Conference Papers

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Author: search.filters.author.Rathod, V.J.Subject: search.filters.subject.CoAP

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    Effective RTO estimation using Eifel Retransmission Timer in CoAP
    (Institute of Electrical and Electronics Engineers Inc., 2020) Rathod, V.J.; Krishnam, S.; Kumar, A.; Baraskar, G.; Tahiliani, M.P.
    Internet of Things (IoT) is a system of interrelated devices with communication capabilities. Network congestion increases as the number of devices increase in the system and de-grades the Quality of Service (QoS). Unlike traditional Internet, TCP is not the de facto transport protocol for IoT because of the constrained nature of IoT devices. Therefore, congestion control mechanisms are coupled with application protocols, such as the Constrained Application Protocol (CoAP). Although there have been efforts to use CoAP with TCP, it typically uses UDP for data transport. CoAP defines a conservative congestion control mechanism that uses a fixed Retransmission TimeOut (RTO) for retransmissions regardless of the network conditions (e.g., Round Trip Time (RTT)). The Eifel Retransmission Timer is a popular algorithm originally proposed for TCP. It assesses prevalent network conditions by measuring RTT and accordingly sets the TCP RTO. This paper proposes to leverage the benefits of Eifel Retransmission Timer by integrating it with CoAP (when used with UDP) to obtain better RTO estimates and control congestion. The proposed algorithm is named as CoAP-Eifel. The effectiveness of the proposed approach has been validated by comparing it with the standard RTO estimation technique of CoAP. The experiments are carried out in a real testbed by using FIT/IoT-LAB. The results demonstrate that the proposed approach provides a better trade-off in terms of delay and throughput, without affecting the packet delivery ratio. © 2020 IEEE.
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    Geometric Sequence Technique for Effective RTO Estimation in CoAP
    (IEEE Computer Society, 2020) Rathod, V.J.; Tahiliani, M.P.
    Internet of Things (IoT) is a network where physical objects with Internet connectivity can interact and exchange information with other connected objects. IoT devices are constrained in terms of power and memory, and have limited communication capabilities. The Constrained Application Protocol (CoAP) is a lightweight messaging protocol which is widely used by various IoT applications in low power and lossy wireless networks. CoAP provides reliability and minimal congestion control via a fixed Retransmission TimeOut (RTO) and Binary Exponential Backoff (BEB). It does not maintain end-to-end connection information and therefore, cannot adapt RTO based on the network conditions. Moreover, CoAP resets the RTO to its default value after having received the ACK for the retransmitted packet. This approach of resetting the RTO degrades the performance in a network with high latency and leads to spurious retransmissions. In this paper, we propose a Geometric Sequence Technique (GST) for effective RTO estimation in CoAP. GST retains the previous RTO value after having received the ACK for the retransmitted packet and eventually returns to the default value by decreasing the RTO depending on the number of consecutive successful transmissions. The proposed technique is implemented in Contiki OS and validated against the existing mechanisms. The experiments have been conducted using the Cooja simulator and the FIT/IoT-LAB testbed to verify the effectiveness of the proposed technique. The results show that GST minimizes the Flow Completion Times (FCT), reduces the number retransmissions and improves the network throughput. © 2020 IEEE.