  Despite file-distribution applications are responsible for a major portion of
the current Internet traffic, so far little effort has been dedicated to study
file distribution from the point of view of energy efficiency. In this paper,
we present a first approach at the problem of energy efficiency for file
distribution. Specifically, we first demonstrate that the general problem of
minimizing energy consumption in file distribution in heterogeneous settings is
NP-hard. For homogeneous settings, we derive tight lower bounds on energy
consumption, and we design a family of algorithms that achieve these bounds.
Our results prove that collaborative p2p schemes achieve up to 50% energy
savings with respect to the best available centralized file distribution
scheme. Through simulation, we demonstrate that in more realistic cases (e.g.,
considering network congestion, and link variability across hosts) we validate
this observation, since our collaborative algorithms always achieve significant
energy savings with respect to the power consumption of centralized file
distribution systems.
