32852748
Asynchronous Parallel Arc Consistency Algorithms on a Distributed Memory Machine
Abstract The use of arc consistency algorithms can greatly reduce the search space of a constraint satisfaction problem by preprocessing and eliminating variable assignments which can never participate in a solution. This paper examines two variations in the frequency of communications of three parallel arc consistency algorithms on distributed memory machines. This paper also examines the effect of simple load balancing versus the more robust mean field annealing graph partitioning heuristic on speedup. Through actual machine experimentation, we compute time required for the algorithms based on such parameters as distribution of work, frequency of message passing, and load balancing. Results indicate that the configuration with less frequent communications and the robust load balancing yields the best speedup.
29269446
A Novel Optimal Channel Partitioning Algorithm for Integrated Wireless and Mobile Networks
How to efficiently support multi-class services is a very important issue in integrated wireless and mobile networks because each type of services has distinct characteristics and quality of service (QoS) requirements. This paper presents an efficient algorithm for near optimal channel allocation when different types of services are to be provided in the next generation integrated wireless and mobile networks. We specifically propose a preemptive priority scheme for an integrated wireless and mobile network by first dividing channels into three independent groups and classifying traffic into four different types. The proposed system is modeled by a multi-dimension Markov chain model. Then such a model is used to obtain a set of relations that correlate performances with various system parameters. A novel recursive algorithm is developed to determine the minimal number of channels in each channel group that would be necessary to satisfy the QoS requirements. We also investigate the impact of load ratio for different types of traffic on channel assignment. Finally, we discuss some limitations of our approach and indicate possible future work. We believe that the partitioning scheme proposed in this paper can become a starting point for analysis of future integrated wireless and mobile networks.
15237323
Testing and Fault Tolerance of Multistage Interconnection Networks
Test length is independent of network size in this simple, straightforward methodology for testing MINs (multistage interconnection networks). It requires only four test sequences for single-fault diagnosis. 26 references.
40094538
A Generic Design Methodology for Deadlock-Free Routing in Multicomputer Networks
This paper introduces a generic methodology for defining deadlock-free wormhole routing schemes in any arbitrary network. The basic strategy is to partition a graph into subdigraphs with no cyclic dependencies and selectively assign virtual channels. The usefulness of our scheme is shown for the n-dimensional hypercube, the n-dimensional mesh, and the k-ary n-cube torus by identifying subdigraph characteristics that ensure acyclic routing. Further generalization which allows partial cyclic dependencies without deadlock is achieved by our extended generic methodology. We also illustrate how to identify shortest fixed path and nonminimal adaptive routing schemes using minimum required channels.
5450203
Guest Editors' Introduction: Challenges in Designing Fault-Tolerant Routing in Networks
+I INRE arc several means nf intercomiecting the compoT nents of a computer system. Components can be connccted through direct or indirect connections. In a direct network, channels directly connect each processor. Neighboring nodes communicate with each other by scnding messages across the channcls. In an indirect network, processors are cnnnccted through switches and/or buses. Depending on how components are connected, we have bus-based networks, router-based networks, switcli-bascd networks, and cluster-based (hybrid of the other thrce networks) nctworks. Nctworks can also be classified bascd on topologies, which cau be either replnr or irregulnr. Anothcr classification is based on applications-there are local arca networks (LANs), networks of workstations (NOWs), multiprocessors, and mobilc networks. In a computer network, the efficiency of a routing process is critical to the system performance. A routing process deals with moving data between processors in a given network. When a routing process involves oiic source and onc destination, it is called unicnst or poirit-lopoint communication. When such a proccss involves more than one source and/or one destination, it is called a collective comrnlrnicntion process. Examples of collective communication include iirulticnst (one-to-many, one source and many destinations), brundcnst (one-to-all), and gossip (all-to-all).
43408451
Network Intrusion Detection System Using Random Projection Technique
15003245
Probabilistic treatment of MIXes to hamper traffic analysis
The goal of anonymity providing techniques is to preserve the privacy of users, who has communicated with whom, for how long, and from which location, by hiding traffic information. This is accomplished by organizing additional traffic to conceal particular communication relationships and by embedding the sender and receiver of a message in their respective anonymity sets. If the number of overall participants is greater than the size of the anonymity set and if the anonymity set changes with time due to unsynchronized participants, then the anonymity technique becomes prone to traffic analysis attacks. We are interested in the statistical properties of the disclosure attack, a newly suggested traffic analysis attack on the MIXes. Our goal is to provide analytical estimates of the number of observations required by the disclosure attack and to identify fundamental (but avoidable) 'weak operational modes' of the MIXes and thus to protect users against a traffic analysis by the disclosure attack.
7357174
On the design and quantification of privacy preserving data mining algorithms
The increasing ability to track and collect large amounts of data with the use of current hardware technology has lead to an interest in the development of data mining algorithms which preserve user privacy. A recently proposed technique addresses the issue of privacy preservation by perturbing the data and reconstructing distributions at an aggregate level in order to perform the mining. This method is able to retain privacy while accessing the information implicit in the original attributes. The distribution reconstruction process naturally leads to some loss of information which is acceptable in many practical situations. This paper discusses an Expectation Maximization (EM) algorithm for distribution reconstruction which is more effective than the currently available method in terms of the level of information loss. Specifically, we prove that the EM algorithm converges to the maximum likelihood estimate of the original distribution based on the perturbed data. We show that when a large amount of data is available, the EM algorithm provides robust estimates of the original distribution. We propose metrics for quantification and measurement of privacy-preserving data mining algorithms. Thus, this paper provides the foundations for measurement of the effectiveness of privacy preserving data mining algorithms. Our privacy metrics illustrate some interesting results on the relative effectiveness of different perturbing distributions.
2759775
Distributed channel management in uncoordinated wireless environments
Wireless 802.11 hotspots have grown in an uncoordinated fashion with highly variable deployment densities. Such uncoordinated deployments, coupled with the difficulty of implementing coordination protocols, has often led to conflicting configurations (e.g., in choice of transmission power and channel of operation) among the corresponding Access Points (APs). Overall, such conflicts cause both unpredictable network performance and unfairness among clients of neighboring hotspots. In this paper, we focus on the fairness problem for uncoordinated deployments. We study this problem from the channel assignment perspective. Our solution is based on the notion of channel-hopping, and meets all the important design considerations for control methods in uncoordinated deployments - distributed in nature, minimal to zero coordination among APs belonging to different hotspots, simple to implement, and interoperable with existing standards. In particular, we propose a specific algorithm called MAXchop, which works efficiently when using only non-overlapping wireless channels, but is particularly effective in exploiting partially-overlapped channels that have been proposed in recent literature. We also evaluate how our channel assignment approach complements previously proposed carrier sensing techniques in providing further performance improvements. Through extensive simulations on real hotspot topologies and evaluation of a full implementation of this technique, we demonstrate the efficacy of these techniques for not only fairness, but also the aggregate throughput, metrics.We believe that this is the first work that brings into focus the fairness properties of channel hopping techniques and we hope that the insights from this research will be applied to other domains where a fair division of a system's resources is an important consideration.
202287
Wire speed packet classification without tcams: a few more registers (and a bit of logic) are enough
Packet classification is the foundation of many Internet functions such as QoS and security. A long thread of research has proposed efficient software-based solutions to this problem. Such software solutions are attractive because they require cheap memory systems for implementation, thus bringing down the overall cost of the system. In contrast, hardware-based solutions use more expensive memory systems, e.g., TCAMs, but are often preferred by router vendors for their faster classification speeds. The goal of this paper is to find a "best-of-both-worlds" solution -- a solution that incurs the cost of a software-based system and has the speed of a hardware-based one. Our proposed solution, called smart rule cache achieves this goal by using minimal hardware -- a few additional registers -- to cache evolving rules which preserve classification semantics, and additional logic to match incoming packets to these rules. Using real traffic traces and real rule sets from a tier-1 ISP, we show such a setup is sufficient to achieve very high hit ratios for fast classification in hardware. Cache miss ratios are 2 ∼ 4 orders of magnitude lower than flow cache schemes. Given its low cost and good performance, we believe our solution may create significant impact on current industry practice.
45546568
Multi-channel Attacks
We introduce multi-channel attacks, i.e., side-channel attacks which utilize multiple side-channels such as power and EM simultaneously. We propose an adversarial model which combines a CMOS leakage model and the maximum-likelihood principle for performing and analyzing such attacks. This model is essential for deriving the optimal and very often counter-intuitive techniques for channel selection and data analysis. We show that using multiple channels is better for template attacks by experimentally showing a three-fold reduction in the error probability. Developing sound countermeasures against multi-channel attacks requires a rigorous leakage assessment methodology. Under suitable assumptions and approximations, our model also yields a practical assessment methodology for net information leakage from the power and all available EM channels in constrained devices such as chip-cards. Classical DPA/DEMA style attacks assume an adversary weaker than that of our model. For this adversary, we apply the maximum-likelihood principle to such design new and more efficient single and multiple-channel DPA/DEMA attacks.