| Summary: | 碩士 === 國立中興大學 === 電機工程學系 === 92 === IEEE 802.11 Wireless LAN standard was ratified a few years ago and lots of vendors have engaged in the manufacture of Wireless LAN products compliant with 802.11. However, 802.11 did not specify how to implement Distribution System (DS).When mobile nodes roam among access points (AP) of different vendors, the context transfer used to keep connection uninterrupted may be failed. This will become a hurdle to widely deploy 802.11 Wireless LAN. In order to overcome this problem, 802.11f was proposed and specified a set of services that will enable multi-vendor access points to interoperate with each other. However, 802.11f only works when a mobile node roams in the same subnet. Once the mobile node moves across different subnets, data connection between terminals will break down. Originally engineered as a solution for Wireless LAN, Mobile IP enables a mobile node to move freely from one subnet to another without disrupting end-to-end connectivity. Besides, the AAA (Authentication, Authorization, and Accounting) architecture is essential for Internet Service Provider (ISP) to handle security and accounting considerations, especially when users roam among different administrative domains. For some big network domains, the mobile node’s current network attach point could be far away from its static home agent and would cause a long delay when registration request is processed.
In this thesis, we first give an introduction to 802.11f and analyze the situation as 802.11f cooperates with Mobile IP. In order to improve both intra and inter domain roaming efficiency, we propose a theoretical model which integrates 802.11 and Mobile IP in AAA environment. We analyze the operation of the model and discuss what kinds of problem this model faces. In intra domain roaming, we make use of the “context pre-transfer model” to pre-establish 802.11 services for the user. In inter domain roaming, we also utilize “Simultaneous Handoff of Mobile IPv4 and 802.11” (SIMIP) to process 802.11 reassociation and Mobile IP registration at the same time. Furthermore, we use a new function of next generation AAA protocol, Diameter, to allocate a new home agent for the user to process subsequent Mobile IP registration locally.
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