Network Working Group                                         Jon Postel
Request for Comments: 897                                            ISI
                                                           February 1984
Updates:  RFC 881

               Domain Name System Implementation Schedule


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 a partial update
   of RFC 881.  This is an official policy statement of the ICCB and the
   DARPA.

   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

   Simple Names

      Hosts in the ARPA research and DDN operational communities are
      currently 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

   Tables

      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.

   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,

         OBERST%EDUCOM.MAILNET@MIT-MULTICS
         EDMISTON.CIC@CSNET-RELAY

The Future Situation

   Hierarchical Names

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

         For example:  F.ISI.USC.ARPA

   Servers

      Every host in the Internet will be 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 will be done by
      interacting with a service.  There will be a number of servers
      that each hold a portion of the name to address information.

      The maintenance of the translation data will be subdivided and
      distributed.

   There are several stages of implementation for the servers and
   several levels of development for use of the domain style names.

      First, there is the simple substitution of the domain style names
      for the current host names, and the subdivision of these into
      several domains.  At this stage all domain style names directly
      translate to host addresses and all domain style names have two
      components.

         For example:  USC-ISIF.ARPA  or  USC-ISIA.DDN

         and:  Postel@USC-ISIF.ARPA  or  Kahn@USC-ISIA.DDN

         Here we expect that "USC-ISIF.ARPA" is the name of an Internet
         host and that we can send mail for "Postel" to the SMTP port on
         that host.  It may be that some backward host can still fake it
         by ignoring the ".ARPA" and looking up an address for
         "USC-ISIF".

         Using the domain name servers (but not the tables) mail
         forwarding may be supported.  A domain name server query can
         say "I want to send mail to ABCDEF.ARPA".  The response might
         be "to send mail to ABCDEF.ARPA send it to the mail relay
         GHIJKL.ARPA at address 123.123.123.123".

      Second, there is an extension to more name components.

         For example:  F.ISI.USC.ARPA  or  A.USC-ISI.DDN

         and:  Postel@F.ISI.USC.ARPA  or  Kahn@A.USC-ISI.DDN

         Here we expect that "F.ISI.USC.ARPA" is the name of an Internet
         host and that we can send mail for "Postel" to the SMTP port on
         that host.  It is unlikely that a backward host can hack this
         at all.

      Third, there is an extension to domain style names that may
      represent only organizations or administrative entities.  Finding
      a host that represents such entities may require a level of
      indirection in the search.

         For example:  USC-ISI.ARPA  or  ARPA.DDN

         and:  Postel@USC-ISI.ARPA  or  Kahn@ARPA.DDN

         Here we don't count on "USC-ISI.ARPA" being the name of an
         Internet host.  When we want to send mail to "Postel" we ask
         the domain name server about sending mail to "USC-ISI.ARPA".
         The server will tell us the name (and address) of a real
         Internet host that handles mail on this organizations behalf,
         for example, "F.USC-ISI.ARPA = 10.2.0.52". We then send mail
         for "Postel" to the SMTP port on F.USC-ISI.ARPA.

   Interface to the World

      Mail will continue to move between the Internet and other
      "systems".  This may be done by designating some sort of
      "other-system" representative organization in the domain server
      data bases that can indirect mail to a mail-relay host.

      For example,

         OBERST@EDUCOM.MAILNET
         EDMISTON@CIC.CSNET

The Transition Situation

   Actually, the situation is a bit more complicated, of course.  A
   number of hosts are already using domain style names under the
   constraint that their domain style name is exactly their old style
   name with the string ".ARPA" appended.  The first transition step is
   to have all hosts do this, and then to eliminate the user of old
   style names altogether.

   Please note carefully that two types of changes are being made:

      One is a change in the support mechanism for translating a host
      name to an internet address,

         that is from using local copies of a full centrally maintained
         table to dynamically accessing a distributed set of servers
         each posesing a portion of a data base maintained in a
         distributed fashion.

      The other is a change in the host names themselves,

         from a flat global space of unstructured strings to a
         hierarchical structure of names.

   There are four steps to the transition plan.

      First, change from old names to domain style names.

         host-name --> host-name.ARPA

      Second, one domain to a few domains.

         host-name.ARPA --> host-name.ARPA and host-name.DDN

      Third, change from using central tables to using name servers.

      Fourth, allow many domains.

   There are two communities that are taking slightly different courses
   in this transition.  The ARPA research community is making the full
   transition.  The DDN operational community is making the change in
   naming on the same schedule, but is not requiring hosts in the DDN
   operational community make the change to using servers at the same
   time (they can if they want to).  The DDN PMO will establish a
   schedule for that change at a later time.  The NIC will maintain a
   central table of all DDN operational hosts.

   Interface to the World

      The interchange of mail with "other-systems" will have to continue
      pretty much as it does now (except that RELAY-HOST will become
      RELAY-HOST.ARPA) until organization names can be used.  Then
      representative organizations can be designated for each
      "other-system" in the domain server data bases that will then
      indirectly specify a mail-relay host.

Policy Statement

   The names of hosts will be changed to domain style names.  Hosts will
   begin to use domain style names on 14-Mar-84 and the use of old style
   names will be completely phased out before 2-May-84.

   This applies to both the ARPA research hosts and the DDN operational
   hosts.

Implication

   All Hosts Change Names

      The impact of introducing the domain style names is that all hosts
      change their names at least once.  Hosts that move to new domains
      or subdomains may change their names several times.

      Hosts have an official (or primary) name and possibly several
      nicknames.  When mail is sent from a host, the official name is
      used in the mail header address fields.

      Suppose, that in the old days before domains were thought of, a
      host changed its name.  What is the impact on users of changing
      the name of a host?  Suppose one host changed its name from FOO to
      BAR.

         Mail

            Mail that was sent before the name was changed can not be
            answered using mail program commands that automatically fill
            in the return address.  While it may be possible to use
            special tricks to fix up the "From" or the "To" users
            addresses, the "Cc" addresses are very difficult to correct.

            Mail that was sent to JOE@ABC from FRED@FOO can not be
            answered unless the change of name is known to the user or
            the mail program an ABC and the host name BAR substituted
            for FOO.

            Mail that is sent to JOE@ABC from SAM@DEF with a cc to
            FRED@FOO can not be answered easily.

         Mailing Lists

            Any mailing lists that have mailboxes on the host that
            changed names will now have incorrect entries.

      The point is that while the host that changed names may be able to
      use special tricks for a while to fix things up for the users, it
      is difficult for other hosts to do this.

      A general trick is to make the old name a nickname for the host
      for some period of time.

      The introduction of domain style names means that all hosts change
      their names essentially at the same time.

         For example, USC-ISIF changes to USC-ISIF.ARPA

      To lessen the resulting havoc, the initial set of new names has a
      fixed relationship to the old names.  The first set of domain
      style names is exactly the old names with the domain name "ARPA"
      appended.  That is, if a hosts old name was "HOST-NAME", then its
      new name is "HOST-NAME.ARPA".

      To further lessen the havoc, there will be a period of time when
      both the old and the new names are allowed.  That is, the old
      names will be nicknames for a while.

   Primary Names

      In to old style names, host have an official or primary names and
      may have several nicknames.  For example,

         Primary Name             Nicknames

         USC-ISIF                 ISIF

         ADA-VAX                  ISI-VAXB  AJPO  VAXB

      In any case, the data base in such than given any of the names for
      a host one can find the address, and given the address one can
      find the primary name.

      In the new domain style name system this property must be
      maintained.  That is, given the Internet address of a host one

      must be able to find the primary name of that host.  This calls
      for careful management of the distributed database by those in
      charge of the domains and subdomains.

The Time Table

   -- Nov 83  Plan and Schedule

      At this point the overall plan for the implementation of domain
      style names and name servers, and a schedule of events was
      published (RFC-881).  Also the draft design and specification for
      the protocol and data base were published (RFC-882, RFC-883).

   -- Nov 83  Initial Domain Style Host Name Table

      At this point a version of the host table which includes the
      domain style names is made available (DHOSTS.TXT).

   -- Feb 84  Domain Requirements Specification

      At this point the requirements for establishing a new domain are
      published as an RFC.

   14 Mar 84  Begin using Domain Style Names

      At this point all hosts should start using their domain style
      names as their official and primary names.  The standard table of
      host names contains domain style names as the official and primary
      name (DHOSTS.TXT becomes HOSTS.TXT).

   04 Apr 84  Server for ARPA Domain

      At this point several domain name servers are in operation to
      supply host name to internet address translations, one of these
      servers is at the NIC.

   04 Apr 84  Domain Table

      At this point a master table of top level domain names and their
      associated servers is established at the NIC.

   02 May 84  Stop using old style Names

      At this point the use of old style names must be completely phased
      out.

   02 May 84  Certain New Domains

      At this point a few new domains may be established, in particular
      the DDN domain.

   06 Jun 84  General & Multilevel Domains

      At this point additional new domains may be established, if they
      meet the requirements.  Domain style names may have more than two
      segments.

   18 Jul 84  Organizational Domains

      Domain style names may identify organizations.  Finding an address
      for a host may involve a level of indirection.

   05 Sep 84  Decommission Host Table

      At this point the master host table maintained by the NIC need no
      longer be complete for the ARPA research community.  A full table
      of the DDN operational hosts will be maintained by the NIC.

   03 Oct 84  DDN Plan for Domains Name Service

      At this point the DDN PMO will establish a plan for the future
      support of name to address translations in the DDN community.

References

   [1]  Postel, J., "The Domain Names Plan and Schedule", RFC-881, USC
        Information Sciences Institute, November 1983.

   [2]  Mockapetris, P., "Domain Names - Concepts and Facilities",
        RFC-882, USC Information Sciences Institute, November 1983.

   [3]  Mockapetris, P., "Domain Names - Implementation and
        Specification", RFC-883, USC Information Sciences Institute,
        November 1983.