Authority
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SDK 1.1
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Networked entities can be simulated either on a Game Client ("Client authority") or a Simulator ("Server authority"). Authority defines which Client or Simulator is allowed to make changes to the synced properties of an Entity, and in general defines who "runs the gameplay code" for that Entity. An Entity is any networked GameObject.
To learn more about authority, check out this short video:
Client authority is the easiest to set up initially, but it has some drawbacks:
Higher latency. Because both Clients have a non-zero ping to the Replication Server, the minimum latency for data replication and commands is the combined ping (Client 1 to Replication Server and Replication Server to Client 2).
Higher exposure to cheating. Because we trust Game Clients to simulate their own Entities, there is a risk that one such Client is tampered with and sends out unrealistic data.
In many cases, especially when not working on a competitive PvP game, these are not really issues and are a perfectly fine choice for the game developer.
Client authority does have a few advantages:
Easier to set up. No Client vs. Server logic separation in the code, no building and uploading of Simulation Servers, everything just works out of the box.
Cheaper. Depending on how optimized the Simulator code is, running a Simulator in the cloud will in most cases incur more costs than just running a Replication Server (which is comparatively very lean).
Having one or several Simulators taking care of the important World simulation tasks (like AI, player character state, score, health, etc.) is always a good idea for competitive PvP games. In this scenario, the Simulator has authority over key game elements, like a "game manager", a score-keeping object, and so on.
Running a Simulator in the cloud next to the Replication Server (with the ping between them being negligible) will also result in lower latency.
When an Entity is created, the creator is assigned authority over the Entity. Authority can be then at a later point between Clients – or even between Clients and Simulators, or . Regardless, only one Client or Simulator can be the authority over the Entity at any given time.
In addition to key gameplay objects, the player character can also be simulated on the Server, with the Client locally predicting its state based on inputs. You can read more about how to achieve that in the section about .
Peer-to-peer support (without a Replication Server) is planned in a future release. Please see the for updates.
Even if an entity is not currently being simulated locally (the client does not have authority), we can still affect its state by sending a or even .