rfc1664.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   according to the algorithms specified in RFC1327. If a DNS error code
   is returned, an error message should be logged and the gateway
   operation is delayed as for timeout. These pathological situations,
   however, should be avoided with a careful duplication and chaching
   mechanism which DNS itself provides.

   Searching the nameserver which can authoritatively solve the query is
   automatically performed by the DNS distributed name service.

5.1 A DNS query example

   An RFC1327 mail-gateway located in the Internet, when translating
   addresses from RFC822 to X.400, can get information about the RFC1327
   mapping rule asking the DNS. As an example, when translating the
   address SUN.CCE.NRC.IT, the gateway will just query DNS for the
   associated PX resource record. The DNS should contain a PX record
   like this:

   *.cce.nrc.it.  IN PX 50   cce.nrc.it.  O-cce.PRMD-nrc.ADMD-acme.C-it.

   The first query will return immediately the appropriate mapping rule
   in DNS store format.

   There is no ".G." at the end of the obtained PX RDATA value, thus
   applying the syntax translation specified in paragraph 4.2 the
   RFC1327 Table 2 mapping rule will be obtained.

   Let's now take another example where a 'gate' table rule is returned.
   If we are looking for an RFC822 domain ending with top level domain
   "MW", and the DNS contains a PX record like this,

      *.mw.   IN  PX  50  mw.  O-cce.PRMD-nrc.ADMD-acme.C-it.G.

   DNS will return 'mw.' and 'O-cce.PRMD-nrc.ADMD-acme.C-it.G.', i.e., a
   'gate' table entry in DNS store format. Dropping the final ".G." and
   applying the syntax translation specified in paragraph 4.2 the
   original rule will be available. More over, the ".G." flag also tells



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   the gateway to use DDA encoding for the inquired RFC822 domain.

   On the other hand, translating from X.400 to RFC822 the address

      C=de; ADMD=pkz; PRMD=nfc; O=top;

   the mail gateway should convert the syntax according to paragraph
   4.2, apply the 'Country code convention' described in 4.2.3 to derive
   the appropriate DNS translation of the X.400 O/R name and then query
   DNS for the corresponding PX resource record. The obtained record for
   which the PX record must be queried is thus:

      O-top.PRMD-nfc.ADMD-pkz.X42D.de.

   The DNS could contain:

      *.ADMD-pkz.X42D.de.  IN  PX  50  pkz.de.  ADMD-pkz.C-de.

   Assuming that there are not more specific records in DNS, the
   wildcard mechanism will return the RFC1327 'table1' rule in encoded
   format.

6. Administration of mapping information

   The DNS, using the PX RR, will be able to distribute the mapping
   information to all RFC1327 gateways located on the Internet. However,
   not all RFC1327 gateways will be able to use the Internet DNS. It is
   expected that some gateways in a particular management domain will
   conform to one of the following models:

      (a) Table-based, (b) DNS-based, (c) X.500-based

   Table-based management domains will continue to submit and retrieve
   their mapping tables from the International Mapping Table coordinator
   manually or via some automated procedures. Their mapping information
   should be made available in DNS by the appropriate DNS authority
   using the same mechanism already in place for MX records: if a branch
   has not yet in place its own DNS server, some higher authority in the
   DNS tree will provide the service for it. A transition procedure
   similar to the one used to migrate from the 'hosts.txt' tables to DNS
   can be applied also to the deployment phase of this proposal. An
   informational document describing the implementation phase and the
   detailed coordination procedures is expected. The deployment phase
   must also follow the directives produced by the current work on
   RFC1327 mapping authorities, in order to insure consistency in the
   mapping information itself.





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   Another distributed directory service which can distribute the
   RFC1327 mapping information is X.500. The coordination, alignment and
   uniqueness of mapping information between DNS and X.500 is an
   essential fact if it happens to have both systems in place. The ideal
   solution is a dynamic alignment mechanism which transparently makes
   the DNS mapping information available in X.500 and vice versa. Some
   work in this specific field is already being done [see Costa] which
   can result in a global transparent directory service, where the
   information is stored in DNS or in X.500, but is visible completely
   by any of the two systems.

7. Conclusion

   The introduction of the new PX resource record and the definition of
   the X.400 O/R name space in the DNS structure provide a good
   repository for mapping information. The mapping information is stored
   in the DNS tree structure so that it can be easily obtained using the
   DNS distributed name service. At the same time the definition of the
   appropriate DNS space for X.400 O/R names provide a repository where
   to store and distribute some other X.400 MHS information. The use of
   the DNS has many known advantages in storing, managing and updating
   the information. A successful number of tests have been performed
   under the provisional top level domain "X400.IT", and their results
   confirmed the advantages of the method.

   Software to query the DNS and then to convert between the textual
   representation of DNS resource records and the address format defined
   in RFC1327 needs to be developed. This software must also allow a
   smooth implementation and deployment period, eventually taking care
   of the transition phase. A further informational document describing
   operational and implementation of the service is expected.

8. Acknowledgements

   We wish to thanks all those who contributed to the discussion and
   revision of this document: many of their ideas and suggestions
   constitute essential parts of this work. In particular thanks to Jon
   Postel, Paul Mockapetris, Rob Austin and the whole IETF x400ops, RARE
   wg-msg and IETF namedroppers groups. A special mention to Christian
   Huitema for his fundamental contribution to this work.











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9. References

   [CCITT] CCITT SG 5/VII, "Recommendation X.400, Message Handling
       Systems: System Model - Service Elements", October 1988.

   [RFC 1327] Kille, S., "Mapping between X.400(1988)/ISO 10021 and RFC
       822", RFC 1327, March 1992.

   [RFC 1034] Mockapetris, P., "Domain Names - Concepts and Facilities",
       STD 13, RFC 1034, USC/Information Sciences Institute, November
       1987.

   [RFC 1035] Mockapetris, P., "Domain names - Implementation and
       Specification", STD 13, RFC 1035, USC/Information Sciences
       Institute, November 1987.

   [RFC 1033] Lottor, M., "Domain Administrators Operation Guide", RFC
       1033, SRI International, November 1987.

   [Costa] Costa, A., Macedo, J., and V. Freitas, "Accessing and
       Managing DNS Information in the X.500 Directory", Proceeding of
       the 4th Joint European Networking Conference, Trondheim, NO, May
       1993.

   [Houttin] Houttin, J., Hansen, K., and S. Aumont, "Address Mapping
       Functions and Authorities", Internet-DRAFT, May 1993.

10. Security Considerations

   Security issues are not discussed in this memo.





















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11. Authors' Addresses

   Claudio Allocchio
   Sincrotrone Trieste
   Padriciano 99
   I 34012 Trieste
   Italy

   RFC822: [e-mail]
   X.400:  C=it;A=garr;P=Trieste;O=Elettra;
   S=Allocchio;G=Claudio;
   Phone:  [phone]
   Fax:    [phone]


   Antonio Blasco Bonito
   CNUCE - CNR
   Reparto infr. reti
   Viale S. Maria 36
   I 56126 Pisa
   Italy

   RFC822: [e-mail]
   X.400:  C=it;A=garr;P=cnr;O=cnuce;S=bonito;
   Phone:  [phone]
   Fax:    [phone]


   Bruce Cole
   Cisco Systems Inc.
   P.O. Box 3075
   1525 O'Brien Drive
   Menlo Park, CA 94026
   U.S.A.

   RFC822: [e-mail]
   X.400:  C=us;A= ;P=Internet;
   DD.rfc-822=bcole(a)cisco.com;
   Phone:  [phone]
   Fax:    [phone]











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   Silvia Giordano
   Centro Svizzero di
   Calcolo Scientifico
   Via Cantonale
   CH 6928 Manno
   Switzerland

   RFC822: [e-mail]
   X.400:  C=ch;A=arcom;P=switch;O=cscs;
   S=giordano;
   Phone:  [phone]
   Fax:    [phone]


   Robert Hagens
   Advanced Network and Services
   1875 Campus Commons Drive
   Reston, VA 22091
   U.S.A.

   RFC822: [e-mail]
   X.400:  C=us;A= ;P=Internet;
   DD.rfc-822=hagens(a)ans.net;
   Phone:  [phone]



























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