Automatic protection switching in linear network is defined at the _______

A. Line layer

B. Section layer
C. Photonic layer
D. Path layer

Explanation: The Line layer in SONET operates like the data link layer in the OSI model and it is responsible for the movement of signal across a physical line. The Synchronous Transport Signal Mux/Demux and Add/Drop Mux provide the Line layer functions.

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