Executive Introduction to Directory Services Using the X.500 Protocol
RFC 1308

Document Type RFC - Informational (March 1992; No errata)
Also known as FYI 13
Last updated 2013-03-02
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Network Working Group                                          C. Weider
Request for Comments: 1308                                           ANS
FYI: 13                                                      J. Reynolds
                                                                     ISI
                                                              March 1992

              Executive Introduction to Directory Services
                        Using the X.500 Protocol

Status of this Memo

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

Abstract

   This document is an Executive Introduction to Directory Services
   using the X.500 protocol. It briefly discusses the deficiencies in
   currently deployed Internet Directory Services, and then illustrates
   the solutions provided by X.500.

   This FYI RFC is a product of the Directory Information Services
   (pilot) Infrastructure Working Group (DISI).  A combined effort of
   the User Services and the OSI Integration Areas of the Internet
   Engineering Task Force (IETF).

1. INTRODUCTION

   The Internet is growing at a phenomenal rate, with no deceleration in
   sight.  Every month thousands of new users are added. New networks
   are added literally almost every day. In fact, it is entirely
   conceivable that in the future every human with access to a computer
   will be able to interact with every other over the Internet and her
   sister networks. However, the ability to interact with everyone is
   only useful if one can locate the people with whom they need to work.
   Thus, as the Internet grows, one of the limitations imposed on the
   effective use of the network will be determined by the quality and
   coverage of Directory Services available.

   Directory Services in this paper refers not only to the types of
   services provided by the telephone companies' White Pages, but to
   resource location, Yellow Pages services, mail address lookup, etc.
   We will take a brief look at the services available today, and at the
   problems they have, and then we will show how the X.500 standard
   solves those problems.

DISI Working Group                                              [Page 1]
RFC 1308                Executive Intro to X.500              March 1992

2. CURRENT SERVICES AND THEIR LIMITATIONS

   In the interests of brevity, we will only look at the WHOIS service,
   and at the DNS. Each will illustrate a particular philosophy, if you
   will, of Directory Services.

   The WHOIS service is maintained by the Defense Data Network Network
   Information Center, or DDN NIC.  It is currently maintained at GSI
   for the IP portion of the Internet. It contains information about IP
   networks, IP network managers, a scattering of well-known personages
   in the Internet, and a large amount of information related
   specifically to the MILNET systems. As the NIC is responsible for
   assigning new networks out of the pool of IP addresses, it is very
   easily able to collect this information when a new network is
   registered. However, the WHOIS database is big enough and
   comprehensive enough to exhibit many of the flaws of a large
   centralized database. First, centralized location of the WHOIS
   database causes slow response during times of peak querying activity,
   storage limitations, and also causes the entire service to be
   unavailable if the link to GSI is broken. Second, centralized
   administration of the database, where any changes to the database
   have to be mailed off to GSI for human transcription into the
   database, increases the turnaround time before the changes are
   propagated, and also introduces another source of potential error in
   the accuracy of the information. These particular problems affect to
   different degrees any system which attempts to provide Directory
   Services through a centralized database.

   The Domain Name Service, or DNS, contains information about the
   mapping of host and domain names, such as, "home.ans.net", to IP
   addresses. This is done so that humans can use easily remembered
   names for machines rather than strings of numbers. It is maintained
   in a distributed fashion, with each DNS server providing nameservice
   for a limited number of domains.  Also, secondary nameservers can be
   identified for each domain, so that one unreachable network will not
   necessarily cut off nameservice. However, even though the DNS is
   superlative at providing these services, there are some problems when
   we attempt to provide other Directory Services in the DNS. First, the
   DNS has very limited search capabilities. Second, the DNS supports
   only a small number of data types. Adding new data types, such as
   photographs, would involve very extensive implementation changes.

3. THE X.500 SOLUTION

   X.500 is a CCITT protocol which is designed to build a distributed,
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