SONET Transport Overhead
SONET provides substantial overhead information, allowing simpler multiplexing and greatly expanded OAM&P capabilities. The SONET TOH, as shown in Figure 5-9, has two layers that include the section overhead and line overhead. Section overhead is used for communications between adjacent NEs, such as regenerators, whereas line overhead is used for the STS-N signal between STS-N multiplexers. You should make a genuine attempt to comprehend this section because a large part of understanding SONET includes understanding the purpose and use of the overhead bytes.