Interface Message Processor
Encyclopedia
Node (networking)
In communication networks, a node is a connection point, either a redistribution point or a communication endpoint . The definition of a node depends on the network and protocol layer referred to...
used to interconnect participant networks to the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a ruggedized
Rugged computer
A rugged computer is a computer specifically designed to reliably operate in harsh usage environments and conditions, such as strong vibrations, extreme temperatures and wet or dusty conditions...
Honeywell
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
DDP-516 minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
with special-purpose interfaces and software. In later years the IMPs were made from the non-ruggedized Honeywell 316
Honeywell 316
The Honeywell 316 was a popular 16-bit minicomputer built by Honeywell starting in 1969. It is part of the Series 16 which includes the Models 116, 316, 416, 516 and 716. They were commonly used for data acquisition and control, remote message concentration, clinical laboratory systems and...
which could handle two-thirds of the communication traffic at approximately one-half the cost. An IMP required the connection to a host computer via a special bit-serial
Serial communications
In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels...
interface, defined in BBN Report 1822
BBN Report 1822
BBN Report 1822 specifies the method for connecting a host computer to an ARPANET router, called an Interface Message Processor . This connection and protocol is generally referred to as 1822, the report number....
. The IMP software and the ARPA network communications protocol running on the IMPs was discussed in RFC 1, the first of a series of standardization documents published by the Internet Engineering Task Force
Internet Engineering Task Force
The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...
(IETF).
The idea of the IMP being a separate computer was suggested by Wes Clark
Wesley A. Clark
Wesley Allison Clark is a computer scientist and one of the main participants, along with Charles Molnar, in the creation of the LINC laboratory computer, which was the first mini-computer and shares with a number of other computers the claim to be the inspiration for the personal computer.Clark...
to Larry Roberts
Lawrence Roberts (scientist)
Lawrence G. Roberts received the Draper Prize in 2001 and the Principe de Asturias Award in 2002 "for the development of the Internet" along with Leonard Kleinrock, Robert Kahn, and Vinton Cerf....
who led the ARPANET implementation for the Department of Defense's Advanced Research Projects Agency (ARPA). The IMPs were built by Bolt Beranek and Newman
BBN Technologies
BBN Technologies is a high-technology company which provides research and development services. BBN is based next to Fresh Pond in Cambridge, Massachusetts, USA...
(BBN).
The original IMP team at BBN consisted of:
- Team Leader: Frank Heart
- Software: Willy CrowtherWilliam CrowtherWilliam Crowther is a computer programmer and caver. He is best known as the co-creator of Colossal Cave Adventure, a seminal computer game that influenced the first decade of game design and created a new game genre, text adventures.-Biography:During the early 1970s Crowther worked at defense...
, Dave Walden, Bernie Cosell - Hardware: Severo OrnsteinSevero OrnsteinSevero M. Ornstein is a retired computer scientist and son of Russian-American composer Leo Ornstein. In 1955 he joined MIT's Lincoln Laboratory as a programmer and designer for the SAGE air-defense system. He later joined the TX-2 group and became a member of the team that designed the LINC. He...
, Ben Barker - Theory and collaboration with the above on the overall system design: Bob KahnBob KahnRobert Elliot Kahn is an American Internet pioneer, engineer and computer scientist, who, along with Vinton G. Cerf, invented the Transmission Control Protocol and the Internet Protocol , the fundamental communication protocols at the heart of the Internet.-Career:After receiving a B.E.E...
- Other: Hawley Rising
- Added to IMP team later: Marty Thrope (hardware), Jim Geisman, Truett Thach (installation), Bill Bertell (Honeywell)
The first IMP was delivered to Leonard Kleinrock
Leonard Kleinrock
Leonard Kleinrock is an American engineer and computer scientist. A computer science professor at UCLA's Henry Samueli School of Engineering and Applied Science, he made several important contributions to the field of computer networking, in particular to the theoretical side of computer networking...
's group at UCLA on August 30, 1969. It used a SDS Sigma-7 host computer. Douglas Engelbart
Douglas Engelbart
Douglas Carl Engelbart is an American inventor, and an early computer and internet pioneer. He is best known for his work on the challenges of human-computer interaction, resulting in the invention of the computer mouse, and the development of hypertext, networked computers, and precursors to GUIs...
's group at the Stanford Research Institute (SRI) received the second IMP on October 1, 1969. It was attached to an SDS-940
SDS 940
The SDS 940 was Scientific Data Systems' first machine designed to support time sharing directly, and was based on the SDS 930's 24-bit CPU built primarily of integrated circuits. It was announced in February 1966 and shipped in April, becoming a major part of Tymshare's expansion during the 1960s...
host. The first communication test between these two systems took place on October 29, 1969 when a login to the SRI machine was attempted, but only the first two letters could be transmitted. The SRI machine crashed upon reception of the 'g' character. A few minutes later the bug was fixed and the login attempt was successfully completed.
A variant of the IMP existed, called the TIP, which connected terminals instead of computers to the network; it was based on the 316. Initially, some Honeywell-based IMPs were replaced with multiprocessing BBN Pluribus
Pluribus
The Pluribus multiprocessor was an early multi-processor computer designed by BBN for use as a packet switch in the ARPANET. Its design later influenced the BBN Butterfly computer....
IMPs, but ultimately BBN developed a microprogrammed clone of the Honeywell processor.
IMPs were at the heart of the ARPANET until it was decommissioned 20 years later in 1989. The last IMP on the ARPANET was the one at the University of Maryland.
External links
- A Technical History of the ARPANET with photos of IMP
- IMP history with photo of developers
- Dave Walden's memories of the IMP and ARPANET
- Oral history interview with Severo Ornstein, Charles Babbage InstituteCharles Babbage InstituteThe Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....
, University of Minnesota. Ornstein was principal hardware designer of the IMP. - Internet STD 39, also known as BBN Report 1822BBN Report 1822BBN Report 1822 specifies the method for connecting a host computer to an ARPANET router, called an Interface Message Processor . This connection and protocol is generally referred to as 1822, the report number....
, "Specification for the Interconnection of a Host and an IMP".