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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
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9
SDH Topologies and Upgrades
Note The terms “Unidirectional Path Switched Ring” and “UPSR” may appear in Cisco literature. 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 network configuration. Cisco does not
recommend using its path protection feature in any particular topological network configuration.
This chapter explains Cisco ONS 15310-MA SDH topologies and upgrades. To provision topologies,
refer to the Cisco ONS 15310-MA SDH Procedure Guide.
Chapter topics include:
• 9.1 Subnetwork Connection Protection Configurations, page 9-1
• 9.3 Interoperability, page 9-4
• 9.2 Terminal Point-to-Point and Linear ADM Configurations, page 9-3
• 9.4 Path-Protected Mesh Networks, page 9-6
• 9.5 Four Node Configurations, page 9-8
• 9.6 STMN Speed Upgrades, page 9-8
• 9.7 Overlay Ring Circuits, page 9-9

9.1 Subnetwork Connection Protection Configurations

Subnetwork Connection Protection (SNCP) configurations provide duplicate fiber paths around the ring.
Working traffic flows in one direction and protection traffic flows in the opposite direction. If a problem
occurs with the working traffic path, the receiving node switches to the path coming from the opposite
direction.
CTC automates ring configuration. Subnetwork Connection Protection traffic is defined within the
ONS 15310-MA SDH on a circuit-by-circuit basis. If a path-protected circuit is not defined within a 1+1
line protection scheme and Subnetwork Connection Protection is available and specified, CTC uses
Subnetwork Connection Protection as the default.
A Subnetwork Connection Protection circuit requires two data communications channel
(DCC)-provisioned optical spans per node. Subnetwork Connection Protection circuits can be created
across these spans until their bandwidth is consumed.