15835461
A New Distributed Dynamic Bandwidth Reservation Mechanism to Improve Resource Utilization: Simulation and Analysis on Real Network and Traffic Scenarios
A stationary solar heat collector includes a reflector having a substantially upwardly facing concave reflective surface and an absorber tube supported relative to the reflective surface for receiving reflected sunrays therefrom. The reflective surface is defined in cross-section by first, second and third semi-parabolic curves arranged in generally end-to-end relation, thereby to define a generally C-shape. The reflective surface may be of a shape generated by moving the curves along a line perpendicular to the plane of the curves or approximately of a shape generated by rotating the curves about the free end of the first curve.
164404
New preemption policies for DiffServ-aware traffic engineering to minimize rerouting in MPLS networks
The preemption policy currently in use in MPLS-enabled commercial routers selects LSPs for preemption based only on their priority and holding time. This can lead to waste of resources and excessive number of rerouting decisions. In this paper, a new preemption policy is proposed and complemented with an adaptive scheme that aims to minimize rerouting. The new policy combines the three main preemption optimization criteria: number of LSPs to be preempted, priority of the LSPs, and preempted bandwidth. Weights can be configured to stress the desired criteria. The new policy is complemented by an adaptive scheme that selects lower priority LSPs that can afford to have their rate reduced. The selected LSPs will fairly reduce their rate in order to accommodate the new high-priority LSP setup request. Performance comparisons of a nonpreemptive approach, a policy currently in use by commercial routers, and our policies are also investigated.
18928894
A new traffic engineering manager for DiffServ/MPLS networks: design and implementation on an IP QoS Testbed
In a multi-service network, different applications have varying QoS requirements. The IETF has proposed the DiffServ architecture as a scalable solution to provide Quality of Service (QoS) in IP Networks. In order to provide quantitative guarantees and optimization of transmission resources, DiffServ mechanisms should be complemented with efficient traffic engineering (TE) mechanisms, which operate on an aggregate basis across all classes of service. The MultiProtocol Label Switching (MPLS) technology is a suitable method to provide TE, independent of the underlying layer2 technology. Currently, the combined use of Differentiated Services (DiffServ) and MPLS is a promising technique to provide Quality of Service (QoS), while efficiently exploiting network resources. In this paper, TEAM, an automated manager for DiffServ/MPLS networks is introduced and its design. The design and implementation details are discussed.
16444250
Optimal policy for label switched path setup in MPLS networks
An important aspect in designing a multiprotocol label switching (MPLS) network is to determine an initial topology and to adapt it to the traffic load. A topology change in an MPLS network occurs when a new label switched path (LSP) is created between two nodes. The LSP creation involves determining the route of the LSP and the according resource allocation to the path. A fully connected MPLS network can be used to minimize the signaling. The objective of this paper is to determine when an LSP should be created and how often it should be re-dimensioned. An optimal policy to determine and adapt the MPLS network topology based on the traffic load is presented. The problem is formulated as a continuous time Markov decision process with the objective to minimize the costs involving bandwidth, switching, and signaling. These costs represent the trade-off between utilization of network resources and signaling/processing load incurred on the network. The policy performs a filtering control to avoid oscillations which may occur due to highly variable traffic. The new policy has been evaluated by simulation and numerical results show its effectiveness and the according performance improvement. A sub-optimal policy is also presented which is less computationally intensive and complicated.
44514493
Locating hot nodes and data routing for efficient decision fusion in sensor networks
This paper presents a fundamentally new approach to integrating local decisions from various nodes and efficiently routing data in sensor networks. By classifying the nodes in the sensor field as ''hot'' or ''cold'' in accordance with whether or not they sense the target, we are able to concentrate on a smaller set of nodes and gear the routing of data to and from the sink to a fraction of the nodes that exist in the network. The introduction of this intermediary step is fundamentally new and allows for efficient and meaningful fusion and routing. This is made possible through the use of a novel Markov Random Field (MRF) approach, which, to the best of our knowledge, has never been applied to sensor networks, in combination with Maximum A Posteriori Probability (MAP) stochastic relaxation tools to flag out the ''hot'' nodes in the network, and to optimally combine their data and decisions towards an integrated and collaborative global decision fusion. This global decision supersedes all local decisions, and provides the basis for efficient use of the sensed data. Because of the MRF local nature, nodes need not see or interact with other nodes in the sensor network beyond their immediate neighborhood, which can either be defined in terms of distance between nodes or communication connectivity, hence adding to the flexibility of dealing with irregular and varying sensor topologies, and also minimizing node power usage and providing for easy scalability. The routing of the ''hot'' nodes' data is confined to a cone of nodes and power constraints are taken into account. We also use the found location of the centroid of the hot nodes over time to track the movement of the target(s). This is achieved by using the segmentation at time t as an initial state in the stochastic MAP relaxation at time [email protected]
11805054
A new preemption policy for DiffServ-aware traffic engineering to minimize rerouting
In this paper, a new preemption policy is proposed and complemented with an adaptive scheme that aims to minimize rerouting. The preemption policy combines the three main optimization criteria: number of LSP to be preempted, priority of LSP to be preempted, and amount of bandwidth to be preempted. The preemption policy is complemented by an adaptive scheme that selects LSP with lower priority and reduces their rate in order to accommodate the new high-priority LSP setup request. Heuristics for both preemption and adaptive preemption policies are derived. Simulation results show the heuristics' accuracy. Performance comparisons of a non-preemptive approach, our preemption policy, the adaptive rate policy, and the policy in use by commercial routers are included.
970504
A 2-exchange heuristic for nesting problems
Abstract This paper describes a new heuristic for the nesting problem based on a 2-exchange neighbourhood generation strategy. This mechanism guides the search through the solution space consisting of the sequences of pieces and relies on a low-level placement heuristic to actually convert one sequence in a feasible layout. The placement heuristic is based on a bottom-left greedy procedure with the ability to fill holes in the middle of the layout at a later stage. Several variants of the 2-exchange nesting heuristic were implemented and tested with different initial solution ranking criteria, different strategies for selecting the next solution, and different neighbourhood sizes. The computational experiments were based on data sets published in the literature. In most of the cases, the 2-exchange nesting algorithm generated better solutions than the best known solutions.
21315647
Reel and sheet cutting at a paper mill
This work describes a real-world industrial problem of production planning and cutting optimization of reels and sheets, occurring at a Portuguese paper mill. It will focus on a particular module of the global problem, which is concerned with the determination of the width combinations of the items involved in the planning process: the main goal consists in satisfying an order set of reels and sheets that must be cut from master reels. The width combination process will determine the quantity/weight of the master reels to be produced and their cutting patterns, in order to minimize waste, while satisfying production orders.A two-phase approach has been devised, naturally dependent on the technological process involved. Details of the models and solution methods are presented. Moreover some illustrative computational results are included.
16974631
Meaning Negotiation for Consensus Formation in Ontology Integration
In project teams, having an unique vocabulary and a common understanding about terms is essential to the success of the project. This issue especially disturbs a design project, which has a multidisciplinary team and must consist of people with specific and different knowledge, from diverse domains, to execute special activities. Negotiation arises from this context as a process for the construction of consensus. The goal of this work is to present a model of negotiation to obtain the consensus of meanings, based on models of business negotiation, and consequently, deal with conflicts and the multiplicity of understandings of a concept, making this negotiation a way for creating value for all agents involved