Comments on NCP/TCP mail service transition strategy
RFC 773

Document Type RFC - Unknown (October 1980; No errata)
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Network Working Group                                            V. Cerf
Request for Comments: 773                                          DARPA
                                                            October 1980

          COMMENTS ON NCP/TCP MAIL SERVICE TRANSITION STRATEGY

INTRODUCTION

   This memo reviews and expands on the mail service transition plan
   [20].

   The principal aim of the plan is to provide for the orderly support
   of the most commonly used network service (mail) during the period of
   transition from ARPANET to Internet Protocol-based operation.

   The goal of the transition is, at the end, to provide in the internet
   environment service which is equivalent to or better than what has
   been available in the ARPANET environment.  During the interim
   period, when both internet and the older ARPANET-based protocols are
   in use, the goal of the transition is to minimize user impact and, to
   the extent possible, to minimize software development or modification
   required to deal with transitional problems.

   It is assumed that the reader is familiar with both the ARPANET and
   internet protocol hierarchies [1-17].  The internet hierarchy is
   designed to interface to many different packet networks (e.g., packet
   satellite, packet radio, Ethernet, LCS Ring net, X.25 public
   nets, ...), while the ARPANET hierarchy is limited to ARPANET IMPs
   (This is less true of the levels above NCP, but NCP itself is closely
   bound to ARPANET services).

   The objective of the transition plan is to specify means by which the
   ARPANET electronic mail services may be supported across the boundary
   between the purely ARPANET environment and the more general internet
   environment during the period of transition by ARPANET hosts to the
   richer internet world.

ELECTRONIC MESSAGE SERVICES

   DARPA is beginning a new phase of research into automatic electronic
   message handling systems.  Ultimately, it is intended that electronic
   messages incorporate multiple media such as text, facsimile,
   compressed digitized voice, graphics and so on.  Success in this new
   research will require substantial progress in developing multimode
   user interfaces to computer-based services (voice input/output,
   graphics, tablet/light pen, facsimile input/output, video/bit mapped
   displays, ...).

   At the same time, progress must be made towards an environment based
   on internet protocols so as to avoid confining the results of the

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October 1980                                                     RFC 773
Comments on NCP/TCP Mail Service Transition Strategy                    

   multimedia effort to any one network.  As a result, DARPA is planning
   to make several transitions over the next few years, from the
   existing, text-based ARPANET electronic message system to an
   internet-based, multimedia electronic message system.

   This paper addresses only the first of the transitions from NCP-based
   text mail to TCP-based multimedia mail.  The transition to the new
   multimedia mail system [7,19] lies ahead, but need not be planned in
   detail until we have some experience with the basic concepts.  This
   first step only provides for the transition to TCP-based text mail.

   The basic ground rules for transition from ARPANET-based electronic
   mail to internet electronic mail are the following:

      1.  ARPANET mailbox names must continue to work correctly.

      2.  No change required to mail editors which parse message headers
          to compose replies and the like.

      3.  Accommodation of non-ARPANET mailbox designators without
          change to the header parsing and checking mechanisms of mail
          composition programs.

      4.  Automatic forwarding of messages between NCP and TCP
          environments without user intervention.

      5.  During the transition, old style mail mechanisms must still
          work.

ELECTRONIC MESSAGE MECHANISMS

   In order to make progress at all, it has been necessary to postulate
   fairly sophisticated changes to the "mailer" function which accepts
   as input an electronic text message and causes it to be delivered to
   the destination (or to an intermediate forwarder).

   We also posit the existence of special, well-known mail forwarding
   hosts on the ARPANET which are responsible for accepting messages
   from NCP (TCP)-based message senders and forwarding them to
   TCP (NCP)-based message receivers.

   In the ARPANET, electronic messages are transported via special
   procedures of the File Transfer Protocol:  MAIL and MLFL.  The former
   method sends electronic messages via the FTP Telnet command channel

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