A method of enabling redundancy for a Home Subscriber Service (HSS) of an IP Multimedia Subsystem (IMS) is provided. Redundancy is provided by a plurality of HSS instances. Where a client node of the IMS requires details of an HSS, the client node is provided with details of a proxy HSS representing the HSS instances. The client node uses the details to send a subsequent request directed to the proxy HSS. The proxy HSS selects an appropriate one of the HSS instances to handle the request received at the proxy HSS from the client node. The proxy HSS forwards the request to the selected HSS instance for handling.