1. A method for utilizing quota usage policy control in a Diameter-based communication network, the method comprising: at a policy server: sending, to an online charging system (OCS) node, a request for quota usage information associated with a subscriber; receiving the quota usage information and a quota tier level indicator associated with the subscriber from the OCS node; generating at least one policy and charging control (PCC) rule for modifying a quality of service (QoS) policy attribute associated with the subscriber based on the quota usage information and the quota tier level indicator; and communicating the at least one PCC rule to a Diameter network element.