Leonard Kleinrock is an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 engineer

Engineer

An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...

 and computer scientist

Computer scientist

A computer scientist is a scientist who has acquired knowledge of computer science, the study of the theoretical foundations of information and computation and their application in computer systems....

. A computer science professor at UCLA's Henry Samueli School of Engineering and Applied Science

Henry Samueli School of Engineering and Applied Science

The Henry Samueli School of Engineering and Applied Science at the University of California, Los Angeles was opened with an enrollment of 379 students in the fall of 1945. It opened as the College of Engineering until it was changed to school on February 21, 1969. The School now has seven...

, he made several important contributions to the field of computer network

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

ing, in particular to the theoretical side of computer networking. He also played an important role in the development of the ARPANET

ARPANET

The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...

, the precursor to the Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

, at UCLA.

His most well-known and significant work is his early work on queueing theory

Queueing theory

Queueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...

, which has applications in many fields, among them as a key mathematical background to packet switching

Packet switching

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 over a shared network...

, the basic technology behind the Internet.