Multi-Swarm Collaboration for Improving Content Availability in Swarming Systems

Despite its great success, BitTorrent suffers from a content unavailability problem where peers can not complete their content downloads due to some missing chunks, which is caused by an absence of seeders. Multi-swarm collaboration approach is a natural choice for improving the content avail- ability, since the content unavailability can not be managed by one swarm easily. Most existing multi-swarm collaboration approaches, however, show content-related limitations, which limit their application scopes. In this paper, we introduce a new kind of multi-swarm collaboration utilizing a swarm as a temporal storage. In a nutshell, the collaborating swarms cache some chunks of each other that are likely to be unavailable when the seeders are online and share the cached chunks when the content unavailability happens. Our approach enables any swarms to collaborate with each other without the content-related limitations. Simulation results show that our approach improves the number of download completions by over 50% compared to vanilla BitTorrent with low caching overhead. The results also show that our approach enables the peers participating in our approach to enjoy better performance than other peers, which can be an peer incentive.