Which layer of a SONET structure is responsible for mapping signals into a Synchronous Payload Envelope (SPE)?

The layer responsible for mapping signals into a Synchronous Payload Envelope (SPE) in a SONET structure is the Path layer. This layer operates above the Line layer and is specifically designed to manage the individual payloads that are carried by SONET frames. It takes incoming payloads, like those from higher-layer protocols, and encapsulates them into the SPE, ensuring that they are correctly formatted for transport.

The Path layer also handles overhead necessary for error detection and performance monitoring of the payload being carried. By managing the encapsulation and the appropriate processing of the payload, the Path layer ensures that the data is effectively transmitted across the network while maintaining synchronization and integrity.

Understanding the distinct roles within the SONET structure is crucial, particularly how each layer interacts with one another. This ensures efficient transmission and minimizes errors in large-scale network operations.