Researcher:
Hassanzadeh-Nazarabadi, Yahya

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PhD Student

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Yahya

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Hassanzadeh-Nazarabadi

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Hassanzadeh-Nazarabadi, Yahya

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Now showing 1 - 10 of 17
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    Publication
    Awake: decentralized and availability aware replication for P2P cloud storage
    (Ieee, 2016) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Küpçü, Alptekin; Özkasap, Öznur; PhD Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 168060; 113507
    The traditional decentralized availability-based replication algorithms suffer from high dependence on the underlying system's churn behavior, randomness in replica selection, and the inability of maximizing the replicas availability. These drawbacks result in poor data availability especially in low available systems as well as where the churn behavior is mispredicted. In this paper, we propose dynamic, fully decentralized availability aware algorithm named Awake, with the goal of maximizing the availability of replicas. Compared to the existing solutions, Awake always provides the maximum availability of replicas regardless of the underlying system's churn behavior. By employing Awake, a data owner can select its replicas only based on the aggregated availability information of nodes obtained in a fully decentralized manner with asymptotically the same message overhead as the communication complexity of the underlying system. Awake has linear space complexity in the number of registered users to the system. Our extensive simulation results show that in comparison to the best existing decentralized solutions, regardless of the underlying churn model of the system, Awake improves the availability of replicas with a gain of about 21%. Likewise, Awake is scalable by showing the same performance independent of the system size.
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    A consensus protocol with deterministic finality
    (Ieee, 2021) N/A; N/A; N/A; Hassanzadeh-Nazarabadi, Yahya; Boshrooyeh, Sanaz Taheri; PhD Student; PhD Student; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A
    Proof-of-Validation (PoV) is a fair, immutable, and fully decentralized blockchain consensus protocol with an O(1) asymptotic message complexity. The original PoV proposal lacks deterministic finality, which guarantees that a valid block will not be revoked once it is committed to the blockchain. Supporting deterministic finality yields a fork-resistant blockchain. In this extended abstract, we pitch the architectural outline of our proposed Finalita, which is the extension of PoV that enables deterministic finality. Blockchains running with Finalita feature deterministic finality, in addition to all qualities supported by the original PoV.
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    LARAS: locality aware replication algorithm for the Skip Graph
    (Institute of Electrical and Electronics Engineers (IEEE), 2016) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Küpçü, Alptekin; Özkasap, Öznur; PhD Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 168060; 113507
    Skip Graph, a member of the distributed hash table (DHT) family, has several benefits as an underlying structure in peer-to-peer (P2P) storage systems. In such systems, replication plays a key role on the system's performance. The traditional decentralized replication algorithms do not consider the locations of Skip Graph nodes in the network. Negligence of node locations in the placement of the replicas results in high access delays between the nodes and their closest replicas. This negatively affects the performance of the whole storage system. In this paper, with the aim of making Skip Graph's replication locality aware, we propose dynamic fully decentralized LARAS approach, where the data owner can replicate itself based on the system size, possible data requester nodes' set and using local information of the storage system. Our extensive performance results show that LARAS improves replication access delay of the Skip Graph based storage system about 20% and 38% in comparison to the best known decentralized counterpart in the public and private replication scenarios, respectively.
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    Locality aware skip graph
    (IEEE, 2015) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Küpçü, Alptekin; Özkasap, Öznur; PhD Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 168060; 113507
    Skip Graph, as a distributed hash table (DHT) based data structure, plays a key role in peer-to-peer (P2P) storage systems, distributed online social networks, search engines, and several DHT-based applications. In the Skip Graph structure, node identifiers define the connectivity. However, traditional identifier assignment algorithms do not consider the Skip Graph nodes' locations. Neglecting the nodes' localities in the identifier assignments results in high end-to-end latency in the overlay network which negatively affects the overall system performance. In this paper, we propose a method to assign the Skip Graph node identifiers considering their location information and make the nodes locality aware. In the proposed dynamic and fully decentralized algorithm, named DPAD, instead of assigning node identifiers uniformly at random, locality aware identifiers will be assigned to the nodes at their arrival to the system based on their distances to some super-nodes named landmarks. We define locality awareness as the similarity of the distances between the nodes in the overlay and underlay networks. Performance analysis results show that DPAD algorithm provides about 82% improvement in the locality awareness of node identifiers and about 40% improvement in the search query end-to-end latency, compared to the best known static and dynamic algorithms.
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    Decentralized utility- and locality-aware replication for heterogeneous DHT-based P2P cloud storage systems
    (IEEE Computer Soc, 2020) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Küpçü, Alptekin; Özkasap, Öznur; PhD Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 168060; 113507
    As a Distributed Hash Table (DHT), Skip Graph routing overlays are exploited in several peer-to-peer (P2P) services, including P2P cloud storage. The fully decentralized replication algorithms that are applicable to the Skip Graph-based P2P cloud storage fail on improving the performance of the system with respect to both the availability of replicas as well as their response time. Additionally, they presume the system as homogeneous with respect to the nodes' latency distribution, availability behavior, and bandwidth, or storage. In this article, we propose Pyramid, which is the first fully decentralized utility- and locality-aware replication approach for Skip Graph-based P2P cloud storage systems. Pyramid considers the nodes as heterogeneous with respect to their latency distribution, availability behavior, bandwidth, and storage. Pyramid is utility-aware as it maximizes the average available bandwidth of replicas per time slot (e.g., per hour). Additionally, Pyramid is locality-aware as it minimizes the average latency between nodes and their closest replica. Our simulation results show that compared to the state-of-the-art solutions that either perform good in utility-awareness, or in locality-awareness, our proposed Pyramid improves both the utility- and locality-awareness of replicas with a gain of about 1.2 and 1.1 times at the same time, respectively.
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    SkipVis: a skip graph visualizer
    (Institute of Electrical and Electronics Engineers (IEEE), 2018) Menceloglu, Esin; N/A; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Ekmekci, Canberk; Özkasap, Öznur; PhD Student; Undergraduate Student; Faculty Member; Department of Electrical and Electronics Engineering; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 113507
    Skip Graph is a network overlay structure utilized in distributed data storage services as well as systems such as P2P cloud storage, search engines, Internet-of-Things, and mobile sensor networks. We propose SkipVis: a Skip Graph overlay visualizer that facilitates the flaw detection of Skip Graph-based algorithms in their design phase and also the implementation correctness verifiability. To the best of our knowledge, there exists no overlay visualizer for Skip Graph structure. Therefore, SkipVis is designed and developed as a scalable open source Skip Graph overlay visualizer that provides an interactive graphical user interface. In this paper, we describe SkipVis design principles, configuration, architecture and demonstration scenario.
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    ELATS: Energy and locality aware aggregation tree for skip graph
    (Institute of Electrical and Electronics Engineers (IEEE), 2018) N/A; N/A; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Özkasap, Öznur; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 113507
    As a distributed hash table (DHT), Skip Graph acts as the underlying routing infrastructure of peer-to-peer (P2P) storage systems, distributed online social networks, search engines, and other DHT-based applications. For many P2P applications, data aggregation is vital, however, it is a missing feature of Skip Graph. The traditional aggregation algorithms cost noticeable message overhead which degrades the energy efficiency while increasing the response time. Likewise, the aggregation trees proposed for other DHTs are either inapplicable to the Skip Graph or apply some sort of randomness in their construction. Randomized features of an aggregation tree result in higher aggregation latency as well as enforcing unbalanced load on nodes which negatively affect the energy efficiency. In this paper, we propose ELATS which is the first energy and locality aware aggregation tree for Skip Graph. We define the energy awareness as minimizing the average energy cost of an aggregation tree, and the locality awareness as minimizing the latency on the path between the root and leaves of the aggregation tree. Performance analysis results show that ELATS algorithm provides both energy and locality awareness, and improves the aggregation latency with the gain of about 8% in comparison to the best existing solutions for DHTs which are either locality aware or energy aware.
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    SkipSim: scalable skip graph simulator
    (Ieee, 2020) N/A; N/A; Department of Computer Engineering; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Şahin, Ali Utkan; Özkasap, Öznur; Küpçü, Alptekin; PhD Student; Undergraduate Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; N/A; 113507; 168060
    SkipSim is an offline Skip Graph simulator that enables Skip Graph-based algorithms including blockchains and P2P cloud storage to be simulated, while preserving their scalability and decentralized nature. To the best of our knowledge, it is the first Skip Graph simulator that provides several features for experimentation on Skip Graph-based overlay networks. In this demo paper, we present SkipSim features, its architecture, as well as a sample blockchain demo scenario.
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    Opera: scalable simulator for distributed systems
    (Ieee, 2021) N/A; N/A; Department of Computer Engineering; N/A; Hassanzadeh-Nazarabadi, Yahya; Ali, Moayed Haji; Nayal, Nazir; PhD Student; Undergraduate Student; Master Student; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; N/A; N/A
    Opera is a scalable local simulation network for experimental researches on distributed systems. To the best of our knowledge, it is the first Java-based event-driven simulator for distributed systems with a modular network, induced churn and latency traces from real-world systems, full life cycle management of the nodes, and a production-grade simulation monitoring. In this demo paper, we present the key features of Opera, its software architecture, as well as a sample demo scenario.
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    A containerized proof-of-concept implementation of LightChain system
    (Ieee, 2020) N/A; N/A; Department of Computer Engineering; N/A; Department of Computer Engineering; Department of Computer Engineering; Hassanzadeh-Nazarabadi, Yahya; Nayal, Nazir; Hamdan, Shadi Sameh; Özkasap, Öznur; Küpçü, Alptekin; PhD Student; Faculty Member; Master Student; Faculty Member; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; 113507; 168060
    LightChain is the first Distributed Hash Table (DHT)-based blockchain with a logarithmic asymptotic message and memory complexity. In this demo paper, we present the software architecture of our open-source implementation of LightChain, as well as a novel deployment scenario of the entire LightChain system on a single machine aiming at results reproducibility.