一、Internet的结构 Internet不是一种新的物理网络,而是将多个物理网络互联起来的一种方法和使用络的一套规则。Internet实际上是一个“网络的网络”,它将位于不同地区、不同环境的网络互连成为一个整体。 物理上,两个网络只能通过一个分别连在两个网络上的主机连接起来。但仅仅物理连接并不能提供我们所需要的网络互连,因为这样的连接并不能保证这台主机与其它需要进行通信的主机能够协凋工作。为了能容纳不同的网络环境,需要一台能够将报文分组从一个网络转变到另一个网络上的主机。我们将这种连接两个网络并将报文分组从一个网络传到另一个网络 First, the structure of the Internet The Internet is not a new kind of physical network, but a way to interconnect multiple physical networks and use a set of rules. Internet is actually a “network of the network”, it will be located in different regions, different environments interconnect the network as a whole. Physically, the two networks can only be connected by a single host connected to both networks. But just a physical connection does not provide the network interconnection we need because this connection does not guarantee that this host will work with other hosts that need to communicate. In order to accommodate different network environments, a host that can switch packets from one network to another is needed. We will connect this two networks and packet packets from one network to another network