Weinong Wang

BiChord: an improved approach for lookup routing in chord

Efficient resource lookup is essential for peer to peer networks and DHT (Distributed Hash Table) provides an ideal solution for resource lookup in distributed networks. Chord is a representative peer to peer lookup service based on DHT. The topology of Chord is modeled as a directed graph. There is a unidirectional link from a node to its every routing table entry node. In this paper, we propose to model the topology of Chord as a bidirectional graph. A reverse link is added for each original unidirectional link and such a pair of symmetrical links is maintained by a single heart-beat message. Then each node should maintain a finger table and a reverse finger table at very little additional cost. However, such reverse fingers may help to improve the lookup efficiency greatly. Theoretical analyses and experimental results both approve such improvements.

Fully decentralized DHT based approach to grid service discovery using overlay networks

Distributed hash table (DHT) is widely used in peer-to-peer networks for its scalability, adaptability, and fault-tolerance in large and dynamic environments. In this paper, we study on the application of DHT for grid service discovery. Grid service is represented by multiple (attribute, value) pairs. The virtual organization (VO) is also self-organized into a 2-dimensional network overlays - one for attributes, and the other for values - as nodes join and publish services in the VO. Service discovery in a VO is firstly directed to the attribute overlay to find the nodes with the discovered attributes, then to the value overlay until the nodes which have the same (attribute, value) are reached. Gateway servers are deployed on the border to interconnect different VOs. The service discovery request can be redirected to other VOs in case that there is no provider in the requesters own VO. Our approach is highly efficient, scalable and quick responsive.

A Multiobjective Optimization Algorithm for LSP Setup in Diffserv and MPLS Networks

In this paper, a multiobjective optimization QoS-aware path selection algorithm is proposed for LSPs setup in DiffServ-MPLS networks. We simultaneously optimize multiple QoS objectives by a genetic algorithm in conjunction with concept of Pareto dominance. Simulation demonstrates that the proposed algorithm is capable of discovering a set of QoS-aware near optimal paths within in a few iterations. In addition, simulation results also very promising indicates scalability of the algorithm with increasing number of network nodes.

A fully decentralized approach to grid service discovery using self-organized overlay networks

Self-organized overlay is widely used in Peer-to-peer (P2P) networks for its scalability, adaptability, and fault-tolerance in large and dynamic environments. In this paper, we propose a fully decentralized approach, DGSD(Decentralized Grid Service Discovery) for Grid service discovery. DGSD makes use of the underlying P2P overlay network protocols to self-organize nodes and services in the Grid. In DGSD, Grid service is represented by (attribute, value) pairs, and the Grid community, named virtual organization (VO), is self-organized into 2-dimensional overlay networks. One for attributes, and the other for values. Service discovery request in a VO is firstly directed to the attribute overlay network to find the servers with the searched attributes, then to the value overlay until the servers which have the same (attribute, value) pairs are reached. The architecture of DGSD supports interactions between VOs. Our approach is highly efficient, scalable and quickly responsive.

Text-Based p2p content search using a hierarchical architecture

As a scalable alternative to traditional server-based architecture, peer-to-peer (P2P) computing has become a popular distributed computing paradigm. However, efficient content search is absent, which hinders the wider deployment of the peer-to-peer systems. Earlier peer-to-peer systems such as Napster and Gnutella suffer from unscalability. Structured peer-to-peer networks achieve good scalability and high reliability, and yet they can only support a single-key based lookup instead of content search by means of DHTs (Distributed Hash Tables). In this paper, we propose a text-based peer-to-peer content search solution, which uses a hierarchical architecture. The heterogeneity of the popularity of terms both in documents and queries and the heterogeneity of hosts are both examined herein. There some techniques are employed to cope with the troubles arising from these heterogeneities. The experimental results show that the solution is feasible and efficient.

Cost management based security framework in mobile ad hoc networks

Security issues are always difficult to deal with in mobile ad hoc networks. People seldom studied the costs of those security schemes respectively and for some security methods designed and adopted beforehand, their effects are often investigated one by one. In fact, when facing certain attacks, different methods would respond individually and result in waste of resources. Making use of the cost management idea, we analyze the costs of security measures in mobile ad hoc networks and introduce a security framework based on security mechanisms cost management. Under the framework, the network system’s own tasks can be finished in time and the whole network’s security costs can be decreased. We discuss the process of security costs computation at each mobile node and in certain nodes groups. To show how to use the proposed security framework in certain applications, we give examples of DoS attacks and costs computation of defense methods. The results showed that more secure environment can be achieved based on the security framework in mobile ad hoc networks.

Adaptive improving forward-link soft handoff performance in power-controlled DS-CDMA cellular networks

In this paper, we propose an adaptive guard capacity scheme for soft handoff calls by means of a predictive multiple access interference (MAI) temporal structure, so as to improve soft handoff users performance simultaneously with an acceptable QoS guarantee for ongoing users. Furthermore, we apply feedback control methodology to formulate the adaptive guard capacity adjustment as an adaptive real-time control problem. Performance evaluation reveals that the solution not only has excellent stability behavior, but also meets zero steady state error and settling time requirements. And simulation results also indicate that our adaptive guard capacity scheme can guarantee the predetermined soft handoff failure probability and new call blocking probability by comparing with conventional fixed guard capacity scheme.

DIRA: distributed insertion and relocation routing algorithm for overlay multicast in diffserv domain

Traditional multicast routing algorithms require routers to be specially designed such that they can forward the same copy of packet onto different output links simultaneously. This idea conflicts severely with the core-stateless principle in most QoS network architectures, such as Diffserv. Meanwhile, overlay multicast emerges as an effective alternative to the traditional approaches. In this paper, we combine the overlay multicast technique with the Diffserv architecture seamlessly and design an overlay multicast routing algorithm, which generates a multicast tree at a pretty low cost incrementally. Owing to its distributed nature, the computation of the tree can be executed efficiently. Through a large amount of simulations, we have shown that our algorithm is quite competitive in terms of network resource utilization and other metrics.

An end-to-end qos provisioning architecture in IPv6 networks

Differentiated Service (DiffServ) is a scalable solution to provide class-based differentiated Quality of Services (QoS). However, the basic DiffServ model lacks mechanisms to reserve resource for the class-based traffic and perform per-flow admission control. In this paper, we propose an end-to-end QoS provisioning architecture in IPv6 networks supported by a QoS-aware path selection algorithm. We design a novel flow label mechanism to achieve the effect of per-flow reservation paradigm and keep the scalability of DiffServ. In addition, the proposed QoS-aware path selection algorithm can optimize multiple QoS objectives simultaneously by exploiting genetic algorithm technique in conjunction with concept of Pareto dominance. The simulation results demonstrate the efficiency and scalability of the proposed architecture and algorithm.

Multimedia Tampering Localization Based on the Perturbation in Reverse Processing

A new fragile watermarking scheme, which exploits the perturbation in reverse processing, is proposed to enhance the tampering localizability of multimedia authentication. In verifying data integrity or authenticating signatures, the new method performs the reverse processing of watermark embedding. Typically, it solves an embedding equation or de-filters the distributed version instead of really extracting the watermark. If any tampering happened, the output of the method perturbs because the manipulated data, which can be regarded as the observation error, is drastically enlarged by such processing. The perturbed values indicate the degree of the tampering, and their positions directly draw the shapes of the manipulated areas. Compared with the mostly used block-based fragile watermarking, the new method localizes the tampering almost sample-wise other than block-wise. It also supports the adaptive embedding, which does not evenly scale the watermark, and avoids the vulnerabilities resulting from the block-based approaches.