Original text:
A YANG Data Model for Optical Impairment-aware Topology <del> draft-ietf-ccamp-optical-impairment-topology-yang-09 </del>  Abstract of unidirectional links are connected to the same bidirectional LTP on either end of the link pair. <del> [Editor's note: text below related to G.807 needs to be revised based on the published G.807 revision!] </del> 2.3.1. The OTSi is defined in ITU-T Recommendation G.959.1, section 3.2.4 defines a pointer (leafref) from the OTSi to the transceiver module terminating the OTSi signal.  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>  2.3.3. The frequency slot of the MC is defined by the n value defining the central frequency of the MC and the m value that defines the width of <del> the MC following the flexible grid definition in ITU-T Recommendation G.694.1 G.694.1.  In this model, the effective frequency slot as defined in ITU-T draft Recommendation G.807 is equal to the frequency slot of this end-to-end MC.  It is also assumed that ROADM devices can switch MCs.  For various reasons (e.g.  differential delay), it is preferred to use a single MC for all OTSi's of the same OTSiG.  It may however not always be possible to find a single MC for carrying all OTSi's of an OTSiG due to spectrum occupation along the OTSiG path. </del>  2.3.4. entity like the LTP described above.  Moreover, a TTP can terminate one or several OTSiG signals (tunnels) as described in I-D.ietf-teas- te-topo-and-tunnel-modeling and each OTSiG consists of one or <del> multiple OTSi signals as described in sect-2.3.2.  Therefore, a TTP may be associated with multiple transceiver modules. </del>  A transponder is typically characterized by its data/symbol rate and the maximum distance the signal can travel.  Other transponder Supported transmitter tuning range with min/max nominal carrier frequency [f_tx_min, f_tx_max] <del> Supported transmitter tunability grid, the distance between two adjacent carrier frequencies (in GHz) </del>  Supported transmitter power range [p_tx-min, p_tx_max] Supported receiver channel power range [p_rx-min, p_rx_max] Supported maximum total power, rx power for all channels fed into regeneration and each transceiver is operated in an uni- directional mode.  Due to the fact that 3R regenerators are composed of an optical transponder pair, the capabilitiy whether an optical transponder can be used as a 3R regenerator is is added to the transponder [Editor's note: this section is still work in progress]  3. [Editor's note: tree view below always has to be updated before

Reviewer comments:
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

Revised text:
A YANG Data Model for Optical Impairment-aware Topology  <ins> draft-ietf-ccamp-optical-impairment-topology-yang-10 </ins> Abstract of unidirectional links are connected to the same bidirectional LTP on either end of the link pair.  2.3.1. The OTSi is defined in ITU-T Recommendation G.959.1, section 3.2.4 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.  <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. The frequency slot of the MC is defined by the n value defining the central frequency of the MC and the m value that defines the width of  <ins> the MC following the flexible grid definition in G.694.1.  In this model, the effective frequency slot as defined in G.807 is equal to the frequency slot of this end-to-end MC.  It is also assumed that ROADM devices can switch MCs.  For various reasons (e.g. differential delay), it is preferred to use a single MC for all OTSi's of the same OTSiG.  It may however not always be possible to find a single MC for carrying all OTSi's of an OTSiG due to spectrum occupation along the OTSiG path. </ins> 2.3.4. entity like the LTP described above.  Moreover, a TTP can terminate one or several OTSiG signals (tunnels) as described in I-D.ietf-teas- te-topo-and-tunnel-modeling and each OTSiG consists of one or  <ins> multiple OTSi signals as described in OTSiG.  Therefore, a TTP may be associated with multiple transceiver modules. </ins> A transponder is typically characterized by its data/symbol rate and the maximum distance the signal can travel.  Other transponder Supported transmitter tuning range with min/max nominal carrier frequency [f_tx_min, f_tx_max]  <ins> Supported transmitter tunability describing the transmitter's frequency fine tuning steps (the minimum distance between two adjacent carrier frequencies in GHz) </ins> Supported transmitter power range [p_tx-min, p_tx_max] Supported receiver channel power range [p_rx-min, p_rx_max] Supported maximum total power, rx power for all channels fed into regeneration and each transceiver is operated in an uni- directional mode. <ins> Implemantations may support the change of the carrier frequency where the receiver may operate at a different optical frequency as the transmitter.  The transceiver mode is a property of the transceiver and is applied to the transmitter and the receiver. Therefore, the transceiver mode is the same for the two segments on the two sides of the 3R regenaretor realised by two transceivers operated in the uni-directional mode. </ins> Due to the fact that 3R regenerators are composed of an optical transponder pair, the capabilitiy whether an optical transponder can be used as a 3R regenerator is is added to the transponder [Editor's note: this section is still work in progress] <ins> 2.10. The YANG model defined in this document supports the following protection architectures: Individual OTSi protection OMS MCG protection = TE-link protection between adjacent WDM-TE- nodes [Editor's note: this section is still work in progress] 2.10.1. Individual OTSi protection is a protection architecture where an individual OTSi signal is protected as defined in Appendix III of ITU-T Recommendation G.873.1 G.873.1.  This protection architecture requires dedicated photonic protection functions that are typically provided by dedicated protection hardware.  These photonic protection functions are a photonic splitter function splitting the OTSi signal in transmit direction and a photonic selector function selecting the OTSi signal in receive direction from one of the two protection legs between the protection functions terminating the individual OTSi protection.  This individual OTSi protection scheme can be considered as a photonic 1+1 protection scheme (1+1 sub-network connection protection (SNCP) in ITU-T terminology). In case of individual OTSi protection, there are two network media channel paths associated with the OTSi signal.  In the YANG model, this is modeled as a leaf list of the otsi providing the nmc-path-id for the two network media channel paths associated with the individually protected otsi. [Editor's note: this section is still work in progress] 2.10.2. OMS MCG protection is a protection architecture where a TE-link between two adjacent WDM-TE-nodes is protected.  This is a local protection scheme, which can be modeled as a TE-link property. [Editor's note: this section is still work in progress] </ins> 3. [Editor's note: tree view below always has to be updated before