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This paper describes the IP multimedia subsystem, an overlay network that integrates the technologies of the Internet with the cellular and fixed telecommunications world. In theory the IMS is access independent providing services to any IP connected network, furthermore these networks can implement different QoS models. A flexible QoS provisioning mechanism is needed to dynamically control the network resources on the bearer and session level. This paper presents a hierarchical QoS management framework and suggests enhancements to the current policy decision function implementation. This scheme hides the specific QoS model and access technology from the signaling plane, providing true access independence. A practical testbed that utilises the proposed scheme is described as well as the current status of the implementation.