Network Working Group J. Postel
Request for Comments: 818 ISI
November 1982
Page 1
The Remote User Telnet Service
- This RFC is the specification of an application protocol. Any host that
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- implements this application level service must follow this protocol.
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- This RFC was suggested by Mike Mulligan some months ago when he was at
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- BBN.
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- In the ARPANET Host-to-Host Network Control Protocol (NCP) and in the
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- Internet Transmission Control Protocol (TCP) well known sockets or ports
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- are used to identify services. The general notion is that there are a
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- few types of services that are distinct and useful enough to use the NCP
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- or TCP demultiplexing mechanism directly.
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- The most common of these is the Server Telnet which generally speaking
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- defines the network terminal access procedure for a system executive.
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- That is, making a connection to the server Telnet port actually puts the
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- caller in contact with the system executive, for example, the TOPS20
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- EXEC or the Unix Shell.
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- On some small hosts there may be very limited functionality and no
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- executive. In such cases it may be useful to designate specific well
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- known ports for specific applications.
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- This memo specifies that the specific service of User Telnet may be
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- accessed (on hosts that choose to provide it) by opening a connection to
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- port 107 (153 octal). The Telnet Protocol is to be used on the
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- connection from the originating user to the server.
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- EXAMPLE: REMOTE TELNET SERVICE ON THE BBN TC68K
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- The TC68K is a Terminal Concentrator based on the Motorola MC68000
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- microprocessor. It is used at Bolt Beranek & Newman to provide access
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- by terminals to the FiberNet, a local area network.
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- The custom hardware provides one network connection, sixteen RS232
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- terminal connections, and a programmable timer.
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- The software is based on the Micro-Operating System (MOS) using the IP,
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- ICMP, TCP, and Telnet protocols. A user TC-Telnet application provides
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- an interface to allow the user to use the network to connect to a host,
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- Page 2
Remote User Telnet Service
- providing a network virtual terminal. A server Telnet also exists on
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- the TC68K to serve as a front end for devices that have no awareness of
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- the net. This is used for remote printer/plotters and computers with no
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- network software.
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- The TC68Ks at BBN are distributed about several buildings. To provide
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- an operational tool to test remote TC68Ks, the TC68K software was
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- configured to put a user Telnet back to back with a server Telnet. An
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- operator can open a connection to a remote TC68K and appear to be a
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- terminal local to that unit. This verifies that the network path
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- between the two units is operational and provides the operator with
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- access to statistics that are kept as part of the standard user
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- TC-Telnet application.
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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
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- necessary for this was the "Pseudo Teletype" (PTY) device driver for
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- MOS. This "device" appears as a terminal to its application, but what
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- it is really doing is providing a character stream between two
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- processes.
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