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the exchange and get implemented. Hasbrouck and Saar contrast this with the way in which latencies are measured by many trading venues that use much more narrow definitions, such as the processing delay measured from the entry of the order (at the vendor's computer) to the transmission of an acknowledgment (from the vendor's computer). Trading using computers has developed to the point where millisecond improvements in network speeds offer a competitive advantage for financial institutions.
36:
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of change of perspective or displacement of objects such as the horizon, which takes some time to build up to discernible amounts after the initial acceleration which caused the displacement. 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.
573:, the execution of the process can be postponed if other processes are also executing. In addition, the operating system can schedule when to perform the action that the process is commanding. 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
462:. The latency of his trip is the time it takes him to go from his house in England to the hotel he is staying at in New York. This is independent of the throughput of the London-New York air link – whether there were 100 passengers a day making the trip or 10000, the latency of the trip would remain the same.
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may result. This is because, in the real world, motion cues are those of acceleration and are quickly transmitted to the brain, typically in less than 50 milliseconds; this is followed some milliseconds later by a perception of change in the visual scene. The visual scene change is essentially one
518:
The people involved in the turnaround are interested only in the time it takes for their individual tasks. When all of the tasks are done at the same time, however, it is possible to reduce the latency to the length of the longest task. If some steps have prerequisites, it becomes more difficult to
446:
within a system of workflows can be subject to some type of operational latency. It may even be the case that an individual system may have more than one type of latency, depending on the type of participant or goal-seeking behavior. This is best illustrated by the following two examples involving
354:
of most fiber optic cables is about 1.5, meaning that light travels about 1.5 times as fast in a vacuum as it does in the cable. This works out to about 5.0 ÎĽs of latency for every kilometer. In shorter metro networks, higher latency can be experienced due to extra distance in building risers
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are far enough away from Earth that communication latency becomes significant – about a quarter of a second for a trip from one ground-based transmitter to the satellite and back to another ground-based transmitter; close to half a second for two-way communication from one Earth station to another
226:
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
465:
From the point of view of flight operations personnel, latency can be entirely different. Consider the staff at the London and New York airports. 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
304:
However, in a non-trivial network, a typical packet will be forwarded over multiple links and gateways, each of which will not begin to forward the packet until it has been completely received. In such a network, the minimal latency is the sum of the transmission delay of each link, plus the
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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, principally because ICMP is intended only for diagnostic or control purposes, and differs from real
433:
Video latency refers to the degree of delay between the time a transfer of a video stream is requested and the actual time that transfer begins. Networks that exhibit relatively small delays are known as low-latency networks, while their counterparts are known as high-latency networks.
214:), 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
355:
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.
260:(the one-way latency from the source to the destination plus the one-way latency from the destination back to the source). Round-trip latency is more often quoted, because it can be measured from a single point. Many software platforms provide a service called
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occurs when a gateway receives multiple packets from different sources heading toward the same destination. Since typically only one packet can be transmitted at a time, some of the packets must queue for transmission, incurring additional delay.
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can also cause increased latency that is an order of magnitude or more. The combination of propagation, serialization, queuing, and processing delays often produces a complex and variable network latency profile.
168:. 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.
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In simulators with both visual and motion systems, it is particularly important that the latency of the motion system not be greater than of the visual system, or symptoms of
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perform all steps in parallel. In the example above, the requirement to clean the plane before loading passengers results in a minimum latency longer than any single task.
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However, cleaning, refueling and loading the cargo can be done at the same time. Passengers can only be loaded after cleaning is complete. The reduced latency, then, is:
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Audio latency is the delay between when an audio signal enters and when it emerges from a system. Potential contributors to latency in an audio system include
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in the sense of the extra time delay of a system over and above the reaction time of the vehicle being simulated, but this requires detailed knowledge of the
581:. The latency is the delay between the events generated by the hardware clock and the actual transitions of voltage from high to low or low to high.
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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
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is sometimes used to cut this delay, at the expense of more complicated satellite tracking on the ground and requiring more satellites in the
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626:, between initial input and output clearly discernible to the simulator trainee or simulator subject. Latency is sometimes also called
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have performance limitations that create additional latency. The problem may be mitigated with real-time extensions and patches such as
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Due to imperfections in the fiber, light degrades as it is transmitted through it. For distances of greater than 100 kilometers,
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606:, benchmarking against "average" and "median" latency can be misleading because few outlier numbers can distort them. Instead,
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153:, refers to the latency between the input to a simulation and the visual or auditory response, often occurring because of
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policies to different protocols. For more accurate measurements it is better to use specific software, for example:
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forwarding latency of each gateway. In practice, minimal latency also includes queuing and processing delays.
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The precise definition of latency depends on the system being observed or the nature of the simulation. In
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From the point of view of a passenger, latency can be described as follows. Suppose John Doe flies from
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for the data encoded on a platter to rotate from its current position to a position under the
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the process for each transition (high-low or low-high) based on a hardware clock such as the
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630:. Some authorities distinguish between latency and transport delay by using the term
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On embedded systems, the real-time execution of instructions is often supported by a
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are deployed. Latency introduced by these components needs to be taken into account.
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Foundations of Data
Intensive Applications Large Scale Data Analytics Under the Hood
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can propagate. The magnitude of this velocity is always less than or equal to the
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are incurred while a gateway determines what to do with a newly received packet.
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In simulation applications, latency refers to the time delay, often measured in
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256:(the time from the source sending a packet to the destination receiving it), or
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for the actuator arm to be positioned above the appropriate track and then
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921:"Coordinating Multiple Agents for Workflow-Oriented Process Orchestration"
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443:
218:. This gives players with low-latency connections a technical advantage.
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Latency is physically a consequence of the limited velocity at which any
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863:"Basic QoS part 1 – Traffic Policing and Shaping on Cisco IOS Router"
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at any given moment. Perceptible latency has a strong effect on
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provides an example of mechanical latency. Here, it is the time
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in reliable two-way communication systems as described by the
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that can be used to measure round-trip latency. Ping uses the
29:
137:, from a general point of view, is a time delay between the
841:"Network Protocols Discussion / Traffic Shaping Strategies"
790:"High-frequency trading: when milliseconds mean millions"
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Any mechanical process encounters limitations modeled by
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Assuming the above are done consecutively, minimum plane
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Information
Systems and E-Business Management Journal
60:. Unsourced material may be challenged and removed.
175:, the lower limit of latency is determined by the
346:. This would equate to a latency of 3.33
27:Time interval between an input and a response
8:
949:Simulating network link latency under Linux
350:for every kilometer of path length. The
120:Learn how and when to remove this message
707:
466:possible. It might take, for example:
179:being used to transfer information. In
551:Computer hardware and software systems
7:
58:adding citations to reliable sources
25:
930:. Springer-Verlag. Archived from
476:10 minutes to load the passengers
266:Internet Control Message Protocol
273:communication protocols such as
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756:Hasbrouck, Joel; Saar, Gideon.
387:to ensure continuous coverage.
141:of some physical change in the
45:needs additional citations for
736:"Velocity and the Bottom Line"
614:should use "99th percentile".
252:network is measured as either
1:
342:is largely a function of the
185:information that is in-flight
479:30 minutes to load the cargo
473:15 minutes to refuel a plane
419:digital-to-analog conversion
403:analog-to-digital conversion
379:and then back to the first.
763:. p. 1. Archived from
470:35 minutes to clean a plane
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691:Response time (technology)
638:and can be controversial.
597:real-time operating system
579:High Precision Event Timer
554:
394:
283:internet service providers
234:
210:are sensitive to latency (
69:"Latency" engineering
586:desktop operating systems
411:digital signal processing
197:human–machine interaction
545:disk read-and-write head
231:Packet-switched networks
686:Performance engineering
385:satellite constellation
328:bandwidth-delay product
237:Bandwidth-delay product
370:Satellite transmission
285:might apply different
758:"Low-Latency Trading"
724:Retrieved 2020-10-27.
571:computer multitasking
569:. In the context of
555:Further information:
322:Latency limits total
258:round-trip delay time
964:Engineering concepts
814:"Don't misuse ping!"
565:in the context of a
491:35 + 15 + 10 + 30 =
376:geostationary orbits
162:physical interaction
149:, as it is known in
139:cause and the effect
54:improve this article
869:. 19 September 2012
839:Shane Chen (2005).
770:on 11 November 2011
612:software developers
608:software architects
531:. The behavior of
352:index of refraction
820:on 12 October 2017
720:2021-04-22 at the
656:Age of Information
643:simulator sickness
541:rotational latency
511:Minimum latency =
919:(December 2003).
666:Interrupt latency
529:Newtonian physics
415:transmission time
312:Processing delays
189:user satisfaction
157:in online games.
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917:M. Brian Blake
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43:This article
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932:the original
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818:the original
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765:the original
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739:. Retrieved
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624:milliseconds
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563:instructions
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364:regenerators
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334:Fiber optics
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52:Please help
47:verification
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741:23 February
618:Simulations
557:Access time
533:disk drives
338:Latency in
316:Bufferbloat
18:Low-latency
799:2018-03-25
702:References
590:PREEMPT RT
449:air travel
360:amplifiers
324:throughput
235:See also:
110:April 2011
80:newspapers
715:"Latency"
676:Lead time
575:schedules
537:seek time
523:Mechanics
407:buffering
193:usability
958:Category
891:. 2021.
873:29 April
824:29 April
718:Archived
661:Feedback
650:See also
460:New York
444:workflow
438:Workflow
425:in air.
421:and the
181:reliable
774:18 July
632:latency
567:process
295:Netperf
279:routers
268:(ICMP)
254:one-way
135:Latency
94:scholar
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671:Jitter
456:London
177:medium
143:system
96:
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935:(PDF)
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584:Many
429:Video
391:Audio
299:Iperf
291:hping
248:in a
101:JSTOR
87:books
893:ISBN
875:2015
826:2015
776:2011
743:2023
610:and
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281:and
262:ping
239:and
73:news
458:to
362:or
297:or
275:TCP
212:lag
147:Lag
56:by
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