Research On The Handover Technology Of The Mobile IPv6

Mobile IPv6(MIPv6) protocol supports a mobile node to be accessed by Home Address wherever it is in home network or roaming in foreign network.However,there exists several seconds of latency while the mobile node handovers to a new subnet;therefore the communication of the mobile node is interrupted for a period of time,which is unacceptable to the real-time traffics such as VoIP.So IETF founded a workgroup named MIPSHOP to research on optimizing the handover process,to achieve the goals of reducing handover latency & packet loss & signaling overhead.Fast Handovers for Mobile IPv6(FMIPv6) protocol and Hierarchical Mobile IPv6 Mobility Management(HMIPv6) are the two protocols the workgroup develops.Mobile IPv6 is still a premature protocol so far.This is because the mobile IPv6 protocol is built on existing fixed network based on the IPv6 protocol.From a functional point of view, Mobile IPv6 protocol support in the global roaming mobile terminals,which has resolved the problem occours when nodes move between different IPv6 subnets,but from the performance point of view,when the mobile terminal switching from one subnet to another subnet,its communication is interrupted for a few seconds or even more than 10 seconds.The problem of excessive switching delays do not have a great influence on some operations(such as file transfer),but for real-time and TCP latency sensitive operations the impact is tremendous.In addition,Mobile IPv6 switching will be in the introduction of additional signaling overhead,signaling crossing through the backbone network may increase the burden on the backbone network.Therefore,the practicality of Mobile IPv6 need for switching optimization.The dissertation researched on the operation process of MIPv6,FMIPv6 and HMIPv6 protocols in detail and analyzed every kinds of latency introduced by handover.Based on the comprehensive research on FMIPv6,two problems was discussed which the current FMIPv6 protocol does not solve.These problems are:Ping-Pong movement;the FNA message may be dropped.The happening of the problems will result in packet loss.To the first problem, the dissertation provided the solution of bringing in the concept of transition period.In the transition period,the mobile node cannot affirm its attachment to the new subnet until it connects to the new subnet stably.To the second problem,the dissertation provided the solution of adding an acknowledgement to FNA message and defined the acknowledgement message format,which avoids handover failing arising from the FNA message dropping. Finally,on the base of MobiWan,which is the extension module of the Network Simulation tool,improved PredictiVe Fast Handover scheme was designed and implemented.Via simulating base handover of MIPv6 and Fast Handover scheme,it is indicated that,the Predictive Fast Handover performance is improved on the aspect of handover latency and packet loss.