759389
Mesh Permutation Routing with Locality
Given the permutation routing problem on mesh-connected arrays with a known maximum distance, d, between any source- destination pair, we show how sorting and the greedy algorithm can be combined to yield a deterministic, asymptotically optimal algorithm for solving the problem. This simple algorithm runs in d+O(df(d)) time and requires an O(f;(d)) buffer size (or O(d) time and constant buffer size if we choose f(d) to be a constant). It also gives efficient solutions to the k-k routing problem with locality.
18650610
Modeling multistep cyber attacks for scenario recognition
Efforts toward automated detection and identification of multistep cyber attack scenarios would benefit significantly from a methodology and language for modeling such scenarios. The Correlated Attack Modeling Language (CAML) uses a modular approach, where a module represents an inference step and modules can be linked together to detect multistep scenarios. CAML is accompanied by a library of predicates, which functions as a vocabulary to describe the properties of system states and events. The concept of attack patterns is introduced to facilitate reuse of generic modules in the attack modeling process. CAML is used in a prototype implementation of a scenario recognition engine that consumes first-level security alerts in real time and produces reports that identify multistep attack scenarios discovered in the alert stream.
12589493
Automatic analysis of firewall and network intrusion detection system configurations
Given a network that deploys multiple firewalls and network intrusion detection systems (NIDSs), ensuring that these security components are correctly configured is a challenging problem. Although models have been developed to reason independently about the effectiveness of firewalls and NIDSs, there is no common framework to analyze their interaction. This paper presents an integrated, constraint-based approach for modeling and reasoning about these configurations. Our approach considers the dependencies among the two types of components, and can reason automatically about their combined behavior. We have developed a tool for the specification and verification of networks that include multiple firewalls and NIDSs, based on this approach. This tool can also be used to automatically generate NIDS configurations that are optimal relative to a given cost function.
42848873
Time Lower Bounds for Permutation Routing on Multi-Dimensional Bused Meshes
We present time lower bounds for the permutation routing problem on three- and higher-dimensional n x…x n meshes with buses. We prove an (r–1)n/r lower bound for the general case of an r-dimensional bused mesh, r≥2, which is not as strong for low-dimensional as for higher-dimensional cases. We then use a different approach to construct a 0.705n lower bound for the three-dimensional case.
10409164
Denial of service against the Domain Name System
Because many network services rely on the Domain Name System, denial-of-service attacks against it can be particularly damaging. This article analyzes such threats and reviews existing and proposed countermeasures for addressing them.
15843617
Routing with Locality on Meshes with Buses
Routing with locality is studied for meshes with buses. In this problem, packets' distances are bounded by a value,d, which is less than the diameter of the network. This problem arises naturally when specific known algorithms are implemented on meshes. Solving this problem in ordinary meshes requires at least a routing time ofdsteps. To do better than this, we propose adding a kind of short bus to ordinary meshes. By using a technique which we call iterative walk-and-ride, we show how the routing time can be reduced by approximately one-third for solving the problem (including the multipacket version) on one- and two-dimensional short-bus meshes. The bounds we develop are tight.
5982660
Efficient video similarity measurement with video signature
The video signature method has previously been proposed as a technique to summarize video efficiently for visual similarity measurements (see Cheung, S.-C. and Zakhor, A., Proc. SPIE, vol.3964, p.34-6, 2000; ICIP2000, vol.1, p.85-9, 2000; ICIP2001, vol.1, p.649-52, 2001). We now develop the necessary theoretical framework to analyze this method. We define our target video similarity measure based on the fraction of similar clusters shared between two video sequences. This measure is too computationally complex to be deployed in database applications. By considering this measure geometrically on the image feature space, we find that it can be approximated by the volume of the intersection between Voronoi cells of similar clusters. In the video signature method, sampling is used to estimate this volume. By choosing an appropriate distribution to generate samples, and ranking the samples based upon their distances to the boundary between Voronoi cells, we demonstrate that our target measure can be well approximated by the video signature method. Experimental results on a large dataset of Web video and a set of MPEG-7 test sequences with artificially generated similar versions are used to demonstrate the retrieval performance of our proposed techniques.
45839859
Parallel Algorithm Design for Workstation Clusters
Clusters of workstations connected by local area networks are in common use in many organizations. The combined processing power of these clusters is rarely exploited owing to the lack of suitable parallel algorithms. The paper describes a parallel programming paradigm called supervisor-worker, suitable for the workstation environment, which can be used to speed up the execution of a large class of existing sequential programs. Simple formulae are developed to predict the speed-up of a parallel algorithm developed in this way. The predictions depend on two easily-determined parameters of the sequential program and the characteristic communication cost of the workstation cluster. Consequently, it is possible to estimate the benefits of the parallel program before proceeding with detailed implementation. As an example, the parallel version of a travelling salesman program is developed and the measured speed-up compared with the predicted speed-up.
1708697
Enhancing compositional reachability analysis with context constraints
Compositional techniques have been proposed for traditional reachability analysis in order to introduce modularity and to control the state explosion problem. While modularity has been achived, state explosion is still a problem. Indeed, this problem may even be exacerbated as a locally minimised subsystem may contain many states and transitions forbidden by its context or environments. This paper presents a method to alleviate this problem effectively by including context constraints in local subsystem minimisation. The global behaviour generated using the method is observationally equivalent to that generated by compositional reachability analysis without the inclusion of context constraints.Context constraints, specified as interface processes, are restrictions imposed by the environment on subsystem behaviour. The minimisation produces a simplified machine that describes the behaviour of the subsystem constrained by its context. This machine can also be used as a substitute for the original subsystem in the subsequent steps of the compositional reachability analysis. Interface processes capturing context constraints can be specified by users or automatically constructd using a simple algorithm. The concepts in the paper are illustrated with a clients/server system.
45469802
Towards a Framework for Testing Distributed Multimedia Software Systems
With the advancement in network speed and computing power; distributed multimedia applications are becoming populal: However; general principles of system testing cannot be directly applied to testing of distributed multimedia software systems (DMSS) on account of their stringent timing and synchronization requirements. This paper presents a framework for testing DMSS with special emphases on test case generation and resr architecture. We propose ways to greatly cut down the number of test cases without compronzising the test effectiveness. Procedures for testing the servers and the clients are also discussed.
28306600
A model-based authorware for the construction of distributed multimedia systems
Abstract Distributed multimedia systems typically involve a sophisticated user interaction. Further, objects are allocated on physically distributed computing systems, and multimedia data must be transferred across heterogeneous networks in a timely manner. These systems often have complex requirements on a user interaction, quality of service and temporal order among media streams. The design and implementation of these requirements are inherently complex and present an extraordinary design and programming challenge. Generally, these complex requirements cannot be adequately captured using a single model or a design notation. The challenge amounts to (i) identification of multiple, often orthogonal models, each capturing a specific aspect of the requirements, and (ii) provision of an authorware that supports the composition of these models. In this paper, we propose to capture the multimedia requirements in three different models: configuration, user control and presentation, and demonstrate how the composition of these models can be supported by an authorware using the Java and CORBA technologies. The concepts are illustrated using a real-life example based on a virtual city tour application that features distributed controls, collaborative work and multimedia presentations. Various distributed multimedia applications like video phone, video conferencing and distributed presentation have been successfully constructed using the proposed multiple models and authorware. The results are encouraging and the approach can shorten the development of multimedia applications considerably.