Multicasting with selective delivery: A SafetyNet for vertical handoffs
  In future mobility support will require handling roaming in heterogeneous access networks. In order to enable seamless roaming it is necessary to minimize the impact of the vertical handoffs. Localized mobility management schemes such as FMIPv6 and HMIPv6 do not provide sufficient handoff performance, since they have been designed for horizontal handoffs. In this paper, we propose the SafetyNet protocol, which allows a Mobile Node to perform seamless vertical handoffs. Further, we propose a handoff timing algorithm which allows a Mobile Node to delay or even completely avoid upward vertical handoffs. We implement the SafetyNet protocol and compare its performance with the Fast Handovers for Mobile IPv6 protocol in our wireless test bed and analyze the results. The experimental results indicate that the proposed SafetyNet protocol can provide an improvement of up to 95% for TCP performance in vertical handoffs, when compared with FMIPv6 and an improvement of 64% over FMIPv6 with bicasting. We use numerical analysis of the protocol to show that its signaling and data transmission overhead is comparable to Fast Mobile IPv6 and significantly smaller than that of FMIPv6 with bicasting. 
Henrik Petander, Eranga Perera, Aruna Seneviratne