sider the Grid as the new enabling technology to transparently access ... the future users of this new technology. In fact wireless devices, with currently.
An Agent-based Architecture for Mobile Grid Users Dario Bruneo, Antonio Puliafito, Angelo Zaia Dept. of Mathematics, University of Messina Salita Sperone - Contrada Papardo, 98166 Messina, Italy {dbruneo,apulia,azaia}@ingegneria.unime.it
Abstract. This paper wishes to investigate the converging field of mobile and Grid computing by defining a unified, extensible, scaleable and flexible architecture for the provision of Grid secure services. We propose using the mobile agent paradigm in order to develop a middleware layer that takes care of all the details to allow mobile users to access distributed resources in a transparent, secure and effective way. Keywords: GRID computing, mobile agents, QoS, mobile users, wireless systems
1
Introduction
GRID technology [4] is a new paradigm which has the potential to completely change the way of computing and data access. Generally speaking, we could consider the Grid as the new enabling technology to transparently access computing and storage resources anywhere, anytime and with guaranteed Quality of Service (QoS). Although still in its infancy, Grid is already being successfully used in many scientific applications where huges amounts of data have to be processed and/or stored. We do think that the time is right for the Grid to reveal its potentialities to a wider audience, which is mainly constituted of users with every day problems and requirements. Obviously such needs cannot directly compete with the highly demanding scientific applications described so far, but, as the amount of potential users is really enormous, the accumulated data processing and storage requirements are at least comparable. In particular, mobile users might be the future users of this new technology. In fact wireless devices, with currently limited resources, would benefit from the opportunity of using a considerable amount of resources made available by all the other devices connected to the network. Of course, the need for managing the transparency of the service (on the one hand) and the mobility of users (on the other) requires a big initial effort in the creation of a suitable middleware. Mobile agent technology seems the best solution for the creation of this infrastructure. The paper is organized as follows: in section 2 we present the reference scenario for the architecture proposed. In section 3 we describe the relationship between agents and the Grid. The architecture examined is described in section 4. Finally, in section 5 we present the conclusions and the further development.
2
Scenario
Our reference scenario is made of the following main areas: 1. The wired area, i.e. the Internet with the available Grid resources. 2. The wireless area, where mobile users try to access GRID resources through wireless mobile terminals. The wired area is characterized by the presence of Access Points (APs), which allow mobile hosts to connect to the wired infrastructure through wireless links. Mobile hosts are free to change their location without any restriction, while maintaining their connection to the service they are using. The wireless area allows the extension of Grid services to mobile users. In fact, once the AP is reached, all the services on offer can be obtained. One crucial aspect to be addressed regards the new, challenging problems related to the fact that mobile terminals may offer features that may differ a lot from one to another. This impacts both the way in which applications have to be developed and the way they have to be accessed. Static applications are unfit to dynamically adapt to user requirements, to satisfy his/her preferences and match the computational processing power offered by his/her mobile device. New and more stringent Quality of Service (QoS) requirements have to be satisfied, developing new and more sophisticated strategies that also involve programming at the network equipment level [7]. In order for true service portability to be achieved, services need to be offered in partnership between mobile and fixed networks. The theme of mobile personal communications has been anytime, anywhere access. The new problem is, then, anyhow access.
3
Agents and the GRID
In an environment where multiple and different networking infrastructures are involved we plan to use an agent-based management system as an underlying layer to the network model to collect the required management data, distribute and balance the computation inside the network, negotiate and adjust the required and/or feasible levels of security, and maintain a high level of fault tolerance in the system. Smart phones, PDA’s are nowadays normally adopted for accessing to distributed data. Middleware for portable device integration should permit both automatic discover of resources at runtime and support for easy access and utilization of highly heterogenerous components [3]. Middleware solutions should dynamically tailor service provisioning to the specific characteristics of the client access device, which usually exhibits a high heterogeneity of hardware/software capabilities, hosted operating systems, and supported network technologies. An agent-based approach to such kind of problems, as well as introducing flexibility on the fixed part of the network in order to provide more advanced services, will
exploit the mobile agents properties of mobility, asynchronicity and autonomy during service provisioning. Mobile agents will be the underlying enabling technology that we will use in order to develop a powerful middleware which will enhance the fixed networks (and the related Grid services) and extend the infrastructure services only when and where it is needed, without imposing operation suspension.
4
Architecture
In the architecture proposed we expect to use a Grid middleware (Globus) and a mobile agent environment. The Grid middleware is integrated with functions that facilitate the management of data mining and data transfer (Knowledge Grid) [2]. We use a mobile agent environment that manages the user (mobility, profile, etc.) and the issues related with the heterogeneity of the devices. First of all, let us analyze the interfacing between the user (wireless) and the wired zone. A fixed agent (Personal Agent) will be present in every mobile device (PDA, Laptop). The Personal Agent will have the task of managing the wireless device, by monitoring resources (battery, memory, CPU, display, etc.) and position (through GPS, for instance) within the wireless area. When a user enters the wireless area, an agent (User Agent) is created in the corresponding Access Point. This agent will represent the user while he/she remains connected to the network. The User Agent will be able to communicate with the Personal Agent present in the device, in order to obtain all the information needed. Any time the user moves (by changing his/her Access Point) the user agent will follow him/her, by migrating to the new Access Point. The User Agent will therefore act as an intermediary between the mobile device and the Grid resources present in the wired area. As we can see in Fig. 1(a), each node of the Grid network will
(a) Grid Node.
(b) Agent’s interaction. Fig. 1.
consist of a three-level architecture. The lowest one is the level that provides the Grid basic services (resource management, security, distributed access). If the Globus middleware is used, the main services will be: the Globus Resource Management Architecture (GRAM), the Grid Security Infrastructure (GSI), the Grid Information Service (GIS), and the Globus Access to Secondary Storage (GASS). The Data Grid services will be available at a higher level. This is a set of services (based on the Grid services of the lower level) that facilitate the management of distributed data (movement, sharing). If the Globus middleware is used, the main services will be: Storage System (SS), Metadata Repository (MR), and Replica Management (RM). An agent platform containing the Grid Agents will be present at the highest level of the architecture. The task of the Grid Agents will be to respond to the queries coming from the User Agents in order to satisfy the requests. Moreover, the Grid Agents will have the task of managing issues related to the network load balancing and to the availability of the resources. In order to enable the User Agents to reach the Grid Agents present in the network, some Discovery of Services techniques (for instance, Jini [6]) will be used. A representation of the interaction among the entities present in the architecture is shown in Fig. 1(b). According to the needs and the profile of the user, and to the characteristics of the mobile device, the Personal Agent sends a query to its User Agent, through the wireless network. The User Agent starts the Discovery of Service procedure, in order to locate an available Grid Agent in the network. Once a Grid Agent is located, it provides the service required, by using the Grid resources. The Grid Agent - by using the services of the underlying Grid middleware - will balance the load, manage the QoS, and distribute the computation. For this purpose, some code and/or data might need to be moved from one node of the Grid network to another.
5
Conclusion
In this paper we have analyzed the issues related to some users (not linked to the scientific community) exploiting the potential of Grid computing. In particular, our attention has been focused on mobile users, due to the currently limited resources available to them. An architecture based on mobile agents has been presented. This architecture can manage the transparency of the access to the distributed services on the one hand, and the user’s mobility on the other. We are now going to implement this architecture, by using advanced Access Points equipped with 802.11b wireless cards based on the Linux operating system [1]. Such Access Points are equipped with the MAP agent platform [5]. More attention will also be focused on interfacing the agent platform present in Grid nodes with the services made available by the Globus middleware.
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