On Fri, Sep 12, 2003 at 12:59:11PM -0400, Dan Merillat wrote: > On Fri, 12 Sep 2003, Edgar Friendly wrote: > > > Thomas Leske <[EMAIL PROTECTED]> writes: > > > > > The intension of probalistic caching is to keep data longer > > > available in the network and improve routing. It works by > > > giving data source nodes a better clue on the global popularity > > > of the data, because the reloads increase its local popularity. > > > > > <SNIP> > > > > let me get this clear, you're proposing to have nodes pretend they > > don't have data? This seems to have the downside of non-probabilistic > > ... unless it comes back as DNF, in which case they answer "Yes". > Basically a "I have this, but let's let the 'owner' know it's popular" > scheme. Better to translate it to an InsertRequest, though. That way, > if you get a collision, great, the data is still there. If not, you > send the data both ways, up to the "best" node and down to the node > requesting it.
Why is this useful? > > Even with those fixes the proposal loses. It solves the > "popular-to-death" problem but opens up new flooding attacks. Indeed. Without pcaching, or with this proposal as far as I read it, the flooding attacker has a work factor of 25; with pcaching it's more like 5. > > Popular-to-death is a very difficult attack where you request the same > key from lots of nodes that should NOT be specalized in it. When they > find the key, you've pulled it to the edges of the network... now > requests for it never reach the "best" node so it dies of LRU. Quit > requesting it and many of the edge nodes will begin dropping it... and > eventually the content is gone. (Note: Edge nodes are the nodes most > unspecialized for a particular part of keyspace. They should have the > most hops to reach it.) Clever. > > The fact that freenet routing is so dynamic makes this attack neigh > impossible. Flooding is a much more valid concern. Hrrm. > > --Dan -- Matthew J Toseland - [EMAIL PROTECTED] Freenet Project Official Codemonkey - http://freenetproject.org/ ICTHUS - Nothing is impossible. Our Boss says so.
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