Performance evaluation of a Kademlia-based communication-oriented P2P system under churn

摘要

The phenomenon of churn has a significant effect on the performance of Peer-to-Peer (P2P) networks, especially in mobile environments that are characterized by intermittent connections and unguaranteed network bandwidths. A number of proposals have been put forward to deal with this problem; however, we have so far not seen any thorough analysis to guide the optimal design choices and parameter configurations for structured P2P networks. In this article, we present a performance evaluation of a structured communication-oriented P2P system in the presence of churn. The evaluation is conducted using both simulation models and a real-life prototype implementation. In both evaluation environments, we utilize Kademlia with some modifications as the underlying distributed hash table (DHT) algorithm, and Peer-to-Peer Protocol (P2PP) as the signaling protocol. The results from the simulation models created using Nethawk EAST (a telecommunication simulator software) suggest that, in most situations, a lookup parallelism degree of 3 and resource replication degree of 3 are enough for guaranteeing a high resource lookup success ratio. We also notice that, with the parallel lookup mechanism, a good success ratio is achieved even without the KeepAlive traffic that is used for detecting the aliveness of nodes. A prototype system that works in mobile environment is implemented to evaluate the feasibility of mobile nodes acting as full-fledged peers. The measurements made using the prototype show that, from the viewpoints of CPU load and network traffic load, it is feasible for the mobile nodes to take part in the overlay. Through energy consumption measurements, we draw the conclusion that in general the UMTS access mode consumes slightly more power than the WLAN access mode. Protocol packets with sizes of 200 bytes or less are observed to be the most energy efficient in the UMTS access mode.