The SOAP Service Description Language (SSDL) is a SOAP-centric language for describing Web Service contracts. SSDL focuses on message abstraction as the building block for creating service-oriented applications and provides an extensible range of protocol frameworks that can be used to describe and formally model Web Service interactions. SSDL's natural alignment with service-oriented design principles intuitively suggests that it encourages the creation of applications that adhere to this architectural paradigm. Given the lack of tools and empirical data for using SSDL as part of Web Services-based SOAs, we identified the need to investigate its practicability and usefulness through empirical work. To that end we have developed Soya, a programming model and runtime environment for creating and executing SSDL-based Web Services. On the one hand, Soya provides straightforward programming abstractions that foster message-oriented thinking. On the other hand, it leverages contemporary tooling (i.e. Windows Communication Foundation) with SSDL-related runtime functionality and semantics. In this thesis, we describe the design and architecture of Soya and show how it makes it possible to use SSDL as an alternative and powerful metadata language without imposing unrealistic burdens on application developers. In addition, we use Soya and SSDL in a case study which provides a set of initial empirical results with respect to SSDL's strengths and drawbacks. In summary, our work serves as a knowledge framework for better understanding message-oriented Web Service development and demonstrates SSDL's practicability in terms of implementation and usability.

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

This work describes the design and implementation of a generic architecture to provide a collective solution for power-aware routing to a wide range of problems in wireless sensor network environments. Power aware-routing is integral to the proposed solutions for different problems. These solutions try to achieve power-efficient routing specific to the problem domain. This can lead to challenging technical problems and deployment barriers when attempting to integrate the solutions. This work extracts various factors to be considered for a range of problems in wireless sensor networks and provides a generic framework for efficient power-aware routing. The architecture aims to relieve researchers from considering power management in their design. We have identified coupling between sources and sinks as the main factor for different design choices for a range of problems. We developed a core-based hierarchical routing framework for efficient power-aware routing that is used to decouple the sources from sinks. The architecture uses only local interaction for scalability and stability in a dynamic network. The architecture provides core-based query forwarding and data dissemination. It uses data aggregation and query aggregation at core nodes to reduce the amount of data to be transmitted. The architecture can be easily extended to incorporate protocols to provide QoS and security to the applications. We use network simulations to evaluate the performance of cluster formation and energy efficiency of the algorithm. Our results show that energy efficiency of the algorithm is better when the transmission range is kept to a minimum for network connectivity as compared to adjustable transmission range.

Overlay networks have been the subject of significant research and practical interest recently in addressing the inefficiency and ossification of the current Internet. In this thesis, we cover various aspects of overlay network design, including overlay routing algorithms, overlay network assignment and multihomed overlay networks. We also examine the behavior of overlay networks under a wide range of network settings and identify several key factors that affect the performance of overlay networks. Based on these findings, practical design guidelines are also given. Specifically, this thesis addresses the following problems: 1) Dynamic overlay routing: We perform an extensive simulation study to investigate the performance of available bandwidth-based dynamic overlay routing from three important aspects: efficiency, stability, and safety margin. Based on the findings, we propose a hybrid routing scheme that achieves good performance in all three aspects. We also examine the effects of several factors on overlay routing performance, including network load, traffic variability, link-state staleness, number of overlay hops, measurement errors, and native sharing effects. 2) Virtual network assignment: We investigate the virtual network (VN) assignment problem in the scenario of network virtualization. Specifically, we develop a basic VN assignment scheme without reconfiguration and use it as the building block for all other advanced algorithms. Subdividing heuristics and adaptive optimization strategies are presented to further improve the performance. We also develop a selective VN reconfiguration scheme that prioritizes the reconfiguration for the most critical VNs. 3) Overlay network configuration tool for PlanetLab: We develop NetFinder, an automatic overlay network configuration tool to efficiently allocate PlanetLab resources to individual overlays. NetFinder continuously monitors the resource utilization of PlanetLab and accepts a user-defined overlay topology as input and selects the set of PlanetLab nodes and their interconnection for the user overlay. 4) Multihomed overlay network: We examine the effectiveness of combining multihoming and overlay routing from the perspective of an overlay service provider (OSP). We focus on the corresponding design problem and examine, with realistic network performance and pricing data, whether the OSP can provide a network service that is profitable, better (in terms of round-trip time), and less expensive than the competing native ISPs.

In this dissertation research we study and address the unique challenges involved in information sharing and dissemination of large-scale group communication applications. We focus on system architectures and various techniques for efficient and scalable information dissemination in distributed P2P environments. Our solutions are developed by targeting at utilizing three representative P2P overlay networks: structured P2P network based on consistent hashing techniques, unstructured Gnutella-like P2P network, and P2P GeoGrid based on geographical location and proximity of end nodes. We have made three unique contributions to the general field of large-scale information sharing and dissemination. First, we propose a landmark-based peer clustering techniques to grouping end-system nodes by their network proximity, and a communication management technique addresses load balancing and reliability of group communication applications in structured P2P network. Second, we develop a utility-based P2P group communication service middleware, consisting of a utility-based topology management and a utility-aware P2P routing, for providing scalable and efficient group communication services in an unstructured P2P overlay network of heterogeneous peers. Third, we propose an overlay network management protocol that is aware of the geographical location of end-system nodes and a set of routing and adaptation techniques, aiming at building decentralized information dissemination service networks to support location-based applications and services. Although different overlay networks require different system designs for building scalable and efficient information dissemination services, we have employed two common design philosophies: (1) exploiting end-system heterogeneity and (2) utilizing proximity information of end-system nodes to localize most of the communication traffic, and (3) using randomized shortcuts to accelerate long-distant communications. We have demonstrated our design philosophies and the performance improvements in the above three types of P2P overlay networks. Concretely, by assigning more workloads to more powerful peers, we can greatly increase the system scalability and reduce the variation of workload distribution. By clustering end-system nodes based on their IP-network proximity or their geographical proximity, and utilizing randomized shortcuts, we can reduce the end-to-end communication latency, balance peer workloads against service request hotspots across the overlay network, and significantly enhance the scalability and efficiency of large-scale decentralized information dissemination and group communication.

Current wireless network solutions are based on a link abstraction where a single co-channel transmitter transmits in any time duration. This model severely limits the performance that can be obtained from the network. Being inherently an extension of a wired network model, this model is also incapable of handling the unique challenges that arise in a wireless medium. The prevailing theme of this research is to explore wireless link abstractions that incorporate the broadcast and space-time varying nature of the wireless channel. Recently, a new paradigm for wireless networks which uses the idea of 'cooperative transmissions' (CT) has garnered significant attention. Unlike current approaches where a single transmitter transmits at a time in any channel, with CT, multiple transmitters transmit concurrently after appropriately encoding their transmissions. While the physical layer mechanisms for CT have been well studied, the higher layer applicability of CT has been relatively unexplored. In this work, we show that when wireless links use CT, several network performance metrics such as aggregate throughput, security and spatial reuse can be improved significantly compared to the current state of the art. In this context, our first contribution is Aegis, a framework for securing wireless networks against eavesdropping which uses CT with intelligent scheduling and coding in Wireless Local Area networks. The second contribution is Symbiotic Coding, an approach to encode information such that successful reception is possible even upon collisions. The third contribution is Proteus, a routing protocol that improves aggregate throughput in multi-hop networks by leveraging CT to adapt the rate and range of links in a flow. Finally, we also explore the practical aspects of realizing CT using real systems.

Traditional routing protocols select paths based on static link weights and converge to new paths only when there is an outright reachability failure (such as a link or router failure). This design allows routing scale to hundreds of thousands of nodes, but it comes at the cost of functionality: routing provides only simple, single path connectivity. Networked applications in the wide-area, enterprise, and data center can all benefit from network protocols that allow traffic to be sent over multiple routes en route to a destination. This ability, also called multipath routing, has other significant benefits over single-path routing, such as more efficiently using network resources and recovering more quickly from network disruptions. This dissertation explores the design of an architecture for path selection in the network and proposes a "narrow waist" interface for networks to expose choice in routing traffic to end systems. Because most networks are also business entities, and are sensitive to the cost of routing traffic in their network, this dissertation also develops a framework for exposing paths based on their cost. For this purpose, this dissertation develops a cost model for routing traffic in a network. In particular, this dissertation presents the following contributions: * Design of path bits, a "narrow waist" for multipath routing. Our work ties a large number of multipath routing proposals by creating an interface (path bits) for decoupling the multipath routing protocols implemented by the network and end systems (or other network elements) making a choice for path selection. Path bits permit simple, scalable, and efficient implementations of multipath routing protocols in the network that still provide enough expressiveness for end systems to select alternate paths. We demonstrate that our interface is flexible and leads to efficient network implementations by building prototype implementations on different hardware and software platforms. * Design of path splicing, a multipath routing scheme. We develop, path splicing, a multipath routing technique, which uses random perturbations from the shortest path to create exponentially large number of paths with only a linear increase in state in a network. We also develop a simple interface to enable end systems to make path selection decisions. We present various deployment paths for implementing path splicing in both intradomain and interdomain routing on the Internet. * Design of low cost path-selection framework for a network. Network operators and end systems can have conflicting goals, where the network operators are concerned with saving cost and reducing traffic uncertainty; and end systems favor better performing paths. Exposing choice of routing in the network can thus, create a tension between the network operators and the end systems. We propose a path-selection framework where end systems make path selection decisions based on path performance and networks expose paths to end systems based on their cost to the network. This thesis presents a cost model for routing traffic in a network to enable network operators to reason about "what-if " scenarios and routing traffic on their network.

The SOAP Service Description Language (SSDL) is a SOAP-centric language for describing Web Service contracts. SSDL focuses on message abstraction as the building block for creating service-oriented applications and provides an extensible range of protocol frameworks that can be used to describe and formally model Web Service interactions. SSDL's natural alignment with service-oriented design principles intuitively suggests that it encourages the creation of applications that adhere to this architectural paradigm. Given the lack of tools and empirical data for using SSDL as part of Web Services-based SOAs, we identified the need to investigate its practicability and usefulness through empirical work. To that end we have developed Soya, a programming model and runtime environment for creating and executing SSDL-based Web Services. On the one hand, Soya provides straightforward programming abstractions that foster message-oriented thinking. On the other hand, it leverages contemporary tooling (i.e. Windows Communication Foundation) with SSDL-related runtime functionality and semantics. In this thesis, we describe the design and architecture of Soya and show how it makes it possible to use SSDL as an alternative and powerful metadata language without imposing unrealistic burdens on application developers. In addition, we use Soya and SSDL in a case study which provides a set of initial empirical results with respect to SSDL's strengths and drawbacks. In summary, our work serves as a knowledge framework for better understanding message-oriented Web Service development and demonstrates SSDL's practicability in terms of implementation and usability.

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 208-226.

Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 192-203.