Interface Message Processor

An Interface Message Processor (IMP ) is a packet switching node for the ARPANET and the immediate ancestor of modern routers. IMPs are a subject of the first Request for Comments by April 1969, RFC 1

IMPs are based on mini- computers of the series 16 from Honeywell. First, Honeywell DDP -516 were used in a particularly robust design, later Honeywell H316. Using special high-speed serial interface communicated the IMPs with the hosts that they staked to the ARPANET.

The IMP was conceived by Wesley A. Clark, who worked at Washington University in St. Louis at that time. He proposed the concept in April 1967 at a conference before, had invited to the Lawrence Roberts, the head of the ARPANET project. Until then, it had been planned to develop for each to be networked operating system software, which should make interoperability of all. Clark proposed to define an interface that was as easy to implement for all systems, and to provide the interface to the external network separately for such systems that could mediate between the other. This concept was an essential basis of the later Internet.

For June 1968 Roberts and his colleague Barry Wessler written on the basis of a study in the meantime created by the Stanford Research Institute, the final specification of the IMP.

In December 1968, Bolt Beranek and Newman ( BBN ) awarded the contract for the first implementations. The composition of the team that implemented the first IMP was:

• Director: Frank Heart
• Software: Bernie Cosell, William Crowther, Robert E. Kahn, Hawley Rising, Dave Walden
• Hardware: Ben Barker, Severo Ornstein, Marty Thrope
• Unknown task: Bill Bertell (Honeywell), Jim Geisman, Truett Thach

The first IMP was at the University of California, Los Angeles. He was connected to a Sigma 7 from Scientific Data Systems. The second IMP was installed at the Stanford Research Institute (SRI ) and connected to an SDS 940. The first communication was made on October 29, 1969 under the direction of Leonard Kleinrock. It was the first two letters of the word "login". The system crashed, as the third letter was sent. An hour later succeeded the error-free transmission.