This Recommendation specifies a methodology for describing equipment for transport networks based on the transport processing functions and architectural entities defined in [ITU-T G.805]. It defines the set of generic atomic and compound functions and the set of rules for how to combine them. The detailed characteristics of equipment functional blocks of specific transport networks (e.g., SDH, OTN) will be defined in follow-up Recommendations based on this methodology. Equipment can then be described by an equipment functional specification (EFS) which lists the atomic functions and their interconnection.