Comparison of Crawling Strategies for an Optimized Mobile P2P Architecture
Mobile networks differ from their wireline counterparts mainly by the high costs for air transmissions and by the mobility of the users. A new entity, denoted as the crawling peer, is suggested in order to optimize the resource mediation mechanism for a mobile P2P file sharing application. In P2P networks there are two major functions, resource mediation and resource control. In recent works, the trend for realizing resource mediation tends towards structured P2P networks. However, in a mobile environment this approach is not suited due the introduced overhead and the resulting high costs of the air interface, the temporal and spatial mobility of the users, and the need for searching uniquely identifiable resources. In our approach, the crawling peer locates content on behalf of mobile peers. It is placed in the wireline part of the mobile network and thus, does not suffer from the above mentioned restrictions. The crawling peer is part of a comprehensive mobile P2P file sharing architecture which is based on the popular eDonkey file sharing application. The performance of three querying strategies of the crawling peer is investigated with respect to banning at the index servers and the response time of requests, i.e. the time to find a file. The results show that the selection of an appropriate request strategy for the crawling peer maximizes the probability of locating a file while the probability to be banned by an eDonkey index server is minimized.