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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Network Working Group H. Brodie

Request for Comments #269 UCLA-NMC

NIC #7817 6 December 71

Almost immediately after starting to use SMFS we found a serious lack in

one area. There is no way for a user to ask "what files do I have

there?" As a matter of fact, the author suspects that there are already

several files there which he has "forgotten" about! It is reasonable,

perhaps even necessary, for any server to supply a nicely formatted

character string describing the files stored there for this password, or

user, or whatever division is used. The listing should also contain

other pertinent information, such as date created, size etc.

In the meantime, UCSB is providing the SEX system with valuable "out-of-

line on-line" storage, and we look forward to the development of a

widely accepted file transfer protocol, implemented on a large number of

server sites, hopefully equipped with low cost bulk storage.

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SEX Notebook Appendix A H. Brodie

Section 23.29                                           3 December 71

FXFER

FXFER is a re-entrant program written in Symbol which is used to send a

receive file from UCSB, using their Simple Minded File System. For the

description of the Network interface to SMFS, see RFC #122 by Jim White.

Files are stored there in a paged format identical to the paged format

that the tape process uses: <header><data page><data page>... Thus a

file which Master lists as having n pages will take 2048 n bytes of

storage at UCSB. The user's sign-on initials are used as both the

access and modification passwords, so that if a file is sent under on

user's sign-on, they can only be retrieved or deleted by him.

Commands

PA - Increments "print All" counter. Different settings of this

counter yield different levels of program trace output on the console.

NP - No print. This sets the "Print All" counter to zero.

DF FOO - This deletes the file "FOO" located at UCSB.

PF FOO - This sends the file "FOO", pointed to by the user's root

directory, to UCSB. Only read access is needed to "FOO".

GF FOO - The file "FOO" located at UCSB is retrieved and put in the

user's root (with write access). Note that it must have been sent by the user to have the right password.

RN FOO BAR - Rename the file "FOO" at UCSB to "BAR". The same password

restrictions as with PF and GF apply. (Not yet implemented)

ST - Status. Tells what program is doing and how much its done.

X - Exit Program.

If the system and/or UCSB is particularly slow, then UCSBFIL may type a

time-out message. At this point the user has the option of continuing,

or exiting the program. The message is self-explanatory, as are most of

the program's messages.

[ This RFC was put into machine readable form for entry ] [ into the online RFC archives by Nick Christenson 10/97]

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