The communications protocol used to transmit a file to a user, also known as a file transfer protocol. For example, the Internet uses HTTP and FTP, which ride over TCP/IP. Unix systems use FTP over TCP/IP, as well as UUCP. In the days of analog modems, general-purpose communications programs used a common protocol, such as Xmodem or Ymodem, at both ends of the transmission. See
TCP/IP,
FTP,
HTTP,
UUCP,
Xmodem and
Ymodem.