Search

Most existing cross-domain recommendation (CDR) systems apply the embedding and mapping idea to tackle the cold-start user problem and, to this end, they learn a common bridge function to transfer the user preferences from the source domain into the target domain. However, sharing a bridge function for all users inevitably leads to biased recommendations. This paper proposes a novel method, named CDR to cold-start users via categorized preference transfer (CDRCPT), to overcome the shortcomings of existing approaches. First, the embeddings of users and items in both the source and target domain are learned through pretraining and we utilize preference encoder to obtain the preference embeddings of users in the source domain. Second, mini-batch clustering is applied in the source domain to group users according to their preferences; here, each cluster identifies a specific class of users, and each cluster is represented by its center. Finally, the general representation is fed into a meta network to learn a bridge function for each available class of users. Experiments on two real data sets show that our CDRCPT method is effective in improving the accuracy and robustness of recommendations. [ABSTRACT FROM AUTHOR]

Log blockchain can be used to ensure the integrity of log data. However, current methods are facing the problems of throughput mismatch and rough audit granularity. Packaging multiple logs to generate integrity proofs improves throughput but reduces audit granularity, and the auditor can only locate the tampering log packet instead of specific records. This paper proposes CFAuditChain, an audit blockchain based on a cuckoo filter, where the proof of existence (PoE) of the single log is calculated while calculating the integrity proof of packet logs. The PoE is saved in the cuckoo filter and stored using blockchain for immutability. Therefore, the auditor can verify the credibility of each log based on the filter when the integrity proof of a log packet does not match. The theoretical analysis and experimental results show that CFAuditChain provides the granularity of audit logs down to the records level at an acceptable cost. [ABSTRACT FROM AUTHOR]

The problem of detecting communities in real-world networks has been extensively studied in the past, but most of the existing approaches work on single-domain networks , i.e. they consider only one type of relationship between nodes. Single-domain networks may contain noisy edges and they may lack some important information. Thus, some authors have proposed to consider the multiple relationships that connect the nodes of a network, thus obtaining multi-domain networks. However, most community detection approaches are limited to multi-layer networks , i.e. networks generated from the superposition of several single-domain networks (called layers) that are regarded as independent of each other. In addition to being computationally expensive, multi-layer approaches might yield inaccurate results because they ignore potential dependencies between layers. This paper proposes a multi-domain discrete-time quantum walks (MDQW) model for multi-domain networks. First, the walking space of network nodes in multi-domain network is constructed. Second, the quantum permutation circuit of the coin state is designed based on the coded particle state. Then, using different coin states, the shift operator performs several quantum walks on the particles. Finally, the corresponding update rule is selected to move the node according to the measurement result of the quantum state. With continuous update iteration, the shift operator automatically optimizes the discovered community structure. We experimentally compared our MDQW method with four state-of-the-art competitors on five real datasets. We used the normalized mutual information (NMI) to compare clustering quality, and we report an increase in NMI of up to 3.51 of our MDQW method in comparison with the second-best performing competitor. The MDQW method is much faster than its competitors, allowing us to conclude that MDQW is a useful tool in the analysis of large real-life multi-domain networks. Finally, we illustrate the usefulness of our approach on two real-world case studies. [ABSTRACT FROM AUTHOR]

Link residual closeness is a newly proposed measure for network vulnerability. In this model, vertices are perfectly reliable and the links fail independently of each other. It measures the vulnerability even when the removal of links does not disconnect the graph. In this paper, we characterize those graphs that maximize the link residual closeness over the connected graphs with fixed order and one additional parameter such as connectivity, edge connectivity, bipartiteness, independence number, matching number, chromatic number, number of cut vertices and number of cut edges. [ABSTRACT FROM AUTHOR]

Multi-dimensional packet classification is one of the most important functions to support various services in next generation routers. Both the memory-efficient data structure to support larger rule tables and the hardware architecture to achieve a higher throughput are desired. In this paper, we propose a parallel and pipelined architecture called Set-Pruning Segment Trees with Buckets (SPSTwB) for multi-dimensional packet classification. SPSTwB significantly reduces rule duplication based on a novel partitioning scheme and an efficient bucket merging scheme. The key feature of our proposed architecture is that memory consumption is reduced significantly regardless of the characteristics of various rule tables. In addition, the logic complexity of each pipeline stage is simplified by not storing rule IDs and priorities and thus it can run at a high clock rate. The proposed scheme needs less than 20 bytes per rule for various 100 K rule tables generated by ClassBench. In addition, the proposed scheme supports fast incremental rule update. The proposed pipelined architecture can achieve a throughput of 134 Gbps from the implementation on Xilinx Virtex-7 FPGA device with dual-ported Block RAM. [ABSTRACT FROM AUTHOR]

This research presents a new problem maximum scatter colored traveling salesman problem (MSCTSP), the objective of MSCTSP is to find Hamiltonian cycles with the minimal edge as max as possible, it is used to simulate the real-world applications of network and transport. Since MSCTSP has been proved to be a NP-hard problem, population-based algorithms can be used for solving it. However, the performances are not satisfactory. Thus, it is necessary to develop novel algorithms to obtain high quality feasible solution. Based on the above reason, the paper proposes a novel hybrid ITÖ (HITÖ) algorithm, which integrates the two new strategies: crossover operator and mutation strategy, into the standard ITÖ. In the iteration course of HITÖ, the dual-chromosome coding is used to code a feasible solution of MSCTSP, and the stochastic drift and volatility operators are used to explore and exploit new unknown region. During the process, drift operator is performed by crossover operator, volatility operator is carried out by mutation strategy, and they are both affected by activity intensity of particles which functionally depends on the radius and temperature. Experiments display HITÖ shows an improvement over comparative algorithms on solution quality. [ABSTRACT FROM AUTHOR]

According to Menger's theorem, connectivity and edge connectivity are closely related to node-disjoint paths and edge-disjoint paths, respectively. Node- and edge-disjoint paths can keep the effective transmission of information and confidentiality. Therefore, node-disjoint paths and edge-disjoint paths are two important parameters to measure the reliability of a network. For a faulty node (resp. edge) set |$S\subset V$| (resp. |$S\subset E$|⁠), a connected graph |$G=(V,E)$| is |$S$| -strongly Menger-node-connected (resp. Menger-edge-connected) if any two distinct nodes |$x$| and |$y$| in |$G-S$| are connected by |$\min \{\deg _{G-S}(x),\deg _{G-S}(y)\}$| internally node-disjoint (resp. edge-disjoint) paths in |$G-S$|⁠ , where |$\deg _{G-S}(x)$| and |$\deg _{G-S}(y)$| are the degrees of |$x$| and |$y$| in |$G-S$|⁠ , respectively. And most of the previous studies are based on networks that are triangle-free. In this paper, we consider the strongly Menger (edge) connectedness of a class of |$r$| -dimensional recursive networks RNCG |$G_{r}$| with triangles. Moreover, we show that |$G_{r}$| is |$(rl-l-1)$| -strongly Menger-node-connected. And then we show that |$G_{r}$| is |$[k+(r-1)l-2]$| -strongly Menger-edge-connected of order 1 and |$[2k+2(r-1)l-6]$| -strongly Menger-edge-connected of order 2. Since the class of |$r$| -dimensional recursive networks RNCG |$G_{r}$| includes not only data center networks DCell and generalized DCell but also interconnection network dragonfly, etc. all the results are appropriate for these networks. [ABSTRACT FROM AUTHOR]

The article presents a letter made by Donald Davis. The author suggests that the letter was intended for the benefit of historians and other scholars who study the progress of computer networking. It also provides an analysis of various documents that have been cited and publicized in the media as well as on the Internet pages claiming for invention of the packet-switching.

This special issue contains four papers selected from the 26th UK Performance Engineering Workshop (UKPEW), which was held during 8–9 July 2010 in the Department of Computer Science at the University of Warwick. UKPEW is the leading UK forum for the presentation of work relating to all aspects of performance modelling and the analysis of computer and telecommunication systems. This year's selected papers demonstrate the variety of topics on offer at UKPEW: performance issues in cloud computing, energy-aware routing in packet networks, source location privacy and multi-hop ad hoc networks for wireless networks. [ABSTRACT FROM AUTHOR]

When a vehicle requests a video streaming service from the Internet, it may not have enough bandwidth to receive good video quality. In order to resolve this problem, the vehicle is proposed to ask neighboring vehicles to help the video download process using a short-range wireless technique, i.e. Dedicated Short Range Communications (DSRCs). In this paper, this scenario is called cooperative streaming over vehicular networks. Since the topology of vehicular networks changes over time rapidly, three critical issues in the moving-vehicle-based cooperative streaming are: (i) how to form a cooperative group dynamically, (ii) how to schedule neighboring vehicles to help the video download process and (iii) how to estimate the possible change of network conditions. We propose corresponding control schemes to tackle the aforementioned issues in this paper. From the simulation results, we can find that different scheduling schemes are adaptive to different scenarios, and the proposed dynamic group formation scheme has better performance than that of periodic group formation scheme. [ABSTRACT FROM PUBLISHER]

Despite a significant increase in security of modern information systems, cyber attacks have become more sophisticated as attackers combine multiple vulnerabilities to penetrate networks resulting in devastating consequences. In the past, attack graphs had been important tools for analyzing and understanding how various vulnerabilities could be combined through many potential interactions and connections between network components to compromise security. Full attack graphs for a realistic network, however, can be very large and complex, making it difficult to analyze and to decide what changes should be made in the network to make it sufficiently secure. We propose in this paper a novel approach to analyze network vulnerability and to identify all the combinations of exploits that are critical to the overall security of a network. Unlike previous graph-based algorithms that generate attack trees (or graphs) to cover all possible sequences of vulnerabilities, our method directly analyzes and eliminates less critical vulnerabilities without building the actual attack graph. The proposed approach relies on a unique evaluation of a vulnerability metric defined in this paper and its effectiveness is demonstrated through an example of a network that provides voice over IP services. [ABSTRACT FROM AUTHOR]

Efficient fault detection and characterization are crucial requirements for automated network diagnosis systems. In this paper, we present normalized statistical signatures (NSSs), a network ‘soft-failure’ characterization technique for user devices (UDs) based upon exhaustive sets of aggregated statistical features extracted from transmission control protocol (TCP) packet streams. TCP streams are collected on-demand (e.g. upon user complaint) with fixed data transfer limits to capture the artifacts resulting from UD faults. NSSs created using live network and testbed data are able to uniquely characterize many faults and offer insight into how various types of features are affected by the faults and networks. We then introduce the link adaptive signature estimation (LASE) technique to reduce the quantities of collected NSSs required for generalized diagnostic systems with variable link parameters. We create feature estimator functions using multivariate regression techniques to generate artificial NSSs, which are subsequently used to train machine learning systems that have robust generalization capabilities. Performance of a prototype fault classifier system based on NSSs shows that an overall detection accuracy of 98% can be achieved for eight types of faults in a live network environment. In this paper, we specifically focus on formulating the basic framework of NSS and LASE, and limit the analysis to wired networks. This work can later be extended to encompass more complex fixed and mobile wireless networking environments. We expect that the combination of NSSs and LASE can serve as the foundation of next-generation automated network diagnosis systems. [ABSTRACT FROM AUTHOR]

This paper examines efficient and decentralized monitoring of objects moving in a transportation network. Previous work in moving object monitoring has focused primarily on centralized information systems, like moving object databases and geographic information systems. In contrast, in this paper monitoring is in-network, requiring no centralized control and allowing for substantial spatial constraints to the movement of information. The transportation network is assumed to be augmented with fixed checkpoints that can detect passing mobile objects. This assumption is motivated by many practical applications, from traffic management in vehicle ad hoc networks to habitat monitoring by tracking animal movements. In this context, this paper proposes and evaluates a family of efficient decentralized algorithms for capturing, storing and querying the movements of objects. The algorithms differ in the restrictions they make on the communication and sensing constraints to the mobile nodes and the fixed checkpoints. The performance of the algorithms is evaluated and compared with respect to their scalability (in terms of communication and space complexity), and their latency (the time between when a movement event occurs, and when all interested nodes are updated with records about that event). The conclusions identify three key principles for efficient decentralized monitoring of objects moving past checkpoints: structuring computation around neighboring checkpoints; taking advantage of mobility diffusion and separating the generation and querying of movement information. [ABSTRACT FROM AUTHOR]

The Real-Time Specification for Java (RTSJ) is silent on multiprocessor issues. It attempts not to preclude multiprocessor implementations but provides no direct support. Many areas of the RTSJ leave an implementation considerable freedom on how it provides the defined functionality. One such area is the asynchronous event handling (AEH) model. Events are fired and associated handlers are scheduled for execution in response; handlers have defined scheduling parameters and deadlines. The primary goal of the AEH model is to support a lightweight real-time concurrency model. Hence handlers, in general, do not have dedicated threads. Rather, the implementation is responsible for ensuring that all handlers meet their deadlines. Typically real-time threads are assigned to execute handlers by the implementation. This paper discusses the issues associated with implementing the AEH model on multiprocessor systems. The emphasis here is on achieving a lightweight model. A model is lightweight if it is able to meet the deadlines of all handlers with as few as possible real-time threads. In the RTSJ this is made more complicated because asynchronous event handlers are allowed to suspend themselves (for example, by waiting on a monitor condition). Such handlers are called blocking handlers. Most of an implementation's freedom comes from being able to optimize the support for those handlers that do not block. The paper first examines all possible releasing sequences of non-blocking handlers on multiprocessor systems. Based on this, it proposes an efficient and scalable AEH mapping model for multiprocessor systems, which limits the number of real-time threads even in the worst case while retaining the schedulability of the system. The proposed model is then examined to prove its safety and liveness requirements using a model checking tool, UPPAAL. The verification and simulation results of the model indicate that the safety and liveness requirements are satisfied. Most importantly, this paper derives the proposed model's greatest lower and least upper bounds of real-time threads required to execute a given number of non-blocking handlers. The greatest lower bound is equal to the number of processors, and the least upper bound is equal to the number of processors times that of the priority levels in the system. In the model, the number of real-time threads required to execute a given number of non-blocking handlers is restricted to between these two bounds depending on the releasing sequence of handlers. Even in the worst case, the model requires the least upper bound of real-time threads which is, in most cases, considerably less than the actual number of handlers in the system. This, in turn, enables the proposed model to be efficient and scalable by reducing time and space overheads, compared with a traditional 1:1 AEH mapping model where each handler is mapped to a single thread. [ABSTRACT FROM AUTHOR]

This paper presents a simple framework unifying a family of consensus algorithms that can tolerate process crash failures and asynchronous periods of the network, also called indulgent consensus algorithms. Key to the framework is a new abstraction we introduce here, called Alpha, and which precisely captures consensus safety. Implementations of Alpha in shared memory, storage area network, message passing and active disk systems are presented, leading to directly derived consensus algorithms suited to these communication media. The paper also considers the case where the number of processes is unknown and can be arbitrarily large. [ABSTRACT FROM AUTHOR]

Information systems ontology is intended to facilitate interoperability among the many applications which are now becoming available on the Internet. In particular, it is intended to facilitate the development of intelligent agents which can automate a large part of the task of a user achieving some end employing multiple autonomous applications. A large number of ontologies exist supporting specific kinds of interoperation among selected, generally mutually aware, applications. The intent of the upper ontology movement is to develop an abstract description of what there is in the world, in an application-independent form, which can be used both to help build specific ontologies and to help in finding common ground among them. This paper argues that, for the purposes of information systems interoperation and the semantic web, application-independent upper ontologies are unlikely to be successful because of semantic heterogeneity. However, the paper argues for a distinction in upper ontologies between formal and material ontologies, based on analogies with concepts in Kant's synthetic a priori, and that formal ontologies whose focus is on how we see the world are more likely to be successfully developed in the absence of applications than are material ontologies, which attempt to catalog the world a priori. Categories and Descriptors: C.2.4 [Distributed Systems] Distributed Applications, Distributed Databases D.2.12 [Software Engineering] InteroperabilityData Mapping; H.3.5 [Information Storage and Retrieval] Online Information ServicesData Sharing and Web-based Services; H.2.1 [Database Management] Systems. [ABSTRACT FROM AUTHOR]

Pervasive computing is the next generation computing environment with information and communication technology everywhere, for everyone, at any time. There are many methods proposed to reach the ultimate design goals of pervasive computing. Most of them are still at the hypothesis and early stages. In this paper, an initial investigation has been carried out to use active networks as the operating platforms for pervasive computing. Upon taking advantage of the active network paradigm, which offers flexibility and extensibility within networks, the active pervasive network infrastructure (APNI) framework is proposed. An additional feature known as `adaptiveness' is recommended to work in pervasive computing. Primarily, the integrity of information content can be retained and adapted to available network resources, even if an end user moves to an unfavourable network environment as long as the user approves and accepts appropriate modifications of receiving content. Furthermore, information transfer can be sustained through different extensible mechanisms on the network layer in active networks. As a result, information can be sent through the APNI with low packet loss rate. The functional objectives of proposed designs in the paper have been verified through thorough experiments in an active network prototype. [ABSTRACT FROM AUTHOR]

The article discusses the history of packet switching technology in Great Britain. It suggests that the technology can be attributed to Paul Baran of RAND Corp. who proposed it in the context of a digital communication network for military purpose. It cites the role of Leonard Kleinrock in the development of ARPA through the application of queuing theory with the aim of predicting performance of its design.

In Underwater Wireless Sensor Networks (UWSN), the existing scheduling technique causes propagation delay or overhead issue. Also the data collision is likely to occur. In order to overcome this issue, in this paper, we propose to design a cluster-based MAC protocol for collision avoidance and TDMA scheduling in UWSN. Initially, the clusters are formed and cluster heads (CHs) are elected as per the energy-efficient hierarchical clustering algorithm. The cluster members, which are one-hop neighbors of CH, schedule the data sending times for all cluster members. The energy consumption analytical model is derived to show the average energy consumed by each CH. Finally, conflict-free scheduling is performed by using Spatial- Temporal-Confliction-Table. This allows nodes to transmit at the same time as long as their packets arrive during different times at the intended destinations. Simulation results show that the proposed MAC protocol reduces the delay and energy consumption while by increasing the packet delivery ratio. [ABSTRACT FROM AUTHOR]

To solve the problem of group task allocation with time constraints in open and dynamic network environments, this paper proposes a decentralized combinatorial auction-based approach for group task allocation. In the proposed approach, both resource providers and consumers are modeled as intelligent agents. The proposed approach is decentralized, so all the agents are limited to communicating with their neighboring agents. The proposed approach also allows agents to enter and leave the network environments freely, and is robust for the dynamism and openness of the network environments. Tasks in the proposed approach have deadlines, and may need the collaboration of a group of self-interested providers. The experimental results demonstrate that the proposed approach outperforms two well-known task allocation approaches in terms of success rate of task allocation, the individual utility of the agents, the speed of task allocation and scalability. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for evaluating the performance of forwarding strategies for location management in a personal communication services (PCS) mobile network. A forwarding strategy in the PCS network can be implemented by two mechanisms: a forwarding operation which follows a chain of databases to locate a mobile user and a resetting operation which updates the databases in the chain so that the current location of a mobile user can be known directly without having to follow a chain of databases. In this paper, we consider the PCS network as a server whose function is to provide services to the mobile user for ‘updating the location of the user as the user moves across a database boundary’ and ‘locating the mobile user’. We use a Markov chain to describe the behavior of the mobile user and analyze the best time when forwarding and resetting should be performed in order to optimize the service rate of the PCS network. We demonstrate the applicability of our approach with hexagonal and mesh coverage models for the PCS network and provide a physical interpretation of the result. [ABSTRACT FROM AUTHOR]

Single sign-on (SSO) is a new authentication mechanism for the distributed computer network. It allows a legal user to sign-on to multiple servers with a single credential in distributed computer networks. Recently, Chang and Lee have proposed a SSO scheme and claimed that their scheme is secure. However, asWang et al. pointed out, there are two leaks in Chang-Lee scheme. The first leak user to access resources offered by other service providers. The other leak allows an outside attacker to forge a credential and use the forged credential to sign-on to the legal servers. Unfortunately,Wang et al. have not offered any suggestions as to how to mend the leaks. In this paper, we shall point out the third leak of the Chang-Lee scheme and propose a solution to remedy all three of these leaks. The solution will upgrade not only the security level but also the performance efficiency of the Chang-Lee scheme. [ABSTRACT FROM AUTHOR]

Electronic multicoupons are the digital version of paper-based booklet of coupons, which allow a customer to obtain goods or services from a merchant typically with discounts or gifts. In this paper, we propose a multicoupon scheme for multi-merchant environments that enhances the security and the efficiency as regards the previous solution that deals with this kind of scenario. On one hand, our scheme meets basic security requirements (unforgeability, reuse detection), but also unsplittability. This fact will help to increase the trust on the part of merchants. On the other hand, we focus on achieving a high degree of privacy for customers (anonymity, unlinkability, confidentiality) that will contribute to gaining the trust of the involved customers. Moreover, we provide measures to protect honest parties from dishonest participants, keeping in mind the scalability and efficiency of the multicoupon scheme, to attract customers and merchants. In addition, we show by implementation that our proposal outperforms previous solutions of this kind. [ABSTRACT FROM AUTHOR]

Network coding has been shown to improve various performance metrics in computer networks. However, the use of network coding, especially random linear network coding, incurs serious time delay in the decoding process and thus it is imperative to use a network coding implementation that has low decoding latency characteristics, e.g. a parallelized implementation. In this paper, we investigate the problem of parallelizing Pipeline network coding, a variant of random linear coding recently developed in order to alleviate the problems of random linear coding. We propose a novel massively parallelized decoding algorithm leveraging General Purpose Graphics Processing Unit (GPGPU) and show its performance enhancement by up to 100% compared with previous GPGPU-based parallel algorithms via experiments on real systems. [ABSTRACT FROM AUTHOR]

The Information-Centric Networking (ICN) paradigm is shaping the foreseen future Internet architecture by focusing on the data itself rather than its hosting location. It is a shift from a host-centric communication model to a content-centric model supporting among others unique and location-independent content names, in-network caching and name-based routing. By leveraging the easy data access, and reducing both the retrieval delay and the load on the data producer, the ICN can be a viable framework to support the Internet of Things (IoT), interconnecting billions of heterogeneous constrained objects. Among several ICN architectures, the Named Data Networking (NDN) is considered as a suitable ICN architecture for IoT systems. However, its default caching approach lacks a data freshness mechanism, while IoT data are transient and frequently updated by the producer which imposes stringent requirements in terms of information freshness. Furthermore, IoT devices are usually resource-constrained with harsh limitations on energy, memory and processing power. We propose in this paper a caching strategy and a novel cache freshness mechanism to monitor the validity of cached contents in an IoT environment while minimizing the caching process cost. We compared our solution to several relevant schemes using the ccnSim simulator. Our solution exhibits the best system performances in terms of hop reduction ratio, server hit reduction ratio and response latency, yet it provides the lowest cache cost and significantly improves the content validity. [ABSTRACT FROM AUTHOR]

Cooperative Intelligent Transportation Systems (ITS) will turn up to us with safer and more efficient driving environments as well as convenient and infotainment features for future ITS stations. ETSI and ISO are completing the standardization of the building blocks of a reference communication architecture for cooperative ITS. Future ITS stations complying with this set of standards deployed in vehicles, at the roadside infrastructures and within the Internet are expected to communicate with each other through a combination of ITS dedicated communication protocols and legacy Internet protocols. However, in spite of the wide adoption of IPv6 for cooperative ITS communications, relatively little attention has been paid to the security issues related to IPv6 signaling and IPv6 transport communications. In this paper, we present our position on the emerging and urgent IPv6-related security issues that occur in communications between ITS stations complying with the ITS station reference architecture under standardization within ETSI TC ITS and ISO TC204. [ABSTRACT FROM AUTHOR]

This paper presents a probabilistic model-based approach aimed at evaluating quantitative measures to assess the security risks faced by an information system in operation. The proposed approach takes into account the impact of three environmental factors and their interdependencies: the vulnerability life cycle, the behavior of the attackers and the behavior of the system administrator. Several quantitative security measures are defined and evaluated. Two different scenarios are distinguished corresponding to the case where the system vulnerabilities are discovered by a malicious user or by a non malicious user. The proposed models are based on stochastic activity networks and describe the system states resulting from the combined modeling of the three external factors. Five states are distinguished (vulnerable, exposed, compromised, patched and secure) and probability measures are associated to these states to assess the level of risk faced by the system as a result of the vulnerability exploitation process. The parameters of the models, e.g. those characterizing the occurrence of vulnerability life cycle events, are derived from the analysis of public information recorded in vulnerability databases. Several sensitivity analyses are carried out for the two scenarios, in order to quantify and illustrate the impact of various parameters, including the probability of security patch application, the attack rate, etc. [ABSTRACT FROM PUBLISHER]

In (Tucker, J. V. and Zucker, J. I. (2007) Computability of analog networks. Theoret. Comput. Sci., 371, 115–146; Tucker, J. V. and Zucker, J. I. (2011) Continuity of operators on continuous and discrete time streams. Theoret. Comput. Sci., 412, 3378–3403), Tucker and Zucker present a model for the semantics of analog networks operating on streams from topological algebras. Central to their model is a parametrized stream operator representing the network along with a theory that concerns the existence, uniqueness, continuity and computability of a fixed point of that stream operator. We narrow the scope of this paper from general topological algebras to algebras of streams that assume values only from a Banach space. This restriction facilitates the definition of a fairly broad class of stream operators to which the theory described in the above two papers applies. As a demonstration in their original work, the authors provide two case studies: analog networks that model the behavior of simple mass-spring-damper systems. The case studies showcase the theory well, but they seem to require the imposition of somewhat peculiar conditions on the parameters (the masses, the spring constants and the damping coefficients). The extra conditions—while not catastrophic to the case studies—make them somewhat unsatisfying. We show here that while their original mass–spring–damper models do not fall within our new class, they can be trivially reconfigured into equivalent models that do. This modification obviates the extra conditions on the parameters. [ABSTRACT FROM AUTHOR]

Hypercubes are a simple topology frequently used as interconnection network of parallel systems. However, hypercubes connecting a significant number of nodes also have an impractically high number of edges. To address this issue, Ghose and Desai introduced a new topology, hierarchical cubic networks, containing almost half many edges than a hypercube of the same size. In this paper, we describe a node-to-set disjoint-path routing algorithm in a hierarchical cubic network HCN(n) finding node-disjoint paths between one source node and k (k≤n+1) destination nodes in O(knlog k) time complexity. Generated paths have lengths of at most 3n+k+3. [ABSTRACT FROM PUBLISHER]

Causal discovery is highly desirable in science and technology. In this paper, we study a new research problem of discovery of causal relationships in the context of streaming features, where the features steam in one by one. With a Bayesian network to represent causal relationships, we propose a novel algorithm called causal discovery from streaming features (CDFSF) which consists of a two-phase scheme. In the first phase, CDFSF dynamically discovers causal relationships between each feature seen so far with an arriving feature, while in the second phase CDFSF removes the false positives of each arrived feature from its current set of direct causes and effects. To improve the efficiency of CDFSF, using the symmetry properties between parents (causes) and children (effects) in a faithful Bayesian network, we present a variant of CDFSF, S-CDFSF. Experimental results validate our algorithms in comparison with the existing algorithms of causal relationship discovery. [ABSTRACT FROM PUBLISHER]

The use of the Internet for business-critical and real-time services is growing day after day. Random node (link) failures and targeted attacks against the network affect all types of traffic, but mainly critical services. For these services, most of the time it is not possible to wait for the complete network recovery; the best approach is to act in a proactive way by improving redundancy and network robustness. In this paper, we study network resilience and propose a resilience factor to measure the network level of robustness and protection against targeted attacks. We also propose strategies to improve resilience by simple alterations in the network topology. Our proposal is compared with previous approaches, and experimental results on selected network topologies confirmed the effectiveness of the approach. [ABSTRACT FROM PUBLISHER]

The COordinate Rotation DIgital Computer (CORDIC) algorithm is a famous technique for realizing complex arithmetic functions using simple shift-add operations. This paper presents a novel completely scaling-free CORDIC algorithm in rotation mode for high performance hyperbolic computations. We target algorithm level improvements to achieve low area and power-delay product on FPGA. Instead of complex search algorithms, we use the most significant one bit detection technique for micro-rotation sequence identification, which helps in significantly reducing the number of pipelining stages. The proposed technique uses mathematical identities to extend the range of convergence. The eight-staged pipelined architecture implementation requires a ROM in the preprocessing unit for storing the initial coordinate values, while the ROM for storing the elementary angles is eliminated. The FPGA implementation of the proposed processor requires 46.35% less gates and has 31.81% less delay when compared with Xilinx Core IP-CORDIC v3.0. Moreover, on an average it consumes 75.96% less power when compared with Xilinx CORDIC v3.0. Hence, the proposed technique provides an area–power-delay efficient VLSI implementation for calculating hyperbolic functions and exponents. The detailed algorithm design, along with FPGA implementation and area and time complexities, is presented in this paper. [ABSTRACT FROM AUTHOR]

With a formulated game of non-cooperative internet service providers (ISPs), this paper proposes a new framework for apportioning ISP's responsibility in an end-to-end quality of service (QoS) request. The strategy is based on Path-Classification scheme under Nash equilibrium (PC-Nash), which is obtained by classifying paths according to the quantized QoS level. Optimal QoS-level selection of individual ISP is then captured by the Nash equilibrium. To facilitate the game solution searching, a loss network model is derived for the call acceptance probabilities and the expected utility values. Solutions provided by PC-Nash are compared with three conventional policies, i.e. most-effort (ME), least-effort (LE) and equal-distribution (ED). The reported results show the conformity of call acceptance probabilities between mathematical analysis and discrete-event simulations. Furthermore, with the utility functions of practical service models, ME and LE are found to provide comparable utilities to PC-Nash with respect to peer and retail/wholesale service models, respectively, for a network with the same path quality. However, for networks with different path qualities, PC-Nash outperforms all the conventional policies significantly. From this evidence, PC-Nash is thus expected to be useful in QoS provisioning of practical inter-domain networks. [ABSTRACT FROM AUTHOR]

The objective of self-healing key distribution is to enable group users to recover session keys by themselves, without requesting additional transmissions from the group manager (GM), even when they miss some broadcast messages. One major benefit of the self-healing key distribution mechanism is the reduction of energy consumption due to the elimination of such additional transmission. Also in some applications, e.g., uni-directional broadcast channel from the GM, the self-healing key distribution mechanism seems to be the ideal solution. Desired features of self-healing key distribution schemes include energy awareness, short broadcast message, efficient users addition, revocation and so on. A primary challenge is managing the trade-off between providing an acceptable level of security and conserving scarce resources in particular energy which is critical for wireless network operations. Over a decade, a great number of self-healing key distribution schemes have been proposed for establishing a group key amongst a dynamic group of users over an unreliable, or lossy, network. In this paper a comprehensive survey is conducted on the state-of-the-art in the field of self-healing key distribution. First, we clarify the security requirements of self-healing key distribution scheme for their special application environment. Then, we present a classification of self-healing key distribution schemes according to different cryptographic primitives, and give an insight to their features and goals. Furthermore, we consider several problems, namely authentication on broadcast messages, sponsorization and mutual-healing, related to the robustness of self-healing key distribution schemes. At last, we delineate their similarities and differences and outline several future research directions. [ABSTRACT FROM PUBLISHER]

The interconnection network considered in this paper is the k-ary n-cube that is an attractive variance of the well-known hypercube. Many interconnection networks, including the ring, torus and hypercube, that are attractive in both theoretical interests and practical systems can be regarded as the subclasses of the k-ary n-cubes. Stewart and Xiang have investigated the fault-tolerant path embedding properties of the k-ary n-cube [2008, IEEE Trans. Parallel Distrib. Syst., 19 1071–1085]. From their results, we know that the k-ary n-cube is a (2n – 2)-edge-fault-tolerant Hamiltonian for k even. In this paper, we do a further investigation for the fault-tolerant cycle embedding properties of the k-ary n-cubes. First, we introduce a new graph called the ladder-wounded cycle-of-ladders (LWCOL). By embedding the LWCOL into the k-ary n-cubes for k even with at most 2n – 2 edge faults, we show that the k-ary n-cube is (2n – 2)-edge-fault-tolerant bipancyclic for k even; that is, it embeds all cycles of even lengths ranging from 4 to N when there exist at most 2n – 2 edge faults, where N is the order of the network. Since the degree of the k-ary n-cube is 2n, the result is optimal. [ABSTRACT FROM AUTHOR]

The interconnection network considered in this paper is the k-ary n-cube that is an attractive variance of the well-known hypercube. Many interconnection networks that are desirable in both theoretical interests and practical systems, including the ring, torus and hypercube, may be regarded as the subclasses of k-ary n-cubes. In this paper, we investigate the pancycle-connected properties of the k-ary n-cube. We show that the k-ary n-cube is bipancycle-connected for k being even. That is, each pair of vertices x and y is contained by a cycle of each even length ranging from the length of the smallest even cycle that contains x and y to N, where N is the order of the network. We also show that the k-ary n-cube is strictly m-pancycle-connected for k being odd and n ≥ 2, where m = nk - n. That is, each pair of vertices is contained by a cycle of each length ranging from nk - n to N; and nk - n has reached the lower bound of the problem. [ABSTRACT FROM PUBLISHER]

This paper is meant to be an illustration of the use of stochastic geometry for analyzing the performance of routing in large wireless ad hoc (mobile or mesh) networks. In classical routing strategies used in such networks, packets are transmitted on a pre-defined route that is usually obtained by a shortest-path routing protocol. In this paper we review some recent ideas concerning a new routing technique which is opportunistic in the sense that each packet at each hop on its (specific) route from an origin to a destination takes advantage of the actual pattern of nodes that captured its recent (re)transmission in order to choose the next relay. The paper focuses both on the distributed algorithms allowing such a routing technique to work and on the evaluation of the gain in performance it brings compared to classical mechanisms. On the algorithmic side, we show that it is possible to implement this opportunistic technique in such a way that the current transmitter of a given packet does not need to know its next relay a priori, but the nodes that capture this transmission (if any) perform a self-selection procedure to choose the packet relay node and acknowledge the transmitter. We also show that this routing technique works well with various medium access protocols (such as Aloha, CSMA, TDMA). Finally, we show that the above relay self-selection procedure can be optimized in the sense that it is the node that optimizes some given utility criterion (e.g. minimize the remaining distance to the final destination), which is chosen as the relay. The performance evaluation part is based on stochastic geometry and combines simulation as analytical models. The main result is that such opportunistic schemes very significantly outperform classical routing schemes when properly optimized and provided at least a small number of nodes in the network know their geographical positions exactly. [ABSTRACT FROM PUBLISHER]

There are two types of dynamic elements in a pervasive system: the first is where a context varies with shifting environments, and the second is where variables are defined by the dynamic requirements of an application. This makes improving adaptability to dynamic change an important topic in pervasive systems research. Currently, most of the efforts targeting improvements in adaptability focus on context-related issues, other variables being simply encoded in the program directly. This ignores the dynamic complexity of a pervasive system, resulting in poor system adaptability. In this paper, we propose a rule-based method in which the two types of change are separated from the program code. The changes are then stored and processed by means of corresponding rules. In our new method when a change occurs, the system needs only to modify the rules rather than the program code. This makes a pervasive system more robust in its adaptability to dynamic change. Experiments and examples are provided to evaluate the feasibility of the proposed method. [ABSTRACT FROM PUBLISHER]

The trend in network processing is towards layer 4-7 processing in the routers and switches. In this paper, we present a hybrid network processor (NPU) architecture that supports high-speed execution of higher layer TCP/IP protocol processing. The architecture achieves this by employing optimized logic blocks for specific tasks in the processing elements. This is a unique architecture such that it can realize both task-level and packet-level parallelism. We also present an example of implementation of a fast adaptive routing algorithm, Cognitive Packet Networks (CPNs), using the proposed NPU architecture. CPN uses a neural network model with a reinforcement learning algorithm to find routes. The applicability of the CPN concept has been demonstrated through several software implementations. Through hardware implementation, we show that this new network model can sustain similar line rates as the current IP protocols. [ABSTRACT FROM AUTHOR]

The main activities leading towards a testbed validation of routing protocols for MANETs involve code development and experimentation. Because of the characteristics of such networks, these activities are commonly obstructed by the need of managing parameters inherently difficult to control in real situations, such as the position of the nodes or the starting residual energy of mobiles. This paper discusses a possible solution to the problem and presents an implementation of the proposal. The MANET testbed manager (MTM) is a system that allows setting up reproducible testbed scenarios useful for code development, initial validation and visualization. The main purpose of MTM is to simulate the main physical elements that can be found in a mobile network while allowing a MANET routing protocol operate concurrently being unaware of the underlying simulation. [ABSTRACT FROM AUTHOR]

The eXtensible Markup Language (XML) and XML-Schema are increasingly becoming the languages of choice to exchange data and describe data across the Internet, respectively. In this perspective, much of the database research focus is shifting from the traditional database models to the semistructured data and XML. In this paper, a formal framework supporting the design of XML-Schema type hierarchies has been proposed, by following and revisiting the database approach. In particular, the notion of a legal XML-Schema type hierarchy has been formally given and an algorithm for checking the legality of type hierarchies has been proposed. [ABSTRACT FROM AUTHOR]

Bluetooth has a master-slave configuration called a piconet. Unspecified in the Bluetooth standard, the link polling policy adopted by a master may significantly influence the bandwidth utilization of a piconet. Several works have been dedicated to this issue. However, none of them addresses the asymmetry of traffics between masters and slaves, and the different data packet types provided by Bluetooth are not fully exploited. In this paper, we propose an efficient pattern matching polling (PMP) policy for data link scheduling that properly resolves these deficiencies. A polling pattern is a sequence of Bluetooth packets of different type combinations (e.g. DH1IDH3IDH5IDM1IDM3IDMS) to be exchanged by a master-slave pair that can properly reflect the traffic ratio (i.e. asymmetry) of the pair. By judiciously selecting a proper polling pattern together with polling times for the link, the precious wireless bandwidth can be better utilized. The ultimate goal is to reduce the unfilled, or even null, payloads in each busy slot. In addition, an overflow mechanism is included to handle unpredictable traffic dynamics. Extensive simulations are presented to justify the capability of PMP in handling regular as well as bursty traffics. [ABSTRACT FROM AUTHOR]

Interval routing is a space-efficient routing method for computer networks. The method is said to be optimal if it can generate optimal routing paths for any source-destination node pair. A path is optimal if it is a shortest path between the two nodes involved. A seminal result in the area, however, has pointed out that ‘the interval routing algorithm cannot be optimal in networks with arbitrary topology’. The statement is correct but the lower bound on the longest routing path that was derived is not. We give the counterproof in this paper and the corrected bound. [ABSTRACT FROM AUTHOR]

With increase in the use of wireless enabled devices and the rapid proliferation of cell phones with demand for voice and data services have necessitated the identification of additional frequency spectrum or judicious use of the currently persisting spectrum. The term cognitive radio (CR) is apt for spectrum access. Deployment of aCRnetwork involves spectrum sensing, spectrum exploitation, performance evaluation and optimization at different levels in the network. The importance of ubiquitous wireless access to the Internet has been constantly growing in the last years, a wireless application becomes more and more sophisticated and widely used, the demand for more bandwidth will increase substantially, in order to compete the growing demand, one has to consider new concepts of better way of utilizing the spectral resources. This paper deals with the Comparatative Performance Analysis of Filter Bank Multicarrier Prototype Filter under the effect of Tero, Bellanger and Phydas Filter Coefficients. In this paper, simulation analysis of multirate filter structures is done which reflects the modifications in Prototype Filter design. Multicarrier modulation is the apt choice for good data rate wireless communication. In multicarrier communication, the perfect reconstruction is the prime requirement for all structures with alias cancellation at Different K (Overlapping factor) values when Lp = K × M - 1 - D, M = N, N being number of subcarriers and Lp being prototype filter length, D being delay. The Performance Analysis of a Cascade Integrator Comb prototype Filter bank in the context of Filter Bank-based Multicarrier Transmission for CR has also been done here. A benefit of the chosen technique is that, a CIC filter can be designed with a slight adjustment in parameters of interest. The entire performance of the filters designed is analysed and evaluated by analysing Normalized Amplitude versus Normalized Frequency plots at typical K and N values. The roll off factor plays a significant role in performance analysis of CIC filter. Whatsoever results are obtainable are presented for useful analysis to the radio frequency design engineers working in the domain of multirate signal processing for wireless communication. [ABSTRACT FROM AUTHOR]

Cloud-based file systems are widely accepted and adopted for personal and business purposes in recent years. Statistics shows that ~25% of file operations from a typical user are random writes. Inherited from traditional disk-based file systems, most distributed file systems are also based on objects or chunks of fixed sizes, which work well for sequential writes but poorly for random writes. This paper investigates the design paradigm of variable-sized objects for a distributed file system, where a new file write interface is proposed to provide rich write semantics. A novel distributed file system named VarFS, is presented to incorporate variable object indexing, support the random write interface and remain POSIX compatible. VarFS reduces the amount of unnecessary data being read and the number of objects modified in face of updates and consequently alleviates the total amount of data transferred. VarFS is implemented based on Ceph and the performance measurements show that it can achieve 1-2 orders of magnitude less latency than Ceph on random writes. At the same time, the overhead for initial writes and re-writes is acceptable. [ABSTRACT FROM AUTHOR]

The failure on all homogeneous devices due to the same reason is called homogeneous fault in networks. In contrast, heterogeneous platforms deployed simultaneously in the network are more robust against homogeneous faults. One of the challenging problems is how to design survivable networks that against homogeneous faults. This paper utilizes edge-colored graphs to investigate the network topology with homogeneous faults, in order to guarantee network connectivity using minimum number of links. Two types of network topologies are proposed on the edge-colored graph. One type of networks is characterized by the fact that all the edges of the same color form a Hamiltonian path or a Hamiltonian cycle. An upper bound on the number of colors used in the proposed network topologies is obtained. The network topologies of the second type have edges colored with at most five colors. Additionally, the subnetworks induced by the edges of two colors contain a Hamiltonian path, or a Hamilton cycle in some cases. [ABSTRACT FROM AUTHOR]

Hardware signatures based on Bloom filters are used to support and accelerate membership query in a set of items. They use modest hardware at the cost of false positives, but never produce false negatives. Signatures were traditionally used in different distributed and network applications, but in recent years their use has been extended to other fields (for instance, support for manycore/multicore parallel programming, such as data race detection, deterministic replay or transactional memory (TM)). One drawback of signatures is that they have a fixed size, and what is a good signature size for one application, may be not appropriate for another. Recently, we proposed a shared hardware module for managing signatures based on a collection of Bloom filters. It has the characteristic of hosting a variable number of signatures that change their size in runtime to adapt to the demand of the applications. However, the assignment of resources follows a single symmetric policy for all allocations leading to a module with a limited adaptability to the workloads. In this paper, we explore new techniques to allocate signatures in an asymmetric way in this module, with the aim of optimizing the resources and reducing even more the number of false positives. We explore several asymmetric strategies and their efficient hardware implementation, and we show specific examples usingTMas a driver application. The results show that these strategies lead to a significant reduction in the number of false positives compared with symmetric policies. [ABSTRACT FROM AUTHOR]

The degree distribution is an important characteristic of complex networks. In many data analysis applications, the networks should be represented as fixed-length feature vectors and therefore the feature extraction from the degree distribution is a necessary step. Moreover, many applications need a similarity function for comparison of complex networks based on their degree distributions. Such a similarity measure has many applications, including classification and clustering of network instances, evaluation of network sampling methods, anomaly detection and study of epidemic dynamics. The existing methods are unable to effectively capture the similarity of degree distributions, particularly when the corresponding networks have different sizes. In this paper, we propose a feature extraction method and a similarity function for the degree distributions in complex networks. We propose to calculate the feature values based on the mean and standard deviation of the node degrees in order to decrease the effect of the network size on the extracted features. Experiments on a wide range of real and artificial networks confirms the accuracy, stability and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Loosely coupled and cross-platform features make Web services accessible and increasingly popular on the Internet. However, efficient service discovery and automated service composition are still challenges under the conventional practice where services are organized into categories. In this paper, we propose a graph-based method to organize Web services into a service ecosystem interlaced with service relationships at the semantic level. First, Web services are modelled as a set of interfaces, whose input and output parameters are annotated with well-defined ontologies. Secondly, semantic associations and interactions between Web services are mined, and services are constructed into a Web services network (SN), a variant of bipartite graph, by projecting the functional aspects of concrete Web services onto the abstract service layer. Thirdly, from the complex network perspective, the services relations are investigated and the structure of SN is analysed. To demonstrate the basic topological properties of SN, an empirical study is conducted on two data sets for comparative purposes, 10000+ Web services collected from the Internet and 1231 Web services provided by Titan system of Zhejiang University. The experimental results reveal that SNs, which are built by different data sets on the semantic level, exhibit the same features such as small-world and scale-free. In addition, our results yield valuable insight for developing service discovery and automated composition algorithms, and characterizing the evolution of the entire Web service ecosystem. [ABSTRACT FROM AUTHOR]

Computing network paths under worst-case delay constraints has been the subject of abundant literature in the past two decades. Assuming weighted fair queueing scheduling at the nodes, this translates to computing paths and reserving rates at each link. The problem is NP-hard in general, even for a single path; hence polynomial-time heuristics have been proposed in the past that either assume equal rates at each node, or compute the path heuristically and then allocate the rates optimally on the given path. In this paper we show that the above heuristics, albeit finding optimal solutions quite often, can lead to failing of paths at very low loads, and that this could be avoided by solving the problem, i.e. path computation and rate allocation, jointly at optimality. This is possible by modeling the problem as a mixed-integer second-order cone program and solving it optimally in split-second times for relatively large networks on commodity hardware; this approach can also be easily turned into a heuristic one, trading a negligible increase in blocking probability for one order of magnitude of computation time. Extensive simulations show that these methods are feasible in today's Internet service provider networks and they significantly outperform the existing schemes in terms of blocking probability. [ABSTRACT FROM AUTHOR]