http://www.rfc-editor.org/rfc/rfc2826.txt
RFC 2826: IAB Technical Comment on the Unique DNS Root, 2000-05-01T23:00:00-00:00This document discusses the existence of a globally unique public name space in the Internet called the DNS (Domain Name System). This name space is a hierarchical name space derived from a single, globally unique root. It is a technical constraint inherent in the design of the DNS. One root must be supported by a set of coordinated root servers administered by a unique naming authority. It is not technically feasible for there to be more than one root in the public DNS. This memo provides information for the Internet community.