ITU-T Y.1344 PDF

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

The ETH ring maps to the physical layer ring structure. Protection schemes for the other layers, including the Ethernet physical layer network (ETY), are out of the scope of this Recommendation.