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Network Working Group                                          J. PostelRequest for Comments:  805                                           ISI                                                         8 February 1982Computer Mail Meeting NotesIntroduction   A meeting was held on the 11th of January 1982 at USC Information   Sciences Institute to discuss addressing issues in computer mail.   The attendees are listed at the end of this memo.  The major   conclusion reached at the meeting is to extend the   "username@hostname" mailbox format to "username@host.domain", where   the domain itself can be further structured.Overview   The meeting opened with a brief discussion of the objectives of the   meeting and a review of the agenda.      The meeting was called to discuss a few specific issues in text      mail systems for the ARPA Internet.  In particular, issues of      addressing are of major concern as we develop an internet in which      mail relaying is a common occurance.  We need to discuss      alternatives in the design of the mail system to provide high      utility at reasonable cost.  One scheme suggested is to create      "mail domains" which are another level of addressing.  The ad hoc      scheme of source routing, while effective for some cases, is seen      to lead to some problems.  A key test of addressing schemes is the      procedure for sending copies of a reply to a message to the people      who received copies of the original message.  The key reference      documents for the meeting were RFCs 788, 799, and 801.   Jon Postel gave a brief review of the NCP-to-TCP transition plan (RFC801).  The emphasis was on mail, the internet host table, and the   role of a Host Name Server.   The major part of the meeting was devoted to a wide ranging   discussion of the general mailbox identification problem.  In   particular, the notion of a hierarchial structure of name domains was   discussed, and the issues associated with name servers were discussed   including the types of information name servers should provide.Name Domains   One of the interesting ideas that emerged from this discussion was   that the "user@host" model of a mailbox identifier should, inPostel                                                          [Page 1]

Computer Mail Meeting Notes                              8 February 1982   principle, be replaced by a "unique-id@location-id" model, where the   unique-id would be a globally unique id for this mailbox (independent   of location) and the location-id would be advice about where to find   the mailbox.  However, it was recognized that the "user@host" model   was well established and that so many different elaborations of the   "user" field were already in use that there was no point in persuing   this "unique-id" idea at this time.   Several alternatives for the structuring and ordering of the   extensions to the "host" field to make it into a general   "location-id" were discussed.      These basically involved adding more hierarchical name information      either to the right or the left of the @, with the "higher order"      portion rightmost or leftmost.  It was clear that the information      content of all these syntactic alternatives was the same, so that      the one causing least difficulty for existing systems should be      chosen.  Hence it was decided to add all new information on the      right of the @ sign, leaving the "user" field to the left      completely to each system to determine (in particular to avoid the      problem that some systems already use dot (.) internally as part      of user names).   The conclusion in this area was that the current "user@host" mailbox   identifier should be extended to "user@host.domain" where "domain"   could be a hierarchy of domains.      In particular, the "host" field would become a "location" field      and the structure would read (left to right) from the most      specific to the most general.         For example: "Postel@F.ISI.IN" might be the mailbox of Jon         Postel on host F in the ISI complex of the Internet domain.      Formally, inRFC733, the host-indicator definition rule would      become:         host indicator = ( "at" / "@" ) domains         domains = node / node "." domains            Note only one "at" or "@" is allowed, and that the domains            form a hierarchy with the most general in scope last.            And note that the choice of domain names must be            administratively controlled and the highest level domain            names must be globally unique.Postel                                                          [Page 2]

Computer Mail Meeting Notes                              8 February 1982      The hierarchial domain type naming differs from source routing in      that the former gives absolute addressing while the latter gives      relative adressing.Name Servers   The discussion of name servers identified three separate name server   functions: "white pages", "unique-id to location-id", and   "location-id to address".      The "white pages" service is a way of looking up a user by name      and other properties using pattern matching and may return several      data base "hits".  Each hit must have an associated unique-id.      The "unique-id to location-id" service returns the character      string location-id where the unique-id is currently found.      The "location-id to address" service returns a network address      (numeric) corresponding to the location-id.         If the location-id is the name of a host in the current domain         it is clear that the address returned will be the address to         send the mail to, but if the location-id is that of some other         domain then the address returned may be either the address to         send the mail to, or the address of a name server for that         domain, and these two cases must be distinguished.   The conclusion of this discussion was that a location-id to address   name service must be defined soon.  The other types of name servers   were not further discussed, and are not required in the   implemenation.   Another aspect of the name server is returning additional information   besides the address.  In particular, for mail it is important to know   which mail procedures the destination implements (NCP/FTP, TCP/SMTP,   etc.).  Two approaches were discussed: one is coding the information   as service names (e.g., NCP/SMTP), and the other is by reference to   protocol and port numbers (e.g., PROTOCOL=6, PORT=25).  Another   suggestion was that the request ought to be "location-id,service"   (e.g., "ISIF.IN,MAIL") and the response ought to be the location-id,   address, protocol, and port.  A different way of getting this   information was suggested that instead of (or in addition to) having   this information in the name server, one should get this data from   the host itself via some sort of query or "who are you" protocol.   Also discussed was the initial  provision for name service.  It seems   useful to start with a text file that can be accessed via FTP, and to   have both "Telnet-Like" (i.e., based on TCP) and "Datagram" (i.e.,Postel                                                          [Page 3]

Computer Mail Meeting Notes                              8 February 1982   based on UDP) access to a query server.  This might be possible as an   extension of the IEN-116 name server.   Another issue was the central vs. distributed implementation of the   name look up service.  It is recognized that separate servers for   each domain has administrative and maintenance advantages, but that a   central server may be a useful first step.  It is also recognized   that each distinct database should be replicated a few times and be   avialiable from distinct servers for robust and reliable service.   An Example:      Suppose that the new mailbox specification is of the form      USER@HOST.ORG.DOMAIN.         e.g., Postel@F.ISI.IN      A source host sending mail to this address first queries a name      server for the domain IN (giving the whole location "F.ISI.IN").      The result of the query is either (1) the final address of the      destination host (F.ISI), or (2) the address of a name server for      ISI, or (3) the address of a forwarder for ISI.  In cases 1 and 3,      the source host sends the mail to the address returned.  In case      2,  the source host queries the ISI name server and ... (recursive      call to this paragraph).Action Items:RFC 733 Revision      To include the hierarchial host and domain naming procedure, and      to delete the features decommitted at the Computer Mail meeting on      10-JAN-79.      By: Dave Crocker      Due: 15-Feb-82   Host Name Server Description      To specify a way to get name to address conversions and to find      out about services offered.  Also how to get info on domain names.      By: Jon Postel      Due: 15-Feb-82Postel                                                          [Page 4]

Computer Mail Meeting Notes                              8 February 1982   Transition Plan Revision      To include new host and domain names.      By: Jon Postel      Due: 15-Feb-82   SMTP Revision      To include new host and domain names.      By: Jon Postel      Due: Unspecified   Mail System Description Revision      How to do mail systems, including use of SMTP and Host Name      Server.      By: Jon Postel      Due: Unspecified   Conversion of User Programs and Mailer Programs.      Programs have to handle dots in the "host" field.  Many programs      on many hosts will have to be modified to a greater or lesser      extent.  In many cases the modifications should be quite simple.      By: A Cast of Thousands      Due: Unspecified (See the Following Item)   Set a date when it ok to send messages with dots in "host" field.      The must be a date after which it is ok to send host fields with      dots  throughout the ARPANET and Internet world without the      recipients complaining.      By: DARPA (Duane Adams)      Due: 1-Mar-82Postel                                                          [Page 5]

Computer Mail Meeting Notes                              8 February 1982Attendees:   Duane A. Adams    DARPA/IPTO    Adams@ISI           (202) 694-8096   Vint Cerf         DARPA/IPTO    Cerf@ISI            (202) 694-3049   Harry Forsdick    BBN           Forsdick@BBN        (617) 497-3638   Eric Schienbrood  BBN           shienbrood@bbn-unix (617) 497-3756   Bob Thomas        BBN           BThomas@BBND        (617) 497-3483   Bob Fabry         Berkeley      Fabry@Berkeley      (415) 642-2714   Bill Joy          Berkeley      unj@berkeley        (415) 642-7780   Gene Ball         CMU           Ball@CMUA           (412) 578-2569   Anil Agarwal      COMSAT        Agarwal@ISID        (301) 863-6103   David L. Mills    COMSAT        Mills@ISID          (202) 863-6092   Dave Crocker      Univ. Del     DCrocker@Udel       (302) 738-8913   Ray McFarland     DoD           McFarland@ISIA      (301) 796-6290   Dave Lebling      MIT           PDL@MIT-XX          (617) 253-1440   Paul Mockapetris  ISI           Mockapetris@ISIF    (213) 822-1511   Jon Postel        ISI           Postel@ISIF         (213) 822-1511   Carl Sunshine     ISI           Sunshine@ISIF       (213) 822-1511   Mark Crispin      Stanford U.   Admin.MRC@SCORE     (415) 497-1407   Bob Braden        UCL[A]        braden@ISIA      (uk) (01)387-7050   Steve Kille       UCL           UCL-Netwiz@ISIE  (uk) (01)387-7050   Bill Tuck         UCL           UKSAT@ISIE       (uk) (01)387-7050   Marv Solomon      Univ. Wisc    Solomon@UWisc   Ed Taft           Xerox Parc    Taft@Parc-Maxc      (415) 494-4419Postel                                                          [Page 6]