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In distributed database systems the global database is partitioned into a collection of local databases stored at different sites. In this era of growing technology and fast communication media, security has an important role to play. In this paper we presented a secure concurrency control protocol (SCCP) based on the timestamp ordering, which provides concurrency control and maintains security. We also implemented SCCP and a comparison of SCCP is presented in three cases (High, Medium and Low security levels). In this experiment, It is observed that throughput of the system decreases as the security level of the transaction increases, i.e., there is tradeoff between the security level and the throughput of the system.

Advancing technology in wireless communication offers users anytime, anywhere access to information and network resources without restricting them to the fixed network infrastructure. Mobile computing represents a shift in the distributed systems paradigm. The potential of decoupled and disconnected operation, location-dependent computation and communication and powerful portable computing devices gives rise to opportunities for new patterns of distributed computation that require a revised view of distributed systems. Mobile environment brings different challenges to users and service providers when compared to fixed, wired networks. Mobility brings uncertainties, as well as opportunities to provide new services and supplementary information to users in the locations where they find themselves. A mobile user is one who, on occasion, disconnects from his/her home network to change location and then reconnects, possibly using a different access technology. A necessary feature of mobility management is the ability to continue to provide system and network services to mobile users seamlessly, regardless of their location and the form of their connection. In general, most application software, operating systems and network infrastructures are intended for more conventional environments and so the mobile user has great difficulty in exploiting the computational infrastructure as fully as he/she might. The Internet Roaming solution for corporate wireless data users integrates mobile networking across private wireless local area networks (WLANs), public WLANs and cellular data networks. In this study we have developed an infrastructure using mobile agent for integrating the Wireless LAN and cellular data called Internet Roaming System (IRS). It is implemented on PMADE mobile agent system developed at IIT Roorkee.

In order to disperse the load on a Web server, generally the server cluster is configured to distribute access requests, or mirror servers are distributed geographically on different networks. Use of the Internet and the World-Wide-Web (WWW) has become widespread in recent years and mobile agent technology has proliferated at an equally rapid rate to evenly distribute the requests to web servers through load balancing. There are various loads balancing policies came into picture. Primitive one is Message Passing Interface (MPI). Its wide availability and portability make it an attractive choice, however the communication requirements are sometimes inconventior and inefficient when implementing the primitives provided by MPI. Mobile agent (MA) based approach have the merits of high flexibility, efficiency, low network traffic, less communication latency as well as highly asynchronous. In this study we present dynamic load balancing using mobile agent technology in which when a node is overloaded, task migrates to less utilized nodes so as to share the workload. However, the decision of which nodes receive migrating task is made in real-time by design and implementation of a framework called Platform for Load balancing (PLB). It is implemented on PMADE (A Platform for Mobile Agent Distribution and Execution). PLB integrated web servers can dispatch MAs to retrieve load information and accomplish load redistribution on all servers. The performance evaluation demonstrates that the PLB framework provides a foundation to develop efficient load balancing schemes on wide range of web server systems from cluster to open network and the results of a comparison of PLB, with some existing ones, is also reported.

Cluster computing harnesses the combined computing power of multiple processors in a parallel configuration. Cluster Computing environments built from commodity hardware have provided a cost-effective solution for many scientific and high-performance applications. In this paper we have presented design and implementation of a cluster based framework using mobile code. The cluster implementation involves the designing of a server named MCLUSTER which manages the configuring, resetting of cluster. It allows a user to provide necessary information regarding the application to be executed via a graphical user interface (GUI). Framework handles- the generation of application mobile code and its distribution to appropriate client nodes, efficient handling of results so generated and communicated by a number of client nodes and recording of execution time of application. The client node receives and executes the mobile code that defines the distributed job submitted by MCLUSTER server and replies the results back. We have also the analyzed the performance of the developed system emphasizing the tradeoff between communication and computation overhead.

In order to disperse the load on a Web server, generally the server cluster is configured to distribute access requests, or mirror servers are distributed geographically on different networks. Use of the Internet and the World-Wide-Web (WWW) has become widespread in recent years and mobile agent technology has proliferated at an equally rapid rate to evenly distribute the requests to web servers through load balancing. There are various loads balancing policies came into picture. Primitive one is Message Passing Interface (MPI). Its wide availability and portability make it an attractive choice, however the communication requirements are sometimes inconventior and inefficient when implementing the primitives provided by MPI. Mobile agent (MA) based approach have the merits of high flexibility, efficiency, low network traffic, less communication latency as well as highly asynchronous. In this study we present dynamic load balancing using mobile agent technology in which when a node is overloaded, task migrates to less utilized nodes so as to share the workload. However, the decision of which nodes receive migrating task is made in real-time by design and implementation of a framework called Platform for Load balancing (PLB). It is implemented on PMADE (A Platform for Mobile Agent Distribution and Execution). PLB integrated web servers can dispatch MAs to retrieve load information and accomplish load redistribution on all servers. The performance evaluation demonstrates that the PLB framework provides a foundation to develop efficient load balancing schemes on wide range of web server systems from cluster to open network and the results of a comparison of PLB, with some existing ones, is also reported.

Mobile agents can be seen as a new paradigm for distributed computing. One characteristic of mobile agents is their autonomy and pro-activity. This article present a framework designed on top of PMADE (Platform for Mobile Agent Distribution and Execution) to support our research in this domain. Our framework consists of three modules. The Map Module collects information on the available network of agent hosts (AHs) and a mobile agent is able to locate services within the network with the help of this module. Furthermore, the framework provides a Route estimating module and an optimization module, which minimizes network load. These modules support a fast and efficient navigation through the network, which is an environment with an inherently dynamical behavior. The basis for this work is the PMADE Domain Service, which is a hierarchical arrangement of AHs that groups AHs into a federation of networked local clusters, so called domains. This paper also evaluates the basic concepts and the actual modules of the developed framework and made some measurements to characterize the modules quality and to identify problems.