Typically, permanent virtual circuits are set up between multiple backbone switches and between switches and devices with heavy network traffic.

一般而言，永久性虚拟电路建在多个主干网交换机之间和交换机与网络信息流量大的设备之间。

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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.

CNN: Networking trends emerge for '99