Netcode

Netcode is a blanket term for anything that somehow relates to networking in online games; netcode is a term most commonly used by gamers when discussing synchronization issues between clients and servers. The actual elements of a game engine that can cause so-called "netcode issues" include, among other things, latency, lag compensation or the lack thereof skill, simulation errors, and network issues between the client and server that are completely out of the game's hands. Netcode as a term tends to be used only in the gaming community, as it is not recognized as an actual computer science term.

Latency is an unavoidable fact of online games, caused by not only network latency, which is largely out of a game's control, but also latency inherent in the way game simulations are run. There are several lag compensation methods used to disguise, reduce, or cope with latency, however their feasibility varies by application.

A single update of a game simulation is known as a tick. The rate at which the simulation is run on a server is referred often to as the server's tickrate; this is essentially the server equivalent of a client's frame rate, absent any rendering system. Tickrate is limited by the length of time it takes to run the simulation, and is often intentionally limited further to reduce instability introduced by a fluctuating tickrate, and to reduce CPU and data transmission costs. A lower tickrate increases latency in the synchronization of the game simulation between the server and clients. Tickrate for games like first-person shooters can vary from 60 ticks per seconds for games like Quake or Counter-Strike: Global Offensive in competitive mode to 30 ticks per seconds for games like Battlefield 4 and Titanfall. A lower tickrate also naturally reduces the precision of the simulation, which itself might cause problems if taken too far, or if the client and server simulations are running at significantly different rates.

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