Re: FTP questions.


braden@venera.isi.edu
Thu, 11 Aug 88 17:15:28 PDT


        As best I recollect (someone correct me if I'm wrong), TOPS-20 transfers
        that use page structure and stream mode do not close the data connection
        after each file. I don't recall hearing anyone claim that this was
        the wrong thing to do, at least within the last few years. By analogy,
        I think it is ok to leave the connection up for record structure and
        stream mode.

That sounds right to me. If the receiver can unambiguously tell when the
end of data has come by somehow parsing the stream, the sender does not
have to close the connection to indicate EOF. The record-structure
escape sequences in stream mode can carry the EOF bit, or the page
structure has its own encoding that says "last page".

        It's unfortunate that 3.3 is not quite consistent with 3.2 (and
        implicitly disagrees with 3.4.x also, where a point is made of
        saying that the close is necessary in file structure, but nothing is
        said about it for the other structures.) I think that 3.2 should be
        believed. The closing of the data connection at the end of any transfer
        is at the server's discretion, so you wouldn't be out of spec to do it
        if you are writing a server, but as you said in the first place,
        it seems like a useless thing to do.

Right.

        I believe that MIL-STD-1780 FTP is consistent with what I have just
        said. The relevant reference seems to be section 5.4.2, entitled
        "Alternate Data" (huh?) The MIL-STD has its little organizational
        glitches too, you see. Sigh. I have not noticed anything in the MIL-STD
        that replicates the troublesome wording of 3.3 of the RFC, but given
        the way the MIL-STD is put together, I'm not willing to make a promise
        even though I've got it open right in front of me.

Well, I wouldn't know a MIL-STD FTP even if (especially if?) I met one
coming through a dark alley on a moonless night. But people I trust tell
me it is obsolete, being based on RFC-765, so I wouldn't pay attention to
it anyway. Unfortunate, DoD turned its back on Internet standards
some time ago.

Bob Braden

        Bill Barns / MITRE / barns@gateway.mitre.org



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