Early Online and Multiplayer Games Figure 2.9 Atari
Early Online and Multiplayer Games Figure 2.11 Screen shots of Doom, the popular First-Person Shooter that started a surge in online, multiplayer gaming. Reproduced by permission of Id Software, Inc. Doom node IPX driver Device driver Network card Local area network Doom node IPX driver Device driver Network card Software Hardware Figure 2.12 The hardware and software layers required to run multiplayer networked Doom Computer Computer Computer Ethernet Modem Modem Computer Computer (a) (b) Figure 2.13 Network topologies used by Doom. Computers connected to an ethernet LAN acted as peers (a), or computers connected by a modem acted as peers (b) Doom used a peer-to-peer topology for networking. All players in the game were independent peers running their own copy of the game and communicating directly with the other Doom peers. Every 1/35th of a second, each Doom game sampled the input from each player (such as move left, strafe, shoot, etc.) and transmitted them to all other players in the game. When commands for all other players for that time interval had been received, the game timeline advanced. Doom used sequence numbers to determine if a packet was lost. If a Doom node received a packet number that was not expected (i.e. the previous packet was lost), it decided that a packet had been lost and sent a resend request (a negative acknowledgement, or NACK) to the sender [DOOMENGINE].
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