Interface Message Processor

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Leonard Kleinrock and the first IMP. Taken from http://www.lk.cs.ucla.edu/personal_history.html

The Interface Message Processor (IMP) was the packet-switching node used to connect computers to the original ARPANET in the late 1960s and 1970s. To connect to the ARPANET, host computers communicated with IMPs using a special high-speed bit-serial interface. The IMP itself was a ruggedized Honeywell DDP-516 mini-computer with special-purpose interfaces and software. In later years the IMPs were made from the non-ruggedized Honeywell 316. There was also a variant called the TIP which connected terminals instead of computers to the network, which was based on the 316.

The IMP was conceived of by Larry Roberts and the implementation was done by Bolt, Beranek, and Newman. The first IMP was placed at UCLA on August 30, 1969. It was attached to a SDS Sigma-7. IMP number two arrived at the Stanford Research Institute (SRI) on October 1, 1969. It was attached to an SDS-940. The first communication between IMPs was the first three letters of the word "login." The SRI machine crashed after the 'g' was transmitted. A few minutes later the bug was fixed and they successfully logged in.

IMPs were at the heart of the ARPANET until it was decomissioned 20 years later in 1989. The last IMP on the ARPANET was the one at the University of Maryland.

The original IMP team at BBN consisted of:

Team Manager: Frank Heart
Software: Dave Walden; Willy Crowther; Bob Kahn; Bernie Cosell; Hawley Rising
Hardware: Severo Ornstein; Ben Barker; Marty Thrope
Unknown: Jim Geisman; Truett Thach; Bill Bertell (Honeywell)