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rfc:rfc897

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.

Postel [Page 1]

RFC 897 February 1984 Domain Implementation Schedule

    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".

Postel [Page 2]

RFC 897 February 1984 Domain Implementation Schedule

       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

Postel [Page 3]

RFC 897 February 1984 Domain Implementation Schedule

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.

Postel [Page 4]

RFC 897 February 1984 Domain Implementation Schedule

 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.

Postel [Page 5]

RFC 897 February 1984 Domain Implementation Schedule

          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

Postel [Page 6]

RFC 897 February 1984 Domain Implementation Schedule

    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

  1. - 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).
  1. - 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).
  1. - 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.

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RFC 897 February 1984 Domain Implementation Schedule

 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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