دانلود رایگان مقاله بررسی DHTs برای کاهش اثرات ریزش در شبکه تلفن همراه

Abstract

6. Conclusions and future work In this work, we have evaluated three systems, namely, Chord DHT, Chord–Chord HDHT and Chord–Kademlia HDHT, under various operating conditions. We have shown that the flat DHT performs poorly at high churn, prompting the need for a system with better support for mobile nodes. We have shown that the two hierarchical systems exhibit satisfactory performance even at the presence of churn. We discover that both HDHTs are more stable, more efficient and more scalable compared to the flat system and are therefore good candidates in alleviating the effects of churn in mobile networks. Chord–Chord HDHT is better than Chord DHT because of the cluster-based design resulting to better fault tolerance. It is more stable, more efficient and more scalable than Chord DHT. Similar to Chord–Chord HDHT, Chord–Kademlia HDHT also shows good performance. This work’s Chord–Kademlia HDHT implementation can be employed in mobile networks that need to be reliable and delayintolerant but are not bandwidth-constrained. Such networks require few lookup failures and fast lookup resolution to ensure that time-sensitive materials are received correctly and immediately. However if the main consideration is lightweight mobile application, our work’s Chord–Chord HDHT implementation is the better option. Mobile devices have limited capacities, which means short battery life and unreliable connectivity. Such devices require an application that can provide good lookup success and fast lookup latency, along with small bandwidth utilization to optimize the limited resources. In conclusion, we have shown that by using any of the two hierarchical DHTs, we can integrate mobile devices into the P2P paradigm.Existing flat peer-to-peer (P2P) systems based on distributed hash tables (DHTs) perform unsatisfactorily under churn due to their non-hierarchical topology. These flat DHTs (FDHTs) experience low lookup success ratio, high lookup latency and high bandwidth usage as a consequence of the presence of churn. With this, we explore the use of hierarchical DHT (HDHT), specifically the superpeer design, in mitigating the effects of churn. To the best of our knowledge, we are the first to intensively examine HDHTs with and without high churn through simulations. Using the OMNeT++ simulator and the OverSim framework, we analyze flat and hierarchical DHTs with and without churn. Results show that the implemented HDHTs perform more satisfactorily than a flat DHT because of better fault isolation and smaller cluster sizes at the cost of higher superpeer traffic. HDHTs are more stable as they have better lookup success ratios. They are more efficient as evidenced by lower lookup latencies and lower average node bandwidth usage. They are more scalable since their performance do not degrade significantly even at high population. With this, the implemented HDHTs can be utilized to alleviate the effects of churn in mobile networks.

6. Conclusions and future work

In this work, we have evaluated three systems, namely, Chord DHT, Chord–Chord HDHT and Chord–Kademlia HDHT, under various operating conditions. We have shown that the flat DHT performs poorly at high churn, prompting the need for a system with better support for mobile nodes. We have shown that the two hierarchical systems exhibit satisfactory performance even at the presence of churn. We discover that both HDHTs are more stable, more efficient and more scalable compared to the flat system and are therefore good candidates in alleviating the effects of churn in mobile networks. Chord–Chord HDHT is better than Chord DHT because of the cluster-based design resulting to better fault tolerance. It is more stable, more efficient and more scalable than Chord DHT. Similar to Chord–Chord HDHT, Chord–Kademlia HDHT also shows good performance. This work’s Chord–Kademlia HDHT implementation can be employed in mobile networks that need to be reliable and delayintolerant but are not bandwidth-constrained. Such networks require few lookup failures and fast lookup resolution to ensure that time-sensitive materials are received correctly and immediately. However if the main consideration is lightweight mobile application, our work’s Chord–Chord HDHT implementation is the better option. Mobile devices have limited capacities, which means short battery life and unreliable connectivity. Such devices require an application that can provide good lookup success and fast lookup latency, along with small bandwidth utilization to optimize the limited resources. In conclusion, we have shown that by using any of the two hierarchical DHTs, we can integrate mobile devices into the P2P paradigm.