Optical Transport Networks from TDM to Packet

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This Handbook discusses the technologies covered by ITU-T Recommendations related to Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN) and Ethernet over Transport (EoT). Each chapter of this Handbook is dedicated to a specific aspect (architecture, multiplexing hierarchy, protection, synchronization, etc.) of SDH, OTN and EoT optical transport networks. Plesiochronous Digital Hierarchy networks, which are at present considered obsolete, and Multiprotocol Label Switching - Transport Profile, which is at a preliminary stage of standardization, are only mentioned in the Preface. Finally, the last chapter of the Handbook discusses automatically switched optical networks (ASON), based on the control planes introduced in addition to transport planes and management planes.



Automatically switched optical networks (ASON)

Up through the late 1990s, transport networks and equipment were wholly configured and provisioned via centralized management systems, with commissioning and installation of new equipment being a tedious error-prone process. Each new generation of technology and equipment had offered additional capabilities to facilitate evolution from full manual operation towards increased automation. However, while a transport network could be re-arranged for network maintenance or improved utilization, it was considered as a relatively static entity (relative to a timescale of less than months) that offered leased line services.


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