This section describes the application of the VLAN SNCP.
Figure 1 shows engineering project T which is a ring network by station A, B, C, and D. Station A, B, C, and D are OADM stations. Service b between station A and station B adopts VLAN SNCP protection realized by dual fed and selective receiving.
 : Direction of the working signal flow |
 : Direction of the protection signal flow |
As shown in Figure 1, during normal operation, client service b at the transmitting end is input through OTU2 and then 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. At the receiving end, the signals from the link on OTU4 are selected.
| : Direction of the working signal flow |
: Direction of the protection signal flow |
As shown in Figure 2, when the working channel is abnormal, at the transmitting end, client service b is transmitted over the protection link on OTU2. The protection service is then cross-connected to OTU1 and transmitted over the protection channel; at the receiving end, the service on OTU3 is cross-connected to OTU4 and the signals from the protection link on OTU4 are selected.