—As the number of Mobile IP (MIP) [2] users grow, so will the demand for delay sensitive real-time applications, such as audio streaming, that require seamless handoff, namely, a packet lossless Quality-of-Service guarantee during a handoff. Two well-known approaches in reducing the MIP handoff latency have been proposed in the literature. One aims to reduce the (home) network registration time through a hierarchical management structure, while the other tries to minimize the lengthy address resolution delay by address pre-configuration through what is known as the fast-handoff mechanism. We present a novel seamless handoff architecture, S-MIP, that builds on top of the hierarchical approach [4] and the fast-handoff mechanism [3], in conjunction with a newly developed handoff algorithm based on pure software-based movement tracking techniques [16]. Using a combination of simulation and mathematical analysis, we argue that our architecture is capable of providing packet lossless hando...