Generally, tasks in a distributed system must reach agreement. This requires a set of processors to agree on a common value even though some components may be corrupt. There have been several significant studies on this agreement problem in regularized network environments such as the fully connected, broadcast and multicast networks. Recently, many large complex networks have emerged displaying a scale-free feature that influences the system to reach a common value in a novel way. This unanimity problem is called Byzantine agreement (BA). The BA problem is one of the most significant problems in designing a fault-tolerant distributed system. Unfortunately, existing BA protocols cannot cope with the new network environment, and the BA problem thus must be revisited. In this paper, a new BA protocol is proposed that adapts to the scale-free network (SFN) environment and derives its limit of allowable faulty components while maintaining the minimum number of message exchanges. The correctness and complexity of this protocol have been proved. It is observed that an SFN in conjunction with the proposed agreement protocol can tolerate the maximum number of faulty components.

The integration of people devices and services through the use of Machine-to-Machine technology has been, and will continue to be for the foreseeable future, an important economic trend. Mobile video services have become more convenient with respect to mobility, but the quality of the video they produce is limited. In this study, an integrated video service framework “DMCT-S” based on Machine-to-Machine communications is proposed, in which a mobile video service can be integrated into a home video service. In the integrated framework, people can easily watch a low-quality video from a mobile service and transfer the video playing context to another video service to continue the twin high-quality video with same content played in a smart home. This seamless and integrated framework results in vastly increased people convenience.

Fault-tolerance is an important research topic in the study of distributed systems. To cope with the influence of faulty components, reaching a common agreement in the presence of faults before performing certain tasks is essential. However, the Byzantine Agreement (BA) problem is a fundamental problem in fault-tolerant distributed systems. In previous studies, protocols dealing with the BA problem focused on static networks; however, these do not perform well in dynamically changing mobile networks. The most well known mobile network is the Mobile Ad-hoc Network (MANET). To enhance fault-tolerance and MANET reliability, the BA problem in virtual subnets of MANET is revisited in this paper. The proposed protocol is called the Hybrid Agreement Protocol (HAP). It achieves agreement on a common value among all functional mobile processors in a minimal number of message exchange rounds, and can tolerate a maximal number of allowable faulty components in the virtual subnet of MANET.

The fault-tolerance is an important research topic in the study of distributed systems. To cope with the influence from faulty processors, reaching a common agreement in the presence of faults before performing certain special tasks is essential. Therefore, the Byzantine Agreement (BA) problem has drawn more researcher attention as they explore deeper into the world of distributed systems. Traditionally, the BA problem is solved in a wired network. However, the mobile computers have become increasingly popular. This environment encourages distributed system design and practices that support mobile processors. A mobile ad-hoc network (MANET) is different from a wired network. The processors have high mobility. Therefore, to enhance fault-tolerance and MANET reliability, the BA problem in virtual subnet of MANET is revised in this paper. The proposed protocol uses a minimum number of message exchange rounds and can tolerate the maximum number of allowable faulty components and make each fault-free processor reach a common agreement in the virtual subnet of MANET

Mobile ad-hoc network (MANET) is practical more and more due to it can provide processor joins to the network or leaves away anytime with non-infrastructure. Further, the fault-tolerance and reliability of the MANET has also been an important topic. The problem of reaching agreement in the distributed system is one of the most important issues to design a fault-tolerance system. In previous works, reach a common agreement among correct processors to cope with the influence from faulty components is significant in a fault-tolerance system. In this paper, the agreement problem is revisited in a MANET, which the processors maybe subject to malicious failure

In recent years, network bandwidth and quality has been drastically improved in a speed even much faster than the enhancement of computer performance. Various communication and computing tasks in the fields can be integrated and applied in a distributed system in nowadays. However, those resources are heterogeneous and dynamic in distributed systems connecting a broad range of resources. This study proposed a hybrid load balancing policy to maintain performance and stability of distributed system

The Byzantine agreement (BA) problem has been widely discussed in the literature concerned. Most BA protocols can reach a common agreement by way of fault masking. However, in a highly reliable fault-tolerant distributed system, just reaching a common agreement is not enough. We need to take into consideration another related problem called the fault diagnosis agreement (FDA) problem. The goal of solving the FDA problem is to make each fault-free processor detect/locate the common set of faulty components in the distributed system. We shall solve the FDA problem with the dual failure mode over a multicasting network system. The proposed FDA protocol can detect/locate the maximum number of faulty components with the dual failure mode to solve the FDA problem in a synchronous multicasting network

Traditionally, it is very important to deliver data secretly and at low cost in a distributed environment. Using a reliable method to assist in communicating with each other needs to be discussed. Thus, we propose the two-phase agreement (TPA) protocol to solve those problems by verifying the received messages and achieve the agreement. The TPA protocol will assist the organization in achieving agreement and generate a common key to verify it. Similarly, there are many faults and attacks in the network, such as interruption, interception, modification and fabrication. The messages from a source might be changed. However we can use the TPA protocol to remove these faulty influences. The proposed TPA protocol doesn't only decrease the complexity of messages but also increases the capability of fault tolerance. Similarly, it is more reliable via the secret key in a real distributed system. This protocol can solve the agreement problem in net-meeting between arbitrary processors, like sub-company communication with the main-company or makes a decision in the company conference.

Under many circumstances, reaching a common agreement in the presence of faulty components is the central issue of fault tolerant distributed computing. So the Byzantine agreement (BA) problem has become more and more important in distributed systems. Traditionally, the BA problem was visited in a fully connected network (FCN), broadcasting network (BCN) and generalized connected network (GCN). Subsequently, malicious fault assumption with processors or communication media was extended to a hybrid fault model on both processors and communication media. However, the network structures (topologies) of FCN, BCN and GCN are not practical. In this study, we lighten restrictions of the network structure to revisit the BA problem with multicasting network (MCN). The proposed protocol uses the minimum number of rounds of message exchange and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach a common agreement in an MCN.

Previously, most Byzantine Agreement protocols could reach an agreement by way of fault masking. Few of them can detect and locate the faulty components. On the other hand, most fault diagnosis algorithms can detect and locate faulty components but few of them can make all fault free processors reach an agreement. The study analyses the messages received at the period of reaching agreement, and then detects and locates the faulty components of the network. Finally, the proposed protocol can further make all fault free processors agree on the common failure report of the synchronous connected network. The symptoms of the faults include the malicious fault and the dormant fault.

Traditionally, the consensus problem was solved in a fully connected network with node failure assumption. The link failure was unfairly treated as node failure. The paper revisits the consensus problem with the assumption of link failure on dormant faults and malicious faults. A simple and efficient protocol is proposed. The complexity of information exchange required by the protocol is O(n/sup 2/). The protocol uses a minimum number of rounds to achieve a consensus and can tolerate a maximum number of allowable faulty components.

Traditionally, the Byzantine Agreement (BA) problem is studied either in a fully connected network or in a broadcast network. A generalized network model for BA is proposed in this paper. A fully-connected network or a broadcast network is a special case of the new network architecture. Under the new generalized network model, the BA problem is reexamined with the assumption of malicious faults on both processors and transmission medium (TM), as opposed to previous studies which consider malicious faults on processors only. The proposed algorithm uses the minimum number of message exchanges, and can tolerate the maximum number of allowable faulty components to make each healthy processor reach a common agreement for the cases of processor failures, TM failures, or processor/TM failures. The results can also be used to solve the interactive consistency problem and the consensus problem.>

Traditionally, the problems of Byzantine agreement, consensus, and interactive consistency are studied in a fully connected network with processors in malicious failure only. Such problems are reexamined with the assumption of malicious faults on both processors and links. The proposed protocols use the minimum number of message exchanges and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach a common agreement for the cases of processor failure, link failure, or processor and link failure.>