I&#39;ve spoken to a number of ISPs over the past year who are using P2P caching products, and they all stated that they were seeing benefits from them.<br><br>You&#39;re correct in that there&#39;s probably a lot of data which is only requested once (just like a HTTP cache), but there will also be files which could be downloaded dozens of hundreds of more of times - and 100 downloads of a 60 min TV shows (350MB) is 35GB of saved traffic - not a huge amount in the scheme of things, but multiple it out to a month or a year and the numbers get significant enough.<br>
<br>Most of these products also cache in both directions. ie, they will pull from the cache not only when one of your clients downloads a file from elsewhere on the Internet, but also when a host elsewhere on the Internet downloads from one or your clients. Depending on how you pay for your tail to the client the caching can have a saving not only on bandwidth out to the Internet but even on domestic tail costs.<br>
<br>As others have said, the copyright issue isn&#39;t really any different to that for a web cache.&nbsp; Sure, you might suspect that there&#39;d be a higher percentage of &quot;illegal&quot; material transfered over P2P than HTTP, but that doesn&#39;t mean it&#39;s all illegal...<br>
<br>Most/all of the caching products also give the ability to shape P2P traffic, which can be a good thing or a bad thing depending on how you manage it.&nbsp; From memory Exetel in Australia openly admit that they shape P2P traffic during peak hours, but let it run free during quiet times, and that hasn&#39;t caused them any issues.&nbsp; Comcast in the US on the other hand got taken to court for doing basically the same thing.&nbsp; Most of the ISPs I&#39;ve spoken to are doing some form of P2P shaping, although generally not signifant, and normally they don&#39;t make that fact known.<br>
<br>I&#39;d say the majority of ISPs are still not doing P2P caching, although more and more are at least using it on part of their network.&nbsp; If you&#39;d asked me a few months ago I would have said that this number will increase over time, but at the moment in the US at least there seems to be a move away from P2P and back to HTTP/streaming protocols.&nbsp; Why bothered downloading a P2P of a TV show when you can watch it on Hulu, InnerTube or YouTube?&nbsp; Why bothered downloadind a movie when you can stream it form NetFlix?<br>
<br>&nbsp; Scott.<br><br><br><div class="gmail_quote">On Tue, Nov 18, 2008 at 6:42 PM, Cameron Kerr <span dir="ltr">&lt;<a href="mailto:ckerr@cs.otago.ac.nz">ckerr@cs.otago.ac.nz</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div style="">I&#39;m updating my labnotes for my network management paper regarding the use of proxy caches, and previously I have pointed to the possibility of caching peer-to-peer traffic as shown in the paper <i>Deconstructing the Kazaa Network</i><div>
<br></div><div><a href="http://portal.acm.org/citation.cfm?coll=GUIDE&amp;dl=GUIDE&amp;id=837393" target="_blank">http://portal.acm.org/citation.cfm?coll=GUIDE&amp;dl=GUIDE&amp;id=837393</a></div><div><br></div><div>I would like to know whether or not caching of peer-to-peer is something that ISPs actually do today, and if not why not. I imagine there are probably some interesting legal interactions, but I&#39;m eager to find out how industry is moving in this field.</div>
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<div>--&nbsp;</div><div>Cameron Kerr &lt;<a href="mailto:ckerr@cs.otago.ac.nz" target="_blank">ckerr@cs.otago.ac.nz</a>&gt;</div><font color="#888888"><div>Teaching Fellow, Computer Science, University of Otago</div><div><br></div>
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