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   minimum, an important requirement for the migration strategy is that
   only one common set of routing procedures is used for both 84 and 88
   systems in the European R&D MHS.

6. Conclusion

    1. The transition from X.400(84) to ISO 10021/X.400(88) is
       worthwhile for the European R&D MHS, to provide:

          - P7 Message Store to support remote UAs.
          - Distribution Lists.
          - Support for Directory Names.
          - Standardised external Body Part types.
          - Redirection.
          - Security.
          - Future extensibility.
          - Physical Delivery.

    2. To minimise the number of transitions the European R&D MHS
       target should be ISO 10021 rather than CCITT X.400(88) -
       i.e., straight to use of the full OSI stack with Normal-mode
       RTS.

    3. To give a useful quality of service, the European R&D MHS
       should not use minimal 88 MTAs which relay the syntax but
       understand none of the semantics of extensions. In
       particular, all European R&D MHS 88 MTAs should generate
       reports containing extensions copied from the subject message
       and route reports through the DL expansion hierarchy where
       appropriate.





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RFC 1615         Migrating from X.400(84) to X.400(88)          May 1994


    4. The European R&D MHS should carefully plan the transition so
       that it is never necessary to relay through an 84 system to
       provide connectivity between any two 88 systems.

    5. The European R&D MHS should consider the additional
       functionality that can be provided to X.400(84) users by
       adopting an enhanced specification of the interworking rules
       between X.400(84) and ISO 10021/X.400(88), and weigh this
       against the cost of building and maintaining its own
       convertors. The advantages to X.400(84) users are:

         - Ability to generate 88 common-name attribute, likely to
           be widely used for naming DLs.
         - Consistent reception of DL-expanded and Redirected
           messages.
         - Ability to receive extended 88 P2 contents
           automatically downgraded to 84 P2.

7. Security Considerations

   Security issues are not discussed in this memo.






























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RFC 1615         Migrating from X.400(84) to X.400(88)          May 1994


Appendix A - DL-expanded and Redirected Messages in X.400(84)

   This Annex provides an additional to the rules for "Interworking with
   1984 Systems" contained in Annex B of ISO 10021-6/X.419,  to give
   X.400(84) recipients consistent reception of messages  that have been
   expanded by a DL or redirected.  It is applicable  only if the
   transition topology for the European R&D MHS  recommended in section
   3 is adopted.

   Replace the first paragraph of B.2.3 by:

   If an other-actions element is present in any trace- information-
   elements, that other-actions element and all preceding trace-
   information-elements shall be deleted. If an other-actions element is
   present in any subject-intermediate-trace-information- elements, that
   other-actions element shall be deleted.

Appendix B - Bibliography

   [1] ENV 41201, "Private MHS UA and MTA: PRMD to PRMD", CEN/CENELEC,
       1988.

   [2] Kille, S., "X.400 1988 to 1984 downgrading", RTR 3, RFC 1328,
       University College London, May 1992.

   [3] ENV 41202, "Protocol for InterPersonal Messaging between MTAs
       accessing the Public MHS", CEPT, 1988.

   [4] Kille, S.  "Mapping between X.400(1988)/ISO 10021 and RFC 822",
       RTR 2, RFC 1327; University College London. May 1992.

   [5] Kille, S., "Using the OSI Directory to achieve User Friendly
       Naming", RFC 1484, ISODE Consortium, July 1993.

   [6] Crocker, D., "Standard for the Format of ARPA Internet Text
       Messages", STD 11, RFC 822, University of Delaware, August 1982.

   [7] Craigie, J., "COSINE Study 8.2.2. Migration Strategy for
       X.400(84) to X.400(88)/MOTIS", Joint Network Team, 1988.

   [8] Craigie, J., "ISO 10021-X.400(88): A Tutorial for those familiar
       with X.400(84)", Computer Networks and ISDN systems 16, 153-160,
       North-Holland, 1988.

   [9] Manros, C.-U., "The X.400 Blue Book Companion", ISBN 1 871802 00
       8, Technology Appraisals Ltd, 1989.





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  [10] CCITT Recommendations X.400 - X.430, "Data Communication
       Networks: Message Handling Systems", CCITT Red Book, Vol. VIII -
       Fasc. VIII.7, Malaga-Torremolinos, 1984.

  [11] CCITT Recommendations X.400 - X.420 (ISO IS-10021), "Data
       Communication Networks: Message Handling Systems", CCITT Blue
       Book, Vol. VIII - Fasc. VIII.7, Melbourne, 1988.

Appendix C - MHS Terminology

   Message Handling is performed by four types of functional entity:
   User Agents (UAs) which enable the user to compose, send, receive,
   read and otherwise process messages; Message Transfer Agents (MTAs)
   which provide store-and-forward relaying services; Message Stores
   (MSs) which act on behalf of UAs located remotely from their
   associated MTA (e.g., UAs on PCs or workstations); and Access Units
   (AUs) which interface MHS to other communications media (e.g., Telex,
   Teletex, Fax, Postal Services). Each UA (and MS, and AU) is served by
   a single MTA, which provides that user's interface into the Message
   Transfer Service (MTS).

   Collections of MTAs (and their associated UAs, MSs and AUs) which are
   operated by or under the aegis of a single management authority are
   termed a Management Domain (MD). Two types of MD are defined: an
   ADMD, which provides a global public message relaying service
   directly or indirectly to all other ADMDs; and a PRMD operated by a
   private concern to serve its own users.

   A Message is comprised of an envelope and its contents. Apart from
   the MTS content-conversion service, the content is not examined or
   modified by the MTS which uses the envelope alone to provide the
   information required to convey the message to its destination.

   The MTS is the store-and-forward message relay service provided by
   the set of all MTAs. MTAs communicate with each other using the P1
   Message Transfer protocol.















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Appendix D - Abbreviations

      ACSE     Association Control Service Element
      ADMD     Administration Management Domain
      ASCII    American Standard Code for Information Exchange
      ASN.1    Abstract Syntax Notation One
      AU       Access Unit
      CCITT    Comite Consultatif International de Telegraphique et
               Telephonique
      CEN      Comite Europeen de Normalisation
      CENELEC  Comite Europeen de Normalisation Electrotechnique
      CEPT     Conference Europeene des Postes et Telecommunications
      CONS     Connection Oriented Network Service
      COSINE   Co-operation for OSI networking in Europe
      DL       Distribution List
      DIS      Draft International Standard
      EN       European Norm
      ENV      Draft EN, European functional standard
      IEC      International Electrotechnical Commission
      IPM      Inter-Personal Message
      IPMS     Inter-Personal Messaging Service
      IPN      Inter-Personal Notification
      ISO      International Organisation for Standardisation
      JNT      Joint Network Team (UK)
      JTC      Joint Technical Committee (ISO/IEC)
      MD       Management Domain (either an ADMD or a PRMD)
      MHS      Message Handling System
      MOTIS    Message-Oriented Text Interchange Systems
      MTA      Message Transfer Agent
      MTL      Message Transfer Layer
      MTS      Message Transfer System
      NBS      National Bureau of Standardization
      OSI      Open Systems Interconnection
      PRMD     Private Management Domain
      RARE     Reseaux Associes pour la Recherche Europeenne
      RFC      Request for Comments
      RTR      RARE Technical Report
      RTS      Reliable Transfer Service
      WG-MSG   RARE Working Group on Mail and Messaging












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RFC 1615         Migrating from X.400(84) to X.400(88)          May 1994


Authors' Addresses

   Jeroen Houttuin
   RARE Secretariat
   Singel 466-468
   NL-1017 AW Amsterdam
   Europe

   Phone: [phone]
   RFC 822: [e-mail]
   X.400: C=NL;ADMD=400net;PRMD=surf;
   O=rare;S=houttuin;


   Jim Craigie
   Joint Network Team
   Rutherford Appleton Laboratory
   UK-OX11 OQX Chilton
   Didcot, Oxfordshire
   Europe

   Phone: [phone]
   RFC 822: [e-mail]
   X.400: C=GB;ADMD= ;PRMD=UK.AC;
   O=jnt;I=J;S=Craigie;


























Houttuin & Craigie                                             [Page 17]