A system and method for providing APS (automatic protection switching)
redundant pair control protocol signaling for multi-nodal APS (MN-APS) is
provided. Periodic liveliness messages are exchanged between each node of
a redundant pair. Each liveliness message contains an IHY (I heard you)
message which indicates whether or not the sender of the liveliness
message received within a duration of a hold time a previously
transmitted liveliness message from the recipient. When more than one
MN-APS group is configured between two redundant nodes, liveliness
messages are bundled together to reduce processing loads.