ARPANET Protocols

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This page keeps track of ARPANET protocols, classified by status, and RFC and year.

Used on ARPANET (1969-1981)

This section covers protocols that were at one used or tested on ARPANET. This list is not considered to be comprehensive, but should cover any protocol predating RFC 791 or predate 1981, which defined IP. These protocols, by and later cover

Protocols Listed in RFC 349

RFC 349 contains the earlist listen of "well known services" as of 1972, and assigns static socket numbers. NCP was a half-duplex protocol, so each application was assigned in pairs of two (so telnet would use sockets 1 and 2).

ARPANET Well Known Sockets
Socket Assignment
1 Telnet
3 File Transfer
5 Remote Job Entry
7 Echo
9 Discard


Originally defined in RFC 15. User experience is documented in RFC 206


Originally defined in RFC 114.


Remote Job Submission RFC 325

Echo Protocol

Provides a loopback service to determine if a given host is available or not. Considered obsolete on modern systems, originally documented as RFC 347.

Discard Protocol

Discards all incoming data; intended to use for diagnostic and testing. Documented as RFC 348

Protocols with known implementations

These protocols are known to have at least some sort of implementation as documented by later documentations, or exist in some form in archived source code or similar.



NETWORK CHARACTER DISPLAY PROTOCOL. RFC 205. Implementation notes discussed on RFC 387



Simple Minded File System


Mail Protocols

Due to an influx of different systems and needs, a large number of email systems were to exchange mail between systems. How much these were used is a matter of some debate. RFC453 discusses the need for a "Network Mail" protocol between sites. It's known by the 1976 Network UNIX dump from TUHS that a sendmsg implementation was included on UNIX/PDP systems connected to ARPANET.



Network Utilities

Network utilities represents testing protocols, or infrastructure ones

Host-IMP Protocol (1822)

Documented in RFC 7, the Host-IMP protocol is the set of commands that a given computer would use to talk to ARPANET directly. It's comparable to the AT commands used in Hayes modems.


Network Voice Protocol

Network Graphics Protocol

Originally discussed inRFC94, and more formally defined in RFC186, its unclear if the Network Graphics Protocol was ever used beyond basic testing. RFC387 discusses real world problems in deploying graphics over the network, and a need to design for the least common denominator.

CSNET/NSFNET Era (1981-1989)

This era largely covers the growth and development of

Berkeley r-commands

R utilties represent commands popularized by BSD, and common in most TCP/IP implements of the era ==


The World Wide Web (1990-2000)