Deep Inspection of Unreachable BitTorrent Swarms

Masahiro YOSHIDA  Akihiro NAKAO  

IEICE TRANSACTIONS on Information and Systems   Vol.E96-D    No.2    pp.249-258
Publication Date: 2013/02/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E96.D.249
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Section on The Internet Architectures, Protocols, and Applications for Diversified Futures)
peer-to-peer networks,  BitTorrent,  network measurement,  unreachable peers,  

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BitTorrent is one of the most popular P2P file sharing applications worldwide. Each BitTorrent network is called a swarm, and millions of peers may join multiple swarms. However, there are many unreachable peers (NATed (network address translated), firewalled, or inactive at the time of measurement) in each swarm; hence, existing techniques can only measure a part of all the peers in a swarm. In this paper, we propose an improved measurement method for BitTorrent swarms that include many unreachable peers. In essence, NATed peers and those behind firewalls are found by allowing them to connect to our crawlers by actively advertising our crawlers' addresses. Evaluation results show that the proposed method increases the number of unique contacted peers by 112% compared to the conventional method. Moreover, the proposed method increases the total volume of downloaded pieces by 66%. We investigate the sampling bias among the proposed and conventional methods, and we find that different measurement methods yield significantly different results.

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