Broadband ISDN tools: Synchronous digital hierarchy (SDH)
John Ronayne · 2023
Public transmission network planning for the next few decades is predicated upon the massive introduction and increase of optical transmission in the network. The plans assume that this high-bandwidth optical network will be managed and controlled through the use of the Synchronous Digital Hierarchy (sdh). The story of sdh arises out of the development of leased circuit networks, particularly in the us. The principle of sdh is not unlike this. Lump together a large amount of information from a variety of sources and of varying sizes and put it all in the one envelope. Send along with it a catalogue of the information contained, giving precise information of where it is to be found. This is sdh. In 1988 the agreement envisaged in moving from sonet to sdh was that the sonet envelope at 51.840 Mbit/s would be mapped into sdh as three sonetsts-1 envelopes.