Contents. Network Topology. Common Network Topology. Chain Network. Protection Mode. Ring with Chain Network, страница 5

Figure 2-10 Service flow between NE A and NE C (fiber-cut)

n  Typical NE configuration

Here takes NE A as an example to introduce the typical configuration of nodes in an MSP ring.

NE A configures two SL16 for east and west lines respectively and configures three PQ1 to add/drop 3 x 63 x E1 services. Figure 2-11 shows the typical NE configuration.

Figure 2-11 Board configuration of NE A

2.  Four-Fiber Bidirectional MSP Ring

This protection mode is also applicable to a ring network with dispersive services. If the service is only transmitted between adjacent nodes, the service capacity can reach STM-N x K (K is the number of nodes) at most in the ring. A four-fiber ring requires two pairs of optical interfaces boards at each node, and two pairs of optical fibers on the line.

The four-fiber bidirectional MSP ring adopts uniform routing, the same with two-fiber MSP ring. It requires the support of automatic protection switching (APS) protocol and high-level network maintenance.

The four-fiber bidirectional MSP ring supports ring switching and span switching. If both the working path and the protection path between two nodes are faulty, the ring switching is up. If only the working path is faulty, the span switching is up. The span switching is 1:1 linear multiplex section switching between two nodes.

The example below illustrates the configuration of the four-fiber bidirectional MSP ring.

n  Configuration plan

NEs A, B, C and D form a four-fiber bidirectional MSP ring with the line rate being STM-16. The services are dispersive and there are services transmitted between adjacent nodes.

n  Configuration description

The service on the four-fiber bidirectional MSP ring tends to be transmitted over uniform routing, so the bidirectional service should be configured for each direction. For services that are not added/dropped at this station, configure them as bidirectional pass-through services.

Take an E1 service between NE A and NE C as an example. The service occupies #1 VC-4 in the line. As shown in Figure 2-12, the ring corresponding to east 1 and west 1 is the working ring, and the ring corresponding to east 2 and west 2 is the protection ring. You need to configure the service on the working route or the working ring only. The protection ring of the four-fiber ring can carry extra services, however, these services will be lost upon switching.

Normal condition

Figure 2-12 illustrates the service flow in normal conditions: NE A tributary unit—NE A east 1:7-SL16-1—fiber line—NE B west 1:12-SL16-1—NE B east 1:7-SL16-1—NE C west 1:12-SL16-1—NE C tributary unit.

Figure 2-12 Service flow between NE A and NE C (normal)

Ring switching

If both the working and protection fibers between NE A and NE B are broken, the E1 service between A and C will be switched to the protection ring. The service flow from NE A to NE C is shown in Figure 2-13: NE A tributary unit → NE A west 2:13-SL16-1 → NE D east 2:6-SL16-1→ NE D west 2:13-SL16-1 → NE C east 2:6-SL16-1→NE C west 2:13-SL16-1→NE B east 2:6-SL16-1→NE B east1:7-SL16-1→NE C west 1:12-SL16-1→ NE C tributary unit. The service from NE C to NE A is carried on another standby fiber.

Figure 2-13 Service flow between NE A and NE C upon fiber cut (ring switching)

Span switching