The various network device drivers run at the interface layer, which receives and transmits data from and to the physical link.

各种网络设备驱动程序在接口层运行，该层从物理链路接收数据，并向物理链路传输数据。

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Each layer USES the layers beneath it, so the network layer does not need to worry about how each hop on the network USES the physical and data link layers and so forth.

每一层都使用它下面的层，因此网络层不必担心网络上的每次跳转如何使用物理和数据链接等问题。

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Then the data link layer and network layer design schemes of several typical systems are described in detail.

分类阐述了几种典型的数据链路层和网络层的设计方案和设计思想。

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