Public Server MMO’s

1. Public Server MMO’s

2. What’s an MMO? Massively Multiplayer Online game Persistent world Success stories Lineage World of Warcraft Public Server MMO

3. MMO • MMO problems • Huge scalability issues • Hosting costs: 20% of subscription revenue • Support costs: 20% of subscription revenue • Content costs: Unknown but surely large • Those are for successful MMO’s • Unsuccessful ones have the cost of failure

4. Public Server • What’s a public server game? • Game company distributes the server code • Users host the machines themselves • Users can modify the server • Examples • Half-life, Counter-Strike, Doom • Neverwinter Nights • Benefits • User hosting resources are extremely plentiful! • User content creation extremely plentiful • Drawback • No subscription model • No persistent world

5. Public Server resources are plentiful 70% of all servers are empty CDF of fullness of Counter-strike servers

6. Public Server content is plentiful

7. Our Goal: Public Server MMO • Decrease hosting and support costs by not hosting gameplay • Decrease development costs by allowing user-generated content • Allow for a persistent world with public servers

8. Basic Architecture • Public Servers host game play • Publisher hosts authentication, billing, loot server • Users store persistent data themselves • Key challenges • Authentication • Persistent Content across public servers • Trading Items

9. Billing Authentication Public Server MMO Participants Loot Publisher Public Server Client

10. Authentication keys • Clients must be able to authenticate themselves to loot server, public servers • Cli_key_pub, Cli_key_priv • Clients keep private key • Loot server must be able to sign loot, as authentic • Loot_key_pub, Loot_key_priv • Loot server keeps private key • Loot server must be able to bind loot to specific players • Bindi_key_pub , Bindi_key_priv • Loot server keeps private keys

11. Challenge: Persistent Content • Content creation • Loot is designed by community and approved by publisher • Loot is issued according to authenticated player-minutes to servers • Servers distribute loot according to game-play • Content security • Loot is signed to a player and signed to the loot server • Public servers and other players check a piece of loot by checking signatures • Loot can be stored at the clients • Caveat: loot cannot be traded from players

12. Challenge: Authenticated Time • How are player minutes authenticated? • Public servers want minutes • Players want minutes • Use a periodic Reverse Turing test that fits in with game-play as a mini-game • Finding objects in a scene • Identifying human faces

13. Challenge: Trading Items • We would like to relax the “loot cannot be traded” restriction for game-play purposes • We don’t want to allow item duping • We don’t want to keep an item revocation list • Solution: periodic trading window • Publisher coordinates a player-wide swap meet or auction • During auction, each player’s goods are re-issued • Old items are invalidated by changing Loot_key_pub, Loot_key_priv

14. Item 1 Item 2 Item 3 attributes Signatures bind_key_p1 loot_key attributes Signatures bind_key_p2 Loot_key attributes Signatures bind_key_p2 Loot_key Trading Illustration Mint Player 2 Player 1 Submit items to mint

15. Item 1 Item 2 Item 3 attributes Signatures bind_key_p2 loot_key’ attributes Signatures bind_key_p1 Loot_key’ attributes Signatures bind_key_p1 Loot_key’ Trading Illustration Mint Player 2 Player 1 Receive new items

16. Quantifiable elements • Re-minting all items in the world: # of items vs. time • Generating / verifying CAPTCHA’s: # of captcha’s vs. time

17. Conclusion

18. scratch • How can we prevent servers from giving players loot for doing nothing • We don’t! • We do require players to be present at the keys, and we assume they will gravitate towards compelling content • Bootstrapping: why go to a new server? • Trickle some loot to a server just for being up

19. A A P A Game Server E E