Content Delivery Network (CDN) Test Suite
CDNs are widely used by large websites to distribute static content near to end users. This reduces the burden on the content providers' servers and improves web page load times. Major, well-known CDNs include Akamai, Google and Microsoft. There are a great many smaller CDNs in operation, too.
The largest CDN operators will place caches inside ISP (internet service provider) networks so that traffic does not even need to leave the ISP network. This is beneficial for both the ISPs (it reduces the load on their transit and peering links) and the CDN operators (it spreads the content-serving burden to a wider array of servers).
Our CDN test suite measures performance to multiple CDNs by fetching a small object (usually around 80 kibibytes, or KiB) over HTTP. Care is taken to ensure that we fetch the same object, or a very similar one in size and content, from each CDN, to provide comparability between the CDNs themselves.
Supported CDNs
The CDNs we currently support for testing are:
Google
Amazon AWS/Cloudfront
Microsoft Azure
Cloudflare
Akamai
Apple
Alibaba
Tencent
Fastly
Limelight
Metrics
The key metrics we capture by the test are:
DNS lookup time.
TCP connection time.
Download speed.
Note: the download speed is not representative of the maximum capacity of the user's broadband connection. An 80 KiB transfer is not enough to ramp the line up to full speed. It is instead intended to be indicative of the transfer rate seen for a small object as served by the CDN in question.
Object fetch time (lower is better).
The IP address of the CDN node.
CDN Test Example
We tested CDN latency under otherwise idle conditions. Many applications are served over a small number of CDNs. Not all CDNs have distribution endpoints in every country; this can affect the latency to applications hosted overseas.
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