Lag
Encyclopedia
Lag is a common word meaning to fail to keep up or to fall behind. In real-time applications, the term is used when the application fails to respond in a timely fashion to inputs. The most common use regards online gaming when the game doesn't respond in sync with the player's controls, usually due to a slow internet connection, server latency or overworked hardware.
Lag is also often used in reference to video games to describe to the delay (or latency) between an action by a player and the reaction of the game.
In distributed applications (such as MMORPGs
), lag is often caused by communication latency
, which 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 because of packet processing in networking equipment, and other traffic.
The term lag is often also used as a synonym for communication latency
. This can be misleading because there can be other causes for the symptom.
or a turn-based game with a low pace may have a high threshold or even be mostly unaffected by high delays, whereas a twitch gameplay game such as a first-person shooter
with a considerably higher pace may require significantly lower delay to be able to provide satisfying gameplay. But, the specific characteristic of the game matter. For example, fast chess is a turn-based game that is fast action and may not tolerate high lag. And, some twitch games can be designed such that only events that impact the outcome of the game introduce lag, allowing for fast local response most of the time.
, Final Fantasy XI
, Call of Duty
, Adventure Quest Worlds, RuneScape
, League of Legends
, Heroes of Newerth
, etc. incur online lag
due to a combination of local and remote processing lag and communications latency, and user tolerance for lag depends highly upon the type of game, similarly as it does for local gaming. In general parlance, the round-trip network latency between a client game and the host server is referred to as the client's ping
time.
is a type of online gaming where the entire game is hosted on a game server in a data center, and the user is only running a thin client
locally that forwards game controller
actions upstream to the game server. The game server then renders the next frame of the game video which is compressed using low-lag video compression and is sent downstream and decompressed by the thin client. For the cloud gaming experience to be acceptable, the round-trip lag of all elements of the cloud gaming system (the thin client, the Internet and/or LAN connection the game server, the game execution on the game server, the video and audio compression and decompression, and the display of the video on a display device
) must be low enough that the user perception is that the game is running locally. Because of such tight lag requirements, distance considerations of the speed of light
through optical fiber
come into play, currently limiting the distance between a user and a cloud gaming game server to approximately 1000 miles, according to OnLive
, the only company thus far operating a cloud gaming service.
Cloud gaming is a very new technology, but early tests have shown that in practice, cloud gaming lag is only slightly higher than local console lag. For example, Unreal Tournament 3 incurs up to 133ms of lag on a console and was tested in July 2010 as incurring 150ms in lag on OnLive
, resulting in the assessment in July 2010 that "Out of controlled conditions, OnLive has managed to get within spitting distance of console response times". In September 2010, reviewers reported a steady reduction in lag due to constant improvements in the technology, to the point where "the actions on screen were one-to-one with my input controls. In fact, I forgot that it wasn't running natively on my PC."
Lag is also often used in reference to video games to describe to the delay (or latency) between an action by a player and the reaction of the game.
In distributed applications (such as MMORPGs
Massively multiplayer online role-playing game
Massively multiplayer online role-playing game is a genre of role-playing video games in which a very large number of players interact with one another within a virtual game world....
), lag is often caused by communication latency
Latency (engineering)
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...
, which 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 because of packet processing in networking equipment, and other traffic.
The term lag is often also used as a synonym for communication latency
Latency (engineering)
Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...
. This can be misleading because there can be other causes for the symptom.
Lag in local video gaming
All video games incur some lag, since once an input from the player is received, the game must compute the next frame of video and that video frame must be scanned out to a display device. But in general parlance, video game lag refers to delays that are noticeable to a player. The tolerance for lag depends heavily on the type of game. For instance, a strategy gameStrategy game
A strategy game or strategic game is a game in which the players' uncoerced, and often autonomous decision-making skills have a high significance in determining the outcome...
or a turn-based game with a low pace may have a high threshold or even be mostly unaffected by high delays, whereas a twitch gameplay game such as a first-person shooter
First-person shooter
First-person shooter is a video game genre that centers the gameplay on gun and projectile weapon-based combat through first-person perspective; i.e., the player experiences the action through the eyes of a protagonist. Generally speaking, the first-person shooter shares common traits with other...
with a considerably higher pace may require significantly lower delay to be able to provide satisfying gameplay. But, the specific characteristic of the game matter. For example, fast chess is a turn-based game that is fast action and may not tolerate high lag. And, some twitch games can be designed such that only events that impact the outcome of the game introduce lag, allowing for fast local response most of the time.
Lag in online multiplayer gaming
All online video games such as World of WarcraftWorld of Warcraft
World of Warcraft is a massively multiplayer online role-playing game by Blizzard Entertainment. It is the fourth released game set in the fantasy Warcraft universe, which was first introduced by Warcraft: Orcs & Humans in 1994...
, Final Fantasy XI
Final Fantasy XI
, also known as Final Fantasy XI Online, is a MMORPG developed and published by Square as part of the Final Fantasy series. It was released in Japan on Sony's PlayStation 2 on May 16, 2002, and was released for Microsoft's Windows-based personal computers in November 2002...
, Call of Duty
Call of Duty
Call of Duty is a first-person shooter video game developed by Infinity Ward and published by Activision in 2003. It is the first game in a series with the same name. The game simulates the infantry and combined arms warfare of World War II. The game is based on the Quake III: Team Arena engine...
, Adventure Quest Worlds, RuneScape
RuneScape
RuneScape is a fantasy massively multiplayer online role-playing game released in January 2001 by Andrew and Paul Gower, and developed and published by Jagex Games Studio. It is a graphical browser game implemented on the client-side in Java, and incorporates 3D rendering...
, League of Legends
League of Legends
The BetFred League of Legends was a darts tournament featuring some of the legends of the game of darts which commenced in May 2008. The tournament is broadcast on Setanta Sports in the United Kingdom....
, Heroes of Newerth
Heroes of Newerth
Heroes of Newerth is a free-to-play science fantasy, action real-time strategy game developed by S2 Games for Microsoft Windows, Mac OS X and Linux. The game was heavily inspired by the Warcraft III: The Frozen Throne custom map, Defense of the Ancients and is S2 Games' first game title in the...
, etc. incur online lag
Lag (online gaming)
In online gaming, Lag is a term used to describe delays between the action of players and the reaction of the server . Although it is commonly used to refer to delays caused by high latency, it is occasionally used to describe delays caused by insufficient processing power in the client and/or server...
due to a combination of local and remote processing lag and communications latency, and user tolerance for lag depends highly upon the type of game, similarly as it does for local gaming. In general parlance, the round-trip network latency between a client game and the host server is referred to as the client's ping
Ping
Ping is a computer network administration utility used to test the reachability of a host on an Internet Protocol network and to measure the round-trip time for messages sent from the originating host to a destination computer...
time.
Lag in cloud gaming
Cloud gamingCloud gaming
Cloud gaming, also called gaming on demand, is a type of online gaming that allows direct and on-demand streaming of games onto a computer, similar to video on demand, through the use of a thin client, in which the actual game is stored on the operator's or game company's server and is streamed...
is a type of online gaming where the entire game is hosted on a game server in a data center, and the user is only running a thin client
Thin client
A thin client is a computer or a computer program which depends heavily on some other computer to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself...
locally that forwards game controller
Game controller
A game controller is a device used with games or entertainment systems used to control a playable character or object, or otherwise provide input in a computer game. A controller is typically connected to a game console or computer by means of a wire, cord or nowadays, by means of wireless connection...
actions upstream to the game server. The game server then renders the next frame of the game video which is compressed using low-lag video compression and is sent downstream and decompressed by the thin client. For the cloud gaming experience to be acceptable, the round-trip lag of all elements of the cloud gaming system (the thin client, the Internet and/or LAN connection the game server, the game execution on the game server, the video and audio compression and decompression, and the display of the video on a display device
Display device
A display device is an output device for presentation of information in visual or tactile form...
) must be low enough that the user perception is that the game is running locally. Because of such tight lag requirements, distance considerations of the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
through optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
come into play, currently limiting the distance between a user and a cloud gaming game server to approximately 1000 miles, according to OnLive
OnLive
OnLive is a cloud gaming platform: the games are synchronized, rendered, and stored on remote servers and delivered via the Internet.The service is available using the OnLive Game System, PCs running Microsoft Windows and Intel-based Macs with OS X 10.5.8 or later...
, the only company thus far operating a cloud gaming service.
Cloud gaming is a very new technology, but early tests have shown that in practice, cloud gaming lag is only slightly higher than local console lag. For example, Unreal Tournament 3 incurs up to 133ms of lag on a console and was tested in July 2010 as incurring 150ms in lag on OnLive
OnLive
OnLive is a cloud gaming platform: the games are synchronized, rendered, and stored on remote servers and delivered via the Internet.The service is available using the OnLive Game System, PCs running Microsoft Windows and Intel-based Macs with OS X 10.5.8 or later...
, resulting in the assessment in July 2010 that "Out of controlled conditions, OnLive has managed to get within spitting distance of console response times". In September 2010, reviewers reported a steady reduction in lag due to constant improvements in the technology, to the point where "the actions on screen were one-to-one with my input controls. In fact, I forgot that it wasn't running natively on my PC."