點對點(P2P)網路下進行檔案分享是利用網路來完成分散式計算，在不考慮如版權等爭異的話題下，點對點網路確實加速了檔案(如影片或歌曲)的分享，根據片段來做檔案分享是在點對點網路下常見的方式，如BitTorrent (BT)。而BT使用的最稀有的片段優先傳送演算法確實加速了點對點網路的下載速度。近年來隨著異質網路的快速發展，人們使用網路的選擇變的多元化，所以造成了點對點網路中各個節點間的傳送速度會有所不同，然而在過去的研究很少在討論根據節點間的傳輸情況如何有效的做到檔案片段的排程。在本篇論文中我們提出了二種演算法-　(a) 最稀有的片段優先傳，有與傳送節點最小傳輸時間的節點優先收　和 (b) 與傳送節點有最小傳輸時間的節點優先收，最稀有的片段優先傳。模擬結果顯示我們提出的演算法在異質網路下較最稀有的片段優先演算法效能佳。

Without considering the controversial issue such as copyright, file sharing is the most popular application in a Peer-to-Peer (P2P) network. Piece-based file sharing is an intuitive way to speed up the sharing process in a P2P network, such as the BT P2P network, and Rarest Piece First (RPF) is the most common way to distribute file pieces. As heterogeneous networks have been fast developing, the transmission conditions among nodes therefore become diversified. In the past, few studies had ever been made about how to more efficiently distribute the file pieces based on the transmission conditions among nodes. In the study, we propose two improved algorithms - (a) RPF with a Shortest Transmission Time (STT) requesting node first and (b) A STT requesting node first with RPF to solve this problem. The simulation results show that our proposed schemes can perform better than RPF in a heterogeneous network environment.

[1] P. Rodriguez, and E.W. Biersack, “Dynamic Pallel Access to Replicated Content in the Internet,” IEEE/ACM transactions on Networking, Vol. 10, No. 4, pp.455-465, August 2002
[2] Napster. http://www.napster.com/
[3] Gnutella. http://www.gnutella.com/
[4] eMule. http://www.emule-project.net/
[5] BitTorrent . http://www.bittorrent.com/
[6] The BitTorrent Protocol Specification, v1.0, 2004, Available at: http://wiki.theory.org/index.php/BitTorrentSpecification
[7] EContentMag.com, “Chasing the user: The recenue streams of 2006, ” [Online], http://www.econtentmag.com/Articles/ArticleReader.aspx?ArticleID=14532, 2005
[8] Fedora Project. http://torrent.fedoraproject.org/
[9] M. Izal, G. Urvoy-Keller, E.W. Biersack, P.A. Felber, A.Al Hamra, and L. Garces-Erice, “Dissecting BitTorrent: Five Months in a Torrent’s Lifetime, ” in Springer Berlin / Heidelberg,2004
[10] Dongyu Qiu and R. Srikant, “Modeling and Performance Analysis of BitTorrent-Like Peer-to-Peer Networks, ” in ACM SIGGOMM, August 2004
[11] Yatin chawathe, Sylvia Ratnasamy, Lee Breslau, Nick Lanham and Scott Shenker, “Making gnutella-like P2P systems scalable,” in ACM SIGCOMM, August 2003
[12] Qin Lv, Pei Cao, Edith Cohen, Kai Li and Scott Shenker, “Search and Replication in Unstructured Peer-to-Peer Networks,” in ACM ICS, June 2002
[13] Ananth Rao, Karthik Lakshminarayanan, Sonesh Surana, Richard Karp and Ion Stoica, “Load Balancing in Structured P2P system,” In Proceedings of the 2nd International Workshop on Peer-to-Peer Systems, Feb. 2003
[14] Zhiyong Xu, Dan Stefanescu, Honggang Zhang, Laxmi Bhuyan and Jizhong Han, “PROD: Relayed File Retrieving in Overlay Networks,” in IEEE IPDPS, April 2008
[15] J. S. K. Chan, V. O. K. Li, and K. S. Lui, “Scheduling algorithms for peer-to-peer collaborative file distribution,” in Proc. Int’l Conf. on Collaborative Computing: Networking, Applications and Worksharing (CollaborateCom), Dec. 2005.
[16] T. H. Cormen, C. E. Leiserson, R. L. Rivest, and C. Stein, Introduction to Algorithms, 2nd ed. Cambridge, MA: MIT Press, 2001 .
[17] J. S. K. Chan, V. O. K. Li, and K. S. Lui, “Performance Comparison of Scheduling Algorithms for Peer-to-Peer Collaborative File Distribution,” in IEEE Journal on Selected Areas in Communications, vol. 25, NO. 1, January 2007, pp.146-154
[18] M.-H. Huang and J.-S. Leu, ”A Study on Piece-based File Sharing in a Peer-to-Peer Network”, The Fourth Workshop on Wireless Ad Hoc and Sensor Networks (WASN'08), Tainan, Taiwan, Sep. 4-5, 2008
[19] P.B. B, C.S. Raghavendra, and V.K. Prasanna, “Efficient Collective Communication in Distributed Heterogeneous Systems,” Proc. International Conf. on Distributed Computing Systems, pp. 15-24, June 1999
[20] Yuh-Ming Chiu and Do Young Eun, “Minimizing File Downlad Time in Stochastic Peer-to-Peer Networks,” in IEEE/ACM transactions on networking, vol.16, NO.2, April 2008
[21] J.-S. Leu and M.-H. Huang, "Piece-based File Sharing over a Peer-to-Peer Network in a Heterogeneous Network Environment", The 13th IEEE International Symposium on Consumer Electronics (IEEE ISCE 2009), pp.881-884, May 2009.
[22] S. Chen, Z Zhang, S. Chen, B. Shi, “Efficient File Search in non-DHT P2P Networks,” Computer Communication, Feb. 2008