Modeling vanet deployment in urban settings

... (VANETs) has prompted greater research into simulation models that better reflect urban VANET deployments. Still, we lack a systematic understanding of the required level of simulation details in modeling various real-world urban constraints. In this work, we developed a series of simulation models that account for street layout, traffic rules, multilane roads, acceleration-deceleration, and RF attenuation due to obstacles. Using real and controlled synthetic maps, we evaluated the sensitivity of the simulation results toward these details. Our results indicate that the delivery ratio and packet delays in VANETs are more sensitive to the clustering effect of vehicles at intersections and their accelerationdeceleration. The VANET performance appears to be only marginally affected by the simulation of multiple lanes and careful synchronization at traffic signals. We also found that the performance in dense VANETs improves significantly when routing decisions are limited to a wireless backbone of mesh nodes, whereas in sparse VANETs, performance improves when vehicles also participate in ad hoc routing. Finally, through measurement and analysis of signal strengths around urban city blocks, we show that the effect of signal attenuation due to physical obstacles can potentially be parameterized in simulations. Our work provides a starting point for further understanding and development of more accurate VANET simulation models

Verifiable Sustainability in Data Centers

Sustainability is crucial for combating climate change and protecting our planet. While there are various systems that can pose a threat to sustainability, data centers are particularly significant due to their substantial energy consumption and environmental impact. Although data centers are becoming increasingly accountable to be sustainable, the current practice of reporting sustainability data is often mired with simple green-washing. To improve this status quo, users as well as regulators need to verify the data on the sustainability impact reported by data center operators. To do so, data centers must have appropriate infrastructures in place that provide the guarantee that the data on sustainability is collected, stored, aggregated, and converted to metrics in a secure, unforgeable, and privacy-preserving manner. Therefore, this paper first introduces the new security challenges related to such infrastructure, how it affects operators and users, and potential solutions and research directions for addressing the challenges for data centers and other industry segments

Probabilistic delay guarantees using delay distribution measurements

Carriers increasingly differentiate their wide-area connectivity offerings by means of customized services, such as virtual private networks (VPN) with Quality of Service (QoS) guarantees, or QVPNs. The key challenge faced by carriers is to maximize the number of QVPNs admitted by exploiting the statistical multiplexing nature of input traffic. While existing measurement-based admission control algorithms utilize statistical multiplexing along the bandwidth dimension, they do not satisfactorily exploit statistical multiplexing along the delay dimension to guarantee distinct per-QVPN delay bounds. This paper presents Delay Distribution Measurement (DDM) based admission control algorithm, the first measurement-based approach that effectively exploits statistical multiplexing along the delay dimension. In other words, DDM exploits the well known fact that the actual delay experienced by most packets of a QVPN is usually far smaller than its worst-case delay bound requirement since multiple QVPNs rarely send traffic bursts at the same time. Additionally, DDM supports QVPNs with distinct probabilistic delay guarantees – QVPNs that can tolerate more delay violations can reserve fewer resource than those that tolerate less, even though they require the same delay bound. A comprehensive performance evaluation using Voice over IP traces shows that, when compared to deterministic admission control, DDM can potentially increase the number of admitted QVPNs (and link utilization) by up to a factor of 3.0 even when the delay violation probability is as small as 10 −5

Efficient Provisioning Algorithms for Network Resource Virtualization with QoS Guarantees

In recent years, large commercial and non-commercial customers of network service providers (NSP) are increasingly demanding dedicated and fault-tolerant wide-area network connectivity between their remote endpoints with the ability to exercise fine-grained control over their share of physical network resources. This trend is being coupled with a rapid surge in the amount of real-time network traffic that the NSP's network infrastructure is required to carry. In other words, customers require a virtualized share of the NSP's physical network infrastructure with performance and isolation guarantees. At the same time, NSPs themselves have an inherent need to maximize their own revenue base by accommodating the requirements of as many customers as possible. These three competing forces have created an urgent requirement for resource provisioning techniques that enable network resource virtualization with performance and isolation guarantees and at the same time maximize the utilization efficiency of the network infrastructure. This dissertatio

Real-Time OS Needs Multi-Resource Coordination

Most research on real-time operating systems have focused on scheduling and admission control of a single system resource, such as CPU, disk, and network link. However, real-world real-time applications require access to multiple system resources. Coordinating the allocation and scheduling of multiple resources raises new and interesting research problems, especially for latency-bound applications. The goal of this position paper is to identify these research issues, present sample solutions, and outline open problems for future research