The VLAN SNCP protection utilizes the dual fed and selective receiving function of the Layer 2 module to protect the line board and OCh fiber. The granularity is on client-side port service level indicated with VLAN.
Trigger Conditions
The trigger conditions for the VLAN SNCP automatic switching are as follows:
Abnormal line status is detected, which can be confirmed when no OAM frame is received in a period (currently 100 ms). The following alarms may occur on the board: LOS, LOF, AIS-L, OTU-LOF, OTU-AIS, OTU-LOM.
Working Principle
The VLAN SNCP protects inter-subnet services and requires no protocol. The VLAN SNCP provides protection for topologies such as ring with chain, tangent rings, intersecting rings. This ensures high flexibility in application.
The principle of VLAN SNCP protection is similar to that of SW SNCP protection. The difference lies in that the VLAN SNCP monitors Layer 2 electrical layer while SW SNCP monitors Layer 1 electrical layer.Figure 1 shows the principle with the VLAN SNCP as an example.
NOTICE: The client-side 1+1 protection and VLAN SNCP cannot be configured at the same time for the 11LEX4, 11LEM24, L4G and the TBE board.
 : Direction of the working signal flow |
 : Direction of the protection signal flow |
NOTE: - As shown in Figure 1, 2 and 4 stand for the working OTU; 1 and 3 stand for the protection OTU. The working and protection links realize dual fed and selective receiving by using the Layer 2 module.
- The SCC board communicates with OTU through the backplane. This communication is not indicated in Figure 1.
- In the transmit direction, the client services to be protected are input through OTU2. Then, the client services are duplicated and transmitted into two links: the working link and protection link. The protection services are cross-connected to OTU1 through OTU2. The working signals and protection signals are transmitted over the working and protection channels respectively.
- In the receiving direction, the signals from the working link on OTU4 are selected during normal operation. When the working channel works abnormally, the signals from the protection link on OTU4 are selected.
- After the working channel resumes normal operation, the service signals can be switched back to the link on the specified OTU according to the revertive mode preconfigured on the U2000 Web LCT.