| In company with the rapid development of Internet and increasingly comprehensive application of Mobile Computing, Research on mobile computer wireless access was impelled. Like desktop, mobile computer want to access the same network and share the same resource and service, and that not limitation to some fixed area. Moreover when mobile computer is moving, it is convenient to cut previous connection and establish new connection. IETF brings out Mobile IP protocol to support this requirement. Thereby it is possible to mobile accessing Internet. Mobile IP provide IP mobility solution and make it possible for mobile node to change its point of attachment without losing its ability to communicate and use a permanent IP to access any link. But when mobile node moves between two foreign agents, it had to handoff to ensure normal communications. As result of high move frequency, mobile node may not finish home registration in time, the data packets send to mobile node will lost. If mobile node spend long time to handoff, such as the current handoff procedure is not finished and mobile node move to another foreign agent, a new handoff occurs, there will made more latency and packets lost.For the sake of solve mobile IP handoff problem, a fast handoff scheme is proposed, this scheme introduce fast move detection algorithm and distributed foreign agent hierarchies. The algorithm asks L2 and L3 to cooperate and effectively reduce the detection latency in handoff procedure. A visited domain is divided into several sub area, there is a foreign agent hierarchy in every sub domain, Gateway Foreign Agents of different foreign agent hierarchies cooperate and made mobile node handoff localization, reduce the latency cause of home registration. Fast handoff scheme reduce the latency and data packets lost in handoff procedure, effectively improve mobile IP's QoS.
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