基于Tit-for-Tat的BitTorrent网络经济模型

摘要 针对BitTorrent网络中节点的“搭便车”行为会严重影响正常节点的下载进度以及整个网络性能的问题，提出了一种基于“以牙还牙”机制的经济模型.类比于现实社会的商品交易以及信用体系，在考虑了节点的上传下载行为的周期性表现以及文件块在节点中的动态分布状况后，设计了由节点财富值、文件块的定价以及节点透支额度组成的BitTorrent经济模型；并将该经济模型应用到“以牙还牙”机制中.在提出的经济模型中，节点间的资源传播作为一种交易，在未达到透支额度条件下节点按照文件块的定价进行交易，从而使得节点的财富值发生变化.仿真实验结果表明:在相似的资源传播速度下，该经济模型对free-rider节点的屏蔽效果要明显优于单纯的“以牙还牙”机制.
Abstract：To solve the problem that the free-riding behavior of a node will seriously affect the download progress of the common node and the whole network performance in the BT network， a new economic model (TTEM) was proposed based on the tit-for-tat mechanism. According to the commodity trading and credit system in the social life， the economic model was presented that consisted of the node wealth， the file blocks pricing and the node overdraft. Finally， the TTEM was proposed by deploying the economic model on the tit-for-tat. Resources spread between nodes as a transaction in TTEM. Nodes were traded by the price of the file blocks， making the wealth of the node change， if the node’s wealth is greater than the overdraft. The simulation results show TTEM is able to reduce the impact which the free-rider nodes make on the BT network than the pure tit-for-tat mechanism under the similar propagation velocity of the file resources.