This is nice so we can identify the need for a new xMI interface at the NBI of the MDSC


       +-------------------------------------+   |    +---------------+
       |                                     |   |    |   Service     |
       |    Consumer orchestration system    | =====> | Orchestrator  |
       |                                     |   |    |      (1)      |
       +-------------------------------------+   |    +---------------+
                         ^                       |            ^
                         | NSC NBI               |            | XMI (2)
                         v                       |            v
       +-------------------------------------+   |    +---------------+
       |                                     |   |    |     MDSC      |
       | IETF Network Slice Controller (NSC) | =====> |   (Network    |
       | IETF Network Slice Controller (NSC) |   |    | Orchestrator) |
       +-------------------------------------+   |    +---------------+
                         ^                       |            ^
                         | NSC SBI               |            | MPI
                         v                       |            v
       +-------------------------------------+   |    +---------------+
       |         Network Controller(s)       | =====> |  PNC/MSDC(s)  |
       +-------------------------------------+   |    +---------------+

Note 1 - The Service Orchestrator may contain also some MDSC service-related functions,
as described in section 4.2 of [RFC8453].

Note 2 - This is an interface between two MDSC functional elements encompassing different
MDSC service-related functions which is not defined in [RFC8453].

---

                     (Customer VPL Request)
                                
      Boundary                  :
      Between  . . . . . . . . .:. . . . . . . . . . .
      Customer &                :
      Network Operator          : CMI
                                :
                 +-----------------------------+
                 | MDSC (Service Orchestrator) |
                 +-----------------------------+
      Boundary                  :
      Between  . . . . . . . . .:. . . . . . . . . . .
      Consumer &                :
      Network Provider          : NSC NBI (2)
                                :
                 +-----------------------------+
                 | MDSC (Network Orchestrator) |
                 +-----------------------------+
                                :
                                : MPI
                                :
                              -----
                             | PNC |
            Site A          ( ----- )           Site B
           +-----+         (         )         +-----+
           | CE1 |========(  Physical )========| CE2 |
           +-----\         ( Network )         /-----+
                  \         (_______)         /
                   \            ||           /
                    \           ||          /
                VPL1 \          ||         / VPL2
                      \         ||        /
                       \        ||       /
                        \       ||      /
                         \-------------/
                         |     CE3     |
                         +-------------+
                              Site C

      Key:   ... ACTN control connectivity
             === Physical connectivity
             --- Logical connectivity


                    Figure 2: Virtual Private Line Model

---

                     +--------------+   +--------------+
                     |     CNC-A    |   |     CNC-B    |
                     +--------------+   +--------------+
                                 :         :
      Boundary                   :         :
      Between  . . . . . . . . ..:. . . . . . . . . . .
      Consumer &                 :         :
      Network Operator           : CMI-A   : CMI-B
                                 :         :
                       +-----------------------------+
                       | MDSC (Service Orchestrator) |
                       +-----------------------------+
      Boundary                        :
      Between   . . . . . . . . . . . : . . . . . . . . . . .
      Consumer &                      :
      Network Provider                : NSC NBI (2)
                                      :
                       +-----------------------------+
                       | MDSC (Network Orchestrator) |
                       +-----------------------------+
                       :              :              :
                       : MPI          : MPI          : MPI
                       :              :              :
                   +-------+      +-------+      +-------+
                   |  PNC  |      |  PNC  |      |  PNC  |
                   +-------+      +-------+      +-------+
                       :              :              :
                       :              :              :
        ______     ---------      ---------      ---------     ______
       <      >   (         )    (         )    (         )   <      >
       <Site A>==( Physical  )==( Physical  )==( Physical  )==<Site B>
       <      >   ( Network )    ( Network )    ( Network )   <      >
       <      >    (       )      (       )      (       )    <      >
       <      >     -------        -------        -------     <      >
       <      >-----------------------------------------------<      >
       <______>                                               <______>

      Key:   ... ACTN control connectivity
             === Physical connectivity
             --- Logical connectivity


                            Figure 3: VPN Model
---

               +--------------+                  ___________
               |    Service   |                 (           )
               | Orchestrator |---------------->(  Network  )
               +--------------+                 (  Slice 2  )
                  ^                             (___________)
                  |                           ___________  ^
                  |  +--------------+        (           ) :
                  |  |    Service   |------->(  Network  ) :
                  |  | Orchestrator |        (  Slice 1  ) :
                  |  +--------------+        (___________) :
                  |       ^                      ^    ^    :
      Boundary    |       |                      :    :    :
      Between    .|. . . .|. . . . . . . . . . . : . .:. . : . . .
      Consumer &  |       |                      :    :    :
      Network     |       |                      :    :    :
      Provider    v       v                      :    :    :
               +---------------+                 :    :....:
               |     MDSC      |                 :         :
               |   (Network    |                 :         :
               | Orchestrator) |                 :         :
               +---------------+                 :         :
                        ^                  ------^--       :
                        |                 (         )      :
                        v                (  Physical )     :
                    +-------+             ( Network )      :
                    |  PNC  |<------------>(       )    ---^-----
                  +-------  |               -------    (         )
                  |  PNC  |-+                         (  Physical )
                  |       |<-------------------------->( Network )
                  +-------+                             (       )
                                                         -------

      Key: --- ACTN control connection
           ... Virtualization/abstraction through slicing


                         Figure 4: Network Slicing
                         
---

                         +----------+
                         | Consumer |
                         +----------+
                               :
                        .......:....... Network Slice Service Interface
                               :
                       +---------------+
                       |      MDSC     |
                       +---------------+
                               :
                        .......:....... MPI
                               :
                           +-------+
                           |  PNC  |
                           +-------+
                               :
                        .......:....... SBI
                               :
                           ----------
                          (          )
                         (  Physical  )
                          ( Network  )
                           (________)


                  Figure 6: The Yang Interfaces in Context