Wireless Handoff Optimization: A Comparison of IEEE 802.11r and HOKEY

Abstract. IEEE 802.11 or Wi-Fi has long been the most widely deployed technology for wireless broadband Internet access, yet it is increasingly facing competition from other technologies such as packet-switched cellular data. End user expectations and demands have grown towards a more mobile and agile network. At one end, users demand more and more mobility and on the other end, they expect a good QoS which is sufficient to meet the needs of VoIP and streaming video. However, as the 4G technologies start knocking at doors, 802.11 is being questioned for its mobility and QoS (Quality of Service). Unnecessary handoffs and reauthentication during handoffs result in higher latencies. Recent research shows that if the handoff latency is high, services like VoIP experience excessive jitter. Bulk of the handoff latency is caused by security mechanisms, such as the 4-way handshake and, in particular, EAP authentication to a remote authentication server. IEEE 802.11r and HandOver KEY (HOKEY) are protocol enhancements that have been introduced to mitigate these challenges and to manage fast and secure handoffs in a seamless manner. 802.11r extends the 802.11 base specification to support fast handoff in the MAC protocol. On the other hand, HOKEY is a suite of protocols standardized by IETF to support fast handoffs. This paper analyzes the applicability of 802.11r and HOKEY solutions to enable fast authentication and fast handoffs. It also presents an overview of the fast handoff solutions proposed in some recent research

Metronome: adaptive and precise intermittent packet retrieval in DPDK

DPDK (Data Plane Development Kit) is arguably today's most employed framework for software packet processing. Its impressive performance however comes at the cost of precious CPU resources, dedicated to continuously poll the NICs. To face this issue, this paper presents Metronome, an approach devised to replace the continuous DPDK polling with a sleep&wake intermittent mode. Metronome revolves around two main innovations. First, we design a microseconds time-scale sleep function, named hr_sleep(), which outperforms Linux' nanosleep() of more than one order of magnitude in terms of precision when running threads with common time-sharing priorities. Then, we design, model, and assess an efficient multi-thread operation which guarantees service continuity and improved robustness against preemptive thread executions, like in common CPU-sharing scenarios, meanwhile providing controlled latency and high polling efficiency by dynamically adapting to the measured traffic load

Energy Measurement and Modeling in High Performance Computing with Intel's RAPL

Significant advancements in the cloud computing paradigm have persuaded service providers to offer new and old services using the cloud computing platform for advantages like elasticity, scalability, availability and cost-effectiveness. In addition, the goal of achieving exaflops computation by 2020 by the High Performance Computing (HPC) community and the rapid growth in data generated and analyzed in the scientific computing paradigm have paved the way for an unprecedented growth in the number of server systems in data centers. As an example, CERN is now producing approximately 30 petabytes of data annually, which need to be stored and analyzed for particle physics. The proliferation of applications like social networking, video on demand and big data, is just adding more to the total number of server systems in data centers. Such big numbers of power hungry servers have increased the energy demand of data centers, and as a result energy efficiency in HPC, scientific computing and cloud computing is now a big concern. In this thesis, we investigate the energy consumption of server based computing systems and propose practical solutions for measuring, modeling and analyzing the energy efficiency of such systems. In this thesis, we have extensively used and analyzed Intel's Running Average Power Limit (RAPL) as an energy measurement tool. Firstly, we have used RAPL to profile the performance and energy consumption of an application. Secondly, we propose two strategies to model the power consumption of computing systems: modeling the power consumption of components inside the CPU such as instruction decoders, L2 and L3 caches, etc and modeling the full system power consumption using operating system counters and RAPL. For modeling the power consumption, we have used regression based models, statistical models as well as non-linear additive models. To validate our findings, we have used real production logs from data center as well as instances from Amazon Elastic Compute Cloud (EC2). The proposed power models predict the power consumption with promising accuracy. Thirdly, we have performed an extensive evaluation of RAPL as a power measurement tool and pinpointed RAPL's performance with respect to measurement overhead, accuracy, granularity, etc. This comprehensive analysis also reveals some open issues with RAPL that might weaken its usability in certain scenarios for which we also pinpoint solutions. Finally, to show the applicability of RAPL, we analyze the energy efficiency of two large scale graph processing platforms: Apache Giraph and Spark's GraphX.

State-of-the-art Study and Design of a Small Footprint Version of the COOS Plugin Framework

GSM and UMTS technologies have already gained a huge market penetrationresulting in millions of customers. Machine-to-Machine (M2M) Communicationis promising to be the next big technology that is going to hit themass market with numerous essential services. Telemetry systems, whichwere thought once as the domain of big industrial companies, are now beingavailable to larger and wider customers because of the advances in M2Mcommunication. Thanks to mobile technologies, millions of small handhelddevices are now available in the mass market which can be used to communicatereal time information to the customers. Telenor Objects (a smallbusiness unit of Telenor Group) has defined a new Connected Object Operatingsystem (COOS) which aims to provide a common platform for thedevices to communicate real time data and to provide value added servicesto the customers. COOS is a modular and flexible platform, and includes aplugin framework offered to device and service developers for easy connectingservices and devices to the platform. The current version of COOS pluginframework is based on Java Standard Edition and OSGI, with some supportfor development on J2ME. This thesis research work aims to provide a briefoverview of the Connected Object concept and the COOS platform architecture.The main goal of this thesis is to design a small footprint version ofthe COOS plugin framework for Windows-based handheld devices. It willalso provide a state-of- the art study on mobile device programming focusingon Windows-based services. This thesis research can serve as a startingdocument to provide a full functioning plugin framework for Windows-baseddevices and services

RAPL in Action : Experiences in Using RAPL for Power Measurements

To improve energy efficiency and comply with the power budgets, it is important to be able to measure the power consumption of cloud computing servers. Intel’s Running Average Power Limit (RAPL) interface is a powerful tool for this purpose. RAPL provides power limiting features and accurate energy readings for CPUs and DRAM, which are easily accessible through different interfaces on large distributed computing systems. Since its introduction, RAPL has been used extensively in power measurement and modeling. However, the advantages and disadvantages of RAPL have not beenwell investigated yet. To fill this gap,we conduct a series of experiments to disclose the underlying strengths and weaknesses of the RAPL interface by using both customized microbenchmarks and three well-known application level benchmarks: Stream, Stress-ng, and ParFullCMS. Moreover, to make the analysis as realistic as possible, we leverage two production-level power measurement datasets from the Taito, a supercomputing cluster of the Finnish Center of Scientific Computing and also replicate our experiments on Amazon EC2. Our results illustrate different aspects of RAPL and document the findings through comprehensive analysis. Our observations reveal that RAPL readings are highly correlated with plug power, promisingly accurate enough, and have negligible performance overhead. Experimental results suggest RAPL can be a very useful tool tomeasure and monitor the energy consumption of servers without deploying any complex power meters. We also show that there are still some open issues, such as driver support, non-atomicity of register updates, and unpredictable timings that might weaken the usability of RAPL in certain scenarios. For such scenarios, we pinpoint solutions and workarounds.Peer reviewe

Antifilarial potential of the root extract of the Mirabilis jalapa Linn. (Nyctaginaceae) on cattle filarial parasite Setaria cervi

Effect of aqueous and alcoholic extracts of the roots of Mirabilis jalapa Linn. Four Oclock plant, onthe spontaneous movements of both the whole worm and the nerve-muscle (n.m.) preparation ofSetaria cervi and on the survival of microfilariae in vitro was studied. Alcoholic extract caused theinhibition of spontaneous movements of the whole worm and the n.m. preparation of S. cervi,whereas aqueous extract caused inhibition of spontaneous movements of the n.m. preparation.The initial stimulatory effect was not observed by aqueous and alcoholic extracts on n.m.preparation while effect of alcoholic extract on the whole worm was characterized by an increasein the amplitude of contractions followed by reversible paralysis. The concentrations required toinhibit the movements of the whole worm and n.m. preparation for alcoholic extract of root were270mg/mL and 40 mg/mL, respectively whereas an aqueous extract caused inhibition of n.m.preparation at 30 mg/mL suggesting a cuticular permeability barrier. Alcoholic extract of the rootsof M. jalapa caused concentration related effect on the survival of microfilariae of S. cervi. The LC50and LC90 for alcoholic extract as observed after 6 hrs. were found to be 10 ng/mL and 18 ng/mL.,respectively

Thigh-length compression stockings and DVT after stroke

Controversy exists as to whether neoadjuvant chemotherapy improves survival in patients with invasive bladder cancer, despite randomised controlled trials of more than 3000 patients. We undertook a systematic review and meta-analysis to assess the effect of such treatment on survival in patients with this disease