Change:
defines a pointer (leafref) from the OTSi to the transceiver module terminating the OTSi signal. <ins> The OTSi signals in the YANG model are described by augmenting the network and each OTSi signal is uniquely identified by its otsi- carrier-id, which is unique within the scope the OTSiG [see OTSiG below] the OTSi belongs to. </ins> 2.3.2. <del> The definition of the OTSiG is currently being moved from ITU-T Recommendation G.709 G.709 to the new draft Recommendation G.807 (still work in progress) [G.807].  The OTSiG is an electrical signal that is carried by one or more OTSi's.  The relationship between the OTSiG and the the OTSi's is described in ITU-T draft Recommendation G.807, section 10.2 [G.807].  The YANG model below supports both cases: the single OTSi case where the OTSiG contains a single OTSi (see ITU-T draft Recommendation G.807, Figure 10-2) and the multiple OTSi case where the OTSiG consists of more than one OTSi (see ITU-T draft Recommendation G.807, Figure 10-3).  From a layer 0 topology YANG model perspective, the OTSiG is a logical construct that associates the OTSi's, which belong to the same OTSiG.  The typical application of an OTSiG consisting of more than one OTSi is inverse multiplexing.  Constraints exist for the OTSi's belonging to the same OTSiG such as: (i) all OTSi's must be co-routed over the same optical fibers and nodes and (ii) the differential delay between the different OTSi's may not exceed a certain limit.  Example: a 400Gbps client signal may be carried by 4 OTSi's where each OTSi carries 100Gbps of client traffic. </del> <ins> The OTSiG is defined in ITU-T Recommendation G.807 G.807 as a "set of optical tributary signals (OTSi) that supports a single digital client".  Hence, the OTSiG is an electrical signal that is carried by one or more OTSi's.  The relationship between the OTSiG and the the OTSi's is described in G.807, section 10.2.  The YANG model below supports both cases: the single OTSi case where the OTSiG contains a single OTSi (see G.807, Figure 10-2) and the multiple OTSi case where the OTSiG consists of more than one OTSi (see G.807, Figure 10-3). From a layer 0 topology YANG model perspective, the OTSiG is a logical construct that associates the OTSi's, which belong to the same OTSiG.  The typical application of an OTSiG consisting of more than one OTSi is inverse multiplexing.  Constraints exist for the OTSi's belonging to the same OTSiG such as: (i) all OTSi's must be co-routed over the same optical fibers and nodes and (ii) the differential delay between the different OTSi's may not exceed a certain limit.  Example: a 400Gbps client signal may be carried by 4 OTSi's where each OTSi carries 100Gbps of client traffic. All OTSiGs are described in the YANG model by augmenting the network and each OTSiG is uniquely identified by its otsi-group-id, which is unique within the network.  Each OTSiG also contains a list of the OTSi signals belonging to the OTSiG. </ins> 2.3.3.

Discussion:
draft-ietf-ccamp-optical-impairment-topology-URL for IETF 114 submission --> draft-ietf-ccamp-optical-impairment-topology-yang-URL Related to pull request . Addressing and resolving several open issues.
May need to rebase this branch with the master branch to make sure all the validation checks pass