A User TELNET Description of an Initial Implementation
RFC 206

Document Type RFC - Unknown (August 1971; No errata)
Last updated 2013-03-02
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Network Working Group                                           J. White
Request for Comments: 206                    Computer Research Lab, UCSB
NIC: 7176                                                  9 August 1971

                             A User TELNET
                Description of an Initial Implementation

PREFACE

   The User TELNET described in this document has been implemented
   within UCSB's Online System by Mark Krilanovich and makes teletype-
   compatible time-sharing systems in the Net accessible to Online
   System users.

Contents

                                                                   Page
   I.   Function...................................................  1
   II.  Invoking TELNET............................................  2
   III. The Virtual Teletype.......................................  5
   IV.  Returning to TELNET........................................ 11
   V.   Breaking TELNET Connections................................ 12
   VI.  Abnormal Network Conditions................................ 12

FIGURES

                                                                   Page
   Figure 1.  Network Sites........................................  4
   Figure 2.  TELNET Character Set.................................  6
   Figure 3.  Connect Error Codes.................................. 13
   Figure 4.  Input Error Codes.................................... 13
   Figure 5.  Output Error Codes................................... 14

I.  Function

   This document describes a program whose function is to make an Online
   System terminal _appear_ to any teletype-compatible, time-sharing
   system in the Network _as if it were directly connected to that
   system_.  By invoking this program from his terminal, an OLS user can
   effectively dial up a system at another site and use it as if he were
   a local user of that system.  The program performs the following
   major functions:

      1) it resolves keyboard and display device incompatibilities

      2) performs character set transformations, and

White                                                           [Page 1]
RFC 206                      A User TELNET                   August 1971

      3) makes its presence and that of the Network transparent to the
         user.

   The program which performs these functions is called a _User TELNET_.
   It operates in conjunction with another program called a _Server
   TELNET_ executing at the site whose system is being used.  A Server
   TELNET exists at each site whose system is accessible from the Net.
   Similarly, a User TELNET must exist at a site before users at that
   site have access to remote systems.

   User and Server TELNETs access the Net through their respective NCPs,
   and operate under a Network-standard protocol which specifies the
   hand-shaking procedure by which the two parties connect themselves to
   one another, as well as the format of data sent over a pair of
   Network connections established between them.  A User TELNET makes
   such protocol considerations transparent to its users.

   The TELNET protocol is based upon the notion of a virtual teletype,
   employing a 7-bit ASCII character set.  The primary function of a
   User TELNET, then, is to provide the means by which its users can
   'hit' all the keys on that virtual teletype.  If the user's keyboard
   happens in fact to actually be a teletype, then the mapping procedure
   is a very simple one.  However, in UCSB's case, where a user's input
   device is an OLS keyboard (a device very different from a teletype),
   the mapping is more complex.

   The primary function of a Server TELNET is to map the keys on the
   virtual teletype into that set of keys _its_ local users can push on
   _their_ keyboards.  Again, if those keyboards are teletypes, the
   mapping done by the Server TELNET is straightforward.  In other
   cases, the task may be very complex.

   A similar set of mappings transforms ouput generated by the remote
   system into a form displayable on the user's output device (in UCSB's
   case, this device is normally a storage scope).

II.  Invoking TELNET

   This and succeeding sections describe a preliminary version of a User
   TELNET (hereafter referred to simply as TELNET) currently implemented
   within the Online System.  This initial implementation does not
   provide all of the services that a final version must provide, nor
   does it provide all the conveniences that the next version will
   offer.  It's a first pass which will be upgraded in the near future.

White                                                           [Page 2]
RFC 206                      A User TELNET                   August 1971

   TELNET is accessible from NET, a subsystem (like MOLSF and COL) of
   OLS.  A user is by default prohibited from loading NET.  To have
   access to NET enabled fro his user number, a user need only contact
   the Computer Center.  Assuming the foregoing, Net can be loaded with
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