Vint Cerf was perhaps one of the greatest contributors to the Internet as we know it today. Working closely with Bob Khan and others from ARPA (Advanced Research Projects Agency, an organization formed under the Department of Defense) he developed and tested TCP/IP (Transmission Control Protocol / Internet Protocol). The IP protocol was developed in order to allow for routing of information from one host to another through a network. TCP allows for encapsulating and decapsulating of packets of information, and thus provides error checking to ensure the integrity of the data regardless of the reliability of the underlying network. TCP/IP enabled the internetworking of many diverse networks. Without it, the Internet as we know it today would not have been able to exist. With it, the Internet has grown at an exponential rate, far beyond even the scope once imagined by the pioneers of this field.
ARPA (Advanced Research Projects Agency), or DARPA (Defense Advanced Research Projects Agency) as it is currently called, was an organization established in early 1958 by President Eisenhower of the United States. Its purpose, officially, was to serve as a highly advanced research and development team devoted to developing far-reaching technological advances. ARPA, as an organization, is unique. Reporting directly to the Secretary of Defense, ARPA is nevertheless an independent team, not bound to any one faction of the military. The staff is rotated every 3-5 years in order to maintain a fresh and inventive perspective, and given generous funding to develop their ideas. It was through ARPA funded programs that the first giant strides in networking were achieved. Many of the pioneers in the development of the Internet were at one time or another part of ARPA's staff. Today, Cerf is the Senior Vice President of Internet Architecture and Engineering for MCI.