Ho Ho-ching. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 104-107). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgment --- p.vi / Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Introduction to PBX based Call Center --- p.1 / Chapter 1.2. --- The Scenarios --- p.2 / Chapter 1.3. --- Thesis Overview --- p.5 / Chapter 2. --- Features of Collaborative Browsing --- p.8 / Chapter 2.1. --- Feature Synchronization vs Bitmap Screen Transfer --- p.8 / Chapter 2.2. --- Basic Collaborative Features of the Collaborative Browser --- p.9 / Chapter 2.2.1. --- Web Page Pushing --- p.10 / Chapter 2.2.2. --- Screen Widget Synchronization --- p.11 / Chapter 2.2.3. --- Tele-pointing and Shared Whiteboard --- p.12 / Chapter 2.3. --- Collaborative Form Manipulation --- p.13 / Chapter 2.3.1. --- Importance of Electronic Form Collaboration --- p.13 / Chapter 2.3.2. --- Basic Support for Form Collaboration ´ؤ´ؤData Synchronization --- p.14 / Chapter 2.3.3. --- Existence of Form Complexity ´ؤForm Data Dependency --- p.75 / Chapter 2.3.4. --- Hinting --- p.17 / Chapter 2.4. --- Collaborative IVR --- p.23 / Chapter 2.4.1. --- Traditional Interactive Voice Response (IVR) Service --- p.23 / Chapter 2.4.2. --- Abstraction ´ؤCorrelating Form Interaction Mechansim with IVR --- p.25 / Chapter 2.4.3 --- Collaborative IVR by Form Interaction Mechanism --- p.27 / Chapter 3. --- Software Architecture --- p.33 / Chapter 3.1. --- The Three-Tier Architecture --- p.33 / Chapter 3.2. --- The Collaboration Mechanism for Collaborative Browser --- p.37 / Chapter 3.2.1. --- Session Initialization/Termination --- p.37 / Chapter 3.2.2. --- Data Flow of the Basic Collaboration Features --- p.39 / Chapter 3.2.3. --- Control Mechanism --- p.40 / Chapter 3.2.4. --- The Hinting Mechanism for Collaborative Form Manipulation --- p.43 / Chapter 3.3. --- The Collaboration Mechanism for Collaborative IVR --- p.45 / Chapter 4. --- Implementation --- p.51 / Chapter 4.1. --- Shareable Document Object Architecture for Collaboration --- p.51 / Chapter 4.1.1. --- Document Object Architecture --- p.51 / Chapter 4.1.2. --- Generalizing to Shareable Document Object Architecture --- p.53 / Chapter 4.2. --- Whiteboard Mechanism --- p.55 / Chapter 4.3. --- Packet Data Unit for Communication --- p.57 / Chapter 4.4. --- Bridging Different Software Components --- p.60 / Chapter 4.5. --- Hinting Mechanism for Collaborative Form Manipulation --- p.63 / Chapter 4.5.1. --- Relating Form Fields to Table Fields --- p.63 / Chapter 4.5.2. --- Hinting by the Hinting Tables --- p.69 / Chapter 4.6. --- Collaborative IVR --- p.73 / Chapter 4.6.1. --- Using Mediator for Collaborative IVR --- p.73 / Chapter 4.6.2. --- Concept of Telephone Form --- p.74 / Chapter 4.6.3. --- Hinting for Collaborative IVR --- p.78 / Chapter 4.7. --- System Integration --- p.81 / Chapter 5. --- Performance Evaluation and Experiment Results --- p.84 / Chapter 5.1. --- Optimizing the Transmission Methodology --- p.84 / Chapter 5.2. --- Browser Responsiveness Study --- p.86 / Chapter 5.2.1. --- Experiment Details --- p.86 / Chapter 5.2.2. --- The Assumptions --- p.89 / Chapter 5.2.3. --- Experiment Results and Analysis --- p.90 / Chapter 5.3. --- Bandwidth Consumption --- p.94 / Chapter 6. --- Conclusions --- p.97 / Appendix A 一 Government Profit Tax Return Form --- p.101 / Appendix B ´ؤ A Phone Banking IVR Service Tree --- p.103 / Bibliography --- p.104

Choy Man Ting. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 66-69). / Abstracts in English and Chinese. / Acknowledgments --- p.ii / Abstract --- p.v / Table of Contents --- p.vii / List of figures --- p.viii / Chapter Chapter 1 --- p.12 / Chapter 1.1 --- OBS Network Architecture --- p.3 / Chapter 1.2 --- Offset Time and Reservation Schemes --- p.5 / Chapter 1.3 --- Research Objectives --- p.7 / Chapter 1.4 --- Overview --- p.8 / Chapter Chapter 2 --- p.9 / Chapter 2.1 --- WDM crossbar architectures --- p.9 / Chapter 2.2 --- Switch Based on Optical Crossbars --- p.10 / Chapter 2.3 --- Switch Based on Wavelength Grating Routers --- p.11 / Chapter Chapter 3 --- p.14 / Chapter 3.1 --- Basics of Dual Shuffle Exchange Network --- p.14 / Chapter 3.2 --- Dual Shuffle-exchange Network --- p.16 / Chapter 3.3 --- Proposed Architecture based on DSN --- p.19 / Chapter 3.4 --- Analysis on blocking due to output contention --- p.20 / Chapter 3.5 --- Implementation issues on the 4x4 switching module --- p.23 / Chapter 3.6 --- Analysis: Non-blocking versus banyan --- p.25 / Chapter Chapter 4 --- p.30 / Chapter 4.1 --- First Scheme --- p.30 / Chapter 4.2 --- Simulation on the first scheme --- p.33 / Chapter 4.3 --- Second Scheme: Tunable wavelength converter --- p.37 / Chapter 4.4 --- Third Scheme: Route to specific wavelength port --- p.42 / Chapter 4.5 --- Analysis on blocking due to insufficient stages --- p.46 / Chapter Chapter 5 --- p.49 / Chapter 5.1 --- Delay analysis of DSN --- p.49 / Chapter 5.2 --- Vertical Expansion --- p.51 / Chapter 5.3 --- Simulation results on vertical expansion --- p.52 / Chapter 5.4 --- Building DSN with 8x8 MEMS switches --- p.54 / Chapter 5.5 --- Prove of the proposed Quarter shuffle network --- p.56 / Chapter 5.6 --- Comparison between Quarter shuffle and doubled links approaches --- p.58 / Chapter Chapter 6 --- p.64 / Conclusion --- p.64 / Bibliography --- p.66

Present-day datacenter networks (DCNs) are designed to achieve full bisection bandwidth in order to provide high network throughput and server agility. However, the average utilization of typical DCN infrastructure is below 10% for significant time intervals. As a result, energy is wasted during these periods. In this thesis we analyze traffic behavior of datacenter networks using traces as well as simulated models. Based on the insight developed, we present techniques to reduce energy waste by making energy use scale linearly with load. The solutions developed are analyzed via simulations, formal analysis, and prototyping. The impact of our work is significant because the energy savings we obtain for networking infrastructure of DCNs are near optimal. A key finding of our traffic analysis is that network switch ports within the DCN are grossly under-utilized. Therefore, the first solution we study is to modify the routing within the network to force most traffic to the smallest of switches. This increases the hop count for the traffic but enables the powering off of many switch ports. The exact extent of energy savings is derived and validated using simulations. An alternative strategy we explore in this context is to replace about half the switches with fewer switches that have higher port density. This has the effect of enabling even greater traffic consolidation, thus enabling even more ports to sleep. Finally, we explore a third approach in which we begin with end-to-end traffic models and incrementally build a DCN topology that is optimized for that model. In other words, the network topology is optimized for the potential use of the datacenter. This approach makes sense because, as other researchers have observed, the traffic in a datacenter is heavily dependent on the primary use of the datacenter. A second line of research we undertake is to merge traffic in the analog domain prior to feeding it to switches. This is accomplished by use of a passive device we call a merge network. Using a merge network enables us to attain linear scaling of energy use with load regardless of datacenter traffic models. The challenge in using such a device is that layer 2 and layer 3 protocols require a one-to-one mapping of hardware addresses to IP (Internet Protocol) addresses. We overcome this problem by building a software shim layer that hides the fact that traffic is being merged. In order to validate the idea of a merge network, we build a simple mere network for gigabit optical interfaces and demonstrate correct operation at line speeds of layer 2 and layer 3 protocols. We also conducted measurements to study how traffic gets mixed in the merge network prior to being fed to the switch. We also show that the merge network uses only a fraction of a watt of power, which makes this a very attractive solution for energy efficiency. In this research we have developed solutions that enable linear scaling of energy with load in datacenter networks. The different techniques developed have been analyzed via modeling and simulations as well as prototyping. We believe that these solutions can be easily incorporated into future DCNs with little effort.

Application-layer overlay networks have recently emerged as a promising platform to deploy additional services over the Internet. A virtual network of overlay nodes can be used to regulate traffic flows of an underlay network, without modifying the underlay network infrastructure. As a result, an opportunity to redeem the inefficiency of IP routing and to improve end-to-end performance of the Internet has arisen, by routing traffic over multiple overlay paths. However, to achieve high end-to-end performance over the Internet by means of overlay networks, a number of challenging issues, including limited knowledge of the underlay network characteristics, fluctuations of overlay path performance, and interactions between overlay and the underlay traffic must be addressed. This thesis provides solutions to some of these issues, by proposing a framework to construct a multi-path overlay architecture for improving Internet end-to-end performance and availability. The framework is formed by posing a series of questions, including i) how to model and forecast overlay path performance characteristics; ii) how to route traffic optimally over multiple overlay paths; and iii) how to place overlay nodes to maximally leverage the Internet resource redundancy, while minimizing the deployment cost. To answer those research questions, analytical and experimental studies have been conducted. As a result, i) a loss model and a hybrid forecasting technique are proposed to capture, and subsequently predict end-to-end loss/delay behaviors; with this predictive capability, overlay agents can, for example, select overlay paths that potentially offer good performance and reliability; ii) to take full advantage of the predictive capability and the availability of multiple paths, a Markov Decision Process based multi-path traffic controller is developed, which can route traffic simultaneously over multiple overlay paths to optimize some performance measures, e.g. average loss rate and latency. As there can be multiple overlay controllers, competing for common resources by making selfish decisions, which could jeopardize performance of the networks, game theory is applied here to turn the competition into cooperation; as a consequence, the network performance is improved; iii) furthermore, to facilitate the deployment of the multi-path overlay architecture, a multi-objective genetic-based algorithm is introduced to place overlay nodes to attain a high level of overlay path diversity, while minimizing the number of overlay nodes to be deployed, and thus reducing the deployment cost. The findings of this thesis indicate that the use of multiple overlay paths can substantially improve end-to-end performance. They uncover the potential of multi-path application-layer overlay networks as an architecture for achieving high end-to-end performance and availability over the Internet.

Using network architecture to describe a biological system is an effective organizational method. The utility of this approach, which generally applies to qualitative models, is enhanced by the addition of quantitative models characterizing the interactions between network nodes. A chromatophore-based signal transduction network is developed, and the highly interconnected major nodes of the network, guanine trisphosphate, adenylate cyclase, and protein kinase A, are identified. These reference nodes serve to partition the network into functional modules, and mechanistic models describing these modules are derived. Three elicitor compounds, forskolin, melanocyte stimulating hormone (MSH), and clonidine, were selected due to their ability to access the signal transduction network at specific reference nodes, and the module configurations corresponding to their mechanisms of action are presented. The chromatophore responses to the three elicitors and to a negative control, L-15 cell medium, were recorded for two experimental blocks consisting of genetically different fish cells. Significant differences in cell responsiveness were evident between the two blocks, but this variability was controlled by the transformation and normalization of the data. The model parameters for each agent were estimated, and the resulting response curves were highly accurate predictors of the changes in apparent cell area, with R-squared values in the 0.88 to 0.96 range. Two examples were presented for the application of a model discovery algorithm, which selects modules from an existing library, generates model output for all valid module configurations, and selects the configurations which best satisfy a fitness function for a given set of target data. The algorithm proved robust to the introduction of different levels of random error in the simulated data sets when applied to a model of the desensitization of a cell membrane receptor, and continued to classify the stochastic data sets correctly even when the underlying rate constants differed significantly from those embedded in the modules. When challenged with the chromatophore data, the model discovery algorithm successfully matched the forskolin and MSH module configurations to the data within the top three models proposed, with less precise classification for the clonidine model. / Graduation date: 2005

Machine virtualization has become a cornerstone of modern datacenters. It enables server consolidation as a means to reduce costs and increase efficiencies. The communication endpoints within the datacenter are now virtual machines (VMs), not physical servers. Consequently, the datacenter network now extends into the server and last hop switching occurs inside the server. Today, thanks to increasing core counts on processors, server VM densities are on the rise. This trend is placing enormous pressure on the network I/O subsystem and the last hop virtual switch to support efficient communication, both internal and external to the server. But the current state-of-the-art solutions fall short of these requirements. This thesis presents new architectures and mechanisms for the network subsystem in virtualized servers to build efficient virtualization platforms. Specifically, there are three primary contributions in this thesis. First, it presents a new mechanism to reduce memory sharing overheads in driver domain-based I/O architectures. The key idea is to enable a guest operating system to reuse its I/O buffers that are shared with a driver domain. Second, it describes Hyper-Switch, a highly streamlined, efficient, and scalable software-based virtual switching architecture, specifically for hypervisors that support driver domains. The Hyper-Switch combines the best of the existing architectures by hosting the device drivers in a driver domain to isolate any faults and placing the virtual switch in the hypervisor to perform efficient packet switching. Further, the Hyper-Switch implements several optimizations, such as virtual machine state-aware batching, preemptive copying, and dynamic offloading of packet processing to idle CPU cores, to enable efficient packet processing, better utilization of the available CPU resources, and higher concurrency. This architecture eliminates the memory sharing overheads associated with driver domains. Third, this thesis proposes an alternate virtual switching architecture, called sNICh, which explores the idea of server/switch integration. The sNICh is a combined network interface card (NIC) and datacenter switching accelerator. This takes the Hyper-Switch architecture one step further. It offloads the data plane of the switch to the network device, eliminating driver domains entirely.

An architectural framework is proposed to secure the data link layer (Layer 2) in Internet protocol (IP) over Ethernet networks. In this architecture, a new security inter-layering concept, incorporating cryptographic Layer 2 identities, is introduced. Instead of traditional media access control (MAC) addresses, secure and flexible data link layer identifiers are utilized to securely bind Layer 2 and upper layers. In addition, to create security parameters and negotiate identifiers at the data link layer, a key establishment protocol is presented. Moreover, this architecture incorporates the IEEE 802.1AE standard (MACsec) and uses a key hierarchy similar to the IEEE 802.11i standard for future compatibility of wired and wireless networks. Finally, we provide a security analysis of the new data link layer security architecture.

This thesis, presents a multiprocessor topology, the hierarchical network of hyper-cubes, which has a low diameter, low degree of connectivity and yet exhibits hypercube like versatile characteristics. The hierarchical network of hyper-cubes consists of k-cubes interconnected in two or more hierarchical levels. The network has a hierarchical, expansive, recursive structure with a constant pre-defined building block. The basic building block of the hierarchical network of hyper-cubes comprises of a k-cube of processor elements and a network controller. The hierarchical network of hyper-cubes retains the positive features of the k-cube at different levels of hierarchy and has been found to perform better than the binary hypercube in executing a variety of application problems. The ASCEND/DESCEND class of algorithms can be executed in O(log2 N) parallel steps (N is the number of data elements) on a hierarchical network of hypercubes with N processor elements. A description of the topology of the hierarchical network of hypercubes is presented and its architectural potential in terms of fault-tolerant message routing, executing a class of highly parallel algorithms, and in simulating artificial neural networks is analyzed. Further, the proposed topology is found to be very efficient in executing multinode broadcast and total exchange algorithms. We subsequently, propose an improvisation of the network to counter faults, and explore implementation of artificial neural networks to demonstrate efficient implementation of application problems on the network. The fault-tolerant capabilities of the hierarchical network of hypercubes with two network controllers per k-cube of processor elements are comparable to those of the hypercube and the folded hypercube. We also discuss various issues related to the suitability of multiprocessor architectures for simulating neural networks. Performance analysis of ring, hypercube, mesh and hierarchical network of hypercubes for simulating artificial neural networks is presented. Our studies reveal that the performance of the hierarchical network of hypercubes is better than those of ring, mesh, hypernet and hypercube topologies in implementing artificial neural networks. Design and implementation aspects of hierarchical network of hypercubes based on two schemes, viz., dual-ported RAM communication, and transputers are also presented. Results of simulation studies for robotic applications using neural network paradigms on the transputer-based hierarchical network of hypercubes reveal that the proposed network can produce fast response times of the order of hundred microseconds.

Thesis (Ph.D. (Computer Science)) - Rhodes University, 2008.

Thesis (Ph. D.)--University of California, Riverside, 2008. / Includes abstract. Title from first page of PDF file (viewed February 3, 2010). Available via ProQuest Digital Dissertations. Includes bibliographical references. Also issued in print.