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.
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.
Joel Hasbrouck and Gideon Saar (2011) measure latency to execute financial transactions based on three components: the time it takes for information to reach the trader, execution of the trader's algorithms to analyze the information and decide a course of action, and the generated action to reach the exchange and get implemented.
[5] Trading using computers has developed to the point where millisecond improvements in network speeds offer a competitive advantage for financial institutions.
Ping uses the Internet Control Message Protocol (ICMP) echo request which causes the recipient to send the received packet as an immediate response, thus it provides a rough way of measuring round-trip delay time.
Ping cannot perform accurate measurements,[7] principally because ICMP is intended only for diagnostic or control purposes, and differs from real communication protocols such as TCP.
Queuing delay occurs when a gateway receives multiple packets from different sources heading toward the same destination.
The combination of propagation, serialization, queuing, and processing delays often produces a complex and variable network latency profile.
In shorter metro networks, higher latency can be experienced due to extra distance in building risers and cross-connects.
To calculate the latency of a connection, one has to know the distance traveled by the fiber, which is rarely a straight line, since it has to traverse geographic contours and obstacles, such as roads and railway tracks, as well as other rights-of-way.
Only a limited number of planes are able to make the transatlantic journey, so when one lands they must prepare it for the return trip as quickly as possible.
The reduced latency, then, is: The people involved in the turnaround are interested only in the time it takes for their individual tasks.
In the example above, the requirement to clean the plane before loading passengers results in a minimum latency longer than any single task.
For example, suppose a process commands that a computer card's voltage output be set high-low-high-low and so on at a rate of 1000 Hz.
The operating system schedules the process for each transition (high-low or low-high) based on a hardware clock such as the High Precision Event Timer.
Note that in software systems, benchmarking against "average" and "median" latency can be misleading because few outlier numbers can distort them.
A simulator should, therefore, reflect the real-world situation by ensuring that the motion latency is equal to or less than that of the visual system and not the other way round.