Design And Simulated Implementation Of Rerouting Mechanism With ABC Supported In NGI

It has been the urgent demand to enjoy the high quality network service any time and any place in NGI (Next Generation Internet), which indicates that NGI must support ABC (Always Best Connected) at the beginning of and during the communication in order to allow users both to connect and use services in the best way. However, handoff caused by user's movement will lead to the interruption of communication and loss of packets, which brings great influence on user's QoS. In this thesis, a rerouting mechanism with ABC supported is designed to ensure user's QoS effectively.First, cell coverage and transmitting power are added into user preference to support ABC in the rerouting mechanism. In this way, user's QoS can be effectively guaranteed when he or she is moving with higher speed or lower remaining battery capacity. Second, several service policies are offered by network providers according to user's application type and the final pricing of each service policy is jointly determined by the bandwidth price and floating price.According to the hierarchical cell structure, resource reservation is divided into two types, that is, vertical and horizontal reservation to guarantee QoS after rerouting. Vertical reservation is mainly designed when the utility of user located in the cell's inner section is decreased and the cell which can maximize user's utility will be selected as the target cell for vertical reservation. Visiting probabilities of the cells which can be reached by user is computed with user's current motion parameters and the cells with higher probabilities will be chosen as the target cells for horizontal reservation.Rerouting should be aided by resource reservation to become fast and effective with lower overheads. While satisfying the optimal goal, a cross router is found out from the previous access router reversely. After that, local path reestablishment is made between the cross router and the new access router. Therefore, the number of links requiring resource reservation is greatly reduced.The mechanism above is implemented based on the NS2 simulating platform. And the results are analyzed and show that the mechanism is feasible and effective.