rfc2167.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

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.