In addition, the transport layer allows IMS devices to make and receive calls to and from the PSTN network or other circuit-switched networks via the PSTN gateway.

此外，传输层允许IMS设备通过PSTN网关呼叫PSTN网络或其他电路交换网络和接收来自这些网络的呼叫。

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If this is the case the circuit manager may wish to filter out datagrams for the appropriate network layer if only one of the applications is affected.

在这种情况时，链路管理器可能为特定的网络层过滤数据包，而只使一个程序受影响。

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