A layer-3 switch is a switch that can perform routing functions.

三层交换机是可执行路由功能的交换机。

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Layer 3: Services layer.

层3：服务层。

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IP, located one layer down, at the OSI network layer, or layer 3, communicates the addresses of each packet's sender and receiver to the routers along the way.

IP位于下一层，在OSI的网络层，即第三层，把每个包的发送者和接收者地址告诉一路上各个路由器。

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As we learned when the console was initially announced, the Wii U's "proprietary high-density optical discs" hold up to 25GB of data -- equivalent with that of Sony's single-layer Blu-ray format on the PlayStation 3, and much larger than the Xbox 360's dual-layer DVD format.

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Switches with built-in routing, also known as Layer 3 switches, are expected to catch on as router replacements once the boxes are equipped with WAN interfaces and support for multiple protocols -- two features backbone routers have long had.

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Existing 3-D printers, also called rapid prototyping machines, build structures layer by layer.

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