The SDN control plane needs to frequently update the data plane as the network conditions change. Since each switch updates its flow table independently and asynchronously, the transition of data plane state-if done d...
详细信息
The SDN control plane needs to frequently update the data plane as the network conditions change. Since each switch updates its flow table independently and asynchronously, the transition of data plane state-if done directly from the initial to the final stage-may result in serious flash congestion. Prior work strives to find a congestion-free update plan with multiple stages, each with the property that there will be no congestion independent of the update order. Yet congestion-free update may prevent the network from being fully utilized. It also requires solving a series of LP which is time-consuming. In this paper, we propose congestion-minimizing update and focus on two general problems: The first is to find routing at each intermediate stage that minimizes transient congestion for a given number of intermediate stages. The second is to find the minimum number of intermediate stages and an update plan for a given maximum level of transient congestion. We formulate them as two optimization programs and prove their hardness. We propose a set of algorithms to find the update plan in a scalable manner. Extensive experiments with Mininet show that our solution reduces update time by 50 percent and saves control overhead by 38 percent compared to prior work.
Rapid progress in time domain modeling and computer technology have brought practical time domain simulators within reach. The next decade will see the emergence of sophisticated time domain simulation tools linking g...
详细信息
Rapid progress in time domain modeling and computer technology have brought practical time domain simulators within reach. The next decade will see the emergence of sophisticated time domain simulation tools linking geometry, layout, physical and processing parameters of a microwave or high speed digital circuit with its system specifications and the desired time and frequency performance, including electromagnetic susceptibility and emissions. These CAD systems will most likely employ dedicated parallel processors configured specifically for modeling three-dimensional field problems. Furthermore, the nature of discrete time domain algorithms allows the designer to employ optimization and synthesis procedures which differ from those employed in traditional frequency domain CAD tools. In this paper, recent progress in time domain modeling will be highlighted, and the possible impact of these development on future CAD procedures and systems will be discussed.
Self-tuning servo control based on a nonmodified least-squares algorithm is considered. The fundamental result of the analysis is that the passivity of the two time-varying operators depending on the noise process dyn...
详细信息
Self-tuning servo control based on a nonmodified least-squares algorithm is considered. The fundamental result of the analysis is that the passivity of the two time-varying operators depending on the noise process dynamics, regression vector, and the ponderation matrix sequence of the algorithm is essential for the global stability of the self-tuning regulator. The methodology can be applied to problems of adaptive prediction based on a nonmodified least-squares algorithm and system parameter identification by a least-squares algorithm with a priori prediction.< >
Given a system represented at gate level, we propose an algorithm mapping the design into the minimum number of FPGA's for logic emulation. We first devise a Local Ratiocut clustering scheme to reduce the circuit ...
详细信息
Given a system represented at gate level, we propose an algorithm mapping the design into the minimum number of FPGA's for logic emulation. We first devise a Local Ratiocut clustering scheme to reduce the circuit complexity. Then a Set Covering partitioning approach, utilizing the paradigm of Espresso II, is proposed as an alternative to the widely adopted recursive partitioning paradigm. Experimental results have shown that our approach achieved significant improvement with much shorter run times compared to the recursive Fiduccia-Mattheyses approach on large designs. For instance, on a benchmark of 160K gates and 90K nets, we reduced the number of FPGA's required and the run time by 41 and 86%, respectively.
Optimal performance of a manufacturing layout consisting of several mobile robots performing specific transportation tasks depends on effective task planning. For mobile robots of a specific type and a structured work...
详细信息
Optimal performance of a manufacturing layout consisting of several mobile robots performing specific transportation tasks depends on effective task planning. For mobile robots of a specific type and a structured workplace layout, task planning aims to achieve a maximum throughput of robot trips by coordinating robot motion to minimize congestion in the system. This, in turn, minimizes the number of robots required to carry out a specific work load. In this paper, a novel, synergistic approach based on decentralized path planning, heuristic algorithm based navigation, and localized collision avoidance is presented. A comprehensive, flexible multiple mobile robots system (MMRS) consisting of standard patterns, a local controller, and individual mobile robots has been described. The mobile robots are capable of performing their own path planning and collision avoidance by means of ultrasonic sensors, standard patterns, and rotary optical encoders. Specially designed algorithms for the mobile robot and the local controller have been presented. To ensure greater flexibility in designing the layout, the proposed MMRS was interfaced with a specially designed CAD subsystem. Simulations using varying numbers of robots were performed on a sample layout that was designed using the CAD subsystem. A statistical analysis of the simulation results was performed to evaluate the control algorithms and to determine the optimal number of robots required for the designed layout. The results of the simulation have been presented to illustrate the validity of the approach.
An efficient algorithm is developed to compute the a posteriori probabilities of the origins of measurements in the joint probabilistic data association filter (JPDAF). The inherited parallelism of this algorithm enab...
详细信息
An efficient algorithm is developed to compute the a posteriori probabilities of the origins of measurements in the joint probabilistic data association filter (JPDAF). The inherited parallelism of this algorithm enables it to be suitable for implementation in a multiprocessor system. In this algorithm, the a posteriori probability of the origin of each measurement in the JPDAF is decomposed into two parts. The computation of one part becomes trivial and the algorithm developed here is implemented on the other part, which is shown to be related to permanents. The computational complexity of this algorithm is analyzed in the worst case as well as in the average case. An analysis of this algorithm enables us to conclude that this algorithm is more efficient than other existing ones in the average case.
As more organizations field high-speed networks for distributed systems, ensuring the fault tolerance of those networks assumes greater importance. Although the US Department of Defense has adopted the fiber distribut...
详细信息
As more organizations field high-speed networks for distributed systems, ensuring the fault tolerance of those networks assumes greater importance. Although the US Department of Defense has adopted the fiber distributed data interface as part of its Safenet standard, FDDI's built-in features do not meet Safenet's reliability requirements. This standard requires that a network survive multiple faults;an FDDI network may fail after just two trunk faults. So how do you manage a real-time, FDDI network to meet such a stringent fault-tolerance requirement? The authors' solution involves the use of online and offline components that manage network resources to work around breaks (faults). An integrated approach, their network management strategy combines temporal and spatial redundancy. Temporal redundancy migrates messages on faulty routes to fault-free ones. Spatial redundancy tries to overcome faults by sending multiple copies of messages, hoping that if one copy gets lost, others will reach their destination. Based on four message characteristics-length, period, deadline, and fault-tolerance limit-algorithms perform network management functions. To minimize network overhead, the authors' management strategy manipulates message sets rather than individual messages. Simulation results show that the integrated approach provides better performance than either a temporal or spatial redundancy approach alone.
A Sybil attack occurs when an adversary controls multiple system identifiers (IDs). Limiting the number of Sybil (bad) IDs to a minority is critical for tolerating malicious behavior. A popular tool for enforcing a ba...
详细信息
A Sybil attack occurs when an adversary controls multiple system identifiers (IDs). Limiting the number of Sybil (bad) IDs to a minority is critical for tolerating malicious behavior. A popular tool for enforcing a bad minority is resource burning (RB): the verifiable consumption of a network resource. Unfortunately, typical RB defenses require non-Sybil (good) IDs to consume at least as many resources as the adversary. We present a new defense, ERGO, that guarantees (1) there is always a bad minority;and (2) during a significant attack, the good IDs consume asymptotically less resources than the bad. Specifically, despite high churn, the good-ID RB rate is O (root T J + J), where T is the adversary's RB rate, and J is the good-ID join rate. We show this RB rate is asymptotically optimal for a large class of algorithms, and we empirically demonstrate the benefits of ERGO. (c) 2023 Elsevier Inc. All rights reserved.
Using a two-stage solution methodology and a modified simulated annealing technique, the authors develop a solution algorithm to the network reconfiguration problem, which is a constrained, multiobjective, nondifferen...
详细信息
Using a two-stage solution methodology and a modified simulated annealing technique, the authors develop a solution algorithm to the network reconfiguration problem, which is a constrained, multiobjective, nondifferentiable, optimization problem. This solution algorithm allows the designer to obtain a desirable, global noninferior point in a reasonable computation time. Also, given a desired number of switch-on/switch-off operations involved in the network configuration, the solution algorithm can identify the most effective operations. In order to reduce the computation time required, the idea of approximate calculations is explored and incorporated into the solution algorithm, where two efficient load-flow methods are employed; one for high temperature and the other for low temperature. The solution algorithm has been implemented in a software package and tested on a 69-bus system with very promising results.< >
A general architecture for an autoregressive (AR) planar waveguide optical filter is demonstrated for the first time, Its advantages are a flatter passband, sharper rolloff and better rejection in the stopband compare...
详细信息
A general architecture for an autoregressive (AR) planar waveguide optical filter is demonstrated for the first time, Its advantages are a flatter passband, sharper rolloff and better rejection in the stopband compared to finite impulse response (FIR) filters with the same number of stages. The architecture can be extended to an arbitrary number of stages. A modified Levinson algorithm is derived for filter synthesis and analysis which includes waveguide loss and phase errors between stages, The filter analysisalgorithm allows the filter's coupling ratios and phase errors for each stage to be determined from the filter's spectral response, When combined with a postfabrication tuning process, this analysis method provides feedback for optimizing the response. Autoregressive lattice filters mere designed and fabricated using Ge-doped silica waveguides. Measurements are reported which demonstrate the synthesis and analysisalgorithms. The impact of fabrication tolerances on filter synthesis and of measurement uncertainties on filter analysis are investigated.
暂无评论