US Patent 7145882 Multiplexed automatic protection switching channels

An apparatus and method that extend the automatic protection switching protocol to address at least 256 network nodes. By using overhead bytes as extended APS node IDs, large single ring SONET/SDH systems can be avoided. This means APS messages that force every node into a single ring can be avoided and recovery performance from a break in the ring or a node fault can be improved. The protocol for the extended automatic protection switching channels takes multiple extended APS node IDs from tributary lines and merges those extended APS ID's into a single SONET/SDH stream on another line. Placement of the extended APS node ID's in the overhead bytes of SONET/SDH frames allows easy relay around each SONET/SDH ring.