RFC 818

Title block tea 🎀✨

Number: RFC 818 Author: J. Postel, ISI Date: November 1982 Series: Network Working Group Category, obsoletes, updates: this copy doesn't list any of those, so there's nothing to report on that front 🫶

The Remote User Telnet Service 🌸

okay bestie, so this doc is an application protocol spec 💅 and the rule is that any host that runs this application-level service has to follow the protocol. no skipping steps, no cap 😤

Mike Mulligan suggested this RFC a while back, when he was still at BBN 💜

The vibe of the ports 🦋

So in the ARPANET Host-to-Host Network Control Protocol (NCP) and the Internet Transmission Control Protocol (TCP), we use well known sockets (ports) to tell services apart. The big idea is that there are a few services distinct and useful enough to get their own demultiplexing slot in NCP or TCP directly. it's giving organization, it's giving clean 🧚

The most famous one is the Server Telnet. Generally speaking, it's the network terminal access procedure for a system executive. So when you connect to the server Telnet port, you're literally put in touch with the system executive, like the TOPS20 EXEC or the Unix Shell. main character energy 👑

But on some tiny hosts there's barely any functionality and no executive at all 🥺 In that case it can be useful to assign specific well known ports to specific applications instead.

This memo says the specific service of User Telnet can be accessed (on hosts that choose to offer it) by opening a connection to port 107 (153 octal) 🍓 The Telnet Protocol is used on that connection, from the originating user to the server. ✨

EXAMPLE: REMOTE TELNET SERVICE ON THE BBN TC68K 🎀

Okay this one is so cute, I'm obsessed 😭

The TC68K is a Terminal Concentrator built on the Motorola MC68000 microprocessor. Bolt Beranek & Newman used it to let terminals reach the FiberNet, their local area network 🌈

The custom hardware gives you one network connection, sixteen RS232 terminal connections, and a programmable timer. literally a whole little hub 💖

The software runs on the Micro-Operating System (MOS) and uses the IP, ICMP, TCP, and Telnet protocols. A user TC-Telnet application gives you an interface to hop from the network onto a host, and it provides a network virtual terminal. There's also a server Telnet on the TC68K that acts as a front end for devices that have no clue about the net. That's used for remote printer/plotters and computers with no network software at all 🖨️💅

The TC68Ks at BBN are spread across several buildings. To make a handy tool for testing remote TC68Ks, the TC68K software was set up to put a user Telnet back to back with a server Telnet 🫶 An operator can open a connection to a remote TC68K and feel like they're a terminal sitting right next to that unit. This checks that the network path between the two units is working, and it gives the operator access to statistics kept as part of the standard user TC-Telnet application. it's a whole diagnostic moment ✨

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

This was the slay solution because the only extra piece of software it needed was the "Pseudo Teletype" (PTY) device driver for MOS 💜 The PTY "device" looks like a terminal to its application, but what it's really doing is providing a character stream between two processes. iykyk, it's a sneaky little trick and I love it 🦋🌸