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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However, the concern is that voice traffic in frame environments built with permanent virtual circuits (PVC) will not be as cost-effective as frame nets built with switched virtual circuits (SVC).

但问题是，用永久虚拟电路(PVC)建立起来的帧环境中的话音通信的性能价格比不如用交换虚拟电路(SVC)建立起来的帧网络。

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