rfc454.txt

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Network Working Group                                        A. McKenzie
Request for Comments: 454                                            BBN
NIC: 14333                                              16 February 1973

                         FILE TRANSFER PROTOCOL

            Meeting Announcement and a New Proposed Document

   Attached is a new proposal for a File Transfer Protocol.  The
   document is an extensive update to RFC 354 and, I believe,
   incorporates solutions to most of the objections to RFC 354.

   It now seems appropriate to make another attempt to reach final
   agreement on FTP.  Accordingly, I am calling a meeting of interested
   parties, to be held at BBN on March 16, for discussion of this and
   other proposals.

   This note is directed to the network community at large, rather than
   specifically to the old FTP committee, because I don't believe that
   the FTP committee membership includes all the individuals who have
   contributed to the current state of FTP design.  Nevertheless, it is
   intended that the meeting proceed from the current state, rather than
   bringing new members up-to-speed.  Prospective attendees should
   therefore be familiar with at least the following documents:

      RFC 354
      RFC 385
      RFC 414
      RFC 418
      RFC 438

   Anyone wishing to attend this meeting should contact Alex McKenzie
   (NIC Ident aam) at BBN, 50 Moulton Street, Cambridge, Mass. 02138.
   My telephone number is:

                             [phone] ext.441

   When there is some indication of the number of individuals planning
   to attend, a meeting room will be reserved and more specific
   information will be directed to attendees.











McKenzie                                                        [Page 1]

RFC 454                  File Transfer Protocol                July 1972


                      PROPOSED FILE TRANSFER PROTOCOL

   This document is the outcome of a meeting held 25 January 1973 in
   Cambridge, Massachusetts, by the following people:

      Abhay Bhushan (MIT - DMCG)

      Bob Bressler (BBN - NET)

      Bob Clements (BBN - TENEX)

      Alex McKenzie (BBN - NET)

      Nancy Neigus (BBN - NET)

      Ken Pogran (MIT - MULTICS)

      Marc Seriff (MIT - DMCG)

   The basis of the document is RFC 354 with considerations drawn from
   RFC's 385, 414, 418, and 438 and personal communication with network
   participants.





























McKenzie                                                        [Page 2]

RFC 454                  File Transfer Protocol                July 1972


                      PROPOSED FILE TRANSFER PROTOCOL

INTRODUCTION

   The File Transfer Protocol (FTP) is a protocol for file transfer
   between HOSTs (including terminal IMPs), on the ARPA Computer Network
   (ARPANET).  The primary function of FTP is to transfer files
   efficiently and reliably among HOSTs and to allow the convenient use
   of remote file storage capabilities.

   The objectives of FTP are 1) to promote sharing of files (computer
   programs and/or data), 2) to encourage indirect or implicit (via
   programs) use of remote computers, 3) to shield a user from
   variations in file storage systems among HOSTs, and 4) to transfer
   data reliably and efficiently.  FTP, though usable directly by a user
   at a terminal, is designed mainly for use by programs.

   The attempt in this specification is to satisfy the diverse needs of
   users of maxi-HOSTs, mini-HOSTs, TIPs, and the Datacomputer, with a
   simple, elegant, and easily implemented protocol design.

   This paper assumes knowledge of the following protocols:

      1) The HOST-HOST Protocol (NIC #8246)

      2) The Initial Connection Protocol (NIC #7101)

      3) The TELNET Protocol (NWG/RFC #318, NIC #9348)

II.  DISCUSSION

   In this section, the terminology and the FTP model are discussed.
   The terms defined in this section are only those that have special
   significance in FTP.

II.A  Terminology

   ASCII               The USASCII character set as defined in NIC
                       #7104.  In FTP, ASCII characters are defined to
                       be the lower half of an eight bit code set (i.e.,
                       the most significant bit is zero).

   access controls     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
                       provide access controls.



McKenzie                                                        [Page 3]

RFC 454                  File Transfer Protocol                July 1972


   byte size           The byte size specified for the transfer od data.
                       The data connection is opened with this byte
                       size.  Data connection byte size is not
                       necessarily the byte size in which data is to be
                       stored in a system, and may not be related to the
                       structure of data.

   data connection     A simplex connection over which data is
                       transferred, in a specified byte size, mode and
                       type.  The data transferred may be a part of a
                       file, an entire file or a number of files.  The
                       data connection may be in either direction
                       (server-to-user or user-to-server).

   data socket         The socket on which a User-FTP process "listens"
                       for a data connection.

   EOF                 The end-of-file condition that defines the end of
                       a file being transferred.

   EOR                 The end-of-record condition that defines the end
                       of a record being transferred.

   error recovery      A procedure that allows a user to recover from
                       certain errors such as failure of either HOST
                       system or transfer process.  In FTP, error
                       recovery may involve restarting a file transfer
                       at a given checkpoint.

   FTP commands        A set of commands that comprise the control
                       information flowing from the user-FTP to the
                       server-FTP process.

   file                An ordered set of computer data (including
                       programs) of arbitrary length uniquely identified
                       by a pathname.

   mode                The mode in which data is to be transferred via
                       the data connection.  The mode defines the data
                       format including EOR and EOF.  The transfer modes
                       defined in FTP are described in Section III.C.

   NVT                 The Network Virtual Terminal as defined in the
                       ARPANET TELNET Protocol.







McKenzie                                                        [Page 4]

RFC 454                  File Transfer Protocol                July 1972


   NVFS                The Network Virtual File System.  A concept which
                       defines a standard network file system with
                       standard commands and pathname conventions.  FTP
                       only partially embraces the NVFS concept at this
                       time.

   pathname            Pathname is defined to be the character string
                       which must be input to a file system by a user in
                       order to identify a file.  Pathname normally
                       contains device and/or directory names, and file
                       name specification.  FTP does not yet specify a
                       standard pathname convention.  Each user must
                       follow the file naming conventions of the file
                       systems he wishes to use.

   record              A sequential file may be structured as a number
                       of contiguous parts called records.  Record
                       structures are supported by FTP but are not
                       mandatory.

   reply               A reply is an acknowledgement (positive or
                       negative) sent from server to user via the TELNET
                       connections in response to FTP commands.  The
                       general form of a reply is a completion code
                       (including error codes) followed by an ASCII text
                       string.  The codes are for use by programs and
                       the text is for human users.

   server-FTP process  A process or set of processes which perform the
                       function of file transfer in cooperation with a
                       user-FTP process.  The server-FTP process must
                       interpret and respond to user commands and
                       initiate the data connection.

   server site         A HOST site which has a server-FTP process.

   server-TELNET       A TELNET process which listens on a specified
                       socket for an ICP initiated by a user-TELNET, and
                       performs in accordance with the ARPANET TELNET
                       Protocol.

   TELNET connections  The full-duplex communication path between a
                       user-TELNET and a server-TELNET.  The TELNET
                       connections are established via the standard
                       ARPANET Initial Connection Protocol (ICP).






McKenzie                                                        [Page 5]

RFC 454                  File Transfer Protocol                July 1972


   type                The data representation type used for data
                       transfer and storage.  Type implies certain
                       transformations between the time of data storage
                       and data transfer.  The representation types
                       defined in FTP are described in Section III.B.

   user                A process on behalf of a human being or a human
                       being wishing to obtain file transfer service.


   user site           A HOST site satisfying any of the following
                       conditions: 1) The site where a user is located,