Bob Kahn

Robert E. Kahn, (born December 23 1938), along with Vinton G. Cerf, invented the TCP/IP protocol, the technology used to transmit information on the modern Internet.

He received a B.E.E. from the City College of New York in 1960, and a M.A. and Ph.D. degrees from Princeton University in 1962 and 1964 respectively. He worked for a while at Bell Laboratories, and as an Assistant Professor of Electrical Engineering at MIT. He took a leave of absence from MIT to join Bolt Beranek and Newman (BBN), where he was responsible for the system design of the ARPANET, the first packet-switched network.

In 1972 he moved to DARPA, and in October of that year, he demonstrated the ARPANET by connecting 40 different computers at the International Computer Communication Conference, publicizing the network to the general public for the first time. After he became Director of DARPA's Information Processing Techniques Office (IPTO), he started the United States government's billion dollar Strategic Computing Program, the largest computer research and development program ever undertaken by the federal government.

While working on a satellite packet network project, he came up with the initial ideas for what later became the Transmission Control Protocol (TCP), which was intended as a replacement for an earlier network protocol, NCP, used in the ARPANET. While working on this, he played a major role in forming the basis of open-architecture networking, which would allow computers and networks all over the world communicate with each other, regardless of what hardware or software the computers on each network used. To reach this goal, TCP was designed to have the following features:

• Small sub-sections of the whole network would be able to talk to each other through a specialized computer than only forwarded packets (first called a gateway, and now called a router).
• No portion of the network would be the single point of failure, or would be able to control the whole network.
• Each piece of information sent through the network would be a given a sequence number, to ensure that they were dealt with in the right order at the destination computer, and to detect the loss of any of them.
• A computer which sent information to another computer would know that it was successfully received when the destination computer sent back a special packet, called an acknowledgement, for that particular piece of information.
• If information sent from one computer to another was lost, the information would be retransmitted, after the loss was detected by a timeout, which would recognize that the expected acknowledgement had not been received.
• Each piece of information sent through the network would be accompanied by a checksum, calculated by the original sender, and checked by the ultimate receiver, to ensure that it was not damaged in any way en route.

Vint Cerf joined him on the project in the spring of 1973, and together they completed an early version of TCP. Later, it was separated into two separate layers, with the more basic functions being moved to the Internet Protocol (IP). The two together are usually referred together as TCP/IP, and are the basis for the modern Internet.

After thirteen years with DARPA, he left to found the Corporation for National Research Initiatives (CNRI) in 1986, and as of 2003 is the Chairman, CEO and President. CNRI is a not-for-profit organization which is intended to provide leadership and funding for research and development of the National Information Infrastructure.

External links

• Biography of Robert E. Kahn (http://www.cnri.reston.va.us/bios/kahn.html) on the Corporation for National Research Initiatives' website.
• Bio of Robert E. Kahn (http://livinginternet.com/i/ii_kahn.htm) from the Living Internet.

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