RFC 1068 (rfc1068) - Page 2 of 27

Background File Transfer Program (BFTP)

RFC 1068                                                     August 1988


   Background file transfer has a number of potential advantages for a
   user:

   o    No Waiting

        The user can request a large transfer and ignore it until a
        notification message arrives through some common channel (e.g.,
        electronic mail).

   o    End-to-end Reliability

        The FTC daemon can try a transfer repeatedly until it either
        succeeds or fails permanently.  This provides reliable end-to-
        end delivery of a file, in spite of the source or destination
        host being down or poor Internet connectivity during some time
        period.

   o    Multiple File Delivery

        In order for background file transfer to be accepted in the
        Internet, it may have to include some "value-added" services.
        One such service would be an implementation of a multiple file
        transfer capability for all hosts.  Such a facility is suggested
        in RFC-959 (see the description of "NLST") and implemented in
        some User-FTP programs.

   o    Deferred Delivery

        The user may wish to defer a large transfer until an off-peak
        period.  This may become important when parts of the Internet
        adopt accounting and traffic-based cost-recovery mechanisms.


   There is a serious human-engineering problem with background file
   transfer: if the user makes a mistake in entering parameters, this
   mistake may not become apparent until much later.  This can be the
   cause of severe user frustration.  To avoid this problem, the user
   interface program ought to verify the correctness of as many of the
   parameters as possible when they are entered.  Of course, such
   foreground verification of parameters is not possible if the remote
   host to which the parameters apply is currently unreachable.

   To explore the usefulness of background file transfer in the present
   Internet, we have implemented a file-mover service which we call the
   Background File Transfer Program or BFTP.

   Section 2 describes BFTP and Section 3 presents our experience and
   conclusions.  The appendices contain detailed information about the



DeSchon & Braden