According to the present invention there is provided a method of ensuring that all AF sessions for an IP-CAN session reach the same PCRF when more than one PCRF is deployed in an operator network. The method involves configuring a PCRF such that, upon receipt of a request relating to the establishment or modification of the IP-CAN session, the PCRF determines one or more Application Detection and Control (ADC) rules for identifying application messages associated with the IP-CAN session and that require that an address of the PCRF must be included in the identified AF session messages. The PCRF is further configured to provision the one or more ADC rules at an ADC node.