Song Haibin wrote:
"On the other hand, P2P systems not adopting the tit-for-tat approach
(e.g. the eDonkey network) should not be damaged by locality-based"
It is not clear to me. Peer selection (tit-for-tat like choking algo in
BT) is not the only one factor of efficiency, there is also piece
diversity.
Edonkey/emule also use rarest first (but a less efficient peer selection
algorithm). Therefore, as locality adversely impact
piece diversity, my bet is that Edonkey/emule will suffer from locality.
What do you mean with "less efficient" by saying "Edonkey/emule also use
rarest first (but a less efficient peer selection algorithm)"?
The peer selection algorithm of a P2P protocol is a tradeoff between
maximizing
the efficiency (in terms of download completion time, or upload
utilization of leechers) and fostering
persistency of seeds (and of the torrent).
BT with its choking algorithm clearly fosters the efficiency of the
torrent. The peer selection algorithm of Emule
fosters persistency. You are served by a peer when you are the first one
in its waiting queue. You place is the queue is mainly of function of
the time
you spent in the queue and your upload contribution. I believe this
upload contribution and the rarest first piece selection was added to emule
based on BT experience in order to improve its efficiency, but the main
focus of emule is still to keep peers as long as possible in the swarm
in order
to improve the persistency of contents.
Regards,
Arnaud.
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