RFC 1684
Introduction to White Pages Services based on X.500
Okay bestie, let's get into it 💖 This is RFC 1684, called Introduction to White Pages Services based on X.500. It's from the Network Working Group 🌸, written by P. Jurg of SURFnet bv, and dated August 1994. It's filed as Informational, which means it's giving info to the Internet community and isn't a standard (more on that below 🎀). It doesn't obsolete or update any other RFC, since the header doesn't list any. This is part 1 of 2, so more is coming!
Status of this Memo ✨
This memo is here to provide information for the Internet community 🦋. It does not specify an Internet standard of any kind, so it's not a standard, bestie. Distribution of this memo is unlimited, so share it with everyone 💜.
Abstract 🎀
This one's for organisations that use local and global electronic communication every single day, for whom an electronic White Pages Service is basically indispensable 😭.
The document gives you an intro to the international ITU-T (formerly CCITT) X.500 and ISO 9594 standard, which is especially suited for providing an integrated local and global electronic White Pages Service 🧚.
We also get a short overview of the experience gained from the Paradise X.500 pilot, plus references to more detailed information 📚.
It's useful for managers of those organisations who need the executive commitment to make their organisation's address information available by means of X.500 💅.
Table Of Contents 📋
1. Introduction ................................................ 2
2. Concept of X.500 ............................................ 3
2.1 Directory Model ......................................... 3
2.2 Information Model ....................................... 4
3. Benefits of X.500 .......................................... 5
4. Organisational aspects of X.500(experience from Paradise) .. 6
5. Applications of X.500 ...................................... 8
6. References ................................................. 9
7. Security Considerations .................................... 10
8. Author's Address ........................................... 101. Introduction 🌈
Huge international computer networks mean we can now overcome geographical distances without having to travel at all ✈️ (we get to work with people anywhere, from our own desks 🙌). Besides the phone, we can swap electronic data to discuss working documents, new ideas, plans or literally whatever. One of the most popular ways to do this is electronic mail, which can carry every kind of electronic data, from informal plain text messages all the way to formatted and multi-media documents 💌.
As more and more people connect to computer networks (and it's growing continuously, at least doubling each year!! 😭), it gets harder to track down people's electronic (mail) addresses 🔍. So if we want global communication over computer networks to work, a global White Pages service is absolutely indispensable 💯. It should definitely provide people's electronic mail addresses, but it could also easily contain telephone and fax numbers and postal addresses 📬.
Right now, one technical solution for a globally distributed White Pages service is X.500, and there's an international infrastructure based on X.500 technology called 'Paradise' (Piloting An inteRnationAl DIrectory SErvice) 🏝️. It contains about 1.5 million entries belonging to persons and 3,000 belonging to organisations, and 35 countries are involved worldwide. Paradise is also an EC project. The project runs until September 1994. After that, its operational tasks will be taken over by a European service provider for the R&D community, called DANTE 🌍.
The goal of Paradise and related national initiatives is to stimulate and extend the use of the X.500 White Pages service 🚀. Within the pilot, attention is paid to technical and organisational aspects. The Paradise infrastructure is mainly based on the Internet Protocol. The specific issues related to using the Internet Protocol for X.500 can be found in [5] 📖.
When an organisation decides whether to join the international X.500 infrastructure and open up (part of) its local address information to the outside world, it's important that it fully understands the technical and organisational issues involved 🤔.
This document helps with this by first explaining the main concepts of X.500 (section 2), then pointing out its benefits (section 3), the organisational aspects involved (section 4), and which other applications the X.500 infrastructure may be used for in the near future (section 5) 🗺️.
2. Concept of X.500 🎀
X.500 describes a so-called 'Directory Service', which can be used for all types of electronic directories 💅. This document focuses on using X.500 for a global White Pages Directory. The concept of X.500 can roughly be divided into the 'Directory model' and the 'Information model' ✨.
2.1 Directory model 🌳
X.500 takes a distributed approach to reach its goal of a global Directory Service 🌐. The idea is that an organisation's local (communication oriented) information is maintained locally, in one or more so-called Directory System Agents (DSA's). 'Locally' is a flexible word here: one DSA can keep information for more than one organisation 🙈. A DSA is essentially a database that:
- stores the information according to the X.500 standard (see section 2.2),
- has the ability, where necessary, to exchange data with other DSA's.
Through communicating with each other, the DSA's form the Directory Information Tree (DIT) 🌲. The DIT is a virtual hierarchical datastructure with a 'root' at the top, below which 'countries' are defined. Below the countries (usually) 'organisations' are defined, and below an organisation come 'persons', or first additional 'organisational units' 🏢. Here's a simplified illustration where only three countries and no organisational units are shown:
root o
/|\
/ | \
/ | \
countries uk de fr
/ | /\ |\
/ | / \ | \
organisations a b c d e f
| | | | | |
persons .. .. ... .... ...The DIT is a representation of the global Directory 🌍.
Each DSA holds a part of the global Directory and can figure out, through the hierarchical DIT structure, which DSA holds which parts of the Directory 🧭.
The standard doesn't describe how to distribute different parts of the Directory among DSA's. What it does say is that the information corresponding to a single node of the DIT (i.e., a country, organisation, person) cannot be distributed over several DSA's 🚫. In practice, a large organisation will maintain one or more DSA's to hold its part of the Directory, while smaller organisations may share a DSA with other organisations 🤝. Either way, the distribution among the DSA's is totally transparent to the users of the Directory ✨.
A user of the Directory can be a person or a computer 🤖. A user accesses the Directory through a so-called Directory User Agent (DUA). The DUA automatically contacts a nearby DSA, which lets the user search or browse through the DIT and retrieve the corresponding information 🔎. A DUA can be built into all sorts of user interfaces, so users may access the Directory through dedicated DUA interfaces or through e-mail applications, for example 📨. Currently most DUA interfaces used by persons are dedicated, but it's expected that in the near future a lot of DUA interfaces will be integrated with other applications 🔮.
2.2 Information Model 🧾
Besides the Directory model, the X.500 standard also defines the information model used in the Directory Service 📋.
All information in the Directory is stored in 'entries', and each one belongs to at least one so-called 'object class' 🗂️. In the White Pages application of X.500, which is what we're focusing on here, object classes are defined such as 'country', 'organisation', 'organisational unit' and 'person' 💜.
The actual information in an entry is determined by so-called 'attributes' contained in that entry. The object classes an entry belongs to define what types of attributes the entry may use, and therefore what information is specific to entries of that object class 🧩. For example, the object class 'person' allows attribute types like 'common name', 'telephone number', and 'e-mail address' to be used, while the object class 'organisation' allows attribute types like 'organisation name' and 'business category' 💅. Depending on its type, an attribute can take one or more values 🌈.
To specify the name of an entry in the DIT, at least one attribute value of the entry is used 🏷️. The entry of a person is usually named after the value of the attribute type 'common name'. The name of an entry must be unique on the same level in the subtree of the DIT to which the entry belongs 🫶.
Check out this example of an entry belonging to the object class 'person' 👀:
Attribute type Attribute value
-------------- --------------
Object Class: top
person
Common Name: Thomas Lenggenhager
T. Lenggenhager
Surname: Lenggenhager
Postal Address: SWITCH
Limmatquai 138
CH-8001 Zuerich
Telephone Number: +41 1 268 1540
Facsimile Telephone Number: +41 1 268 1568
Mail: lenggenhager@switch.chThis entry corresponds to the node in the DIT that sits below the node of the organisation 'SWITCH', and it's named after the first value of the attribute type 'common name': 'Thomas Lenggenhager' 🦋.
3. Benefits of X.500 ✨
okay so, why would anyone pick X.500 for a local White Pages service? 🤔 here are some really good arguments, bestie 💖
- the distributed character of the service 🌸 a big organisation can split up the responsibility for managing the info it publishes through X.500 by spreading that info over several DSAs. and the overall structure? still totally intact 🧚
- the flexibility of the service 🦋 X.500 isn't just for public stuff, it can also power specific private Directory Service apps. so the public White Pages info in an org has to match the DIT, object class and attribute type definitions used by the rest of the world 🌍 but internal apps can use their own DIT structure and their own object classes and attributes (and those values only show up within (a part) of the org) 👀 and yes, one local setup can serve both public and private computers at once 💅
- a good alternative to paper directories 📄 paper ones are rarely up-to-date (printing costs, ugh) and X.500 isn't only for humans, applications can use it too 🫶
some super important arguments for global use:
- distributed = perfect for a huge global White Pages 🌍 maintenance can happen in a distributed way, which is iconic 👑
- the searching is elite 🔍 X.500 lets you search at any level or in any subtree of the DIT. you specify an attribute type together with a value, and the Directory finds all the entries that contain an attribute of that type with that value. for example, you could look up every person in an org with a particular common name, or every org in a country whose business category is telecommunications. the organisations that maintain the DSAs decide who gets to do which searches, and how many levels deep a search is allowed to go 🙃
searches can be an exact match or an approximate one. ngl, distributed searches (the ones that need connections to a lot of DSAs) can get expensive and generally aren't encouraged 💀
- DUA interfaces for all the workstations 💻 there are DUA interfaces for the White Pages service available for all types of workstations (DOS, Macintosh OS, Unix). for an overview of X.500 software, check RFC 1292 [2] or updates of this document 📚
- it's an international standard 🌏 using a standard obviously means fewer problems with interoperability and interworking. and the standard gets updated based on practical experience too 🙌
4. Organisational aspects of X.500 (experience from Paradise) ✨
running a local X.500 (or any other electronic) Directory comes with organisational aspects, and they can roughly be split into three sub-aspects: data management, legal issues and cost aspects. with cost aspects, there's no publicly known model or experience at the moment 🤷♀️
so the focus in this document is on data management and legal issues 🎯
data management is all about getting the right info into the Directory and keeping it up to date 📝
from the experience of Paradise participants, these items are of first importance 👑:
- executive commitment 💼 without this, it's almost impossible to create an organisation-wide, up-to-date electronic Directory 😭
- structure of the local DIT 🗂️ joining the international infrastructure means an organisation has to conform to some rules for the local DIT structure as presented to the global X.500 infrastructure. a recommendation on how to structure a local DIT and use the available attributes can be found in [7]. the most important recommendation in that document is to keep the local part of the DIT as simple (flat) as possible, because users from outside the organisation may have a hard time finding entries of persons inside it (searches in the DIT are often only allowed one level deep) 🙈
- attributes to be used 🏷️ for the existing infrastructure, the objects and associated attributes that are globally used are documented in [1] 📖
- sources of the data 🔎 an organisation has to find out where to get what kind of data, and develop procedures for uploading it to its DSA('s) ⬆️
- delegating responsibilities for updates 🤝 procedures have to be developed for updates of the local Directory, and those procedures have to include delegation of responsibilities 📋
- security procedures 🔐 rules have to be set for access and security. who may contact the DSA? who gets access to which subtrees and what attributes? 👀
a study of the legal consequences of presenting (address) info via X.500 led to the main conclusion that in Europe, an organisation has to formally register its data collections (yes, this one is serious, babe). registration implies defining a goal for the application 🎯 this has to be done for the White Pages service as well as for any deviating local application of X.500. however, the different national laws may differ when it comes to legal restrictions. for more info on this subject, check out "Building a Directory Service, Final Report test phase SURFnet X.500 pilot project", E. Huizer, SURFnet B.V., Utrecht NL, 1994. (copies available from SURFnet B.V.) 📚
several Paradise members have pilots running right now to evaluate the organisational aspects 🧪 and case studies coming from those pilots will be documented ✨
small or medium size organisations that don't have too many entries to insert can use one of the different national initiatives concerning a 'central DSA' 🏢 these central DSAs are operated by national service providers and contain the White Pages info of a lot of small and medium size organisations. for organisations in countries without such a national service, there's a European central DSA (Paradise) and an American central DSA (InterNIC) 🌍 it's worth noting that central DSA services are only technical services, so a participating organisation still has to cover the organisational issues 😤 but part of a central DSA service may be consultancy with respect to data management and legal issues 💁♀️
5. Applications of X.500 ✨
besides White Pages, X.500 can be useful for all kinds of distributed info storage that humans or machines can benefit from 🧠 examples that are likely to use X.500 in the near future are: the distribution list mechanism, public key distribution for Privacy Enhanced Mail (PEM), routing of X.400 messages, distribution of EDI identifiers, etc. for more, see [7]. the first three get a quick look below 👇
distribution lists 📬 the distribution list mechanism uses X.500 to find the e-mail addresses of the persons who have subscribed to a list. the distributed approach means people can change their e-mail address without having to change their subscriptions to distribution lists 🙌
PEM 🔐 (see a.o. [8] or [4]) PEM uses a public key mechanism for exchanging secure e-mail messages. for example, you can send a secure message by encrypting it with the publicly known (public) key of the recipient 🗝️ only the recipient can decipher the message, using his/her private key. to make this mechanism work, you need access to the public keys of all possible recipients, and X.500 can be used for that 💜
X.400 routing 🌐 a world-wide pilot is running in which X.400 routing is done by means of X.500. X.400 MTAs use special DUAs to find, via the Directory, the MTAs to which the recipients of a message want their mail to be delivered. the distributed approach of X.500 will mean much less routing management, since right now tables are used that have to be updated/exchanged periodically 🦋
6. References 📚
[1] Barker, P., and S. Kille,"The COSINE and Internet X.500 Schema", RFC 1274, University College London, November 1991.
[2] Getchell, A., and S. Sataluri, Editors, "A Revised Catalog of Available X.500 Implementations", FYI 11, RFC 1632, Lawrence Livermore National Laboratory, AT&T Bell Laboratories, May 1994.
[3] Weider, C., and J. Reynolds, "Executive Introduction to Directory Services using the X.500 Protocol", FYI 13, RFC 1308, ANS, USC/Information Sciences Institute, March 1992.
[4] Linn, J., "Privacy Enhancement for Internet Electronic Mail:Part I: Message Encryption and Authentication Procedures", RFC 1421, IAB IRTF PSRG, IETF PEM WGs, Feblruary 1993.
[5] Hardcastle-Kille, S., Huizer, E., Cerf, V., Hobby, R., and S. Kent, "A Strategic Plan for Deploying an Internet X.500 Directory Service", RFC 1430, ISODE Consortium, SURFnet bv, Corporation for National Research Initiatives, University of California, Davis, Bolt, Beranek and Newman, February 1993.
[6] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access Protocol", RFC 1487, Performance Systems International, University of Michigan, ISODE Consortium, July 1993.
[7] Weider, C., and R. Wright, R., "A Survey of Advanced Usages of X.500", FYI 21, RFC 1491, Merit Network, Inc, Lawrence Berkeley Laboratory, July 1993.
[8] "Privacy Enhanced Mail in more detail", Zegwaart, E., Computer Networks for Research in Europe Vol. 2, pp. 63-71.
[9] Barker, P., Kille, S., and T. Lenggenhager, T., "Naming and Structuring Guidelines for X.500 Directory Pilots", RTR 11/RFC 1617, University College London, ISODE Consortium, SWITCH, May 1994.
For a good technical introduction to X.500 we also recommend:
[10] Rose, M., "The Little Black Book", PSI Inc., Prentice Hall Inc., New Jersey, 1992.
[11] Steedman, D., "The Directory standard and its application", Technology Appraisals, Twickenham (U.K.), 1993.
7. Security Considerations 😱
Security issues are not explicitly discussed in this memo. Yes, you read that right, bestie. 💀
8. Author's Address 💌
Peter Jurg
SURFnet bv
Postbus 19035
NL-3501 DA Utrecht
The Netherlands
Phone: +31 30 310290
Fax: +31 20 340903
RFC822: Peter.Jurg@surfnet.nl
X.400: C=nl; ADMD=400net; PRMD=surf; O=surfnet; S=jurg📦 where this page comes from
- ietf: rfc1684 1994-08
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms