RFC 310 (rfc310) - Page 1 of 7

Another Look at Data and File Transfer Protocols

Alternative Format: Original Text Document
Next >
Network Working Group                                         A. Bhushan
Request for Comments: 310                                        MIT-MAC
NIC: 9261                                                  April 3, 1972


            Another Look At Data And File Transfer Protocols

   Our experience with ad hoc techniques of data and file transfer over
   the ARPANET together with a better knowledge of terminal IMP (TIP)
   capabilities and Datacomputer requirements has indicated to us that
   the Data Transfer Protocol (DTP) (see ref 1) and the File Transfer
   Protocol (FTP) (see ref 2) could undergo revision.  Our effort in
   implementing DTP and FTP has revealed areas in which the protocols
   could be simplified without degrading their usefulness.

   This paper suggests some specific changes in DTP and FTP that should
   make them more useful and/or simplify implementation.  The attempt
   here is to stimulate thinking so that we may come up with a better
   protocol at the forthcoming Data and File Transfer Workshop (see ref
   3).

Experience to Date

   A number of ad hoc techniques of transmitting data and files across
   the ARPANET already exist.  Perhaps, the most versatile of these
   existing methods is the TENEX "CPYNET" system.  The "CPYNET" system
   uses an ad hoc or interim file transfer protocol developed by Ray
   Tomlinson and others at BBN to transmit files among the TENEX systems
   on the ARPANET. [Private Communication with Bill Crowther, BBN.]

   In CPYNET, the using process goes through the Initial Connection
   Protocol (ICP) to server socket 7, establishing a full-duplex
   connection with an 8-bit byte size.  Control information, including
   user name, password, command (read, write, or append), file name, and
   byte size for the data connection is transmitted from the using
   process to the serving process.  The original full-duplex connection
   is then closed, and a new full-duplex connection is established using
   the original socket numbers but with possibly a different byte size.
   The file is now transmitted on this newly established connection.
   The end-of-file is indicated by closing the connection (the mode of
   transfer is thus similar to DTP "indefinite bit-stream").

   CPYNET has been used quite extensively for transfer of TENEX system
   files.  Because data is not reformatted, and because the optimum
   connection byte size may be used for data transfer, CPYNET is quite
   efficient.  The PDP-10 (and there are quite a lot in the ARPANET)
   works more efficiently with a 36 bit byte size which minimizes
   packing and unpacking of data, and increases effective I/O speed



Bhushan
Next >