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Internet Draft A.P. Jurg Expires: May 1994 SURFnet bv October1993 Introduction to White Pages services based on X.500 <draft-rare-nap-x500intro-00.txt> Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are draft documents valid for a maximum of six months. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the I-D abstract listing contained in each Internet Draft directory to learn the current status of this or any other Internet Draft. Abstract This document explains why an electronic White Pages service is indispensable for the global electronic communication community. It argues that the International ITU-T X.500 (formerly CCITT) and ISO 9594 standard should be used to set up a global White Pages service. The target group of this document consists of IT managers of organizations that are using electronic communication on a day to day basis. This document should help the IT managers to get the necessary executive commitment to start making available the (address) information of their organization through X.500. Jurg Expires: May 1994 [Page 1] Internet Draft Introduction to X.500 for White Pages October 1993 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 ............................................. 4 4 Organizational aspects of X.500. ......................... 5 5 Applications of X.500 .................................... 7 6 References ............................................... 7 1 Introduction Due to the tremendous growth and development of international computer networks we have nowadays the possibility,to overcome - without having to travel - geographical distances when working together with other people. Besides the possibility of using the telephone we may use electronic data exchange to discuss working documents, new ideas, plans or whatsoever. One of the most popular means for this is electronic mail, which can be used to exchange all kinds of electronic data: from informal pure text messages to formatted and multi-media documents. As the number of people connected to computer networks grows (and it does continuously, it is at least doubling each year!), it becomes more difficult to track down people's electronic (mail) addresses. Hence, in order to make global communication over computer networks work, a global White Pages service is indispensable. Such a service should of course provide people's electronic mail addresses, but could also easily contain telephone and fax numbers and postal addresses. Currently the only technical solution for a globally distributed White Pages service is X.500 and there exists an international infrastructure based on X.500 technology called 'Paradise' (Piloting An inteRnAtional DIrectory SErvice), which contains about 1,5 million entries belonging to persons and 3.000 belonging to organizations. Worldwide 35 countries are involved. Paradise is also a project of the EC. The Project continues until september 1994, but after that its operational tasks will be taken over by a European service provider for the R&D community (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 organizational problems and legal issues. In the decision process of joining the international X.500 infrastructure and opening (part) of the local (address) information to the outside world, it is important that an organization fully understands the technical and organizational Jurg Expires: May 1994 [Page 2] Internet Draft Introduction to X.500 for White Pages October 1993 issues involved and the particular benefits of X.500. This document tries to be of help in this matter by firstly explaining the main concepts of X.500 (section 2) and subsequently pointing out its benefits (section 3), what organizational aspects are involved (section 4), and for which other applications the X.500 infrastructure may be used in the near future (section 5). 2 Concept of X.500 The X.500 standard describes a so-called 'Directory Service', which among others, can be used for a global White Pages service. The total concept of X.500 may roughly be divided in the 'Directory model' and the 'Information model'. 2.1 Directory model X.500 uses a distributed approach to achieve the goal of a global Directory Service. The idea is that local (communication oriented) information of an organization is maintained locally in one or more so-called Directory System Agents (DSA's). 'Locally' is a flexible expression here: it is possible that one DSA keeps information of more than one organization. A DSA essentially is a database - where the information is stored according to the X.500 standard (see section 2.2), - that has the ability, where necessary, to exchange data with other DSA's. Through the communication among each other the DSA's form the Directory Information Tree (DIT). The DIT is a hierarchical logical datastructure consisting of a 'root', below which 'countries' are defined. Below the countries (usually) 'organizations' are defined, and below an organization 'persons' or first additional 'organizational units' are defined (see the simplified illustration below; only three countries and no organizational units are presented). The DIT is a representation of the global Directory. root o /|\ / | \ / | \ countries uk de fr /| /\ |\ / | / \ | \ organizations a b c d e f | | | | | | persons ... ... .. .. ... ... Jurg Expires: May 1994 [Page 3] Internet Draft Introduction to X.500 for White Pages October 1993 Each DSA holds a part of the global Directory and is able to find out, through the hierarchical DIT structure, which DSA's hold which parts of the Directory. The standard does not describe how to distribute different parts of the Directory among DSA's. In practice a large organization will have one or more DSA's that hold the part of the DIT from the entry of this organization down to all leaf nodes below it. Smaller organizations may share a DSA with other organizations. The distribution among the DSA's is totally transparent to the users of the Directory. They are only aware of the global DIT. A user accesses the Directory through a so-called Directory User Agent (DUA). The DUA automatically contacts a nearby DSA by means of which the user may search or browse through the DIT to find the information s/he needs. Where the first generation of DUA's are standalone applications, it is expected that in the near future there will be DUA's available that are integrated with e-mail and other applications. 2.2 Information Model Besides the Directory model, the X.500 standard defines also the information model used in the Directory Service. All information in the Directory is stored in 'entries', each of which belongs to at least one so-called 'object class'. In the White Pages application of X.500, on which we focus here, object classes have been defined such as 'country', 'organization', 'organizational unit' and 'person'. The actual information in an entry is determined by so-called 'attributes' that are contained in that entry. The object classes to which an entry belongs define what types of attributes an entry may use and hence what information is specific for entries belonging to that object class. The object class 'person' for example allows attribute types like 'common name', 'telephone number' and 'e-mail address' to be used and the object class 'organization' allows for attribute types like 'organization name' and 'business category'. Dependent 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 name of an entry must be unique on the same level in the subtree of the DIT to which the entry belongs. 3 Benefits of X.500 Why should one use X.500 for a local White Pages service? Here are some good arguments: Jurg Expires: May 1994 [Page 4] Internet Draft Introduction to X.500 for White Pages October 1993 - The flexibility of the service. Besides for public purposes, X.500 may also be used for specific private Directory Service applications. Whereas the definitions of the DIT, object classes and attribute types of the public White Pages information within an organization have to conform to those of the rest of world, the internal applications may use their own DIT structure and their own definitions of object classes and attributes (the values being only visible within (a part) of the organization). Nevertheless one local infrastructure can be used for the public and private applications. - The distributed character of the service. A large organization may distribute the responsibility for the management of the information it presents through X.500 by distributing this information over several DSA's (without losing the overall structure). - X.500 security aspects. It is possible to hide certain attributes of an entry from an unauthorized user. For example the value(s) of the attribute type 'home telephone number' of a person may be visible only to his/her colleagues. By means of strong or simple authentication (using cryptographic keys or simple userid/password identification respectively) it is possible to prohibit unauthorized use of (a part of) the Directory Service. - Good alternative for paper directories. The provision of White Pages services based on X.500 may be a good alternative for paper directories, because the latter directories are rarely up-to-date (due to the printing costs) and because X.500 cannot only be used by humans but also by applications. There are many arguments in favor of X.500 for global use. Here we present some important ones. - A Global Directory. By its distributed nature X.500 is particularly suited for a large global White Pages directory. Maintenance can take place in a distributed way. - Good searching capabilities. X.500 offers the possibility to do searches in any level or in any subtree of the DIT. In order to do a search an attribute type together with a value have to be specified. Then the Directory searches for all entries that contain an attribute of that type with the given value. For example one can search for all persons having a particular job description, or all persons within a country that have beer as a favorite drink. It is up to the responsible managers of the DSA's to decide who may perform such searches and also how many levels deep a search may be. Searches can be done on the basis of an exact or approximate match, etc. It is worth to note here that distributed searches (that need connections to a lot of DSA's) may be expensive. Jurg Expires: May 1994 [Page 5] Internet Draft Introduction to X.500 for White Pages October 1993 - There are DUA's for the White Pages service available for all types of workstations (DOS, Macintosh OS, Unix). - X.500 is an international standard. Using a standard obviously means less problems with interoperability and interworking. Also the standard is updated according to practical experience. 4 Organizational aspects of X.500 The organizational aspects involved in operating a local X.500 Directory can roughly be divided in three sub-aspects: datamanagement, legal issues and cost aspects. With respect to cost aspects there is no publicly known model or experience at the moment. Therefore we will focus here on datamanagement and legal issues. Datamanagement refers to issues that are related to bringing appropriate information into the Directory and keeping it up to date. The following items are of first importance: - Executive commitment. - Structure of the local DIT. In joining the international infrastructure an organization 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 how to use the available attributes can be found in [namguid]. The most important recommendation in the latter document is to keep the local part of the DIT as simple (flat) as possible. The reason is that users from outside the organization may otherwise have difficulties in finding entries of persons within the organization (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 [RFC1274]. - Sources of the data. An organization has to find out where to get what kind of data and develop procedures for uploading its DSA(s). - Delegating responsibilities for updates. Procedures have to be developed for updates of the local Directory. These procedures have to include who is responsible for what. - Security procedures. Rules have to be set for access and security. Who may contact the DSA? Who will have access to which subtrees and what attributes? A study of the legal consequences of presenting (address) information via X.500 lead to the main conclusion that in Europe an organization has to formally register its data collections. Registration implies defining a goal for the Jurg Expires: May 1994 [Page 6] Internet Draft Introduction to X.500 for White Pages October 1993 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 with respect to legal restrictions. For more information on this subject we refer to [legal]. Among the Paradise members there are several pilots running at the moment with the goal to evaluate the organizational aspects. Case studies coming from these pilots can be found in the document [casestud]. Small or medium size organizations that have not too many entries to insert in the Directory may make use of one of the different national initiatives concerning a 'central DSA'. These central DSA's are operated by national service providers and contain the White Pages information of a lot of small and medium size organizations. For organizations in countries without such a national service there is also a European central DSA (Paradise) and an American central DSA (InterNIC). It is noteworthy that the central DSA services are generally only technical services, i.e. a participating organization still has to cover organizational issues. However, part of the central DSA service may be a consult with respect to this matter. 5 Applications of X.500 Besides for White Pages, X.500 can be useful for all kinds of distributed information storage from which humans or machines can benefit. Examples that are likely to use X.500 in the near future are: distribution list mechanism, public key distribution for Privacy Enhanced Mail (PEM), routing of X.400 messages, distribution of EDI identifiers, etc. For more information we refer to [RFC1491]. Here we briefly discuss the first three applications. The distribution list mechanism uses X.500 for finding the e-mail addresses of the persons that have subscribed to a list. The distributed approach of X.500 makes it possible that people change their e-mail address without having to change their subscription to distribution lists. PEM (RFC1421-1424) uses a public key mechanism for exchanging secure e-mail messages. For example: One will be able to send a secure message by encrypting a message with the publicly known (public) key of the recipient. Only the recipient of the message can decipher the message using his/her private key. In order to make such a mechanism work one must have access to the public keys of all possible recipients. X.500 can be used for that. Jurg Expires: May 1994 [Page 7] Internet Draft Introduction to X.500 for White Pages October 1993 At this moment a world-wide pilot is running in which X.400 routing is done by means of X.500. X.400 MTA's use special DUA's to find via the Directory the MTA's 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 (currently tables are used that have to be updated/exchanged periodically). 6 References [RFC1274]P. Barker, S. Kille, "The COSINE and Internet X.500 Schema", RFC1274, University College London, November 1991 [RFC1421]J. Linn, "Privacy Enhancement for Internet Electronic Mail:Part I: Message Encryption and Authentication Procedures", RFC 1421, DEC, February 1993. [RFC1422]S. Kent, "Privacy Enhancement for Internet Electronic Mail:Part II: Certificate-Based Key Management", RFC 1422, BBN, February 1993. [RFC1423]D. Balenson, "Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers", RFC 1423, TIS, February 1993. [RFC1424]B. Balaski, "Privacy Enhancement for Internet Electronic Mail: Part IV: Notary, Co-Issuer, CRL-Storing and CRL- Retrieving Services", RFC 1424, RSA Laboratories, February 1993. [RFC1491]C. Weider, R. Wright, "A Survey of Advanced Usages of X.500", Merit Network, Inc., Lawrence Berkeley Laboratory, July 1993 [namguid] P. Barker, S.E. Kille, T. Lenggenhager, " Naming and Structuring Guidelines for X.500 Directory Pilots", working draft [casestud] Some case studies from the European R&D community, work in progress [legal] E. Jeunink, E. Huizer, "Directory Services and Privacy Issues", work in progress For a good technical introduction to X.500 we also recommend: M.T. Rose, "The Little Black Book", PSI Inc., Prentice Hall Inc., New Jersey, 1992 D. Steedman, "The Directory standard and its application", Technology Appraisals, Twickenham (U.K.), 1993. Jurg Expires: May 1994 [Page 8]