A spotlight on Latency

How much time it takes for a packet of data to get from one designated point to another.

Network related delays can be changed dramatically when a data centre is moved. Geographical distance contributes significantly to the network latency between the client and server. Just moving the server physically further away from the user can double the latency. However it won’t just slow down operations, it will also reduce the throughput of applications further impacting the end users. To put into context the relationship between network delay and an application response time is far from one-to-one.

The following example provides a relatively simple overview of the relationship between network latency and application latency. For a local user with one millisecond of network delay between the client and the server, 150 transactions would be completed in 0.15 seconds. When just 50 milliseconds of network delay is introduced (representing a typical cross-country WAN connection), the performance of these transactions did not slow down by only 50 milliseconds (0.05 seconds). Instead, the same 150 transactions took 7.5 seconds.


This illustrates how small changes in network latency result in major problems with application performance. In a complex project such as a data centre move, the challenge of assessing the network impact on application performance becomes one of large scale as hundreds of servers hosting thousands of applications need to be tested to understand the full impact of the data centre move.

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