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I just wanted to know What is the Meaning of latency in performance testing?

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In simplest terms this is Remote Response time. For instance, you want to invoke a web service or access a web page. Apart from the processing time that is needed on the server to process your request, there is a delay involved for your request to reach to server and the response from server to reach you.

While referring to Latency, it’s that delay we are talking about. This becomes a big issue for a remote data center which is hosting your service/page.

Imagine your data center in US, and accessing it from India. So there would definitely be some time lag for the request and response to complete. If ignored, latency can trigger your SLA’s. Though it’s quite difficult to improve latency it’s important to measure it

Quoted from this link .

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Latency is the time from just sending the request until the first byte of response is received, it is also known as Time to First Byte, it includes:

  • Opening socket connection
  • Sending packet to the target server
  • Waiting for the first byte of response

So it is one of the essential performance metrics for the web sites which covers the time from opening the connection till the response starts coming. High latency indicates networking problems.

References:

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In performance testing, term latency of a request is travel time from client to server and server to client. Some tester called it “Delay”. Let’s say:

A request starts at t=0
Reaches to a server in 1 second (at t=1)
Server takes 2 seconds to process (at t=3)
Reaches to the client end in 1 second (at t=4)

So Latency will be 2 seconds.

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I beg to differ the answers above. Latency in performance testing is what you, or the entity asking for the test, have decided it means. The Wikipedia article is a good starting point

The answers above somewhat apply in the context of web testing using one of the more common tools and should be called network latency.

In reality it may or may not include higher then layer 4 processing times, or something totally different if it's a non networked system.

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