Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams (sequences of packets) over a shared network. When traversing network adapters, switches, routers and other network nodes, packets are buffered and queued, resulting in variable delay and throughput depending on the traffic load in the network.

Packet switching contrasts with another principal networking paradigm, circuit switching, a method which sets up a limited number of dedicated connections of constant bit rate and constant delay between nodes for exclusive use during the communication session. In case of traffic fees (as opposed to flat rate), for example in cellular communication services, circuit switching is characterized by a fee per time unit of connection time, even when no data is transferred, while packet switching is characterized by a fee per unit of information.

Leonard Kleinrock (born June 13, 1934) is an American engineer and computer scientist. A computer science professor at UCLA's Henry Samueli School of Engineering and Applied Science, he made several important contributions to the field of computer networking, in particular to the theoretical side of computer networking. He also played an important role in the development of the ARPANET, the precursor to the Internet, at UCLA.

His most well-known and significant work is his early work on queueing theory, which has applications in many fields, among them as a key mathematical background to packet switching, the basic technology behind the Internet. His initial contribution to this field was his doctoral thesis at the Massachusetts Institute of Technology in 1962, published in book form in 1964; he later published several of the standard works on the subject. He described this work as:

"Basically, what I did for my PhD research in 1961–1962 was to establish a mathematical theory of packet networks..."