The computer input/output (I/O) subsystem and its functioning are very abstract concepts that are difficult for undergraduate freshmen to understand. However, it is important that freshmen assimilate these low-level concepts if they are going to be taught about the operating systems (OS) working over that architecture layer, or working directly with them in embedded systems, real-time systems, or in the area of human--computer interaction (HCI). This article describes the use of a game console (Nintendo® DS, NDS) in a project-based learning (PBL or PjBL) environment in which the design of a game is the basis of the project in order to encourage the students to get more involved with the computer I/O subsystem abstraction. A 4yr experience is reported in which the action research model (planning, acting, observing, and reflecting) has been followed. The general procedure for the 4yr and the specific characteristics and achieved results for each year are reported. The aim of the study was twofold: to assess the learning effectiveness of the active PjBL educational approach and some related factors, and to analyze the motivation toward the subject fostered by the game console. The first aim is analyzed using the scores achieved by the students; the second aim is analyzed via satisfaction questionnaires.

This paper presents an evaluation of three communication-efficient algorithms implementing the Omega class of failure detectors, which provides an eventual leader election functionality, in distributed systems where processes can crash and recover. Communication efficiency means that eventually only a correct process, i.e., the elected leader, keeps sending a message periodically to the rest of processes. The first algorithm relies on the use of stable storage to store the identity of the leader and an incarnation number. The second algorithm does not use stable storage, but requires a majority of correct processes. Also, it is near-communication-efficient, since besides the leader, unstable processes, i.e., those that crash and recover infinitely often, may send messages periodically before they receive a message from the leader. Finally, the third algorithm does neither use stable storage nor require a majority of correct processes, but assumes that each process has access to a nondecreasing and persistent local clock. Using the OMNeT++ network simulation framework, we evaluate the performance and the quality of service provided by these algorithms, in terms of the number of messages exchanged among processes and the capability of the failure detector to provide a single leader, respectively.

Being the Input/Output subsystem an important topic in the area of Computer Architecture [1], in this work we propose a Project-Based Learning (PBL) methodology enhanced by the use of a Nintendo® DS machine. The use of both, methodology and platform, is endorsed by students' comments, the projects themselves and the scores obtained in the subject.

We present a modular redesign of TrustedPals, a smart card-based security framework for solving Secure Multiparty Computation (SMC). Originally, TrustedPals assumed a synchronous network setting and allowed to reduce SMC to the problem of fault-tolerant consensus among smart cards. We explore how to make TrustedPals applicable in environments with less synchrony and show how it can be used to solve asynchronous SMC. Within the redesign we investigate the problem of solving consensus in a general omission failure model augmented with failure detectors. To this end, we give novel definitions of both consensus and the class \diamond {\cal P} of failure detectors in the omission model, which we call \diamond {\cal P}({ om}), and show how to implement \diamond {\cal P}({ om}) and have consensus in such a system with very weak synchrony assumptions. The integration of failure detection and consensus into the TrustedPals framework uses tools from privacy enhancing techniques such as message padding and dummy traffic.

No abstract available.

This paper presents an evaluation of several communication-optimal algorithms implementing the diamP class of failure detectors. The first algorithm is based on a reliable broadcast primitive, involving a quadratic number of messages to manage a suspicion. The second algorithm uses exclusively one-to-one communication, involving a linear number of messages to manage a suspicion, but with a higher latency to propagate the suspicion to the rest of processes. A third algorithm reduces this latency using an additional one-to-all communication mechanism. We evaluate the quality of service provided by these algorithms, in terms of the capability of the failure detector to provide right answers and the reaction time after a failure.

No abstract available.