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Guidelines for Configuring LOS Detection

Keep the following points in mind when you configure the capability to detect LOS conditions on T1E1 interfaces:

  • A cable disconnection of a serial port cannot be detected when no external clock is being used by the port. The following clock configurations use an external clock:

    • DCE/DTE: Cfg Rate – Ext Clk

    • DCE/DTE: All Clock – Ext Clk

    • DCE/DTE: Adap Rate – Ext Clk

    • DCE/DTE: Auto Rate – Ext Clk

    • DTE: All clocked by Ext Clk (ST/RT)

    • DTE: All clocked by User Clk (RT)

    • Any custom clock config that uses “TT”

  • For any other serial clock configuration, a cable removal on the online port does not cause it to exit the running state.

  • For T1/E1 ports, the recovered clock (which is equivalent to the external clock of a serial port) from the incoming T1/E1 AMI signal is used in all available T1/E1 preconfigured or canned clock configurations.

  • The T1 LOS checking technique was primarily intended for CTP bundles. Because the T1/E1 SAToP bundle state machine also supports the bundle EVAL state as part of its bundle state machine, it can also benefit from the LOS checking functionality provided by this feature. However, the LOS detection feature on SAToP bundles is not useful for both ended redundancy, since both-ended Y-cable redundancy configurations only supports CTP bundles.

  • CESoPSN and VCOMP bundles are not supported for detecting LOS conditions because their bundle state machines do not support an EVAL state.

  • You can configure the LOS detection mechanism for T1/E1 ports in the same function that checks the external input clock. In addition, this T1/E1 LOS detection capability is processed under the control of a separate port configuration flag so that this LOS checking occurs only when this flag is active. Although this menu option to enable or disable the LOS detection functionality is shown regardless of the port type, such as serial interfaces or T1E1 interfaces, this setting becomes effective on a T1/E1 port only when it is connected to a CTP or SAToP bundle. If the LOS detection functionality is enabled on a serial port or other bundle types, the setting is not processed.

  • Also, when you run the bundle query for CTP bundles and SAToP bundles, the T1E1 port type displays port configuration flags that are relevant to a T1E1 port. In the PortConfigFlags field displayed in the output of the bundle query, T1LoSCheck denotes that LOS detection is specified on a T1 port connected to a CTP bundle or a SAToP bundle, E1LoSCheck denotes that LOS detection is specified on a E1 port connected to a CTP bundle or a SAToP bundle, and the NoRdReclk flag signifies that the redundancy receiving (RX) clock is disabled. The NoRdReclk flag is also displayed because this flag is default enabled for a T1/E1 port, whereas it is usually not enabled for a serial port.