A method of constructing a globally unique locator for a network entity attached to a network. A path between a core network and the network entity via intermediate network entities is determined by applying policy routing. The globally unique locator for the network entity is constructed by concatenating elements identifying the locations of the network entity, the intermediate network entities and a node in the core network. The identifying elements are obtained from Attachment Registers associated with each of the network entity, the intermediate network entities and the node in the core network.