This Recommendation defines the protection switching operation and associated protocol for shared mesh protection at the optical data unit (ODU) layer. The ODU shared mesh protection (SMP) mechanism is based on the generic shared mesh protection architecture defined in [ITU-T G.808.3]. The SMP mechanism uses pre-computed protection paths that are pre-configured into the network elements. These protection paths are activated when necessary via data plane protocol operations. This Recommendation focuses on the activation of the protection paths and the information that the network elements must maintain in order to support the activation of protection paths. The details of how the pre-computation of protection paths is done and how the information about the protection paths is configured into the network elements are outside the scope of this Recommendation. The encoding of the automatic protection switching (APS) protocol into the APS/PCC bytes is outside the scope of this Recommendation. The use of this mechanism with ODUflex that are capable of being resized is for further study.