Internet sharing systems aim at federating and utilizing distributed computing resources across the Internet. This paper presents a user-level virtual machine (VM) approach to MPI program execution in an Internet sharing framework. In this approach, the resource consumer has its own operating system running on top of, and isolated from, the operating system of the resource provider. We propose an efficient socket virtualization technique to optimize VM network performance. Socket virtualization achieves the same network bandwidth as the physical network. In our LAN environment, it reduces the latency overhead from 172 % (using existing TUN/TAP technique) to 35.6%. Performance results on MPI benchmarks show that our virtualization technique incurs small overhead compared with the physical host platform, while gaining in return a higher degree of guest isolation and customization. We also describe the key mechanisms that allow the employment of VMs in an existing Internet sharing system. 1

Computer engineers increasingly depend on the use of software tools to evaluate and investigate the design of computer systems. It is therefore very important that educators in this field promote extensive tool-based experimentation by students. However, the integration of today's complex tools into curricula poses several challenges to instructors. To deploy a tool-based class experiment, they must (1) obtain access to hardware resources that meet the requirements of the tool, and obtain access to student accounts on these resources; (2) install and maintain the tool (software and documentation); (3) develop education content (tutorials, assignments) to be used in class. If many tools are intended to be used throughout the semester, the overheads are magnified in proportion to the number of needed tools. Furthermore, it becomes important to (4) guarantee that tools are presented to students with user-friendly interfaces. This paper describes how these challenges are addressed by a universally accessible NETwork-computer for Computer Architecture Research and Education - NETCARE - that provides educators with a Web portal to access computing resources, executable tools and educational material. This infrastructure has been used in computer architecture and parallel programming classes for three years; the experience obtained from its extensive usage has motivated several improvements in the infrastructure which are described in this paper. In terms of hardware...