  Let (A,G) be a C*-dynamical system with G discrete. In this paper we
investigate the ideal structure of the reduced crossed product C*-algebra and
in particular we determine sufficient - and in some cases also necessary -
conditions for A to separate the ideals in Ax_rG. When A separates the ideals
in Ax_rG, then there is a one-to-one correspondence between the ideals in Ax_rG
and the invariant ideals in A. We extend the concept of topological freeness
and present a generalization of the Rokhlin property. Exactness properties of
(A,G) turns out to be crucial in these investigations.
