CHAPTE R
12-1
Cisco ONS 15454 Reference Manual, R8.5.x
78-18106-01
12
SONET Topologies and Upgrades
Note The terms "Unidirectional Path Switched Ring" and "UPSR" may appear in Cisco literatur e. These terms
do not refer to using Cisco ONS 15xxx products in a unidirectional path switched ring configuration.
Rather, these terms, as well as "Path Protected Mesh Network" and "PPMN," refer generally to Cisco's
path protection feature, which may be used in any topological n etwork configuration. Cisco does not
recommend using its path protection feature in any parti cular topological network configuration.
This chapter explains Cisco ONS 154 54 SONET topologies and upgrades. To provision topologies, refer
to the Cisco ONS 15454 Procedure Guide.
Chapter topics include:
• 12.1 SONET Rings and TCC2/TCC2P Cards, page 12-1
• 12.2 Bidirectional Line Switched Rings, page 12-3
• 12.3 Path Protection, page 12-14
• 12.4 Dual-Ring Interconnect, page 12-19
• 12.5 Comparison of the Protection Schemes, page 12-28
• 12.6 Subtending Rings, page 12-29
• 12.7 Linear ADM Configurations, page 12-31
• 12.8 Path-Protected Mesh Networks, page 12-31
• 12.9 Four-Shelf Node Configurations, page 12-33
• 12.10 STS around the Ring, page 12-34
• 12.11 OC-N Speed Upgrades, page 12-35
• 12.12 In-Service Topology Upgrades, page 12-38

12.1 SONET Rings and TCC2/TCC2P Cards

Table 12-1 shows the SONET rings that can be created on each ONS 15454 node using redun dant
TCC2/TCC2P cards.