With the convergence of the Internet and cellular networks, voice-over-IP (VoIP) applications across wired and wireless domains are of increasing importance. Two major mobility management protocols, Mobile IP (MIP) and session initiation protocol (SIP), have been proposed to handle macro-mobility in the network layer and the application layer respectively, either independently or jointly for different scenarios. The paper explores the capabilities of MIPv6 and SIP in supporting VoIP applications from the point of view of "mobility awareness" or "mobility unawareness". It proposes a MIP-SIP hybrid mobility management architecture that enables mobile hosts running mobility-unaware applications to communicate with CHs (correspondent hosts) running mobility-aware applications. The paper focuses on. macro-mobility support across wireless and wired domains and compares the hybrid architecture with MIPv6 and SIP in terms of handoff disruption time and the user-perceived quality of service (QoS) through analysis and proof-of-concept simulations. The AAA (authentication, authorisation and accounting) functions are also considered for inter-domain handoffs.