The IEEE 802.3az standard, known as Energy Efficient Ethernet (EEE), is one of recent efforts to improve energy efficiency in communications. However, EEE may not achieve good energy efficiency on some traffic patterns. Coalescing techniques were proposed to solve this problem, but their implementations typically employ a simple polity and need further optimization. Adaptive interrupt coalescing (AIC) has been recently proposed to suggest a better policy, but AIC may not be utilized in high-speed networks having 1G or 10G bandwidth. The paper proposes interval-based adaptive interrupt coalescing (IAIC) that can enhance energy efficiency in high-speed networks. EEE with IAIC at the sender has been implemented and experimented with at 1Gbps bandwidth. The experimental results show that IAIC achieves better energy efficiency than other approaches and can reduce up to 71.59% of energy consumed in a network interface card with no energy savings technique.

Energy efficiency is increasingly important for future information and communication technologies (ICT). As an effort to improve energy efficiency in communications, the IEEE 802.3 Working Group approved IEEE 802.3az standard, known as Energy Efficient Ethernet (EEE) in 2010. EEE uses a Low Power Idle (LPI) mode to reduce the energy consumption of a link when no packets are being sent, but it has been shown that EEE cannot achieve good energy efficiency when small packets are sent periodically with a gap between them. To solve this problem, coalescing techniques were proposed such as packet coalescing and interrupt coalescing. EEE with either of two coalescing techniques shows better energy efficiency but its implementations typically employ a few fixed coalescing parameters and need further optimization. The paper proposes adaptive interrupt coalescing (AIC) that could improve energy efficiency and support performance as well. EEE with AIC at the sender has been implemented with the Intel 82579 network interface card (NIC) and e1000e Linux device driver. The experiments were performed at 100 M bps bandwidth to verify the feasibility of AIC. The experimental results show that energy efficiency of AIC is improved in most cases despite performance consideration and in the best case can be improved up to 37% compared to that of conventional interrupt coalescing techniques.

The concept of energy-efficient networking has begun to spread in the past few years, gaining increasing popularity. A common opinion among networking researchers is that the sole introduction of low consumption silicon technologies may not be enough to effectively curb energy requirements. Thus, for disruptively boosting the network energy efficiency, these hardware enhancements must be integrated with ad-hoc mechanisms that explicitly manage energy saving, by exploiting network-specific features. The IEEE 802.3az Energy Efficient Ethernet (EEE) standard is one of such efforts. EEE introduces a low power mode for the most common Ethernet physical layer standards and is expected to provide large energy savings. However, it has been shown that EEE may not achieve good energy efficiency because mode transition overheads can be significant, leading to almost full energy consumption even at low utilization levels. Coalescing techniques such as packet coalescing and interrupt coalescing were proposed to improve energy efficiency of EEE, but their implementations typically adopt a simple policy that employs a few fixed values for coalescing parameters, thus it is difficult to achieve optimal energy efficiency. The paper proposes adaptive interrupt coalescing (AIC) that adopts an optimal policy that could not only improve energy efficiency but support performance. AIC has been implemented at the sender side with the Intel 82579 network interface card (NIC) and e1000e Linux device driver. The experiments were performed at 100 M bps transfer rate and show that energy efficiency of AIC is improved in most cases despite performance consideration and in the best case can be improved up to 37% compared to that of conventional interrupt coalescing techniques.

As more computing and communication resources appear, energy efficiency becomes increasingly important for future information and communication technologies. We need energy-efficient technologies that can reduce the overall energy consumption of computation, storage and communications. Despite the potential of the next generation nonvolatile RAM (NVRAM) for energy savings, it is typically used as storage devices to improve system performance of file systems and is not utilized for the purpose of improving energy efficiency. This paper suggests an energy-efficient writing approach in a file system that adopts the NVRAM-based SSD as a storage device. Simulation results show that the energy efficient writing approach consumes less energy than the conventional writing approach for ideal workloads as both the data size in a write request and the subpage size get smaller.

The advent of the state-of-the-art technologies such as cloud computing and big data processing stimulates the provision of various new IT services, which implies that more servers are required to support them. However, the need for more servers will lead to more energy consumption and the efficient use of energy in the computing environment will become more important. The next generation nonvolatile RAM has many desirable features such as byte addressability, low access latency, high density and low energy consumption. There are many approaches to adopt them especially in the area of the file system involving storage devices, but their focus lies on the improvement of system performance, not on energy reduction. This paper suggests a novel approach for energy reduction in which the MRAM-based SSD is utilized as a storage device instead of the hard disk and a downsized page is adopted instead of the 4KB page that is the size of a page in the ordinary file system. The simulation results show that energy efficiency of a new approach is very effective in case of accessing the small number of bytes and is improved up to 128 times better than that of NAND Flash memory.

Dynamic Hash Tables (DHTs) are distributed systems that maintain key-value pairs and provide efficient lookup services. Traditional DHTs usually rely on a random ID distribution of the keys to achieve such efficiency. Uniformly random hash functions are typically used to create uniformly random ID distributions from non-random key distributions. However, there are many cases where such random hash functions cannot be applied. For example, those systems that provide range queries over the keys cannot apply random hash functions on the keys, otherwise, the range query is very difficult to support. In this paper, we present a new lookup system called DChord, which does not depend on the randomness assumption to achieve its performance. To show the performance of the proposed system, we provide mathematical analysis and extensive simulation results in a highly non-random USN (Ubiquitous Sensor Network) metadata identifier space. To be specific, we show that DChord has high regularity in terms of in-degree and out-degree distributions. Thus, the system is robust against random node failures. We also show that query processing load is well balanced among nodes and the lookup speed is deterministic in such a way that the number of nodes to visit for a query is at most log(2)(N).

The Green's equivalence relations have played a fundamental role in the development of semigroup theory. They are concerned with mutual divisibility of various kinds, and all of them reduce to the universal equivalence in a group. Boolean matrices have been successfully used in various areas, and many researches have been performed on them. Studying Green's relations on a monoid of boolean matrices will reveal important characteristics about boolean matrices, which may be useful in diverse applications. Although there are known algorithms that can compute Green relations, most of them are concerned with finding one equivalence class in a specific Green's relation and only a few algorithms have been appeared quite recently to deal with the problem of finding the whole D or J equivalence relations on the monoid of all Boolean matrices. However, their results are far from satisfaction since their computational complexity is exponential-their computation requires multiplication of three Boolean matrices for each of all possible triples of Boolean matrices and the size of the monoid of all Boolean matrices grows exponentially as n increases. As an effort to reduce the execution time, this paper shows an isomorphism between the R relation and L relation on the monoid of all Boolean matrices in terms of transposition. introduces theorems based on it discusses an improved algorithm for the J relation computation whose design reflects those theorems and gives its execution results.

Since the development of the Distributed Hash Tables (DHTs), the distributed lookup services are one of the hot topics in the networking area. The main reason of this popularity is the simplicity of the lookup structure. However, the simple key based search mechanism makes the so called "keyword" based search difficult if not impossible. Thus, the applicability of the DHTs is limited to certain areas. In this paper. we find that DHTs can be used as the ubiquitous sensor network (USN) metadata lookup service across a large number of sensor networks. The popularity of the Ubiquitous Sensor Network has motivated the development of the USN middleware services for the sensor networks. One of the key functionalities of the USN middleware service is the lookup of the USN metadata, by which users get various information about the sensor network such as the type of the sensor networks and/or nodes, the residual of the batteries, the type of the sensor nodes. Traditional distributed hash table based lookup systems are good for one sensor network. However, as the number of sensor network increases, the need to integrate the lookup services of many autonomous sensor networks so that they can provide the users an integrated view of the entire sensor network. In this paper, we provide a hybrid lookup model, in which the autonomous lookup services are combined together and provide seamless services across the boundary of a single lookup services. We show that the hybrid model can provide far better lookup performance than a single lookup system.

Green's relations are five equivalence relations that characterize the elements of a semigroup in terms of the principal ideals. The J relation is one of Green's relations. Although there are known algorithms that can compute Green relations, they are not useful for finding all J relations in the semigroup of all Boolean matrices. Its computation requires multiplication of three Boolean matrices for each of all possible triples of Boolean matrices. The size of the semigroup of all Boolean matrices grows exponentially as n increases. It is easy to see that it involves exponential time complexity. The computation of J relations over the Boolean matrix is left an unsolved problem. The paper shows theorems that can reduce the computation time, discusses an algorithm for efficient J relation computation whose design reflects those theorems and gives its execution results.

D-class computation requires multiplication of three Boolean matrices for each of all possible triples of Boolean matrices and search for equivalent Boolean matrices according to a specific equivalence relation. It is easy to see that even multiplying all Boolean matrices with themselves shows exponential time complexity and D-Class computation was left an unsolved problem due to its computational complexity. The vector-based multiplication theory shows that the multiplication of three Boolean matrices for each of all possible triples of Boolean matrices can be done much more efficiently. However, D-Class computation requires computation of equivalent classes in addition to the efficient multiplication. The paper discusses a theory and an algorithm for efficient D-class computation, and shows execution results of the algorithm.

Boolean matrices are applied to a variety of areas and used successfully in many applications, and there are many researches on boolean matrices. Most researches deal with the multiplication of boolean matrices, but all of them focus on the multiplication of two boolean matrices and very few researches deal with the multiplication between many nm boolean matrices and all mk boolean matrices. The paper discusses the existing optimal algorithms for the multiplication of two boolean matrices are not suitable for the multiplication between a nm boolean matrix and all mk boolean matrices, establishes a theory that enables the efficient multiplication of a nm boolean matrix and all mk boolean matrices, and shows the execution results of a multiplication algorithm designed with this theory.

Conventional and public-key cryptography has been widely accepted as a base technology for the design of computer security systems. D-classes have the potential for application to conventional and public-key cryptography. However, there are very few results on D-classes because the computational complexity of D-class computation is NP-complete. This paper discusses the design of algorithms for the efficient computation of D-classes and the Java implementation of them. In addition, the paper implements the same D-class computation algorithms in C and shows the performance of C and Java programming languages for the computation-intensive applications by comparing their execution results.

No abstract available.