Described are methods and apparatus, including computer program products, for common telephony services to multiple devices associated with multiple networks. A centralized packet-based network is provided that is capable of providing the common telephony services associated with a subscriber to a first telephony device of the subscriber associated with a first network and to a second telephony device of the subscriber associated with a second network. Each call placed to or from a subscriber's device is routed to the centralized, packet-based network. Each device can be assigned an identical unique identifier. The packet-based service provider network can perform a handoff of the call while the call is in process from the first device associated with the first network to the second device associated with the second network.