Bellairs Games Workshop. Massively Multiplayer Games

Transcription

1 Bellairs Games Workshop Massively Multiplayer Games Jörg Kienzle McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 1

2 Outline Intro on Massively Multiplayer Games Historical Perspective Technical Challenges Game Architectures Network Architectures McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 2

3 What is an MMOG Massively Multiplayer Online Game Large number of players Vastly distributed geographic area Each player assumes an identity and interacts with the others in a shared environment / virtual world in real-time Persistent worlds Other names MMG, MMORPG, MMOPW McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 3

4 What is Shared Shared sense of space Environment and other players Shared sense of presence Each player controls an avatar Shared sense of time A way to communicate Gestures, textual messages, audio A way to share Environment reflects the actions of the players A sense of fairness McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 4

5 Challenge: Games must be fun! Richly detailed environment Highly interactive McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 5

6 Historical Perspective (1) 1980: Multi-User Dungeons (D&D style game) Text based Ran on a single mainframe / centralized database 1000 s 1985: Habitat (virtual world), Rabbitjack s Casino, Yserbius, Air Warrior Commodore s McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 6

7 Historical Perspective (2) 1990: Neverwinter Nights AOL 1995: Meridian 59 Internet based Flat fee 1997: Ultima Online > Kingdom of the Winds, Lineage, Everquest, Asherons Call, Dark Age of Camelot, Star Wars Galaxies, The Sims Online, Shadowbane, World of Warcraft, Middle Earth Online, The Matrix Online, etc McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 7

8 Technical Challenges (1) Network Bandwidth Increasing needs Details of the environment Number of players Fixed resources Each player has a limited bandwidth Bandwidth of provider is expensive Network Latency Messages take time to travel from one node to another Varying latency Out-of-date information vs. real-time McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 8

9 Technical Challenges (2) Distributed Consistency Consistent world views for all players Actions based on inconsistent views have to be consolidated Lack of consistency Hampers the level of immersion of a player Can be exploited to gain unfair advantage Fault Tolerance Insulate users from failures of components (network, hardware, servers) or other players Transparent recovery Visible failures can be costly / damage reputation McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 9

10 Technical Challenges (3) Administration and Live Production Delivery of game does not finish once the game hits the shelves 24x7 service commitment: new features, additional content No interruption of user experience Cheating Disastrous consequences 3% of players Security and Privacy McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 10

11 Technical Challenges (4) Scalability Partition and distribute computational tasks such that Each participant is aware of all the information that is relevant for him / her Each computing device participating in the game is not overloaded The capacity of the network resources available for the game is not exceeded The size of the concurrent user set and of the virtual environment can be increased without requiring architectural changes to the game McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 11

12 MMOG Architectures Game Architecture Shards Zones Seamless Worlds Network Architecture Client / Server Peer-to-Peer McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 12

13 Shards (1) Partition the space into severl logical instances Parallel universes / different worlds Each shard server can handle a fixed maximum amount of players McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 13

14 Advantages Shards (2) Easy to implement No consistency problems No inter-shard communication required Adding new shards is easy Disadvantages Players (friends!) might be isolated Individual shards do not scale McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 14

15 Zoned Worlds (1) Divide the world into distinct zones Provide means for players to travel between zones McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 15

16 Zoned Worlds (2) Advantages Benefits of shards without seggregation of users Server failures are isolated to players in a zone Can be combined with shards -> zoned shards (the most used architecture these days) Disadvantages Discontinuity of game play Zones do not scale easily Late players miss interesting parts of the game McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 16

17 Seamless Worlds Transparent zones Servers must interact to transfer objects between zones Advantages Non-stop play Dynamic zones provide load balancing capabilities No segregation Disadvantages Complex implementation Has to support player interaction between zones Designing game content to respect zone boundaries McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 17

18 Client - Server (1) Dedicated game servers Clients do not communicate directly Partition the clients / environment across multiple servers Servers communicate directly with each other Server is responsible of forwarding client messages to other interested clients McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 18

19 Client - Server (2) McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 19

20 Client - Server (3) Gateway / front-end servers forward messages to zone servers McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 20

21 Client - Server (4) Gateways facilitate Fault tolerance Dynamic zones Physics Servers Scalability Servers managing different interaction types Front-end Servers AI Servers Database Servers Physics / AI / player interaction Game Servers McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 21

22 Client - Server (5) Advantages Well understood Easy administration, consistency, security Central control Hierarchical models in principle scalable Grid computing ideas can be applied Disadvantages High latency High and unpredictable investment cost in servers McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 22

23 Peer-to-Peer (1) Every node is considered an equal peer to the others Direct communication between players Active area of research in MMOG McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 23

24 Peer-to-Peer (2) Advantages Lower hardware and bandwidth cost Potentially highly scalable (the more players, the more resources) Low latency Fault tolerance possibilities Challenges Peer-to-peer systems do not require a fixed subset of resources to be available at all time Security and Privacy Issues Cheating Network attacks / unfair computation Administration, Maintenance, Debugging Varying resources McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 24

25 Questions McGill Games Workshop - Bellairs, 2005, Jörg Kienzle Slide 25