Why do speed tests show that my server is less than 1000mbps

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Edge100x
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Why do speed tests show that my server is less than 1000mbps

Post by Edge100x »

Customers ask this sometimes after they use an external speed-testing website to check the server's throughput.

Our VDSes come on mostly-unused gigE (1000mbps) connections, which means that they far outstrip the available capacity at speed-testing sites, which are sometimes overloaded and limited to much lower speeds. These sites are meant for testing fairly slow home broadband connections that are in the 10mbps range, and they are tweaked and configured with those in mind.

To give an example, you might connect from your VDS in Dallas to a speed site that has a shared 100mbps connection to the internet. The ISP running the test site allows 10 clients to run tests at once, since they realize that most broadband lines are less than that, and the few that are more will generally fit into the remainder (they also know that they could allocate more bandwidth, but bandwidth is expensive). When you connect, 9 other users might be running tests, leaving only 10mbps left out of their small link -- and making it look like your VDS can only handle 10mbps!

In reality, your server, being on a barely-used 1000mbps line, would completely dwarf even what they could test with nobody else connected (100mbps).

As another test of speed, you could download a large file from a nearby, known-fast download host, such as a close university with an underloaded FTP, or from a mirror of kernel.org. You will likely see bandwidth speeds in the 5-10 megabyte per second (40-80mbps) range if you do this. The reasons for the realized speed still being less than 1000mbps are twofold: One, you're probably still faster than their available capacity; and two, TCP connections across the internet are limited by what's called the "bandwidth delay product" and TCP Window size.

Regardless of what you see through these two testing methods, you can rest easy, because we're certain that we have access to the full capacity that we advertise. To test each of our connections to InterNAP and make sure that they can handle what InterNAP tells us they can, we frequently do large site-to-site transfers, and we also look at the bandwidth used during DDoS attacks. We have always found that InterNAP gives us the full amount that we pay for.

If you ever see packet loss on the first hop of your outbound trace -- which could indicate a capacity problem -- let us know ASAP.
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