Latency

Latency refers to the delay before a transfer of data begins following an instruction for its transfer. In computing, latency is often used to mean any delay or waiting that increases real or perceived response time beyond the response time desired.

Overview

Latency is physically a consequence of the limited velocity with which any physical interaction can propagate. This velocity is always lower than or equal to the speed of light. Therefore, every physical system with any physical separation (distance) between interacting systems will experience some sort of latency, regardless of the nature of stimulation that it has been exposed to.

The precise definition of latency depends on the system being observed and the nature of stimulation. In communications, the lower limit of latency is determined by the medium being used for communications. In reliable two-way communication systems, latency limits the maximum rate that information can be transmitted, as there is often a limit on the amount of information that is "in-flight" at any one moment. In the field of human–machine interaction, perceptible latency has a strong effect on user satisfaction and usability.

Types of Latency

There are several specific types of latency:

• Transmission Latency: The time taken for a packet to be transmitted across a network.
• Propagation Latency: The delay in transmitting a packet between two points. This is dependent on the speed of light and the distance between the points.
• Processing Latency: The delay in processing data at an intermediate node.
• Queuing Latency: The delay caused by data packets queuing.
• Coding Latency: The delay due to data being coded for transmission.

Latency in Computing

In computing, latency is the time it takes for data from one point to reach another. This is usually measured in milliseconds and can be seen when downloading or uploading data, or when playing online games. High latency can cause lag. This can be due to a slow network, congestion, or heavy data processing.

Latency in Telecommunications

In telecommunications, latency is the time it takes for a voice packet to reach the receiver. This can be affected by the distance the packet has to travel, the number of nodes it has to pass through, and the speed of the network. High latency can cause delays in communication and can affect the quality of voice calls.

Latency in Medicine

In medicine, latency refers to the time period between when an individual is infected with a virus or bacteria and when they start showing symptoms of the disease. This period can vary greatly depending on the type of disease and the individual's immune system.

See Also

• Delay (audio effect)
• Lag (online gaming)
• Ping (networking utility)
• Round-trip delay time
• Throughput

References

Latency Resources
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