This Recommendation describes both the functional components and the methodology that should be used in order to describe multi-protocol label switching transport profile (MPLS-TP) layer network functionality of network elements; it does not describe individual MPLS-TP network equipment as such. This Recommendation provides a representation of the MPLS-TP technology using the methodologies that have been used for other transport technologies (e.g.@ synchronous digital hierarchy (SDH)@ optical transport network (OTN) and Ethernet).2 This Recommendation forms part of a suite of Recommendations covering the full functionality of network equipment. These Recommendations are [ITU-T G.705]@ [ITU-T G.783]@ [ITU-T G.798]@ [ITU-T G.806] and [ITU-T G.8021]. This Recommendation also follows the principles defined in [ITU-T G.805]. These Recommendations specify a library of basic building blocks and a set of rules by which they may be combined in order to describe digital transmission equipment. The library comprises the functional building blocks needed to specify completely the generic functional structure of the MPLS-TP layer network. In order to be compliant with this Recommendation@ equipment needs to be describable as an interconnection of a subset of these functional blocks contained within this Recommendation. The interconnections of these blocks should obey the combination rules given. Not every atomic function defined in this Recommendation is required for every application. Different subsets of atomic functions may be assembled in different ways according to the combination rules given in this Recommendation to provide a variety of different capabilities. Network operators and equipment suppliers may choose which functions must be implemented for each application. Figure 1-1 presents the set of atomic functions associated with the traffic signal transport. The functions are based on the functional architecture as described in [ITU-T G.8110.1]. It is noted that this Recommendation only defines Ethernet for the client of MPLS-TP as multi-protocol label switching - transport profile / Ethernet MAC layer network (MT/ETH) adaptation function. 2 This ITU-T Recommendation is intended to be aligned with the IETF MPLS RFCs normatively referenced by this Recommendation.