Hi,
On 15/04/2011 18:43, Vijay K. Gurbani wrote:
One issue that has been talked about in ALTO is whether it can
influence the choice of sub-optimal peers; in other words,
can ALTO be used to purposely provide sub-optimal peers simply
because a peering relationship exists and the peers in the
peering network are sub-optimal (i.e., they may have less upload
bandwidth when compared to other peers).
The third simulation shows that this is not the case, and other
publications [2] have experimentally demonstrated that this
is not the case for BitTorrent at least. BitTorrent exhibits
strong clustering behaviour, where similar-bandwidth peers
cluster together to ensure effective sharing incentives by
rewarding peers who contribute proportionally more to the
system.
what we have done in [2] is in the context of no constraint on the
interconnexion graph
among peers. We studied in [3] the case of a constrained graph (used to
enforce locality).
I believe [3] is more relevant to the discussion, as it shows that even
with a very constrained graph,
BitTorrent is still quite efficient.
However, we didn't looked at the clustering properties with a
constrained graph in [3]. From [2], I am convinced that
if the incoming rate of new pieces in a given ISP is lower than the
upload rate of the fast uploading leechers in that ISP,
it is likely that clustering and sharing incentives will not hold
anymore. The lack of sharing incentives might be a real issue.
For this reason, it is certainly a good idea to use fast uploading
leechers as bridges among ISPs so that
each of those leechers can act as fast surrogate feeds for new pieces.
In that case, clustering and sharing incentives
will still hold.
All my reasoning is in case of torrents that are starting (many
leechers, one seed). As long as there are enough seeds, the
sharing incentive property is less important.
Regards,
Arnaud.
[2] "Clustering and sharing incentives in BitTorrent systems",
Arnaud Legout, Nikitas Liogkas, Eddie Kohler and Lixia Zhang,
ACM Sigmetrics, June 2007.
[3] Stevens Le Blond, Arnaud Legout, Walid Dabbous. Pushing BitTorrent
Locality to the Limit. Computer Networks,
doi:10.1016/j.comnet.2010.09.014, 2010.
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