The RFC also discusses the hierarchical database model, resource record usage, query formation, query resolution, and domain control. This RFC specifies the format of domain system transactions, discusses the implementation of domain servers, and explores the use of domain names in the context of mail and other network software. Several implementations of the domain system exist. These implementations are available online. The last paragraphs list implementations under development.
Points of contact can supply more information.
The intent of listing these implementations is to give vendors the opportunity to inspect working code. These implementations embody experience with the domain system and offer interpretations of the protocols found acceptable in operational environments. A commercial version of BIND is distributed with Sun Microsystems' operating system version 3.2. The point of contact is Bill Nowicki. They already have a resolver that depends on recursive queries.