Research On The Key Issues Of Structured P2P Network

Peer-to-Peer(P2P) network is a virtual or an overlay network which built on theInternet. The main advantages of P2P network are self-organization and distributedstructure. In general, P2P network can be classified into two categories: structured P2Pnetwork and unstructured P2P network. This thesis focuses on the key issues ofstructured P2P network. The structured P2P network uses distributed hash tables(DHTs)as the substrate to provide data publishing and retrieving. DHTs use hash functions toachieve the mapping relationship between name space and hash space. Note thatdifferent DHT system use different algorithm to publish and retrieve objects. DHTshave many advantages such as scalability, reliability and fault-tolerance. In addition tosupporting the P2P systems, DHTs are also used to construct the next generationInternet and content delivery network. In LISP system, a mapping system whichconstructed by DHT has been proposed. In content delivery network(CDN) network, thenaming system of PSIRP project has been constructed by DHT.In this thesis, the author investigated some key issues of structured P2P networksuch as mismatch problem, load balancing problem and reliability problem. Thestructure of this thesis is organized as follows:1. In chapter one, the author introduced the backgrounds of DHTs andstate-of-the-art of some open issues.2. In chapter two, the author analyzed the primary cause of mismatch problem: theformation of logical topology ignores the information of the underlying topology. Thework used the weighted bipartite graph to model the matching relationship betweenlogical space and physical space and used the KM algorithm and genetic algorithm tosolve the mismatch problem with the given lookup traffic matrix.3. In chapter three, the author investgated the application and deployment of DHTsin the LISP scheme, the work proposed the enhanced pointer-based Chord architectureto construct the mapping system of LISP: LISP-PCHORD. LISP-PCHORD is scalableand reliable. In order to achieve the optimal performance of mapping system, itproposed the optimization design problem which includes the space partition and assignment of matching relationship between logical nodes and physical nodes. Basedon the given lookup traffic matrix, it presented mathmatical programming method andgenetic method to solve the optimization problem.4. In chapter four, the author investigated the traffic locality problem and gatewayselection problem of hierarchical DHTs. It proposed a tree-tier hierachical DHTatchitecture, the top hierachy is the global overlay, its function is to receive anddisseminate infromation; the middle hierachy consists of manager nodes which managethe corresponding group of participanting nodes, here, the granularity of group could bean AS or an ISP; the lower hierachy consists of groups and the participanting nodes ofgroup are connected with three manners: full-meshed, center-based and DHT-basedrespectively. It also proposed three gateway selection algorithms to satisfy differentsystem requirements.5. In chapter five, the author investigated the lookup efficiency of Chord, the workproposed the multi-topology method to divide Chord ring into many small sub-ringsbased on some rules. This multi-topology structure can use parallel lookup method toimprove lookup efficiency of system.6. In chapter six, the author investigated the reliability and fairness of DHTs. Thework studied the ’loss rate’ metric which has tightly relationship with sytem reliability;Furthermore, it proposed the optimization model between nodes’ processing power andsystem performance. It proved that in the homogeneous P2P network, if the size of zonemaintained by each node is equal, the system can acheive the optimal fairness with theuniform or random lookup traffic distribution. It also proposed two mechanisms forimproving the system reliability of heterogeneous and homogeneous networks.7. In chapter seven, the author made a conclusion of this thesis and look forward tofuture research.