近年来，随着网络的迅猛发展，网络安全问题变得越来越突出。如何保障网络的安全，如何制定网络的安全策略日益成为安全领域研究的热点。

本文从协议工程的角度出发，首先分析了产生网络安全问题的各种因素，然后介绍了许多人如何利用协议漏洞破坏网络安全，并提出了从协议方面维护网络安全。

在文章中接着介绍了Petri网的研究概况，指出利用Petri网进行通信协议的描述和验证的优越性。随后，在Petri网基本概念和相关性质的基础上，对停一等协议建立了Petri网模型，得到相关结论。

在第四章从IPSec的体系、IPSec的三个基本协议和安全策略的管理三个方面对IPSec协议进行了深入的研究和探讨。

从这篇论文中我们可以意识到网络通信安全协议的重要性，还可以初步了解如何去分析研究协议。

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abstract

The network security is more important as the network's development rapidly.How to ensure the security of the network and how to make the policy of the network security is the hotspot of the security study.

For the view of protocol engineering, this paper analysese the kinds of the factor which produce the problem of the network security .Then we introduced that many people attack the network security by the fault of protocol,and bring the motheds protect the network security from protocols.

In this paper, we introduced the research survey in Petri nets . This shows the advantage of using Petri nets to describe and verify communicating protocols. Soon afterwards we construct the model of stop-and-wait protocol with the tool of automatic machine and Petri nets.

At the fouth chapter of this paper introduces the IPsec protocol in great details including the following three aspects of  the system of IPSec protocol,the basic protocols of IPSec and SP (Security Policy) management.

We can know the importance of network security,and learn how to analysize the protocols.

Keywords:  network security, Petri nets, Stop-and-wait protocol, IPSec