I was looking through the session types and I am a bit confused. For the moment I have gone with systemlink because I can have up to 31 players and it fits my needs. I noticed in its description, it outlines that you can only have players connect on the same local subnet. Does this mean that say, a friend in California, can't play or am I understand it wrong. I am ultimately hoping to achieve a server that people can connect to nationally for the moment. I just need some clarity and understanding. Thanks in advance

System Link is for Xboxes on your local network.  You want to go with the Matchmaking option for over the internet play.

You generally want to use system link for local testing (because it does not require any special subscriptions on the Windows side), but then switch to player match when your game is finished and people want to play it over the Internet.

Many games actually include menu options for both, so players can choose what type of networking they want to use.

http://blogs.msdn.com/shawnhar/archive/2007/11/21/system-link-networking-in-xna-game-studio-2-0.aspx

Thanks for all the help guys ^^