Re: ftp in java
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On Mon, 11 Aug 2008, Christian wrote:
Tom Anderson schrieb:
On Sun, 10 Aug 2008, Arne Vajh?j wrote:
Tom Anderson wrote:
On Sun, 10 Aug 2008, Arne Vajh?j wrote:
Christian wrote:
The Big problem is that FTP has no verification for files. After
transferring a file you never know if it has been transferred without
errors ... no hashing not even a stupid crc-check is done imho FTP
should die as soon as possible. Its a danger to any files integrity.
HTTP is no different.
That type of check are usually done at a higher level than basic file
transfer.
And lower - TCP has a checksum, as do pretty much all link-layer
protocols.
But that is on packets not on files.
True, but since the file is transferred in packets, it also covers the
file. Your TCP or HTTP/FTP implementation could put the packets together
wrongly, and that wouldn't be detected, of course, but that's a rather
hypothetical risk.
I'm not saying that file-level checksums aren't needed - they're a very
good idea, not least because the TCP checksum is very weak - just that
there is already a layer of checksumming here.
its 2 Layers..
Well, or a thick layer, depending on how you look at it :).
and IP checksums will be removed in the future (IPv6 may be I will live
that long until it really comes to the homeuser).
The checksum is in TCP, not IP. IPv6 will make no difference to TCP's
checksumming, as far as i know.
Experience shows that filechecksums are needed because of misbehaving
NATs and misbehaving firewalls. Some of these devices try to replace IPs
in the data packages. Also Zone Alarm 4 for example had some problems
with corrupting package data.
Good point.
A way to get round this would be to use an encrypted protocol like HTTPS
that the middleboxes can't interfere with. Also, TLS, which is the secure
component of HTTPS, includes message authentication codes, which are a
kind of checksum.
Filechecksums is a must. Nice is to have some interleave level of a
merkletree so only parts of the file have to be redownloaded again.
Yes, that's a pretty cool approach.
tom
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DO NOT WANT!
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