HOST-HOST communication protocol in the ARPA network

The Advanced Research Projects Agency (ARPA) Computer Network (hereafter referred to as the "ARPA network") is one of the most ambitious computer networks attempted to date. The types of machines and operating systems involved in the network vary widely. For example, the computers at the first four sites are an XDS 940 (Stanford Research Institute), an IBM 360/75 (University of California, Santa Barbara), an XDS SIGMA-7 (University of California, Los Angeles), and a DEC PDP-10 (University of Utah). The only commonality among the network membership is the use of highly interactive time-sharing systems; but, of course, these are all different in external appearance and implementation. Furthermore, no one node is in control of the network. This has insured generality and reliability but complicates the software.