RFC 691 presented a minor revision of RFC 686, regarding the subject of print files. This current edition of the FTP specification is intended to correct some minor documentation errors, to improve the explanation of some protocol features, and to add some new optional commands. This specification is compatible with the previous edition. A program implemented in conformance to the previous specification should automatically be in conformance to this specification. Access controls define users' access privileges to the use of a system, and to the files in that system.
Access controls are necessary to prevent unauthorized or accidental use of files.
It is the prerogative of a server-FTP process to invoke access controls. The transfer byte size is always 8 bits. The transfer byte size is not necessarily the byte size in which data is to be stored in a system, nor the logical byte size for interpretation of the structure of the data. This connection follows the Telnet Protocol. A full duplex connection over which data is transferred, in a specified mode and type.