Exploiting Data Mining Techniques for Broadcasting Data in Mobile Computing Environments

Cataloged from PDF version of article.Mobile computers can be equipped with wireless communication devices that enable users to access data services from any location. In wireless communication, the server-to-client (downlink) communication bandwidth is much higher than the client-to-server (uplink) communication bandwidth. This asymmetry makes the dissemination of data to client machines a desirable approach. However, dissemination of data by broadcasting may induce high access latency in case the number of broadcast data items is large. In this paper, we propose two methods aiming to reduce client access latency of broadcast data. Our methods are based on analyzing the broadcast history (i.e., the chronological sequence of items that have been requested by clients) using data mining techniques. With the first method, the data items in the broadcast disk are organized in such a way that the items requested subsequently are placed close to each other. The second method focuses on improving the cache hit ratio to be able to decrease the access latency. It enables clients to prefetch the data from the broadcast disk based on the rules extracted from previous data request patterns. The proposed methods are implemented on a Web log to estimate their effectiveness. It is shown through performance experiments that the proposed rule-based methods are effective in improving the system performance in terms of the average latency as well as the cache hit ratio of mobile clients

Improving the Multi-Channel Hybrid Data Dissemination System

A major problem with the Internet and web-based applications is the scalable delivery of data. Lack of scalability can hinder performance and decrease the ability of a system to perform as originally designed. One of the most promising solutions to this scalability problem is to use a multiple channel hybrid data dissemination server to deliver requested information to users. This solution provides the high scalability found in multicast, with the low latency found in unicast. A multiple channel hybrid server works by using a push-based multicast channel to deliver the most popular data to users, and reserves the pull-based unicast channel for user requests and delivery of less popular data.The adoption of a multiple channel hybrid data dissemination server, however, introduces a variety of data management problems. In this dissertation, we propose an improved multiple channel hybrid data dissemination model, and propose solutions to three fundamental data management problems that arise in any multiple channel hybrid scheme. In particular, we address the push popularity problem, the document classification problem, and the bandwidth division problem. We also propose a multicast pull channel to the common two-channel hybrid scheme. Our hypothesis that this new channel both improves scalability, and decreases variances in response times, is confirmed by our extensive experimental results. We develop a fully functioning architecture for our three-channel hybrid scheme. In a real world environment, our middleware is shown to provide high scalability for overloaded web servers, while keeping the response times experienced by clients at a minimum. Further, we demonstrate that the practical impact of this work extends to other broadcast-based environments, such as a wireless network

Analyzing the costs/tradeoffs involved between layer 2, layer 3, layer 4 and layer 5 switching

The switching function was primarily entrusted to Layer 2 of the OSI model, i.e. the Data Link Layer. A Layer 2 switch performs forwarding decisions by analyzing the MAC (Media Access Control) address of the destination segment in the frame. The Layer 2 switch checks for the destination address and transmits the packet to the appropriate segment if the address is present in its table of known destinations. If the entry for that address is not present, the switch then forwards the packet to all segments except the one on which it came from. This is known as flooding. When it gets a reply from the destination segment, it learns the location of the new address and adds it to its table of known destinations. As number of users are increasing on the network, the speed and the bandwidth of the network is being stretched to its limits. Earlier, switching was primarily entrusted to Layer 2 (Data Link Layer) of the OSI model, but now there are switches that operate at Layer 3 (Network Layer), Layer 4 (Transport Layer) and Layer 5 (Session Layer) of the OSI model. Going from one layer to the other layer does involve some costs/tradeoffs. My thesis explores the costs and tradeoffs involved with switching based on layers 2, 3, 4 and 5 of the OSI reference model

Centralized prevention of denial of service attacks

The world has come to depend on the Internet at an increasing rate for communication, e-commerce, and many other essential services. As such, the Internet has become an integral part of the workings of society at large. This has lead to an increased vulnerability to remotely controlled disruption of vital commercial and government operations---with obvious implications. This disruption can be caused by an attack on one or more specific networks which will deny service to legitimate users or an attack on the Internet itself by creating large amounts of spurious traffic (which will deny services to many or all networks). Individual organizations can take steps to protect themselves but this does not solve the problem of an Internet wide attack. This thesis focuses on an analysis of the different types of Denial of Service attacks and suggests an approach to prevent both categories by centralized detection and limitation of excessive packet flows