Domain name system implementation schedule - revised
RFC 921

Document Type RFC - Unknown (October 1984; No errata)
Updates RFC 897
Last updated 2013-03-02
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Network Working Group                                         Jon Postel
Request for Comments: 921                                            ISI
                                                            October 1984
Updates:  RFC 897, RFC 881

          Domain Name System Implementation Schedule - Revised

Status of this Memo

   This memo is a policy statement on the implementation of the Domain
   Style Naming System in the Internet.  This memo is an update of
   RFC-881, and RFC-897.  This is an official policy statement of the
   IAB and the DARPA.  Distribution of this memo is unlimited.

   The intent of this memo is to detail the schedule for the
   implementation for the Domain Style Naming System.  The explanation
   of how this system works is to be found in the references.

The Current Situation

   There are three aspects to the domain style naming system, (1) the
   names themselves, (2) the method of translating names to addresses,
   and (3) the relationship between the Internet and the rest of the


      The names are being changed from simple names, or globally unique
      strings, to structured names, where each component name is unique
      only with respect to the superior component name.

      Simple Names

         Until recently, hosts in the DARPA research and DDN operational
         communities were assigned names in a flat or global name space
         of character strings.  There are some limits on these names.
         They must start with a letter, end with a letter or digit and
         have only letters or digits or hyphen as interior characters.
         Case is not significant.

            For example:  USC-ISIF

      Hierarchical Names

         Because of the growth of the Internet, structured names (or
         domain style names) have been introduced.  Each element of the
         structured name will be a character string (with the same
         constraints that previously applied to the simple names).  The

Postel                                                          [Page 1]

RFC 921                                                     October 1984
Domain Implementation Schedule - Revised

         elements (or components) of the structured names are separated
         with periods, and the elements are written from the most
         specific on the left to the most general on the right.

            For example:  USC-ISIF.ARPA

      The Initial and Temporary Domain

         The introduction of these hierarchical names has been very
         limited.  Every current name in this new system has the form
         "old-simple-name.ARPA".  That is, the all the hosts are in a
         domain called "ARPA".  This is a temporary situation.  The
         current intention is for the ARPA domain to cease to exist.
         This means that all hosts will change their names as the domain
         style names come into full use.

   Name to Address Lookup

      Every host in the Internet is expected to have a way of
      translating the name of any other host into its Internet address.

      By and large, the name to address translation is done by looking
      up the information in a table of all hosts.

      The maintenance of this table is centralized at the Network
      Information Center (NIC).  Each host is expected to obtain a
      current copy of the table on a timely basis.  This table is called
      "HOSTS.TXT" [8] and is normally accessed via the Hostnames
      Server [9].

   Interface to the World

      A great deal of mail moves between the Internet and other
      "systems" that somehow transport mail among computers.  This is
      currently done by hiding some sort of "other-system" addressing
      information in the local-part of the mail address and using a
      mail-relay host in the host-part of the mailbox.

      For example,


Postel                                                          [Page 2]

RFC 921                                                     October 1984
Domain Implementation Schedule - Revised

The Future Situation


      Hierarchical Names

         The use of the hierarchical names will be greatly expanded
         according to the rules established in the "Domain Requirements"
         memo (RFC-920) [5].

            For example:  F.ISI.USC.EDU

      There are several levels of development for use of the domain
      style names.

      First, there is the current simple substitution of the domain
      style names for the old style host names.  At this stage all
      domain style names directly translate to host addresses (using the
      NIC tables) and all domain style names have two components.  The
      mail system uses addresses of the form "local-part@host", where
      host is a domain style host name.

         For example:  USC-ISIF.ARPA  and  Postel@USC-ISIF.ARPA

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