Since the data forwarding in Vehicular Ad Hoc Network (VANET) is inefficient, a technology on data forwarding and routing selection based on Software Defined Network (SDN) was proposed. Firstly, a hierarchical architecture of SDN based VANET, which was consist of local controller and global controller, was used to separate data forwarding from transmission control and decide the direction of data forwarding flexibly. Secondly, a vehicular routing mechanism of single road section was designed and data could be transmitted stably by predicting vehicular position and using greedy strategy. Thirdly, to achieve the goal of path disjoint which could avoid the bandwidth bottleneck between multiple demands, a road section routing mechanism was proposed, which combined the Breadth First Search (BFS) and edge set. Finally, compared with Ad Hoc On-demand Distance Vector (AODV) routing, the proposed algorithm could increase data reception rate by 40% and reduce average delay by 60%. The simulation results show that the technology on data forwarding and routing for software defined VANET can effectively improve the data delivery rate, and reduces the average packet delay.

Since the efficiency of data forwarding in Vehicular Ad Hoc Network (VANET) is low, a data forwarding mechanism in VANET based on Software-Defined Network (SDN) was proposed. Firstly, a hierarchical architecture of SDN based VANET was designed. This architecture was consist of local controller and vehicular, it could implement the separation of control and data forwarding, and also could achieve high scalability, reliability and efficiency. Secondly, a new data forwarding mechanism was proposed, which used dynamic programming and binary search. Finally, compared with Ad Hoc On-demand Distance Vector routing (AODV), Destination Sequenced Distance Vector routing (DSDV), Dynamic Source Routing (DSR) and Optimized Link State Routing (OLSR) algorithm, the proposed algorithm could improve packet delivery fraction and end-to-end delay. Therein, the average increase of packet delivery fraction was about 100%, while the average reduction of end-to-end delay was about 20%. The simulation results show that the data forwarding mechanism in software-defined VANET can effectively improve the packet delivery and reduce the end-to-end delay.

Vehicular Ad Hoc Network (VANET) is a highly dynamic communication network, which means it's a great challenge to design a stable data dissemination mechanism. Applying Named Data Networking (NDN), which focused on the content of the data, to VANET could effectively relive the problems brought by the frequent change of network topology. Firstly, the message types and data structure of NDN were improved. Secondly, the way of establishing routes according to section was put forward with the combination of characteristics of VANET so as to reduce the cost of data dissemination. The simulation results show that compared to the traditional NDN algorithm which is applied to VANET data dissemination, Average Hit Rate (AHR) and Average Forward Times (AFT) can be significantly improved by VANET data dissemination mechanism based on NDN. Therein, the average increase of AHR is about 53 percent points, while the average reduction of AFT is about 0.4 times. Therefore, the improved VANET data dissemination mechanism can improve the efficiency of data dissemination by using the new routing method.

Concerning the problem that the data in distributed system usually has many replicas among several datacenters and a robust mechanism was required to maintain data consistency, an algorithm of geographically distributed replication management was proposed after further research on the replication theory of distributed systems. Microsoft Research used Service Level Agreements (SLA) to divide the consistency requirements of users into several levels, each of which was associated with tolerable delay. The system ensured that users could have higher service levels within tolerable delay. Tuba system extends Pileus, it can dynamically change the location of primary and secondary replicas according to statistics sent by all users, so as to raise the average performance of the system. But the replication of Tuba system was carried out based on a single target unit. Improving the method in Tuba system, a set of algorithms independently to change the location of primary and secondary replicas was proposed. The mechanism was implemented in the replication among the HBase distributed systems. After the system is completed, the results show that taking the correlation between two regions into consideration when changing the location of primary and secondary replicas can improve the overall utility of the system.