Re: returning results for partial downloads

Zlatin Balevsky wrote:
> I believe most of these ideas are already implemented in the current
> download mesh.  What is missing are the ideas for queueing discipline.
>  That is a very interesting topic, and it would be a very exciting
> challenge to come up with schemes that can beat bittorrent's
> tit-for-tat.

I thought BitTyrant's approach was interesting: it tries to determine
the threshold at which it will be unchoked by each peer, sorts the peers
by their download/upload ratios at the threshold, and uploads to as many
as possible given the available upstream bandwidth.

http://bittyrant.cs.washington.edu/

In a sense though, it's parasitic on BitTorrent's tit for tat strategy:
it exploits the fact that once you persuade a peer to unchoke you,
there's nothing to be gained by further increasing your upload speed.

It seems to me that the prisoner's dilemma isn't the appropriate model
for this problem: uploading to one neighbour prevents you from uploading
to another, so you can't treat the situation as a set of separate
two-player games. I've been working on an extension of the prisoner's
dilemma that incorporates resource scarcity:

http://www.cs.ucl.ac.uk/staff/mrogers/sharers-dilemma.html

You can see the parallel between BitTyrant's strategy and the utility
maximisation strategy in the sharer's dilemma. Saleem Bhatti and I were
thinking of running a tournament to find good strategies for the
sharer's dilemma. Any takers? :-)

Cheers,
Michael