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.


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     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:  [email protected]  or  [email protected]

        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".



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        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:  [email protected]  or  [email protected]

        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:  [email protected]  or  [email protected]

        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,

        [email protected]
        [email protected]




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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.



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  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.


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           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


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     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.




Postel                                                          [Page 7]



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  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.











Postel                                                          [Page 8]


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