ITU-T Y.1344 PDF

This Recommendation defines the automatic protection switching (APS) protocol and protection switching mechanisms for ETH layer Ethernet ring topologies. The protection protocol defined in this Recommendation enables protected point-to-point, point-to-multipoint and multipoint-tomultipoint connectivity within the ring or interconnected rings, called "multi-ring/ladder network" topology.

The ETH layer ring maps to physical layer ring structure.

Protection schemes for the other layers, including ETY layer, are out of scope of this Recommendation.