In telecommunications, subnetwork connection protection (SNCP), is a type of protection mechanism associated with synchronous optical networks such as synchronous digital hierarchy (SDH).
SNCP is a dedicated (1+1) protection mechanism for SDH network spans which may be deployed in ring, point to point or mesh topologies.
The changeover criteria are specified individually when configuring a network element.
In order to prevent any unnecessary or spurious protection switching in the presence of bit errors on both paths, a switch will typically occur when the quality of the alternate path exceeds that of the current working path by some threshold (e.g., an order of magnitude better BER).
Consecutively, any case of failure drops in SNCP's decision mechanism.