Online Worlds / MMO

The game stopped living on one machine. Now it has to be synchronized over an unreliable wire — and you cannot cheat ping. The theme of the era: what you put on the wire (state or input), where the authoritative state lives (a shard, a single server) and which economies emerge when thousands of people share one world.

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1997–2005

Networking, persistence, economies

The three canonical netcode models and why each one dictates its own genre; how to hold thousands of players in one persistent world; and what happens when virtual money starts to be worth real money.

Netcode taxonomy: three models~17 min

What we put on the wire: state (client-server) vs commands (lockstep) vs input (rollback). The cost of bandwidth and latency + 🏠 a lag simulator (lab).✦ open

Rollback netcode (GGPO)~18 min

The third model in depth: input prediction, rollback and resimulation, a save state every frame, delay vs rollback. Why fighting games — yes, RTS — no.✦ open

Persistence and sharding~17 min

Where the authoritative state lives when there are thousands of players: WoW's shards vs EVE's single shard + Time Dilation, databases, dupes and zoning.✦ open

Virtual economies~18 min

Bartle, Castronova and "the GNP of Norrath", RMT and gold farms, faucets/sinks and EVE's currency design.✦ open

Module 4 follows the course concept (see CONCEPT.md + ROADMAP.md). The full source text is 04-online-worlds-1997-2005.md. For the client-server model in depth see the lesson "Client prediction" (module 3).