SRI serial line file transfer protocol

[sri-unix!fylstra.tsca at SRI-UNIX]

A growing number of personal computers and word processors are in use
at SRI on projects and in the homes of SRI employees.  The SRI
Networks Group proposes to provide software enabling most personal
computers to transfer text and data files to and from mainframe
computers.  The medium of communications will be a hardwired
line or a dial-up telephone connection.  We anticipate that the first
version of this service will provide the MODEM2 file transfer protocol
on our hosts by using the following software:

	o MODEM206 on our CP/M systems
	o FTPS and FTPG on our TOPS-20 systems
	o UMODEM on our Unix systems
	o A VAX/VMS implementation (to be written)
	o (Possibly) an Apple-DOS implementation

While simple, efficient, and readily available, the MODEM2 protocol
suffers from a few drawbacks:

	o It imposes a potentially heavy load on mainframes;
	o Because it requires raw binary access to the serial line
	  and timeout service, it is difficult to implement on some
	  operating systems;
	o Because it does not provide a complete, ARPANet-like model,
	  it requires the user to exercise manual control over
	  the connection.

We would like to hear from the ARPANet community concerning alternatives
to MODEM2 that recommend themselves.  Here are some ground rules:

	o The service should provide reliable file transfer of text
	  and binary data;
	o The protocol should be implementable on most hosts with
	  relative simplicity, preferably in languages such as Pascal,
	  C, SAIL, or FORTRAN;
	o The file transfer model should make it possible to provide
	  a simple human interface.

Some specific questions we have are:

	o Are other groups already working on this problem?
	o Does CSNet have any plans to extend the MMDF package to
	  provide FTP service using the phone channel link-level protocol?
	o Do MMDF implementations exist on non-Unix systems?
	o Would UUCP be a viable approach for file transfer?
	o Does PCNet ever expect to finalize its protocol and documentation?

Please send replies to FYLSTRA at SRI-KL or telephone Dave Fylstra
at (415)859-2816.  Thanks to one and all.