When devices are emulated, such as virtual network adapters, the emulation provides a layer to abstract away the physical hardware.

当设备被模拟(比如虚拟网络适配器)时，模拟提供一个抽象层以抽象物理硬件。

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The link layer refers to the device drivers providing access to the physical layer, which could be numerous mediums, such as serial links or Ethernet devices.

链路层是指提供对物理层访问的设备驱动程序，这可以是各种介质，例如串口链路或以太网设备。

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This caching layer optimizes access to the physical devices by keeping data around for a short time (or speculatively read ahead so that the data is available when needed).

这个缓存层通过将数据保留一段时间(或者随即预先读取数据以便在需要是就可用)优化了对物理设备的访问。

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