First draft of summary: This Recommendation defines the interfaces of the Ethernet transport network to be used within and between subnetworks of the Ethernet network, in terms of: - ethernet transport hierarchy; - functionality of the OAM in support of Ethernet networks; - frame and PDU structures; - bit rates; - formats for mapping and multiplexing client signals. The interfaces defined in this Recommendation can be applied at user-to-network interfaces (UNI) and network node interfaces (NNI) of the Ethernet transport network. The Ethernet UNI is formed by an Ethernet interface and the Ethernet NNI by an Ethernet interface or an Ethernet over Transport interface. The Ethernet over Transport NNI uses various server layer networks like OTH and SDH. It is recognized, for Ethernet over Transport interfaces used within Ethernet subnetworks, that aspects of the interface are transport technology dependent and subject to change as transport technology progresses. Therefore, transport technology dependent aspects are not defined in this Recommendation for these interfaces to allow for transport technology changes. The OAM functionality necessary for operations and management of Ethernet subnetworks is described. The detailed requirements are specified in a number of ITU-T Recommendations, IEEE Standards and MEF Technical Specifications, which are referred to.