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SONET
28 Avidia System Configuration and Management User Manual
SONET
The Synchronous Optical Network (SONET) is the transport standard for transmitting data over
fiber-optic cable. It supports data rates in the gigabit range, optical interfaces, network
management, and diagnostic testing methods.
SONET comprises four layers, as described in the following table:
REDUNDANCY
Redundancy is a feature of the Avidia system. Redundancy includes:
• dual homing, which provides redundancy at a VPC or VCC level (dual homing also
provides static load sharing) as described on page 29
• card redundancy, where a primary line card can switch to a secondary line card if the
primary card were to fail as described on page 32
• Automatic Protection Switching (APS) for the OC3 line card with dual-PHY connectors,
where the primary physical port switches to the secondary physical port if the primary port
were to fail as described on page 33
Layer Description
Medium The physical layer, in which electrical and optical signals are transported across SONET
cable. This is the lowest SONET layer.
Section Governs communication between SONET network elements, such as regenerators. This
layer handles framing, scrambling, and error monitoring.
Line Establishes communication between SONET line terminating equipment where SONET
signals are multiplexed or demultiplexed. This layer handles data transmission through
synchronization, multiplexing, and other data transport functions.
Path Terminates point-to-point communications. This layer handles transport of services
through the entire network. This is the highest SONET layer.