An Architecture For Computational Grids Based On Proxy Servers P. V. C. Costa, S. D. Zorzo, H. C. Guardia {paulocosta,zorzo,helio}@dc.ufscar.br UFSCar  Federal University of Sªo Carlos, Brazil Abstract The Computational Grid concept allows for large-scale resource sharing. The implementation of Grid environments relies on the existence of a communications infrastructure and efficient resource management. Access control and secure communication are also required. Architectures to support Computational Grids can be developed in a variety of ways. This work presents an approach to create a Grid architecture based on Proxy Servers. This approach is in- tended to offer transparency and easy lightweight deployment architecture. 1. Introduction The advances attained in data communication and the popularization of the Internet serve as the basis for a new, less centralized approach aimed at achieving greater computational power. The discovery that the majority of the more than 400 million computers around the world are inactive most of the time [1] has moti- vated the creation of a distributed and shared architec- ture aimed at taking advantage of this potential. This architecture became known as Grid, an analogy of the energy distribution nets [2] involving generating re- sources and consumers interlinked through a distribu- tion net. Similarly, the computational Grid is a hardware and software infrastructure interlinking computational capacity and making its resources available for use. The infrastructure of a Computational Grid should sup- ply basic services for control, communications and se- cure sharing among the Grids resources. Because this computational structure is highly distributed, shared, and sometimes interlinked through a public data com- munications channel, security is also a crucial issue. Grid design involves the use of distributed computa- tional resources for the solution of specific problems. The development of an infrastructure for the implemen- tation of general purpose Grids is also discussed in pro- jects such as [3], [4]. The purpose of the work reported on here is to develop a basic and expandable infrastructure for Grid Comput- ing that allows for the introduction of a new Proxy server-based approach. Based on the layer model, this architecture provides the grids basic communication, security, control and monitoring services. Added to these characteristics is the distributed programming interface support  Message Passing Interface (MPI) [5], which is simple and transparent. The strong points of the architecture are its transparency, simple use and low interference in the installed base. As a result, a new architecture is sought to foment research in the area and to serve as the basis for future work developed within the ambit of Grid Computing, including distributed thread support, load balancing mechanisms, and distrib- uted filing systems. The first phase of the design consists of creating a basic layered infrastructure, serving as the basis for the sub- sequent phases of the design that complete the architec- ture. The functions predicted for the initial phase are:  Authentication: the host is authenticated through digital certificates along with user authentication based on userID and password;  Secure Communication: communication between sites is safe and transparent using the SSL protocol, which allows for tunneling of traffic between sites, re- gardless of the application used;  MPI Support: greater advantage can be taken of the MPI applications through this architecture, since they can be executed using machines and clusters spread around several sites, without the need for alteration of the application code or for installation of new com- munication tools, thereby ensuring transparency and greater availability and utilization of resources to the user. Section 2 presents and discusses the proposed architec- ture and the layer modeling of its modules, while sec- tion 3 describes the functions developed in the first phase of the design and section 4 outlines our initial conclusions.