Distributed Denial of Service (DDoS) attacks are an important and challenging security threat. Despite of the availability of several defence mechanisms and ongoing academic research in the field, attackers handle to build a large network of agent machines. This research developed a tool, DDoSniffer, to tackle the DDoS attack by detecting ongoing attack traffic at the agent machines. Due to the diversity in DDoS attack strategies, it is not realistic to deal with all type of attacks with one single solution. DDoSniffer focuses on TCP-based attacks. Different scenarios were tested to evaluate the performance of DDoSniffer when detecting what we classified as connection attacks and bandwidth attacks. The former attacks generate connections with four packets or fewer. The latter attacks create connections with traffic ratios larger than usual. Detection is the minimum requirement of all defence mechanisms, and DDoSniffer is capable of detecting a broad range of attacks within seconds.

The XML-based interoperable characteristics make enhancing security for XML Web Services a lot different from that of the traditional network-based applications. SSL VPN gateways are usually used to provide security for traditional network-based applications, but not for Web Services. This thesis presents an integrated security solution for securing both traditional network-based applications and Web Services. The integrated security solution includes a VPN framework and a Web Services framework. Considering that we have already had an SSL VPN gateway developed by our lab, we take it as the motherboard of the solution and the VPN server of the gateway as the security functional part of the VPN framework. As the highlight of this thesis project, a Web Services security component, also the security functional part of the Web Services framework, has been developed, implemented and integrated with the SSL VPN gateway to get the integrated security solution. The problem of applying ECC over binary fields for XML security, SOAP message security and Web Services security to make the Web Services security component share the same set of ECC keys with the VPN server on the gateway has been studied. Tools for reading ECC keys and certificates from the BUL's key files have been developed. Methods to adopt the ECC key files to ensure security of Web Services have also been developed. To the best of our knowledge, there is no previous work on adopting ECC keys over binary fields for Web Services security. The integrated security solution we present in this thesis is the prototype of a network device that has functions of three gateways: a VPN gateway, a Web Services security gateway and a Web Services gateway.

This thesis proposes an implementation of an improved algorithm for solving nonlinear separable integer programming problems, as they arise in the field of system reliability. The reliability redundancy optimization solver (RROS) improves on a hybrid technique of dynamic programming with depth first search with tighter variable bounds. The implementation takes the form of an Excel add-in, which will be familiar to users with little formal OR/MS training. The user interface design is discussed. Example applications with benchmarks show that the RROS offers accurate solutions in a comparatively efficient way. This thesis further introduces a surrogate method to solve nonlinear problems with non-separable objectives, where a separable constraint is used as a surrogate objective. This is shown to yield solutions to a number of difficult cases.

This thesis studies the characterization and simulation of long wavelength indium aluminium gallium arsenide (InAlGaAs) lattice-matched to indium phosphide (InP) diode laser, emitting between 1.648 to 1.7 mum in wavelength. The active region of one laser diode sample consists of six In0.69Ga 0.31As quantum wells (1.0% compressive strain) and seven In0.52 Al0.36Ga0.12As unstrained barriers. The lasers are grown using digital alloy molecular beam epitaxy (MBE). The band diagram analysis shows a large conduction band offset which is typical of InAlGaAs lasers. The geometry-dependent and temperature-dependent measurement as well as the laser optical gain, loss and spectral properties were carried out and comparison done for different ridge widths (1.2 to 2.8mum), cavity lengths (555 to 2200mum) and temperature range between 25 and 70°C. The output power as a function of current characteristics reveals threshold current increase with cavity lengths and ridge widths with thermal roll-off occurring at higher injection currents. The slope efficiency and external differential quantum efficiency increases for the narrowest and widest ridge widths within the same cavity length laser device but decreases with increase in cavity length. The temperature analysis shows longer cavity length lasers exhibit better temperature characteristic than the shorter cavity length laser devices indicating the better thermal stability of the longer cavity lasers. Temperature elevations also caused increase in threshold current and decrease in efficiencies. The temperature distribution shows a higher temperature in the active region than the operating temperature due to self heating of the laser devices in continuous wave operation. The optical spectrum exhibits red-shifting of the emission wavelength with increasing bias current and temperature.

In 2008, a cohort of Inuit researchers met in Ottawa for a two-week training course on Inuit health research and planning. A means for ongoing communication after the course was necessary to build on their acquired knowledge. Research shows that online communities of practice (OCoPs) are often unsuccessful due to factors such as a lack of time and a lack of member involvement in design of the OCoP. The objective of this research was to find the determinants that impact participation in an OCoP of members from a cohort of Inuit researchers. An open-ended interview questionnaire was developed and members were interviewed. Results show lack of time as the main barrier to participation. Involvement in the development of an updated OCoP is of interest to many members. In a culture that has been built and sustained by knowledge sharing, an OCoP is a legitimate tool.

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