In computing and especially computer networks, lag (slang) is a symptom where the result of an action appears later than expected. While different kinds of latency are well defined technical terms, lag is the symptom, not the cause.

Latency is the time taken for a packet of data to be sent from onetime for encoding the packet for transmission and transmitting it, the time for that serial data to traverse the network equipment between the nodes, and the time to get the data off the circuit. 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). Actual latency is 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, internet lag is often frowned upon because it disrupts normal gameplay. Due to this, many players that have a lower speed 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. Extreme cases of lag may result in extensive desynchronization of the game state. The game may attempt to correct this by pausing gameplay and attempting to fully resynchronize all players. Games that do not or fail in the attempt may simply drop the offending players.

See also

• Bandwidth - Measure of a connection's maximum data transfer capacity.
• Ping - Tool for determining network latency with regard to another system.
• Avalon - Movie by Mamoru Oshii, in which large parts of the portrayed society play an immense online virtual reality game, features lag as a phenomenon to which players react with bodily symptoms (convulsions, nausea).
• Lagometer - A 'device' that measures lag.
• Input lag

External links

• The Gamer's Guide from Blues News - Lag Section
• It's the Latency, Stupid
• Bandwidth and Latency

de:Lag es:Lag fr:Lag (informatique) ko:? it:Lag (informatica) he:??? ja:?? pl:Lag pt:Latência fi:Viive tr:Lag