因特网由三个层次组成：骨干网，中间层次网和子网络。

The Internet is a three level hierarchy composed of backbone networks, mid-level networks, and stub networks.

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从某种不怎么被承认的层次上说，万维网的受众，无论怎样衡量，都不过是骗子。

At some never-quite-admitted level, the Web audience, however measurable, is nevertheless a fraud.

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网元管理是层次化管理系统的基础。但是，目前通用的网络管理系统缺少对网元管理的支持。

Network element management is the foundation of layered management, but current network management systems are lack of supports to element management.

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