PC/TCP Packet Driver

PC/TCP Packet Driver is a networking API for MS-DOS, PC DOS, and later x86 DOS implementations such as DR-DOS, FreeDOS, etc. It implements the lowest levels of a TCP/IP stack, where the remainder is typically implemented either by TSR drivers or as a library linked into an application program. It was invented in 1983 at MIT's Lab for Computer Science (CSR/CSC group under Jerry Saltzer and David D. Clark), and was commercialized in 1986 by FTP Software.