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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. The protocol is defined in RFC 1. 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. Initially, some Honeywell based IMPs were replaced with multiprocessing BBN Pluribus IMPs, but ultimately BBN developed a microprogrammed clone of the Honeywell processor.

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.^[1] A few minutes later the bug was fixed and they successfully logged in.

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.

They were the first generation of what is known as a router today.^{[2] [3] [4]}

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)

1. ^ Hambling, David (2005). Weapons Grade. New York City: Carroll & Graf. ISBN 0-78671-769-6. 
2. ^ IMP -- Interface Message Processor, LivingInternet Accessed June 22, 2007.
3. ^ Looking back at the ARPANET effort, 34 years later, Dave Walden, Accessed June 22, 2007.
4. ^ A Technical History of the ARPANET - A Technical Tour, THINK Protocols team, Accessed June 22, 2007.

• 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
• Internet STD 39, also known as BBN Report 1822, "Specification for the Interconnection of a Host and an IMP".

• ARPANET

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