In this appendix, we will specify the working of SDH/SONET signaling looking in detail at the structure of the frame at the different layers.
This analysis is doubly useful, both as an example of the completeness and complexity of the signaling structure of a carrier class network and for practical reasons. As a matter of fact, the SDH/SONET framing is also frequently used in other kinds of equipment for the sake of compatibility and because all the needed hardware is available.
We will concentrate on SDH, specifying when needed the differences with SONET.
All the elements reported in this appendix, including the figures, have their origin in the SDH/SONET standards. Thus, we refer the reader to the relevant bibliography ...