Comments on NCP/TCP mail service transition strategy
RFC - Unknown
(October 1980; No errata)
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RFC 773 (Unknown)
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Network Working Group V. Cerf
Request for Comments: 773 DARPA
COMMENTS ON NCP/TCP MAIL SERVICE TRANSITION STRATEGY
This memo reviews and expands on the mail service transition plan
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
At the same time, progress must be made towards an environment based
on internet protocols so as to avoid confining the results of the
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
4. Automatic forwarding of messages between NCP and TCP
environments without user intervention.
5. During the transition, old style mail mechanisms must still
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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