The number of Web traffic flows dominates Internet traffic today and most Web interactions are short-lived HTTP connections handled by TCP. Most core Internet routers use Drop Tail queuing which produces bursts of packet drops that contribute to unfair service. This thesis introduces two new active queue management (AQM) algorithms, PISA (PI with Short-lived flows Adjustment) and PIMC (PI with Minimum Cwnd). These AQMs are built on top of the PI (Proportional Integrator). To evaluate the performance of PISA and PIMC, a new simple model of HTTP traffic was developed for the NS-2 simulation. TCP sources inform PISA and PIMC routers of their congestion window by embedding a source hint in the packet header. Using the congestion window, PISA drops packets from short-lived Web flows less than packets from long-lived flows. Using a congestion window, PIMC does not drop a packet when congestion window is below a fixed threshold. This study provides a series of NS-2 experiments to investigate the behavior of PISA and PIMC. The results show fewer drops for both PISA and PIMC that avoids timeouts and increases the rate at which Web objects are sent. PISA and PIMC improve the performance of HTTP flows significantly over PI. PISA performs slightly better than PIMC.

"Traditional security models are out of place in peer networks, where no hierarchy ex- ists, and where no outside channel can be relied upon. In this nontraditional environment we must provide traditional security properties and assure fairness in order to enable the secure, collaborative success of the network. One solution is to form a Trusted Domain, and exclude perceived dishonest and unfair members. Previous solutions have been intolerant of masquerading, and have suffered from a lack of precise control over the allocation and exercise of privileges within the Trusted Domain. Our contribution is the introduction of a model that allows for controlled access to the group, granular control over privileges, and guards against masquerading. Contin- ued good behavior is rewarded by an escalation of privileges, while requiring an increased commitment of resources. Bad behavior results in expulsion from the Trusted Domain. In colluding with malicious nodes, well behaved nodes risk losing privileges gained over time; collusion is thereby discouraged. We implement our solution on top of the Bouncer Toolkit, produced by Narasimha et al. [7], as a prototype peer to peer network. We make use of social models for trust from [], and rely on new cryptographic primitives from the field of Threshold Cryptography. We present the results of an experimental analysis of its performance for a number of thresholds, and present observations on a number of important performance and security improvements that can be made to the underlying toolkit."

by Chan Wing-Fung. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1997. / Incldues bibliographical references (leaves 71-73). / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.iv / LIST OF TABLES --- p.vi / ACKNOWLEDGEMENTS --- p.vii / Chapter / Chapter I. --- INTRODUCTION --- p.1 / Internet banking --- p.1 / Chapter II. --- INTERNET BANKING: AN OVERVIEW --- p.4 / Banking Evolution --- p.4 / The Emergence of Internet Banking --- p.7 / Find/SVP Survey on Internet Banking --- p.9 / General Performance Attributes of Internet --- p.11 / Internet as a new delivery channel --- p.13 / Product --- p.13 / Price --- p.14 / Brand --- p.15 / Customer Service --- p.15 / Categories of Internet banking --- p.17 / Net presence --- p.17 / Interactive Sites --- p.18 / PC Home Banking --- p.19 / Full Internet Banking --- p.20 / The opportunity and the threat --- p.21 / Internet Banking in U.S --- p.23 / Internet Banking in Hong Kong --- p.28 / Chapter III. --- LITERATURE REVIEW --- p.32 / Books --- p.32 / Magazines --- p.33 / Reports and Papers --- p.36 / Journals --- p.38 / Chapter IV. --- METHODOLOGY --- p.41 / Objective --- p.41 / Methodology --- p.42 / Questionnaire --- p.43 / Chapter V. --- RESULTS --- p.47 / Demographic information --- p.47 / PC and Internet usage --- p.49 / Banking behaviour --- p.49 / Attitude towards new services --- p.50 / Attitude towards Internet banking --- p.54 / Chapter VI. --- CONCLUSIONS --- p.60 / Appendix / Chapter 1. --- QUESTIONNAIRE --- p.63 / Chapter 2. --- CODING FORMAT --- p.68 / Chapter 3. --- BIBLIOGRAPHY --- p.71 / Books --- p.71 / Magazines --- p.71 / Reports and Papers --- p.72 / Journals --- p.72 / Web sites --- p.73 / Chapter 4. --- LOCAL BANKS HOMEPAGES --- p.74

by Leung Kwong Lok, Wan Lai Yin, Carol. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 96-96). / ABSTRACT --- p.i / TABLE OF CONTENTS --- p.iii / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.vii / Chapter / Chapter I. --- INTRODUCTION --- p.1 / Electronic Commerce - an Emerging Market --- p.1 / Background on the Internet --- p.3 / Research Objectives --- p.5 / Methodology --- p.6 / Chapter II. --- ELECTRONIC COMMERCE ON THE NET --- p.8 / Size of the Internet Market --- p.8 / Market Potential for Internet Commerce --- p.11 / Business Models for Internet Commerce --- p.15 / Advertising Model --- p.15 / Subscription Model --- p.16 / Transaction Model --- p.17 / Advantages of Internet Shopping & Impact on the Value Chain --- p.19 / Advantages --- p.19 / Impact on Value Chain --- p.21 / Products/Services to be Sold on the Net --- p.22 / Ways to Attract and Sustain Cyber Customers --- p.24 / Strategic Issues that a Net Merchant will Face --- p.26 / Vendor Reliability --- p.28 / Accessibility of the Internet --- p.29 / Copyright --- p.30 / Other Issues --- p.32 / Chapter III. --- INTERNET SHOPPING TECHNOLGICAL ENABLERS --- p.33 / Overview --- p.33 / Intelligent Agent --- p.33 / Internet Payment System --- p.35 / Internet Appliance/Network Computer --- p.40 / Access Technology --- p.41 / Chapter IV. --- INTERNET AND E-COMMERCE DEVELOPMENT IN HONG KONG … --- p.44 / The Hong Kong Internet User Profile Analysis --- p.44 / The Internet Population Growth in Hong Kong --- p.44 / Internet User Demographic Profile --- p.44 / Usage profile --- p.46 / Legislation --- p.46 / Public Non-Exclusive Telecommunication Service (PNETS) License for IAP --- p.47 / Data Privacy Ordinance --- p.47 / Regulation of Obscene and Indecent Materials Transmitted On the Internet --- p.50 / Infrastructure Development --- p.50 / De-regulation Of The Hong Kong Telecommunication Industry --- p.51 / Hong Kong Internet eXchange (HKIX) --- p.52 / The Internet Industry Participants --- p.52 / Internet Access Provider --- p.53 / Internet Content Provider and Online Commerce Models --- p.55 / Chapter V. --- CASE STUDY --- p.60 / Cathay Pacific Airways Limited --- p.60 / Interview Summary --- p.61 / US Experience --- p.63 / Wellcome Company Limited --- p.64 / Interview Summary --- p.66 / U.S. Experience --- p.69 / CityLine (Hong Kong) Ltd --- p.73 / Interview Summary --- p.74 / U.S. Experience --- p.76 / Universal Networks --- p.78 / Interview Summary --- p.78 / US Experience --- p.80 / MEDIA Magazine --- p.82 / Interview Summary --- p.82 / US Experience --- p.84 / Summary Of Interviews --- p.85 / Companies' Expectation And Actual Results --- p.85 / Obstacles Encountered --- p.86 / Wish List --- p.86 / Chapter VI. --- CONCLUSION AND RECOMMENDATIONS --- p.88 / Cultural Factor --- p.89 / Environmental Factor --- p.89 / Technological Factor --- p.90 / Regulatory Factor --- p.91 / Media Impact --- p.91 / Chapter VII. --- LIMITATIONS --- p.92 / APPENDIX --- p.93 / BILIOGRAPHY --- p.96

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Simulation has become an important way to observe and understand various networking phenomena under various conditions. As the demand to simulate larger and more complex networks increases, the limited computing capacity of a single workstation and the limited simulation capability of a single network simulator have become apparent obstacles to the simulationists. In this research we develop techniques that can scale a simulation to address the limited capacity of a single workstation, as well as techniques that can compose a simulation from different simulator components to address the limited capability of a single network simulator. We scale a simulation with two different approaches: 1) We reduce the resource requirement of a simulation substantially, so that larger simulations can fit into one single workstation. In this thesis, we develop three technqiues (Negative Forwarding Table, Multicast Routing Object Aggregation and NIx-Vector Unicast Routing) to aggregate and compress the large amount of superfluous or redundant routing state in large multicast simulations. 2) The other approach to scale network simulations is to partition a simulation model in a way that makes the best use of the resources of the available computer cluster, and distribute the simulation onto the different processors of the computer cluster to obtain the best parallel simulation performance. We develop a novel empirical methodology called BencHMAP (Benchmark-Based Hardware and Model Aware Partitioning) that runs small sets of benchmark simulations to derive the right formulas of calculating the weights that are used to partition the simulation on a given computer cluster. On the other hand, to address the problem of the limited capability of a network simulator, we develop techniques for building complex network simulations by composing from independent components. With different existing simulators good at different protocol layers/scenarios, we can make each simulator execute the layers where it excels, using a simulation backplane to be the interface between different simulators. In this thesis we demonstrate that these techniques enable us to not only scale up simulations by orders of magnitude with a good performance, but also compose complex simulations with high fidelity.

The future success of communication networks hinges on the ability to overcome the mismatch between requested quality of service (QoS) and limited network resources. Spectrum is a natural resource that cannot be replenished and therefore must be used efficiently. On the other hand, energy efficiency (EE) is also becoming increasingly important as battery technology has not kept up with the growing requirements stemming from ubiquitous multimedia applications. The qualities of wireless channels vary with both time and user. We use channel state information (CSI) to dynamically assign wireless resources to users to improve spectral and energy efficiency. We first investigate a series of general treatments of exploiting CSI in a distributed way to control the medium access to maximize spectral efficiency for networks with arbitrary topologies and traffic distributions. As the first step, we propose decentralized optimization for multichannel random access (DOMRA), which uses local CSI and two-hop static neighborhood information to achieve performance comparable with the global optimal channel-aware Aloha. The generic framework developed in DOMRA proved to be very useful in improving cellular networks as well. We develop cochannel interference avoidance (CIA) medium access control (MAC), which is optimized by DOMRA, to mitigate the downlink severe cochannel interference that is usually experienced by cell-edge users. Aloha-based schemes have low channel utilization efficiency because of the collision of entire data frames. We further develop channel-aware distributed MAC (CAD-MAC), which avoids collision through signaling negotiation ahead of data transmission. CAD-MAC completely resolves the contention of networks with arbitrary topologies, achieves throughput close to centralized schedulers, and is robust to any channel uncertainty. Then we address energy-efficient wireless communications while emphasizing orthogonal frequency multiple access (OFDMA) systems. We first discover the global optimal energy-efficient link adaptation in frequency-selective channels using the strict quasiconcavity of energy efficiency functions. This link adaptation optimally balances the power consumption of electronic circuits and that of data transmission on each subchannel. The global optimal energy-efficient transmission can be obtained using iterative operations, which may be complex to be implemented in a practical system. Besides, running iterative algorithms consumes additional energy. Hence, we further develop a closed-form link adaptation scheme, which performs close to the global optimum. Besides, since subchannel allocation in OFDMA systems determines the energy efficiency of all users, we develop closed-form resource allocation approaches that achieve near-optimal performance too. In an interference-free environment, a tradeoff between EE and spectral efficiency (SE) exists, as increasing transmit power always improves SE but not necessarily EE. We continue the investigation in interference-limited scenarios and show that since increased transmit power also brings higher interference to the network, SE is not necessarily higher and the tradeoff is improved. Especially, in interference-dominated regimes, e.g., local area networks, both spectral- and energy-efficient communications desire optimized time-division protocols and the proposed DOMRA, CIA-MAC, and CAD-MAC can be used to improve both spectral and energy efficiency.

The objective of this research is to investigate improved methods for distributing certificate revocation lists (CRLs) in vehicular ad hoc networks (VANETs). VANETs are a subset of mobile ad hoc networks composed of network-equipped vehicles and infrastructure points, which will allow vehicles to communicate with other vehicles and with roadside infrastructure points. While sharing some of the same limitations of mobile ad hoc networks, such as lack of infrastructure and limited communications range, VANETs have several dissimilarities that make them a much different research area. The main differences include the size of the network, the speed of the vehicles, and the network security concerns. Confidentiality, authenticity, integrity, and availability are some of the standard goals of network security. While confidentiality and authenticity at times seem in opposition to each other, VANET researchers have developed many methods for enhancing confidentiality while at the same time providing authenticity. The method agreed upon for confidentiality and authenticity by most researchers and the IEEE 1609 working group is a public key infrastructure (PKI) system. An important part of any PKI system is the revocation of certificates. The revocation process, as well as the distribution of revocation information, is an open research problem for VANETs. This research develops new methods of CRL distribution and compares them to existing methods proposed by other researchers. The new methods show improved performance in various vehicle traffic densities.

This work focuses on the performance characterization of distributed collaborative ad-hoc networks, focusing on such metrics as the lifetime, latency, and throughput capacity of two such classes of networks. The first part concerns modeling and optimization of static Wireless Sensor Networks, specifically dealing with the issues of energy efficiency, lifetime, and latency. We analyze and characterize these performance measures and discuss various fundamental design tradeoffs. For example, energy efficiency in wireless sensor networks can only be improved at the cost of the latency (the delay incurred during communication). It has been clearly shown that improvement in energy efficiency through data aggregation increases the latency in the network. In addition, sleep-active duty cycling of nodes (devices constituting the network), a commonly employed mechanism to conserve battery lifetime in such networks, has adverse effects on their functionality and capacity. Hence these issues deserve a detailed study. The second part of this work concerns performance modeling of Delay Tolerant Networks (DTNs) and Sparse Mobile Ad-Hoc Networks (SPMANETs) in general. We first investigate the effect of modern coding, such as the application of packet-level rateless codes, on the latency, reliability, and energy efficiency of the network. These codes provide us the means to break large messages into smaller packets thereby enabling efficient communication. The work then focuses on developing and formalizing an information-theoretic framework for Delay Tolerant- and other Sparse Mobile Networks. This is enabled by the use of an embedded-Markov-chain approach used for complex queuing-theoretic problems. An important goal of this work is to incorporate a wide range of mobility models into the analysis framework. Yet another important question will be the effect of changing the mobility on the comparative performance of networking protocols. Lastly, the framework will be extended to various communication paradigms such as two-hop vs multi-hop routing, unicast, and multicast.

On the Internet, one of the essential characteristics of electronic commerce is the integration of large-scale computer networks and business practices. Commercial servers are connected through open and complex communication technologies, and online consumers access the services with virtually unpredictable behavior. Both of them as well as the e-Commerce infrastructure are vulnerable to cyber attacks. Among the various network security problems, the Distributed Denial-of-Service (DDoS) attack is a unique example to illustrate the risk of commercial network applications. Using a massive junk traffic, literally anyone on the Internet can launch a DDoS attack to flood and shutdown an eCommerce website. Cooperative technological solutions for Distributed Denial-of-Service (DDoS) attacks are already available, yet organizations in the best position to implement them lack incentive to do so, and the victims of DDoS attacks cannot find effective methods to motivate the organizations. Chapter 1 discusses two components of the technological solutions to DDoS attacks: cooperative filtering and cooperative traffic smoothing by caching, and then analyzes the broken incentive chain in each of these technological solutions. As a remedy, I propose usage-based pricing and Capacity Provision Networks, which enable victims to disseminate enough incentive along attack paths to stimulate cooperation against DDoS attacks. Chapter 2 addresses possible Distributed Denial-of-Service (DDoS) attacks toward the wireless Internet including the Wireless Extended Internet, the Wireless Portal Network, and the Wireless Ad Hoc network. I propose a conceptual model for defending against DDoS attacks on the wireless Internet, which incorporates both cooperative technological solutions and economic incentive mechanisms built on usage-based fees. Cost-effectiveness is also addressed through an illustrative implementation scheme using Policy Based Networking (PBN). By investigating both technological and economic difficulties in defense of DDoS attacks which have plagued the wired Internet, our aim here is to foster further development of wireless Internet infrastructure as a more secure and efficient platform for mobile commerce. To avoid centralized resources and performance bottlenecks, online peer-to-peer communities and online social network have become increasingly popular. In particular, the recent boost of online peer-to-peer communities has led to exponential growth in sharing of user-contributed content which has brought profound changes to business and economic practices. Understanding the dynamics and sustainability of such peer-to-peer communities has important implications for business managers. In Chapter 3, I explore the structure of online sharing communities from a dynamic process perspective. I build an evolutionary game model to capture the dynamics of online peer-to-peer communities. Using online music sharing data collected from one of the IRC Channels for over five years, I empirically investigate the model which underlies the dynamics of the music sharing community. Our empirical results show strong support for the evolutionary process of the community. I find that the two major parties in the community, namely sharers and downloaders, are influencing each other in their dynamics of evolvement in the community. These dynamics reveal the mechanism through which peer-to-peer communities sustain and thrive in a constant changing environment. / text