[Note: This text was posted through a time warp from 1979. Special thanks to Dan Bernstein and Avery Pennarun for their technical expertise.] Computers on the ARPAnet talk to each other using NCP, the Network Control Protocol. Each computer on the ARPAnet has its own public NCP address, similar to a street number; for example, 207. The target of each packet of data is identified by a public NCP address.