The transmission of data flows in current networks is in a scattered and disordered state, which makes it difficult to effectively discover and defend against network attacks in a timely manner, ...while network managers lack the tools for the secure and orderly management of data flows. To solve this problem, a secure data flow forwarding method based on service ordering management is proposed in this paper. By defining the service header, the scheme realizes a fine-grained service-based division of data flows. The rules for services in the network are formulated, and orderly control over data flows based on the rules is implemented through the software-defined network architecture, such that only data flows meeting the rules are allowed to pass through the network. Meanwhile, to achieve secure data flow forwarding, data flow is signed, and the signature fields are sampled and verified on the forwarding device to ensure the correctness and tamperproof nature of the data flow forwarding process. The experimental results reveal that the proposed method based on service ordering management can achieve fine-grained and orderly secure data flow control forwarding, effectively defending against network attacks and improving network security. Furthermore, the additional forwarding delay introduced by the scheme is in the controllable range, making the approach practical.
•This paper describes through structured analysis e-waste management systems in Mexico near the US-Mexico border.•Market requirements of materials determine the way they are handled.•Regulatory ...legislation is only one of many factors that are important in the disposal of e-waste.•It is important to include this diversity when designing policies for managing the disposal of computers.
Currently, around the globe, environmental and social problems derive from the inappropriate recycling of electronic products. Moreover, improper recycling is not the only issue to address in electronic products. Others include: energy intensity in their manufacture, employment generation related to the international trade in used electronics, and access to technology by low-income communities. Nevertheless, policies and controls created to provide socially and environmentally sound management of used electronics do not match the complexity of the system. In order to understand the e-waste system, particularly used computers, as a whole, a field study was done between 2010 and 2011 in ten Mexican cities. Ninety-five diverse stakeholders were interviewed to uncover factors regarding the decision to waste or trade still-usable computers. Structured analysis was used to create Data Flow Diagrams (DFDs) to describe the critical parts of the system. The results show that perceived value and geographical location determine the rate in which computers are disposed and the opportunities to waste or trade them, including the trade of their materials. Among businesses and other organizations, legislation has a stronger effect. Technological change is another important factor, largely driving the change in materials and new products. Designing policies responding to this diversity may prevent unforeseen problems and stimulate solutions.
The steady-state performance of a bulk transfer TCP flow (i.e., a flow with a large amount of data to send, such as FTP transfers) may be characterized by the send rate, which is the amount of data ...sent by the sender in unit time. In this paper we develop a simple analytic characterization of the steady-state send rate as a function of loss rate and round trip time (RTT) for a bulk transfer TCP flow. Unlike the models of Lakshman and Madhow (see IEE/ACM Trans. Networking, vol.5, p.336-50, 1997), Mahdavi and Floyd (1997), Mathis, Semke, Mahdavi and Ott (see Comput. Commun. Rev., vol.27, no.3, 1997) and by by Ott et al., our model captures not only the behavior of the fast retransmit mechanism but also the effect of the time-out mechanism. Our measurements suggest that this latter behavior is important from a modeling perspective, as almost all of our TCP traces contained more time-out events than fast retransmit events. Our measurements demonstrate that our model is able to more accurately predict TCP send rate and is accurate over a wider range of loss rates. We also present a simple extension of our model to compute the throughput of a bulk transfer TCP flow, which is defined as the amount of data received by the receiver in unit time.
Purpose
The purpose of this paper is to investigate a systematic methodology to manage asset data flow between building stakeholders throughout building life cycle using the Construction Operation ...Building Information Exchange (COBie) standard.
Design/methodology/approach
A literature review of the relevant building information modelling (BIM) for facilities management (FM) studies including the gaps and challenges of producing COBie data is analysed. Then a standard project management methodology by Project Management Institute (PMI) is introduced as a theoretical framework to map the different areas of managing COBie data as a project in coordination with Royal Institute of British Architects (RIBA) Plan of work. This theoretical background is coupled with an inductive approach through the placement within a construction company (Bouygues, UK) in the UCLH construction project to produce the conceptual framework that is aligned with industry needs.
Findings
The lack of well-structured approach to manage COBie data throughout building life cycle causes many problems and confusions about the roles and responsibilities of different stakeholders in creating and managing asset data. This confusion in turn results in incomplete and low-quality COBie data at the handover phase which hinders the ability of facility managers to use these data effectively in the operations phase. The proposed conceptual framework provides a standard project management process to systemise the data flow among all stakeholders.
Practical implications
The proposed framework is developed in liaison with a large construction company, so it is well aligned with an actual industry approach to managing COBie data. Furthermore, it provides a systematic step-by-step approach to managing COBie as a project that could be easily implemented in actual construction projects.
Originality/value
The paper introduced a novel approach to manage COBie data using a standard project management methodology based on an actual live construction project perspective coupled with project management theory.
In high-level synthesis for real-time systems, it typically employs heterogeneous functional-unit types to achieve high-performance and low-cost designs. In the design phase, it is critical to ...determine which functional-unit type to be mapped for each operation in a given application such that the total cost is minimized while the deadline can be met. For a path or tree structured application, existing approaches can obtain the minimum-cost assignment, called "optimal assignment", under which the resultant system satisfies a given timing constraint. However, it is still an open question whether there exist efficient algorithms to obtain the optimal assignment for the directed acyclic graph (DAG), or more generally, the data-flow graph with cycles (cyclic DFG). For DAGs, by analyzing the property of the problem, this paper designs an efficient algorithm to obtain the optimal assignments. For cyclic DFGs, we approach this problem with the combination of retiming technique to thoroughly explore the design space. We formulate a Mixed Integer Linear Programming (MILP) model to give the optimal solution. But because of the high degree of its time complexity, we devise a practical algorithm to obtain near-optimal solutions within a minute. Experimental results show the effectiveness of our algorithms. Specifically, compared with existing techniques, we can achieve 25.70 and 30.23 percent reductions in total cost on DAGs and cyclic DFGs, respectively.
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