Network Working Group B. Jennings
Request for Comments: 1943 Sandia National Laboratory
Category: Informational May 1996
Building an X.500 Directory Service in the US
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 document provides definition and recommends considerations that
must be undertaken to operate a X.500 Directory Service in the United
States. This project is the work performed for the Integrated
Directory Services Working Group within the Internet Engineering Task
Force, for establishing an electronic White Pages Directory Service
within an organization in the US and for connecting it to a wide-area
Directory infrastructure.
Establishing a successful White Pages Directory Service within an
organization requires a collaborative effort between the technical,
legal and data management components of an organization. It also
helps if there is a strong commitment from the higher management to
participate in a wide-area Directory Service.
The recommendations presented in the document are the result of
experience from participating in the Internet White Pages project.
Table of Contents
1.0 Introduction 2
1.1 Purpose of this Document 2
1.2 Introduction to Directory Services 2
2.0 The X.500 Protocol 4
2.1 Introduction 4
2.2 Directory Model 4
2.3 Information Model 5
2.4 Benefits and Uses for X.500 Directory Service 6
2.5 Other Applications of X.500 7
3.0 Legal Issues 8
3.1 Introduction 8
3.2 Purpose of the Directory 8
3.3 User Rights 9
3.4 Data Integrity 9
Jennings Informational [Page 1]
RFC 1943 Building an X.500 Directory Service in the US May 1996
3.5 Protection of the Data 10
3.6 Conclusions 10
4.0 Infrastructure 11
4.1 Introduction 11
4.2 A Well Maintained Infrastructure 11
4.3 DUA Interfaces for End Users 12
5.0 Datamanagement & Pilot Projects 13
5.1 Simple Internet White Pages Service 13
5.2 InterNIC 13
5.3 ESnet 14
6.0 Recommendations 14
6.1 General 14
6.2 Getting Started 14
6.3 Who are the Customers 14
6.4 What are the Contents of the Directory 15
6.5 What are the Rights of the Individuals 15
6.6 Data Integrity 16
6.7 Data Security 16
6.8 Data Administration 17
6.9 Conclusion 17
7.0 References 18
8.0 Glossary 19
9.0 Security Considerations 22
10.0 Author's Address 22
1.0 Introduction
1.1 Purpose of this Document
This document provides an introduction for individuals planning to
build a directory service for an organization in the US. It presents
an introduction to the technical, legal, and organizational aspects
of a directory service. It describes various options to organizations
who want to operate an X.500 Directory service and illustrates these
with examples of current X.500 service providers.
1.2 Introduction to Directory Services
An electronic directory server is an electronic process that provides
a list of information provided via electronic access. This
information is variable in content, however it should be explicitly
defined by the directory purpose. Information about people,
organizations, services, network hardware are just a few examples of
data content that a directory service can provide. The aim of an
X.500 Directory service is to make using the directory intuitive and
as easy to use as calling for directory assistance. The X.500
Directory service is an international standard ratified by the
International organization for Standardization (IS) and the ITU-T
Jennings Informational [Page 2]
RFC 1943 Building an X.500 Directory Service in the US May 1996
International Telecommunication Union formerly (CCITT) in 1988 [1].
The Directory is intended to be global service comprised of
independently operated and distributed Directory Service Agents
(DSAs), that provide information in the form of a White Pages Phone
Directory.
Electronic mail communication benefits from the existence of a global
electronic White Pages to allow network users to retrieve addressing
information in an intuitive fashion. Manual searching for names and
addresses, specifically electronic addresses, can take a great deal
of time. A White Pages directory service can enable network users to
retrieve the addresses of communication partners in a user friendly
way, using known variables such as common name, surname, and
organization to facilitate various levels of searches.
In order to make global communication over computer networks work
efficiently, a global electronic White Pages service is
indispensable. Such a directory service could also contain telephone
and fax numbers, postal addresses as well as platform type to
facilitate in translation of documents between users on different
systems. An electronic White Pages may prove to be useful for
specific local purposes; replacing paper directories or improving
quality of personnel administration for example. An electronic
directory is much easier to produce and more timely than paper
directories which are often out of date as soon as they are printed.
The Internet White Pages Project provides many companies in the US
with an opportunity to pilot X.500 in their organizations.
Operating as a globally distributed directory service, this project
allows organizations in a wide variety of industry type to make
themselves known on the Internet and to provide access to their staff
as desired.
Some organizations, such as ESnet agreed to manage directory
information for other organizations. ESnet maintains data at their
site for all the national laboratories. They provide assistance to
organizations in defining their directory information tree (DIT)
structure. They also provide free access to the X.500 Directory via
Gopher, WWW, DUAs, whois and finger protocols.
The InterNIC is another directory services provider on the Internet.
To date [June 1995] they hold X.500 directory data for 52
organizations and provide free access to this data via various
protocols: X.500 DUA, E-Mail, whois, Gopher and WWW.
To find the most current listing of X.500 providers see RFC 1632 -
Catalog of Available X.500 Implementations [2].
Jennings Informational [Page 3]
RFC 1943 Building an X.500 Directory Service in the US May 1996
2.0 The X.500 Protocol
2.1 Introduction
This chapter provides the basic technical information necessary for
an organization to begin deploying an X.500 Directory Service. It
provides a brief introduction to the X.500 protocol and the
possibilities that X.500 offers.
2.2 The Directory Model
X.500 Directory Model is a distributed collection of independent
systems which cooperate to provide a logical data base of information
to provide a global Directory Service. Directory information about a
particular organization is maintained locally in a Directory System
Agent (DSA). This information is structured within specified
standards. Adherence to these standards makes the distributed model
possible. It is possible for one organization to keep information
about other organizations, and it is possible for an organization to
operate independently from the global model as a stand alone system.
DSAs that operate within the global model have the ability to
exchange information with other DSAs by means of the X.500 protocol.
DSAs that are interconnected form the Directory Information Tree
(DIT). The DIT is a virtual hierarchical data structure. An X.500
pilot using QUIPU software introduced the concept of a "root" DSA
which represents the world; below which "countries" are defined.
Defined under the countries are "organizations". The organizations
further define "organizational units" and/ or "people". This DIT
identifies the DIT for the White Pages X.500 services.
Each DSA provides information for the global directory. Directories
are able to locate in the hierarchical structure discussed above,
which DSA holds a certain portion of the directory. Each directory
manages information through a defined set of attributes and in a
structure defined as the Directory Information Base (DIB).
A DSA is accessed by means of a Directory User Agent (DUA). A DUA
interacts with the Directory by communicating with one or more DSAs
as necessary to respond to a specific query. DUAs can be an IP
protocol such as whois or finger, or a more sophisticated application
which may provide Graphical User Interface (GUI) access to the DSA.
Access to a DSA can be accomplished by an individual or automated by
computer application.
Jennings Informational [Page 4]
RFC 1943 Building an X.500 Directory Service in the US May 1996
2.3 The Information Model
In addition to the Directory Model, the X.500 standard defines the
information model used in the Directory Service. All information in
the Directory is stored in "entries", each of which belong to at
least one "object class". In the White Pages application of X.500
object classes are defined as country, organization, organizational
unit and person.
The object classes to which an entry belongs defines the attributes
associated with a particular entry. Some attributes are mandatory
others are optional. System administrators may define their own
attributes and register these with regulating authorities, which will
in turn make these attributes available on a large scale.
Every entry has a Relative Distinguished Name (RDN), which uniquely
identifies the entry. A RDN is made up of the DIT information and the
actual entry.
The Directory operates under a set of rules know as the Directory
schema. This defines correct utilization of attributes, and ensures
an element of sameness throughout the global Directory Service.
Under the White Pages object class "Person" there are three mandatory
attributes:
objectClass commonName surName
These attributes along with the DIT structure above, define the RDN.
An example of an entry under Sandia National Laboratory is shown
here: @c=US@o=Sandia National Laboratory@ou=Employees@cn=Barbara
Jennings
root
/ \
/ \
c=US c=CA
/ \
/ \
o=Sandia National o=ESnet
Laboratory
/ \
/ \
ou=Employees ou=Guests
/ \
/ \
cn=Barbara Jennings cn=Paul Brooks
Jennings Informational [Page 5]
RFC 1943 Building an X.500 Directory Service in the US May 1996
Organizations may define the best structure suited for their DIT.
Typically an organizations DIT will look very much like the
organizations structure itself. A DIT structure is determined by
naming rules and as such, becomes the elements unique Relative
Distinguished Name (RDN). The DIT structure may also be dependent on
whether the DSA information is administered by a flat file or a
database. Extra consideration to designing of the DIT structure
should be taken when using flat files versus a database, as it takes
longer to search through a flat file if the tree structure becomes
too complex or intricate. To obtain information on recommended schema
for DIT structuring see RFC1274 [3].
2.4 Benefits and Uses for X.500 Directory Service
The nature of the X.500 Directory makes it suitable for independently
operated segments that can be expanded to global distribution. The
benefits for local directory use are:
- with the distributed nature of the service, an organization may
separate the responsibility for management of many DSAs and still
retain the overall structure;
- the robustness of this service allows it to provide information to a
wide range of applications. Whereas globally integrated projects must
conform to a specific DIT, independent X.500 operations may define
unique DITs, object classes and attributes as per their specific
needs;
- X.500 is a good alternative for paper directories, offering the
ability to update and modify in an interactive mode. This allows a
company to provide the most current information with less cost and
effort;
- because of the electronic base of X.500, other electronic
applications may interact with the application without human
intervention.
The benefits for global directory use are:
- the distributed nature of X.500 is well suited for large global
applications such as the White Pages Directory. Maintenance can be
performed in a distributed manner;
- X.500 offers good searching capabilities from any level in the DIT.
Also with "User Friendly Naming" in place, searches are very
intuitive;
Jennings Informational [Page 6]
RFC 1943 Building an X.500 Directory Service in the US May 1996
- there are DUA interfaces for the White Pages service available for
all types of workstations. For an overview of X.500 software reference
RFC1632.
- X.500 is an international standard. Using such a standard ensures
interoperability within the worldwide base.
2.5 Other Applications of X.500
In addition to the White Pages, X.500 can be used as a source for any
type of information that needs a distributed storage base.
The University of Michigan is using X.500 for electronic mail
routing. Any mail coming to the university domain, umich.edu; gets
expanded out to a local address that is stored in the rfc822Mailbox
attribute. The University also operates a standard X.500 name server
which provides name lookup service of over 200,000 names. They use
the Lightweight Directory Access Protocol (LDAP) [11].
An implementation of the X.500 Standard directory service has been
incorporated into the Open Software Foundation (OSF) Distributed
Computing Environment (DCE). This component, known as the Global
Directory Service (GDS), provides an area where distributed
application clients can find their application servers. The GDS, in
response to requests made by other clients, provides the unique
network address for a particular DCE resource. Because it is based
on a international standard, GDS can offer access to resources among
users and organizations worldwide. This scalable service can be
performed in DCE environments that range in size from the very small
to the very large.
Lookup services can be implemented into a variety of applications.
Cambridge University in Great Britain implemented the X.500 directory
service into an employee locator application. Based on badge sensors
at strategic locations, this application can determine the
whereabouts of an employee on the campus. As the individual moves
about, the sensors register their location in an X.500 Directory.
Digital Signature Service (DSS) and Privacy Enhanced Mail (PEM) work
on the principal of a directory key server which generates and
provide users with "public" codes that match previously registered
"private" codes. Only the recipient can decipher messages sent in
this fashion. The X.509 [4] standard for key certificates easily fits
within the structure of the X.500 Directory Service.
Jennings Informational [Page 7]
RFC 1943 Building an X.500 Directory Service in the US May 1996
3.0 Legal Issues
3.1 Introduction
Currently in the United States, there are no specific legal rules for
the information that is provided via an electronic directory service.
Various organizations and groups associated with usage of the
Internet, noting a need to address privacy and data integrity issues,
have prepared directives to address this issue. Two such areas
addressed are those of the rights of registrants included in the
directory and the responsibility of administrators to guarantee the
integrity of such data.
Registries containing information that is related to an individual is
freely transferred and unregulated in the US, unless the provider of
the data is an agency or an holder of sensitive information as
defined by federal legislation and further may differ for each state.
An agency is defined as: any executive department, military
department, Government corporation, Government controlled
corporation, or other establishment in the executive branch of the
Government (including the Executive Office of the President), or any
independent regulatory agency. Sensitive data can be financial
records, medical records, and certain legal documents. As previously
noted, each state has their own legislation on sensitive or private
data.The registered persons have little recourse to control list
information short of filing a lawsuit against the information
provider.
For individuals who transfer data across country boundaries, it is
important to understand that other countries may have legislation to
regulate data. Prior to requesting list information from these
countries, an administrator should review applicable legislation and
have some mechanism in place to ensure how data will be handled once
it is crosses the border. Policy Statements for some countries have
been prepared and are provided for via Code of Conduct papers.
3.2 Purpose of the Directory
The operational intent including presentation data and list
registrants and access rights must be clearly defined and stated.
Initially this provides the skeleton of the DIT. Eventually a
statement such as this may provide a basis legally justifying the
directory.
All data presented must be defined in the purpose. If for example, a
directory is for the sole purpose of providing professional
addressing information - an entry would include name, postal address,
office telephone, facsimile number, electronic mail address and
Jennings Informational [Page 8]
RFC 1943 Building an X.500 Directory Service in the US May 1996
company name. Private address information listing the home address
or phone would be prohibited as would any other information not
directly related to addressing.
3.3 User Rights
The North American Directory Forum (NADF) has published a document
that defines the User Bill of Rights [5]. This document defines an
individuals rights regarding the public release of personal or
private information. Among other issues stated, the user has the
right to be notified regarding the inclusion of their information in
a data registry as well as the right to examine and have incorrect
information changed.
This paper is specifically written for the North American Directory
Forum and recommends compliance with US or Canadian laws regulating
privacy and access information.
Although current US legislation does not include all the suggestions
in this document, it is the responsibility of the controller of the
data to respect the rights of the individuals. These recommended
rules can be seen as respect for the individual and the considerate
controller will follow these guidelines within any boundaries that
they may be mandated by.
3.4 Data Integrity
An information provider has the responsibility to guarantee the data
that they make available to users. The integrity of a data source is
heavily weighted by the accuracy and timeliness of the contents.
Interoperable data sources must have concurrence of these factors as
well. The degree to which an information provider can guarantee the
validity of the data that they present, reflects on the validity of
the provider in general. RFC 1355 [6], suggests that a data source
enable accuracy statements describing the process that the individual
NIC will use to maintain accuracy in the database.
In the European community, it is a legal requirement that the
information provider guarantee accurate data.
The controller of the information needs to be certain of the primary
source of data. When possible, the controller should develop routines
of random checks to validate the registry data for correctness.
Jennings Informational [Page 9]
RFC 1943 Building an X.500 Directory Service in the US May 1996
3.5 Data Security
A Directory Service with non-authenticated access from the Internet
is difficult to protect from unauthorized use. Unauthorized use being
defined by each organization within the directory purpose statement.
Typical misuse being by individuals who attempt to duplicate the
directory for unauthorized purposes. Other security measures include:
Access Control Lists (ACLs), limitations on number of entries
returned to a query, and time to search flags. The result of such
controls will affect the legitimate user as well as the user they are
intended to block.
An alternative that may provide protection from misuse is to create
and display an attribute with each entry stating non-approved usage.
This feature will also provide evidence of restricted use in the
event that a legal case is necessary to stop unauthorized access.
The responsibility again falls on the data provider/implementor of
the directory service. Astute programmers will create or make use of
existing tools to protect against data destruction, falsification,
and misuse.
3.6 Conclusions
User Rights, Data Integrity and Protection of data should not be
considered merely in an effort to abide by legal rulings; they should
be the intention of a good data source. A successful Directory
Service must be aware of the requirements of those individuals
inclusive in the list as well as those of the directory users.
In general, at the minimum the following conditions should be
observed:
1. Define the purpose of the Directory.
2. Initially inform all registrants of their inclusion in
a Directory.
3. Prevent the use of data beyond the stated purpose.
4. Limit the attributes associated to an entry within
boundaries of the purpose.
5. Work towards a suitable level of security.
6. Develop a mechanism to correct/remove faulty data
or information that should not be in the Directory.
Jennings Informational [Page 10]
RFC 1943 Building an X.500 Directory Service in the US May 1996
4.0 Infrastructure
4.1 Introduction
The White Pages Project, currently operated by Performance Systems
International (PSI) provides a reliable QUIPU infrastructure for
sites wishing to provide their own X.500 directory. Started in 1989
as the NYSERNet White Pages Pilot Project it was the first
production-quality field test of the Open Systems Interconnection
(OSI) technology running on top of TCP/IP suite of protocols [7].
This pilot X.500 Directory, provided a real-time testbed for a
variety of administrative and usage issues that arise. Today, more
than 30 countries participate in the globally distributed project
with over 1 million entries. The White Pages pilot is one of 37 other
pilots cooperating to provide information in the Nameflow-PARADISE
directory; an European project.
Initially the software was public domain, QUIPU X.500 [8]. This
"shareware" application in conjunction with administrative services
provided free of charge by PSI, allowed for a truly distributed X.500
Directory Service to operate.
In keeping with the Internet rules of operation, the lack of the US
regulations, the suggestions of North American Directory Forum and
the Internet Engineering Task Force (IETF), the complications that
arise from multi-distributed data as a service can be overwhelming.
PSI took on the challenge to provide such a service, and continues to
ensure operations today.
4.2 A Well Maintained Infrastructure
This distributed information service involves the cohesive effort of
all of the participating organizations. The ISO Development
Environment (ISODE) implementation of the OSI Directory, provided the
attributes and uniformity to facilitate this effort.
The primary DSA for the PSI Project is named Alpaca. Operating on a
Sun Sparc 10 with 120 megabytes of memory, this host serves as the
Master for the DSAs of 117 organizations under c=US. Redundancy for
Alpaca is provided by two sources, Fruit Bat operated by PSI and Pied
Tamarin operated by the InterNIC. Slave updates to this host are
provided on a nightly basis from the individual DSAs.
The data presentation is hierarchical in nature and emulates the
common white pages telephone book. The information provided contains
at minimum: a common name, voice phone listing, and electronic mail
addressing. Each entry has a uniqueness associates with it; the
relative distinguished name which is comprised of the entire
Jennings Informational [Page 11]
RFC 1943 Building an X.500 Directory Service in the US May 1996
directory information tree. The DITs may vary slightly, but each must
contain an organization, and a person. The nature of the directory
and the structure of the actual organization for whom the directory
is being provided contribute to the overall DIT structure. The
following is a list of commonly used attributes:
commonName physicalDeliveryOfficeName stateOrProvinceName
description photo streetAddress
userid postOfficeBox surname
favouriteDrink postalAddress telephoneNumber
title rfc822Mailbox facsimileTelephoneNumber
4.3 DUA Interfaces for End Users
There are a variety of user interfaces on the market today that will
provide Directory User Agent access to the X.500 Directory. Standard
protocols such as fred, whois, whois++, finger, are used widely.
Interfaces are also available via World-wide Web browsers and
electronic mail.
Vendors providing DUAs include ISODE Consortium, NeXor, and Control
Data Corporation. These applications operate in conjunction with the
vendor provided DSAs.
Historically DUA interfaces were difficult to implement and required
the entire OSI stack. Implementing such a product on a PC or Apple
platform required skillful programming. The executable for these
platforms were usually very large. The IETF has since defined and
standardized the Lightweight Directory Access Protocol (LDAP) [11]; a
protocol for accessing on-line Directory services which offers
comparable functionality to the Directory Access Protocol (DAP). It
runs directly over TCP and is used by nearly all X.500 clients. LDAP
does not have the overhead of the various OSI layers and runs on top
of TCP/IP.
The functionality varies by specific DUA. Each offers access to the
X.500 Directory. Most offer the ability to make modifications to
entries. There are a few that offer Kerberos authentication.
Further information on LDAP clients for specific platforms can be
found on the University of Michigan WWW server:
http://www.umich.edu/~rsug/ldap.
Another interface that has been tested and recommended for users by
our Dutch (Surfnet) colleagues is Directory Enquiry (DE). Originally
developed by University College London for the Paradise project in
Europe, the engineers at Surfnet have selected DE as the best
interface for "dumb" terminals. They have also translated the
Jennings Informational [Page 12]
RFC 1943 Building an X.500 Directory Service in the US May 1996
interface into Dutch for their local users [12].
Ideally, users should be able to access X.500 directly from their
electronic mail applications. Vendors (other than the ones mentioned
above) have been slow to incorporate the X.500 Standards into their
electronic mail applications.
5.0 Datamanagement & Pilot Projects
5.1 Simple Internet White Pages Service
A wide variety of directory services retrieval protocols has emerged
in the time since the original Internet White Pages was begun in
1989. To ensure that decentralized implementations will have
interoperability with other providers, the IETF Integrated Directory
Services Working Group, is working to create a draft focusing on the
common information and operational modeling issues to which all
Internet White Pages Services (IWPS) must conform to.
Utilizing current information servers, the conceptual model described
includes issues regarding naming, schema, query and response issues
for a narrowly defined subset of directory services. The goal of this
paper is to establish a simple set of information objects, coupled
with a basic set of process requirements that will form a basis which
can lead to ubiquitous IWPS. With this goal in mind, it will be
easier to proved a consistent User view of the various directory
services.
5.2 InterNIC
The InterNIC [9] is a collaborative project of two organizations
working together to offer the Internet community a full scope of
network information services. Established in January 1993 by the
National Science Foundation, the InterNIC provides registration
services and directory and database services to the Internet.
(Internet a global network of more than 13,000 computers networks,
connecting over 1.7 million computers and used by an estimated 13
million people.) In keeping up with the exponential growth of the
Internet, the InterNIC provides a guide to navigate the maze of
available resources.
InterNIC provides two types of services; InterNIC directory and
database services and registration services. AT&T provides the
directory and database services, acting as the pointer to numerous
resources on the network offering X.500 to help users easily locate
other users and organizations on the Internet.
Jennings Informational [Page 13]
RFC 1943 Building an X.500 Directory Service in the US May 1996
5.3 ESnet
The Energy Sciences Network [10], is a nationwide computer data
communications network whose primary purpose is support multiple
program, open scientific research. As part of this support, ESnet
offers networking services including information access and
retrieval, directory services, group communications series, remote
file access services and infrastructure services. As a early member
of the White-Pages Pilot Project, ESnet continues to be a part of the
worldwide distributed directory service based on the ISO/OSI X.500
standard. There are over nineteen ESnet organization represented in
the directory, comprising over 120,000 entries. ESnet provides access
to seven other sites via the X.500 DSAs.
6.0 Recommendations
6.1 General
The X.500 Directory technology is available through several options.
Vendors can provide consultation for schema design as well as supply,
install, and support the software to perform the operations required.
For smaller organizations or companies who do not want to administer
their own DSA, there are providers available who will maintain the
DSAs remotely and provide this service to the Internet. Those with
network and management expertise, can either operate independently or
join one of several white pages directory projects. Careful
consideration must be given to the initial investment required and
the required maintenance process.
6.2 Getting Started
Successful initialization of a directory service requires a
systematic approach. The complexity of offering this type of service
becomes more apparent as implementation progresses. Several aspects
must be considered as this service becomes a cooperative effort among
the technical, administrative, organizational, and legal disciplines.
Procedures must be defined and agreed to at the initial phase of
implementing an X.500 Directory service [13]. The following are
issues that should be addressed in these procedures.
6.3 Who are the Customers?
Defining the customer and the customer requirements will determine
the scope of service to offer. What is the primary purpose for the
directory service? A company may find it desirable to do away with a
paper directory while simultaneously providing the current directory
information. The directory may be for internal use only or expanded
to any users with Internet access. Will the customer use the
Jennings Informational [Page 14]
RFC 1943 Building an X.500 Directory Service in the US May 1996
directory for e-mail address only or is other locational information
such as postal address and telephone number a requirement?
The directory may provide information to electronic customers such as
distributed computing applications as well. In this case, the data
must be provided in machine readable format.
Will the customers extend across country boundaries? Information may
be considered private by one country and not by another. It is
necessary to be aware of the legalities and restrictions for the
locality using the data. Some counties have published a Code of
Conduct with the IETF, explicitly stating the legal restrictions on
directory and list data. Check the archives to determine if the
country with whom information will be shared has presented such
information.
6.4 What are the contents of the Directory?
The information presented in the directory is tightly coupled with
the purpose. If the purpose is to provide addressing information for
individuals, then customary information would include: Name, address,
phone, e-mail address, facsimile number, pager, etc. If the use of
the directory is to facilitate electronic mail routing then the
destination mail address needs to be included for each user. No other
information should be presented in the directory if it is not
directly related to the purpose.
If the directory is internal only, it may be desirable to include the
registrants title as well. Remember that information available on the
Internet is generally open to anyone who wants to access it.
Individuals wishing to target a specific market may access
directories to create customer mailing lists.
The structure or schema of the X.500 Directory must be an initial
consideration. Will the hierarchy follow the company structure or is
a different approach more practical? How many entries will there be
in the directory five or 50,000? A complex hierarchyfor thousands of
users may affect the efficiency of queries.
6.5 What are the rights of the individuals?
The subjects included in the directory shall have well defined
rights. These may be mandated by company policy, legal restrictions,
and the ultimate use of the directory. For a basic Internet White
Pages Service these rights may include:
Jennings Informational [Page 15]
RFC 1943 Building an X.500 Directory Service in the US May 1996
1. the option of inclusion in the directory
2. the right of access to the information
3. the right to have inaccurate entries corrected
The terms and conditions for employees of an organization may affect
these rights. On becoming an employee of any organization, an
individual inevitably agrees to forego certain personal privacies and
to accept restrictions.
Every organization should develop and publish the "rights" that can
be expected by the list registrants.
6.6 Data Integrity
Information that needs to be included in the directory may come from
various sources. Demographic information may originate from the human
resources department. Electronic mail addresses may be provided by
the computer network department. To guarantee data integrity, it is
advised that the data be identified and maintained as corporate
information.
The required timeliness of the data is unique for each DSA. Updates
to the data may be a frequent as once a day or once a month. Updates
to the data must be provided on a regular basis. In cases where data
is time sensitive, an attribute should be included to display the
most recent maintenance date.
A regular check for data accuracy should be included in the directory
administration. Faulty information may put an organization in breach
of any data protection laws and possibly render the company as
unreliable.
6.7 Data Security
Securing networked information resources is inherently complex.
Attempts must be made to preserve the security of the data. These may
include access control lists (ACLs), limiting the number or responses
allowed to queries, or internal/external access to the directory.
The 1993 recommendations have added a complex access control model
that is designed to tightly restrict the access that users may have
to the information in the Directory. Local protection is configured
by the implementor. A secure X.500 Directory should provide tools to
protect against destruction, falsification, and loss of data.
There is not a tool yet that will protect against the misuse of data.
There are flags and limits that can be set from within the
application that will serve somewhat as a barrier to such unwanted
Jennings Informational [Page 16]
RFC 1943 Building an X.500 Directory Service in the US May 1996
use. Any restrictions however, also will affect the legitimate users.
One suggestion is to post a notice of illegitimate use within each
entry. This of course will only serve as a deterrent and as an asset
should legal action be required.
Again, caution must be taken when transferring data between country
and state borders. In the US data regulations differ from state to
state.
6.8 Data Administration
The decentralized nature of the X.500 Directory service means that
each organization has complete control over the data. As part of a
global service however, it is important that the operation of the DSA
be monitored and maintained in a consistent manner. Authorization
must be given to the local manager of the information and in some
cases, the subjects included in the directory may also have
modification privileges.
Once the service is running, the importance of guaranteed operation
can not be overstated. Maintenance of the local Directory will be an
integral part of normal administrative procedures within the
organization and must be defined and agreed upon in the initial
stages of development.
6.9 Conclusion
Establishing a Directory service within an organization will involve
a great deal of cooperative effort. It is essential to get commitment
from the integral parties of an organization at the onset. This
includes the technical, legal, and data managements components of the
organization. Executive level commitment will make it much easier to
get the cooperation necessary.
Operational procedures must be clearly defined, as the inclusion in a
globally distributed service has wide visibility. Adherence to these
procedures must be maintained to the highest degree possible as
misinformation may result in unintentional legal violations and
unreliable access or data can adversely affect on a companys
reputation.
An X.500 Directory can be extremely useful for an organization if it
operates as designed. It may serve as the "hub" of the information
routing and the basis for several everyday activities. A successful
service will be one of the most important tools for communication in
the computer network environment. For people to make use of the
service, they must be able to rely on consistent and accurate
information.
Jennings Informational [Page 17]
RFC 1943 Building an X.500 Directory Service in the US May 1996
References
1. CCITT Blue Book, Volume VIII - Fascicle VIII.8, November 1988.
2. RFC 1632; A Revised Catalog of Available X.500
Implementations. A. Getchell; ESnet, S.
Sataluri; AT&T.
3. RFC 1274; The COSINE and Internet X.500 Schema. P. Barker &
S. Kille.
4. CCITT Blue Book, Volume VIII - Fascicle VIII - Rec. X.509,
November 1988.
5. RFC 1295; User Bill of Rights for entries and listing in the
Public Directory. Networking Working Group; IETF, January
1992.
6. STD 35, RFC 1355; Privacy and Accuracy Issues in Network
Information Center Databases. Curran, Marine, August 1992.
7. RFC 1006, ISO Transport Class 2 Non-use of Explicit Flow
Control over TCP RFC 1006 extension. Y. Pouffary, June 1995.
8. Colin Robbins, NEXOR Ltd., Nottingham, London.
c.robbins@nexor.co.uk
9. InterNIC; Collaborative effort of AT&T and
Network Solutions; info@internic.net
10. ESnet; Managed and funded by the US Department of Energys
Energy Research Office in Scientific Computing (DOE/ER/OSC).
11. RFC 1777; Lightweight Directory Access Protocol, W. Yeong,
T. Howes, S. Kille, March 1995.
12. Building a Directory Service, Final Report test phase SURFnet
X.500 pilot project, June 1995.
13. The X.500 Directory Services: a discussion of the concerns
raised by the existence of a global Directory, Julia M. Hill,
Vol.2/No.1 Electronic Networking, Spring 1992.
14. Directory Services and Privacy Issues, E. Jeunik and E.
Huizer.
Jennings Informational [Page 18]
RFC 1943 Building an X.500 Directory Service in the US May 1996
15. The Little Black Book; Mail Bonding with OSI Directory
Services, Marshall T. Rose, Simon & Schuster Company,
1992.
16. NYSERNet White Pages Pilot Project: Status Report; NYSERNet
Technical Report #89-12-31-1, Marshall T. Rose, December 1989.
17. RFC 1798, Connection-less Lightweight Directory Access
Protocol, A. Young, June 1995.
18. RFC 1781; Using the OSI Directory to Achieve User Friendly
Naming, S. Kille, March 1995.
19. draft-ietf-pds-iwps-design-spec-01.txt, Tony Genovese;
Microsoft, Work in Progress, July 1995.
20. draft-ietf-ids-privacy-00.txt, B. Jennings; Sandia National
Laboratories, S. Sataluri; AT&T, Work in Progress, November
1994.
Glossary
ACL Access Control List; a mechanism to restrict access to data
stored in an X.500 Directory Service
Attribute A collection of attributes belong to an entry in the
Directory Service, and contain information belonging
to that entry.
c= countryName; Object class definition, specifies a country.
When used as part of the directory name, it identifies the
country in which the named object is physically located.
cn= commonName; Attribute defining common name for individuals
included in a directory. In 1988 standards can be up to 64
characters.
CCITT The International Telegraph and Telephone Consultative
Committee.
DAP Directory Access Protocol; the protocol between a DUA and a
DSA.
DIB Directory Information Base; a collection of information
objects in the Directory.
DIT Directory Information Tree; the hierarchy of the distributed
database that makes up an X.500 service.
Jennings Informational [Page 19]
RFC 1943 Building an X.500 Directory Service in the US May 1996
DSA Directory System Agent; an application that offers the
Directory service, this is the database for the Directory.
DUA Directory User Agent; an application that facilitates User
access to a DSA.
E-Mail Electronic Mail. Entry A Directory Service contains entries
on people, organizations, countries, etc. Entries belong to a
certain class, and information on entries is stored in
attributes.
ESnet Energy Sciences Network; nationwide computer data
communications network.
GUI Graphical User Interface.
IETF Internet Engineering Task Force; an internationally
represented task force charged with solving the short-term
needs of the Internet
Internet A collection of connected networks, international,
running the Internet suite of protocols.
InterNIC Directory of Directories, a collaborative project
between AT&T, and Network Solutions, Inc.
IP Internet Protocol; the network protocol offering a
conectionless-mode network service in the Internet suite of
protocols.
ISODE ISO Development Environment, a research tool developed to
study the upper-layers of OSI and deploy network applications
according to the ISO OSI standards and ITU X series of
recommendations.
ITU International Telecommunication Union; formerly the CCITT.
LDAP Lightweight Directory Access Protocol, an Internet Standard
for a lightweight version of DAP running over TCP/IP.
Object Entries in a Directory Service belong to an Object Class to
Class indicate the type and characteristic; e.g. Object Class
"person".
OSI Open Standards Interconnection, An international
standardization program, facilitated by ISO and ITU to develop
standards for data networking.
Jennings Informational [Page 20]
RFC 1943 Building an X.500 Directory Service in the US May 1996
o= organization; An attribute defining the company or
organization that the person works for.
ou= organizational unit; An attribute found under organization.
Denotes the department, division, or other such sub-unit of
the organization that the person works in.
PEM Privacy Enhanced Mail; and Internet Standard for sending
secure Electronic mail.
PSI Performance Systems International, Inc.; operator of the
Internet White Pages Project
QUIPU X.500 Directory implementation developed by Colin Robbins
while at the University College of London.
RDN Relative Distinguished Name; a unique identifier for each list
subject, defined by the hierarchy of the DSA.
RFC Request For Comments; Internet series publications
sn= surname; Attribute defining the surname of the person in the
directory.
TCP/IP Transmission Control Protocol and Internet Protocol; two
internet protocols.
White-Pages Electronic directory, accessible via Internet suite of
protocols.
Whois An Internet standard protocol.
Whois++ An Internet Directory Services protocol; a possible
alternative for X.500 WPS
White Pages Service a Directory Service that contains information on
people and organizations.
X.500 A series of recommendations as defined by the ITU, that
specify a Directory Services protocol.
Jennings Informational [Page 21]
RFC 1943 Building an X.500 Directory Service in the US May 1996
9.0 Security Considerations
Security issues are not discussed in this memo.
Author's Address
Barbara Jennings
Sandia National Laboratories
Scientific Computing Systems
P.O. Box 5800
M/S 0807
Albuquerque, NM 87106
USA
Phone: 505-845-8554
Fax: 505-844-2067
EMail: jennings@sandia.gov
Jennings Informational [Page 22]