Research And Improvement On Chord-Based DHT Routing Protocols

Structured P2P network belongs to the third generation of P2P networks. It uses the distributed hash table (DHT) technology, which makes the nodes and resources of the system organized according to certain rules. The use of DHT increases the efficiency of resource location and makes the system has good scalability. Currently, the structured P2P networks based on DHT have become a hot research field in P2P networks.The first part of this paper is focused on how to further improve the searching efficiency of structured P2P networks. The traditional structured P2P network does not take the logical network and physical network topology matching problems into account, which may lead to the nodes close to each other in the logical network are far away in physical network and will make the actual routing less efficient. Meanwhile, the traditional structured P2P network does not consider each node's difference in performance and does not use this feature to improve the system performance. This paper presents a distributed hash table based structured P2P network named "Friend Aware Chord". It has three kinds of resource localization algorithms. The first one uses Super node to locate resource. The second one locates resource through social relations (usually friend), and the third one is the classic Chord algorithm. To achieve the highest efficiency, the nodes can intelligently choose which algorithm to use. In Friend Aware Chord system, nodes with strong calculate power and large network bandwidth will have more friends. These nodes will take greater system load, for they have a greater amount of nodes which will take their routing through them. As a result, nodes in Friend Aware Chord will take different system load according to their performance. Super nodes act as administrators of a group of nodes, and they will take the first class system load. Normal nodes with strong calculate power and large network bandwidth will take the second class system load. Other nodes will bear lighter system load. Friend Aware Chord changes the traditional pure flat structured P2P network into a hybrid P2P network, which is consistent with the development trend of P2P networks. Its performance heterogeneity based distribution of system load makes the system performance is optimized to some extent. Meanwhile, the system can intelligently select the resource localization algorithm, making the efficiency of resource localization of resources to some extent improved.The second part of this paper is concentrated on how to ensure security of structured P2P networks. The safety of ID allocation is the key to ensure security of DHT systems. This paper proposes a safe ID allocation strategy. It uses the hash value of Email address instead of IP address in order to avoid the frequent change of ID due to the frequent change of IP address. Then, it introduces the external Email authentication to ensure the authenticity of applicants, thus it reduces the possibility of the adversary to get a large extent of ID resources. In addition, the paper presents a co-test strategy sponsored by Super nodes to discover malicious nodes. The integrated use of these two strategies will ensure the security of Friend Aware Chord system to a certain extent.In the third part, this paper presents the simulation experiments for the proposed algorithm based on PeerSim, which is a P2P simulation platform. The results proved that Friend Aware Chord has some advantages in average logic routing hops and average delay of resource searching compared with the classic Chord.