A system includes a wireless access network, a gateway that controls communications between the wireless access network and a packet data network, and a policy-charging-and-rule-function (PCRF). The PCRF includes a routing agent in communication with the gateway and a group of multi-media processing engines (MPEs) that are associated with the routing agent. The routing agent receives from the gateway a request to establish a session for a piece of user equipment, and selects one of the MPEs to handle the session based on an IMSI of the piece of user equipment. The routing agent maintains a table indexed by IP address, and makes an entry therein that points to the selected MPE.