History of packet switching

The concept of packet switching was first explored by Paul Baran in the early 1960's, and then independently a few years later by Donald Davies (Abbate, 2000). Leonard Kleinrock conducted early research and published a book in the related field of digital message switching (without the packets) in 1961, and also later played a leading role in building and management of the world's first packet switched network, the ARPANET.

Baran developed the concept of packet switching during his research at the RAND Corporation for the US Air Force into survivable communications networks, first published as RAND Paper P-2626 in 1962 [1], and then including and expanding somewhat within a series of eleven papers titled On Distributed Communications in 1964 [2]. Baran's P-2626 paper described a general architecture for a large-scale, distributed, survivable communications network. The paper focuses on three key ideas: first, use of a decentralized network with multiple paths between any two points; and second, dividing complete user messages into what he called message blocks (later called packets); then third, delivery of these messages by store and forward switching.

Baran's study made its way to Robert Taylor and J.C.R. Licklider at the Information Processing Technology Office, both wide-area network evangelists, and it helped influence Lawrence Roberts to adopt the technology when Taylor put him in charge of development of the ARPANET.

Baran's packet switching work was similar to the research performed independently by Donald Davies at the National Physical Laboratory, UK. In 1965, Davies developed the concept of packet switched networks and proposed development of a UK wide network. He gave a talk on the proposal in 1966, after which a person from the Ministry of Defense told him about Baran's work. Davies met Lawrence Roberts at the 1967 ACM Symposium on Operating System Principles, bringing the two groups together.

Interestingly, Davies had chosen some of the same parameters for his original network design as Baran, such as a packet size of 1024 bits. Roberts and the ARPANET team took the name "packet switching" itself from Davies's work.