Synchronous Digital Hierarchy Glossary Definition

Synchronous Digital Hierarchy is a historical Telecommunications concept used in older carrier, data-communications, or enterprise network documentation. Historically, the term may also appear in legacy Telecommunications documentation, where implementation details can differ from current networks.

This term remains useful when reading older Telecommunications documentation, migration plans, equipment manuals, or service records.

Related concepts include Telecommunications and Circuit Switching.

Additional Resource: International Telecommunication Union: What Is Telecommunication?

Optical transport hierarchy. Its historical or lifecycle status is qualified so it is not presented as the recommended current technology without context.