中文摘要：

针对局域内网单台计算机下载外网资源速度慢的问题,本文以Petri网为系统逻辑设计工具,提出一种基于P2P（Peer to Peer）分布式结构的外网带宽共享协议。该协议指定内网多台计算机在外网下载所需文件的不同片段,再由局域内网传输给任务发起者所属计算机进行原文件整合。协议充分利用多台计算机的并行下载能力以及局域内网的快速传输能力,从逻辑层面提高了单台计算机的下行带宽。本文进一步通过基于Petri网的可达标志图,S_不变量和流程图方法对协议的逻辑正确性和行为许可性进行了验证。

英文摘要：

Downloading resources by a computer usually suffers slow download speed in local area network.Petri nets are suitable for logic programming of a target system. Hence,this study proposes an outer net bandwidth sharing protocol with a kind of distributed structures based on Petri nets. This protocol defines a valid file download calculation process. First,the computers in the intranet are specified by the protocol to download the differentiable fragments of an object file. Then,these fragments are sent to the computer of the originator,which completes final file integration. The protocol makes full use of the abilities of the parallel downloads for multiple computers and the fast data transmission capacity in the intranet. The proposed method expands the downlink bandwidth of a single computer at the logic level. Finally,logical correctness and behavior availability of the protocol are checked by using reachability graph,S_ invariant,and flow diagram of Petri nets.