The lockstep protocol is a ''partial'' solution to the look-ahead cheating problem in

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architecture

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, in which a cheating client delays their own actions to await the messages of other players. A client can do so by acting as if they're suffering from high latency; the outgoing packet is forged by attaching a time stamp that is prior to the actual moment the packet is sent. To avoid this method of cheating, the lockstep protocol requires each player to first announce a "commitment" (e.g. hash value of the action); this commitment is a representation of an action that: * Cannot be used to infer the action; and * Easily compares whether an action corresponds with a commitment. Once all players have received the commitments, they reveal their actions, which are compared with the corresponding commitments to ensure that the commitment is indeed the sent action."Cheat-Proof Playout for Centralized and Distributed Online Games"
Baughman and Levine, 2001

Drawbacks

As all players must wait for all commitments to arrive before sending their actions, the game progresses as slowly as the player with the highest latency. Although this may not be noticeable in a

turn-based game In video and other games, the passage of time must be handled in a way that players find fair and easy to understand. This is usually done in one of the two ways: real-time and turn-based. Real-time Real-time games have game time progress cont ...

, real-time online games, such as

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, require much faster reactions. This can be acquired by placing a limit on the time in which a player can announce their action. If no action is sent within this period, other players do not announce their actions to that player and ignore any action that arrives too late.

Asynchronous lockstep protocol

To overcome the obvious drawback of the simple lockstep protocol, an

asynchronous Asynchrony is the state of not being in synchronization. Asynchrony or asynchronous may refer to: Electronics and computing * Asynchrony (computer programming), the occurrence of events independent of the main program flow, and ways to deal with ...

variant of the protocol exists wherein players advance in time free of any negotiations with other players until interaction between players exists, known as a "lockstep mode." This mode may be defined by a certain area around a player, such as a sphere, in which the game world may be affected by the player. Such an interaction can only occur when, for example, the areas of influence surrounding two players intersect.

External links

* '
Archers on a 28.8
'', a comprehensive write-up by

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and

Paul Bettner Zynga with Friends (formerly Newtoy, Inc.) was a video game developer founded in 2008 by brothers Paul Bettner and David Bettner, and their cousin Michael Chow. In November 2008, Newtoy, Inc. released its first game for the iPhone and iPod touch ...

, who developed the lock-step protocol for Age of Empires.

References

{{Reflist Cheating in video games Network protocols