A method is disclosed for use in a Universal Mobile Telecommunications System network comprising an IP Multimedia Subsystem. The method comprises receiving node status information relating to a first node of the network which indicates an occurrence of an event associated with the first node, determining the existence of a network association established between the first node and a second node of the network that would be adversely affected by the occurrence of the event, and causing the network association to be terminated, thereby allowing a new network association between the first and second nodes to be established in its place.