The Remote User Telnet Service

This RFC is the specification of an application protocol. Any host that

implements this application level service must follow this protocol.

This RFC was suggested by Mike Mulligan some months ago when he was at

BBN.

In the ARPANET Host-to-Host Network Control Protocol (NCP) and in the

Internet Transmission Control Protocol (TCP) well known sockets or ports

are used to identify services. The general notion is that there are a

few types of services that are distinct and useful enough to use the NCP

or TCP demultiplexing mechanism directly.

The most common of these is the Server Telnet which generally speaking

defines the network terminal access procedure for a system executive.

That is, making a connection to the server Telnet port actually puts the

caller in contact with the system executive, for example, the TOPS20

EXEC or the Unix Shell.

On some small hosts there may be very limited functionality and no

executive. In such cases it may be useful to designate specific well

known ports for specific applications.

This memo specifies that the specific service of User Telnet may be

accessed (on hosts that choose to provide it) by opening a connection to

port 107 (153 octal). The Telnet Protocol is to be used on the

connection from the originating user to the server.

EXAMPLE: REMOTE TELNET SERVICE ON THE BBN TC68K

The TC68K is a Terminal Concentrator based on the Motorola MC68000

microprocessor. It is used at Bolt Beranek & Newman to provide access

by terminals to the FiberNet, a local area network.

The custom hardware provides one network connection, sixteen RS232

terminal connections, and a programmable timer.

The software is based on the Micro-Operating System (MOS) using the IP,

ICMP, TCP, and Telnet protocols. A user TC-Telnet application provides

an interface to allow the user to use the network to connect to a host,

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                                              Remote User Telnet Service

providing a network virtual terminal. A server Telnet also exists on

the TC68K to serve as a front end for devices that have no awareness of

the net. This is used for remote printer/plotters and computers with no

network software.

The TC68Ks at BBN are distributed about several buildings. To provide

an operational tool to test remote TC68Ks, the TC68K software was

configured to put a user Telnet back to back with a server Telnet. An

operator can open a connection to a remote TC68K and appear to be a

terminal local to that unit. This verifies that the network path

between the two units is operational and provides the operator with

access to statistics that are kept as part of the standard user

TC-Telnet application.

   Operator's         Local                  Remote         Remote
   Terminal   <=TTY=> user      <=FiberNet=> server <=PTY=> user
                      TC-Telnet              Telnet         TC-Telnet

This solution was attractive as the only extra piece of software

necessary for this was the "Pseudo Teletype" (PTY) device driver for

MOS. This "device" appears as a terminal to its application, but what

it is really doing is providing a character stream between two

processes.

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