Host Ports
An approved scheme for connecting host computers to the ARPANET through host ports
Chipman, S.G., "Host Ports", RFC 667, DOI 10.17487/RFC0667, December 1974, <https://www.rfc-editor.org/info/rfc667>.
@misc{rfc667,
series = {Request for Comments},
number = 667,
howpublished = {RFC 667},
publisher = {RFC Editor},
doi = {10.17487/RFC0667},
url = {https://www.rfc-editor.org/info/rfc667},
author = {S.G. Chipman},
title = {{Host Ports}},
pagetotal = 2,
year = 1974,
month = dec,
} RFC text
Network Working Group S. Chipman
Request for Comments: 667 BBN-TENEX
NIC: 31422 December 1974
Host Ports
The following is the approved scheme to connect our computers to the
network. This configuration will become effective December 18, 1974.
__________________
| PDP-11 |
| SPEECH FRONT END |________
| 50.=62(8) | __|_________
|__________________| | |
__________________ | IMP-50 |________\ NCC-TIP
| PDP-10 | |____________| /
| SYSTEM D |________| | |
| 114.=162(8) | | |
|__________________| | |________________________
__________________ | |
| PDP-10 | | |
| SYSTEM A |________ | |
| 197.=305(8) | | | |
|__________________| | | |
__________________ __|___|_____ |
| PDP-11 | | | |
| LPT |_____| IMP-5 |________\ CCA |
| 69.=105(8) | |____________| / |
|__________________| | | |
__________________ | | |
| PDP-11 | | | |
| PACKET RADIO |________| | |
| 133.=205(8) | | |
|__________________| | |
__________________ | ________________________|
| PDP-10 | | |
| SYSTEM B |________ | |
| 49.=61(8) | __|___|___|_ ____________
|__________________| | 49 |_____| 161 |
__________________ | BBN10X-TIP | VDH | ANALOG TIP | Local
| PDP-10 | |____________| |____________| Terminals
| SYSTEM C |________|
| 241.=361(8) |
|__________________|
All host interfaces are local (except host number 005 which is an
easily convertible local/distant interface and we have been asked by
Div 6 to avoid using it so Div 6 can more easily check out PDP-10 IMP
interfaces). The PDP-11 with the line printer is intentionally on
host 105 so that a simple minded program can respond when someone
tries to ICP to its logger socket "To login to BBN (System C) use
host number 241(10)".
[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by Alex McKenzie with ]
[ support from GTE, formerly BBN Corp. 2/2000 ]
AI ELI5
On this page
§1The Host Port Configuration
RFC 667 documents the approved scheme for connecting computers to the ARPANET at BBN. The configuration describes how various PDP-10 and PDP-11 computers connect through Interface Message Processors (IMPs) that form the backbone of the ARPANET. The configuration became effective December 18, 1974.
The document specifies a collection of computers including systems named System A, System B, System C, System D, and special-purpose systems like a speech front end, a line printer terminal, and a packet radio system. Each is assigned a unique host number in both decimal and octal notation.
This document says which computers connect where on the network, and what number each one gets.
§2Physical Layout and Host Numbers
Most host interfaces are local to BBN, meaning they connect by short cables to their assigned IMPs. The configuration uses host ports for routing: a PDP-11 running a line printer is intentionally assigned a host number that allows a simple program to respond to connection attempts with a message directing users to the correct host number for reaching BBN's main system (System C).
The document includes a detailed diagram showing the interconnection of six computers and specialized systems, their connection points to two IMPs (IMP-50 and IMP-5), and links to a Terminal Interface Processor (TIP) and other network sites. The diagram uses octal notation for addresses, which was standard for PDP systems at the time.
The document shows a drawing of all the computers and where each one plugs into the network.
§3Host Identification
Each host is assigned a unique identification number in both decimal and octal notation. The system is designed to allow users to find and connect to the correct host using these identifiers. A clever routing convention places a line printer at a host number that can provide directory assistance to new users, guiding them to the correct address for reaching the main system.
This approach to host naming and numbering reflects the early days of the ARPANET, when host addresses were relatively few and simple mapping schemes could be published in RFC documents.
Each computer gets a number so you know which one you are talking to. One computer was put at a helpful number so it could tell you where to go.