Network Working Group H. Alvestrand
Request for Comments: 2148 UNINETT
BCP: 15 P. Jurg
Category: Best Current Practice SURFnet
September 1997
Deployment of the Internet White Pages Service
Status of this Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
This document makes the following recommendations for organizations
on the Internet:
(1) An organization SHOULD publish public E-mail addresses and
other public address information about Internet users
within their site.
(2) Most countries have laws concerning publication of
information about persons. Above and beyond these, the
organization SHOULD follow the recommendations of [1].
(3) The currently preferable way for publishing the information
is by using X.500 as its data structure and naming scheme
(defined in [4] and discussed in [3], but some countries
use a refinement nationally, like [15] for the US). The
organization MAY additionally publish it using additional
data structures such as whois++.
(4) The organization SHOULD make the published information
available to LDAP clients, by allowing LDAP servers access
to their data".
(5) The organization SHOULD NOT attempt to charge for simple
access to the data.
In addition, it makes the following recommendations for various and
sundry other parties:
(1) E-mail vendors SHOULD include LDAP lookup functionality
into their products, either as built-in functionality or by
providing translation facilities.
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RFC 2148 Internet White Pages Service September 1997
(2) Internet Service providers SHOULD help smaller
organizations follow this recommendation, either by providing
services for hosting their data, by helping them find other
parties to do so, or by helping them bring their own service
on-line.
(3) All interested parties SHOULD make sure there exists a core
X.500 name space in the world, and that all names in this
name space are resolvable. (National name spaces may
elobarate on the core name space).
The rest of this document is justification and details for this
recommendation.
The words "SHOULD", "MUST" and "MAY", when written in UPPER CASE,
have the meaning defined in RFC 2119 [17]
The Internet is used for information exchange and communication
between its users. It can only be effective as such if users are able
to find each other's addresses. Therefore the Internet benefits from
an adequate White Pages Service, i.e., a directory service offering
(Internet) address information related to people and organizations.
This document describes the way in which the Internet White Pages
Service (from now on abbreviated as IWPS) is best exploited using
today's experience, today's protocols, today's products and today's
procedures.
Experience [2] has shown that a White Pages Service based on self-
registration of users or on centralized servers tends to gather data
in a haphazard fashion, and, moreover, collects data that ages
rapidly and is not kept up to date.
The most vital attempts to establish the IWPS are based on models
with distributed (local) databases each holding a manageable part of
the IWPS information. Such a part mostly consists of all relevant
IWPS information from within a particular organization or from within
an Internet service provider and its users. On top of the databases
there is a directory services protocol that connects them and
provides user access. Today X.500 is the most popular directory
services protocol on the Internet, connecting the address information
of about 1,5 million individuals and 3,000 organizations. Whois++ is
the second popular protocol. X.500 and Whois++ may also be used to
interconnect other information than only IWPS information, but here
we only discuss the IWPS features.
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Note: there are other, not interconnected, address databases on the
Internet that are also very popular for storing address information
about people. "Ph" is a popular protocol for use with a stand-alone
database. There are over 300 registered Ph databases on the
Internet. Interconnection of databases however, is highly recommended
for an IWPS, since it ensures that data can be found. Hence Ph as it
is now is not considered to be a good candidate for an IWPS, but
future developments may change this situation (see section 12).
Currently X.500 must be recommended as the directory services
protocol to be used for the IWPS. However, future technology may make
it possible to use other protocols as well or instead.
Since many people think that X.500 on the Internet will be replaced
by other protocols in the near future, it should be mentioned here
that currently LDAP is seen as the surviving component of today's
implementations and the main access protocol for tomorrow's directory
services. As soon as new technology (that will probably use LDAP)
becomes available and experiments show that they work, this document
will be updated.
A summary of X.500 products can be found in [14] (a document that
will be updated regularly).
The sections 3-7 below contain recommendations related to the
publication of information in the IWPS that are independent of a
directory services protocol. The sections 8-11 discuss X.500 specific
issues. In section 12 some future developments are discussed as they
can be foreseen at the time of writing this document.
IWPS information is public address information regarding individuals
and organizations. The IWPS information concerning an individual
should be published and maintained by an organization that has a
direct, durable link with this individual, like in the following
cases:
- The individual is employed by the maintainer's organization
- The individual is enrolled in the university/school that
maintains the data
- The individual is a (personal) subscriber of the maintainer's
Internet service
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The organization that maintains the data does not have to store the
data in a local database of its own. Though running a local database
in the X.500 or Whois++ service is not a too difficult job, it is
recommended that Internet service providers provide database
facilities for those organizations among its customers that only
maintain a small part of the IWPS information or don't have enough
system management resources. This will encourage such organizations
to join the IWPS. Collection of IWPS information and keeping it up-
to-date should always be in the hands of the organization the
information relates to.
Within the current (national) naming schemes for X.500, entries of
individuals reside under an organization. In the case of Internet
service providers that hold the entries of their subscribers this
would mean that individuals can only be found if one knows the name
of the service provider. The problem of this restriction could be
solved by using a more topographical approach in the X.500 naming
scheme, but will more likely be solved by a future index service for
directory services, which will allow searches for individuals without
organization names (see section 12).
The information to be published about an individual should at least
include:
- The individual's name
- The individual's e-mail address, in RFC-822 format; if not
present, some other contact information is to be included
- Some indication of the individual's relationship with the
maintainer
When X.500 is used as directory services protocol the last
requirement may be fulfilled by using the "organizationalStatus"
attribute (see [3]) or by adding a special organizational unit to the
local X.500 name space that reflects the relation (like ou=students
or ou=employees).
Additionally some other public address information about individuals
may be included in the IWPS:
- The individual's phone number
- The individual's fax number
- The individual's postal address
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- The URL of the individual's home page on the Web
In the near future it will be a good idea to also store public key
information.
More information about a recommended Internet White Pages Schema is
found in The Internet White Pages Schema [16]
Organizations should publish the following information about
themselves in the IWPS:
- The URL of the organizations home page on the Web
- Postal address
- Fax numbers
- Internet domain
- Various names and abbreviations for the organization that
people can be expected to search for, such as the English
name, and often the domain name of an organization.
Organizations may also publish phone numbers and a presentation of
themselves.
Data management, i.e. collecting the IWPS information and keeping it
up-to-date, is a task that must not be underestimated for larger
organizations. The following recommendations can be made with respect
to these issues:
- An organization should achieve an executive level commitment
to start a local database with IWPS information. This will
make it much easier to get cooperation from people within the
organization that are to be involved in setting up a
Directory Service.
- An organization should decide on the kind of information the
database should contain and how it should be structured. It
should follow the Internet recommendations for structuring
the information. Besides the criteria in the previous
section, [3] and [4] should be followed if X.500 is used as
directory services protocol.
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- An organization should define criteria for the quality of the
data in the Directory, like timeliness, update frequency,
correctness, etc. These criteria should be communicated
throughout the organization and contributing entities should
commit to the defined quality levels.
- Existing databases within an organization should be used to
retrieve IWPS and local information, to the greatest extent
possible. An organization should involve the people who
maintain those databases and make sure to get a formal
written commitment from them to use their data source. The
organization should rely on these people, since they have the
experience in management and control of local, available
data.
- The best motivation for an organization to join the IWPS is
that they will have a local database for local purposes at
the same time. A local database may contain more, not
necessarily public, information and serve more purposes than
is requested for in the IWPS. In connecting to the IWPS an
organization must "filter out" the extra local information
and services that is not meant for the public IWPS using the
directory services protocol.
Most countries have privacy laws regarding the publication of
information about people. They range from the relaxed US laws to the
UK requirement that information should be accurate to the Norwegian
law that says that you can't publish unless you get specific
permission from the individual. Every maintainer of IWPS information
should publish data according to the national law of the country in
which the local database which holds the information resides.
Some of these are documented in [5] and [1].
A maintainer of IWPS information should also follow some common
rules, even when they are not legally imposed:
- Publish only correct information.
- Give people the possibility to view the information stored
about themselves and the right to withhold information or
have information altered.
- Don't publish information "just because it's there". Publish
what is needed and what is thought useful, and no more.
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Given the number of data management and legal issues that are
involved in publishing IWPS information, good consulting services are
vital to have smaller companies quickly and efficiently join the
IWPS. Internet service providers are encouraged to provide such
services.
In the current IWPS it believed that due to today's technological
constraints, charging users is harmful to the viability of the
service. There are several arguments for this belief:
- Micropayment technology is not available at the moment.
- Subscription services require either that the customer sign
up to multiple search services or that the services are
linked "behind the scene" with all kinds of bilateral
agreements; both structures have unacceptably high overhead
costs and increase the entry cost to the service.
- The current directory services protocols do not support
authentication to a level that would seem appropriate for a
service that charges.
Therefore it is strongly recommended that all lookups by users in the
IWPS are for free. This, of course, does not limit in any way the
ability to use the same IWPS dataset to support other services where
charging may be appropriate.
The IWPS based on the X.500 protocol has a relatively wide
deployment. The current service contains about 1,5 million entries of
individuals and 3,000 of organizations. It is coordinated by Dante,
an Internet service provider in the UK, and known as "NameFLOW-
Paradise".
Though X.500 is sometimes criticized by the fact that its
functionality is restricted by the hierarchical naming structure it
imposes, it provides a reasonably good functionality as has been
shown in several pilots by organizations [5], [2], [6], [7] that are
now running a production X.500 IWPS. User interfaces also determine
the functionality the X.500 IWPS offers. Usually they offer lookups
in the IWPS based on the following user input:
- The name of a person
- The name of an organization this person can be related to
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- The name of a country
As a result they will provide the publicly available information
about the person in question. Most user interfaces offer the
possibility to list organizations in a country and users in an
organization to help users to make their choice for the input. It may
also be possible to use part of the names as input or approximate
names.
Specific user interfaces can provide lookups based on other input,
like e-mail addresses of people or postal addresses of organizations.
Such possibilities may however violate privacy laws. Providers of
directory services services may then be held responsible.
The X.500 naming scheme imposes the requirement on an interconnected
IWPS that all entries stored in it must have unique names (the
"naming scheme"). This is most easily fulfilled by registering all
entries in a "naming tree" with a single root; this is the reason why
the totality of information in an X.500 IWPS is sometimes referred to
as the "Directory Information Tree"
or DIT.
Organizations are strongly encouraged to use the X.500 protocol for
joining the IWPS. The current service is based on the X.500 1988
standard [8] and some Internet-specific additions to the protocol
that connects the local databases [10] and to the access protocol
[9]. Organizations should use X.500 software based on these
specifications and additionally supports [11] for the transportation
of OSI protocols over the Internet.
Organisations may connect to the NameFLOW-Paradise infrastructure
with 1988 DSAs that don't implement [10], but they will lack
automatic replication of knowledge references. This will be
inconvenient, but not a big problem. The 1993 standard of X.500
includes the functionality from [10], but uses a different potocol.
Hence organisations that connect to the infrastructure with a 1993
DSA will also encounter this shortcoming. Section 12 "Future
developments" explains why the infrastructure doesn't use the 1993
standard for the moment.
For recommendations on which attributes to use in X.500 and how to
use them (either for public IWPS information or additional local
information the reader is referred to [3] and [4]. For specific non-
public local purposes also new attributes (and object classes) may be
defined. Generally it should be recommended to use as much as
possible the multi-valuedness of attributes in X.500 as this will
improve the searching functionality of the service considerably. For
example, the organizationalName attribute which holds the name of an
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organization or the commonName attribute which holds the name of a
person should contain all known aliases for the organization or
person. In particular it is important to add "readable" variants of
all attributes that people are expected to search for, if they
contain national characters.
Another recommendation that can be made is that replication of data
[10] between local databases is used in order to improve the
performance of the service. Since replicating all entries of a part
of the IWPS from one local database in another may violate local
privacy laws, it is recommended to restrict replication to country
and organizational entries and knowledge references (which tell where
to go for which part of the IWPS). Of course privacy laws are not
violated when the replicating database is managed by the same
organization as the one that masters the information. So local
replication between two databases within the same organization is
highly recommended.
In general replication within one country will usually be less a
legal problem than across country borders.
Recommendations for the operation of a database in the X.500
infrastructure can be found in [12].
X.500 is not recommended to be used for:
- A Yellow Pages service with a large scope. See [5].
- Searching outside the limited patterns listed here, in
particular searching for a person without knowing which
organization he might be affiliated to.
- Publishing information in other character sets than ASCII,
some of the Latin-based European scripts and Japanese (the
T.61 character sets). While support for these character sets
is available in revised versions of X.500, products that
support the revision aren't commonly available yet.
Some people, for instance when using Novell 4 servers, have decided
that they will use X.500 or X.500-like services as an internal naming
mechanism, without coordinating with an outside source.
This suffers from many of the same problems as private IP addresses,
only more so: your data may need significant restructuring once you
decide to expose them to the outer world.
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A globally accessible X.500 service requires a globally connected
X.500 name space. See [3] and [4] for recommendations on how create a
local part of the global name space.
Though the standard is not very clear about this and the most recent
version (93) appears not to support it, in practice the X.500 name
space is only manageable if there is a single root context operated
under a cooperative agreement. However, one can be sure that there
will be turf battles over it's control.
If those turf battles aren't decided outside the actual running
service, the effect on the service quality will be ruinous.
This document appeals to all players in the field to let existing
practice alone until a better system is agreed and is ready to go
into place; at the moment, the root context of the day is operated by
the Dante NameFLOW-Paradise service.
More information on the Dante NameFLOW-Paradise service is found at
the URL
http://www.dante.net/nameflow.html
At the moment, LDAP as documented in [9] is the protocol that offers
the most X.500 functionality in places where it is not feasible to
implement the full OSI stack.
It is implemented on a lot of platforms, including several PC-type
platforms, and is popular in a multitude of commercial offerings.
A concerted effort to make LDAP available is the publication method
that gives the widest access to the data.
In addition, X.500 DSAs must implement the necessary linkages to make
sure they are properly integrated into the naming/referral tree; in
most cases, this will mean that they should implement the X.500 DSP
protocol at least.
(The question of whether one gateways LDAP to DAP or DAP to LDAP is
irrelevant in this context; it may be quite appropriate to store data
on an LDAP-only server and make it available to the DAP/DSP-running
world through a gateway if the major users all use LDAP)
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Today [October 1996] there are several enhancements to be expected
with respect to IWPS technology.
The most important one to be mentioned here is the creation of a
"Common Indexing Protocol" that must enable the integration of X.500,
Whois++ and protocols that use stand-alone databases. Such a protocol
would not only enable integration but would offer at the same time
the possibility to explore yellow pages services and enhanced
searches, even if used for X.500 only.
In the context of the Common Indexing Protocol the stand-alone LDAP
servers should be mentioned that are announced by several software
developers. These are stand-alone address databases that can be
accessed by LDAP. Currently also a public domain version is available
from the University of Michigan. Also announced is an LDAP-to-DAP
gateway that can integrate a stand-alone LDAP server in an X.500
infrastructure.
Other improvements include defining a common core schema for multiple
White Pages services, leading to the possibility of accessing data in
multiple services through a single access protocol.
The 1993 version of the X.500 standard has already been implemented
in several products. It is an enhancement over the 1988 standard in
several ways, but has not been implemented in the NameFLOW-Paradise
infrastructure yet. The main reason is that the standard doesn't
recognize the existence of a single root DSA, but assumes that the
managers of first-level DSAs (the country DSA's) make bilateral
contracts for interconnection. In the case of NameFLOW-Paradise such
a situation would be unmanageable. In [13] an enhancement of the 1993
standard is proposed that makes a single root possible. As soon as
implementations of [13] are available, NameFLOW-Paradise will
experiment with 1993 DSAs. This is expected in 1997.
Once these developments reach stability, they may be referenced by
later versions of this BCP document.
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The security implications of having a directory are many.
- People will have a standard way to access the information
published.
- People will be able to gather parts of the information for
purposes you never intended (like publishing directories,
building search engines, headhunting or making harassing
phone calls).
- People will attempt to access more of the information than
you intended to publish, by trying to break security
functions or eavesdropping on conversations other users have
with the Directory.
- If modification over the Net is possible, people will attempt
to change your information in unintended ways. Sometimes
users will change data by mistake, too; not all undesired
change is malicious.
The first defense for directory security is to limit your publication
to stuff you can live with having publicly available, whatever
happens.
The second defense involves trying to impose access control. LDAP
supports a few access control methods, including the use of cleartext
passwords. Cleartext passwords are not a secure mechanism in the
presence of eavesdroppers; this document encourages use of stronger
mechanisms if modification is made available over the open Internet.
Otherwise, modification rights should be restricted to the local
intranet.
The third defense involves trying to prevent "inappropriate" access
to the directory such as limiting the number of returned search items
or refuse list operations where they are not useful to prevent
"trolling". Such defenses are rarely completely successful, because
it is very hard to set limits that differentiate between an innocent
user doing wasteful searching and a malicous data troller doing
carefully limited searches.
Future enhancements may include using encrypted sessions, public key
logins and signed requests; such mechanisms are not generally
available today.
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The authors wish to thank the following people for their constructive
contributions to the text in this document:
Peter Bachman <peterb@suport.psi.com>
David Chadwick <D.W.Chadwick@iti.salford.ac.uk>
William Curtin <curtinw@ncr.disa.mil>
Patrik Faltstrom <paf@swip.net>
Rick Huber <rvh@att.com>
Thomas Lenggenhager <lenggenhager@switch.ch>
Sri Saluteri <sri@qsun.ho.att.com>
Mark Wahl <M.Wahl@critical-angle.com>
DAP Directory Access Protocol; protocol used between a DUA and a
DSA to access the Directory Information. Part of X.500.
DSP Directory System Protocol: the protocol used between two DSAs
DSA Directory System Agent - entity that provides DUAs and other
DSAs access to the information stored in the Directory
LDAP Lightweight Directory Access Protocol - defined in RFC 1777
Further terms may be found in RFC 1983.
[1] Jeunik, E. and E. Huizer. Directory Services and Privacy
Issues. Proceedings of Joint European Networking Conference
1993, Trondheim,
http://www.surfnet.nl/surfnet/diensten/x500/privacy.html
[2] Jennings, B. Building an X.500 Directory Service in the US,
RFC1943, May 1996.
[3] Barker, P., S. Kille, T. Lenggenhager, Building Naming and
Structuring Guidelines for X.500 Directory Pilots, P. Barker,
S. Kille, T. Lenggenhager, RFC1617
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[4] The COSINE and Internet X.500 Schema. P. Barker & S. Kille,
RFC1274
[5] Introducing a Directory Service, SURFnet report 1995 (see
URL:
http://info.nic.surfnet.nl/surfnet/projects/x500/introducing/)
[6] Paradise International Reports, University College London,
April 1991 - April 1994
[7] Naming Guidelines for the AARNet X.500 Directory Service,
Michaelson and Prior, RFC 1562
[8] CCITT Blue Book, Volume VIII - Fascicle VIII.8, November 1988
[9] Lightweight Directory Access Protocol, W. Yeong, T. Howes, S.
Kille, RFC1777
[10] Replication and Distributed Operations extensions to provide
an Internet Directory using X.500, S. Kille, RFC1276
[11] ISO transport services on top of the TCP: Version: 3, M.
Rose, D. Cass, RFC1006
[12] Recommendations for an X.500 Production Directory Service, R.
Wright et al., RFC1803
[13] Managing the X.500 Root Naming Context, D. Chadwick, RFCxxxx
[14] A Revised Catalog of Available X.500 Implementations, A.
Getchell, S. Sataluri, RFC1632
[15] A Naming Scheme for c=US, The North American Directory Forum,
RFC1255
[16] A Common Schema for the Internet White Pages Service, T.
Genovese, B. Jennings, Work In Progress.
[17] Key words for use in RFCs to Indicate Requirement Level, S.
Bradner, RFC 2119,
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