The ODUk SNCP protection uses the dual fed and selective receiving function of the cross-connections at the electrical layer to protect the line board and OCh fiber. The granularity is ODU0, ODU1, ODU2, ODU3 or DOUflex services.
Trigger Conditions
ODUk SNCP is classified into three types: SNC/I, SNC/N, and SNC/S. The difference among the three types lies in that they have different monitoring abilities and thus have different trigger conditions.
The trigger conditions for the SNC/I protection automatic switching are as follows:
NOTE:
- The board is offline, including the following situations: Removing or cold resetting the board.
- There is a signal failure (SF) condition. SF includes the following board-side alarms: LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, ODU-AIS, ODU-LCK, ODU-OCI, OTU-TIM, ODU-TIM, ODU-TCM-TIM.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC.
NOTE: - Only when the Enable TIM Response of the NS2, ND2, NQ2 or NS3 configured with protection is set to Enabled, the OTU-TIM, ODU-TIM, ODU-TCM-TIM are valid.
The trigger conditions for the SNC/N protection automatic switching are as follows: NOTE:
- The board is offline, including the following situations: Removing or cold resetting the board.
- There is a signal failure (SF) condition. SF includes the following board-side alarms: LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, ODU-AIS, ODU-LCK, ODU-OCI, ODU-LOFLOM, ODU-TCM-OCI, ODU-TCM-LCK, ODU-TCM-AIS, OTU-TIM, ODU-TIM, ODU-TCM-TIM, ODU-TCM-LTC.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC, ODU-TCM-DEG, ODU-TCM-EXC.
NOTE: - Only when the Non-Intrusive Monitoring of the OTU configured with protection is set to Enabled, the ODU-AIS, ODU-LCK, ODU-OCI, ODU-DEG, ODU-EXC are valid.
- If the protection of TCM layer is required, and the Sink Mode of the TCM overheads on the corresponding layer of the proper channel is set to TRAN, the ODU-TCM-OCI, ODU-TCM-LCK, ODU-TCM-AIS is valid.
- Only when Enable TIM Response of the NS2, ND2, NQ2 or NS3 configured with protection is set to Enabled, the OTU-TIM, ODU-TIM, ODU-TCM-TIM are valid.
- If the protection of TCMn layer is required and Enable LTC Response of the TCMn section of ODU1 or ODU2 of the NS2, ND2, NQ2 or NS3 configured with protection is set to Enabled, the ODU-TCM-LTC is valid.
The trigger conditions for the SNC/S protection automatic switching are as follows: NOTE:
- The board is offline, including the following situations: Removing or cold resetting the board.
- There is a signal failure (SF) condition. SF includes the following board-side alarms: LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, ODU-AIS, ODU-LCK, ODU-OCI, ODU-TCM-OCI, ODU-TCM-LCK, ODU-TCM-AIS, ODU-TCM-TIM, ODU-TCM-LTC, OTU-TIM, ODU-TIM.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: OTU-DEG, OTU-EXC, ODU-DEG, ODU-EXC, ODU-TCM-DEG, ODU-TCM-EXC.
NOTE: - If the protection of TCM layer is required, and the Sink Mode of the TCM overheads on the corresponding layer of the proper channel is set to OPER, ODU-TCM-OCI, ODU-TCM-LCK, ODU-TCM-AIS are valid.
- Only when the Enable TIM Response of the NS2, ND2, NQ2 or NS3 configured with protection is set to Enabled, the OTU-TIM, ODU-TIM, ODU-TCM-TIM are valid.
- If the protection of TCMn layer is required and Enable LTC Response of the TCMn section of ODU1 or ODU2 of the NS2, ND2, NQ2 or NS3 configured with protection is set to Enabled, the ODU-TCM-LTC is valid.
Working Principle
The ODUk SNCP protects inter-subnet services and requires no protocol. The ODUk SNCP provides protection for topologies such as ring with chain, tangent rings, intersecting rings. This ensures high flexibility in application.
ODUk SNCP protection is of ODU1, ODU2 level. Types of SNCP are classified into SNC/I, SNC/N, and SNC/S.
- SNC/I (Inherent monitoring): inherent monitoring; the trigger condition is the state of overheads in the SM section.
- SNC/S (Sub-layer monitoring): sub-layer monitoring; the trigger condition is the state of overheads in the SM and TCM sections.
- SNC/N (Non-intrusive monitoring): non-intrusive monitoring; the trigger condition is the state of overheads in the SM, TCM or PM sections.
Figure 1 shows the principle with the ODUk SNCP as an example.
Figure 1 Working principle of the ODUk SNCP
 : Direction of the working signal flow |
 : Direction of the protection signal flow |
NOTE: - As shown in Figure 1, 1 and 4 are tributary boards or line boards; 2 and 5 are protection line boards; 3 and 6 are working line boards. The OptiX OSN 6800A/8800 T16 (NA)/8800 T32 (NA)/8800 T64 (NA) realizes dual fed and selective receiving by using a centralized cross-connect board, which is not shown in Figure 1. The OptiX OSN 3800A realizes dual fed and selective receiving by using mesh cross-connections.
- The SCC and the line boards communicate through the backplane, which are not shown in Figure 1.
- In the transmit direction, the client services to be protected are input through the tributary board. They are split into working signals and protection signals after passing through the XCS board or mesh cross-connections. The working signals and the protection signals are respectively transmitted in the working channel and the protection channel.
- In the receiving direction, in normal cases, only the cross-connection corresponding to the working line board is enabled and that to the protection line board is disconnected. When the working channel is faulty, the cross-connection corresponding to the working line board is disconnected and that to the protection line board is enabled. The service signals are transmitted in the protection channel.
- After the working channel returns to normal, the service signals can be switched back to the cross-connection corresponding to the given line board according to the existing configuration in the NMS.