"This Recommendation defines the 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-to-multipoint connectivity within a ring or interconnected rings@ called ""multi-ring/ladder network"" topology. The ETH layer ring maps to the physical layer ring structure. Protection schemes for the other layers@ including ETY layer@ are out of the scope of this Recommendation."