rfc897.txt

RFC 相关的技术文档

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:  [e-mail]  or  [e-mail]

         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:  [e-mail]  or  [e-mail]

         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:  [e-mail]  or  [e-mail]

         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,

         [e-mail]
         [e-mail]




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]