The Next-Generation Wireless Networks (NGWNs) are believed to exhibit a heterogeneous environment which imposes various challenges, among them Mobility Management is most crucial. The FMIPv6 protocol has been standardized by IETF to address certain shortcomings of the baseline Mobile IPv6. However, it does not directly support vertical handovers. Therefore, research is still going on to develop more effective IPv6 based vertical handoff protocols for efficient support of frequent and seamless roaming. This paper presents a new protocol named Distributed Signaling Fast Mobile IPv6 (DS-FMIPv6) which effectively addresses reduction of handoff latency, signaling costs and power overheads for a better support of seamless & frequent vertical handoffs.