Information-Centric Networking (ICN) technology has recently been attracting substantial interest in the research community as one of the most promising future Internet architectures. The Named Data Networking (NDN) approach, which is one of the most recent instantiations of the ICN approach, would be a good choice for multimedia services, because NDN utilizes in-network storage embedded in NDN routers by caching recently or frequently requested contents. It is important to determine which data to cache at which NDN routers in order to achieve high performance, by considering not only the popularity of contents but also the inter-chunk popularity of a content item. This paper presents a chunk-block-based incremental caching scheme that considers both content and inter-chunk popularity. Our proposed scheme employs an incremental cache populating mechanism, which utilizes not only core-side but also edge-side NDN routers according to the request rate of the content item. Through simulations, we show that the proposed scheme achieves less delay, reduced redundant network traffic, and a higher cache hit ratio than legacy schemes.

In this work, we propose general, practical and accurate models to analyze the performance of multi-cache systems, in which a cache forwards its miss stream (i.e., requests which have not found the target item) to other caches. We extend a miss stream modeling technique originally known as Melazzi's approximation, which provides a simple but accurate approximate analysis for caches with cascade configurations. We consider several practical replication strategies, which have been commonly adopted in the context of ICN, taking into account the effects of temporal locality. Also, we capture the existing state correlations between neighboring caches by exploiting the cache eviction time. Our proposed models to handle traffic patterns allow us to go beyond the standard Poisson approximation under Independent Reference Model. Our results, validated against simulations, provide interesting insights into the performance of multi-cache systems with different replication strategies.

Many distributed systems use a replication mechanism for reliability and availability. On the other hand, application developers have to consider minimum consistency requirement for each application. Therefore, a replication protocol that supports multiple consistency models is required. Multi-Consistency Data Replication (McRep) is a proxy-based replication protocol and can support multiple consistency models. However, McRep has a potential problem in that a replicator relaying all request and reply messages between clients and replicas can be a performance bottleneck and a Single-Point-of-Failure (SPoF). In this paper, we introduce the multi-consistency support mechanism of McRep to a combined state-machine and deferred-update replication protocol to eliminate the performance bottleneck and SPoF. The state-machine and deferred-update protocols are well-established approaches for fault-tolerant data management systems. But each method can ensure only a specific consistency model. Thus, we adaptively select a replication method from the two replication bases. In our protocol, the functionality of the McRep's replicator is realized by clients and replicas. Each replica has new roles in serialization of all transactions and managing all views of the database, and each client has a new role in managing status of its transactions. We have implemented and evaluated the proposed protocol and compared to McRep. The evaluation results show that the proposed protocol achieved comparable throughput of transactions to McRep. Especially the proposed protocol improved the throughput up to 16% at a read-heavy workload in One-Copy. Finally, we demonstrated the proposed failover mechanism. As a result, a failure of a leader replica did not affect continuity of the entire replication system unlike McRep.

We propose subquadratic space complexity multipliers for any finite field $mathbb{F}_{q^n}$ over the base field $mathbb{F}_q$ using the Dickson basis, where q is a prime power. It is shown that a field multiplication in $mathbb{F}_{q^n}$ based on the Dickson basis results in computations of Toeplitz matrix vector products (TMVPs). Therefore, an efficient computation of a TMVP yields an efficient multiplier. In order to derive efficient $mathbb{F}_{q^n}$ multipliers, we develop computational schemes for a TMVP over $mathbb{F}_{q}$. As a result, the $mathbb{F}_{2^n}$ multipliers, as special cases of the proposed $mathbb{F}_{q^n}$ multipliers, have lower time complexities as well as space complexities compared with existing results. For example, in the case that n is a power of 3, the proposed $mathbb{F}_{2^n}$ multiplier for an irreducible Dickson trinomial has about 14% reduced space complexity and lower time complexity compared with the best known results.

Named Data Networking (NDN) has emerged as an alternative to traditional IP-based networking for the achievement of Information-Centric Networking (ICN). Currently, most NDN is deployed over IP networks, but such an overlay deployment increases the transport network overhead due to the use of dual network control planes (NDN routing and IP routing). Software-Defined Networking (SDN) can be used to mitigate the network overhead by forwarding NDN packets without the use of IP routing. However, to deploy NDN over SDN, a variable NDN content name needs to be mapped to a fixed-size match field in an OpenFlow switch flow table. For efficient support of such a mapping task, we propose a new architecture that uses dual name for content: content name and Name Tag. The Name Tag is derived from the corresponding content name and is a legitimate IPv6 address. By using the proposed Name Tag, the SDN with an NDN control application can transport an IPv6 packet that encapsulates an NDN packet for an NDN name-based routing. We emulate the proposed architecture using Mininet and verify that it is feasible.

A 10-bit 20-MS/s asynchronous SAR ADC with a meta-stability detector using replica comparators is proposed. The proposed SAR ADC with the area of 0.093mm2 is implemented using a 130-nm CMOS process with a 1.2-V supply. The measured peak ENOBs for the full rail-to-rail differential input signal is 9.6bits.

We present a hierarchical replicated state machine (H-RSM) and its corresponding consensus protocol D-Paxos for replication across multiple data centers in the cloud. Our H-RSM is based on the idea of parallel processing and aims to improve resource utilization. We detail D-Paxos and theoretically prove that D-Paxos implements an H-RSM. With batching and logical pipelining, D-Paxos efficiently utilizes the idle time caused by high-latency message transmission in a wide-area network and available bandwidth in a local-area network. Experiments show that D-Paxos provides higher throughput and better scalability than other Paxos variants for replication across multiple data centers. To predict the optimal batch sizes when D-Paxos reaches its maximum throughput, an analytical model is developed theoretically and validated experimentally.

A new gain enhancement technique for an operational amplifier (opamp) using a replica amplifier is presented to reduce a sensitivity of a gain mismatch between the main amplifier and the replica amplifier which limits a gain-enhancement factor in the conventional replica-amp techniques. In the proposed technique, the replica amplifier is used to only amplify an error voltage of the main amplifier. The outputs of the main amplifier and the replica amplifier are added to cancel the error voltage of the main amplifier. The proposed technique can also achieve a higher output voltage swing because the replica amplifier amplifies only the error voltage. In case of using a fully-differential common-source opamp for the main amplifier and a telescopic opamp for the replica amplifier, Monte Carlo simulation at 100 iterations shows that the proposed amplifier has almost the same gain variation with 15.5dB gain enhancement and about five times output voltage swing expanding for a supply voltage of 1.2V compared with the single closed-loop amplifier using the telescopic opamp.

In many radio frequency identification (RFID) applications, the reader identifies the tags in its scope repeatedly. For these applications, many algorithms, such as an adaptive binary splitting algorithm (ABS), a single resolution blocking ABS (SRB), a pair resolution blocking ABS (PRB) and a dynamic blocking ABS (DBA) have been proposed. All these algorithms require the staying tags to reply with their IDs to be recognized by the reader. However, the IDs of the staying tags are stored in the reader in the last identification round. The reader can verify the existence of these tags when identifying them. Thus, we propose an anti-collision algorithm with short reply for RFID tag identification (ACSR). In ACSR, each staying tag emits a short reply to indicate its continued existence. Therefore, the data amount transmitted by staying tags is reduced significantly. The identification rate of ACSR is analyzed in this paper. Finally, simulation and analysis results show that ACSR greatly outperforms ABS, SRB and DBA in terms of the identification rate and average amount of data transmitted by a tag.

A field multiplication in the extended binary field is often expressed using Toeplitz matrix-vector products (TMVPs), whose matrices have special properties such as symmetric or triangular. We show that such TMVPs can be efficiently implemented by taking advantage of some properties of matrices. This yields an efficient multiplier when a field multiplication involves such TMVPs. For example, we propose an efficient multiplier based on the Dickson basis which requires the reduced number of XOR gates by an average of 34% compared with previously known results.

The main purpose of this paper is to propose overtime replacement policies for the system which has a finite life cycle. The newly proposed overtime technique, where the system is replaced preventively at the first completion of some working cycle over a planned time T, is employed into modelings to avoid operational interruptions for successive jobs. We consider two overtime replacement model with finite operating interval which S is given as (i) constant interval, and (ii) random interval. The expected replacement costs per unit of time are obtained and their optimal solutions are discussed analytically. Further, numerical examples are given when the failure time has a Weibull distribution and working cycles are exponentially distributed.

High-availability seamless redundancy (HSR) is a fault-tolerant protocol for Ethernet networks that provides two frame copies for each frame sent. Each copy is forwarded on a separate physical path. HSR is a potential candidate for several fault-tolerant Ethernet applications including smart grid communications. However, one of the drawbacks of the HSR protocol is that it generates and circulates unnecessary frames within connected rings regardless of the presence of a destination node in the ring. This downside will degrade network performance and may deplete network resources. Previously, we proposed a simple but efficient approach to solving the above problem, namely, port locking (PL), which is based on the media access control address. The PL approach enables the network to learn the locations of the source and destination nodes gradually for each connection pair without using network control frames; the PL then prunes all the rings that do not contain the destination node by locking the corresponding ring's entrance ports at its QuadBox node. In this paper, we present an enhanced port-locking (EPL) approach that increases the number of pruned unused HSR rings. The analysis and corresponding simulation results show that the network traffic volume is significantly reduced for a large-sized HSR connected-rings network and consequently, network performance is greatly improved compared to the standard HSR protocol, and even PL.

Throughput capacity is of great importance for the design and performance optimization of mobile ad hoc networks (MANETs). We study the exact per node throughput capacity of MANETs under a general 2HR-(g, x, f) routing scheme which combines erasure coding and packet replication techniques. Under this scheme, a source node first encodes a group of g packets into x (x ≥ g) distinct coded packets, and then replicates each of the coded packets to at most f relay nodes which help to forward them to the destination node. All original packets can be recovered once the destination node receives any g distinct coded packets of the group. To study the throughput capacity, we first construct two absorbing Markov chain models to depict the complicated packet delivery process under the routing scheme. Based on these Markov models, an analytical expression of the throughput capacity is derived. Extensive simulation and numerical results are provided to verify the accuracy of theoretical results on throughput capacity and to illustrate how system parameters will affect the throughput capacity in MANETs. Interestingly, we find that the replication of coded packets can improve the throughput capacity when the parameter x is relatively small.

Risk-aware Data Replication (RDR), which replicates data at primary sites to nearby safe backup sites, has been proposed to mitigate service disruption in a disaster area even after a widespread disaster that damages a network and a primary site. RDR assigns a safe backup site to a primary site while considering damage risk for both the primary site and the backup candidate site. To minimize the damage risk of all site-pairs the Integer Programing Problem (IPP), which is a mathematical optimization problem, is applied. A challenge for RDR is to choose safe backup sites within a short computation time even for a huge number of sites. As described in this paper, we propose a Discreet method for RDR to surmount this hurdle. The Discreet method first judges the backup sites of a potentially unsafe primary site and avoids assigning a very safe primary site with a very safe backup site. We evaluated the computation time for site-paring and the data availability in the cases of Earthquake and Tsunami using basic disaster simulations. We confirmed that the computation rate of the proposed method is more than 1000 times faster than the existing method when the number of sites is greater than 1000. We also confirmed the data availability of the proposed method; it provides almost equal rates to existing methods of strict optimization. These results mean that the proposed method makes RDR more practical for massively multiple sites.

This paper presents a constant-current-controlled class-C VCO using a self-adjusting replica bias circuit. The proposed class-C VCO is more suitable in real-life applications as it can maintain constant current which is more robust in phase noise performance over variation of gate bias of cross-coupled pair comparing to a traditional approach without amplitude modulation issue. The proposed VCO is implemented in 180,nm CMOS process. It achieves a tuning range of 4.8--4.9,GHz with a phase noise of -121,dBc/Hz at 1,MHz offset. The power consumption of the core oscillators is 4.8,mW and an FoM of -189,dBc/Hz is achieved.

Distributed file systems, which manage large amounts of data over multiple commercially available machines, have attracted attention as management and processing systems for Big Data applications. A distributed file system consists of multiple data nodes and provides reliability and availability by holding multiple replicas of data. Due to system failure or maintenance, a data node may be removed from the system, and the data blocks held by the removed data node are lost. If data blocks are missing, the access load of the other data nodes that hold the lost data blocks increases, and as a result, the performance of data processing over the distributed file system decreases. Therefore, replica reconstruction is an important issue to reallocate the missing data blocks to prevent such performance degradation. The Hadoop Distributed File System (HDFS) is a widely used distributed file system. In the HDFS replica reconstruction process, source and destination data nodes for replication are selected randomly. We find that this replica reconstruction scheme is inefficient because data transfer is biased. Therefore, we propose two more effective replica reconstruction schemes that aim to balance the workloads of replication processes. Our proposed replication scheduling strategy assumes that nodes are arranged in a ring, and data blocks are transferred based on this one-directional ring structure to minimize the difference in the amount of transfer data for each node. Based on this strategy, we propose two replica reconstruction schemes: an optimization scheme and a heuristic scheme. We have implemented the proposed schemes in HDFS and evaluate them on an actual HDFS cluster. We also conduct experiments on a large-scale environment by simulation. From the experiments in the actual environment, we confirm that the replica reconstruction throughputs of the proposed schemes show a 45% improvement compared to the HDFS default scheme. We also verify that the heuristic scheme is effective because it shows performance comparable to the optimization scheme. Furthermore, the experimental results on the large-scale simulation environment show that while the optimization scheme is unrealistic because a long time is required to find the optimal solution, the heuristic scheme is very efficient because it can be scalable, and that scheme improved replica reconstruction throughput by up to 25% compared to the default scheme.

In several important applications, we often encounter with the computation of a Toeplitz matrix vector product (TMVP). In this work, we propose a k-way splitting method for a TMVP over any field F, which is a generalization of that over GF(2) presented by Hasan and Negre. Furthermore, as an application of the TMVP method over F, we present the first subquadratic space complexity multiplier over any finite field GF(pn) defined by an irreducible trinomial.

We propose TagFlow, a data plane mechanism for classification in Software-Defined Networking (SDN). We first argue that simple field-matching proposals of current SDN APIs are not efficient and flexible enough and then propose a tag based classification mechanism as an alternative. Moreover, we propose user-defined actions as an improvement over current hardcoded actions in SDN APIs. Our experiments show TagFlow forwarding is almost 40% faster than OpenFlow. Furthermore, our user-defined actions at SDN southbound are thousands of times faster that equivalent northbound implementations in the literature.

Information-centric networking (ICN) is a promising architecture and has attracted much attention in the area of future Internet architectures. As one of the key technologies in ICN, in-network caching can enhance content retrieval at a global scale without requiring any special infrastructure. In this paper, we propose a workload-aware caching policy, LRU-GT, which allows cache nodes to protect newly cached contents for a period of time (guard time) during which contents are protected from being replaced. LRU-GT can utilize the temporal locality and distinguish contents of different popularity, which are both the characteristics of the workload. Cache replacement is modeled as a semi-Markov process under the Independent Reference Model (IRM) assumption and a theoretical analysis proves that popular contents have longer sojourn time in the cache compared with unpopular ones in LRU-GT and the value of guard time can affect the cache hit ratio. We also propose a dynamic guard time adjustment algorithm to optimize the performance. Simulation results show that LRU-GT can reduce the average hops to get contents and improve cache hit ratio.

NAND flash storage devices, such as eMMCs and microSD cards, are now widely used in mobile devices. In this paper, we propose a novel buffer replacement scheme for mobile NAND flash storages. It efficiently improves write performance by evicting pages flash-friendly and maintains high cache hit ratios by managing pages in order of recency. Our experimental results show that the proposed scheme outperforms the best performing scheme in the recent literature, Sp.Clock, by 48%.