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, and 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.
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