The whois protocol retrieves information about domain names from a central registry. The whois service is provided by the organizations that run the Internet. Whois is often used to retrieve registration information about an Internet domain or server. It can tell you who owns the domain, how their technical contact can be reached, along with other information.
The original Whois function was to be a central directory of resources and people on ARPANET. However, it could not adequately meet the needs of the expanded Internet. RWhois extends and enhances the Whois concept in a hierarchical and scaleable fashion. In accordance with this, RWhois focuses primarily on the distribution of "network objects", or 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.
The RWhois defines both a directory access protocol and a directory architecture. As a directory service, RWhois is a distributed database, where data is split across multiple servers to keep database sizes manageable.
On the Internet, two such types of data are widely used: domain names and IP networks. Domain names are organized via a label-dot system, reading from a more specific label to a more general label left to right; IP networks are also lexically hierarchical labels using the Classless Inter-Domain Routing (CIDR) notation, but their hierarchy is not easily determined with simple text manipulation. Instead, an IP network"s hierarchy is determined by converting the network to binary notation and applying successively shorter bit masks.
RWhois directs clients toward the appropriate authority area by generating referrals. Referrals are pointers to other servers that are presumed to be closer to the desired data. The client uses this referral to contact the next server and ask the same question. The next server may respond with data, an error, or another referral (or referrals). By following this chain of referrals, the client will eventually reach the server with the appropriate authority area.
Protocol Structure
The entire RWhois protocol can be defined as a series of directives, responses, queries, and results.
rwhois-protocol = client-sends / server-returns
client-sends = *(directives / rwhois-query)
server-returns = *(responses / rwhois-query-result)
Related Terms: SMTP, FTP, Finger, DNS
Sponsor Source: Whois and RWhois are defined by IETF (http://www.ietf.org)
Reference:
http://www.javvin.com/protocol/rfc954.pdf: Nicname/Whois
http://www.javvin.com/protocol/rfc2167.pdf: Referral Whois (RWhois) Protocol V1.5