[BitTorrent] Implementing Vivaldi?

shad0wmatt3r mgp at ucla.edu
Wed Jul 14 21:17:10 EDT 2004

I was wondering if anyone here had attempted to incorporate Vivaldi
into BitTorrent, or whether Vivaldi has been considered for inclusion
in the 2.0 spec?

Vivaldi is a de-centralized algorithm/manner in which peers on a P2P
network can assign themselves synthetic k-dimensional coordinates
(typically, k = 5). The Euclidian distance between the coordinates of
two peers is a reasonable estimate of the latency between them. You
can go to http://www.pdos.lcs.mit.edu/papers/hotnets:vivaldi/paper.pdf
for the full paper.

Because peers in BitTorrent already exchange messages with one another
constantly, and because Vivaldi data is meant to be piggybacked on
"normal" messages in a P2P system, it seems like BitTorrent is an
ideal application for Vivaldi. I'm no BitTorrent expert, but I was
thinking it could be like this:

* When a peer contacts the tracker for the first time, to get an
initial list of peers, the returned list is random.
* When the peer contacts the other peers in this list, it gets their
Vivaldi coordinates and, combined with pinging, can establish it's own
approximate Vivaldi coordinates.
* Each successive time the peer contacts the tracker for peers, it
includes its own Vivaldi coordinates. The tracker responds with n
peers that are close to its coordinates (but not necessarily _the_ n
closest peers as determined by the Euclidian distance -- that could be
computationally expensive). These peers are expected to have, on the
average, lower ping times than the peers in the initial random list,
and so we would expect, on the average, faster downloads.

Any thoughts?

Michael Parker

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