[p2p-hackers] How to solve the "Britney problem"?

Ian Clarke ian at locut.us
Wed Dec 29 12:03:45 UTC 2004


A simple and (IMHO) elegant approach used in Freenet (that can also 
been applied to DHTs) is for nodes to cache the responses to requests 
that they forward in a least-recently-requested cache.  If a node 
receives a request for some data in its cache it responds immediately 
(updating the timestamp in the cache accordingly).

The effect of this is that the load of responding to requests for 
popular information is spread among peers close to that information, 
the more popular it is, the more peers will cache it.  As its 
popularity decreases it will be cached in fewer machines - and so it 
adapts to shifting file popularity.

This approach is also employed by Dijjer (http://dijjer.org/).

Ian.

On 28 Dec 2004, at 16:56, Enzo Michelangeli wrote:
> DHT's such as Kademlia work well when they are used to store large 
> numbers
> of items with different keys. But let's suppose, for example, that a 
> lot
> of nodes want to advertise their IP addresses as the place where people
> can find an instance of a very common resource, such as, say, an open
> proxy for some kind of protocol. All the records will then have the 
> same
> key: Hash("Resource XYZ available here"), which means that the few 
> unlucky
> DHT nodes with ID close to that hash will be requested to store the
> pointers for ALL the records. To some extent this already happens with
> filesharing applications: nodes with ID close to Hash("britney") are
> requested to store metadata information for all Britney Spear's MP3 
> files.
> However, those may amount, at most, to few hundred or maybe thousand
> records; but in the case I mentioned before the number of records may 
> grow
> unbounded as more and more resource providers jpin the scheme. Are 
> there
> techniques devised specifically to solve this problem?
>
> Enzo
>
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--
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