Re: [ftpext] I-D Action:draft-ietf-ftpext2-hash-00.txt

Anthony Bryan <anthonybryan@gmail.com> Thu, 25 November 2010 23:51 UTC

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Date: Thu, 25 Nov 2010 18:52:25 -0500
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From: Anthony Bryan <anthonybryan@gmail.com>
To: Lothar Kimmeringer <lothar@kimmeringer.de>, mb@smartftp.com
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Subject: Re: [ftpext] I-D Action:draft-ietf-ftpext2-hash-00.txt
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On Wed, Nov 24, 2010 at 7:15 PM, Lothar Kimmeringer
<lothar@kimmeringer.de> wrote:
> Hello,
>
> just being added to the maillist and already having a first question ;-)

welcome, thanks for joining us!

> Am 24.11.2010 23:45, schrieb Internet-Drafts@ietf.org:
>>
>> The File Transfer Protocol does not offer any method to verify the
>> integrity of a transferred file, nor can two files be compared
>> against each other without actually transferring them first.
>
> [...]
>
>> A URL for this Internet-Draft is:
>> http://www.ietf.org/internet-drafts/draft-ietf-ftpext2-hash-00.txt
>
> I read the draft and tried to find the reason by searching the
> archive. Why are startpoint and endpoint (SP and EP) missing?

good question!

as you say, some of the other commands (XCRC, XMD5, XSHA1) support
partial file hashing.

I remember this was on our list of known issues, and we authors
brought it up a number of times. we never received any feedback on it
(except for Mat from SmartFTP on his forum who was for it), so it was
dropped.

[for everyone's info, some of the older FTP drafts like HASH that were
around before this mailing list were discussed on apps-discuss (going
back to March for HASH):
http://www.ietf.org/mail-archive/web/apps-discuss/current/maillist.html
]

> The options are even mentioned in Appendx B. Adding these
> options would e.g. allow to implement distributed downloads where
> parts of the same file can be downloaded from different mirror-
> servers at the same time checking the hash of each part.

that's exactly what we're doing in Metalink/XML & Metalink/HTTP (part
of the reason we needed HASH). mirrors, hashes, & signatures, are
offered over HTTP headers:
http://tools.ietf.org/html/draft-bryan-metalinkhttp (see section 7.1)

the Content-MD5 header which does partial hashes for HTTP is being
phased out I believe. we have the partial file hashes in the XML and
different ranges can be downloaded from mirrors...

> In case you want to add another entry to Appendix B:
> Lobster IntegrationServer (supports XCRC, XSHA1, XMD5; all with
> SP and EP).

done! it'll appear in the next version.
-- 
(( Anthony Bryan ... Metalink [ http://www.metalinker.org ]
  )) Easier, More Reliable, Self Healing Downloads