SDH Overhead

SDH Overhead
The SDH standard was developed using a client/server layer approach. The overhead and transport functions are divided into
layers. They are:
*-Regenerator Section
*-Multiplex Section
*-Path

The layers have a hierarchical relationship, with each layer building on the services provided by all the lower layers.
This section details the different SDH overhea
information, specifically:
*-Regenerator Section Overhead
*-Multiplex Overhead
*-Path Overhead

Regenerator Section Overhead
The Regenerator Section Overhead contains only the information required for the elements located at both ends of a section. This might
be two regenerators, a piece of line terminating equipment and a regenerator, or two pieces of line terminating equipment.
The Regenerator Section Overhead is found in the first three rows of Columns 1 through 9 of the STM-1 frame. Byte by byte.

Multiplex Section Overhead
The Multiplex Section Overhead contains the information required between the multiplex section termination equipment at each end of the
Multiplex section (that is, between consecutive network elements excluding the regenerators).
The Multiplex Section Overhead is found in Rows 5 to 9 of Columns 1
through 9 of the STM-1 frame . Byte by byte.

Higher-Order Path Overhead
(VC-4/VC-3)
The Path Overhead is assigned to, and transported with the Virtual Container from the time
it’s created by path terminating equipment until the payload is demultiplexed at the termination
point in a piece of path terminating equipment.The Path Overhead is found in Rows 1 to 9
of the first column of the VC-4 or VC-3 . Byte by byte.

(Click the images for large display.)