[LOG] improved log statements in network classes

Change-Id: I3c3866883c9b61628858d6f69c1bb07a6751b0f7
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1766
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>
Tested-by: Jenkins CI