This tests the performance / distance between vps data centers and the dns server's data centers. imho it's better to have a test web page that consumers visit and establishes a tcp connection to those dns services and estimate the rtt of a single packet from the time it took to establish the connection, or test via the https interface for services that support it.
While I whole-heartedly agree with your objection, I question the solution. How do you get high accuracy timing of DNS resolution in JavaScript inside the browser?
The challenge in providing a good dns service is more about having nodes closer to the user than the dns resolution step itself because that in theory is almost constant for cached responses (it's usually in the microseconds) and when it's not cached the response time is really dependent on recursive querying of other dns servers. So the dns resolution can me estimated by measuring it from a data center manually and subtracting the rtt and use that as a constant.
To estimate the rtt, you can do an xhr request and grab the connectStart and connectEnd using window.performance API keeping in mind it takes 3 rtt to do the handshake. Note that the request will fail for services that don't provide https support but that's ok because we just want to measure connect.
The reason cloudflare has a better performance is most likely because they have better coverage and not because their servers are faster. Faster servers are a small factor in the final response time.
For services that provide https support you can accurately measure the connect and response time of the XHR request using window.performance interface and subtract the dns resolution of the request. Also if you do the request twice, the second time is likely to have a dns and connect time = 0.
Not a JavaScript developer, but if they can do timings fine enough to run Meltdown attacks in JS, I think they can safely and accurately measure network timings.
Timing in general isn’t the issue here, there isn’t a way to my knowledge to get just the DNS portion (specifically across an arbitrary set of DNS providers) of the network timing in JS. Just like there isn’t a way to test the timing of a single packet really either.
See original context, it is clearly about evaluating DNS providers with real end users via a web app. Considering a majority of providers don’t support it, seems it’ll be a very limited evaluation if it followed your proposal.
You'd have to change your nameserver manually unfortunately.
But you could build a good webpage that actually measures how well your current nameserver performs over a wide variety of different types of lookups, both warm and cold caches etc.
