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Parallel and Distributed Systems, IEEE Transactions on

Issue 1 • Date Jan. 2009

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Displaying Results 1 - 16 of 16
  • [Front cover]

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

    Page(s): c2
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  • Design of Fast and Efficient Energy-Aware Gradient-Based Scheduling Algorithms Heterogeneous Embedded Multiprocessor Systems

    Page(s): 1 - 12
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2866 KB) |  | HTML iconHTML  

    In this paper, we present two heuristic energy-aware scheduling algorithms (EGMS and EGMSIV) for scheduling task precedence graphs in an embedded multiprocessor system having processing elements with dynamic voltage scaling capabilities. Unlike most energy-aware scheduling algorithms that consider task ordering and voltage scaling separately from task mapping, our algorithms consider them in an integrated way. EGMS uses the concept of energy gradient to select tasks to be mapped onto new processors and voltage levels. EGM-SIV extends EGMS by introducing intra-task voltage scaling using a Linear Programming (LP) formulation to further reduce the energy consumption. Through rigorous simulations, we compare the performance of our proposed algorithms with a few approaches presented in the literature. The results demonstrate that our algorithms are capable of obtaining energy-efficient schedules using less optimization time. On the average, our algorithms produce schedules which consume 10% less energy with more than 47% reduction in optimization time when compared to a few approaches presented in the literature. In particular, our algorithms perform better in generating energy-efficient schedules for larger task graphs. Our results show a reduction of up to 57% in energy consumption for larger task graphs compared to other approaches. View full abstract»

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  • A Switch Architecture Guaranteeing QoS Provision and HOL Blocking Elimination

    Page(s): 13 - 24
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    Both QoS support and congestion management techniques become essential to achieve good network performance in current high-speed interconnection networks. The most effective techniques traditionally considered for both issues, however, require too many resources for being implemented. In this paper we propose a new cost-effective switch architecture able to face the challenges of congestion management and, at the same time, to provide QoS. The efficiency of our proposal is based on using the resources (queues) used by RECN (an efficient Head-Of-Line blocking elimination technique) also for QoS support, without increasing queue requirements. Provided results show that the new switch architecture is able to guarantee QoS levels without any degradation due to congestion situations. View full abstract»

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  • Bipanconnectivity and Bipancyclicity in k-ary n-cubes

    Page(s): 25 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1339 KB) |  | HTML iconHTML  

    In this paper we give precise solutions to problems posed by Wang, An, Pan, Wang and Qu and by Hsieh, Lin and Huang. In particular, we show that Qn k is bipanconnected and edge-bipancyclic, when k ges 3 and n ges 2, and we also show that when k is odd, Qn k is m-panconnected, for m=(n(k-1)+2k-6)/2, and (k-1)-pancyclic (these bounds are optimal). We introduce a path-shortening technique, called progressive shortening, and strengthen existing results, showing that when paths are formed using progressive shortening then these paths can be efficiently constructed and used to solve a problem relating to the distributed simulation of linear arrays and cycles in a parallel machine whose interconnection network is Qn k, even in the presence of a faulty processor. View full abstract»

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  • Differentiated Bandwidth Allocation with TCP Protection in Core Routers

    Page(s): 34 - 47
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    Differentiated Services (DiffServ) networks categorize routers into edge routers and core routers. In core routers, one of the technological challenges is how to implement differentiated bandwidth allocation and TCP protection together with low complexity. We present an Active Queue Management (AQM) scheme called CHOKeW. A method is borrowed from a previous scheme, CHOKe, which draws a packet at random from the buffer, compares it with the arriving packet, and drops both if they are from the same flow. CHOKeW enhances the drawing function by adjusting the maximum number of draws based on the priority of the new arrival and the current status of network congestion. With respect to the number of flows, both the memory-requirement complexity and the per-packet-processing complexity for CHOKeW is O(1). An analytical model and multiple simulations are used to explain and evaluate CHOKeW. We show that CHOKeW is able to (1) support differentiated bandwidth allocation; (2) provide the flows in the same priority with better fairness than other conventional stateless AQM schemes such as RED and BLUE; (3) maintain high link utilization as well as short queue length; and (4) protect TCP flows by restricting the bandwidth share of high-speed unresponsive flows. View full abstract»

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  • Dynamic Routing with Security Considerations

    Page(s): 48 - 58
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2088 KB) |  | HTML iconHTML  

    Security has become one of the major issues for data communication over wired and wireless networks. Different from the past work on the designs of cryptography algorithms and system infrastructures, we aim at the proposing of a dynamic routing algorithm that could randomize delivery paths for data transmission. The algorithm is easy to implement and compatible with popular routing protocols, such as routing information protocol in wired networks and destination-sequenced distance vector protocol in wireless networks, without introducing extra control messages. An analytic study on the proposed algorithm is presented, and a series of simulation experiments are conducted to verify the analytic results and to show the capability of the proposed algorithm. View full abstract»

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  • A Trace-Driven Approach to Evaluate the Scalability of P2P-Based Video-on-Demand Service

    Page(s): 59 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2083 KB) |  | HTML iconHTML  

    Peer-to-Peer (P2P) networks have emerged as one of the most promising approaches to improve the scalability of Video-on-Demand (VoD) service over Internet. However, despite a number of architectures and streaming protocols have been proposed in past years, there is few work to study the practical performance of P2P-based VoD service especially in consideration of real user behavior which actually has significant impact on system scalability. Therefore, in this paper, we first characterize the user behavior by analyzing a large amount of real traces from a popular VoD system supported by the biggest television station in China, cctv.com. Then we ex-amine the practical scalability of P2P-based VoD service through extensive trace-driven simula-tion under a general system framework. The results show that P2P networks scale well in provid-ing VoD service under real user behavior by obtaining a considerable good cache hit ratio. Moreover, it is observed that adopting hard cache at client side help achieves better system scal-ability than that with soft cache. We also identify the impact of various aspects of user behavior upon system scalability through detailed simulation. We believe that our study will shine insight-ful light on the understanding of practical scalability of P2P-based VoD service and be helpful to future system design and optimization. View full abstract»

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  • Difficulty-Aware Hybrid Search in Peer-to-Peer Networks

    Page(s): 71 - 82
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    By combining an unstructured protocol with a DHT-based index, hybrid Peer-to-Peer (P2P) improves search efficiency in terms of query recall and response time. The key challenge in hybrid search is to estimate the number of peers that can answer a given query. Existing approaches assume that such a number can be directly obtained by computing item popularity. In this work, we show that such an assumption is not always valid, and previous designs cannot distinguish whether items related to a query are distributed in many peers or are in a few peers. To address this issue, we propose QRank, a difficulty-aware hybrid search, which ranks queries by weighting keywords based on term frequency. Using rank values, QRank selects proper search strategies for queries. We conduct comprehensive trace-driven simulations to evaluate this design. Results show that QRank significantly improves the search quality as well as reducing system traffic cost compared with existing approaches. View full abstract»

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  • Heuristic Discovery of Role-Based Trust Chains in Peer-to-Peer Networks

    Page(s): 83 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3473 KB) |  | HTML iconHTML  

    Credential chains are needed in trusted peer-to-peer (P2P) applications, where trust delegation must be established between each pair of peers at specific role level. Role-based trust is refined from the coarse-grained trust model used in most P2P reputation systems. This paper offers a novel heuristic-weighting approach to selecting the most likely path to construct a role-based trust chain. We apply history-sensitive heuristics to measure the path complexity and assess the chaining efficiency. We discover successive edges of a trust chain, adaptively, to match with the demands from various P2P applications. New heuristic chaining algorithms are developed for backward, forward, and bi-directional discovery of trust chains. Our heuristic chain discovery scheme shortens the search time, reduces the memory requirement, and enhances the chaining accuracy in scalable P2P networks. Consider a trust graph over N credentials and M distinct role nodes. Our heuristic trust-chain discovery algorithms require O(N2 logN) search time and O(M) memory space, if the secondary heuristics are generated off-line in advance. These are improved from O(N3) search time and O(NM) space required in non-heuristic discovery algorithms by Li, Winsborough, and Mitchell (2003). Our analytical results are verified by extensive simulation experiments over typical classes of role-based trust graphs. View full abstract»

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  • Optimizing the Throughput of Data-Driven Peer-to-Peer Streaming

    Page(s): 97 - 110
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3322 KB) |  | HTML iconHTML  

    During recent years, the Internet has witnessed a rapid growth in deployment of data-driven (or swarming based) peer-to-peer (P2P) media streaming. In these applications, each node independently selects some other nodes as its neighbors (i.e. gossip-style overlay construction), and exchanges streaming data with the neighbors (i.e. data scheduling). To improve the performance of such protocol, many existing works focus on the gossip-style overlay construction issue. However, few of them concentrate on optimizing the streaming data scheduling to maximize the throughput of a constructed overlay. In this paper, we analytically study the scheduling problem in data-driven streaming system and model it as a classical min-cost network flow problem. We then propose both the global optimal scheduling scheme and distributed heuristic algorithm to optimize the system throughput. Furthermore, we introduce layered video coding into data-driven protocol and extend our algorithm to deal with the end-host heterogeneity. The results of simulation with the real world traces indicate that our distributed algorithm significantly outperforms conventional ad hoc scheduling strategies especially in stringent buffer and bandwidth constraints. View full abstract»

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  • An Architectural Framework for Accurate Characterization of Network Traffic

    Page(s): 111 - 123
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2420 KB) |  | HTML iconHTML  

    In networks carrying large volume of traffic, accurate traffic characterization is necessary for understanding the dynamics and patterns of network resource usage. Previous approaches to flow characterization are based on random sampling of the packets (e.g., Cisco's NetFlow) or inferring characteristics solely based on long lived flows (LLFs) or on lossy data structures (e.g., bloom filters, hash tables). However, none of these approaches takes into account the heavy-tailed nature of the Internet traffic and separates the estimation algorithm from the flow measurement architecture.In this paper, we propose an alternate approach to traffic characterization by closely linking the flow measurement architecture with the estimation algorithm. Our measurement framework stores complete information related to short lived flows (SLFs) while collecting partial information related to LLFs. For real-time separation of LLFs and SLFs, we propose a novel algorithm based on typical sequences from information theory. The distribution (pdf) and sample space of the underlying traffic is estimated using the non-parametric Parzen window technique and likelihood function defined over the Coupon collector problem. We validate the accuracy and performance of our estimation technique using traffic traces from the internal LAN in our laboratory and from National Library for Applied Network Research (NLANR). View full abstract»

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  • Distributed Algorithms for Constructing Approximate Minimum Spanning Trees in Wireless Sensor Networks

    Page(s): 124 - 139
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1358 KB) |  | HTML iconHTML  

    While there are distributed algorithms for the MST problem, these algorithms require relatively large number of messages and time; this makes these algorithms impractical for resource-constrained networks such as ad hoc wireless sensor networks. In such networks, a sensor has very limited power, and any algorithm needs to be simple, local, and energy efficient for being practical. Motivated by these considerations, we design and analyze a class of simple and local distributed algorithms called nearest neighbor tree (NNT) algorithms for energy-efficient construction of MSTs in a wireless ad hoc setting. We assume that the nodes are uniformly distributed in a unit square and show provable bounds on the performance with respect to both the quality of the spanning tree produced and the energy needed to construct them. In particular, we show that NNT produces a close approximation to the MST, and they can be maintained dynamically with polylogarithmic number of rearrangements under node insertions/deletions. We also perform extensive simulations of our algorithms. We tested our algorithms on both uniformly random distributions of nodes, and on a realistic distributions of nodes in an urban setting. Simulations validate the theoretical results and show that the bounds are much better in practice. View full abstract»

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  • 2008 Reviewers List

    Page(s): 140 - 144
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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