To register a mobile device located in a first network with a packet-switched services network, a registration request is received from an aggregation device in the first network. The registration request contains an identifier of the aggregation device and identification information of the mobile device, where the identification information is previously unknown to the packet-switched services network. A globally unique identifier of the mobile device is dynamically created based on the identifier of the aggregation device and the identification information of the mobile device, wherein the globally unique identifier is used for uniquely identifying the mobile device in the packet-switched services network.