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From: braden@VENERA.ISI.EDU
Newsgroups: comp.protocols.tcp-ip
Subject: Re: partial transfer recovery in RFC and OSI protocols
Message-ID: <8912201718.AA10297@braden.isi.edu>
Date: 20 Dec 89 17:18:49 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 22


    In article <8912181942.AA10029@arcturus.mitre.org> barns@GATEWAY.MITRE.ORG writes:

	   There is a different FTP restart scheme by Rick Adams which I have
	   heard will be in 4.4(?).  ... it does not try to handle the more
	   difficult cases of operation between divergent systems.

	That is not the case.  His FTP restart scheme relies on the fact that
	your file is eventually expressed as a stream of octets over the TCP
	connection.  His RESTart command simply says to suppress the first N
	octets.  It is brilliantly simple.

Well, not exactly.  How do you compute N, or reset your file to N?  N
is a count of bytes in the transmitted data stream, which is related to
file position parameters through a transformation which could be very
complex.  On the machine with a complex file structure, the only way to
compute N in general is to play through the conversion process.

I believe Bill Barns stated it exactly right.  Rick's scheme is
brilliantly simple only for binary files between Unix systems.

Bob Braden