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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Chunking
(when using chunked-encoding) can change at each intermediate http proxy. It is
basically just a way to transfer the http-body between a client and a server.
Keep in mind that a proxy acts both as a client (to the upstream server) and as
a server (to the downstream client). So a proxy could for example cache the
entire http-body from the upstream server and then send it to it’s own down-stream
client in one shot. Or it could use a smaller internal buffer then it’s upstream
server and hence split the http-body into smaller chunks when sending it to it’s
client.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>--------<br>
Alex WULMS<br>
Lead Developer/Systems Engineer<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Tel:
+32 2 655 3931<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Information
Systems - SWIFT.COM Development<br>
S.W.I.F.T. SCRL</span><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><o:p></o:p></span></p>
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<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> http-crcsync-bounces@lists.laptop.org
[mailto:http-crcsync-bounces@lists.laptop.org] <b>On Behalf Of </b>Toby Collett<br>
<b>Sent:</b> Wednesday, April 01, 2009 8:18 PM<br>
<b>To:</b> WULMS Alexander<br>
<b>Cc:</b> tridge@samba.org; jg@freedesktop.org; http-crcsync@lists.laptop.org;
angxia Huang; XS Devel<br>
<b>Subject:</b> Re: [Http-crcsync] Apache proxy CRCsync & mozilla gsoc
project?<o:p></o:p></span></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So a quick question, what sort of http transfers are
chunking most often used for? I believe we will get poor results with the
method for most types of binary data, which tend to be the larger files. In the
web context these will generally have not changed at all (in which case
traditional caching will help) or will have changed completely in which case
the hashing is just overhead. Happy to be corrected on this point.<br>
<br>
Actually while we are on this thought do we want to add the strong hash to the
request headers so the upstream server can reply with use the cached version.
This would allow the server side to correct for sites that don't use correct
cache headers (i.e. static images with no cache information).<br>
<br>
One alternative to the fail on error is to hold a copy on the server end for a
short period so we can retransmit unencoded, but this is probably unacceptable
overhead on the server side, especially if we can't manage to maintain a TCP
session for the retry.<br>
<br>
Are there any headers sent with each http chunk, we could always put our strong
hash across these, assuming that chunking is defined at source and not
repartitioned by caches and proxies in between.<br>
<br>
Toby<o:p></o:p></p>
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