Lag
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Latency is the time taken for a sent packet of data to be received at the other end. It includes the time to encode the packet for transmission and transmit it, the time for that data to traverse the network equipment between the nodes, and the time to receive and decode the data. This is also known as "one-way latency". A minimum bound on latency is determined by the distance between communicating devices and the speed at which the signal propagates in the circuits (typically 70–95% of the speed of light in vacuum). Actual latency is often much higher, due to packet processing in networking equipment, and other traffic.
While strictly every packet experiences lag, the term lag is used to refer to delays noticeable to the user. There is often a correlation between latency and the physical distance that data must travel. Thus the time taken for a packet to travel from a computer server in Europe to a client in the same region is likely to be shorter than the time to travel from Europe to the Americas or Asia. But protocols and well written code that avoid unnecessary data transmissions are less affected by the latency inherent in a network. Modern corporate networks have devices to cache frequently requested data and accelerate protocols, thus reducing application response time, the cumulative effect of latency.
In many online video games such as World of Warcraft and Quake III Arena, the lag is caused by bad connection to the host. Internet lag is undesirable because it disrupts normal game-play. Due to this, many players that have a high latency internet connection are often not permitted, or discouraged from playing with other players or servers that have a distant server host or have high latency to one another. Very often it also causes the death of the player character when it engages in combat. Extreme cases of lag may result in extensive desynchronization of the game state. The game may attempt to correct this by pausing game-play and attempting to fully resynchronize all players. Games that do not or fail in the attempt may simply drop the offending players. A reverse is shown when the player is near to the server geographically, allowing for, in some cases, almost instant transfer of data, and therefore no lag.
In Chinese-language software and online games, the term openly used is 卡 kǎ. Here used colloquially, the original definition of "卡" is stuck or unable to move, which is pronounced qiǎ in this context.
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