Netflix host their own speed test at https://fast.com
The system appears to work by using JavaScript to time the download of a 25MB file returned from http://api-global.netflix.com/oca/speedtest (which is a CNAME of api-global.geo.netflix.com). The JS code seems to do this 3 times and then compare the results.
That CNAME's DNS servers will return the estimated nearest server from a geographical list, based upon your IP address, such as the examples below:
| Europe | api-global.eu-west-1.prodaa.netflix.com |
| United States | api-global.us-east-1.prodaa.netflix.com |
All of the end points we discovered appear to be hosted on Amazon; for example, 34.253.86.250 is registered to Amazon Data Services Ireland Limited. It can therefore be a complicated process to determine exactly where any "slow" traffic is being experiences, either on the ISP network gateway or beyond (the responsibility of Netflix).
Testing using easily available tools common to most Windows PC users is obfuscated by Netflix not sharing any such tools with ISPs, and the ICMP protocol being fire-walled on Netflix's endpoints. However, a reasonably useful set of results can be obtained as follows:
Instructions to run the PathPing tool: Click the Windows start button any type powershell [press the Enter key] In the Windows PowerShell window type in pathping api-global.geo.netflix.com [press the Enter key] The pathping tool will run a series of tests over about 5 minutes, and then return some results. Right-click on the title-bar and choose Edit > Select All....followed by....Edit > Copy Paste the results to us in a Support Ticket so that we can analyse them; please record the exact DATE dd-MMM-yyy and TIME HH:mm of the test. |
Key to the results:
| Hop | The number of the router being tested; your device is "0" and your broadband router is likely to be "1". Each router sends your traffic onward to the next hop (router) until it reaches the destination. Once the traffic leaves your router (usually hop "2" and further) then it will be in the ISP network. It will then leave the ISP network and travel to the destination endpoint. |
| RTT | Round Trip Time. The number of milliseconds it took to ping an echo signal to that hop (router )and receive a reply. |
| Source to Here ("Pct" = percentage) | This measures the percentage of packets dropped between your device and this specific hop (node/router) |
| This Node/Link ("Pct" = percentage) | This measures the percentage of packets dropped between this specific hop (node/router) and the one before it. This is useful to identify routers that may be overloaded. It can help identify where such router are located, either on the ISP's network of outside of it. A vertical bar "|" helps pinpoint the route between the 2 routers where the measurement was taken. |
| Address | The host name (if discover-able); this helps identify where the node (router) is located and who is responsible for it. |
Example PathPing output showing possible overloaded router on ISP network:
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