Uni 1+1 Sig+Data APS supports unidirectional switching operations, 1+1 signaling and 1+1 data path.
In the ingress direction (Rx) switching is done based on local requests only as per the APS specifications. K-bytes are used to signal the far end the APS actions taken.
In the egress direction (Tx), the data is transmitted on both active and protecting circuits.
Each end of the APS group may be actively listening on a different circuit.
The APS channel (bytes K1 and K2 in the SONET header) exchanges APS protocol messages.
In Uni 1+1 Sig+Data APS a received L-RDI signal on the active circuit does not cause that circuit (port) to be placed out of service. The APS group can continue to use that circuit as the active receiver. This behavior is not configurable.
Uni 1+1 Sig+Data APS also supports configurable:
Debounce timers for signal failure and degradation conditions
Suppression of L-RDI alarm generation