To know the performance of your operator's DNS servers or of external services such as those of Google or Cloudflare you can use Namebench, you will know minimum, maximum and average response times, thus being able to choose the best DNS service for your connection.
For a guide on how to use Namebench: fribby.net/namebench/?lang=en
Namebench Official Site: code.google.com/archive/p/namebench /
Free Download Namebench for Windows and Mac:
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