An improved task assignment scheme for Hadoop running in the clouds

Nowadays, data-intensive problems are so prevalent that numerous organizations in various industries have to face them in their business operation. It is often crucial for enterprises to have the capability of analyzing large volumes of data in an effective and timely manner. MapReduce and its open-source implementation Hadoop dramatically simplified the development of parallel data-intensive computing applications for ordinary users, and the combination of Hadoop and cloud computing made large-scale parallel data-intensive computing much more accessible to all potential users than ever before. Although Hadoop has become the most popular data management framework for parallel data-intensive computing in the clouds, the Hadoop scheduler is not a perfect match for the cloud environments. In this paper, we discuss the issues with the Hadoop task assignment scheme, and present an improved scheme for heterogeneous computing environments, such as the public clouds. The proposed scheme is based on an optimal minimum makespan algorithm. It projects and compares the completion times of all task slots\u27 next data block, and explicitly strives to shorten the completion time of the map phase of MapReduce jobs. We conducted extensive simulation to evaluate the performance of the proposed scheme compared with the Hadoop scheme in two types of heterogeneous computing environments that are typical on the public cloud platforms. The simulation results showed that the proposed scheme could remarkably reduce the map phase completion time, and it could reduce the amount of remote processing employed to a more significant extent which makes the data processing less vulnerable to both network congestion and disk contention. © 2013 Dai and Bassiouni

Analysis of hierarchical cellular networks with mobile base stations

In this paper. we develop and evaluate a hierarchical cellular architecture for totally mobile wireless networks (TMWNs). Extensive performance tests were conducted to evaluate the performance of a two-tier system and compare its throughput, handoff blocking rate and new call success rate with those obtained by a one-tier model. Our tests have shown that when the total number of channels is kept the same, the two-tier system outperformed the one-tier counterpart under all load conditions. Under the constraint of equal power consumption, the two-tier system still achieved improvement over the one-tier system. especially at light and medium load levels. The improvement of the two-tier system over the one-tier system was observed to diminish as the degree of randomness in the mobility model is reduced scenarios where the one-tier system outperforms the two-tier system are given. Load balancing schemes based on the concept of reversible handoffs are introduced and their performance improvements are analyzed. Comparison results on the percentage of terminal coverage are presented. An analytical model to compute the new call and handoff blocking probabilities in TMWN is given and evaluated. The model extends the Markov chain approach previously used in hierarchical architectures with stationary base stations and uses a corrected derivation for the handoff blocking probability

Supporting differentiated quality of service in optical burst switched networks

We propose and evaluate two new schemes for providing differentiated services in optical burst switched (OBS) networks. The two new schemes are suitable for implementation in OBS networks using just-in-time (JIT) or just-enough-time (JET) scheduling protocols. The first scheme adjusts the size of the search space for a free wavelength based on the priority level of the burst. A simple equation is used to divide the search spectrum into two parts: a base part and an adjustable part. The size of the adjustable part increases as the priority of the burst becomes higher. The scheme is very easy to implement and does not demand any major software or hardware resources in optical cross-connects. The second scheme reduces the dropping probability of bursts with higher priorities through the use of different proactive discarding rates in the network access station (NAS) of the source node. Our extensive simulation tests using JIT show that both schemes are capable of providing tangible quality of service (QoS) differentiation without negatively impacting the throughput of OBS networks

Effective preemptive scheduling scheme for optical burst-switched networks with cascaded wavelength conversion consideration

We introduce a new preemptive scheduling technique for next-generation optical burst switching (OBS) networks considering the impact of cascaded wavelength conversions. It has been shown that when optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause certain signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. Accordingly, subject to this practical impediment, we improve a recently proposed fair channel scheduling algorithm to deal with the fairness problem and aim at burst loss reduction simultaneously in OBS environments. In our scheme, the dynamic priority associated with each burst is based on a constraint threshold and the number of already conducted wavelength conversions among other factors for this burst. When contention occurs, a new arriving superior burst may preempt another scheduled one according to their priorities. Extensive simulation results have shown that the proposed scheme further improves fairness and achieves burst loss reduction as well

Architecture and sparse placement of limited-wavelength converters for optical networks

Equipping all nodes of a large optical network with full conversion capability is prohibitively costly. To improve performance at reduced cost, sparse converter placement algorithms are used to select a subset of nodes for full-conversion deployment. Further cost reduction can be obtained by deploying only limited conversion capability in the selected nodes. We present a limited wavelength converter placement algorithm based on the k-minimum dominating set (k-MDS) concept. We propose three different cost-effective optical switch designs using the technologically feasible nontunable optical multiplexers. These three switch designs are flexible node sharing, strict node sharing, and static mapping. Compared to the full search heuristic of O(N-3) complexity based on ranking nodes by blocking percentages, our algorithm not only has a better time complexity O(RN2), where R is the number of disjoint sets provided by k-MIDS, but also avoids the local minimum problem. The performance benefit of our algorithm is demonstrated by network simulation with the U.S Long Haul topology having 28 nodes (91 is 5) and the National Science Foundation (NSF) network having 16 nodes (91 is 4). Our simulation considers the case when the traffic is not uniformly distributed between node pairs in the network using a weighted placement approach, referred to as k-WMDS. From the optical network management point of view, our results also show that the limited conversion capability can achieve performance very close to that of the full conversion capability, while not only decreasing the optical switch cost but also enhancing its fault tolerance

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Electronics — A New Multidisciplinary Open Access Journal

The proliferation of electronic devices has profoundly affected all aspects of modern life. Large populations of people worldwide are now acclimated to the use of modern electronic devices on a daily basis. Giant industrial corporations, commercial companies and small businesses all use a variety of computing, communications and electronic devices to increase their productivity, enhance market research and improve customer support and satisfaction. [...

Preventing Session Hijacking In Collaborative Applications With Hybrid Cache-Supported One-Way Hash Chains

Session hijacking attacks of social network websites are one of the commonly experienced cyber threats in today\u27s Internet especially with the unprecedented proliferation of wireless networks and mobile applications. To address this problem, we propose a cache supported hybrid two-dimensional one-way hash construction to handle social networks\u27 user sessions authentication in collaborative applications efficiently. The solution, which presents a major redesign from [18], is based on utilizing two-dimensional OHC chains equipped with sparse caching capabilities to carry out authentication during social networks users\u27 sessions. We analyze the proposed hybrid scheme mathematically to determine the cost of authentication and develop a quartic equation to check the optimal configuration of the two dimensions. We also evaluate the hybrid scheme with simulation experiments of different configurations and scenarios. The results of the simulation experiments show that the hybrid scheme improves performance of the OHC tremendously while efficiently and securely handling authentication