The next-generation IP-based mobile network must accommodate various kinds of wireless access technologies, including W-CDMA. Although the soft handover technique should be supported if W-CDMA is used, redundant paths will be created by the soft handover scheme employed by the 3rd generation mobile communication system. This paper proposes the Network Distributed Soft Handover (NDSHO) method, which achieves soft handover control in an IP network but without any redundant paths. NDSHO continuously optimizes all routing paths by relocating the data copy point dynamically during communication according to the movement of the mobile terminal. To achieve the proposed method, this paper introduces a copy point seamless relocation method and an optimal point selection method which takes advantage of OSPF. Furthermore, we show quantitatively that NDSHO makes more efficient use of system resources than the 3rd generation system.