By Topic

Parallel and Distributed Systems, IEEE Transactions on

Issue 6 • Date June 2010

Filter Results

Displaying Results 1 - 17 of 17
  • [Front cover]

    Page(s): c1
    Save to Project icon | Request Permissions | PDF file iconPDF (109 KB)  
    Freely Available from IEEE
  • [Inside front cover]

    Page(s): c2
    Save to Project icon | Request Permissions | PDF file iconPDF (140 KB)  
    Freely Available from IEEE
  • Editor's Note

    Page(s): 737 - 738
    Save to Project icon | Request Permissions | PDF file iconPDF (140 KB)  
    Freely Available from IEEE
  • Buffer Management Strategies to Reduce HoL Blocking

    Page(s): 739 - 753
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4113 KB) |  | HTML iconHTML  

    Congestion management is likely to become a critical issue in interconnection networks, as increasing power consumption and cost concerns lead to improvements in the efficiency of network resources. In previous configurations, networks were usually oversized and underutilized. In a smaller network, however, contention is more likely to occur and blocked packets cause head-of-line (HoL) blocking among the rest of the packets, spreading congestion quickly. The best-known solution to HoL blocking is Virtual Output Queues (VOQs). However, the cost of implementing VOQs increases quadratically with the number of output ports in the network, making it unpractical. The situation is aggravated when several priorities and/or Quality of Service (QoS) levels must be supported. Therefore, a more scalable and cost-effective solution is required to reduce or eliminate HoL blocking. In this paper, we present a family of methodologies, referred to as Destination-Based Buffer Management (DBBM), to reduce/eliminate the HoL blocking effect on interconnection networks. DBBM efficiently uses the resources (mainly memory queues) of the network. These methodologies are comprehensively evaluated in terms of throughput, scalability, and fairness. Results show that using the DBBM strategy, with a reduced number of queues at each switch, it is possible to achieve roughly the same throughput as the VOQ mechanism. Moreover, all of the proposed strategies are designed in such a way that they can be used in any switch architecture. We compare DBBM with RECN, a sophisticated mechanism that eliminates HoL blocking in congestion situations. Our mechanism is able to achieve almost the same performance with very low logic requirements (in contrast with RECN). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Cross-Domain Data Sharing in Distributed Electronic Health Record Systems

    Page(s): 754 - 764
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (610 KB) |  | HTML iconHTML  

    Cross-organization or cross-domain cooperation takes place from time to time in Electronic Health Record (EHR) system for necessary and high-quality patient treatment. Cautious design of delegation mechanism must be in place as a building block of cross-domain cooperation, since the cooperation inevitably involves exchanging and sharing relevant patient data that are considered highly private and confidential. The delegation mechanism grants permission to and restricts access rights of a cooperating partner. Patients are unwilling to accept the EHR system unless their health data are guaranteed proper use and disclosure, which cannot be easily achieved without cross-domain authentication and fine-grained access control. In addition, revocation of the delegated rights should be possible at any time during the cooperation. In this paper, we propose a secure EHR system, based on cryptographic constructions, to enable secure sharing of sensitive patient data during cooperation and preserve patient data privacy. Our EHR system further incorporates advanced mechanisms for fine-grained access control, and on-demand revocation, as enhancements to the basic access control offered by the delegation mechanism, and the basic revocation mechanism, respectively. The proposed EHR system is demonstrated to fulfill objectives specific to the cross-domain delegation scenario of interest. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Update Scheduling for Improving Consistency in Distributed Virtual Environments

    Page(s): 765 - 777
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2441 KB) |  | HTML iconHTML  

    The fundamental goal of distributed virtual environments (DVEs) is to create a common and consistent presentation of the virtual world among a set of computers interconnected by a network. This paper investigates update scheduling algorithms to make efficient use of network capacity and improve consistency in DVEs. Our approach is to schedule state updates according to their potential impacts on consistency. In DVEs, the perceptions of participants are affected by both the spatial magnitude and temporal duration of inconsistency in the virtual world. Using the metric of time-space inconsistency, we analytically derive the optimal update schedules for minimizing the impact of inconsistency. Based on the analysis, we propose a number of scheduling algorithms that integrate spatial and temporal factors. These algorithms also take into consideration the effect of network delays. The algorithms can be used on top of many existing mechanisms such as dead reckoning. Experimental results show that our proposed algorithms significantly outperform the intuitive algorithms that are based on spatial or temporal factors only. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the Benefit of Processor Coallocation in Multicluster Grid Systems

    Page(s): 778 - 789
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2107 KB) |  | HTML iconHTML  

    In multicluster grid systems, parallel applications may benefit from processor coallocation, that is, the simultaneous allocation of processors in multiple clusters. Although coallocation allows the allocation of more processors than available in a single cluster, it may severely increase the execution time of applications due to the relatively slow wide-area communication. The aim of this paper is to investigate the benefit of coallocation in multicluster grid systems, despite this drawback. To this end, we have conducted experiments in a real multicluster grid environment, as well as in a simulated environment, and we evaluate the performance of coallocation for various applications that range from computation-intensive to communication-intensive and for various system load settings. In addition, we compare the performance of scheduling policies that are specifically designed for coallocation. We demonstrate that considering latency in the resource selection phase improves the performance of coallocation, especially for communication-intensive parallel applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Minimum Latency Gossiping in Radio Networks

    Page(s): 790 - 800
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1436 KB) |  | HTML iconHTML  

    We studied the minimum latency gossiping (all-to-all broadcast) problem in multihop radio networks defined as follows: Each node in the network is preloaded with a message and the objective is to distribute each node's message to the entire network with minimum latency. We studied this problem in the unit-size message model and the unit disk graph model. The unit-size model means different messages cannot be combined as one message, and the unit disk graph model means a link exists between two nodes if and only if their euclidean distance is less than 1. The minimum latency gossiping problem is known to be NP-hard in these two models. In this work, we designed a gossiping scheme that significantly improved all current gossiping algorithms in terms of the approximation ratio. Our work has approximation ratio 27, a great improvement of the current state-of-the-art algorithm (which has ratio 1,947). We also discussed the single point of failure problem and its impact on our approximation ratio. We designed an amended gossiping algorithm with ratio 27 in case of a nonsource node failure. We also designed an amended gossiping algorithm with ratio 29 in case of source failure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reliable Broadcast in Radio Networks with Locally Bounded Failures

    Page(s): 801 - 811
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1549 KB) |  | HTML iconHTML  

    This paper studies the reliable broadcast problem in a radio network with locally bounded failures. We present a sufficient condition for achievability of reliable broadcast in a general graph subject to Byzantine/crash-stop failures. We then consider the problem of reliable broadcast in an infinite grid (or finite toroidal) radio network under Byzantine and crash-stop failures. We present bounds on the maximum number of failures that may occur in any given neighborhood without rendering reliable broadcast impossible. For the Byzantine failure model, we describe an algorithm which is optimal for the grid network model, as it tolerates faults up to a previously established upper bound for this model. Our results indicate that it is possible to achieve reliable broadcast if slightly less than one-fourth fraction of nodes in any neighborhood are faulty. We also show that reliable broadcast is achievable with crash-stop failures if slightly less than half the nodes in any given neighborhood may be faulty. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Global Contribution Approach to Maintain Fairness in P2P Networks

    Page(s): 812 - 826
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4423 KB) |  | HTML iconHTML  

    For many P2P systems, implementing right incentives and policies to promote efficient and fair resource sharing is the key to improve the overall system performance. In this paper, we propose a points-based incentive mechanism named Global Contribution (GC) approach that efficiently and naturally maintains fairness in a P2P network. In this approach, a proposed GC algorithm first calculates a global score for each peer that accurately reflects its bandwidth contribution to the entire network. Then, these scores are used in a proposed data transfer policy to determine whether one peer can download data from other peers. Thus, the GC approach achieves: (1) efficiently preventing free-riding, (2) naturally balancing the upload and download amounts in each peer, and (3) reducing rejections in transactions between cooperative peers. Moreover, the GC algorithm requires only private transaction history as an input and can be fully decentralized. Also, its time complexities are approximately O(N2) in a centralized system and O(N) per peer in a decentralized system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An Efficient and Adaptive Decentralized File Replication Algorithm in P2P File Sharing Systems

    Page(s): 827 - 840
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1437 KB) |  | HTML iconHTML  

    In peer-to-peer file sharing systems, file replication technology is widely used to reduce hot spots and improve file query efficiency. Most current file replication methods replicate files in all nodes or two end points on a client-server query path. However, these methods either have low effectiveness or come at a cost of high overhead. File replication in server side enhances replica hit rate, hence, lookup efficiency but produces overloaded nodes and cannot significantly reduce query path length. File replication in client side could greatly reduce query path length, but cannot guarantee high replica hit rate to fully utilize replicas. Though replication along query path solves these problems, it comes at a high cost of overhead due to more replicas and produces underutilized replicas. This paper presents an Efficient and Adaptive Decentralized (EAD) file replication algorithm that achieves high query efficiency and high replica utilization at a significantly low cost. EAD enhances the utilization of file replicas by selecting query traffic hubs and frequent requesters as replica nodes, and dynamically adapting to nonuniform and time-varying file popularity and node interest. Unlike current methods, EAD creates and deletes replicas in a decentralized self-adaptive manner while guarantees high replica utilization. Theoretical analysis shows the high performance of EAD. Simulation results demonstrate the efficiency and effectiveness of EAD in comparison with other approaches in both static and dynamic environments. It dramatically reduces the overhead of file replication, and yields significant improvements on the efficiency and effectiveness of file replication in terms of query efficiency, replica hit rate, and overloaded nodes reduction. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal Swarming for Massive Content Distribution

    Page(s): 841 - 856
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1532 KB) |  | HTML iconHTML  

    A distinct trend has emerged that the Internet is used to transport data on a more and more massive scale. Capacity shortage in the backbone networks has become a genuine possibility, which will be more serious with fiber-based access. The problem addressed in this paper is how to conduct massive content distribution efficiently in the future network environment, where the capacity limitation can equally be at the core or the edge. We propose a novel technique as a main content transport mechanism to achieve efficient network resource utilization. The technique uses multiple trees for distributing different file pieces, which at the heart is a version of swarming. In this paper, we formulate an optimization problem for determining an optimal set of distribution trees as well as the rate of distribution on each tree under bandwidth limitation at arbitrary places in the network. The optimal solution can be found by a distributed algorithm. The results of the paper not only provide stand-alone solutions to the massive content distribution problem, but should also help the understanding of existing distribution techniques such as BitTorrent or FastReplica. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Streamline: An Optimal Distribution Algorithm for Peer-to-Peer Real-Time Streaming

    Page(s): 857 - 871
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2561 KB) |  | HTML iconHTML  

    In this paper, we propose and evaluate an overlay distribution algorithm for P2P, chunk-based, streaming systems over forest-based topologies. In such systems, the stream is divided in chunks; chunks are delivered by each node in a store-and-forward way. A relaying node starts distributing a chunk only when it has completed its reception from another node. Peers are logically organized in a forest of trees, where each tree includes all peers. The source periodically distributes different chunks to each tree for their delivery. Our key idea consists in employing serial transmission: for each tree, and thus, for each chunk, the source node sends the chunk to its children in series; the same holds for each peer node of the tree, excluding the leaves. Besides this basic idea, the contributions of this paper are: 1) we demonstrate the feasibility of serial transmission over a forest of trees, which is not a trivial problem, unlike the case of parallel transmission; 2) we derive an analytical model to evaluate the system performance; 3) we derive a theoretical bound for the number of nodes reachable in a given time interval or equivalently for the time required to reach a given number of nodes; 4) we prove the optimality of our approach in terms of its capability to reach such bound; and 5) we develop a general simulation package for P2P streaming systems and use it to compare our solution to literature results. Finally, we stress that this paper is focused on the theoretical properties and performance understanding of the proposed distribution algorithm, rather than on its practical implementation in a real system. However, we also briefly describe a practical workable implementation of our algorithm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Isoefficiency Maps for Divisible Computations

    Page(s): 872 - 880
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1616 KB) |  | HTML iconHTML  

    In this paper, we propose a new technique of presenting performance relationships in parallel processing. Performance of parallel processing is a hard matter with many counterintuitive phenomena. It is relatively easy to obtain some numerical indicators of the performance using various performance models. However, it is far more difficult to comprehend the nature of the analyzed problem. To facilitate understanding the performance relationships, we propose a new visualization technique based on the concept of isoefficiency. In this paper, isoefficiency is represented as a relation on points in the space of system parameters for which efficiency of parallel processing is equal. We visualize this relation on two-dimensional maps analogously to isobars and isotherms on weather maps. This concept is applied to depict the performance relationships in two standard performance laws: Amdahl's speedup law and Gustafson's speedup law. Then, we use isoefficiency maps to analyze the performance relationships in divisible load processing. Divisible load model conforms with data-parallel computations in an environment with communication delays. The results we obtain give interesting insights into relationships existing in parallel processing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Energy-Efficient Beaconless Geographic Routing in Wireless Sensor Networks

    Page(s): 881 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2830 KB) |  | HTML iconHTML  

    Geographic routing is an attractive localized routing scheme for wireless sensor networks (WSNs) due to its desirable scalability and efficiency. Maintaining neighborhood information for packet forwarding can achieve a high efficiency in geographic routing, but may not be appropriate for WSNs in highly dynamic scenarios where network topology changes frequently due to nodes mobility and availability. We propose a novel online routing scheme, called Energy-efficient Beaconless Geographic Routing (EBGR), which can provide loop-free, fully stateless, energy-efficient sensor-to-sink routing at a low communication overhead without the help of prior neighborhood knowledge. In EBGR, each node first calculates its ideal next-hop relay position on the straight line toward the sink based on the energy-optimal forwarding distance, and each forwarder selects the neighbor closest to its ideal next-hop relay position as the next-hop relay using the Request-To-Send/Clear-To-Send (RTS/CTS) handshaking mechanism. We establish the lower and upper bounds on hop count and the upper bound on energy consumption under EBGR for sensor-to-sink routing, assuming no packet loss and no failures in greedy forwarding. Moreover, we demonstrate that the expected total energy consumption along a route toward the sink under EBGR approaches to the lower bound with the increase of node deployment density. We also extend EBGR to lossy sensor networks to provide energy-efficient routing in the presence of unreliable communication links. Simulation results show that our scheme significantly outperforms existing protocols in wireless sensor networks with highly dynamic network topologies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • TPDS Information for authors

    Page(s): c3
    Save to Project icon | Request Permissions | PDF file iconPDF (140 KB)  
    Freely Available from IEEE
  • [Back cover]

    Page(s): c4
    Save to Project icon | Request Permissions | PDF file iconPDF (109 KB)  
    Freely Available from IEEE

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.

Full Aims & Scope

Meet Our Editors

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