RFC 269 (rfc269) - Page 1 of 3


Some Experience with File Transfer



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Network Working Group                                   H. Brodie
Request for Comments #269                               UCLA-NMC
NIC # 7817                                              6 December 71
Categories:  File Transfer
Updates:  122, 238, 172
Obsoletes:  None


                   Some Experience with File Transfer

At UCLA-NMC we have recently completed implementation of a program which
utilizes UCSB's storage capability via their Simple Minded File System
(See RFC #122 by Jim White for a description of SMFS).  The use of the
program is detailed in Appendix A.

We learned a number of things in the implementation effort and
subsequent usage.  We think a number of these apply towards the
development of a net- word-wide File Transfer Protocol, and we hope to
stimulate further dis- cussion of these issues.  We discovered some
things in the UCSB protocol that we would like to see included in the
network-wide protocol, and we see some things that are in the currently
proposed net protocol and are unfortunately absent from the UCSB
protocol.

In the first category, is the UCSB file retrieval procedure.  The user
specifies among other things, a bit count of the number of bits to be
retrieved in the current request.

Successive RTF commands yield successive pieces of the file.  Portions
of the file can be spaced over by use of the SPF command.  We think that
the ability of the user to specify the size of the "chunks" of the file
he is about to receive, along with the ability to access any part of the
file without having to get the entire file, is definitely an advantage.
It makes the user programs easier to write since the problem of parsing
the input stream virtually disappears, as the user program knows exactly
what to expect at all times.  In addition, the one request, one response
nature of the protocol avoids the problem of sending a request and then
receiving pieces of data of unpredictable size at unknown intervals.
The response to each RTF gives the comforting knowledge that "they're
still listening".  This leads us to believe that there is much to be
gained by the adoption of a one request, one response type of protocol.
We might point out that for any significant file transfer, this does not
seriously cut down on the overall data transfer rate, since a
"defaulting" type of approach, as SMFS uses can be used to keep the
request messages very small.  We also have found the mandatory password
scheme of UCSB quite easily used, and any server site, (i.e. a site
specifically advertising file storage) can reasonably be expected, in
our opinion, to require passwords (see also RFC #238 by R. Braden).


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