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We have to reduce the total electrical power consumption in information systems. In this paper, we consider communication based applications where a server transmits a large volume of data to a client like file transfer protocol (FTP). We discuss a power consumption model for communication-based applications, where the total power consumption of a server depends on the total transmission rate and number of clients where the server concurrently transmits files. A client has to select a server in a set of possible servers, each of which holds a file, so that the power consumption of the server is reduced. We evaluate a pair of PCB (power consumption-based) and TRB (transmission rate-based) algorithms to select a server. In the evaluation, we show the total power consumption can be reduced by the PCB and TRB algorithms compared with the traditional round-robin (RR) algorithm and PCB is more practical than TRB.

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In peer-to-peer (P2P) applications like computer supported cooperative work (CSCW), multiple peer processes are required to cooperate to make a global decision, e.g. fix a meeting schedule of multiple persons. We discuss how multiple peer processes make a decision to achieve some objectives in a peer-to-peer (P2P) overlay network. Here, every process is assumed to be peer and autonomous. That is, there is no centralized coordination. A domain of a process is a collection of possible values which the process can take. Each process first takes a value v in its domain and notifies the other processes of the value v. A process can change the value with another value on receipt of values from other processes. However, a process can take only some value depending on the value v. For example, a process may abort after notifying commit but cannot commit after notifying abort in the commitment control. An existentially (E)-precedent relation shows what values a process can take after taking a value. In addition, a process takes a more preferable value if the process can take one of multiple values. Thus, values are ordered in the preferentially (P)-precedent relation. Based on the E-and P-precedent relations, each process takes the most preferable one in the values which can be changed from the current value v. In this paper, we discuss how every process makes an agreement on a value while each process can change the value according to the relations. In this paper, we discuss a coordination protocol in a type of heterogeneous system where every pair of processes have different E-precedent relation and P-precedent relation on the same domain. Each process learns a part of the precedent relations of another process through exchanging values.

It is now critical to reduce the consumption of natural resources, especially petroleum. Even in information systems, we have to reduce the total electrical power consumption. We classify network applications to two types of applications, transaction and communication based ones. In this paper, we consider communication based applications like the file transfer protocol (FTP). A computer named server consumes the electric power to transfer a file to a client depending on the transmission rate. We discuss a model for power consumption of a data transfer application which depends on the total transmission rate and number of clients to which the server concurrently transmits files. A client has to find a server in a set of servers, each of which holds a file so that the power consumption of the server is reduced. We discuss a pair of algorithms PCB (power consumption-based) and TRB (transmission rate-based) to find a server which transmits a file to a client. In the evaluation, we show the total power consumption can be reduced by the algorithms compared with the traditional round-robin algorithm.

In a decentralised system like P2P where each individual peers are considerably autonomous, the notion of mutual trust between peers is critical. In addition, when the environment is subject to inherent resource constraints, any efficiency efforts are essentially needed. In light of these two issues, we propose a novel trustworthy-based efficient broadcast scheme in a resource-constrained P2P environment. The trustworthiness is associated with the peer's reputation. A peer holds a personalised view of reputation towards other peers in four categories namely SpEed, Correctness, qUality, and Risk-freE (SeCuRE). The value of each category constitutes a fraction of the reliability of individual peer. Another factor that contributes to the reliability of a peer is the peer's credibility concerning trustworthiness in providing recommendation about other peers. Our trust management scheme is applied in conjunction with our trust model in order to detect malicious and collaborative-based malicious peers. Knowledge of trustworthiness among peers is used in our proposed broadcast model named trustworthy-based estafet multi-point relays (TEMPR). This model is designed to minimise the communication overhead between peers while considering the trustworthiness of the peers such that only trustworthy peer may relay messages to other peers. With our approach, each peer is able to disseminate messages in the most efficient and reliable manner.