Unless you're running a 2 person server it's not worth it host a dedicated server off a adsl line. That's assuming your upload is 128k. Here's how you should discern how many people should be allowed on.
Upload Speed (in this case we'll say 128) which gives you 12-16k upstream transfers.
Each player client spot on the server should be given a minimum of 8000 CPS for reduced lag and smooth gameplay, (our server is 10000) -8K
So with a 128K upstream the most you can host without lag is 2 players. 3 could play but lag and ping would fluctuate. 4 is pushing it. So if you're trying to run a dedicated server, I'd advise against it. If you're just putting it up for you and a friend or two to battle it out, have them manually input your IP and the base port into the "favorites" browser. This directly scans the ip of the server instead of going through the master server. I suggest you just do this as it'd be unrealistic for you to run a dedicated server off an adsl line.