摘 要当今，我们处在一个网络信息爆炸时代，信息技术迅猛发展，P2P(Peer-to-Peer)技术也不断地引发越来越多业内人士关注与研究,基于P2P网络技术的应用也迅速发展起来，在互联网用户中引起了极大的反响。它以其特有的自组织性、扩散性，成为互联网不可缺少的部分。86058

起初，以BT、Emule等P2P下载软件，在原有的网络下载技术的上有了很大创新与改进。Internet产生的一个主动力是资源共享，而P2P的应用很好的做到了这一点，这也成为P2P迅猛发展的一个很大的原因。P2P技术改变了整个因特网模式的思想，给我们的生活带来了很多的方便与思考。其在对等计算、协同工作、搜索引擎、文件共享等多个领域得到应用。

本文致力研究基于OverSim的P2P通信仿真系统的设计。Oversim是一种基于离散仿真系统仿真框架OMNET++的开源覆盖网络。这个框架克服了现有P2P模拟器的一些缺陷,它被认为是最有力的工具之一的研究。在所有可用的工具中我们选择OverSim是因为它的灵活性:其模块化设计和通用的API的使用促进了与新协议的扩展。此外,其灵活的底层网络计划在应用程序开发中非常有用。本文设计的系统用BitTorrent协议模拟在P2P系统中常见的文件分享功能，采用P2P典型的结构化模型。用户peer若要请求下载文件，首先到Tracker服务器查找到该文件的种子文件，Traker回复Peer的下载请求，回应相应的下载信息。本文开始给出了关于P2P的一些基础性描述，紧接着介绍了仿真平台的相关技术，最后对系统进行整体设计与仿真。

毕业论文关键词：P2P；OverSim；仿真平台；文件分享；算法验证

Abstract Today, we are in a network information explosion era, the rapid development of information technology, P2P (Peer - to - Peer) technology is also constantly caused more and more attention the personage inside course of study and research, based on the application of P2P network technology also developed rapidly, has caused great repercussions in the Internet users。It by its unique self-organizing, diffusivity, become an indispensable part of the Internet。

    At first, such as BT, Emule P2P download software, on the original network download technology has made great innovation and improvement。The Internet is a main power resource sharing, and P2P applications very well done this in the past, this has become a big reason for the P2P software's rapid development。P2P technology has changed the thought of the Internet model, brought a lot of convenience to our life and thinking。In peer-to-peer computing, collaborative work, search engines, file sharing, and other fields has been applied。

    This article dedicated to the research of P2P communication simulation system based on OverSim design。Oversim is an open source based on discrete simulation system simulation framework OMNET++ overlay network。This framework overcomes some defects of existing P2P simulator, it is considered to be one of the most powerful tool to study。In all of the available tools we choose OverSim because of its flexibility: the modular design and the use of a common API for promote with the expansion of the New Deal。In addition, its underlying network plan is flexible in application development is very useful。System designed in this paper using BitTorrent protocol simulation in P2P system common file sharing features, typical structural model using P2P。If user peer download file to request, first of all to the Tracker server lookup to seed file, the file Traker reply peer download request, respond to the corresponding download information。Beginning, the paper puts forward some basic description about P2P, and then introduces the relevant technology of the simulation platform, finally, the simulation system for the overall design。System research based on the P2P BT protocol, only does not take into account more scenes。