一、应用背景 在构建计算机网络系统时,经常会碰到这样一些实例: 驻外办事机构与总部连网 不在同一物理空间的小型工作组之间连网 多台客户机共享一个Internet接口 不在同一网段上的客户机的相互通信问题等 对上述连网的实现,直观的操作就是投入一些资金租用专用通道,购买专用网络设备。然而,这对于小公司、小单位在经费上可能会有困难,小规模的应用在资源上可能造成浪费。并且,随着工作业务 First, the application background In the construction of computer network systems, often encounter such examples: foreign offices and headquarters networking is not in the same physical space between a small workgroup networked multiple clients to share an Internet interface is not on the same network Section of the client’s mutual communication problems such as the realization of the above networking, intuitive operation is to invest some dedicated channels of capital leased to buy a dedicated network equipment. However, this may be difficult for small companies and small units in terms of funding. Small-scale applications may result in waste of resources. And, with the work business