| Along with the rapid development of Internet and mobile telecommunication and the ceaseless increase of data traffic, the research on the wireless access of mobile node is impelled. People not only expect that mobile node can access the same networks and share the same resources and services like desktop, but also except that mobile node can retain communication when it moves among some different networks. IETF brings out Mobile IP protocol to support this requirement. Thereby, it is possible that a mobile node accesses Internet. Mobile IP provides IP mobility solution and makes mobile node connect any link using a permanent IP address. Mobile IP is divided into Mobile IPv4 and Mobile IPv6 because of the differences between IPv4 and IPv6. Mobile IPv6 will be used in intending Internet and mobile telecommunication system widely.When mobile node moves between two access points, it has to hand over to ensure normal communications. Mobile node gets a new care-of address when it enters a new subnet and it must send binding update messages to its home agent and correspondent nodes. Because transmitting messages and handling protocols both waste some time, the handover procedure may lead that mobile node can't send and receive data packets for a space and it interrupts the communications between mobile node and its correspondent nodes. How to retain the continuity of communications, how to support various real-time applications, how to reduce the communications discontinuity time and how to reduce the handover effect on QoS are research emphases in Mobile IPv6.Mobile IPv6 had defined mobile detection, new care-of address configuration and binding update. On this basis, researchers proposed various handover methods for improving the handover performance of Mibile IPv6. Fast Handovers for Mobile IPv6 (FMIPv6) effectively reduces the detection latency and the losing of data packets in handover procedure, and effectively improves Mobile IPv6's QoS. In Hierarchical Mobile IPv6 (HMIPv6), a visited domain is divided into several sub domain, and every sub domain has a mobility anchor point. Mobility anchor points of different hierarchies cooperate, make mobile node handover localize and reduce the latency caused by home registration. And Flow-based Fast Handover Method for MIPv6 (FFHMIPv6) makes use of native IPv6 features and reduces care of address registration latency.This article makes an illustration for analyzing handover, and divides handover situation into handover taking place in an anchor domain and handover taking place between two anchor domains. After comparing and analyzing the handover delay of various handover methods, this article introduces a new handover method which is called Integrated Handover Method for Mobile IPv6 (IMIPv6). This new method integrates the advantages and characteristics of various handover methods:(1)adopting the mobile detection technology of HMIPv6;(2)adopting the anchor management method of HMIPv6;(3)adopting the method of using cross router to redirect traffic of FFHMIPv6.IMIPv6 not only reduces mobile detection latency and new care-of address configuration latency, but reduces binding update latency; not only reduces the latency of handover taking place in an anchor domain, but reduces the latency of handover taking place between two anchor domains.On the basis of theoretics analysis, this article also simulates and analyses TCP congestion window size of various handover methods using network simulator NS-2. The next work is to come ture IMIPv6's simulation module in NS-2, and to simulate its TCP congestion window size and its UDP packet losing rate and packet delay. |
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