翻译TCP/IP-仅供爱好者学习

        原文取自http://www.mamiyami.com/document/oreilly/books/tcpip/tcpip/index.htm，要转载请注明出处。

1.总览TCP/IP

      所有使用UNIX操作系统的用户，比如工程师，教师，科学家或者是做生意的，他们这时就有了第二个

职业——UNIX系统的系统管理员，如果这些电脑可以上网，那他们同时又是网络管理员。

     网络管理员和系统管理员是两种截然不同的工作。系统管理员的工作包含给系统新另一个用户，给单独的一台计算机做备份。这和网络管理员是不同的。一旦你把你的计算机放在网络之中，你的计算机将和网络中其他计算机存在一定的联系。作为一个网络管理员，你的工作就不仅仅会影响你自己的计算机，而会对网络中所有的计算机产生影响。套用一句话，就是网络管理员会影响网络中每一强计算机。

     身在网络中的计算机使自己的交流能力大大加强-并且，大部分计算机是用来交流而只有一少部分是用来计算的。许多大型机和超级计算机是用作商业或是科学计算使用，但是比起用作收发邮件的电子计算机的数量，就少得很多。而且，当你看到上万的计算机用作交流思想，显而易见，为什么计算机会被当作是交流的设备。

     计算机通信的积极的影响随着加入网络的计算机的数量的增加而增大。TCP/IP协议的最大优势在于，它能够使用不同的硬件和不同的操作系统的计算机通信。

    这本书通过实践，一步一步指导我们在UNIX操作系统上配置和管理TCP/IP软件，TCP/IP协议支配UNIX操作系统上的数据通信，它从底层支持UNIX操作系统的局域网，企业网，万维网上的通信软件。

      TCP/IP协议属于两大数据传输协议。主要由以下两个数据传输协议组成，一是传输控制协议，另一个是因特网协议。当然TCP/IP协议还包含其他别的协议。但是TCP协议和IP协议是它的主要组成部分。

     本书的第一部分讨论TCP/IP协议的基础以及它如何在网络里传递数据。第二部分我们将解释如何配置和运行在UNIX操作系统上的。现在，我们从一个小故事开始讲起。

     在1969年，

In 1969 the Advanced Research Projects Agency (ARPA) funded a research and development project to create an experimental packet-switching network. This network, called the ARPANET, was built to study techniques for providing robust, reliable, vendor-independent data communications. Many techniques of modern data communications were developed in the ARPANET.

The experimental ARPANET was so successful that many of the organizations attached to it began to use it for daily data communications. In 1975 the ARPANET was converted from an experimental network to an operational network, and the responsibility for administering the network was given to the Defense Communications Agency (DCA). [1] However, development of the ARPANET did not stop just because it was being used as an operational network; the basic TCP/IP protocols were developed after the ARPANET was operational.

[1] DCA has since changed its name to Defense Information Systems Agency (DISA).

The TCP/IP protocols were adopted as Military Standards (MIL STD) in 1983, and all hosts connected to the network were required to convert to the new protocols. To ease this conversion, DARPA [2] funded Bolt, Beranek, and Newman (BBN) to implement TCP/IP in Berkeley (BSD) UNIX. Thus began the marriage of UNIX and TCP/IP.

[2] During the 1980s and early 1990s, ARPA, which is part of the U.S. Department of Defense, was named Defense Advanced Research Projects Agency (DARPA). Currently known as ARPA, the agency is again preparing to change its name to DARPA. Whether it is known as ARPA or DARPA, the agency and its mission of funding advanced research has remained the same.

About the time that TCP/IP was adopted as a standard, the term Internet came into common usage. In 1983, the old ARPANET was divided into MILNET, the unclassified part of the Defense Data Network (DDN), and a new, smaller ARPANET. "Internet" was used to refer to the entire network: MILNET plus ARPANET.