Specifications

41
Cisco ONS 15327 Product Overview, R3.3
June 2002
Cisco ONS 15327 Product Overview
Network Configurations
Path-Protected Mesh Network
ONS 15327 networks give you the option of setting up PPMN. PPMN extends the
protection scheme of UPSR from the basic ring configuration to the meshed
architecture of several interconnecting rings. Typical UPSR protection creates
two separate routes between source and destination nodes on a single UPSR.
PPMN does this for source and destination nodes that do not lie on the same ring
but link together through a network of meshed connections. When applied to a
single ring, PPMN uses the same paths as the UPSR.
PPMN connects the source and destination of a circuit over two diverse paths
through a network of single or multiple meshed rings. These two routes form a
circuit-level UPSR. The source sends traffic on each of the diverse routes to the
destination node, where the destination node uses the active route or switches to
the standby route. CTC can automatically route circuits across the PPMN, or you
can manually route circuits.
Figure 33 shows an example of a PPMN. In the example, Node 3 is the source and
Node 9 is the destination. Automated provisioning automatically determines that
the shortest route between the two end nodes passes through Node 8 and Node 7,
shown by the dotted line. Cross-connections are automatically created at nodes 3,
8, 7, and 9 to provide a working-traffic route.
If you check the protected circuit box in CTC, PPMN establishes a second unique
route between Nodes 3 and 9 and automatically creates cross-connections at
nodes 3, 2, 1, 11, and 9, shown by the dashed line. If a signal failure occurs on the
primary path, traffic switches to the second, protected circuit path. In this
example, Node 9 switches from the traffic coming in from Node 7 to the traffic
coming in from Node 11 and service resumes. The switch occurs within 50
milliseconds.