6830084
Performance Analysis of a Leaky-Bucket Controlled ATM Multiplexer
Abstract There are at least three levels where network access control should be exercised: the call level, the burst level and the cell level. These control levels have different time scales. The present paper is concerned primarily with the burst and cell level control. Our system consists of a number of input sources, each controlled by a leaky-bucket mechanism. The outputs from the leaky-buckets are fed to a statistical multiplexer. The cell level loss occurs at the individual leaky-buckets and the burst level loss occurs at the statistical multiplexer. We use a unified state space representation for the leaky-buckets-multiplexer system and a spectral expansion method to analyze the cell level and the burst level behaviors. Numerical results obtained offer insight into the allocation and management of the buffers to attain the best performance tradeoffs.
3873642
On staleness and the delivery of web pages
A popular technique to improve the scalability of a web based system is caching at proxy servers. Caching has the drawback that a cached page becomes stale when the page is updated at the web server. In some cases, staleness may not be completely avoided because the server may not wish to expend the processing and communication resources required to transmit all the updates immediately. In general, if updates are transmitted less frequently, the staleness will tend to increase, but the amount of resources consumed will be reduced. The tradeoff between resource consumption and staleness is investigated. A measure of staleness is defined and optimization problems are formulated. The solutions to these problems allow one to come up with an optimal strategy for transmitting page updates. Numerical examples showing the resource consumption/staleness tradeoff are presented.
45147395
Analysis of a Token Ring Protocol for Voice Transmission
Abstract For voice transmissions in a local-area network, it is desirable to have a small coefficient of variation for the interdeparture time of voice packets at the destination. This may be achieved by the proper design of the medium access protocol. A token ring protocol with provision for voice traffic is considered. An analytic model is developed to study the performance of this protocol with respect to voice traffic. Numerical results showing the effect of model parameters on interdeparture time are presented.
42047029
The effect of multiplexing, switching and other factors on the performance of broadband networks
A network model is developed for studying the effect of multiplexing and switching on broadband network performance. Emphasis is placed on the queuing behavior in the network and the impact of multiplexing and switching on the burstiness of the various traffic streams. The three parameters commonly used to characterize traffic (peak bit rate, mean bit rate, and mean burst length) are also considered, and the dependence of the queuing behavior on these parameters is investigated. The performance of three congestion control schemes based on the leaky bucket algorithm is evaluated. The results provide insight into how call acceptance, bandwidth allocation, and bandwidth enforcement should be implemented in a broadband integrated services digital network (BISDN).<<ETX>>
8690187
Distributed Simulation Using a Network of Processors
Abstract Simulation, particulary of networks of queues, is an application with a high degree of inherent parallelism and is of great practical interest. We hope to exploit this parallelism by performing simulations using a network of cheap, but slow, micro-processors. We define a taxonomy by which we classify a number of parameters of a distributed simulation method, and seek solutions to problems of synchronization, deadlock prevention and inter-process communication arising with various methods in each class of the taxonomy. We concentrate in particular on the class (loose, event-driven) which seems to possess the greatest potential parallelism, and on the class (scaled, tight, time-driven) which allows mock-up studies of real systems. We give algorithms for deadlock prevention and detection, and briefly discuss the design of a distributed operating system to support the simulation application. This research forms part of a joint program with the Dept. of Computer Sciences, University of Texas at Austin, directed by Prof. K.M. Chandy.
675655
Analysis of Broadcast Delivery in a Videotex System
Videotex is a system which provides users with low-cost real-time access to information. In such a system, user requests are forwarded to a service computer where the desired information is retrieved and sent back to the user. In this study, we investigate the response time behavior of a videotex system where information requested by one user is broadcast to all users. A novel queueing model for broadcast delivery is developed. Using this model, we first obtain an analytic expression for the mean response time, and then we develop an efficient algorithm for its computation. Numerical results illustrating the performance characteristics of broadcast delivery are presented.
7144703
Effective iterative techniques for fingerprinting design IP
Fingerprinting is an approach that assigns a unique and invisible ID to each sold instance of the intellectual property (IP). One of the key advantages fingerprinting-based intellectual property protection (IPP) has over watermarking-based IPP is the enabling of tracing stolen hardware or software. Fingerprinting schemes have been widely and effectively used to achieve this goal; however, their application domain has been restricted only to static artifacts, such as image and audio, where distinct copies can be obtained easily. In this paper, we propose the first generic fingerprinting technique that can be applied to an arbitrary synthesis (optimization or decision) or compilation problem and, therefore to hardware and software IPs. The key problem with design IP fingerprinting is that there is a need to generate a large number of structurally unique but functionally and timing identical designs. To reduce the cost of generating such distinct copies, we apply iterative optimization in an incremental fashion to solve a fingerprinted instance. Therefore, we leverage on the optimization effort already spent in obtaining previous solutions, yet we generate a uniquely fingerprinted new solution. This generic approach is the basis for developing specific fingerprinting techniques for four important problems in VLSI CAD: partitioning, graph coloring, satisfiability, and standard-cell placement. We demonstrate the effectiveness of the new fingerprinting-based IPP techniques on a number of standard benchmarks.
14348286
A Visual Model Approach for Parsing Colonoscopy Videos
Colonoscopy is an important screening procedure for colorectal cancer. During this procedure, the endoscopist visually inspects the colon. Currently, there is no content-based analysis and retrieval system that automatically analyzes videos captured from colonoscopic procedures and provides a user-friendly and efficient access to important content. Such a system will be valuable as an educational resource for endoscopic research, a platform to assess procedural skills for endoscopists, and a platform for mining for unknown abnormality patterns that may lead to colorectal cancer. The first necessary step for the analysis is parsing for semantic units. In this paper, we propose a new visual model approach that employs visual features extracted directly from compressed videos together with audio analysis to discover important semantic units called scenes. Our experimental results show average precision and recall of 93% and 85%, respectively.
5097434
Automated discovery of concise predictive rules for intrusion detection
This paper details an essential component of a multi-agent distributed knowledge network system for intrusion detection. We describe a distributed intrusion detection architecture, complete with a data warehouse and mobile and stationary agents for distributed problem-solving to facilitate building, monitoring, and analyzing global, spatio-temporal views of intrusions on large distributed systems. An agent for the intrusion detection system, which uses a machine learning approach to automated discovery of concise rules from system call traces, is described.We use a feature vector representation to describe the system calls executed by privileged processes. The feature vectors are labeled as good or bad depending on whether or not they were executed during an observed attack. A rule learning algorithm is then used to induce rules that can be used to monitor the system and detect potential intrusions. We study the performance of the rule learning algorithm on this task with and without feature subset selection using a genetic algorithm. Feature subset selection is shown to significantly reduce the number of features used while improving the accuracy of predictions.
14407932
Automatic measurement of quality metrics for colonoscopy videos
Colonoscopy is the accepted screening method for detection of colorectal cancer or its precursor lesions, colorectal polyps. Indeed, colonoscopy has contributed to a decline in the number of colorectal cancer related deaths. However, not all cancers or large polyps are detected at the time of colonoscopy, and methods to investigate why this occurs are needed. We present a new computer-based method that allows automated measurement of a number of metrics that likely reflect the quality of the colonoscopic procedure. The method is based on analysis of a digitized video file created during colonoscopy, and produces information regarding insertion time, withdrawal time, images at the time of maximal intubation, the time and ratio of clear versus blurred or non-informative images, and a first estimate of effort performed by the endoscopist. As these metrics can be obtained automatically, our method allows future quality control in the day-to-day medical practice setting on a large scale. In addition, our method can be adapted to other healthcare procedures. Last but not least, our method may be useful to assess progress during colonoscopy training, or as part of endoscopic skills assessment evaluations.
18507162
A statistical methodology for wire-length prediction
In this paper, the classic wire-length estimation problem is addressed and a new statistical wire-length estimation approach that captures the probability distribution function of net lengths after placement and before routing is proposed. These types of models are highly instrumental in formalizing a complete and consistent probabilistic approach to design automation and design closure where, along with optimizing the pertinent cost function, the associated prediction error is also considered. The wire-length prediction model was developed using a combination of parametric and nonparametric statistical techniques. The model predicts not only the length of the net using input parameters extracted from the floorplan of a design, but also probability distributions that a net with given characteristics after placement will have a particular length. The model is validated using the learn-and-test and resubstitution techniques. The model can be used for a variety of purposes, including the generation of a large number of statistically sound, and therefore realistic, instances of designs. The net models were applied to the probabilistic buffer-insertion problem and substantial improvement was obtained in net delay after routing (~ 20%) when compared to a traditional bounding box (BBOX)-based buffer-insertion strategy