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Latency

The term latency is an expression for the period of time taken to send a data packet from a source to the intended destination, the higher the latency the slower the data transmission.  This incorporates all elements of the file sending process – including encoding, transmission, and decoding.

Certain delivery protocols such as FTP are particularly susceptible to latency.  When sending packets of data to the remote site the sending site waits for an acknowledgment that the packet has been received before sending the next one, thus making the problem extremely time consuming in the event of high latency.  In extreme cases of latency the time that it takes for the delivery of data and then listening out for the reply can result in the data throughput levels dropping to an significantly low level rendering the solution useless.

There are several ways to combat this one being to utilise a multi-threaded TCP protocols – working in the same manner as above just that many other packet transfer requests are made increasing the throughput.  Another increasingly popular route is to adopt a UDP based delivery protocol which adopts a send and forget mentality i.e. not waiting for the acknowledgement receipt.  This can significantly speed up the delivery process but other features are required, as UDP out of the box won’t work for everyone.

Network tools like ping tests and traceroute measure latency by determining the time it takes a given network packet to travel from source to destination and back, the so-called round-trip time. Round-trip time is not the only way to specify latency, but it is the most common.  To test the latency on your Internet connection between 100′s of test servers go to Speedtest.net where you can test your bandwidth and latency against a local (london) server against say one in Bangkok.

 

Speedtest.net Results

 

On DSL or cable Internet connections, latencies of less than 100 milliseconds (ms) are typical and less than 25 ms desired. Satellite Internet connections, on the other hand, average 500 ms or higher latency.

If you suffer from latency problems when it comes to file transfer, please contact Pro2col on 0333 123 1240 for more information on how you can combat this problem.

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