COLORS, FLAVORS, and TRUTH.  The FLAVORS domain has one immediate
      subdomain named NATURAL.FLAVORS.  All of the leaves are also



 

RFC 882                                                    November 1983
                                  Domain Names - Concepts and Facilities


      domains.  This domain tree has the names " "(the root), COLORS,
      RED.COLORS, BLUE.COLORS, GREEN.COLORS, FLAVORS, NATURAL.FLAVORS,
      CHOCOLATE.NATURAL.FLAVORS, VANILLA.NATURAL.FLAVORS,
      STRAWBERRY.NATURAL.FLAVORS, and TRUTH.  If we wished to add a new
      domain of ARTIFICIAL under FLAVORS, FLAVORS would typically be the
      administrative entity that would decide; if we wished to create
      CHIP and MOCHA names under CHOCOLATE, CHOCOLATE.NATURAL.FLAVORS
      would typically be the appropriate administrative entity.

   Resource set information

      A domain name identifies a set of resource information.  The set
      of resource information associated with a particular name is
      composed of separate resource records (RRs).

      Each resource record has the following major components:

         The domain name which identifies resource set that holds this
         record, and hence the "owner" of the information.  For example,
         a RR that specifies a host address has a domain name the
         specifies the host having that address.  Thus F.ISI.ARPA might
         be the owner of a RR which specified an address field of
         10.2.0.52.  Since name servers typically store their resource
         information in tree structures paralleling the organization of
         the domain space, this information can usually be stored
         implicitly in the database; however it is always included in
         each resource record carried in a message.

         Other information used to manage the RR, such as length fields,
         timeouts, etc.  This information is omitted in much of this
         memo, but is discussed in [14].

         A resource type field that specifies the type of the resource
         in this resource record.  Types refer to abstract resources
         such as host addresses or mail delivery agents.  The type field
         is two octets long and uses an encoding that is standard
         throughout the domain name system.

         A class field identifies the format of the resource data, such
         as the ARPA Internet format (IN) or the Computer Science
         Network format (CSNET), for certain RR types (such as address
         data).  Note that while the class may separate different
         protocol families, networks, etc. it does not do so in all
         cases.  For example, the IN class uses 32 bit IP addresses
         exclusively, but the CSNET class uses 32 bit IP addresses, X.25
         addresses, and phone numbers.  Thus the class field should be
         used as a guide for interpreting the resource data.  The class
         field is two octets long and uses an encoding that is standard
         throughout the domain name system.



 

RFC 882                                                    November 1983
                                  Domain Names - Concepts and Facilities


         Resource data that describes the resource.  The format of this
         data can be determined given the type and class fields, but
         always starts with a two octet length field that allows a name
         server or resolver to determine the boundaries of the resource
         data in any transaction, even if it cannot "understand" the
         resource data itself.  Thus name servers and resolvers can hold
         and pass on records which they cannot interpret.  The format of
         the internal data is restricted only by the maximum length of
         65535 octets; for example the host address record might specify
         a fixed 32 bit number for one class, and a variable length list
         of addresses in another class.

      While the class field in effect partitions the resource data in
      the domain name system into separate parallel sections according
      to class, services can span class boundaries if they use
      compatible resource data formats.  For example, the domain name
      system uses compatible formats for structure information, and the
      mail data decouples mail agent identification from details of how
      to contact the agent (e.g. host addresses).

      This memo uses the following types in its examples:

         A     - the host address associated with the domain name

         MF    - identifies a mail forwarder for the domain

         MD    - identifies a mail destination for the domain

         NS    - the authoritative name server for the domain

         SOA   - identifies the start of a zone of authority