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This chapter is from the book

Payloads and Envelopes

SONET is designed to support a wide variety of payloads. Table 1–1. 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).

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