Even
though many free P2P file
sharing systems have been
proposed and implemented,
only very few have stood
the test of intensive daily
use by a very large user
community. The D-tran free
P2P file sharing system
is one of these systems.
Measurements on Internet
backbones indicate that
D-tran has evolved into
one of the most popular
networks.
There are different aspects
that are important for the
acceptance of a free P2P
file sharing system by a
large user community. First,
such a system should have
a high availability. Secondly,
users should (almost) always
receive a good version of
the content they request
(no fake files) Thirdly,
the free P2P file sharing
system should be able to
deal with flashcrowds. Finally,
users should obtain a relatively
high download speed.
The contributions of free
P2P file sharing are the
following: first, we add
to the understanding of
the operation of a free
P2P file sharing system
that apparently by its user-friendliness,
the quality of the content
it delivers, and its performance,
has the right mechanisms
to attract millions of users.
Second, the results can
aid in the (mathematical)
modeling of free P2P file
sharing systems. It is assumed
that the arrival process
and the abort and departure
processes of downloaders
are Poisson, something that
is in obvious contradiction
with our measurements. One
of our main conclusions
is that within free P2P
file sharing systems a tension
exists between availability,
which is improved when there
are no global components,
and data integrity, which
benefits from centralization.
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