home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
kermit.columbia.edu
/
kermit.columbia.edu.tar
/
kermit.columbia.edu
/
newsgroups
/
misc.20010921-20020314
/
000100_fdc@watsun.cc.columbia.edu_Tue Oct 30 08:55:18 EST 2001.msg
< prev
next >
Wrap
Text File
|
2002-03-13
|
4KB
|
83 lines
Article: 12917 of comp.protocols.kermit.misc
Path: newsmaster.cc.columbia.edu!watsun.cc.columbia.edu!fdc
From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.sys.hp.hpux,comp.protocols.kermit.misc
Subject: Re: transfering files securely (encryption ?)
Date: 30 Oct 2001 13:55:35 GMT
Organization: Columbia University
Lines: 66
Message-ID: <9rmbgn$b4r$1@newsmaster.cc.columbia.edu>
References: <cad82396.0110260651.423f0fd1@posting.google.com> <slrn9trb2v.nb9.Ralf.Hildebrandt@postamt1.charite.de> <9rkbnv$qfg$1@newsmaster.cc.columbia.edu> <slrn9tsp4e.4ki.Ralf.Hildebrandt@postamt1.charite.de>
NNTP-Posting-Host: watsun.cc.columbia.edu
X-Trace: newsmaster.cc.columbia.edu 1004450135 11419 128.59.39.2 (30 Oct 2001 13:55:35 GMT)
X-Complaints-To: postmaster@columbia.edu
NNTP-Posting-Date: 30 Oct 2001 13:55:35 GMT
Xref: newsmaster.cc.columbia.edu comp.sys.hp.hpux:142587 comp.protocols.kermit.misc:12917
In article <slrn9tsp4e.4ki.Ralf.Hildebrandt@postamt1.charite.de>,
Ralf Hildebrandt <Ralf.Hildebrandt@charite.de> wrote:
: On 29 Oct 2001 19:47:11 GMT,
: Jeffrey Altman <jaltman@watsun.cc.columbia.edu> wrote:
:
: >Cygwin on Windows does allow OpenSSH to be used there. But it does
: >not address the lack of support in the SFTP protocol for handling
: >the differences between Stream-Binary, Stream-ASCII, Stream-EBCDIC,
: >Stream-Unicode, and various Record based file formats used on various
: >operating systems. SFTP treats everything as Stream-Binary no matter
: >what.
:
: This restriction was never a problem for me. I just write the stuff the
: way it should appear on the target box.
: YMMV.
:
It might indeed. Lots of tools work for simple cases but not in the
general case. There is a good reason that FTP distinguishes between text-
and binary-mode transfer. FTP was designed in the days of computing
diversity, to interoperate between any pair of computers (the n*n problem)
no matter how their internal file representations differ.
If you only use platforms whose file semantics are all the same, then of
course scp "meets your needs". But from that we can not infer that scp
meets everybody's needs.
Let's look at what happens when you transfer all files in binary mode:
. Sending C source code from DOS or Windows to Unix. You can't compile
it any more because most C compilers do not like CRLF's. Silly and
stupid, we can all agree, but still a fact.
. Sending any text file from Unix to DOS or Windows. You get the
stairstep effect, e.g. when viewing or printing.
These are trivial problems, yet nevertheless so many of today's computer
users are baffled by them that they flood the newsgroups with cries for
help. But let's look at some nontrivial examples:
. Transferring a Unix ASCII text file to an IBM mainframe, which doesn't
use ASCII. It becomes total, incomprehensible garbage. Ditto in the
reverse direction.
. Transferring a text file between a record-oriented file system and a
stream-oriented file system. The record boundaries are lost or turned
into garbage characters.
. Transferring text in (say) German from DOS or Windows to Unix. The
Umlaute become garbage.
. Transferring text in (say) Russian from DOS or Windows to Unix. The
entire text becomes garbage.
Good tools handle not only trivial cases but the general case as well.
Good file-transfer tools follow well-established principals of network
citizenship by not putting proprietary formats on the wire but rather,
always converting to a common intermediate representation for transport.
This includes, for text-mode file transfer, both record format and
character set.
Of course it is easy to say that IBM mainframes, VMS, and so on "don't
matter". This is a dangerous attitude. Monopolies are bad; diversity is
good. Safety and robustness spring from diversity. If you need convincing,
look at the current situation with security and viruses.
- Frank