- What are SONET and T1
- The Development of SONET
- Role of ANSI and Key Standards documents
- The Network and Services Integration Forum (NSIF)
- SONET and T1
- Features of SONET and T1
- Synchronous Networks
- SONET Timing
- Payloads and Envelopes
- Optical Fiber—The Bedrock for SONET
- Typical SONET Topology
- Present Transport Systems and SONET
- Clarification of Terms
Payloads and Envelopes
SONET is designed to support a wide variety of payloads. Table 11. summarizes some typical payloads of existing technologies. The SONET node accepts these payloads and multiplexes them into a SONET envelope. These payloads are called virtual tributaries (VTs) in North America and virtual containers (VCs) in SDH. Later chapters will explain how SONET manages these payloads.
As you can see, the first-generation digital carrier systems are not the same across different geographical regions of the world. Shortly after the inception of T1 in North America, the ITU-T published the E1 standards, which were implemented in Europe, and Japan followed with a hierarchy that was similar to the North American specifications at the lower speeds (but not at the higher speeds).