A Protocol for Packet Network Intercommunication by Vinton Cerf and Robert Kahn The article "A Protocol for Packet Network Intercommunication," published in May 1974, describes the philosphy and design for a protocol to interconnect diverse packet communication networks. Written by Vinton Cerf (1943-) of Stanford University and Robert Kahn (1938- ) of the Advanced Research Agency's Information Processing Techniques Office (ARPA/IPTO), this protocol has come to be known as the Transmission Control Protocol/ Internet Protocol or TCP/IP. It is the protocol that has made a global Internet possible. In their article, Kahn and Cerf identified a significant technical problem and proposed a protocol design and philosophy for its solution. The problem, which became evident in the early 197s, is: How is it possible to interconnect diverse packet networks and to make resource sharing possible across boundaries of dissimilar networks? The ARPANET had solved the problem of creating a packet-switching network to connect diverse computers and diverse operating systems. To interconnect diverse packet networks, however, introduced new problems and complexities, including variations in packet format and size, in addressing mechanisms, and other conventions. A design for a protocol for internetwork packet communication would need to be able to accommodate such differences. In early 1973, shortly after he joined ARPA/IPTO, Kahn began considering the problem of providing an architecture to accommodate heterogeneous packet networks. He identified these ground rules: 1. No change would be required in the international operations of participating networks. 2. Gateways would provide the means to oreformat packets to meet the requirements of different networks and to route packets. 3. Communiction would be on a best-effort basis, using transmission and retransmission of packets to get them to their final destination. 4. There would be no global control at the operations level. These rules form the basis for an open networking architecture. Kahn recognized the need for a protocol to embody these ground rules and invited Cerf to collaborate with him on the design. They presented a draft article describing the design and philosophy for such a protocol in September 19973 at a meeting of networking researchers in Sussex, England. The published version of the article appeared in IEEE Transactions on Communications in May 1974. The protocol design provides the means to create a metalevel architecture by designing software for host computers on the diverse networks and for gateways to interface between them. This makes it possible to set up an "association" between hosts on diverse networks without regard to determining any particular path for data transmission. It identifies the need for a means of addressing that will be understood by the gateways and hosts on the diverse networks. The gateways make it possible to reformat packets to accommodate the different packet sizes among different networks and to route packets. The flow control and windowing mechanism make it possible to transmit and retransmit packets until they are received and reassembled at the destination host. The article includes a number of other concepts to implement an internetworking protocol in diverse networks. Rarely has such a technical article had such an impact. It provides the design for the infrastructure for the global Internet. To understand the nature of the Internet, it is important to read, study, and understand the philosophy and design of the internetworking protocol described in this seminal article. Further Reading: Cerf, Vinton, G. and Robert E. Kahn, "A Protocol for Packet Network Intercommunication," IEEE Transations on Communication, Vol. 22, No. 5, May 1974, p. 637-648 from Ronda Hauben, "A Protocol for Packet Network Intercommunication" by Vinton Cerf and Robert Kahn, in Encyclopedia of Computers and Computer History, Vol. 4, Chicago, Fitzroy Dearborn Publishers, 2001, p. 652-653