes with a pair of new options that he implemented to allow server operators to determine the kind of players that can connect to their games:

I just implemented "sv_minPing" / "sv_maxPing" options so servers can restrict themselves to only low ping or high ping players. This is done based on the ping of the challenge response packet, rather than any in-game pings. There are a few issues with that -- a LPB may occasionally get into a HPB server if they happen to get a network hiccup at just the right time, and the number used as a gate will be closer to the number shown in the server list, rather than the number seen in gameplay. I would reccomend "sv_minPing 200" as a reasonable breakpoint.