EnhancedBit: Unleashing the potential of the unchoking policy in the BitTorrent protocol

V. Atlidakis, M. Roussopoulos, A. Delis

Research output: Contribution to journalArticlepeer-review


In this paper, we propose a modification to the BitTorrent protocol related to its peer unchoking policy. In particular, we apply a novel optimistic unchoking approach that improves the quality of inter-connections amongst peers, i.e., increases the number of directly-connected and interested-in-cooperation peers without penalizing underutilized and/or idle peers. Our optimistic unchoking policy takes into consideration the number of clients currently interested in downloading from a peer that is to be unchoked. Our conjecture is that peers having few clients interested in downloading data from them, should be favored with optimistic unchoke intervals. This enables the peers in question to receive data since they become unchoked faster and in turn, they will trigger the interest of additional clients. In contrast, peers with plenty of "interested" clients should enjoy a lower priority to be selected as planned optimistic unchoked, since these peers likely have enough data to forward; nevertheless, they receive enough data due to tit-for-tat peer reciprocation and are not in need of optimistic unchoking slots. Armed with this realization, we establish an analytical model and prove a significant performance improvement under our modified BitTorrent protocol. Experimental results, also, indicate that our approach significantly outperforms the existing optimistic unchoking policy in three important aspects: first, there is a higher number of interested-in-cooperation and directly-connected peers. Second, since leechers now act as data intermediaries, the load on seeders eases up considerably. Last, a shorter bootstrapping period for fresh peers is achieved. Hence, we claim that our approach helps implement an enhanced BitTorrent protocol and we name it "EnhancedBit".

Original languageEnglish (US)
Pages (from-to)1959-1970
Number of pages12
JournalJournal of Parallel and Distributed Computing
Issue number1
StatePublished - Jan 2014


  • BitTorrent
  • Content distribution
  • Incentive protocols
  • Peer-to-peer (P2P)

ASJC Scopus subject areas

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture
  • Computer Networks and Communications
  • Artificial Intelligence


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