18455665
Restoration in IP over WDM optical networks
An important requirement in any high speed network is to ensure the network's survivability, i.e., the ability to provide reroutes of ongoing connections after the failure of network components. We consider the problem of embedding an IP layer topology in the WDM transport network layer with the objective of achieving the network's survivability in the IP layer. Specifically, we consider the problem of embedding an arbitrary IP layer topology in a WDM wavelength-routing ring network such that the IP topology remains connected under the presence of the failure of any link in the WDM layer.
800618
Packet filtering for congestion control under DoS attacks
Congestion control in IP networks is typically done at each router through queue management, and the network is entirely dependent on the end hosts to react congestion. However, when misbehaving flows exist and continue to send their packets in very high rates, the queue management schemes implemented in current IP routers reveal a significant shortcoming in protecting legitimate flows. Here, we propose a novel scheme for congestion control in IP networks. Our approach is a time-window based filtering mechanism implemented in a router and processed before a queue management policy is applied. Setting the window size properly and dropping packets reaching in the next window can catch the nonresponsive nature of misbehaving flows. The performance of our proposed scheme is demonstrated through extensive simulations using the NS2, simulator using a set of simulated traffic generated based on IP traces reported in http://www.nlnar.org.
550326
Efficient alarm management in optical networks
As the capacity of optical transport networks increases, rapid fault identification and localization become increasingly important. These problems are more challenging than in traditional electronic networks because of optical transparency. In a transparent optical network which does not regenerate optical signals, a fault may propagate to various parts of the network from the origin, and multiple alarms can be generated for a single failure. Efficient alarm management and filtering requires a careful selection and placement of network monitoring equipment. In this paper we survey the capabilities of current optical monitoring equipment and formulate a problem of selecting monitors to be placed throughout the network. Simulation results suggest that the number of monitors and generated alarms can be significantly reduced if monitor locations are selected judiciously.
24043784
Efficient scheduling of transmissions in optical broadcast networks
All-optical networks (AONs) with a broadcast-star based physical topology offer the possibility of transmission scheduling to resolve channel and receiver conflicts. This paper considers the problem of scheduling packet transmissions in a wavelength-division multiplexed (WDM) optical network with tunable transmitters and fixed-tuned receivers. The scheduling problem is complicated by tuning latency, a limited number of channels, and arbitrary traffic demands. We first analyze scheduling all-to-all packet transmissions and obtain a new lower bound for the schedule length. The lower bound is achieved by an algorithm proposed by Pieris and Sasaki (1994). We then extend the analysis to the case of arbitrary traffic demands and obtain lower bounds for the schedule length. Two constructions for scheduling algorithms are provided through list scheduling and multigraphs. The upper bounds so obtained not only provide performance guarantees with arbitrary demands, but also nearly meet the lower bound in simulations.
6488428
Preserving survivability during logical topology reconfiguration in WDM ring networks
We consider the design of reconfiguring logical topologies over physical WDM ring networks. The logical topology consists of the same set of nodes as the physical topology, and the links of the logical topology are lightpaths established (or embedded) over the physical topology. The logical topology is said survivable if the failure of any single physical link does not disconnect the logical topology. In this paper, we consider the following problem: Given a logical topology with its survivable embedding over a physical ring network and a new logical topology to be reconfigured, find a sequence of lightpaths additions and deletions satisfying the given wavelengths and ports constraints such that the logical topology remains survivable throughout the reconfiguration.
9969836
Efficient route establishment and maintenance in wireless sensor networks with mobile base stations
The integration of ground wireless adhoc networks and airborne UAVs is a promising solution for realtime data collection in wireless sensor networks. Such networks play a vital role in many mission critical tasks such as forest fire-fighting and battlefield support. An important problem is to establish/maintain efficient routing structures in the ground sensor network for packet relaying. Our problem is unique in that the base stations are non-static, which necessitates frequent update of the routing structure. The performance of flooding based methods are evaluated. Particularly, in order to deal with non-uniform node density, we propose to introduce an artificial delay factor to control the flooding pattern. We mathematically prove that the delay should be proportional to local node density. Our simulation results show that the proposed method achieves good load balance among multiple base stations.
5939692
Analyzing the Performance of Mesh and Fat-Tree Topologies for Network on Chip Design
The demand of integration of many heterogeneous semiconductor intellectual property (IP) blocks has been introducing a new chip design paradigm so called on chip network. This paradigm promisingly offers a packet switched network among IPs to reduce the main problems in the very deep sub micron technologies that arise from non-scalable global wire delay, failure to achieve global synchronization, errors due to the signal integrity, non-scalable bus based functional interconnection, etc. This paper introduces interconnected or switched network topologies and also analyze their performances in terms of communication protocol related to the issues such as routing strategy, buffer size, routing algorithm , etc. The above mentioned evaluations are done by utilizing the tool that has been widely used in the research domain of computer network design, so called NS-2.
651586
Design and control of a novel 4-DOFs parallel robot H4
This paper deals with the design and dynamic control simulation of a new type and dynamic control simulation of a new type of 4-DOFs parallel mechanism providing 3 translations and 1 rotation for high-speed handling and machining. This parallel mechanism is named as H4. A model-based dynamic control scheme is developed to improve the accuracy of the trajectory tracking. A simplified dynamic model is used for the H4 robot to decrease the cost of computation. A dynamic simulation is performed using ADAMS/sup TM/. In addition, the adept motion is used as a benchmark test to evaluate the effect of the dynamic control. The simulation results show that the dynamic control dramatically improves the trajectory tracking accuracy.
386520
Establishing Pair-Wise Keys in Heterogeneous Sensor Networks
Many applications that make use of sensor networks require secure communication. Because asymmetric-key solutions are difficult to implement in such a resource-constrained environment, symmetric-key methods coupled with a priori key distribution schemes have been proposed to achieve the goals of data secrecy and integrity. These approaches typically assume that all sensors are similar in terms of capabilities, and hence deploy the same number of keys in all sensors in a network to provide the aforementioned protections. In this paper we demonstrate that a probabilistic unbalanced distribution of keys throughout the network that leverages the existence of a small percentage of more capable sensor nodes can not only provide an equal level of security but also reduce the consequences of node compromise. We demonstrate the effectiveness of this approach on small networks using a variety of trust models and then demonstrate the application of this method to very large systems. The approach and analysis presented in this paper can be applied to all protocols that use probabilistic keys including those that employ broadcast mechanisms, hash functions or polynomials for the generation of keys.
30297846
Throughput Aware Mapping for Network on Chip Design of H.264 Decoder
Network-on-Chip (NoC) has been proposed as a new methodology for addressing the design challenges of future massly integrated system in nanoscale. In this paper, we present the queuing theory based model for router to evaluate the performance of NoC in terms of drop probability, throughput and energy consumption. Then we apply the linear programming to optimize the allocation of the heterogeneously functional blocks (IPs) onto the given heterogeneous NoC architecture so as to obtain the maximum throughput as well as to optimize the energy dissipation of whole system. Finally, the three differently heterogenous Tree-based network topologies are proposed as the NoC architectures for the study case of H.264 Decoder. This paper also evaluates the proposed topologies by comparing them to other conventional topologies such as 2-D Mesh and Fat-Tree with respects to throughput, power consumption and size. We use the power modelling tool, known as Orion model to calculate the static powers, areas, and dynamic powers of three topologies. The experiment results show that our Tree-based topologies offer similar throughputs as Fat-Tree does and much higher throughputs compared to 2-D Mesh while use less chip areas and energy consumptions.
17562316
Euler-Rodrigues frames on spatial Pythagorean-hodograph curves
Abstract We investigate the properties of a special kind of frame, which we call the Euler–Rodrigues frame (ERF), defined on the spatial Pythagorean-hodograph (PH) curves. It is a frame that can be naturally constructed from the PH condition. It turns out that this ERF enjoys some nice properties. In particular, a close examination of its angular velocity against a rotation-minimizing frame yields a characterization of PH curves whose ERF achieves rotation-minimizing property. This computation leads into a new fact that this ERF is equivalent to the Frenet frame on cubic PH curves. Furthermore, we prove that the minimum degree of non-planar PH curves whose ERF is an rotation-minimizing frame is seven, and provide a parameterization of the coefficients of those curves.