防火墙

Primarily, the thesis assays the condition of network framework, the network was divided into three levels in terms of network management in order to establish the distributed method ,and still pointing out the intention and denotation of studying the Topology Discovery.Next, the thesis analyzes SNMP protocol minutely, including its development, principle, and the Network Management system that established on the SNMP protocol. Have analysed MIB in detail and the application way of MIB in network management .The thesis also assays the ICMP protocol, describing its working principle and the format of datagram minutely , and describing two important tools of ICMP- Ping and TraceRoute in detail. On the base of upper analysis, the thesis expounds a kind of distributed Topology Discovery project, and book it in one autonomy system. Topology Discovery was divided into two levels in terms of network management, and analyses the way of linking up between the two level. The thesis minutely assays Router-Level Topology Discovery technology basing on SNMP and Subnet-Level Topology Discovery technology basing on ARP and ICMP. According to these analyses, the thesis explores the specific methodology and the technology of XML data object which using the WinSNMP API to achieve topology discovering system on the development platform of Visual C++, and also analyses the technology of topology analysis and topology graph minutely. Moreover, the thesis assays the technology of basic firewall and Topology Discovery response strategy. Finally, the thesis analyses the underlying blind problem of the topology finding, and also analyses the reason that the blind problem produced and the way that reduced. The distributed algorithm that this paper puts forward has a certain directive significance in wireless network or other fields.

本文首先分析了网络结构状况，将网络从网络管理的角度划分为三个层次，为分布式的方法奠定了基础，同时还指出拓扑发现研究的目的及意义；接着本文分析了SNMP协议，详细分析了SNMP协议的发展状况，协议的工作原理，以及由SNMP协议基础上建立的SNMP网络管理体系，详细分析了MIB，以及MIB在网络管理上的应用方式；本文又分析了ICMP协议，详细描述了ICMP的工作原理和数据报格式，并详细描述了ICMP的两个重要工具-Ping 和TraceRoute；然后本文在结合上述分析的基础上，提出了一种分布式的拓扑发现方案，将拓扑发现拟订在一个自治系统内，将拓扑发现从网络管理角度划分为路由器级和子网级两个层次，分析了两个层次之间的衔接方式，同时从拓扑地域的角度将拓扑发现过程分布化，分析了分布式算法的具体方法和分布式结点之间的数据通讯方法，本文详细分析了基于SNMP的路由器级拓扑发现技术和基于ARP和ICMP的子网级拓扑发现技术；根据这些分析，本文利用XML数据对象作为分布式算法中的数据对象，分析了XML的技术，本文使用Visual C++开发平台实现网络拓扑发现系统，详细分析了使用WinSNMP API实现基于SNMP的路由器级拓扑发现和基于ARP的子网级拓扑发现，分析了使用Winsock编程实现基于ICMP的子网级拓扑发现，本文还对拓扑分析和拓扑图的绘制技术作了较细致的分析；本文最后还分析了基本防火墙技术，分析了几种类型的防火墙对拓扑发现带来的影响，以及在拓扑发现时的应对策略，本文还分析了拓扑发现中可能产生的盲点问题，分析了盲点产生的原因以及拓扑发现中减少盲点的方法。

The network machines can distinguish untrusty interface connected to terminal host or firewall from trusty interface connected to DHCP server or other switcher, which works like a firewall between untrusty host and DHCP server.

DHCP窥探就像是非信任的主机和DHCP服务器之间的防火墙，客户端或者防火墙连接在非信任端口，DHCP服务器或者其他交换机连接在信任端口。

In the thesis, the topology and management model of the hierarchical firewall system are respectively presented, moreover, the system is compartmentalized into modules according to different function.

本文研究了分级防火墙系统解决方案，给出了分级防火墙系统的拓扑结构模型及管理结构模型，并对系统的功能模块进行划分。

Among all kinds of firewall technology, packets filtrating firewall has the characteristic of high speed and high security.

在现有各种防火墙技术中，包过滤防火墙具有速度快、安全性较高等优点。

A firewall helps to prevent the nasties from getting into your computer, and should some get in, the firewall will get in the way of them sending your personal information back out.

防火墙有助于防止nasties进入您的计算机上，并应得到的一些，防火墙会在他们的方式发送您的个人信息回来。

This is a firewall source code for research firewall prawns and live a reference value.

这是一个防火墙的源代码，对于研究防火墙的大虾们来说有参考价值。

This is a firewall source code for research firewall prawns a...

这是一个防火墙的源代码，对于研究防火墙的大虾们来说有参考价值。

Today was Updated the stable version of free personal fire wall comodo firewall pro from company comodo.

今天是最新的稳定版本的免费个人防火墙comodo防火墙亲从公司

Today was released the preliminary version of the personal fire wall comodo firewall pro from company comodo.

今天发表的初步版本的个人防火墙comodo防火墙comodo公司从亲。

Status of preliminary version reached the development of personal fire wall comodo firewall pro from company comodo.

地位的初步版本达成的发展，个人防火墙克魔岛防火墙亲从公司的克魔岛。

We have no common name for a mime of Sophron or Xenarchus and a Socratic Conversation; and we should still be without one even if the imitation in the two instances were in trimeters or elegiacs or some other kind of verse--though it is the way with people to tack on 'poet' to the name of a metre, and talk of elegiac-poets and epic-poets, thinking that they call them poets not by reason of the imitative nature of their work, but indiscriminately by reason of the metre they write in.

索夫农 、森那库斯和苏格拉底式的对话采用的模仿没有一个公共的名称；三音步诗、挽歌体或其他类型的诗的模仿也没有——人们把&诗人&这一名词和格律名称结合到一起，称之为挽歌体诗人或者史诗诗人，他们被称为诗人，似乎只是因为遵守格律写作，而非他们作品的模仿本质。

The relationship between communicative competence and grammar teaching should be that of the ends and the means.

交际能力和语法的关系应该是目标与途径的关系。