DNS servers are grouped into several categories of specialization of servicing domain name system queries.
The two principal roles, which may be implemented either uniquely or combined in a given product are: Answer X is Akamai’s recursive DNS resolver (r DNS). Answer X is a modern resolver, supporting DNSSEC, IPv6, and full subscriber aware policy controls.
ANS is a commercial authoritative server from Nominum, a company whose chief scientist and chairman is Paul Mockapetris, the inventor of the DNS.Its first release was in April 2010, but ISC involvement concluded with the release of BIND 10 version 1.2 in April 2014.ISC cited a lack of resources to continue development of BIND 10, and they reaffirmed their commitment to BIND9.Knot DNS supports DNSSEC signing and among others hosts root zone (K and L Root_name_servers), several top-level domains.Mara DNS is a free software DNS server by Sam Trenholme that claims a good security history and ease of use. The same software can be configured to support authoritative, recursive and hybrid mode.
The BIND 10 codebase continues on as an open source project at (ibid.) It is not included in this comparison at this time.