On Wed, Apr 18, 2001 at 05:01:30AM +0100, Michael Rogers wrote:
> But many of them will be holding copies of the same files (especially if
> they're neighbouring nodes). Maybe when a node runs out of space it should
> work from the bottom of its datastore upwards, and for each file, ask its
> neighbours whether thay also have that file. If one of its neighbours has
> the file, it drops it. If it reaches the top of the datastore without
> finding a file that is redundantly stored by one of its neighbours, it
> drops the file at the bottom of the datastore.
There are a number of reasons why this is a bad idea, the easiest to
explain is that if you can ask a node whether it has a file, then it
makes it easier to prove that a node was caching a file, and under some
legal systems, this would allow you to justify shutting down the node.
Normally, the only way you can find out whether a node is caching a file
is to request the file from it, but then if it is not caching the file
it will go out and find it. Even making a request of HTL 1 won't work,
because there is some randomness in how the HTL is decremented.
Ian.
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