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    Item type:Publication,
    Efficient Route Update and Maintenance for Reliable Routing in Large-Scale Sensor Networks
    (2017-02-01) ;
    Camtepe, Seyit
    ;
    Tian, Yu Chu
    Reliable data transmissions are challenging in industrial wireless sensor networks as channel conditions change over time. Rapid changes in channel conditions require accurate estimation of the routing path performance and timely update of the routing information. However, this is not well fulfilled in existing routing approaches. Addressing this problem, this paper presents combined global and local update processes for efficient route update and maintenance, and incorporates them with a hierarchical proactive routing framework. While the global process updates the routing path with a relatively long period, the local process with a shorter period checks potential routing path problems. A theoretical modeling is developed to describe the processes. Through simulations, the presented approach is shown to reduce end-to-end delay up to 30 times for large networks, while improving packet reception ratio (PRR) in comparison with hierarchical and proactive routing protocols ROL/NDC, DSDV, and DSDV with IPv6 Routing Protocol for Low-Power and Lossy Networks' Trickle algorithm. Compared with reactive routing protocols AODV and Ad Hoc On-demand Multipath Distance Vector, it provides similar PRR while reducing end-to-end delay over 15 times.
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    Item type:Publication,
    Resolving Load Imbalance State for SDN by Minimizing Maximum Load of Controllers
    (2021-10-01)
    Srisamarn, Ukrist
    ;
    ;
    Kitsuwan, Nattapong
    This paper proposes a scheme to practically resolve the load imbalance state for orchestrated multiple controllers architecture in software-defined networks (SDN). Multiple controllers architecture is crucial to SDN implementation in large scale networks because this architecture provides efficient performance for end-to-end services, such as reliability and scalability in SDN networks. However, when there are multiple SDN controllers in the network, a load imbalance state may occur. The load imbalance problem can notably degrade service level in some parts of the network because the SDN controllers in those network areas have much higher amount of processing load. Existing works solved the load imbalance problem by migrating the load to multiple SDN controllers in order to maintain an acceptable level of load in all SDN controllers. Nevertheless, most of these works did not consider propagation delay and processing time in their load definition. In large-scale networks, high propagation delay is likely to cause late response from the SDN controller, which may result in a degraded performance in the SDN networks. In this paper, a new load balancing scheme is proposed. The proposed scheme is formulated as an integer linear programming problem (ILP). It defines SDN controller’s load based on propagation delay, processing time at the controller and the number of request messages in order to provide an accurate representation of load in practical environments. Generally, ILP may take a long period of time to process. Therefore, a heuristic algorithm that bases on the proposed load balancing scheme is also developed to provide shorter processing time. Computer simulations and practical implementation in Pica8 switch show that the proposed scheme reduces the average maximum load by at least 9.85%, compared to a conventional scheme.