Computer networks used in Telecommunication, particularly the Internet, have been used to carry computer data only, but now they carry voice and/or video also. Because each type of this traffic has specific flow characteristics, each type has to be handled with a certain level of guaranteed quality. So based on that, IETF introduced a Quality of Service tool, called Differentiated Service. It offers different levels of service to different classes of traffic. Even then, the problem of congestion arises due to sharing of a finite bandwith. In the case of real time multi media traffic, congestion due to inadequate bandwith contributes heavily to the quality, whereas in non-real time traffic the effect of congestion is to make data transfer take a longer time. In contrast, real time data become become obsolete if they do not arrive on time. Therefore what is needed is some way of ensuring that during periods of congestion, real time traffic is not affected at all, or is at least given a higher priority than non-real time. / The motivation for the research that has been carried out was therefore to develop a rule based traffic management scheme for DiffServ networks with a view to introducing QoS (Quality of Service). This required definition of rules for congestion management/control based on the type and nature of IP traffic encountered, and then constructing and storing these rules to enable future access for application and enforcement. We first developed the required rule base and then developed the software based mobile agents using the Java (RMI) application package, for accessing these rules for application and enforcement. Consequently, these mobile agents act as smart traffic managers at nodes/routers in the computer based communication network and manage congestion. The rule base as well as the mobile agent software developed in Java (RMI), were validated using computer simulation. The contents of the research carried out have been presented in the thesis. / Thesis (PhD)--University of South Australia, 2006.

This thesis develops a number of graph-based techniques that are capable of measuring the dynamic behaviour of a network and discusses their application in network management. By representing a computer network as a time series of uniquely labelled graphs, it is possible to measure the degree of change that has occurred between a pair of graphs, and hence the dynamics in a network. Concepts introduced include the median graph, intra- and inter- graph clustering, and hierarchical graph representations. The focus is on producing efficient algorithms and improved measures of network change. It is believed that these graph-based techniques for measuring network dynamics have great potential in network anomaly detection, and thus will improve reliability of enterprise intranets.

In recent times, the imminent lack of public IPv4 addresses has attracted the attention of both the research community and industry. The cellular industry has decided to combat this problem by using IPv6 for all new terminals. However, the success of 3G network deployment will depend on the services offered to end users. Currently, almost all services reside in the IPv4 address space, making them inaccessible to users in IPv6 networks. Thus, an intermediate translation mechanism is required. Previous studies on network address translation methods have shown that Realm Base Kluge Address Heuristic-IP, REBEKAH-IP supports all types of services that can be offered to IPv6 hosts from the public IPv4 based Internet, and provides excellent scalability. However, the method suffers from an ambiguity problem which may lead to call blocking. This thesis presents an improvement to REBEKAH-IP scheme in which the side effect is removed, creating a robust and fully scalable system. The improvement can be divided into two major tasks including a full investigation on the scalability of addressing and improvements to the REBEKAH-IP scheme that allow it to support important features such as ICMP and IP mobility. To address the first task a method called REBEKAH-IP with Port Extension (RPX) is introduced. RPX is extended from the original REBEKAH-IP scheme to incorporate centralised management of both IP address and port numbers. This method overcomes the ambiguity problem, and improves scalability. We propose a priority queue algorithm to further increase scalability. Finally, we present extensive simulation results on the practical scalability of RPX with different traffic compositions, to provide a guideline of the expected scalability in large-scale networks. The second task concerns enabling IP based communication. Firstly, we propose an ICMP translation mechanism which allows the RPX server to support important end-toend control functions. Secondly, we extend the RPX scheme with a mobility support scheme based on Mobile IP. In addition, we have augmented Mobile IP with a new tunneling mechanism called IP-in-FQDN tunneling. The mechanism allows for unique mapping despite the sharing of IP addresses while maintaining the scalability of RPX. We examine the viability of our design through our experimental implementation.

This dissertation reports on studies of the application of lexicographic graph searches to solve problems in FPGA detailed routing. Our contributions include the derivation of iteration limits for scalar implementations of negotiation congestion for standard floating point types and the identification of pathological cases for path choice. In the study of the routability-driven detailed FPGA routing problem, we show universal detailed routability is NP-complete based on a related proof by Lee and Wong. We describe the design of a lexicographic composition operator of totally-ordered monoids as path cost metrics and show its optimality under an adapted A* search. Our new router, CornNC, based on lexicographic composition of congestion and wirelength, established a new minimum track count for the FPGA Place and Route Challenge. For the problem of long-path timing-driven FPGA detailed routing, we show that long-path budgeted detailed routability is NP-complete by reduction to universal detailed routability. We generalise the lexicographic composition to any finite length and verify its optimality under A* search. The application of the timing budget solution of Ghiasi et al. is used to solve the long-path timing budget problem for FPGA connections. Our delay-clamped spiral lexicographic composition design, SpiralRoute, ensures connection based budgets are always met, thus achieves timing closure when it successfully routes. For 113 test routing instances derived from standard benchmarks, SpiralRoute found 13 routable instances with timing closure that were unroutable by a scalar negotiated congestion router and achieved timing closure in another 27 cases when the scalar router did not, at the expense of increased runtime. We also study techniques to improve SpiralRoute runtimes, including a data structure of a trie augmented by data stacks for minimum element retrieval, and the technique of step tomonoid elimination in reducing the retrieval depth in a trie of stacks structure.

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The focus of this thesis is on the resource allocation problems in wireless sensor and cooperative networks. Typically, wireless sensor networks operate with limited energy and bandwidth are often required to meet some specified Quality-of-Service (QoS) constraints. The ultimate objective for the majority of the problems considered in this thesis is to save battery energy and maximize the network lifetime. / In the first part of this thesis, we employ complex mathematical models to emulate a variety of power drains in wireless sensor nodes. In the first instance, we address a lifetime optimization problem of a wireless TDMA/CDMA sensor network for joint transmit power and rate allocations. The effect of fast fading is captured by including rate outage and link outage constraints on each link. After that, a single-hop wireless sensor network is deployed for a certain application - to estimate a Gaussian source within a pre-specified distortion threshold. In this part, we consider lifetime maximization, in different multiple access protocols such as TDMA, an interference limited non-orthogonal multiple access (NOMA) and an idealized Gaussian multiple access channel. This problem is further studied in a multi-hop scenario where sensing and receiving powers are also included in addition to transmission power. Finally, we investigate a balancing problem between the source coding and transmission power for video wireless sensor systems where the sensor node is required to send the collected video clips, through wireless media, to a base station within a corresponding distortion threshold. All these energy saving and lifetime optimization problems in sensor networks can be formulated via nonlinear nonconvex optimization problems, which are generally hard to solve. However, with favourable variable substitution and reasonable approximation, most of these problems are shown to be convex. The only exception is the Gaussian source esitmation problem in NOMA scenario for which we provide a simple successive convex approximation based algorithm for the NOMA case that converges fast to a suboptimal solution. / In the second part of the thesis, we propose an optimal power allocation scheme with a K-block coding delay constraint on data transmission using a three node cooperative relay network assuming a block fading channel model. Channel information is fed back to the transmitter only in a causal fashion, so that the optimal power allocation strategy is only based on the current and past channel gains. We consider the two simplest schemes for information transmission using a three node (a source, a relay and a destination) relay network, namely the amplify and forward (AF) and decode and forward (DF) protocols. We use the dynamic programming methodology to solve the (K-block delay constrained) expected capacity maximization problem and the outage probability minimization problem with a short term sum power (total transmission power of the source and the relay) constraint. / The main contribution of the thesis is a comprehensive suite of power minimization and lifetime maximization methods that can be used in wireless sensor networks. We present several such applications and extensive numerical examples at the end of each chapter.

This thesis investigates how information and communication technologies (ICT), particularly the World Wide Web (Web), can contribute to the role that Meetings, Incentives, Conferences and Conventions, and Exhibitions (MICE) properties play in local economic development (LED). The complex linkages between MICE, ICT and LED, are explored through a literature review, a website audit, in-depth interviews, and a case study from Horowhenua, New Zealand (NZ). The findings reveal that the Web has considerable but as yet largely untapped potential to facilitate linkages between MICE and local economies. Such potential can only be reached through careful planning, and the realisation on the part of managers, developers and planners, that the Web is more than simply a marketing tool, but is also an integral part of attempts to improve internal MICE performance and external links to local development.

The Resource Reservation Protocol (RSVP) is one of the proposals of the Internet Engineering Task Force (IETF) for conveying Quality of Service (QoS) related information in the form of resource reservations along the communication path. The RSVP specification (i.e. Request for Comments 2205) provides a narrative description of the protocol without any use of formal techniques. Thus, some parts of the document may be ambiguous, difficult to understand, and imprecise. So far, RSVP implementations have provided the only mechanism for validating. The cost for fixing errors in the protocol found in the implementation can be high. These disadvantages together with the fact that RSVP is complex make it a good target for formal specification and verification. This thesis formally defines the RSVP Service Specification, models RSVP using a formal method known as Coloured Petri Nets (CPNs) and attempts to verify the model. The following steps summarise the verification process of RSVP. Firstly, the RSVP service specification is derived from the protocol description and modelled using CPNs. After validating the model, the service language, which defines all the possible service primitive occurrence sequences, is generated from the state space of the model by using automata reduction techniques that preserve sequences. Secondly, RSVP is modelled using CPNs. The model is analysed for a set of behavioural properties. They include general properties of protocols, such as correct termination, and a set of new properties defined in this thesis, which are particular to RSVP. The analysis is based on the state space method. The properties are checked by querying the state graph and checking reachability among multiple nodes of its associated Strongly Connected Component (SCC) graph. As a first step, we analyse RSVP under the assumption of a perfect medium (no loss or duplication) to ensure that protocol errors are not hidden by rare events of the medium. The state space is reduced to obtain the sequences of service primitives allowed by RSVP known as the protocol language. Then, the protocol language is compared with the service language to determine if they are equivalent. The desired properties of RSVP are proved to be satisfied by the RSVP CPN model, so that the features of RSVP included in the CPN model operate as expected under our modelling and analysis assumptions. Also, the language analysis results show that RSVP service primitive occurrence sequences generated by the RSVP model are included in the proposed model of the service specification. However, some service primitive occurrence sequences generated from the service specification model are not in the protocol language. These sequences were analysed. There is strong evidence to suggest that these sequences would also appear in the protocol if the capacity of the medium in the RSVP model was marginally increased. Unfortunately, the standard reachability analysis tools would not handle this case, due to state space explosion. / Thesis (PhD)--University of South Australia, 2003

The number of people shopping on the Internet has grown rapidly in recent years and it has been suggested that the growth rate of Internet transactions now exceeds that of traditional retailing. Despite the significant growth in the use of the Internet for business transactions, there is evidence to suggest that many customers abandon web sites without completing their transactions. It is clearly important to understand why people buy from the Internet and also the way consumers examine websites. There had been limited research undertaken to investigate the relationships between the various antecedents and the willingness to buy in the Internet environment, especially within a single study. The main trust of this research is to examine the antecedents that influence the willingness to buy from the Internet and also how these antecedents influence one another. The antecedents included in this research were brand image (Dodds, Monroe & Grewal, 1991), perceived risk (Sweeney & Soutar, 2001), trust (Lynch & Beck, 2001), affect (Lynch & Beck, 2001), convenience (Szymanski & Hise, 2000), relative price (Sweeney, Soutar & Johnson, 1999), site reputation (Baker, Grewal & Parasuraman, 1994) and web design (Szymanski & Hise, 2000). Some of the antecedents were found to be unsuitable and they were dropped from the study. The empirical results from the final model suggest that perceived value is positively influenced by affect and brand image. Both brand image and affect also positively influence the trust of the website. Willingness to buy from the website is influenced by perceived value and trust of the website.