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RFC 2167

Informational
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Referral Whois (RWhois) Protocol V1.5

Part 1 of 2, p. 1 to 26
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Obsoletes:    1714


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Network Working Group                                      S. Williamson
Request for Comments: 2167                                    M. Kosters
Obsoletes: RFC 1714                                            D. Blacka
Category: Informational                                         J. Singh
                                                             K. Zeilstra
                                                 Network Solutions, Inc.
                                                               June 1997

                 Referral Whois (RWhois) Protocol V1.5

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   This memo describes Version 1.5 of the client/server interaction of
   RWhois.  RWhois provides a distributed system for the discovery,
   retrieval, and maintenance of directory information. This system is
   primarily hierarchical by design. It allows for the deterministic
   routing of a query based on hierarchical tags, referring the user
   closer to the maintainer of the information. While RWhois can be
   considered a generic directory services protocol, it distinguishes
   itself from other protocols by providing an integrated, hierarchical
   architecture and query routing mechanism.

1. Introduction

   Early in the development of the ARPANET, the SRI-NIC established a
   centralized Whois database that provided host and network information
   about the systems connected to the network and the electronic mail
   (email) addresses of the users on those systems [RFC 954]. The
   ARPANET experiment evolved into a global network, the Internet, with
   countless people and hundreds of thousands of end systems. The sheer
   size and effort needed to maintain a centralized database
   necessitates an alternate, decentralized approach to storing and
   retrieving this information.

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   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.

   RWhois synthesizes concepts from other, established Internet
   protocols. The RWhois protocol and architecture derive a great deal
   of structure from the Domain Name System (DNS) [RFC 1034] and borrow
   directory service concepts from other directory service efforts,
   primarily [X.500]. The protocol is also influenced by earlier
   established Internet protocols, such as the Simple Mail Transport
   Protocol (SMTP) [RFC 821].

   This RWhois specification defines both a directory access protocol
   and a directory architecture. The directory access protocol
   specifically describes the syntax of the client/server interaction.
   It describes how an RWhois client can search for data on an RWhois
   server, or how the client can modify data on the server. It also
   describes how the server is to interpret input from the client, and
   how the client should interpret the results returned by the server.
   The architecture portion of this document describes the conceptual
   framework behind the RWhois protocol. It details the concepts upon
   which the protocol is based and describes its structural elements.
   The protocol implements the architecture.

   This document uses language like SHOULD and SHALL that have special
   meaning as specified in "Key words for use in RFCs to Indicate
   Requirement Levels". [RFC2119]

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2. Architecture

2.1 Overview

   As a directory service, RWhois is a distributed database, where data
   is split across multiple servers to keep database sizes manageable.
   The architecture portion of this document details the concepts upon
   which the protocol is based and describes its structural elements.
   Specifically, the architecture is concerned with how the data is
   split across the different servers. The basis of this splitting is
   the lexically hierarchical label (or tag), which is a text string
   whose position in a hierarchy can be determined from the structure of
   the string itself.

   All data can follow some sort of hierarchy, even if the hierarchy
   seems somewhat arbitrary. For example, person names can be arranged
   into hierarchical groups via geography. If all the people in
   particular towns are grouped into town groups, then all of the town
   groups can be grouped into state (or province) groups, and then all
   of the state groups can be grouped into a country group. Then, a
   particular name would belong in a town group, a state group, and a
   country group. However, just given a name, it would be impossible to
   determine where in the hierarchy it belongs.  Therefore, a person
   name is not lexically hierarchical.

   However, there are certain types of data whose position in the
   hierarchy can be determined by deciphering the data itself, for
   example, phone numbers. A phone number is grouped according to
   country code, area code, local exchange, and local extension. By
   looking at a phone number, it is possible to determine to which of
   all these groups the number belongs:  1-303-555-2367 is in country
   code 1, area code 303, local exchange 555, and has a local extension
   of 2367. Therefore, a phone number is lexically hierarchical.

   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; for example, war.west.netsol.com is a part of west.netsol.com,
   which is a part of netsol.com, which is a part of com. 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; for example, 198.41.0.0/22
   is a part of 198.41.0.0/16, which is a part of 198.40.0.0/15.
   Instead, an IP network's hierarchy is determined by converting the
   network to binary notation and applying successively shorter bit
   masks.

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   It is important to note that, while very little real data is
   lexically hierarchical in nature, people often create label systems
   (or namespaces) to help manage the data and provide an element of
   uniqueness, for example, Social Security Numbers, ISBNs, or the Dewey
   Decimal System. RWhois leverages lexically hierarchical labels,
   domain names and IP networks, for its data splitting using the
   concepts of authority areas and referrals. An authority area is
   associated with an RWhois server and a lexically hierarchical label,
   which is considered to be its name. An authority area is a piece of
   the distributed database that speaks with authority about its
   assigned part of the hierarchy. All data associated with a particular
   lexically hierarchical tag should be located within that authority
   area's database. Authority areas are further explained in Section
   2.4.

   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. In
   the RWhois architecture, referrals are generated by identifying a
   lexically hierarchical label and deciphering the label to determine
   the next server. Referrals are further explained in Section 2.5.

   When a number of RWhois servers containing authority areas are
   brought on line and informed about each other, they form an RWhois
   tree. The tree has a root authority area, which is the group that
   contains all other groups.  The root authority area must keep
   pointers to the servers and authority areas that form the first level
   of the hierarchy. The authority areas in the first level of the
   hierarchy are then responsible for keeping pointers to the authority
   areas below them and for keeping a pointer to the root.

2.2 Design Philosophy

   The design goals for the RWhois protocol are as follows.

      * It should be a directory access protocol. The server should be
        able to access and update the data residing on it.
      * It should facilitate query routing. An unresolved query should
        be redirected to a server that is presumed to be closer to the
        desired data.
      * It should enable data replication. The server should be able to
        duplicate its data on another server.
      * The server should be lightweight and delegate more functions to
        the client.

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   The concepts used to achieve these design goals are explained in the
   remaining document.

2.3 Schema Model

   As a directory service, RWhois uses various database schema to store
   and represent data. Schema, in this document, has two definitions.
   First, it refers to the entire structure of a database, all the
   tables and fields forming a complete database. When schema is used in
   this context, it is called the "database schema". Database schema
   consists of attributes, classes, and objects. Schema may also refer
   to a single piece of the database, a single table with fields. When
   schema is used in this context, it is just called "schema" or it is
   preceded by the name of the particular piece: contact schema or
   domain schema, for example. In this usage, schema is equivalent to
   "class", defined below.

   There is no standard database schema in the RWhois architecture. Each
   authority area is presumed to be able to define its own local schema.
   However, an authority area that is part of a larger RWhois tree is
   expected to have some part of its schema pertain to the lexically
   hierarchical label upon which the RWhois tree is based. An authority
   area schema may not change throughout much of an RWhois tree.

2.3.1 Attributes

   An attribute is a named field and is the smallest typed unit in the
   database schema. It is equivalent to a relational database's field.
   An attribute is not considered to be data by itself; it is simply
   used to give data a type. When a piece of data has been typed by an
   attribute, it is typically referred to as a value and is represented
   as an attribute-value pair. The RWhois syntax for the attribute-value
   pair is to separate them with a colon, for example:

   First-Name:Bill

   Attributes have a number of properties, some mandated by the RWhois
   protocol and some that are implementation dependent. These properties
   are usually a reflection of the database system used by the server.
   The following is a list of the protocol-mandated properties and their
   descriptions.

    Attribute    This is the name of the attribute.

    Description  This is a natural language description of the
                 attribute.

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    Type         This is a parameter that broadly indicates the use
                 of the attribute to the protocol. There are three
                 standard types:  TEXT, ID, and SEE-ALSO. The default is
                 TEXT, which indicates that the value is a text string.
                 ID indicates that the attribute contains the ID of
                 another RWhois object. This type of attribute is used
                 for database normalization.  SEE-ALSO indicates that
                 the attribute contains a pointer (a Uniform Resource
                 Identifier (URI)) to some other kind of external data;
                 for example, a World Wide Web page or FTP site.

    Format       This is an interpretable string that describes the
                 acceptance format of the value. The server (and
                 optionally the client) should match the value to the
                 format string to determine if the value is acceptable.
                 The format of this property is a keyword indicating the
                 syntax of the format string, followed by a colon,
                 followed by the format string itself. Currently, the
                 only keyword recognized is "re" for POSIX.2 extended
                 regular expressions.

    Indexed      This is a true or false flag indicating that this
                 attribute should be indexed (and therefore able to be
                 searched).

    Required     This is a true or false flag indicating that this
                 attribute must have a value in an instance of the
                 class.

    Multi-Line   This is a true or false flag indicating that this
                 attribute may have multiple instances in a class, but
                 all of the instances are to be considered as multiple
                 lines of the same attribute instance. This allows
                 normal line terminators to terminate values.

    Repeatable   This is a true or false flag indicating that there may
                 be multiple instances of this attribute in a class and
                 each instance is to be interpreted as a separate
                 instance (in contrast to Multi-Line). This flag is
                 mutually exclusive with Multi-Line: if Multi-Line is
                 true, then Repeatable must be false and vice versa.

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    Primary      This is a true or false flag that indicates that this
                 attribute is a primary key. If more than one attribute
                 in a class is marked as primary, then these attributes
                 together form a single primary key. The primary key is
                 intended to be used to force uniqueness among class
                 instances. Therefore, there can be only one instance of
                 a primary key in a database. The Primary flag implies
                 that the attribute is also required.

    Hierarchical This is a true or false flag that indicates that this
                 attribute is lexically hierarchical.

    Private      This is a true or false flag that indicates whether or
                 not this attribute is private (that is, publicly not
                 viewable).  It defaults to false. If it is true, then
                 only the clients that satisfy the
                 authentication/encryption requirements of a guardian
                 (described below) are able to view the attribute-value
                 pair.

2.3.2 Class

   A class is a collection of attributes; it is a structure, not data.
   The concept is equivalent to that of a relational database table. It
   is also equivalent to the second definition of schema, above.

   A class also has some properties that are sometimes referred to as
   its "meta" information. These properties are listed below.

    Version     This is a time/date stamp that is used to quickly detect
                when a class definition has been changed.

    Description This is a natural language description of the class.

2.3.3 Object

   An object is an instance of a class. It is data with a type of
   <class>.

2.3.4 Base Class

   While RWhois does not have or advocate using a specific, standardized
   schema, it does impose a few requirements. It requires that all
   defined classes inherit attributes from a particular base class (or
   base schema).  The RWhois specification does not require the actual
   implementation of inheritance. Instead, all classes must include the
   attributes defined in the base class.

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   The base class has the following attributes.

    Class-Name    This attribute contains the name of the class to which
                  the object belongs. It is the type of the object
                  itself. It is of type TEXT and is required.

    Auth-Area     This attribute contains the name of the authority area
                  to which the object belongs. It, along with Class-
                  Name, definitively defines the type of the object. It
                  is of type TEXT and is required.

    ID            This attribute is a universal identifier for the
                  object. It is formed by choosing a string that is
                  unique within an authority area and appending the
                  authority area to it, separating the local string from
                  the authority area name with a period. The only
                  restrictions on the local string are that it must be
                  unique within the authority area and not contain the
                  period character. This attribute is hierarchical in
                  nature. It is always generated by the server (for
                  example, during a register operation). It is of type
                  TEXT and is required.

    Updated       This attribute is a time/date stamp that indicates the
                  time of last modification of the object. It is both
                  informational and a form of record locking. It
                  prevents two clients from modifying the same object at
                  the same time. It is of type TEXT and is required.

    Guardian      This attribute is a link to a guardian object
                  (described below). Its value is the ID of a guardian
                  object. It is of type ID and is optional. It is
                  repeatable, since an object may have multiple
                  guardians.

    Private      This attribute is a true or false flag that indicates
                  whether or not an object is private (that is, publicly
                  not viewable). It defaults to false. If it is true,
                  then only the clients that satisfy the
                  authentication/encryption requirements of one of the
                  object's guardians are able to view the object. If the
                  object is publicly viewable, then the Private
                  attribute property of each of its attributes still
                  applies.

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    TTL           This attribute is the "time-to-live" of a given
                  object. It is included only if an object has a
                  different time-to-live than the default given in the
                  Start of Authority information. Its value is specified
                  in seconds. It is of type TEXT and is optional.

   The RWhois specification defines two standard classes that should be
   included in all implementations: the referral and guardian classes.

2.3.5 Referral Class

   The referral class is defined to hold referral information (typically
   for link referrals). It consists of attributes defined as part of the
   base class, the protocol-specific attributes described below, and any
   installation-specific attributes.

    Referred-Auth-Area This attribute contains the name of the authority
                       area to which the referral points. It is used as
                       a search key during the query routing. It is of
                       type TEXT and is required. It is repeatable,
                       since referrals can point to servers hosting more
                       than one authority area.

    Referral           This attribute contains the referral itself. It
                       is an RWhois URL. It is of type TEXT and is
                       required. It is repeatable, since more than one
                       server can host a Referred-Auth-Area.

2.3.6 Guardian Class

   The guardian class is defined to hold security information. The
   fundamental concept behind the guardian class is that an object (or
   another structure) is "guarded" by containing a pointer to a guardian
   object [Guardian]. To modify, delete, or possibly view the guarded
   object, the authentication (or encryption, or both) scheme must be
   satisfied. Guardians are intended to not have rank: if an object is
   guarded by more than one guardian object, satisfying any one of those
   guardians is sufficient. A guardian object that does not have any
   Guardian attribute linking it to other guardians guards itself. That
   is, the authentication scheme in the guardian object itself must be
   satisfied to modify, delete, or possibly view it.

   Guardian objects are typically linked to actual database objects with
   the Guardian attribute found in the base class. However, a guardian
   may also be linked to an entire authority area, in which case the
   guardian becomes implicitly linked to all of the objects contained
   within the authority area.

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   The guardian class consists of the base class, the protocol-specific
   attributes described below, and any installation-specific attributes.

    Guard-Scheme This attribute contains a keyword indicating the
                 authentication methodology. Its value must be
                 understood by both the client and server, and its value
                 dictates the contents of the Guard-Info attribute. It
                 is of type TEXT and is required.

    Guard-Info   This attribute contains that data that is used by the
                 Guard-Scheme to verify the authentication. Its actual
                 format is dictated by the Guard-Scheme, for example, it
                 could contain a password or Pretty Good Privacy (PGP)
                 public key id [RFC 1991]. For security reasons, it
                 should not be displayed, and its Private attribute
                 property should be set to true. It is of type TEXT and
                 is required.

2.4 Authority Areas

   The concept of authority areas is pivotal to the RWhois architecture.
   When an RWhois tree is created for a particular lexically
   hierarchical namespace, the different pieces of the hierarchy are
   mapped to authority areas. The most important concept behind an
   authority area is the ability for a portion of the RWhois tree to
   definitively control that portion of the hierarchy. This means that
   an authority area is able to state whether or not a hierarchical tag
   is in the whole RWhois tree. It does this either by returning the
   object containing this tag, returning a referral to a sub-authority
   area, or returning a response indicating that no objects were found.

   This structure enables efficient routing of queries based on the
   hierarchical label to the piece of the hierarchy responsible for it.
   For example, in the domain name namespace as served by RWhois, the
   root of the tree would be an authority area named ".", which would
   delegate a "us" sub-authority area, which would delegate "va", "co",
   "md", and "ca" authority areas, and so forth. When the server with
   the "va.us" authority area is asked about "loudoun.va.us", it will be
   able to authoritatively state that either no "loudoun.va.us" exists
   or it will provide an object for or a referral to "loudoun.va.us".
   Further, if the server is asked about "howard.md.us", it cannot
   answer authoritatively, so it must provide a referral to its
   hierarchical parent ("us" or the root).

   This use of authority area strongly indicates where data should be
   stored within an RWhois tree. Because RWhois uses a specific query
   routing model, data needs to be placed under the proper authority
   area. It is certainly possible to place a piece of data under the

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   wrong authority area, for example, putting an object for
   "howard.md.us" under the "va.us" authority area. In such cases, the
   data is considered to be misplaced and unable to be found within the
   RWhois tree. However, while data should be placed under the lowest
   (most specific) authority area, it is also possible that it could be
   placed in a higher (least specific) authority area, for example,
   putting an object for "loudoun.va.us" under the "us" authority. This
   may be acceptable since, in most cases, the data would be able to be
   found.

   In addition to controlling a part of an RWhois hierarchy, an
   authority area is considered to be autonomous. Each authority area is
   treated as a separate database by the protocol. However, it is
   recommended that an authority area share some core schema with the
   rest of the RWhois tree for interoperability reasons. Each authority
   area, however, is not bound by the database schema of its
   hierarchical parent or by any of its sub-authority areas.

2.5 Query Routing

   RWhois is not only a directory access protocol but it can also route
   queries. Routing a query involves redirecting the query to another
   server that is presumed to be closer to the desired data. To route a
   query, the server first determines the location of the next server.
   It then either forwards the query to that server and returns the
   result to the client or returns the location of that server to the
   client. The location of the server must contain its host name (or IP
   address), port number, and authority area.

   The location of the server to which a query is routed is called a
   referral.  There are two types of referrals: punt and link referrals.
   A punt referral is a pointer to a server that is further up an RWhois
   tree, and a link referral is a pointer to a server that is further
   down the tree. For example, in Figure 1, when the server for the
   "va.us" authority area routes a query up to the server for the "us"
   authority area, it generates a punt referral. Alternatively, when it
   routes a query down to the server for the "loudon.va.us" authority
   area, it generates a link referral.

   Query routing depends on whether or not the search value in a query
   is lexically hierarchical. If the search value is hierarchical, the
   server can generate punt or link referrals using the association of
   authority areas with lexically hierarchical labels. Otherwise, the
   server may send the query to a special index server that gathers the
   indexing information for both hierarchical and non-hierarchical data
   from the directory servers and returns referrals to these servers
   [CIP]. If the server receives one or more referrals from the index
   server, it should return them to the client.

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   It is important to note that the server may route a query whether it
   could resolve the query or not. Even if a query has been resolved
   locally, the server may also return referrals to the client by
   sending the query to the index server. For example, if the server for
   the "com" authority area receives the "domain Org-Name=IBM" query, it
   may return all the domain objects for IBM within the "com" authority
   area. In addition, it may also return referrals to the server for the
   "nl" authority area if that server contains domain objects for IBM in
   the Netherlands and has fed the corresponding indexing information to
   the index server. This way the client can get back information for
   both "ibm.com" and "ibm.nl" domains.

2.5.1 Query Routing Rules

   An RWhois server routes a query based on certain rules. The objective
   is to determine the location of a server to which to route the query.
   A query may contain one or more query terms. The query routing rules
   are applied on each query term until a referral is found. The rules
   are listed below.

      * Is the search value in the query term hierarchical? If not, go
        to the next query term.
      * Parse the hierarchical portion of the search value. Is it is
        within one of the authority areas? If not, go to the next query
        term.
      * Does the found authority area have any referral objects
        (instances of the referral class)? If not, return the "230 No
        objects found" error to the client.
      * Is the hierarchical portion of the search value within the
        Referred-Auth-Area attribute of one of the referral objects? If
        it is, return the value of the Referral attribute of the found
        referral object as a link referral to the client.
      * Are the search values of some of the query terms hierarchical
        but not within any of the authority areas? If they are, return a
        punt referral to the client.
      * Are the search values of all the query terms non-hierarchical?
        If they are, send the query to a special index server that
        gathers the indexing information for both hierarchical and non-
        hierarchical data from the directory servers and returns
        referrals to these servers. If the server receives one or more
        referrals from the index server, return them to the client.

   Note that there can be more than one referral returned to the client.
   These referrals may point to servers serving different authority
   areas. The client may follow them in any order.

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   The pseudo code for the above rules is:

   for each query term in the query
    if the search value in the query term is hierarchical
     if the search value is within one of the authority areas
       if the search value is within one of the referred authority areas
        the server sends link referral(s)
       else
        the server sends a "230 No objects found" error
       endif
     endif
    endif
   endfor

   if the search values of some of the query terms are hierarchical but
     not within any of the authority areas
    the server sends Punt referral(s)
   endif

   if the search values of all the query terms are non-hierarchical
    the server sends Referral(s) from an index server
   endif

2.6 Data Replication

   An RWhois server can replicate (duplicate) data from another RWhois
   server on a per-authority area basis. Data replication makes the
   RWhois service more reliable. Further, it increases throughput by
   distributing queries to more than one server.

   There can be two types of servers serving an authority area: a master
   server and a slave server. A master server is where data is
   registered for an authority area. It answers authoritatively to
   queries in that authority area. There must be one and only one master
   server for an authority area. A master server is also called a
   primary server.

   A slave server is where data is replicated from the master server for
   an authority area. It also answers authoritatively to queries in that
   authority area. There may be one or more slave servers for an
   authority area. A slave server is also called a secondary server.
   Note that a slave server must not register data for an authority
   area.

   It is recommended that the master and slave servers for an authority
   area be geographically separate. Therefore, network unreachability at
   one site will not completely shut down the RWhois service for that
   authority area.

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2.6.1 Data to Replicate

   In RWhois, data is replicated on a per-authority area basis. The
   smallest type of data a slave server can replicate is an attribute of
   a class.  Therefore, a slave server can replicate data for all the
   classes, some classes, or some attributes of some classes.

   The amount of data a slave server can replicate each time is either
   all of the data or the data that has changed since the last
   replication. The process of replicating all of the data is called
   complete replication. The process of replicating the data that has
   changed since the last replication is called incremental replication.

2.6.2 Start Of Authority Variables

   Each authority area has some administrative variables, defined at the
   master server, to control data replication. These variables are
   called the Start Of Authority (SOA) variables. They are listed below.

    Serial-Number     This is the serial number of the data in an
                      authority area. The master server should update
                      this variable whenever the data in the authority
                      area is changed. Its value is a time/date stamp.

    Refresh-Interval  This is the time interval before a slave server
                      checks for complete replication. Its value is
                      specified in seconds.

    Increment-IntervalThis is the time interval before a slave server
                      checks for incremental replication. Its value is
                      specified in seconds.

    Retry-Interval    This is the time interval before a slave server
                      tries again to connect to a master server that
                      appears to be out-of-service. Its value is
                      specified in seconds.

    Time-To-Live      This is the default time to live for the data in
                      an authority area at a slave server. The slave
                      server should not answer authoritatively to
                      queries for such stale data. Its value is
                      specified in seconds.

    Admin-Contact     This is the email address of an individual or a
                      role account responsible for the data integrity in
                      an authority area at the master server.

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    Tech-Contact      This is the email address of an individual or a
                      role account responsible for the operation of the
                      master server for an authority area.

    Hostmaster        This is the email address of an individual or a
                      role account to whom email messages to update the
                      data in an authority area at the master server are
                      sent.

    Primary-Server    This is the location of the master server for an
                      authority area. Its value must contain both the
                      host name (or IP address) and port number of the
                      master server.

3. Protocol

3.1 Overview

   The above sections describe the directory service architecture based
   on the RWhois protocol. The remaining sections describe the syntax of
   the protocol; the sequence and syntax of the information exchanged
   between a server and a client. There are five types of information
   that may be exchanged during a client/server session: directive,
   response, query, result, and info.

3.1.1 Directive

   A directive is a command that a client sends to a server to set a
   control parameter for the session, get the meta-information (class
   definitions and SOA information) about an authority area, or get the
   data in an authority area. The first character of a directive must be
   a "-". The server must support the "-rwhois" directive; all other
   directives are optional. The server must indicate in the banner which
   directives are implemented (see Section 3.1.9).

3.1.2 Response

   A response is the information that a server returns to a client for a
   directive. It is comprised of one or more lines, and the last line
   always indicates the success or failure of the directive. The first
   character of each response line must be a "%". If a server runs a
   directive successfully, the last response line must be "%ok".
   Otherwise, it must be "%error <error-code> <error-text>". A line with
   the string "%ok" or "%error" in the first position must occur only
   once in a server response and must always be the last line. The
   server may send the "%info" response for special messages.

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   A client must understand the "%ok", "%error", and "%info" responses.
   The client must also understand directive specific responses, if it
   uses the related directives to communicate with the server. For
   example, if the client sends the "-schema" directive to the server,
   the client must understand the "%schema" response.

3.1.3 Query

   A query is a command that a client sends to a server to access the
   data in an authority area. The first character of a query must not be
   a "-", since the server checks the first character of each command
   from a client to determine whether it is a directive or a query.

3.1.4 Result

   A result is the information that a server returns to a client for a
   query.  It can be either the accessed data or referrals to other
   servers. It is comprised of one or more lines, and the last line
   always indicates the success or failure of the query. If a server
   returns either data or referrals for a query, the last result line
   must be "%ok". Otherwise, it must be "%error <error-code> <error-
   text>".

3.1.5 Info

   An info message contains miscellaneous information that a server
   sends to a client. The server may use it to send special messages,
   for example a "message of the day" (MOTD), to the client. The first
   info line must be "%info on", and the last info line must be "%info
   off".

3.1.6 Client/Server Session

   A typical RWhois client/server session has the following sequence of
   messages.

      * The client connects to the server.
      * The server returns a banner identifying its protocol versions
        and capabilities.
      * The client sends one or more directives to the server.
      * The server returns the response to each directive.
      * The client finally sends a query to the server.
      * The server returns the query results.
      * The server closes the connection, unless the client has directed
        it not to close the connection.

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3.1.7 Examples

   This section gives some common examples of the client/server
   interaction.  The notation in the examples uses a prefix to indicate
   from where the information comes. A "C" indicates that the client
   sends the data to the server. An "S" indicates that the server sends
   the data to the client. The line is a comment when "#" is used. The
   space after the prefix is not part of the data.

   The following example illustrates a successful query.

   # The client connects to the server.
   # The server returns a banner identifying its protocol versions and
   # capabilities.
   S %rwhois V-1.5:00ffff:00 master.rwhois.net (Network Solutions V-1.5)
   # The client sends a directive to limit the number of search hits
   # to 20.
   C -limit 20
   # The server returns a successful response.
   S %ok
   # The client sends a query to search for rwhois.net domain.
   C domain rwhois.net
   # The server returns the data for rwhois.net domain.
   S domain:ID:dom-1.rwhois.net
   S domain:Auth-Area:rwhois.net
   S domain:Class-Name:domain
   S domain:Updated:19970107201111000
   S domain:Domain:rwhois.net
   S domain:Server;I:hst-1.rwhois.net
   S domain:Server;I:hst-2.rwhois.net
   S
   S %ok
   # The server closes the connection.

   The following example illustrates the link and punt referrals.

   # The client connects to the server.
   # The server returns a banner identifying its protocol versions and
   # capabilities.
   S %rwhois V-1.5:00ffff:00 master.rwhois.net (Network Solutions V-1.5)
   # The client sends a directive to hold the connection until it sends
   # a directive to close the connection.
   C -holdconnect on
   # The server returns a successful response.
   S %ok
   # The client sends a query to search for a.b.rwhois.net domain.
   C domain a.b.rwhois.net
   # The server returns a link referral to a server serving the

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   # b.rwhois.net authority area.
   S %referral rwhois://master.b.rwhois.net:4321/auth-area=b.rwhois.net
   S %ok
   # The client sends a query to search for internic.net domain.
   C domain internic.net
   # The server returns a punt referral to a server serving the root
   # authority area.
   S %referral rwhois://rs.internic.net:4321/auth-area=.
   S %ok
   # The client sends a directive to close the connection.
   C -quit
   S %ok
   # The server closes the connection.

   The following example illustrates a query error.

   # The client connects to the server.
   # The server returns a banner identifying its protocol versions and
   # capabilities.
   S %rwhois V-1.5:00ffff:00 master.rwhois.net (Network Solutions V-1.5)
   # The client sends a query to search for c.rwhois.net domain.
   C domain c.rwhois.net
   # The server returns an error, since neither data nor referrals for
   # c.rwhois.net domain are found within the rwhois.net authority area.
   S %error 230 No objects found
   # The server closes the connection.

3.1.8 Notation

   The following sections use the Augmented Backus-Naur Form (ABNF)
   notation to describe the syntax of the protocol. For further
   information, see Section 2 of [RFC822]. The notation in the examples
   uses a prefix to indicate from where the information comes. A "C"
   indicates that the client sends the data to the server. An "S"
   indicates that the server sends the data to the client. The line is a
   comment when "#" is used. The space after the prefix is not part of
   the data.

3.1.9 General ABNF definitions

   Lexical Tokens

   alpha = "a".."z" / "A".."Z"
   digit = "0".."9"
   hex-digit = digit / "a".."f" / "A".. "F"
   id-char = alpha / digit / "_" / "-"
   any-char = <ASCII 1..255,
              except LF (linefeed) and CR (carriage return)>

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   dns-char = alpha / digit / "-"
   email-char = <see [RFC 822]>
   space = " "
   tab = <ASCII TAB (tab)>
   lf = <ASCII LF (linefeed)>
   cr = <ASCII CR (carriage return)>
   crlf = cr lf

   Grammar

   year = 4digit
   month = 2digit
   day = 2digit
   hour = 2digit
   minute = 2digit
   second = 2digit
   milli-second = 3digit
   host-name = dns-char *(dns-char / ".")
   ip-address = 1*3digit "." 1*3digit "." 1*3digit "." 1*3digit
   email = 1*email-char "@" host-name
   authority-area = (dns-char / ".") *(dns-char / "." / "/")
   object-id = 1*id-char "." authority-area
   host-port = (host-name / ip-address) ":" 1*5digit
   class-name = 1*id-char
   attribute-name = 1*id-char
   attribute-value = 1*any-char
   time-stamp = year month day hour minute second milli-second
   on-off = "on" / "off"

   Note that the time-stamp must be in the Greenwich Mean Time (GMT)
   time zone.  Also note that since in the above any-char is 1..255
   ASCII that the RWhois protocol is an 8 bit protocol.

   Response

   The general response for every directive and query is either "%ok" or
   "%error". In addition, a "%info" response may be sent.

   response = ok-response crlf / error-response crlf / info-response
   ok-response = "%ok"
   error-response = "%error" space error-code space error-text
   error-code = 3digit
   error-text = 1*any-char
   info-response = "%info" space "on" crlf *(*any-char crlf) "%info"
           space "off" crlf

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   Banner

   The server must send a banner to the client when the connection is
   opened.  The banner contains the version(s) of the protocol the
   server supports and a capability ID of encoded bit flags that
   indicates which directives are implemented. If the server supports
   more than one version of the protocol, the lowest-numbered version
   must be specified first. The bits in extra-id are reserved for future
   use. The end of the banner should contain a free-form string
   indicating the name of the server implementation. A server must
   support at least one version of the protocol, and may accept more
   versions for compatibility reasons.

   rwhois-banner = "%rwhois" space version-list space host-name
         [space implementation] crlf
   version-list = version *("," version)
   version = version-number [":" capability-id]
           / "V-1.5" ":" capability-id
   version-number = "V-" 1*digit "." 1*digit
   capability-id = response-id ":" extra-id
   response-id = 6hex-digit
   extra-id = 2hex-digit
   implementation = 1*any-char

   Protocol

   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)

3.2 Required Directives

   The server must implement the following directives.

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3.2.1 rwhois

   Description

   The "-rwhois" directive may be issued by the client at the start of
   every session . It tells the server which version of the protocol the
   client can handle. The server must respond with a banner containing
   the protocol version and directives it implements. This banner is the
   same banner that is sent by the server when the connection is opened,
   except that the server must indicate only one version number. The
   banner issued when opening a connection may contain more than one
   version number. The directive flags are encoded into three octets,
   which are described in Appendix D.

   ABNF

   rwhois-dir = "-rwhois" space version-number [space implementation]
                crlf
   rwhois-response = "%rwhois" space version space host-name
           [space implementation] crlf

   Errors

   300 Not compatible with version
   338 Invalid directive syntax

   Examples

   # When a connection is opened, the server issues the banner.
   S %rwhois V-1.0,V-1.5:00ffff:00 rs.internic.net (NSI Server 1.5.4)
   # The client sends the rwhois directive.
   C -rwhois V-1.5 NSI Client 1.2.3
   S %rwhois V-1.5:00ffff:00 rs.internic.net (NSI Server 1.5.4)
   S %ok

3.3 Optional Directives

   The server should implement the following directives.

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3.3.1 class

   Description

   The "-class" directive can be used by the client to get the meta-
   information for one or more classes in an authority area. The
   response must contain the description and version number of each
   specified class and may be expanded in the future with additional
   attributes. When no class name is given, the server must return the
   meta-information for all the classes in the authority area. Every
   class record must end with an empty "%class" line.

   ABNF

   class-dir = "-class" space authority-area *(space class-name) crlf
   class-response = *class-record response
   class-record = *class-line "%class" crlf
   class-line = "%class" space class-name ":" "description" ":"
                1*any-char crlf
      / "%class" space class-name ":" "version" ":" time-stamp crlf
      / "%class" space class-name ":" meta-field ":" meta-value crlf
   meta-field = 1*id-char
   meta-value = 1*any-char

   The following fields are required.

    meta-field   meta-value  Description

    description  1*any-char  Class description.
                           Time/date stamp indicating version of class,

    version      time-stamp  must be updated after class definition is
                             changed.

   Errors

   338 Invalid directive syntax
   340 Invalid authority area
   341 Invalid class
   400 Directive not available
   401 Not authorized for directive

   Examples

   C -class rwhois.net domain host
   S %class domain:description:Domain information
   S %class domain:version:19970103101232000
   S %class

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   S %class host:description:Host information
   S %class host:version:19970214213241000
   S %class
   S %ok

3.3.2 directive

   Description

   The "-directive" directive can be used by the client to get
   information about the directives that the server supports. The
   response must contain the name and description of each specified
   directive and may be expanded in the future with additional
   attributes. When no directive name is given, the server must return
   information about all the directives. Every directive record must end
   with an empty "%directive" line.

   ABNF

   directive-dir = "-directive" *(space directive-name) crlf
   directive-name = 1*id-char
   directive-response = *directive-record response
   directive-record = "%directive" space "directive" ":" directive-name
                      crlf *directive-line "%directive" crlf
   directive-line = "%directive" space "description" ":" 1*any-char crlf
           / "%directive" space attribute-name ":" attribute-value crlf

   Errors

   338 Invalid directive syntax
   400 Directive not available
   401 Not authorized for directive

   Examples

   Without parameters:

   C -directive
   S %directive directive:rwhois
   S %directive description:RWhois directive
   S %directive
   S %directive directive:quit
   S %directive description:Quit connection
   S %directive
   S %ok

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   With parameters:

   C -directive quit
   S %directive directive:quit
   S %directive description:Quit connection
   S %directive
   S %ok

3.3.3 display

   Description

   By default, the server uses the dump format for the output of a query
   result. The output format can be changed with the "-display"
   directive.  When no parameter is given, the server must list all the
   display formats it supports. Every display record must end with an
   empty "%display" line.

   Currently, only the dump format is standard and must be supported by
   the server. Other output formats may be added in the future. See
   Section 3.4 for the definition of the dump format.

   ABNF

   display-dir = "-display" crlf
       / "-display" space display-name crlf
   display-name = 1*id-char
   display-response = *(display-record) response
   display-record = "%display" space "name" ":" display-name crlf
   *display-line "%display" crlf
   display-line = "%display" space attribute-name ":"
                  attribute-value crlf

   Errors

   338 Invalid directive syntax
   400 Directive not available
   401 Not authorized for directive
   436 Invalid display format

   Examples

   # Get the available display formats.
   C -display
   S %display name:dump
   S %display
   S %ok

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   # Change the active display format.
   C -display dump
   S %ok

3.3.4 forward

   Description

   The "-forward" directive instructs the server to follow all the
   referrals and return the results to the client. This directive can be
   used to run an RWhois server as a proxy server. The default value
   must be "off". When the value is set to "on", the server must not
   return referrals.

   ABNF

   forward-dir = "-forward" space on-off crlf
   forward-response = response

   Errors

   338 Invalid directive syntax
   400 Directive not available
   401 Not authorized for directive

   Examples

   C -forward on
   S %ok

   C -forward off
   S %ok

3.3.5 holdconnect

   Description

   Normally, the server closes the connection after each query. This
   behavior is controlled by the holdconnect state, which can be changed
   with the "-holdconnect" directive. When the holdconnect state is set
   to "off", the server must close the connection after a query; when it
   is set to "on", the server must not close the connection after a
   query. By default, the holdconnect state must be set to "off" for
   each connection.

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   ABNF

   holdconnect-dir = "-holdconnect" space on-off crlf
   holdconnect-response = response

   Errors

   338 Invalid directive syntax
   400 Directive not available
   401 Not authorized for directive

   Examples

   C -holdconnect on
   S %ok

   C -holdconnect off
   S %ok

3.3.6 limit

   Description

   When returning a query result, the server should limit the number of
   objects returned to the client. The "-limit" directive changes this
   limit.  The default and maximum limit is server-dependent. The client
   can get the current limit by using the "-status" directive (see
   Section 3.3.13).

   ABNF

   limit-dir = "-limit" space 1*digit crlf
   limit-response = response

   Errors

   331 Invalid limit
   338 Invalid directive syntax
   400 Directive not available
   401 Not authorized for directive

   Examples

   C -limit 100
   S %ok


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