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Network Working Group                                         Jon PostelRequest for Comments: 897                                            ISI                                                           February 1984Updates:  RFC881               Domain Name System Implementation ScheduleStatus 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   ofRFC 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 1984Domain Implementation Schedule      For example,         OBERST%EDUCOM.MAILNET@MIT-MULTICS         EDMISTON.CIC@CSNET-RELAYThe 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 1984Domain 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.CSNETPostel                                                          [Page 3]

RFC 897                                                    February 1984Domain Implementation ScheduleThe 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 1984Domain 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 1984Domain 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 onePostel                                                          [Page 6]

RFC 897                                                    February 1984Domain 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   -- 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]

RFC 897                                                    February 1984Domain 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]