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Concept
Latency (engineering)
Summary
Latency, from a general point of view, is a time delay between the cause and the effect of some physical change in the system being observed. Lag, as it is known in gaming circles, refers to the latency between the input to a simulation and the visual or auditory response, often occurring because of network delay in online games.
Latency is physically a consequence of the limited velocity at which any physical interaction can propagate. The magnitude of this velocity is always less than or equal to the speed of light. Therefore, every physical system with any physical separation (distance) between cause and effect will experience some sort of latency, regardless of the nature of the stimulation to which it has been exposed.
The precise definition of latency depends on the system being observed or the nature of the simulation. In communications, the lower limit of latency is determined by the medium being used to transfer information. In reliable two-way communication systems, latency limits the maximum rate at which information can be transmitted, as there is often a limit on the amount of information that is in-flight at any given moment. Perceptible latency has a strong effect on user satisfaction and usability in the field of human–machine interaction.
Online games are sensitive to latency (lag), since fast response times to new events occurring during a game session are rewarded while slow response times may carry penalties. Due to a delay in transmission of game events, a player with a high latency internet connection may show slow responses in spite of appropriate reaction time. This gives players with low-latency connections a technical advantage.
Minimizing latency is of interest in the capital markets, particularly where automated systems for financial transactions and information are used to process market updates and turn around orders within milliseconds. Low-latency trading occurs on the networks used by financial institutions to connect to stock exchanges and electronic communication networks (ECNs) to execute financial transactions.
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Ontological neighbourhood
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Network throughput (or just throughput, when in context) refers to the rate of message delivery over a communication channel, such as Ethernet or packet radio, in a communication network. The data that these messages contain may be delivered over physical or logical links, or through network nodes. Throughput is usually measured in bits per second (bit/s or bps), and sometimes in data packets per second (p/s or pps) or data packets per time slot. The system throughput or aggregate throughput is the sum of the data rates that are delivered to all terminals in a network.
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