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Modern devices often include several embedded instruments, such as BIST interfaces, sensors, calibration facilities. New standards, such as IEEE Std 1687, provide vehicles to access these instruments. In approaches based on reconfigurable scan networks (RSNs), instruments are coupled with scan registers, connected into chains and interleaved with reconfigurable modules. Such modules embed reconfigurable multiplexers that permit a selective access to different parts of the chain. A similar scenario is also supported by IEEE Std 1149.1-2013. The test of permanent faults affecting an RSN requires to shift test vectors throughout a certain number of network configurations. This paper presents some methodologies to select the list of configurations that perform the complete test of the reconfigurable modules of the RSN. In particular, one method is presented that, by construction, can be proved to be able to apply the test in the minimum amount of clock cycles. Other methods are sub-optimal in terms of test application time (TAT), but scale well on large circuits. In order to provide a comparison between the proposed methods, experimental results on some benchmark RSNs are provided. [ABSTRACT FROM AUTHOR]

Due to the long simulation time of the reference input set, computer architects often use reduced time simulation techniques to shorten the simulation time. However, what has not yet been thoroughly evaluated is the accuracy of these techniques relative to the reference input set and with respect to each other. To rectify this deficiency, this paper uses three methods to characterize reduced input set, truncated execution, and sampling-based simulation techniques while also examining their speed versus accuracy trade-off and configuration dependence. Our results show that the three sampling-based techniques, SimPoint, SMARTS, and random sampling, have the best accuracy, the best speed versus accuracy trade-off, and the least configuration dependence. On the other hand, the reduced input set and truncated execution simulation techniques had generally poor accuracy, were not significantly faster than the sampling-based techniques, and were severely configuration dependent. The final contribution of this paper is a decision tree, which can help architects choose the most appropriate technique for their simulations. [ABSTRACT FROM AUTHOR]

There is a growing interest in the use of wireless ad hoc sensor networks to monitor, detect, and track the movement of specified targets in a geographic region. A common concern in the deployment of such networks is whether or not a target can pass or intrude a sensor field without being detected. Recent papers in the literature have defined a measure called exposure to quantify the likelihood of a target passing through a sensor field without being detected. These papers differ in the definition of exposure. Also, the existing definitions of exposure are indicators of the likelihood of intrusion and not a direct measure of it. In this paper, we directly work with probability of detection instead of its indicators. We also probabilistically account for the presence of noise in the sensor readings. In the presence of noise, there is a trade off between the probability of a target passing through a sensor field without detection and the false alarm probability (i.e., the probability of falsely detecting the presence of target). We analytically characterize this trade off and illustrate the trade off for example deployments. We also introduce a variant of the traversal problem called unauthorized monitoring. This problem is of interest if sensor fields are used to secure an asset. We analytically characterize the probability of detecting unauthorized monitoring. We also show a trade off between this probability and the corresponding false alarm probability in the presence of noise. [ABSTRACT FROM AUTHOR]

A preface to articles about networks-on-chip is presented.

Maximum distance separable (MDS) matrices are widely used in the design of block ciphers. However, it is highly nontrival to find MDS matrices which could be used in practice. This paper focuses on the design of efficient MDS matrices for substitution-permutation networks (SPNs). We provide a new method to construct and count these MDS matrices. Moreover, we identified an interesting class of Cauchy matrices (named compact Cauchy matrices) which has the fewest different entries and is thus more favorable for implementation. Finally, we prove that all compact Cauchy matrices could be modified into an involution compact Cauchy matrix, and show how to maximize the occurrences of entry “1” in a compact Cauchy matrix. [ABSTRACT FROM AUTHOR]

Deadline guaranteed packet scheduling for switches is a fundamental issue for providing guaranteed QoS in digital networks. It is a historically difficult NP-hard problem if three or more deadlines are involved. All existing algorithms have too low throughput to be used in practice. A key reason is they use packet deadlines as default priorities to decide which packets to drop whenever conflicts occur. Although such a priority structure can ease the scheduling by focusing on one deadline at a time, it hurts the throughput greatly. Since deadlines do not necessarily represent the actual importance of packets, we can greatly improve the throughput if deadline induced priority is not enforced. This paper first presents an algorithm that guarantees the maximum throughput for the case where only two different deadlines are allowed. Then, an algorithm called iterative scheduling with no priority (ISNOP) is proposed for the general case where k > 2 different deadlines may occur. Not only does this algorithm have dramatically better average performance than all existing algorithms, but also guarantees approximation ratio of 2. ISNOP would provide a good practical solution for the historically difficult packet scheduling problem. [ABSTRACT FROM PUBLISHER]

At present, companies and standards organizations are enhancing Ethernet as the unified switch fabric for all of the TCP/IP traffic, the storage traffic and the high performance computing traffic in data centers. Backward congestion notification (BCN) is the basic mechanism for the end-to-end congestion management enhancement of Ethernet. To fulfill the special requirements of the unified switch fabric, i.e., losslessness and low transmission delay, BCN should hold the buffer occupancy around a target point tightly. Thus, the stability of the control loop and the buffer size are critical to BCN. Currently, the impacts of delay on the performance of BCN are unidentified. When the speed of Ethernet increases to 40 Gbps or 100 Gbps in the near future, the number of on-the-fly packets becomes the same order with the buffer size of switch. Accordingly, the impacts of delay will become significant. In this paper, we analyze BCN, paying special attention on the delay. We model the BCN system with a set of segmented delayed differential equations, and then deduce sufficient condition for the uniformly asymptotic stability of BCN. Subsequently, the bounds of buffer occupancy are estimated, which provides direct guidelines on setting buffer size. Finally, numerical analysis and experiments on the NetFPGA platform verify our theoretical analysis. [ABSTRACT FROM AUTHOR]

Context awareness, intended as providing the current execution environment at the service level, is a fundamental capability in future mobile systems. Unfortunately, the real-world realization of such scenarios is currently undermined by inefficient context data delivery mechanisms, which introduce excessive overhead over bandwidth-constrained wireless fixed infrastructures. To efficiently offload context access from fixed infrastructures to mobile nodes, this paper presents a new data caching algorithm that exploits peculiar aspects of context distribution, mainly limited data lifetime and interests similarity between nodes in physical proximity, to properly select the data to evict when necessary. Our solution considers a history over past data accesses and information over data replication to better exploit the limited available space. Extensive simulation results, collected in NS2 simulator, support our assumptions and demonstrate that our caching solution improves system scalability while adding a limited management overhead. [ABSTRACT FROM AUTHOR]

An interconnection network’s diagnosability is an important measure of its self-diagnostic capability. Based on the classical notion of diagnosability, strong diagnosability and conditional diagnosability were proposed later to better reflect the networks’ self-diagnostic capability under more realistic assumptions. In this paper, we study a class of interconnection networks called strong networks, which are n-regular, (n - 1)-connected, and with cn-number no more than n - 3. We build a relationship among the three diagnosability measures for strong networks. Under both PMC and MM^\ast models, given a strong network G with diagnosability t, we prove that G is strongly t-diagnosable if and only if G’s conditional diagnosability is greater than t. A simple check can show that almost all well-known regular interconnection networks are strong networks. The significance of this paper’s result is that it reveals an important relationship between strong and conditional diagnosabilities, and the proof of strong diagnosability for many interconnection networks under MM^\ast or PMC model is not necessary if their conditional diagnosability can be shown to be strictly larger than their diagnosability. [ABSTRACT FROM PUBLISHER]

A stochastic flow network is a directed graph with incoming edges (inputs) and outgoing edges (outputs), tokens enter through the input edges, travel stochastically in the network, and can exit the network through the output edges. Each node in the network is a splitter, namely, a token can enter a node through an incoming edge and exit on one of the output edges according to a predefined probability distribution. Stochastic flow networks can be easily implemented by beam splitters, or by DNA-based chemical reactions, with promising applications in optical computing, molecular computing and stochastic computing. In this paper, we address a fundamental synthesis question: Given a finite set of possible splitters and an arbitrary rational probability distribution, design a stochastic flow network, such that every token that enters the input edge will exit the outputs with the prescribed probability distribution. The problem of probability transformation dates back to von Neumann’s 1951 work and was followed, among others, by Knuth and Yao in 1976. Most existing works have been focusing on the “simulation” of target distributions. In this paper, we design optimal-sized stochastic flow networks for “synthesizing” target distributions. It shows that when each splitter has two outgoing edges and is unbiased, an arbitrary rational probability a \over b with a \leq b \leq 2^n can be realized by a stochastic flow network of size n that is optimal. Compared to the other stochastic systems, feedback (cycles in networks) strongly improves the expressibility of stochastic flow networks. [ABSTRACT FROM AUTHOR]

Server technology provides a means to support a wide range of online services and applications. However, their ad hoc configuration poses significant challenges to the performance, availability, and economical costs of applications. In this paper, we examine the impact of server configuration on the central trade-off between service performance and availability. First, we present a server model as a nonlinear continuous-time model using fluid approximations. Second, we develop concurrency control on server systems for an optimal configuration. We primarily provide two control laws for two different QoS objectives. AM-C is an availability-maximizing server control that achieves the highest service availability given a fixed performance constraint; and PM-C is a performance-maximizing control law that meets a desired availability target with the highest performance. We then improve the control with two additional multilevel laws. AA-PM-C is an availability-aware performance-maximizing control, and PA-AM-C is a performance-aware availability-maximizing control. In this paper, we present ConSer, a novel system for the control of servers. We evaluate ConSer's fluid model and control techniques on the TPC-C industry-standard benchmark. Our experiments show that the proposed techniques successfully guarantee performance and availability constraints. [ABSTRACT FROM AUTHOR]

Chip multiprocessors (CMPs) combine increasingly many general-purpose processor cores on a single chip. These cores run several tasks with unpredictable communication needs, resulting in uncertain and often-changing traffic patterns. This unpredictability leads network-on-chip (NoC) designers to plan for the worst case traffic patterns, and significantly overprovision link capacities. In this paper, we provide NoC designers with an alternative statistical approach. We first present the traffic-load distribution plots (T-Plots), illustrating how much capacity overprovisioning is needed to service 90, 99, or 100 percent of all traffic patterns. We prove that in the general case, plotting T-Plots is #P-complete, and therefore extremely complex. We then show how to determine the exact mean and variance of the traffic load on any edge, and use these to provide Gaussian-based models for the T-Plots, as well as guaranteed performance bounds. We also explain how to practically approximate T-Plots using random-walk-based methods. Finally, we use T-Plots to reduce the network power consumption by providing an efficient capacity allocation algorithm with predictable performance guarantees. [ABSTRACT FROM AUTHOR]

Efficient exact schedulability tests are required both for online admission of applications to dynamic systems and as an integral part of design tools for complex distributed real-time systems. This paper addresses performance issues with exact response time analysis (RTA) for fixed priority preemptive systems. Initial values are introduced that improve the efficiency of the standard RTA algorithm 1) when exact response times are required and 2) when only exact schedulability need be determined. This paper also explores modifications to the standard RTA algorithm, including the use of a response time upper bound to determine when exact analysis is needed, incremental computation aimed at faster convergence, and checking tasks in reverse priority order to identify unschedulable tasksets early. The various initial values and algorithm implementations are compared by means of experiments on a PC recording the number of iterations required and execution time measurements on a real-time embedded microprocessor. Recommendations are provided for engineers tasked with the problem of implementing exact schedulability tests as part of online acceptance tests and spare capacity allocation algorithms or as part of offline system design tools. [ABSTRACT FROM AUTHOR]

The Parallel Disks Model (PDM) has been proposed to alleviate the I/O bottleneck that arises in the processing of massive data sets. Sorting has been extensively studied on the PDM model due to the fundamental nature of the problem--several asymptotically optimal algorithms are known for sorting. Although randomization has been frequently exploited, most of the prior algorithms suffer from complications in memory layouts, implementation, restrictions in range of parameters, and laborious analysis. In this paper, we present a randomized mergesort algorithm based on a simple idea that sorts using an asymptotically optimal number of I/O operations with high probability and has all of the desirable features for practical implementation. In the second part of the paper, we also present several novel algorithms for sorting on the PDM that take only a small number of passes through the data. Recently, considerable interest has been shown by researchers in developing algorithms for problem sizes of practical interest and we are able to obtain several improvements and simplification, in particular for random input. [ABSTRACT FROM AUTHOR]

A fundamental problem in quality-of-service (QoS) routing is the multiconstrained path (MCP) problem, where one seeks a source-destination path satisfying K ≥ 2 additive QoS constraints in a network with K additive QoS parameters. The MOP problem is known to be NP-complete. One popular approach is to use the shortest path with respect to a single edge weighting function as an approximate solution to MCP. In a pioneering work, Jaffe showed that the shortest path with respect to a scaled 1-norm of the K edge weights is a 2-approximation to MCP in the sense that the sum of the larger of the path weight and its corresponding constraint is within a factor of 2 from minimum. In a recent paper, Xue et al. showed that the shortest path with respect to a scaled ∞-norm of the K edge weights is a K-approximation to MCP, in the sense that the largest ratio of the path weight over its corresponding constraint is within a factor of K from minimum. In this paper, we study the relationship between these two optimization criteria and present a class of provably good approximation algorithms to MCP. We first prove that a good approximation according to the second optimization criterion is also a good approximation according to the first optimization criterion, but not vice versa. We then present a class of very simple K-approximation algorithms according to the second optimization criterion, based on the computation of a shortest path with respect to a single edge weighting function. [ABSTRACT FROM AUTHOR]

A wireless sensor network consists of many low-cost, low-power sensor nodes, which can perform sensing, simple computation, and transmission of sensed information. Long distance transmission by sensor nodes is not energy efficient since energy consumption is a superlinear function of the transmission distance. One approach to prolonging network lifetime while preserving network connectivity is to deploy a small number of costly, but more powerful, relay nodes whose main task is communication with other sensor or relay nodes. In this paper, we assume that sensor nodes have communication range r > 0, while relay nodes have communication range R ≥ r, and we study two versions of relay node placement problems. In the first version, we want to deploy the minimum number of relay nodes so that, between each pair of sensor nodes, there is a connecting path consisting of relay and/or sensor nodes. In the second version, we want to deploy the minimum number of relay nodes so that, between each pair of sensor nodes, there is a connecting path consisting solely of relay nodes. We present a polynomial time 7-approximation algorithm for the first problem and a polynomial time (5 + ϵ)-approximation algorithm for the second problem, where ϵ > 0 can be any given constant. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a content distribution network designed to provide bounded content access latency. Content can be divided into multiple classes with different configurable per-class delay bounds. The network uses a simple distributed algorithm to dynamically select subsets of its proxy servers for different classes such that a global per-class delay bound is achieved on content access. The content distribution algorithm is implemented and tested on PlanetLab [25], a world-wide distributed Internet testbed. Evaluation results demonstrate that, despite Internet delay variability, subsecond delay bounds (of 200-500ms) can be guaranteed with a very high probability at only a moderate content replication cost. The distribution algorithm achieves a four to five-fold reduction in the number of response-time violations compared to prior content distribution approaches that attempt to minimize average latency. To the authors' knowledge, this paper presents the first wide-area performance evaluation of an algorithm designed to bound maximum content access latency, as opposed to optimizing an average performance metric. [ABSTRACT FROM AUTHOR]

Fairness is an important property of computer networks and systems. In a wide range of these systems such as distributed multi-hop wireless networks, multihomed networks, and cloud computing, each user may be allocated a number of system resources; this resembles a many-to-many relationship between the sets of users and resources, which raises the problem of system-wide fair resource allocation. In this paper, we assume that each user/node can be allocated a number of resources, which could be either in its neighborhood or far from it. As a key difference with previous works and through incorporating the concept of “flow”, we model near/far resources allocated to nodes. To attain fair flow control in such systems, first we model this situation by introducing a new multi-server system called multi-ring, in which a server that represents a resource, can serve only a subset of either neighboring or far nodes in the system. Then, we define a centralized optimization problem to attain weighted proportional fairness among all nodes meaning that the sum of allocated capacities from all servers to each node (while considering its flow) is fair. We evaluate fairness properties of multi-ring networks and provide conditions on system parameters under which a system can have a fair resource allocation. Moreover, we present a distributed method to attain fairness in distributed environments, and its stability/convergence is evaluated by non-linear discrete dynamical systems. We present conditions under which the system is stable, and through numerical analysis, we show how to obtain stable system parameters for large systems. The effectiveness of the presented method is studied through extensive numerical evaluation. Results show the success of our method in attaining fairness for various topologies and system parameters, and confirm our stability analysis. A number of systems with fairness issues are also studied as potential applications of our model. [ABSTRACT FROM AUTHOR]

Gaussian networks are degree four symmetric networks and these are designed based on the concept of Gaussian integers. The Gaussian network can be described in terms of a generator $\alpha =a+bi$ , where a$ and b$ are integers and . When $\gcd (a,b)=1$ , how to find edge disjoint Hamiltonian cycles has been shown before. In this paper for any generator $\alpha =a+bi,$ even when $\gcd (a, b)=d > 1$ , how to obtain two edge disjoint Hamiltonian cycles in these networks is described. [ABSTRACT FROM AUTHOR]

Cloud computing not only requires high-capacity data center networks to accelerate bandwidth-hungry computations, but also causes considerable power expenses to cloud providers. In recent years many advanced data center network architectures have been proposed to increase the network throughput, such as Fat-Tree [1] and BCube [2] , but little attention has been paid to the power efficiency of these network architectures. This paper makes the first comprehensive comparison study for typical data center networks with regard to their Network Power Effectiveness(NPE), which indicates the end-to-end bps per watt in data transmission and reflects the tradeoff between power consumption and network throughput. We take switches, server NICs and server CPU cores into account when evaluating the network power consumption. We measure NPE under both regular routing and power-aware routing, and investigate the impacts of topology size, traffic load, throughput threshold in power-aware routing, network power parameter as well as traffic pattern. The results show that in most cases Flattened Butterfly possesses the highest NPE among the architectures under study, and server-centric architectures usually have higher NPEs than Fat-Tree and VL2 architectures. In addition, the sleep-on-idle technique and power-aware routing can significantly improve the NPEs for all the data center architectures, especially when the traffic load is low. We believe that the results are useful for cloud providers, when they design/upgrade data center networks or employ network power management. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel analysis method for divisible load scheduling in mesh, torus and Gaussian network, a new type of interconnection network that has the same node degree as the mesh and torus, but shorter network diameter and shorter average hop distances under equal network size. The divisible scheduling in these three networks are uniformly formulated as the Maximum Finish Time Minimization (MFTM) problem. It involves minimizing the makespan of the load distribution and processing. The MTFM problem, a relaxed MFTM problem, a linear programming problem version and a heuristic algorithm are described and solved. The first three of these problems have identical solutions. The heuristic algorithm is close in performance to the optimal solution, significantly outperforms the previously described dimensional algorithm, and has much wider application range than the previously proposed phase algorithm. [ABSTRACT FROM PUBLISHER]

In RAID-5, data and parity blocks are distributed across all disks in a round-robin fashion. Previous approaches to RAID-5 scaling preserve such round-robin distribution, therefore requiring all the data to be migrated. In this paper, we rethink RAID-5 data layout and propose a new approach to RAID-5 scaling called MiPiL. First, MiPiL minimizes data migration while maintaining a uniform data distribution, not only for regular data but also for parity data. It moves the minimum number of data blocks from old disks to new disks for regaining a uniform data distribution. Second, MiPiL optimizes online data migration with piggyback parity updates and lazy metadata updates. Piggyback parity updates during data migration reduce the numbers of additional XOR computations and disk I/Os. Lazy metadata updates minimize the number of metadata writes without compromising data reliability. We implement MiPiL in Linux Kernel 2.6.32.9, and evaluate its performance by replaying three real-system traces. The results demonstrate that MiPiL consistently outperforms the existing “moving-everything” approach by 74.07-77.57% in redistribution time and by 25.78-70.50% in user response time. The experiments also illustrate that under the WebSearch2 and Financial1 workloads, the performance of the RAID-5 scaled using MiPiL is almost identical to that of the round-robin RAID-5. [ABSTRACT FROM AUTHOR]

Reliability evaluation of interconnection network is important to the design and maintenance of multiprocessor systems. The extra connectivity and the extra edge-connectivity are two important parameters for the reliability evaluation of interconnection networks. The \mbi n-dimensional bijective connection network (in brief, BC network) includes several well known network models, such as, hypercubes, Möbius cubes, crossed cubes, and twisted cubes. In this paper, we explore the extra connectivity and the extra edge-connectivity of BC networks, and discuss the structure of BC networks with many faults. We obtain a sharp lower bound of g-extra edge-connectivity of an \mbi n-dimensional BC network for n \geq 4 and 1 \leq g \leq 2^[n \over 2]. We also obtain a sharp lower bound of g-extra connectivity of an n-dimensional BC network for n \geq 4 and 1 \leq g \leq 2 n which improves the result in [“Reliability evaluation of BC networks,” IEEE Trans. Computers, DOI: 10.1109/tc.2012.106.] for 1 \leq g \leq n - 3. Furthermore, we give a remark about exploring the g-extra edge-connectivity of BC networks for the more general \mbi g, and we also characterize the structure of BC networks with many faulty nodes or links. As an application, we obtain several results on the \mbi g-extra (edge-) connectivity and the structure of faulty networks on hypercubes, Möbius cubes, crossed cubes, and twisted cubes. [ABSTRACT FROM AUTHOR]

In heterogeneous networks, devices communicate by means of multiple wired or wireless interfaces. By switching among interfaces or by combining the available ones, each device might establish several connections. A connection may be established when the devices at its endpoints share at least one active interface. In this paper, we consider two fundamental optimization problems. In the first one (Maximum Flow in Multi-Interface Networks, MFMI), we aim to establish the maximal bandwidth that can be guaranteed between two given nodes of the input network. In the second problem (Minimum-Cost Flow in Multi-Interface Networks, (MCFMI)), we look for activating the cheapest set of interfaces among a network to guarantee a minimum bandwidth $(B)$ of communication between two specified nodes. We show that MFMI is polynomially solvable while MCFMI is $(NP)$-hard even for a bounded number of different interfaces and bounded degree networks. Moreover, we provide polynomial approximation algorithms for MCFMI and exact algorithms for relevant subproblems. Finally, we experimentally analyze the proposed approximation algorithm, showing that in practical cases it guarantees a low approximation ratio. [ABSTRACT FROM PUBLISHER]

With the development of multiprocessor system on chips (MPSoCs), it is expected that hundreds of computing cores will be operating on a single chip in the near future. This will require high-performance on-chip networks with very low latency to provide a communication substrate for the increasing number of cores. In this paper, we consider Gaussian on-chip networks that are of significant topological advantages over traditional mesh and torus networks in terms of diameter and average hop distance. Many applications on MPSoCs need global data movement and global control to exchange data and synchronize the execution among cores, which require all-to-all broadcast communication. In this paper, we propose an all-to-all broadcast algorithm suitable for on-chip implementation on the Gaussian network topology. The algorithm utilizes controlled message flooding based on a broadcast pattern, which can be described in a formal, generic way for each node in terms of a few simple operations and can be easily built into router hardware. Furthermore, the generic broadcast pattern also ensures a balanced traffic load in all dimensions in the network so that minimum total latency for all-to-all broadcast can be achieved. The algorithm overlaps message switching time with transmission time in a pipelined fashion to further reduce the total communication latency of all-to-all broadcast. Comparison results demonstrate the topological merits of Gaussian networks and ultralow latency of the proposed all-to-all broadcast algorithm. [ABSTRACT FROM AUTHOR]

This paper introduces the concept of monitoring-as-a-service (MaaS), its main components, and a suite of key functional requirements of MaaS in cloud. We argue that MaaS should support not only the conventional state monitoring capabilities, such as instantaneous violation detection, periodical state monitoring, and single tenant monitoring, but also performance-enhanced functionalities that can optimize on monitoring cost, scalability, and the effectiveness of monitoring service consolidation and isolation. In this paper, we present three enhanced MaaS capabilities and show that window-based state monitoring is not only more resilient to noises and outliers, but also saves considerable communication cost. Similarly, violation-likelihood-based state monitoring can dynamically adjust monitoring intensity based on the likelihood of detecting important events, leading to significant gain in monitoring service consolidation. Finally, multitenancy support in state monitoring allows multiple cloud users to enjoy MaaS with improved performance and efficiency at more affordable cost. We perform extensive experiments in an emulated cloud environment with real-world system and network traces. The experimental results suggest that our MaaS framework achieves significant lower monitoring cost, higher scalability, and better multitenancy performance. [ABSTRACT FROM AUTHOR]

A complete family of Cayley graphs of degree four, denoted as L-networks, is considered in this paper. L-networks are 2D mesh-based topologies with wrap-around connections. L-networks constitute a graph-based model which englobe many previously proposed 2D interconnection networks. Some of them have been extensively used in the industry as the underlying topology for parallel and distributed computers of different scales. Tori, twisted and doubly twisted tori, toroidal diagonal meshes, chordal rings, and circulant graphs are, among others, members of the L-network family. Therefore, many results obtained in previous studies on these networks can be deduced from the general framework presented in this work. In addition, the network model presented in this work allows for new results on the domain of low-degree interconnection networks. Particularly, closed expressions for the graph distance properties have been derived and an optimal routing algorithm of constant complexity is provided. Since symmetry has a big impact on network performance, we have also identified which L-networks are symmetric by studying their group of automorphisms. Finally, a very simple model that predicts the performance of L-networks is also presented. Such model has been contrasted with empirical evaluation. [ABSTRACT FROM AUTHOR]

In this paper, we explore a new form of dissemination that arises in distributed, mission-critical applications called Flash Dissemination. This involves the rapid dissemination of rich information to a large number of recipients in a very short period of time. A key characteristic of Flash Dissemination is its unpredictability (e.g., natural hazards), but when invoked it must harness all possible resources to ensure timely delivery of information. Additionally, it must scale to a large number of recipients and perform efficiently in highly heterogeneous (data, network) and failure prone environments. We investigate a peer-based approach based on the simple principle of transferring dissemination load to information receivers using foundations from broadcast networks, gossip theory, and random networks. Gossip-based protocols are well known for being stateless, scalable, and fault-tolerant; however, their performance degrades as content size increases, because of the propagation of redundant gossip messages. In this paper, we propose Concurrent Random Expanding Walkers (CREW), a smart gossip protocol designed to maximize the speed of dissemination by transmitting data only as needed, and by exploiting both intra- and internode concurrency. CREW is designed to support both content and network heterogeneity and deal with transmission failures without sacrificing dissemination speed. We implemented CREW on top of a scalable middleware environment that allows for deployment across several platforms and developed optimizations without compromising on the stateless nature of CREW. We evaluated CREW empirically and compared it to optimized implementations of popular gossip and peer-based systems. Our experiments show that CREW significantly outperforms both traditional gossip and current large content dissemination systems while sustaining its performance in the presence of network errors. [ABSTRACT FROM AUTHOR]

As Internet and information technology have continued developing, the necessity for fast packet processing in computer networks has also grown in importance. All emerging network applications require deep packet classification as well as security-related processing and they should be run at line rates. Hence, network speed and the complexity of network applications will continue increasing and future network processors should simultaneously meet two requirements: high performance and high programmability. We will show that the performance of single processors will not be sufficient to support future demands. Instead, we will have to turn to multicore processors, which can exploit the parallelism in network workloads. In this paper, we focus on the cache coherence protocols which are central to the design of multicore-based network processors. We investigate the effects of two main categories of various cache coherence protocols with several network workloads on multicore processors. Our simulation results show that token protocols have a significantly higher performance than directory protocols. With an 8-core configuration, token protocols improves the performance compared to directory protocols by a factor of nearly 4 on average. [ABSTRACT FROM AUTHOR]

The ability of networked system software to adapt in a controlled manner to changes in the environment and requirements is crucial, but difficult to realize in complex systems with multiple interacting software layers/components. Typically, many components in a networked system implement adaptive behaviors and encapsulate their own adaptation logic (policies), making the whole system's adaptive behavior hard to analyze, coordinate, and test. This paper describes Cholla, a software architecture that separates the policy decisions of how and when adaptive components in networked systems react to their environment into separate centralized controllers that are constructed from composable rule sets. Centralizing policy decisions into controllers in Cholla facilitates the analysis, coordination, and testing of these policies, while the composable nature of these controllers allows them to be customized to changing user, application, and hardware demands. In addition to describing the architecture of Cholla, this paper also presents a Linux-based prototype implementation of this architecture that controls and coordinates adaptation policy decisions inside network protocols and multimedia applications. An experimental evaluation of this prototype demonstrates that Cholla's controller architecture enables component-based construction and customization of adaptation policies in networked systems, and that these policies can effectively control and coordinate adaptation. [ABSTRACT FROM AUTHOR]

Packet classification has continued to be an important research topic for high-speed routers in recent years. In this paper, we propose a new packet classification scheme based on the binary range and prefix searches. The basic data structure of the proposed packet classification scheme for multidimensional rule tables is a hierarchical list of sorted ranges and prefixes that allows the binary search to be performed on the list at each level to find the best matched rule. We also propose a set of heuristics to further improve the performance of the proposed algorithm. We test our schemes by using rule tables of various sizes generated by ClassBench and compare them with the existing schemes, EGT, EGT-PC, and HyperCuts. The performance results show that in a test using a 2D segmentation table, the proposed scheme not only performs better than the EGT, EGT-PC, and HyperCuts in classification speed and memory usage but also achieves faster table update operations that are not supported in the existing schemes. [ABSTRACT FROM AUTHOR]

This paper presents how a multicore system can benefit from the use of a latency-aware memory bus capable of dual-concurrent data transfers on a single wire line: Source synchronous CDMA interconnect (SSCDMA-I) has been adopted to implement the memory bus of a shared-memory multicore system. Two types of bus-based homogeneous and heterogeneous multicore systems are modeled and simulated by a cycle-accurate simulation platform. Unlike the conventional time-division multiplexing (TDM) bus-based multicore system that shows degradation in performance as the number of processing cores increases, the proposed SSCDMA bus-based multicore shows higher performance up to 23.1 percent for four cores. The maximum latency of a heterogeneous multicore system with a mix of traffic loads has been reduced up to 78 percent. These results demonstrate that the performance of multicore systems can be improved with less cost and network complexity by reducing the bus contention interferences and by supporting higher concurrency in memory accesses that brings shorter critical word access latency. [ABSTRACT FROM AUTHOR]

A system is t-diagnosable if all faulty nodes can be identified without replacement when the number of faults does not exceed t, where t is some positive integer. Furthermore, a system is strongly t-diagnosable if it is t-diagnosable and can achieve (t + 1)-diagnosability except for the case where a node's neighbors are all faulty. In this paper, we propose some conditions for verifying whether a class of interconnection networks, called Matching Composition Networks (MCNs), are strongly diagnosable under the comparison diagnosis model. [ABSTRACT FROM AUTHOR]

Recently, high-end reconfigurable computing systems that employ Field-Programmable Gate Arrays (FPGAs) as hardware accelerators for general-purpose processors have been built. These systems provide new opportunities for high-performance computing. However, the coexistence of the processors and the FPGAs in them also poses new challenges to application developers. In this paper, we build a design model for hybrid designs, that is, designs that utilize both the processors and the FPGAs for computations. The model characterizes a reconfigurable computing system using various parameters, including the floating-point computing power of the processors and the FPGAs, the number of nodes, the size of multiple levels of memory, the memory bandwidth, and the network bandwidth. Based on the model, we propose a design methodology for hardware/software codesign. The methodology partitions workload between the processors and the FPGAs, maintains load balance in the system, and realizes scalability over multiple nodes. Designs are proposed for several computationally intensive applications: matrix multiplication, matrix factorization, and the Floyd-Warshall algorithm for the all-pairs shortest-paths problem. To illustrate our ideas, the proposed hybrid designs are implemented on a Cray XD1. Each node of XD1 contains AMD 2.2-GHz Opteron processors and a Xilinx Virtex-II Pro FPGA. Experimental results show that our designs utilize both the processors and the FPGAs efficiently and overlap most of the data transfer overheads and network communication costs with the computations. Our designs achieve up to 90 percent of the total performance of the nodes and 90 percent of the performance predicted by the design model. In addition, our designs scale over a large number of nodes. [ABSTRACT FROM AUTHOR]

Caches are underutilized because not all of the excess data brought into the cache, to exploit spatial locality, is used. We define cache utilization as the percentage of data brought into the cache that is actually used. In this paper, we focus on prediction mechanisms to predict the useless data in a cache block (cache noise). The prediction mechanisms consider the word usage history of cache blocks for predicting the useful data so that only the useful data is fetched into the cache on a cache miss. We found that the cache noise can have a predictability of about 95 percent with a simple last word usage predictor. When applying cache noise prediction to the L1 data cache, we observed about 37 percent improvement in cache utilization and about 23 percent and 28 percent reduction in cache energy consumption and bandwidth requirement, respectively. Cache noise mispredictions increased the miss rate by 0.1 percent and had almost no impact on instructions per cycle (IPC) count. When compared to a subblocked cache, fetching the to-be-referenced data resulted in 97 percent and 10 percent improvement in miss rate and cache utilization, respectively. However, the subblocked cache had a bandwidth requirement of about 35 percent of the cache noise prediction-based approach and saved 10 percent more power. We also observed that cache noise prediction significantly improves the utilization and reduces the bandwidth requirement for prefetching. [ABSTRACT FROM AUTHOR]

Efficient and deadlock-free routing is critical to the performance of networks-on-chip. The effectiveness of any adaptive routing algorithm strongly depends on the underlying selection strategy. When the routing function returns a set of admissible output channels with a cardinality greater than one, a selection function is used to select the output channel to which the packet will be forwarded. In this paper, we present a novel selection strategy that can be coupled with any adaptive routing algorithm. The proposed selection strategy is based on the concept of Neighbors-on-Path, the aim of which is to exploit the situations of indecision occurring when the routing function returns several admissible output channels. The overall objective is to choose the channel that will allow the packet to be routed to its destination along a path that is as free as possible of congested nodes. Performance evaluation is carried out by using a flit-accurate simulator under traffic scenarios generated by both synthetic and real applications. Results obtained show how the proposed selection strategy applied to the Odd-Even routing algorithm yields an improvement in both average delay and saturation point up to 20 percent and 30 percent on average, respectively, with minimal overhead in terms of area occupation. In addition, as a consequence of the improved router efficiency, a positive effect on total energy consumption is also observed under near-congestion packet injection rates. [ABSTRACT FROM AUTHOR]

Designing protocols for solving the consensus problem faces new challenges in mobile computing environments. Among others, how we can achieve message efficiency for saving resource consumption has been the focus of research. In this paper, we present the HC protocol, a message efficient consensus protocol for MANETs. We consider the widely used system model where the hosts fail by crashes and the system is equipped with Chandra-Toueg's unreliable failure detectors. Unlike existing consensus protocols, the HC protocol uses a two-layer hierarchy based on clusters to achieve message efficiency. The messages from and to the hosts in the same cluster are merged so as to reduce the message cost. However, adding such a hierarchy is not trivial. Due to host movements and failures, the hierarchy changes from time to time and this may cause message loss. In designing HC, we also propose methods to handle such message losses. Extensive simulations have been carried out to evaluate and compare the performance of the HC protocol and similar protocols in a MANET environment. Simulation results show that, in most cases, our protocol can significantly reduce both the message cost and time cost. With increases in the system scale or the percentage of faulty hosts, the advantage of our protocol becomes more obvious. [ABSTRACT FROM AUTHOR]

This paper proposes an architecture and a synthesis method for high-speed computation of fixed-point numerical functions such as trigonometric, logarithmic, sigmoidal, square root, and combinations of these functions. Our architecture is based on the lookup table (LUTE) cascade, which results in a significant reduction in circuit complexity compared to traditional approaches. This is suitable for automatic synthesis and we show a synthesis method that converts a Matlab-like specification into an LUTE cascade design. Experimental results show the efficiency of our approach as implemented on a field-programmable gate array (FPC). [ABSTRACT FROM AUTHOR]

In this paper, we develop a segment tree data structure for solving dynamic table lookup problems. The proposed dynamic segment tree (DST) uses all of the distinct end points of ranges as the keys based on a new range end point scheme. The new end point scheme generates fewer end points than the traditional end point scheme. DST is implemented as a balanced binary search tree augmented with a range set in each mode. The performance of accessing and updating the ranges stored in each node is improved by an efficient range set data structure that combines the priority queue and the interval tree. Based on the proposed data structures, the time complexities of search, insertion, and deletion in a set of N arbitrary ranges are O(logN), O(logN × log Max), and O(Max × logN × log Max), respectively, where Max is the maximum number of ranges covering any address. In practical routing tables, Max is a small constant (six for the routing tables we tested). The memory requirement for DST is O(N log N). The experimental results using real Internet Protocol version 4 (lPv4) routing tables show that both the OST and prefix binary tree on binary tree (PBOB) by Lu et al. (2004) perform much better than the multiway range tree (MRT) by Warkhede et al. (2004) and prefix in B-tree (PIBT) by Lu et al. (2005) in terms of update speed and memory consumption, but DST performs much better than PBOB and a little slower than MRT and PIBT in terms of search speed. [ABSTRACT FROM AUTHOR]

Abstract-(t, k)-diagnosis, which is a generalization of sequential diagnosis, requires at least k faulty processors identified and repaired in each iteration provided there are at most faulty processors, where t ≥ k. In this paper, a (t, k)-diagnosis algorithm under the MM* model is proposed for matching composition networks, which include many well-known interconnection networks, such as hypercubes, crossed cubes, twisted cubes, and Möbius cubes. It is shown that a matching composition network of n dimensions is (Ω(2n*log n / n), n)-diagnosable. [ABSTRACT FROM AUTHOR]

In this paper, we present a self-stabilizing algorithm for finding clustering of tree networks on a distributed model of computation. Clustering is defined as the covering of the nodes of a network by subtrees such that the intersection of any two subtrees is at most a single node and the difference between the sizes of the largest and the smallest clusters is minimal. The proposed algorithm evenly partitions the network into nearly the same size clusters and places resources and services for each cluster at its clusterhead to minimize the cost of sharing resources and using the services. Due to being self-stabilizing, the algorithm can withstand transient faults and does not require initialization. The paper includes a correctness proof of the algorithm, It concludes with remarks on issues such as open and related problems and the application areas of the algorithm. [ABSTRACT FROM AUTHOR]

(t, k)-diagnosis, which is a generalization of sequential diagnosis, requires at least k faulty processors identified and replaced in each iteration provided there are at most t faulty processors, where t ≥ k. This paper proposes a (t, k)-diagnosis algorithm for matching composition networks, which include many well-known interconnection networks such as hypercubes, crossed cubes, twisted cubes, and Möbius cubes. It is shown that matching composition networks of n dimensions are (Ω(...), n), diagnosable, where n > 5. [ABSTRACT FROM AUTHOR]

This paper presents event stream-based online algorithms that fuse the data reported from processes to detect causality-based predicates of interest. The proposed algorithms have the following features. 1) The algorithms are based on logical time, which is useful to detect "cause and effect" relationships in an execution. 2) The algorithms detect properties that can be specified using predicates under a rich palette of time modalities. Specifically, for a conjunctive predicate ø, the algorithms can detect the exact fine-grained time modalities between each pair of intervals, one interval at each process, with low space, time, and message complexities. The main idea used to design the algorithms is that any "cause and effect" interaction can be decomposed as a collection of interactions between pairs of system components. The detection algorithms, which leverage the pairwise interaction among the processes, incur a low overhead and are, hence, highly scalable. The paper then shows how the algorithms can deal with mobility in mobile ad hoc networks. [ABSTRACT FROM AUTHOR]

Fair sharing of bandwidth remains an unresolved issue for distributed systems. In this paper, the users of a distributed LAN are modeled as selfish users with independence to choose their individual strategies. With these selfish users, the contention-based distributed medium access scenario is modeled as a complete-information, noncooperative game, designated the "Access Game." A novel MAC strategy based on p-persistent CSMA is presented to achieve fairness in the "Access Game." It is proven that there are an infinite number of Nash Equilibria for the "Access Game," but they do not result in fairness. Therefore, it may be beneficial for the selfish users to adhere to a set of constraints that result in fairness in a noncooperative fashion. This leads to the formulation of a constrained "Access. Game" with fairness represented as a set of algebraic constraints. It is proven that the solution of the constrained game, the Constrained Nash Equilibrium, is unique. Further, it is shown that, in addition to achieving fairness, this solution also optimizes the throughput. Finally, these results are extended to a more realistic incomplete-information scenario by approximating the incomplete-information scenario as a complete-information scenario through information gathering and dissemination. [ABSTRACT FROM AUTHOR]

A Multiple Bus Network (MBN) connects a set of processors via a set of buses. Two important parameters of an MBN are its loading (largest number of connections on a bus) and its degree (largest number of connections to a processor). These parameters determine the cost, speed, and implementability of the MBN. The smallest degree that any useful MBN can have is 2. In this paper, we study the relationship between running time, degree, and loading of degree-2 MBNs running a fundamental class of algorithms called binary tree algorithms. (A binary tree algorithm reduces 2n inputs at the leaves of a balanced binary tree to a single result at the root of the tree.) Specifically, we establish a nontrivial Ω(n/log n) loading lower bound for any degree-2 MBN running a 2n input binary tree algorithm optimally in n steps. We show that this bound does not hold if the restriction on the degree or the running time is relaxed. That is, optimal-time, degree-3, constant loading MBNs and suboptimal-time, degree-2, constant loading MBNs exist for binary tree algorithms. We also derive a lower bound on the additional time (beyond the optimal) needed to run binary tree algorithms on a degree-2, loading-L MBN, for any L⩾ 3. [ABSTRACT FROM AUTHOR]

As multicast applications have become widely deployed on the Internet, it is increasingly important to ensure these applications respond to network congestion in a TCP-friendly manner so as to coexist with TCP connections (which constitute the majority of the Intemet traffic). In this paper, we present a Rate-based Congestion Control scheme for Multicast, called RACCOOM, for applications that deploy source-based multicast trees as the communication paradigm. Inthe absence of packet loss, a RACCOOM session keeps track of the congestion status of the on-tree path with the largest round trip time (called the target path) and adjusts its sending rate using a TCP Vegas [3]-like method. Upon detection of packet loss anywhere in the muiticast tree, RACCOOM then responds by reducing its sending rate by half in a TCP-Renomanner. The ACK aggregation method used in RACCOOMpreventsACK implosion and yet provides the sender with a simple but comprehensive view of congestion conditions in the multicast tree. Finally, RACCOOM is equipped with mechanisms to deal with changes of the target path due to traffic change and member join/leave. To achieve TCP-friendliness, we have devised a simple method in RACCOOMto emulate how a TCP connection would behave under the same packet loss and delay characteristics. The results thus derived are used by RACCOOMto online adjust the parameters Of its rate adjustment method. Alternatively, we can achieve (weighted) fairness (in terms of bandwidth sharing) among competing RACCOOM connections based on results obtained from feedback control theory. We validate the design, and demonstrate the features, of RACCOOM in ns-2. The encouraging simulation results, coupled with the fact that all the RACCOOM operations except acknowledgment aggregation (which requires modest router support] can be performed at end hosts, suggest that RACCOOM is a practical and yet effective congestion control solution for multicast applications. [ABSTRACT FROM AUTHOR]

Clusters of workstations (COWs) are becoming increasingly popular as a cost-effective alternative to parallel computers. In these systems, processors are connected using irregular topologies, providing the wiring flexibility, scalability, and incremental expansion capability required in this environment. Myrinet is one of the most popular interconnection networks for COWs. Myrinet uses source routing and wormhole switching. The up[sup *]/down[sup *] routing algorithm is used to build the network routes. On the other hand, in Myrinet, network behavior is controlled by the software running at the network interfaces. Hence, new features such as new routing algorithms can be added by only changing this software. In previous work, we proposed the In-Transit Buffer (ITB) mechanism to improve the performance of source routing-based networks. The ITB mechanism temporarily ejects packets from the network at some intermediate hosts and later reinjects them into the network, performing a special kind of virtual cut-through switching at these hosts. We applied this mechanism to up[sup *]/down[sup *] routing, in order to remove the down → up forbidden channel dependences that prevented minimal routing between every pair of hosts. Results showed that network throughput can be more than doubled on medium-sized (32 switches) networks. In this paper, we analyze in depth the effect of using ITBs in the network, showing that they not only serve for guaranteeing minimal routing, but also that they are a powerful mechanism able to balance network traffic and reduce network contention. To demonstrate these capabilities, we apply the ITB mechanism to improved routing schemes, such as DFS and smart- routing. These routing algorithms (without ITBs) are able to improve the performance of up[sup *]/down[sup *] by 30 percent and 90 percent, respectively, for a 32-switch network. The evaluation results show that, when ITBs are used together with these improved routing algorithms, network throughput achieved by DFS and smart-routing can still be improved by 56 percent and 23 percent, respectively. However, smart-routing requires a time to compute the routing tables that rapidly grows with network size, it being impossible in practice to build networks with more than 32 switches. This high computational cost is mainly motivated by the need of obtaining deadlock-free routing tables. However, when ITBs are used, one can decouple the stages of computing routing tables and breaking cycles. Moreover, as stated above, ITBs can be used to reduce network contention. In this way, in this paper, we also propose a completely new routing algorithm that tries to balance network traffic by using a simple and low time consuming strategy. The proposed algorithm guarantees deadlock freedom and reduces network contention with the use of ITBs. The evaluation results show that our algorithm obtains unprecedented throughputs in 32-switch networks, tripling the original up[sup *]/down[sup *] and almost doubling smart-routing. [ABSTRACT FROM AUTHOR]

This paper describes a new protocol for the establishment of multihop ad hoc networks based on Bluetooth devices. The protocol proceeds in three phases: device discovery, partitioning of the network into Bluetooth piconets, and interconnection of the piconets into a connected scatternet. The protocol has the following desirable properties: It is executed at each node with no prior knowledge of the network topology, thus being fully distributed. The selection of the Bluetooth masters is driven by the suitability of a node to be the "best fit" for serving as a master. The generated scatternet is a connected mesh with multiple paths between any pair of nodes, thus achieving robustness. Differently from existing solutions, no extra hardware is required to run the protocol at each node and there is no need for a designated node to start the scatternet formation process. Simulation results are provided which evaluate the impact of the Bluetooth device discovery phase on the performance of the protocol. [ABSTRACT FROM AUTHOR]

In asynchronous systems, the sender encodes a data word with a code word from an unordered code and transmits the code word on the parallel bus lines. In this paper, a transmission time analysis for the above parallel asynchronous communication scheme is presented. It is proven that the average transmission time for a code word is a strictly increasing function of the weight of the code word and it approaches the worst transmission time possible when the weight goes to infinity. This implies that fast parallel asynchronous systems can be designed using low weight codes. This paper also analyzes the transmission time performances of the proximity detecting codes and gives some efficient low constant weight code designs. [ABSTRACT FROM AUTHOR]

In network on chips (NoCs) design, reconfiguration of NoC is a very effective option for minimizing power consumption, and Gaussian networks can provide significant advantage over the mesh networks in terms of network diameter, average hop distance and so on. In this paper, based on the special topology structure and the static connection rules within Gaussian networks, we present the reconfiguration representation for Gaussian networks and the nature of reconfigurable Gaussian networks. Furthermore, reconfigurable rules of Gaussian networks are proposed to design the constraints for automatic reconfiguration of NoC. [ABSTRACT FROM PUBLISHER]