Contents. Network Topology. Common Network Topology. Chain Network. Protection Mode. Ring with Chain Network, страница 8

Figure 2-21 Active service flow between ring and chain (A¨E)

Table 2-9 Service flow between NE A and NE E and the configuration of NE D

If the fiber between NE A and NE B breaks, the service from NE E to NE A does not need to be switched; while the service from NE A to NE E will select the standby route, as shown in Figure 2-22.

Figure 2-22 Protection switching of service between ring and chain

If the active route connecting NE D and NE E is faulty, the service on the chain or the service transmitted over the ring and chain will switch to the standby route automatically.

n  Typical NE configuration

This section introduces two special NEs: A and D.

NE A configures two SL16 boards for east and west lines respectively and configures three PQ1 boards to add/drop 4 x 32 x E1 services. Figure 2-23 shows the typical NE configuration.

Figure 2-23 Board configuration of NE A

NE D needs two groups of STM-16 optical interfaces to form an STM-16 ring, and two groups of STM-16 optical interface to form an STM-16 linear chain that needs 1+1 protection, so NE D is configured with four SL16 boards. NE D also configures a PQ1 board and a PL3 board to add/drop 32 x E1 and 3 x E3 services. Figure 2-24 shows the typical NE configuration.

Figure 2-24 Board configuration of NE D

2.5  Other Topologies

The OptiX OSN 3500 can be deployed in various complex networks, such as tangent rings, intersecting rings, two-ring with chain, DNI, HUB network, and mesh network.

Except HUB network and mesh network, the rest network topologies are also the combination of rings or chains and their protection modes are the same as what we have mentioned in section 2.4  “Ring with Chain Network”.

Usually, each HUB network has a central node, which serves to transfer and route the service between any two nodes except itself. Here, the central node can manage the bandwidth resource flexibly to economize the investment and operating cost. However, this central node is the bottleneck of the whole network and its failure may result in the network crash.

In the mesh network, each node connects to others through direct routes, so it has no bottleneck problem. If the equipment fails, the service can be assured by alternative route. There are several routes available between two nodes, which improve the reliability of service transmission. The mesh network is applicable to areas of heavy traffic. Nevertheless, the network is complicated and hard to manage. The cost is quite high as well.