What is a System Management Unit?

Administrative unit (AU) refers to an AU-PTR and a high-level VC. It is a basic unit that provides bandwidth on the backbone network. Currently, there are two forms of AU, namely AU-4 and AU-3.AU. It can be composed of multiple low-order VCs. In this case, each low-order VC is included in a TU. AU-PTR is an indicator used to indicate the exact position of the first byte of the information payload in the STM-N frame, so that the receiving end can accurately separate the information payload according to the value of the position indicator (pointer value). ^[1]