Since there are new computers and different systems these days out there, you want to ask yourself, How do you play one of my old favorite games doom online? Well of course I have one program that most players use and that actually still play! Its Called ZDaemon of course! (if someone already posted this my bad) Well Zdaemon is very popular because when i get online from time to time you see 16 players on one server and a decent amount of players till play, particulary the dm servers. Most likey 250 players everyday which isn't bad for an old game. Here is the link
http://www.zdaemon.org/ It even has ctf edition with the program.
I also have a review for it
This program is very authentic and it really gets you online to play your all time favorite Doom to Final Doom. You can play all versions of doom, and even third party games such as hexen and Heretic, but mainly it hosts Doom games. You can play many modded dooms to fit for Deathmatches, such as the Dwango Series. You create your own account for the game and its very neat because you can set up your own profile, and have an experiance system that shows your level of play, or how much you play. I recommend this for Multiplayer on doom. I give this a 9/10