NCP/TCP transition plan
RFC 801

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Network Working Group                                          J. Postel
Request for Comments: 801                                            ISI
                                                           November 1981

                        NCP/TCP TRANSITION PLAN

Introduction
------------

   ARPA sponsored research on computer networks led to the development
   of the ARPANET.  The installation of the ARPANET began in September
   1969, and regular operational use was underway by 1971.  The ARPANET
   has been an operational service for at least 10 years.  Even while it
   has provided a reliable service in support of a variety of computer
   research activities, it has itself been a subject of continuing
   research, and has evolved significantly during that time.

   In the past several years ARPA has sponsored additional research on
   computer networks, principally networks based on different underlying
   communication techniques, in particular, digital packet broadcast
   radio and satellite networks.  Also, in the ARPA community there has
   been significant work on local networks.

   It was clear from the start of this research on other networks that
   the base host-to-host protocol used in the ARPANET was inadequate for
   use in these networks.  In 1973 work was initiated on a host-to-host
   protocol for use across all these networks.  The result of this long
   effort is the Internet Protocol (IP) and the Transmission Control
   Protocol (TCP).

   These protocols allow all hosts in the interconnected set of these
   networks to share a common interprocess communication environment.
   The collection of interconnected networks is called the ARPA Internet
   (sometimes called the "Catenet").

   The Department of Defense has recently adopted the internet concept
   and the IP and TCP protocols in particular as DoD wide standards for
   all DoD packet networks, and will be transitioning to this
   architecture over the next several years.  All new DoD packet
   networks will be using these protocols exclusively.

   The time has come to put these protocols into use in the operational
   ARPANET, and extend the logical connectivity of the ARPANET hosts to
   include hosts in other networks participating in the ARPA Internet.

   As with all new systems, there will be some aspects which are not as
   robust and efficient as we would like (just as with the initial
   ARPANET).  But with your help, these problems can be solved and we

Postel                                                          [Page 1]



RFC 801                                                    November 1981
                                                 NCP/TCP Transition Plan

   can move into an environment with significantly broader communication
   services.

Discussion
----------

   The implementation of IP/TCP on several hosts has already been
   completed, and the use of some services is underway.  It is urgent
   that the implementation of of IP/TCP be begun on all other ARPANET
   hosts as soon as possible and no later than 1 January 1982 in any
   case.  Any new host connected to the ARPANET should only implement
   IP/TCP and TCP-based services.  Several important implementation
   issues are discussed in the last section of this memo.

   Because all hosts can not be converted to TCP simultaneously, and
   some will implement only IP/TCP, it will be necessary to provide
   temporarily for communication between NCP-only hosts and TCP-only
   hosts.  To do this certain hosts which implement both NCP and IP/TCP
   will be designated as relay hosts.  These relay hosts will support
   Telnet, FTP, and Mail services on both NCP and TCP.  These relay
   services will be provided  beginning in November 1981, and will be
   fully in place in January 1982.

   Initially there will be many NCP-only hosts and a few TCP-only hosts,
   and the load on the relay hosts will be relatively light.  As time
   goes by, and the conversion progresses, there will be more TCP
   capable hosts, and fewer NCP-only hosts, plus new TCP-only hosts.
   But, presumably most hosts that are now NCP-only will implement
   IP/TCP in addition to their NCP and become "dual protocol" hosts.
   So, while the load on the relay hosts will rise, it will not be a
   substantial portion of the total traffic.

   The next section expands on this plan, and the following section
   gives some milestones in the transition process.  The last section
   lists the key documents describing the new protocols and services.
   Appendices present scenarios for use of the relay services.

The General Plan
----------------

   The goal is to make a complete switch over from the NCP to IP/TCP by
   1 January 1983.

      It is the task of each host organization to implement IP/TCP for
      its own hosts.  This implementation task must begin by
      1 January 1982.

Postel                                                          [Page 2]



RFC 801                                                    November 1981