Peer Selection Strategies for Improved QoS in Heterogeneous BitTorrent-Like VoD Systems

Abstract

The efficiency of BitTorrent in disseminating content has inspired a number of P2P protocols for on-demand video streaming (VoD). Prior work on adapting BitTorrent to VoD mainly focused on the piece selection policy, since streaming requires a somewhat "in order" download progress. Conversely, not much effort has been spent into adapting BitTorrent's peer selection policy, where nodes mainly serve those that have recently uploaded to them at the highest rates. This mechanism incentivizes cooperation among peers but, in a heterogeneous system (i.e. where peers have different bandwidth capacities), it causes faster peers to receive higher download speeds than slower peers. This might hurt the system's ability of providing as many nodes as possible with the minimum download speed necessary to sustain the video playback rate. Furthermore, peers gain little utility in downloading at rates much higher than the video playback rate. Inspired by these observations, in this work, we extend the peer selection mechanism of an existing BitTorrentlike VoD protocol, give-to-get (G2G), with techniques that allow peers to relax their reciprocity-based peer selection and choose more random nodes when their current QoS is high. In this way, more peers can be granted a good QoS and free-riding is tolerated only when bandwidth resources are abundant. To demonstrate the benefits of our approach, we present extensive simulations of the introduced techniques.

Improving BitTorrent's Peer Selection for Multimedia Content On-Demand Delivery

“…Plenty of practical P2P approaches, like the BitTorrent protocol [6], have been successful in the past years. In fact, the great efficiency achieved by BitTorrent for the distribution of large amounts of data inspired its adoption for on-demand video streaming [7][8][9].…”

“…By stimulating direct reciprocity and cooperation, its design specifies who makes use of the uplink capacity from all the peers inside the swarm (i.e., a group of peers downloading a same content). One observed outcome of this policy is that in a heterogeneous system, i.e., where users have different bandwidth capacities, peers with higher upload capacities typically have higher download speeds than slower peers [7].…”

“…Plenty of practical P2P approaches, like the BitTorrent protocol [6], have been successful in the past years. In fact, the great efficiency achieved by BitTorrent for the distribution of large amounts of data inspired its adoption for on-demand video streaming [7][8][9].Peer-Selection Policy is the term assigned to one of the core concepts of BitTorrent. By stimulating direct reciprocity and cooperation, its design specifies who makes use of the uplink capacity from all the peers inside the swarm (i.e., a group of peers downloading a same content).…”

“…By stimulating direct reciprocity and cooperation, its design specifies who makes use of the uplink capacity from all the peers inside the swarm (i.e., a group of peers downloading a same content). One observed outcome of this policy is that in a heterogeneous system, i.e., where users have different bandwidth capacities, peers with higher upload capacities typically have higher download speeds than slower peers [7].However, one essential understanding is that peers receiving a multimedia stream do not need a download rate higher than the playback rate of the media file. Rigorously, all they need is a policy that makes the whole system efficiently allocate its total upload/download capacity so that all of its participants may be served satisfactorily.…”

“…There may be more than three slots though (a maximum of two more), if there is still spare upload capacity left due to current downloading bottlenecks on the already unchoked peers. The attempt is to maximize the bandwidth utilization by increasing the means of cooperation among peers.The characteristic (1) is also focused in the work of D'Acunto et al [7]. Their proposal is mainly devoted to heterogeneous environments and, accordingly, the number of upload slots is adjustable depending on the peer's total upload bandwidth.…”