Software reliability and dependability: a roadmap

Shifting the focus from software reliability to user-centred measures of dependability in complete software-based systems. Influencing design practice to facilitate dependability assessment. Propagating awareness of dependability issues and the use of existing, useful methods. Injecting some rigour in the use of process-related evidence for dependability assessment. Better understanding issues of diversity and variation as drivers of dependability. Bev Littlewood is founder-Director of the Centre for Software Reliability, and Professor of Software Engineering at City University, London. Prof Littlewood has worked for many years on problems associated with the modelling and evaluation of the dependability of software-based systems; he has published many papers in international journals and conference proceedings and has edited several books. Much of this work has been carried out in collaborative projects, including the successful EC-funded projects SHIP, PDCS, PDCS2, DeVa. He has been employed as a consultant t

Safety Critical Wide Area Network Performance Evaluation

The growing importance of real-time computing in numerous applications poses problems for network architectures, especially safety-critical Wide Area Networks (WANs). Assessing network performance in safety-critical real-time systems is difficult, and suggests the use of both human and technical performance criteria because of the importance of both dimensions in safety-critical settings. This research proposes a model that considers both technical and human performance in network evaluation

Comparison Analysis Of Recovery Mechanism At Mpls Network

Multi-protocol Label Switching (MPLS) has become an attractive technology of choice for Internet backbone service providers.  MPLS features the ability to perform traffic engineering and provides support for Quality of Service traffic provisioning. To deliver reliable service, MPLS requires a set of procedures to provide protection for the traffic carried on Label Switched Paths (LSP). In this case Lable Switched Routers (LSRS) supports recovery mechanism when failure happened in the network.This paper studied about performance from usage of different techniques that can be used to reroute traffic faster then  the current IP rerouting methods in the case of a failure in a network. Local rerouting, fast reroute one to one backs up, Haskin, PSL oriented path protection and 1+1 path protection recovery mechanism was compared by given of aggregate traffic which has self-similarity character. Packet drop, rejection probability, recovery time, service disruption time and pre-reserved resources backup will be made as comparator parameter with various bitrate and different position of link failure. Packet loss, rejection probability, recovery time and service disruption time at five recovery mechanisms influenced by position of link failure to ingress. 1+1 path protection mechanism has least packet drop, but costliest way to do recovery in the case of usage resources, as traffic is sent simultaneously in two paths which disjoint. Fast reroute one to one backup is quickest way to operate protection switching recovery after 1+1 path protection mechanism. Keywords: MPLS, recovery, rerouting, self-similar traffic, protection switchingDOI:http://dx.doi.org/10.11591/ijece.v1i2.8

Quantifying Influence of Strategies and Network Properties in Repairing Simultaneous Failures in Smart Grid

The behavior of networks under simultaneous failures has beensubject to various studies in the field of network science. However, themeasures used do usually not take into account the peculiarities of thestudied network. In this paper, we introduce a new measure for powergrids based on the balancing of power and on the accumulated cost ofenergy not supplied (CENS) during an outage. With the help of thismeasure we quantify the performance of seven repair strategies. We findthat both the choice of the right strategy and the topology of the powergrid has a major influence on the outage cost and the survivability ofthe power grid. Additionally, we appraise the potential of smart gridservices and conclude that both distributed energy resources (DER) anddemand response (DR) has a large potential to reduce the cost of anoutage

The Architecture of Complexity Revisited: Design Primitives for Ultra-Large-Scale Systems

As software-intensive systems continue to grow in scale and complexity the techniques that we have used to design and analyze them in the past no longer suffice. In this paper we look at examples of existing ultra-large-scale systems—systems of enormous size and complexity. We examine instances of such systems that have arisen spontaneously in nature and those that have been human-constructed. We distill from these example systems the design primitives that underlie them. We capture these design primitives as a set of tactics— fundamental architectural building-blocks—and argue that to efficiently build and analyze such systems in the future we should strongly consider employing such building-blocks

Gateway selection in multi-hop wireless networks

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 61-63).This thesis describes the implementation of MultiNAT, an application that attempts to provide the benefits of client multi-homing while requiring minimal client configuration, and the evaluation of a novel link-selection algorithm, called AvMet, that significantly outperforms earlier multi-homing methods. The main motivation behind MultiNAT is the growing popularity of cheap broadband Internet connections, which are still not reliable enough for important applications. The increasing prevalence of wireless networks, with their attendant unpredictability and high rates of loss, is further exacerbating the situation. Recent work has shown that multi-homing can increase both Internet performance as well as the end-to-end availability of Internet services. Most previous solutions have required complicated client configuration or have routed packets through dedicated overlay networks; MultiNAT attempts to provide a simpler solution. MultiNAT automatically forwards connection attempts over all local interfaces and uses the resulting connection establishment times along with link-selection metrics to select which interface to use.(cont.) MultiNAT is able to sustain transfer speeds in excess of 4 megabytes per second, while imposing only an extra 150 microseconds of latency per packet. MultiNAT supports a variety of link-selection metrics, each with its own strengths and weaknesses. The MONET race-based scheme works well in wired networks, but is misled by the unpredictable nature of wireless losses. The ETT metric performs relatively well at finding high-throughput paths in multi-hop wireless networks, but can be incorrect when faced with heavy load. Unfortunately, neither of these metrics address end-to-end performance when packets traverse both wired and wireless networks. To fill this need, we propose AvMet, a link-selection scheme that tracks past connection history in order to improve current predictions. We evaluate AvMet on a variety of network configurations and find that AvMet is not misled by wireless losses. AvMet is able to outperform existing predictors in all network configurations and can imp:rove end-to-end availability by up to half an order of magnitude.by Rohit Navalgund Rao.M.Eng