  We present new Suzaku and Fermi data, and re-analyzed archival hard X-ray
data from INTEGRAL and Swift-BAT survey, to investigate the physical properties
of the luminous, high-redshift, hard X-ray selected blazar IGR J22517+2217,
through the modelization of its broad band spectral energy distribution (SED)
in two different activity states. Through the analysis of the new Suzaku data
and the flux selected data from archival hard X-ray observations, we build the
source SED in two different states, one for the newly discovered flare occurred
in 2005 and one for the following quiescent period. Both SEDs are strongly
dominated by the high energy hump peaked at 10^20 -10^22 Hz, that is at least
two orders of magnitude higher than the low energy (synchrotron) one at 10^11
-10^14 Hz, and varies by a factor of 10 between the two states. In both states
the high energy hump is modeled as inverse Compton emission between
relativistic electrons and seed photons produced externally to the jet, while
the synchrotron self-Compton component is found to be negligible. In our model
the observed variability can be accounted for by a variation of the total
number of emitting electrons, and by a dissipation region radius changing from
within to outside the broad line region as the luminosity increases. In its
flaring activity, IGR J22517+2217 shows one of the most powerful jet among the
population of extreme, hard X-ray selected, high redshift blazar observed so
far.
