rfc1684.txt

来自「<VC++网络游戏建摸与实现>源代码」· 文本 代码 · 共 564 行 · 第 1/2 页


RFC 1684       Introduction to X.500 White Pages Services    August 1994


      - 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 not only can be used by humans but also by
        applications.

   Some important arguments in favour of X.500 for global use are:

      - 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 in an
        organisation having a particular common name, or all
        organisations within a country that have telecommunications
        as their business category. It is up to the organisations
        that maintain the DSA's to decide who may perform which
        searches and also how many levels deep a search may be.

        Searches can be done on the basis of an exact or approximate
        match. It is worthwile to note that distributed searches
        (that need connections to a lot of DSA's) may be expensive
        and are generally not encouraged.

      - There are DUA interfaces for the White Pages service
        availablefor all types of workstations (DOS, Macintosh OS,
        Unix). For an overview of X.500 available software see
        RFC 1292 [2] or updates of this document.

      - 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.  Organisational aspects of X.500 (experience from Paradise)

   The organisational aspects involved in operating a local X.500 (or
   any other electronic) 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.




RARE Working Group on Network Applications Support              [Page 6]

RFC 1684       Introduction to X.500 White Pages Services    August 1994


   Therefore the focus in this document is on datamanagement and legal
   issues.

   Data management refers to issues that are related to inserting
   appropriate information into the Directory and keeping it up to date.

   From the experience of participants in Paradise we obtain that the
   following items are of first importance:

      - Executive commitment. Without this it is almost impossible to
        create an organisation wide up-to-date electronic Directory.

      - Structure of the local DIT. In joining the international
        infrastructure 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 how to use the available attributes can be found in
        [7]. 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
        organisation may otherwise have difficulties in finding
        entries of persons within the organisation (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
        its DSA('s).

      - Delegating responsibilities for updates. Procedures have to
        bedeveloped for updates of the local Directory. These
        procedures have to include delegation of responsibilities.

      - 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 organisation
   has to formally register its data collections.  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 with respect
   to legal restrictions. For more information on this subject we refer
   to "Building a Directory Service, Final Report test phase SURFnet



RARE Working Group on Network Applications Support              [Page 7]

RFC 1684       Introduction to X.500 White Pages Services    August 1994


   X.500 pilot project", E.  Huizer, SURFnet B.V., Utrecht NL, 1994.
   (copies available from SURFnet B.V.)

   Among the Paradise members there are several pilots running at the
   moment with the goal to evaluate the organisational aspects. Case
   studies coming from these pilots will be documented.

   Small or medium size organisations that have not too many entries to
   insert in the Directory may use 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 organisations. For
   organisations in countries without such a national service there is
   also a European central DSA (Paradise) and an American central DSA
   (InterNIC). It is worth noting that the central DSA services are only
   technical services, i.e., a participating organisation still has to
   cover the organisational issues. However, part of a central DSA
   service may be consultancy with respect to datamanagement and legal
   issues.

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 [7]. Below the
   first three applications are briefly discussed.

   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 (see a.o. [8] or [4]) uses a public key mechanism for exchanging
   secure e-mail messages. For example: one will be able to end 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 this purpose.

   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



RARE Working Group on Network Applications Support              [Page 8]

RFC 1684       Introduction to X.500 White Pages Services    August 1994


   mean much less routing management (currently 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.



RARE Working Group on Network Applications Support              [Page 9]

RFC 1684       Introduction to X.500 White Pages Services    August 1994


7.  Security Considerations

   Security issues are not explicitly discussed in this memo.

8.  Author's Address

   Peter Jurg
   SURFnet bv
   Postbus 19035
   NL-3501 DA Utrecht
   The Netherlands

   Phone: [phone]
   Fax: [phone]
   RFC822: [e-mail]
   X.400: C=nl; ADMD=400net; PRMD=surf; O=surfnet; S=jurg



































RARE Working Group on Network Applications Support             [Page 10]