[Standards] Fwd: [TechReview] Review of XEP-0234, 0260 and 0261.

Matthew Wild mwild1 at gmail.com
Tue Aug 17 11:37:05 UTC 2010

On 17 August 2010 05:21, Peter Saint-Andre <stpeter at stpeter.im> wrote:
> I'm forwarding this old message to the Standards list for further
> discussion. Expect follow-ups soon.
> /psa
> -------- Original Message --------
> Subject: [TechReview] Review of XEP-0234, 0260 and 0261.
> Date: Fri, 28 May 2010 14:53:14 +0200
> From: Steffen Larsen <zooldk at gmail.com>
> Reply-To: XSF Technical Review Team <techreview at xmpp.org>
> To: XSF Technical Review Team <techreview at xmpp.org>
> CC: XMPP Extension Discussion List <standards at xmpp.org>
> Hi All,
> Me, Joe and Ali have spend some time last week to review the XEPs
> described in the subject.
> Here is our summary of XEP-0234 (which I also mailed earlier to the tech
> list):
> Hash transfer in section 3. has a poor wording: "At any time, the
> hosting entity can communicate the hash of the file to the receiving
> entity".
> We believe that it should be changed to "At any time (during the session
> life-time or before the session terminates)".
> That will make it more unambiguous that it can only be done in the right
> state (that is in a session that is not terminated yet).
> The <file> tag has a size attribute, but the unit is not explained
> anywhere. Its only in XEP-0096 chapter 3 it is explained that the unit
> is bytes. It is the same with the hash attribute. In XEP-0234, it is not
> visible that it is the MD5 checksum that is used as algorithm.
> In XEP-0234 it does not look like that we can do resumable downloads of
> files. In XEP-0096 it looks like that there is defined an optional
> <range> element. If ranged queries are to be implemented, we could do
> that as a transport options/transport features (XEP-0260/0261). But it
> seems like that this feature is left out at present time.

Just a quick note that if we add ranges, we should make sending the
hash with the session-initiate a SHOULD. Otherwise the receiving
client has no way to judge whether it is the same file except by the
filename and size.

Also I've had bad experience (as a user) with transfer resumption thus
far... I think some clients just ignore the range, and send from 0,
causing the range-supporting recipient to receive the start of the
file twice. So either we make range support mandatory, or we need some
way for the initiator to announce it.


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