Network subsystem for time sharing hosts
RFC 15

Document Type RFC - Unknown (September 1969; No errata)
Last updated 2014-05-06
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Network Working Group                                   C. Stephen Carr
Request for Comments: 15                                           UTAH
                                                      25 September 1969

                Network Subsystem for Time Sharing Hosts


   A set of network primitives has been defined (Network Working Group
   Note 11) for inclusion in the monitor systems of the respective
   HOSTS.  These primitives are at the level of system calls: SPOP's or
   BRS's on the 940; UUO's on the PDP-10.  Presumably these UUO's are
   accessible to all user programs when executing for users whose status
   bits allow network access.

   In addition to user program access, a convenient means for direct
   network access from the terminal is desirable.  A sub-system called
   "Telnet" is proposed which is a shell program around the network
   system primitives, allowing a teletype or similar terminal at a
   remote host to function as a teletype at the serving host.

System Primitives

   G. Deloche of U.C.L.A. has documented a proposed set of basic network
   primitives for inclusion in the operating systems of the respective
   HOSTs (NWG Note:  11).  The primitives are:

      Open primary connection

      Open auxiliary connection

      Transmit over connection

      Close connection.

   The details  and terminology are defined by Deloche and others in
   previous memos.  The primitives are system calls, available to
   programmers, and are most likely a part of the resident monitor,
   rather than the swappable executive.

Basic Terminal Access

   In addition to user programming access, it is desirable to have a
   subsystem program at each HOST which makes the network immediately
   accessible from the teletype without special programming.  Subsystems
   are commonly used system components such as text editors, compilers
   and interpreters.  The first network-related subsystem should allow

Carr                                                            [Page 1]
RFC 15          Network Subsystem for Time Sharing Hosts  September 1969

   users at HOST A to connect to HOST B and appear as a regular terminal
   user to HOST B.  It is expected that more sophisticated subsystems
   will be developed in time, but this basic one will render the early
   net immediately useful.

    Terminal        ______                                 ________
    _________      |      |     ______          ______    |        |
   |         |     | USER |    |      |        |      |   |SERVING |
   |         |-----| HOST |----|      |---//---|      |---| HOST   |
   |_________|     |  A   |    |      |        |      |   |  B     |
                   |______|    |______|        |______|   |________|
                  University                               Stanford
                   of Utah                                 Research

   Figure 1:  User accesses distant serving HOST via shunt
              subsystem in his own Host computer.

Simple Dialogue -- PDP-10 to 940

   A user at Utah is sitting at a teletype dialed into the University's
   dual PDP-10's.  He wishes to operate the CAL sub-system on the 940 at
   SRI in Menlo Park, California.

   .LOGIN<CR>                          PDP-10 login

   .R TELNET<CR>                       The PDP-10 run command
    ------------                       is issued to call and start
                                       the TELNET subsystem.
   *ESCAPE CHARACTER IS #<CR>          The user indicates an escape
    -------------------------          character which TELNET
                                       will watch for in subsequent
                                       input from the user.

   *CONNECT TO SRI<CR>                 The TELNET subsystem will make
    ------------------                 the appropriate system call
                                       (UUO) to establish a primary
                                       connection.  The connection
                                       will be established, provided:
                                       1.  SRI is willing to accept
                                       another foreign user;
                                       2.  The UTAH user is cleared
                                       for network access at UTAH.
                                       This is determined by a
                                       status word kept in the PDP-10

Carr                                                            [Page 2]
RFC 15          Network Subsystem for Time Sharing Hosts  September 1969

                                       monitor for each user.

   @LOGIN CARR.                        The user logs in SRI.
    --    -----

   Characters typed on the user's teletype are transmitted unaltered
   through the PDP-10 (user Host) and on to the 940 (serving HOST.)
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