一、基本情况和基本选择1.形势和目标从全球来看,固定电信网逐渐走向下一代网(NGN)已呈不可逆转之势。然而时至今日,NGN并没有一个统一的定义、标准的架构及人人都可以接受的过渡方案和运营方案;加之各国、各地区、各运营商的网络水平、运营状况和所追求目标千差万别,因此,关于 I. Basic Information and Basic Options 1. Situation and Objectives From a global point of view, the fixed telecommunications network has gradually moved toward the next generation network (NGN) and has shown an irreversible trend. However, up till now, NGN does not have a unified definition, a standard architecture and a transition plan and operation plan acceptable to all. In addition, the network level, operation status and goals pursued by countries, regions and operators vary widely, So, about