The tributary SNCP protection uses the dual fed and selective receiving function of the electrical-lay cross-connections to protection the accessed client services.
Trigger Conditions
The tributary SNCP protection 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: LOF, LOS, LOC, OTU-LOF, OTU-LOM, OTU-AIS, OTU-TIM, ODU-AIS, ODU-LCK, ODU-OCI, ODU-TIM, ODU-TCM-TIM.
- There is a signal degraded (SD) condition. SD includes the following board-side alarms: SF-S, 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, ODU-TCM-LTC, ODU-TCM-TIM, 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: - Only when Non-Intrusive Monitoring of the PM layer of the OTU with protection is set to Enabled, the ODU-AIS, ODU-LCK, ODU-OCI, ODU-DEG, and 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 toTRAN, 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 ODU1_TCMn_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-AIS, ODU-TCM-OCI, ODU-TCM-LCK, ODU-TCM-LTC, ODU-TCM-TIM, 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.
For details of the above alarms, refer to the Alarms and Performance Events Reference.
Working Principle
The tributary SNCP protection protects the client services that are accessed by the tributary board. No protocol is required.
The tributary SNCP protection is of ODU1 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.
The supported protection types vary with the type of the services accessed by the tributary board:
- When the tributary board accesses the OTN services, the SNC/I, SNC/N, and SNC/S are supported.
- When the tributary board accesses the STM-16/OC-48 service or SDH/SONET services of a higher level, only the SNC/I is supported.
Figure 1 shows the principle with the tributary SNCP protection as an example.
Figure 1 Working principle of the tributary SNCP protection
 : Direction of the working signal flow |
 : Direction of the protection signal flow |
NOTE: - In Figure 1, the TQM and NS2 boards are considered as an example to describe the principle of the tributary SNCP protection. The TQM1 is the working tributary board and theTQM2 is the protection tributary board.
- The OptiX OSN 6800A /8800 T16 (NA)/8800 T32 (NA)/8800 T64 (NA) realizes selective receiving by using a centralized cross-connect board, which is not shown in Figure 1. The OptiX OSN 3800A realizes 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 that require protection are input through the OLP/SCS board. The client services are divided into two channels and the two channels of client services are sent to the TQM1 and . Then, the client services are cross-connected to the NS2 to be selective received through the XCS board or MESH cross-connections.
- The cross-connection in the working channel corresponding to the TQM1 takes effect and the cross-connection in the protection channel corresponding to the TQM2 is disabled. The NS2 selects the services from the working channel.
- When the working channel is faulty, the cross-connection in the working channel corresponding to the TQM1 is disabled and the cross-connection in the protection channel corresponding to the TQM2 takes effect. The services are transmitted over the protection channel. The NS2 selects the services from the protection channel.
- In the receiving direction, users need to configure the selective receiving of the service that is sent by the NS2.
- After the working channel is recovered, the services can be switched to the cross-connection of the specified tributary board according to the revertive mode that is preset on the U2000 Web LCT.