Why

Reduce number of respdiff queries needed to test DNS software interoperability to a minimum while keeping maximum coverage.

How

Reduce the number of queries that will be sent to the same exact set of name servers.

Assuming large portions of queries are answered by the same set of name servers (e.g. by cloud providers), this should reduce the query set size significantly.

Steps:

1. query each domain for a set of its name servers
2. count the frequency of each name server set
3. filter the set of questions by skipping some of the queries whose domains are served by the same name servers