The index is used to folio and delineate the starting position of VC-n in the...

The index is used to folio and delineate the starting position of VC-n in the corresponding AU or TU frame so that the receiving end can correctly remove the corresponding VC from the STM-N The VC and C packages are then separated into separate low-rate signals, such as PDH That is; Low-rate branch signals can be discarded directly from the STM-N signal