data which can be understood by the requestor.

      3. The CLASS field guides the search for the requested data.

      The last point is central to our approach.  When a query crosses
      protocol boundaries, it must be guided though agents capable of
      performing whatever translation is required.  For example, when a
      mailer wants to identify the location of a mailbox in a portion of
      the domain system that doesn't have a compatible protocol, the
      query must be guided to a name server that can cross the boundary
      itself or form one link in a chain that can span the differences.

      If query and response transport were the only problem, then this
      sort of problem could be dealt with in the name servers
      themselves.  However, the applications that will use domain
      service have similar problems.  For example, mail may need to be
      directed through mail gateways, and the characteristics of one of
      the environments may not permit frequent connectivity between name
      servers in all environments.

      These problems suggest that connectivity will be achieved through
      a variety of measures:

         Translation name servers that act as relays between different
         protocols.

         Translation application servers that translate application
         level transactions.

         Default database entries that route traffic through application
         level forwarders in ways that depend on the class of the
         requestor.

      While this approach seems best given our current understanding of



 

RFC 883                                                    November 1983
                         Domain Names - Implementation and Specification


      the problem, we realize that the approach of using resource data
      that transcends class may be appropriate in future designs or
      applications.  By not defining class to be directly related to
      protocol, network, etc., we feel that such services could be added
      by defining a new "universal" class, while the present use of
      class will provide immediate service.

      This problem requires more thought and experience before solutions
      can be discovered.  The concepts of CLASS, recursive servers and
      other mechanisms are intended as tools for acquiring experience
      and not as final solutions.









































 

RFC 883                                                    November 1983
                         Domain Names - Implementation and Specification