``Measurement, analysis, and modeling of BitTorrent-like systems" 

Lei Guo, Songqing Chen, Zhen Xiao, Enhua Tan, Xiaoning Ding, and Xiaodong Zhang 

Proceedings of ACM SIGCOMM Internet Measurement Conference, (IMC'05), 
New Orleans, LA, October 19-21, 2005. 


Existing studies on BitTorrent systems are single-torrent based, while
more than 85% of all peers participate in multiple torrents according to
our trace analysis. In addition, these studies are not sufficiently
insightful and accurate even for single-torrent models, due to some
unrealistic assumptions. Our analysis of representative BitTorrent
traffic provides several new findings regarding the limitations of
BitTorrent systems: (1) Due to the exponentially decreasing peer arrival
rate in reality, service availability in such systems becomes poor
quickly, after which it is difficult for the file to be located and
downloaded. (2) Client performance in the BitTorrent-like systems is
unstable, and fluctuates widely with the peer population. (3) Existing
systems could provide unfair services to peers, where peers with high
downloading speed tend to download more and upload less. In this paper,
we study these limitations on torrent evolution in realistic
environments. Motivated by the analysis and modeling results, we further
build a graph based multi-torrent model to study inter-torrent
collaboration. Our model quantitatively provides strong motivation for
inter-torrent collaboration instead of directly stimulating seeds to
stay longer. We also discuss a system design to show the feasibility of
multi-torrent collaboration.