SONET, or Synchronous Optical Networking, is a standardized protocol that transfers multiple digital bit streams over optical fiber using lasers or light-emitting diodes (LEDs). Developed in the U.S., it became a standard for synchronous data transmission on optical media. Its international equivalent is the Synchronous Digital Hierarchy (SDH) standard, which was developed for the same purposes but is used mainly outside of North America.
Here’s a brief overview of SONET:
Purpose: SONET provides a method for communicating a large amount of data over large distances using high-speed optical fiber networks.
Rate and Hierarchy: SONET has a basic rate of 51.84 Mbps (known as OC-1) and a set hierarchy of rates that are multiples of this basic rate, such as OC-3 (155.52 Mbps), OC-12 (622.08 Mbps), OC-48 (2.488 Gbps), and so on.
Structure: Data in SONET is sent in frames. Each frame has a specific structure, including a section overhead (SOH) for the entire frame, a line overhead (LOH) for the payload, and the payload itself.
Advantages:
- Standardization: Provides a standardized rate hierarchy and frame format.
- Scalability: Allows for multiplexing, which means lower-rate signals can be aggregated into higher-rate containers for efficient use of bandwidth.
- Flexibility: Can transport many digital data formats, including T1, E1, and ATM.
- High Speeds: Supports high data transmission rates, making it suitable for both metropolitan and long-haul networks.
- Built-in Management and Troubleshooting: The overhead bytes in the SONET frame provide robust network management and troubleshooting capabilities.
Ring Topology: One of the common ways to deploy SONET is in a ring topology, known as a SONET ring. This setup provides redundancy. If one part of the ring fails, data can be rerouted in the opposite direction.
Evolution: With the rise of Ethernet as the dominant networking protocol, Ethernet over SONET (EoS) became a popular way to transport Ethernet traffic over SONET networks. This allows organizations to use their existing SONET infrastructure while benefiting from the widespread use and familiarity of Ethernet.
SONET played a crucial role in the development of optical communications and has served as the backbone for many telecommunication networks. However, with the increasing dominance of IP-based networks and technologies like Wavelength Division Multiplexing (WDM), the direct use of SONET/SDH has been decreasing in some applications but remains significant in legacy systems and specific scenarios.