RFC805

Network Working Group J. Postel Request for Comments: 805 ISI

                                                     8 February 1982

                  Computer Mail Meeting Notes

Introduction

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 "[email protected]", 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 (RFC 801). 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, in

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 "[email protected]" 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: "[email protected]" might be the mailbox of Jon
     Postel on host F in the ISI complex of the Internet domain.

  Formally, in RFC733, 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.

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.,

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
  [email protected].

     e.g., [email protected]

  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-82

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-82

Computer Mail Meeting Notes 8 February 1982

Attendees:

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) 494-4419