Interface Message Processor


The Interface Message Processor (IMP) is a specialized computer from the early days of the internet, which played a crucial role in packet-switching for ARPANET, the predecessor to the modern internet. IMPs acted as gateways between connected computers, helping to send and receive messages by breaking them into smaller packets and routing them to their destination. Developed in the late 1960s, IMPs paved the way for the evolution of internet routers and modern-day network communications.


The phonetic pronunciation of “Interface Message Processor” is:- Interface: /ˈɪn.tər.feɪs/- Message: /ˈmɛs.ɪdʒ/- Processor: /prəˈsɛs.ɔ/ or /proʊˈsɛs.ər/

Key Takeaways

  1. The Interface Message Processor (IMP) was the first packet-switching node to be used in the development of ARPANET, which served as the basis for the modern internet.
  2. IMP essentially enabled efficient communication between different computer systems by breaking down messages into smaller data packets and sending them through a network to their destination, where they were reassembled.
  3. Developed by Bolt, Beranek and Newman (BBN) in the 1960s, IMP played a crucial role in the birth and evolution of computer networking and laid the groundwork for many future networking technologies and protocols.


The Interface Message Processor (IMP) holds significant importance in the history of technology, as it played a crucial role in the early development of the internet.

Created in the late 1960s, the IMP served as the very first device to implement the principles of packet switching, a key innovation that allowed for efficient and reliable data transmission across networks.

By acting as a node that connected two or more networks, the IMP facilitated communication and data exchange, enabling the robustness and versatility required for large-scale computer networks.

As a foundational building block in the creation of the ARPANET, the predecessor of the modern internet, the Interface Message Processor’s pioneering role in network communications cannot be understated, as it paved the way for future advancements and the global connectivity we enjoy today.


Interface Message Processors (IMPs) play a critical role in the early stages of digital communication systems by facilitating seamless communication across diverse networks. Their utilization emerged in the 1960’s with the inception of the pioneering ARPANET, which was the predecessor to today’s internet.

One of the primary purposes of an IMP is to act as a gateway that enables data transmission between different computer networks regardless of the underlying hardware or software infrastructure. It is the cornerstone that supports data transfer across a robust and open system, thus paving the way for the now widely recognized modern protocol of the internet, the TCP/IP suite.

IMPs primarily ensure the efficient transmission of networking packets through the ever-growing network infrastructure. With an on-board controller to manage the complexity of interfacing, IMPs perform various tasks such as buffering, error detection and diagnostics, routing, and congestion control, thereby improving overall network performance.

Also responsible for establishing and maintaining connections, IMPs contribute to the flexibility, resilience, and reliability of the network. Through their seamless and efficient integration with a multitude of nodes, Interface Message Processors played a decisive role in shaping the foundation upon which our current internet relies, enabling an unprecedented level of global interconnectedness.

Examples of Interface Message Processor

The Interface Message Processor (IMP) is an early packet-switching device that was designed to work as an interface between host computers and the ARPANET, the predecessor to the modern internet. Here are three real-world examples involving the IMP technology:

BBN’s IMP & ARPANET:Bolt, Beranek, and Newman (BBN), a research and engineering company, was responsible for the development of the first IMP. BBN was awarded the contract by the Advanced Research Projects Agency (ARPA) to build four IMPs in

On October 29, 1969, the first two IMPs were connected on ARPANET, where one IMP was located at the University of California, Los Angeles (UCLA) and the second at the Stanford Research Institute (SRI).

Honeywell DDP-516 Minicomputer:The original IMP was built using Honeywell’s DDP-516 minicomputer, with modifications to support packet switching and communication capabilities for ARPANET. The DDP-516 had 12K words of memory and was capable of processing 6K bits per second. This minicomputer acted as a translator between host computers and the ARPANET by receiving, processing, and sending data packets efficiently.

SATNET Satellite Connection:In 1973, the ARPANET began testing an experimental satellite connection called SATNET, aiming to connect ARPANET nodes across the Atlantic. The IMP technology played an essential role in implementing this connection by enabling packet-switching across the satellite link. As a result, it laid the foundation for future developments in satellite-based communication networks.In conclusion, while the Interface Message Processor is now an obsolete technology, it was crucial in the early development of the internet and computer networks. It showcased the practical ability of packet-switching technologies and set the stage for the evolution of digital communication networks.

Interface Message Processor FAQ

What is an Interface Message Processor (IMP)?

An Interface Message Processor (IMP) is a crucial component in the early design of the ARPANET, which is the precursor to today’s modern internet. It was responsible for the packet-switching in the network, thus allowing effective communication between computers and other networking devices.

How did the Interface Message Processor work?

The IMP worked by receiving data packets from a host computer, processing the packets, and forwarding them to the correct destination on the network. This packet-switching technology was essential in allowing multiple computers to communicate over a single network effectively, laying the foundation for the contemporary internet’s structure.

Who invented the Interface Message Processor?

Dr. Lawrence G. Roberts and his team at the Advanced Research Projects Agency Network (ARPANET) invented the Interface Message Processor. The first IMP was installed on September 2, 1969, at the University of California, Los Angeles (UCLA).

Which company built the first Interface Message Processor?

Bolt Beranek and Newman (BBN) was the company that built the first Interface Message Processor. BBN was awarded the contract in 1968 to create the IMP for ARPANET, then later became a significant contractor for the United States Department of Defense and the National Science Foundation.

What was the significance of the Interface Message Processor?

The Interface Message Processor played an essential role in the development of packet-switching technology and the creation of the ARPANET. It set the stage for the modern internet’s structure and the growth of communication networks worldwide. The IMP showcased the potential of a distributed and connected network, allowing information exchange and computer resource sharing on an unprecedented scale.

Related Technology Terms

  • Packet Switching
  • Network Protocols
  • Data Communication
  • Router

Sources for More Information


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