Traditional measurement tools are not suitable for finegrain performance evaluation of 802.11 wireless networks. To improve this situation, we have developed Interarrival Histograms, a method for measuring transmission delays based on gathering statistics of interarrival intervals at a receiving station. By measuring a sufficient number of interarrival interval samples with a clock resolution o...

The analysis of the data accessing mechanism is of importance to the analytical performance evaluation of any data processing system. So far, most such analyses have been done under the assumption of an uniform data access model. This is not true in the real world and some attempts at modeling non-uniform data access have been made. In this paper, we develop a new, improved model, which we beli...

Information broadcasting, caching of frequently accessed data, and pull-based data delivery are commonly used techniques to reduce data access time of wireless information services. Most of the studies in the literature focused either on individual technique or a combination of them with some restrictive assumptions. In this paper, we propose a dynamic data delivery model where these three tech...

Cloud computing environments do not allow use of a single access control mechanism, single policy language or single policy management tool for various cloud services. Currently, users must use diverse access control solutions available for each cloud service provider to secure their data. Access control policies may be composed in incompatible ways because of diverse policy languages that are ...

Security focused OS (Secure OS) is attracting attention as a method for minimizing damage caused by various intrusions. Secure OSes can restrict the damage due to an attack by using Mandatory Access Control (MAC). In some projects, secure OSes for Linux have been developed. In these OSes, different implementation methods have been adopted. However, there is no method for easily evaluating the p...

Previous studies have shown that the actual handoff schemes employed in the IEEE 802.11 Wireless LANs (WLANs) do not meet the strict delay constraints placed by many multimedia applications like Voice over IP. Both the active and the passive supported scan modes in the standard handoff procedure have important delay that affects the Quality of Service (QoS) required by the real-time communicati...

This paper describes a methodology for efficiently implementing the collective operations, in this case the barrier, on clusters with the emerging InfiniBand Architecture (IBA). IBA provides hardware level support for the Remote Direct Memory Access (RDMA) message passing model as well as the multicast operation. Exploiting these features of InfiniBand to efficiently implement the barrier opera...