RWhois stands for Referral Whois. It is an application layer protocol.

RWhois is a Directory Services protocol which extends and enhances the Whois concept in a hierarchical and scalable fashion. It focuses on the distribution of "network objects" -- the data representing Internet resources or people -- and uses the inherently hierarchical nature of these network objects (domain names, Internet Protocol (IP) networks, email addresses) to more accurately discover the requested information.