Nowadays, wireless networks are largely deployed, and the number of smart phones has boomed, as well as data transfer via mobile phones. This has resulted in the emergence of multihoming, which allows the user to enjoy the best access for each application. The context of our work is mobile multihomed terminals in a heterogeneous environment. We propose a solution for interdomain mobility management with end-to-end service continuity of communication. For this purpose, we combine a multihoming protocol (SHIM6), which ensures a seamless network change, with the IMS architecture, which allows the establishment of multimedia sessions with quality of service. Our proposal enables a mobile terminal to change its access network seamlessly, without any application disruption. To achieve this, we implement a P-SIP inside the terminal to manage the signaling procedures. The proposed scheme can manage the interdomain mobility of a terminal in two modes: reactive and proactive. A testbed allows us to show the feasibility of our approach and the obtained gain by reducing considerably the handover delay and thus, the data loss.