Draft of new Executive Intro

Chris Weider <weider@ans.net> Mon, 02 March 1992 18:24 UTC

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Date: Mon, 2 Mar 1992 13:17:24 -0500
From: Chris Weider <weider@ans.net>
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To: disi
Subject: Draft of new Executive Intro

INTERNET-DRAFT                                                 C. Weider
                                                             J. Reynolds
                                                           February 1992

              Executive Introduction to Directory Services
                        Using the X.500 Protocol

Status of this Memo

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


   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).


   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.


   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 Network Information Center, or
   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 Big Names 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
   propogated, 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 would be
   very hard pressed, if not completely unable, to provide non-text
   services, such as photos and sound.


   X.500 is a CCITT protocol which is designed to build a distributed,
   global directory. It offers the following features:

   * Decentralized Maintenance:
   Each site running X.500 is responsible ONLY for its local part of the
   Directory, so updates and maintenance can be done instantly.

   * Powerful Searching Capabilities:
   X.500 provides powerful searching facilities that allow users to
   construct arbitrarily complex queries.

   * Single Global Namespace:
   Much like the DNS, X.500 provides a single homogeneous namespace to
   users. The X.500 namespace is more flexible and expandable than the

   * Structured Information Framework:
   X.500 defines the information framework used in the Directory, allowing
   local extentions.

   * Standards-Based Directory Services:
   As X.500 can be used to build a standards-based directory,
   applications which require directory information (e-mail, automated
   resources locators, special-purpose directory tools) can access a
   planet's worth of information in a uniform manner, no matter where
   they are based or currently running.

   With these features alone, X.500 is being used today to provide the
   backbone of a global White Pages service. There is almost 3 years of
   operational experience with X.500, and it is being used widely in Europe and
   Australia in addition to North America. In addition, the various X.500
   implementations add some other features, such as photographs in G3-FAX
   format, and color photos in JPEG format. However, as X.500 is standards
   based, there are very few incompatabilities between the various versions
   of X.500, and as the namespace is consistent, the information in the
   Directory can be accessed by any implementation. Also, work is being done
   in providing Yellow Pages services and other information resource location
   tasks in the Directory.

   The X.500 Directory is taking us closer to the day when we will indeed
   have the entire world on our desktops, and X.500 will help insure that
   we can find whom and what we need.


   For a more detailed technical introduction to X.500 and an extensive
   bibliography, see "Technical Overview of Directory Services Using the
   X.500 Protocol", by Weider, Reynolds, and Heker. This is available
   from the NIC as FYI ##, RFC 13##. For a catalogue of X.500
   implementations, see "A Catalog of Available X.500 Implementations",
   ed. Lang and Wright.  This is available from the NIC as FYI 11, RFC


   Security issues are not discussed in this paper.


   Chris Weider
   Advanced Network and Services, Inc.
   2901 Hubbard, G-1
   Ann Arbor, MI 48105-2437

   Phone (313) 663-2482
   E-mail: weider@ans.net

   Joyce K. Reynolds
   Information Sciences Institute
   University of Southern California
   4676 Admirality Way
   Marina del Rey, CA 90292

   Phone: (310) 622-1511
   E-Mail: jkrey@isi.edu