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Parallel and Distributed Systems, IEEE Transactions on

Issue 4 • Date April 2008

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Displaying Results 1 - 18 of 18
  • [Front cover]

    Page(s): c1
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  • [Inside front cover]

    Page(s): c2
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  • Coordinated Services Provision in Peer-to-Peer Environments

    Page(s): 433 - 446
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3070 KB) |  | HTML iconHTML  

    In recent years, inspired by the emerging Web services standard and peer-to-peer technology, a new federated service providing (FSP) system paradigm has attracted increasing research interests. Many existing systems have either explicitly or implicitly followed this paradigm. Instead of exchanging files, peers in FSP systems share their computation resources in order to offer domain-specific services. In this paper, we focused on the coordination problem of how to self-organize the service group structures in response to the varying service demand. We presented our solution in the form of a coordination mechanism, which includes a labor-market model, a recruiting protocol, and a policy-driven decision architecture. Peers make their service providing decisions based on their local policies, which can be added, removed, or modified by users. A general methodology is introduced in this paper to facilitate policy design. Specifically, a heuristic inspired by the extremal optimization technique is utilized to handle potential inconsistencies among policies. A stimulus-response mechanism was further applied to make the decision process adjustable. Experiments under five application scenarios verified our ideas and demonstrated the effectiveness of our coordination mechanism. View full abstract»

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  • Scalable Distribution of XML Content with XNet

    Page(s): 447 - 461
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3006 KB) |  | HTML iconHTML  

    The XNET XML content network was designed to implement efficient and reliable distribution of structured XML content to very large populations of consumers. For that purpose, our system integrates several technologies: the routing protocol XROUTE makes extensive use of subscription aggregation to limit the size of routing tables while ensuring perfect routing (that is, an event is forwarded to a link only if it leads to an interested consumer). The filtering engine XTRIE uses a sophisticated algorithm to match incoming XML documents against large populations of tree-structured subscriptions, whereas the XSEARCH subscription management algorithm enables the system to efficiently manage large and highly dynamic consumer populations. Finally, our XNET system integrates reliability mechanisms to guarantee that its state is consistent with the consumer population and implements several approaches to fault tolerance to recover from various types of router and link failures. We have analyzed the efficiency of our techniques with various simulations, and to assess the performance of our system in realistic settings and show that it is perfectly suitable for large-scale distributed environments, we have performed a large-scale experimental deployment on the PlanetLab testbed. View full abstract»

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  • Max-Min Fair Scheduling in Input-Queued Switches

    Page(s): 462 - 475
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2785 KB) |  | HTML iconHTML  

    Fairness in traffic management can improve the isolation between traffic streams, offer a more predictable performance, eliminate transient bottlenecks, mitigate the effect of certain kinds of denial-of-service attacks, and serve as a critical component of a quality-of-service strategy to achieve certain guaranteed services such as delay bounds and minimum bandwidths. In this paper, we choose a popular notion of fairness called max-min fairness and provide a rigorous definition in the context of input-queued switches. We show that being fair at the output ports alone or at the input ports alone or even at both input and output ports does not actually achieve an overall max-min fair allocation of bandwidth in a switch. Instead, we propose a new algorithm that can be readily implemented in a distributed fashion at the input and output ports to determine the exact max-min fair rate allocations for the flows through the switch. In addition to proving the correctness of the algorithm, we propose a practical scheduling strategy based on our algorithm. We present simulation results, using both real traffic traces and synthetic traffic, to evaluate the fairness of a variety of popular scheduling algorithms for input-queued switches. The results show that our scheduling strategy achieves better fairness than other known algorithms for input-queued switches and, in addition, achieves throughput performance very close to that of the best schedulers. View full abstract»

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  • Optimal State Allocation for Multicast Communications With Explicit Multicast Forwarding

    Page(s): 476 - 488
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2745 KB) |  | HTML iconHTML  

    In this paper, we propose a scalable and adaptive multicast forwarding mechanism based on explicit multicast (Xcast). This mechanism optimizes the allocation of forwarding states in routers and can be used to improve the scalability of traditional IP multicast and source-specific multicast. Compared with previous work, our mechanism needs fewer routers in a multicast tree to store forwarding states and therefore leads to a more balanced distribution of forwarding states among routers. We focus on two problems and formulate each of them as an optimization problem. The first problem, referred to as minstate, minimizes the total number of routers that store forwarding states in a multicast tree. The second problem, referred to as balancestate, minimizes the maximum number of forwarding states stored in a router for all multicast groups, which is proved to be an NP-hard problem. We design a distributed algorithm that obtains the optimal solution to the first problem and propose an approximation algorithm for the second problem. We also prove that the approach adopted by most existing works to allocate forwarding states in the branching routers of a multicast tree is a special case of our mechanism. The simulation results show that the forwarding state allocation provided by previous work is concentrated on the backbone routers in the Internet, which may cause the scalability problem. In contrast, our mechanism can balance forwarding states stored among routers and reduce the number of routers that store the forwarding states for a multicast tree. View full abstract»

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  • On-Demand Medium Access in Multihop Wireless Networks with Multiple Beam Smart Antennas

    Page(s): 489 - 502
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4009 KB) |  | HTML iconHTML  

    The paper presents a detailed discussion of various issues involved in designing a medium access control (MAC) protocol for multihop wireless networks with nodes employing multiple beam smart antennas. Multiple beam smart antennas can form several beams simultaneously and can initiate concurrent transmissions or receptions .in them, thereby increasing the throughput of the bottleneck nodes. Traditional on-demand MAC protocols for omnidirectional and single beam directional antennas based on the IEEE 802.11 distributed coordination function (DCF) mechanism cannot take advantage of this unique capability of multiple beam antennas as they do not facilitate concurrent transmissions or receptions by a node. This paper introduces a novel protocol, hybrid MAC (HMAC), which enables concurrent packet reception (CPR) and concurrent packet transmission (CPT) at a node equipped with multiple beam antennas and is backward compatible with IEEE 802.11 DCF. Simulation results show the superior performance of HMAC in most ad hoc scenarios. Moreover, in some sample topologies, the throughput of HMAC is close to the theoretical maximum. The paper also presents a wireless mesh network architecture with heterogeneous antenna technologies and illustrates the advantages of employing multiple beam smart antennas and HMAC in such networks. View full abstract»

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  • A Dynamic Skip List-Based Overlay for On-Demand Media Streaming with VCR Interactions

    Page(s): 503 - 514
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    Media distribution through application-layer overlay networks has received considerable attention recently, owing to its flexibility and readily deployable nature. On-demand streaming with asynchronous requests and, in general, with VCR-like interactions nevertheless remains a challenging task in overlay networks. In this paper, we introduce the dynamic skip list (DSL), a novel randomized and distributed structure that inherently accommodates dynamic and asynchronous clients. We establish the theoretical foundations of the DSL and demonstrate a practical DSL-based streaming overlay. In this overlay, the costs for typical operations, including join, leave, fast-forward, rewind, and random seek, are all sublinear to the client population. The model also seamlessly integrates a smart data scheduling algorithm using linear network coding, yielding fast and robust downloading from multiple suppliers. Our simulation results show that the DSL-based overlay is highly scalable. It delivers reasonably smooth playback with diverse client interactivities while keeping the computation and bandwidth overheads low. View full abstract»

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  • peerTalk: A Peer-to-Peer Multiparty Voice-over-IP System

    Page(s): 515 - 528
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2130 KB) |  | HTML iconHTML  

    Multiparty voice-over-IP (MVolP) services allow a group of people to freely communicate with each other via the Internet, which have many important applications such as online gaming and teleconferencing. In this paper, we present a peer-to-peer MVolP system called peerTalk. Compared to traditional approaches such as server-based mixing, peerTalk achieves better scalability and failure resilience by dynamically distributing the stream processing workload among different peers. Particularly, peerTalk decouples the MVolP service delivery into two phases: mixing phase and distribution phase. The decoupled model allows us to explore the asymmetric property of MVolP services (for example, distinct speaking/listening activities and unequal inbound/outbound bandwidths) so that the system can better adapt to distinct stream mixing and distribution requirements. To overcome arbitrary peer departures/ failures, peerTalk provides lightweight backup schemes to achieve fast failure recovery. We have implemented a prototype of the peerTalk system and evaluated its performance using both a large-scale simulation testbed and a real Internet environment. Our initial implementation demonstrates the feasibility of our approach and shows promising results: peerTalk can outperform existing approaches such as P2P overlay multicast and coupled distributed processing for providing MVolP services. View full abstract»

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  • Operand-Load-Based Split Pipeline Architecture for High Clock Rate and Commensurable IPC

    Page(s): 529 - 544
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    The increase in the complexity of a wide-issue processor with its pipeline width is one of the primary concerns of processor designers. In the conventional design, the hardware in the processor core is laid out to handle multiple instructions with two source operands in each pipeline stage. However, an analysis of SPEC2000 programs reveals that an integer program on the average constitutes 25.2 percent of two-op (both source registers) integer instructions and 72.5 percent of one-op/zero-op integer instructions. Floating-point (FP) programs are found to constitute on the average 15.8 percent of two-op integer instructions and 44.1 percent of one-op/zero-op integer instructions. The analysis observes that the hardware laid out for worst-case requirements in the integer pipeline is highly underutilized for a significant portion of time. To alleviate the complexity issues, we propose the split pipeline architecture, a novel technique to distinguish and process instructions based on their source operand requirements. The conventional pipeline is split into two after the decode stage, and the two pipelines are again converged at the execution stage. This leads to a capability of processing instructions at a higher clock rate and at almost the same instruction-per-cycle (IPC) throughput, as compared to a conventional processor. Various flavors of the proposed architecture are simulated and analyzed in this paper, with a circuit level analysis to determine the impact on the critical path delays. Results show that a processor that can fetch, decode, and commit eight instructions in each cycle and with split pipelines of two two-source integer instruction and six zero/one-source integer instruction can achieve a clock rate that is 15.8 percent faster than an eight-wide conventional processor while reducing the IPC throughput by only 0.7 percent for SPEC2000 benchmarks. Similarly, a four-wide processor with split pipelines of one two-source integer instruction and three zero/- - one-source integer instructions can achieve a clock rate that is 19.69 percent faster than a four-wide conventional processor while reducing the IPC throughput by only 1.9 percent. View full abstract»

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  • Algorithms for Fault-Tolerant Topology in Heterogeneous Wireless Sensor Networks

    Page(s): 545 - 558
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    This paper addresses fault-tolerant topology control in a heterogeneous wireless sensor network consisting of several resource-rich supernodes, used for data relaying, and a large number of energy-constrained wireless sensor nodes. We introduce the k-degree anycast topology control (fc-ATC) problem, with the objective of selecting each sensor's transmission range such that each sensor is k-vertex supernode connected and the total power consumed by sensors is minimized. Such topologies are needed for applications that support sensor data reporting, even in the event of failures of up to k - 1 sensor nodes. We propose three solutions for the k-ATC problem: a k-approximation algorithm, a greedy centralized algorithm that minimizes the maximum transmission range between all sensors, and a distributed and localized algorithm that incrementally adjusts sensors' transmission range such that the k-vertex supernode connectivity requirement is met. Extended simulation results are presented to verify our approaches. View full abstract»

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  • Towards Spatial Window Queries Over Continuous Phenomena in Sensor Networks

    Page(s): 559 - 571
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1886 KB) |  | HTML iconHTML  

    Recent research on sensor networks has focused on the efficient processing of declarative SQL queries over sensor nodes. Users are often interested in querying an underlying continuous phenomenon such as a toxic plume, whereas only discrete readings of sensor nodes are available. Therefore, additional information estimation methods are necessary to process the sensor readings to generate the required query results. Most estimation methods are computationally intensive, even when computed in a traditional centralized setting. Furthermore, energy and communication constraints of sensor networks challenge the efficient application of established estimation methods in sensor networks. In this paper, we present an approach using Gaussian kernel estimation to process spatial window queries over continuous phenomena in sensor networks. The key contribution of our approach is the use of a small number of Hermite coefficients to approximate the Gaussian kernel function for subclustered sensor nodes. As a result, our algorithm reduces the size of messages transmitted in the network by logarithmic order, thus saving resources while still providing high-quality query results. View full abstract»

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  • Comments on "Optimal Resource Allocation in Overlay Multicast"

    Page(s): 572 - 573
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    In this comments paper, we revisit the network model introduced in Cui, Y., et al (2006). We discuss the inaccuracy of the model and, to correct the network model, we propose to apply directed capacity constraints for directed flows. Based on a comparison of numerical results, we show that the corrected model leads to better accuracy than the original model. View full abstract»

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    Page(s): 574
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    Page(s): 575
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    Page(s): 576
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  • TPDS Information for authors

    Page(s): c3
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  • [Back cover]

    Page(s): c4
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Aims & Scope

IEEE Transactions on Parallel and Distributed Systems (TPDS) is published monthly. It publishes a range of papers, comments on previously published papers, and survey articles that deal with the parallel and distributed systems research areas of current importance to our readers.

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Meet Our Editors

Editor-in-Chief
David Bader
College of Computing
Georgia Institute of Technology