Experience with an Embedded Systems Software Course

In this paper we share our experience with designing and offering a senior undergraduate course on Embedded Systems Software in the Department of Computer Science at the Hong Kong University of Science and Technology. We give a detailed overview of the course, some reflections on our experience with the first offering of the course, followed by some discussion on the students' views of the course

Bringing embedded software closer to computer science students

Computer Science (CS) students have often shied away from the field of embedded systems owing to their perception of this area as 'hardware' oriented, not without reason. But recent trends in embedded systems, with the growing importance of the software component, has brought about new opportunities for computer science students to participate and contribute to embedded system development. In this paper we present our views and experience gained by teaching Computer Science students, on how we can bring embedded systems closer to them, to provide them the opportunity to fully participate in this growing field. We believe that by building on the CS students'strengths, while lessening the emphasis on the 'hardware' aspects, we can still allow them to master sufficient knowledge and skills to participate in this field

Dependability analysis of large-scale distributed systems using stochastic Petri nets

Dependability models of complex distributed systems using Markovian techniques suffer from state space explosion. Several methods for controlling the state space explosion problem have been proposed in the literature. These largeness avoidance methods include state truncation, model composition, behavioral decomposition, time-scale decomposition and fixed-point iteration. In this paper we briefly review these different methods in the context of dependability evaluation of large-scale distributed systems. We use the stochastic reward nets (SRN) as the modelling formalism, and show how the different methods can be implemented using the various structural constructs available within SRN models. We illustrate the application of these methods using an interesting example

A stable queue-based adaptive controller for improving AQM performance

Active queue management (AQM) mechanisms are designed to provide better support for end-to-end congestion control mechanisms of transmission control protocol (TCP) in TCP/IP networks. This paper introduces a stable queue-based adaptive proportional-integral (Q-SAPI) controller for AQM and presents an implementation. The starting points of our approach are the recently developed fluid-flow modeling and control theoretic interpretation of the TCP/AQM dynamics, and the recently developed fixed-gain proportional-integral (PI) controller for AQM. Q-SAPI aims to improve the transient performance of the fixed-gain PI controller while maintaining its steady-state performance over a wide range of uncertainties in round-trip time (RTT) and the number of active TCP flows. The robustness of Q-SAPI is studied in detail, which provides guidelines for selecting control parameters. Through extensive simulations, we demonstrate the ability of Q-SAPI in controlling queue length in both transient and steady states. Q-SAPI achieves this by adapting the controller gains according to the queue length. (c) 2005 Elsevier B.V. All rights reserved

The effects of AQM on the performance of assured forwarding service

Several active queue management (AQM) mechanisms have been proposed in the literature to provide better support for congestion control. However, their performance is examined mainly in best-effort networks. In this paper, we present an empirical study of the effects of AQM mechanisms on the performance of the Assured Forwarding (AF) Service in the non-oversubscribed Differentiated Services networks. The AQM mechanisms to be studied include some existing mechanisms and a new AQM scheme, proposed in this paper. The study is carried out in the cases of the standard traffic conditioner and intelligent traffic conditioners. Extensive simulation results show: (i) when the standard traffic conditioner is employed at the ingress routers, the transient and steady-state behaviors of an AQM scheme in controlling the queue length not only affect the achievement of bandwidth assurance, but also affect the attainment of excessive bandwidth and link throughput; (ii) the behaviors of an AQM affect the ability of an intelligent traffic conditioner in improving bandwidth assurance; (iii) self-tuning AQM schemes perform better than AQMs with fixed-gains in terms of the achievement of bandwidth assurance and link throughput. (c) 2006 Elsevier B.V. All rights reserved

Cost-Effective and Energy-Aware Resource Allocation in Cloud Data Centers

Cloud computing supports the fast expansion of data and computer centers; therefore, energy and load balancing are vital concerns. The growing popularity of cloud computing has raised power usage and network costs. Frequent calls for computational resources may cause system instability; further, load balancing in the host requires migrating virtual machines (VM) from overloaded to underloaded hosts, which affects energy usage. The proposed cost-efficient whale optimization algorithm for virtual machine (CEWOAVM) technique helps to more effectively place migrating virtual machines. CEWOAVM optimizes system resources such as CPU, storage, and memory. This study proposes energy-aware virtual machine migration with the use of the WOA algorithm for dynamic, cost-effective cloud data centers in order to solve this problem. The experimental results showed that the proposed algorithm saved 18.6%, 27.08%, and 36.3% energy when compared with the PSOCM, RAPSO-VMP, and DTH-MF algorithms, respectively. It also showed 12.68%, 18.7%, and 27.9% improvements for the number of virtual machine migrations and 14.4%, 17.8%, and 23.8% reduction in SLA violation, respectively

A Survey of BitTorrent Performance

Since its inception, BitTorrent has proved to be the most popular approach for sharing large files using the peer-to-peer paradigm. BitTorrent introduced several innovative mechanisms such as tit-for-tat (TFT) and rarest first to enable efficient distribution of files among the participating peers. Several studies examining the performance of BitTorrent and its mechanisms have been published in the literature. In this paper, we present a survey of performance studies of BitTorrent from 2003 to 2008. We categorize these studies based on the techniques used, the mechanisms studied and the resulting observations about BitTorrent performance. Many of the performance studies also suggested modifications to BitTorrent's mechanisms to further improve its performance. We also present a survey of the suggested improvements and categorize them into different groups

E2VT: An Effective and Efficient VM-Transparent Mechanism for Preventing TPVM OS Boot Failure

Integrating system-level virtualization technology with Trusted Computing technology can significantly improve system security. The open-source virtual TPM facility, shipped with the open-source hypervisor Xen, aims to provide the illusion of a physical TPM to TPM-based trusted software executed in trusted virtual machines (TVMs) such that TPM-based trusted software works well in a TVM as in a native Operating System (OS). However, it is not true for the trusted software which works in a trusted para-virtual machine (TPVM). The TPM command packets sent in the TPVM OS boot phase may cause the TPVM OS boot failure. This paper design and implement (EVT)-V-2, an effective and efficient mechanism for preventing the TPVM OS boot failure while (1) being transparent to the TPVM system, (2) maintaining the original system performance, (3) making minimal modifications to the existing architecture. We validate our analysis and design through experiments