CCAMP Working Group                                         I. Busi, Ed.
Internet-Draft                                                    Huawei
Intended status: Informational                              D. King, Ed.
Expires: 26 September 2022                            Old Dog Consulting
                                                           H. Zheng, Ed.
                                                                  Huawei
                                                              Y. Xu, Ed.
                                                                   CAICT
                                                           25 March 2022


         Transport Northbound Interface Applicability Statement
            draft-ietf-ccamp-transport-nbi-app-statement-14

Abstract

   This document provides an analysis of the applicability of the YANG
   models defined by the IETF (in particular in the Traffic Engineering
   Architecture and Signaling (TEAS) and Common Control and Measurement
   Plane (CCAMP) working groups) to support ODU transit services,
   transparent client services, and Ethernet Private Line/Ethernet
   Virtual Private Line (EPL/EVPL) services over Optical Transport
   Network (OTN) in single and multi-domain network scenarios.

   This document also describes how existing YANG models can be used
   through several worked examples and JSON fragments.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 26 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  The Scope of this Document  . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Conventions Used in this Document . . . . . . . . . . . . . .   7
     3.1.  Topology and Traffic Flow Processing  . . . . . . . . . .   7
   4.  Scenarios Description . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Reference Network . . . . . . . . . . . . . . . . . . . .   8
     4.2.  Topology Abstractions . . . . . . . . . . . . . . . . . .  12
     4.3.  Service Configuration . . . . . . . . . . . . . . . . . .  14
       4.3.1.  ODU Transit . . . . . . . . . . . . . . . . . . . . .  14
       4.3.2.  EPL over ODU  . . . . . . . . . . . . . . . . . . . .  15
       4.3.3.  Transparent Client Services . . . . . . . . . . . . .  16
       4.3.4.  EVPL over ODU . . . . . . . . . . . . . . . . . . . .  17
     4.4.  Multi-Function Access Links . . . . . . . . . . . . . . .  18
     4.5.  Protection and Restoration Configuration  . . . . . . . .  19
       4.5.1.  Linear Protection (End-to-End)  . . . . . . . . . . .  20
       4.5.2.  Segmented Protection  . . . . . . . . . . . . . . . .  21
     4.6.  Event Notifications and Alarms  . . . . . . . . . . . . .  21
     4.7.  Path Computation with Constraints . . . . . . . . . . . .  22
   5.  YANG Model Analysis . . . . . . . . . . . . . . . . . . . . .  23
     5.1.  YANG Models for Topology Abstraction  . . . . . . . . . .  23
       5.1.1.  Domain 1 Black Topology Abstraction . . . . . . . . .  24
       5.1.2.  Domain 2 Black Topology Abstraction . . . . . . . . .  28
       5.1.3.  Domain 3 White Topology Abstraction . . . . . . . . .  29
       5.1.4.  Multi-domain Topology Merging . . . . . . . . . . . .  29
     5.2.  YANG Models for Service Configuration . . . . . . . . . .  32
       5.2.1.  ODU Transit Service . . . . . . . . . . . . . . . . .  35
       5.2.2.  EPL over ODU Service  . . . . . . . . . . . . . . . .  37
       5.2.3.  Other OTN Client Services . . . . . . . . . . . . . .  40
       5.2.4.  EVPL over ODU Service . . . . . . . . . . . . . . . .  41
     5.3.  YANG Models for Protection Configuration  . . . . . . . .  42
       5.3.1.  Linear Protection (end-to-end)  . . . . . . . . . . .  42
       5.3.2.  Segmented Protection  . . . . . . . . . . . . . . . .  44
     5.4.  Notifications . . . . . . . . . . . . . . . . . . . . . .  45
     5.5.  Path Computation with Constraints . . . . . . . . . . . .  46
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  46
     6.1.  OTN Security  . . . . . . . . . . . . . . . . . . . . . .  47



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   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  47
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  47
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  49
   Appendix A.  Validating a JSON fragment against a YANG Model  . .  51
     A.1.  JSON CODE . . . . . . . . . . . . . . . . . . . . . . . .  51
     A.2.  Manipulation of JSON fragments  . . . . . . . . . . . . .  52
     A.3.  Comments in JSON fragments  . . . . . . . . . . . . . . .  53
     A.4.  Validation of JSON fragments: DSDL-based approach . . . .  53
     A.5.  Validation of JSON fragments: why not using an XSD-based
           approach  . . . . . . . . . . . . . . . . . . . . . . . .  54
   Appendix B.  Detailed JSON Examples . . . . . . . . . . . . . . .  54
     B.1.  JSON Examples for Topology Abstractions . . . . . . . . .  54
       B.1.1.  JSON Code: mpi1-otn-topology.json . . . . . . . . . .  55
       B.1.2.  JSON Code: mpi1-eth-topology.json . . . . . . . . . .  77
     B.2.  JSON Examples for Service Configuration . . . . . . . . .  82
       B.2.1.  JSON Code: mpi1-odu2-service-config.json  . . . . . .  82
       B.2.2.  JSON Code: mpi1-odu2-tunnel-config.json . . . . . . .  85
       B.2.3.  JSON Code: mpi1-epl-service-config.json . . . . . . .  88
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  89
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  90
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  91

1.  Introduction

   Transport network domains, including Optical Transport Network (OTN)
   and Wavelength Division Multiplexing (WDM) networks are typically
   deployed based on a single vendor or a single technology platform.
   They are often managed using proprietary interfaces to dedicated
   Element Management Systems (EMS), Network Management Systems (NMS)
   and increasingly Software Defined Network (SDN) controllers.

   Support of packet connectivity services over a transport network
   domain is critical for a wide range of applications and services,
   including data center and LAN interconnects, Internet service
   backhauling, mobile backhaul and enterprise Carrier Ethernet
   services.  An explicit goal of operators is to automate the setup of
   these connectivity services across multiple transport network
   domains, that may utilize different technologies.

   A well-defined common open interface to each domain controller or a
   management system is required for network operators to control multi-
   vendor and multi-domain networks and also enable coordination and
   automation of service provisioning.  This is facilitated by using
   standardized data models (e.g., YANG models), and an appropriate
   protocol (e.g., RESTCONF [RFC8040]).





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   This document examines the applicability of the YANG models defined
   by the IETF (in particular in the Traffic Engineering Architecture
   and Signaling (TEAS) and Common Control and Measurement Plane (CCAMP)
   working groups) to support OTN in a single and multi-domain network
   scenarios.

1.1.  The Scope of this Document

   This document assumes a reference architecture, including interfaces,
   based on the Framework for Abstraction and Control of Traffic-
   Engineered Networks (ACTN), defined in [RFC8453].

   The focus of this document is on the interface between the Multi
   Domain Service Coordinator (MDSC) and a Provisioning Network
   Controller (PNC), controlling a transport network domain, called
   MDSC-PNC Interface (MPI) in [RFC8453].

   It is worth noting that the same MPI analyzed in this document could
   be used between hierarchical MDSC controllers, as shown in Figure 4
   of [RFC8453].

   A detailed analysis of the interface between the Customer Network
   Controller (CNC) and the MDSC, called CNC-MDSC Interface (CMI) in
   [RFC8453], as well as the interface between service and network
   orchestrators are outside the scope of this document.  However, when
   needed, this document describes some considerations and assumptions
   about the information which needs to be provided at these interfaces.
   The list of the IETF YANG models which apply to the ACTN MPI can be
   found in [ACTN-YANG].

   The Functional Requirements for the transport API as described in the
   Optical Networking Foundation (ONF) document [ONF_TR-527] have been
   taken as input for defining the reference scenarios analyzed in this
   document.

   The analysis provided in this document confirms that the IETF YANG
   models defined in [RFC8453], [RFC8795], [OTN-TOPO], [CLIENT-TOPO],
   [TE-TUNNEL], [PATH-COMPUTE], [OTN-TUNNEL], and [CLIENT-SIGNAL] can be
   used together to control a multi-domain OTN network to support
   different types of multi-domain services, such as Optical Data Unit
   (ODU) transit services, Transparent client services and EPL/EVPL
   Ethernet Private Line/Ethernet Virtual Private Line (EPL/EVPL)
   services, over a multi-domain OTN connection, satisfying also the
   requirements in [ONF_TR-527].

2.  Terminology

   Domain  A domain, as defined in [RFC4655], is "any collection of



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      network elements within a common sphere of address management or
      path computation responsibility".  Specifically, within this
      document, we mean a part of an operator's network that is under
      common management (i.e., under shared operational management using
      the same instances of a tool and the same policies).  Network
      elements will often be grouped into domains based on technologies,
      vendor profiles, or geographic proximity.

   CNC  Customer Network Controller

   Connection  The data plane configuration of an LSP: within this
      document it is typically an ODU LSP.  An end-to-end connection/LSP
      represents an entire connection between the connection node end-
      points.  A connection/LSP segment represents a portion of the end-
      to-end connection.

   Connectivity Service  A connectivity service, in the context of this
      document, can be considered as a connection between customer
      sites, across the network operator's network [RFC8309].

   E-LINE  Ethernet Line

   EPL  Ethernet Private Line

   EVPL  Ethernet Virtual Private Line

   ILL  Inter-Layer Lock

   Link  It is used to represent the adjacency between two nodes.
      The term physical link represents a link between two physical
      nodes.  The term OTN link represents a link between two OTN nodes.

   LSP  Label Switched Path

   LTP  Link Termination Point

   MDSC  Multi-Domain Service Coordinator

   Network Configuration  As described in [RFC8309] it describes the
      instructions provided to a controller on how to configure parts of
      a network.

   ODU  Optical Channel Data Unit

   OTU  Optical Channel Transport Unit

   OTN  Optical Transport Network




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   PNC  Provisioning Network Controller

   Protection Switching  Protection switching, as defined in
      [ITU-T_G.808.1] and [RFC4427], provides the capability to switch
      the traffic in case of network failures over pre-allocated
      networks resources.  Typically linear protection methods would be
      used and configured to operate as 1+1 unidirectional, 1+1
      bidirectional or 1:n bidirectional.  This ensures fast and simple
      service survivability.

   Protection Transport Entity/LSP  A protection transport entity/LSP,
      as defined in [ITU-T_G.808.1] and [RFC4427], represents the path
      where the "normal" user traffic is transported during protection
      switching events (e.g., when the working transport entity/LSP
      fails).

   Restoration  Restoration methods, as defined in [RFC4427], provide
      the capability to reroute and restore traffic around network
      failures without the necessity to allocate network resources as
      required for dedicated 1+1 protection schemes.  On the other hand,
      restoration times are typically longer than protection switching
      times.

   Service Model  As described in [RFC8309] it describes a service and
      the parameters of the service in a portable way that can be used
      uniformly and independent of the equipment and operating
      environment.

   TE Link  As defined in [RFC8795], is an element of a TE topology,
      presented as an edge on TE graph.

   TE Tunnel  As defined in [TE-TUNNEL], it is a connection-oriented
      service provided by a layered network of delivery of a client's
      data between source and destination tunnel termination points.
      See also [TE-TUTORIAL].

   TE Tunnel Segment  As defined in [TE-TUNNEL], it is a part of a
      multi-domain TE tunnel that spans.  See also [TE-TUTORIAL].

   TE Tunnel Hand-off  It is an access or inter-domain LTP by which a
      multi-domain TE tunnel enters or exits a given network domain.
      See also [TE-TUTORIAL].

   Note - The three definitions above are currently in [TE-TUTORIAL] but
   it is expected that they will be moved to [TE-TUNNEL].  When this
   happens, the reference will be updated and the [TE-TUTORIAL]
   reference will be downgraded to Informative.




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   TPN  Tributary Port Number

   TTP  Tunnel Termination Point

   Termination and Adaptation  It represents the termination of a
      server-layer connection at the node edge-point and the adaptation/
      mapping of the client layer traffic over the terminated server-
      layer connection.

   Transparent Client  As defined in [CLIENT-SIGNAL], it represents a
      client-layer signal, such as Ethernet physical interfaces, FC,
      STM- n, that cannot be switched but only mapped over a server-
      layer TE Tunnel.

   Working Transport Entity/LSP  A working transport entity/LSP, as
      defined in [ITU-T_G.808.1] and [RFC4427], represents the path
      where the "normal" user traffic is transported.

   UNI  User Network Interface

3.  Conventions Used in this Document

3.1.  Topology and Traffic Flow Processing

   The traffic flow between different nodes is specified as an ordered
   list of nodes, separated with commas, indicating within the brackets
   the processing within each node:

         <node> [<processing>]{, <node> [<processing>]}

   The order represents the order of traffic flow being forwarded
   through the network.

   The <processing> represents the type of processing performed by the
   node, which can be just switching at a given layer "(switching-
   layer)" or it can also include an adaptation of a client layer into a
   server layer: "(client-layer) -> server-layer" or "client-layer ->
   (server-layer)", where the round brackets are used to represent at
   which layer (client layer or server layer) the node is switching.

   For example, the following traffic flow:

         R1 [(PKT) -> ODU2], S3 [(ODU2)], S5 [(ODU2)], S6 [(ODU2)],
         R3 [ODU2 -> (PKT)]

   Node R1 is switching at the packet (PKT) layer and mapping packets
   into an ODU2 before transmission to node S3.  Nodes S3, S5 and S6,
   are switching at the ODU2 layer: S3 sends the ODU2 traffic to S5,



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   which then sends it to S6 which finally sends to R3.  Node R3
   terminates the ODU2 from S6 before switching at the packet (PKT)
   layer.

   The paths of working and protection transport entities are specified
   as an ordered list of nodes, separated with commas:

         <node> {, <node>}

   The order represents the order of traffic flow being forwarded
   through the network in the forward direction.  In the case of
   bidirectional paths, the forward and backward directions are selected
   arbitrarily, but the convention is consistent between working/
   protection path pairs, as well as across multiple domains.

   The use of curly brackets denotes multiple nodes in a list.

4.  Scenarios Description

4.1.  Reference Network

   The physical topology of the reference network is shown in Figure 1.
   It represents an OTN network composed of three transport network
   domains that provide connectivity services to an IP customer network
   through nine access links:


























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                  ........................
      .........   :                      :
              :   :   Network domain 1   :   .............
      Customer:   :                      :   :           :
       domain :   :     S1 -------+      :   :  Network  :
              :   :    /           \     :   :  domain 3 :   ..........
          R1 ------- S3 ----- S4    \    :   :           :   :
              :   :    \        \    S2 --------+        :   :Customer
              :   :     \        \    |  :   :   \       :   : domain
              :   :      S5       \   |  :   :    \      :   :
          R2 ------+    /  \       \  |  :   :    S31 --------- R5
              :   : \  /    \       \ |  :   :   /   \   :   :
          R3 ------- S6 ---- S7 ---- S8 ------ S32   S33 ------ R6
              :   : /        |       |   :   : / \   /   :   :.......
          R4 ------+         |       |   :   :/   S34    :          :
              :   :..........|.......|...:   /    /      :          :
      ........:              |       |      /:.../.......:          :
                             |       |     /    /                   :
                  ...........|.......|..../..../...                 :
                  :          |       |   /    /   :    ..............
                  : Network  |       |  /    /    :    :
                  : domain 2 |       | /    /     :    :Customer
                  :         S11 ---- S12   /      :    : domain
                  :        /          | \ /       :    :
                  :     S13     S14   | S15 ------------- R7
                  :     |  \   /   \  |    \      :    :
                  :     |   S16     \ |     \     :    :
                  :     |  /         S17 -- S18 --------- R8
                  :     | /             \   /     :    :
                  :    S19 ---- S20 ---- S21 ------------ R9
                  :                               :    :
                  :...............................:    :.............

                        Figure 1: Reference network

   This document assumes that all the Si transport network switching
   nodes are capable of switching in the electrical domain (ODU
   switching) moreover, all the Si-Sj OTN links within the transport
   network (intra-domain or inter-domain) are 100G links while the
   access Ri-Sj links are 10G links.

   This document also assumes that within the transport network, the
   physical/optical connections supporting the Si-Sj OTN links (up to
   the OTU4 trail), are pre-provisioned using mechanisms that are
   outside the scope of this document and are not exposed at the MPIs to
   the MDSC.





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   Different transmission technologies can be used on the access links
   (e.g., Ethernet, Synchronous Transport Module (STM) and OTU).
   Section 4.3 provides more details about the different assumptions on
   the access links for different types of connectivity services, and
   Section 4.4 describes the control of access links that can support
   different technology configurations (e.g., STM-64, 10GE or OTU2)
   depending on the type of service being configured (multi-function
   access links).

   To carry client signals (e.g., Ethernet or STM-N) over OTN, some ODU
   termination and adaptation resources need to be available on the
   physical edge nodes (e.g., node S3 and S18).  The location of these
   resources within the physical node is implementation-specific and
   outside the scope of standardization.  This document assumes that
   these termination and adaptation resources are located on the
   physical interfaces of the edge nodes terminating the access links.
   In other words, each physical access link has a set of dedicated ODU
   termination and adaptation resources.

   The transport network control architecture, shown in Figure 2,
   follows the ACTN architecture as defined in the ACTN framework
   document [RFC8453], and uses the same functional components:





























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                              --------------
                             |              |
                             |     CNC      |
                             |              |
                              --------------
                                    |
                ....................|....................... CMI
                                    |
                             ----------------
                            |                |
                            |      MDSC      |
                            |                |
                             ----------------
                               /   |    \
                              /    |     \
               ............../.....|......\................ MPIs
                            /      |       \
                           /   ----------   \
                          /   |   PNC2   |   \
                         /     ----------     \
                ----------         |           \
               |   PNC1   |      -----          \
                ----------     (       )      ----------
                    |         (         )    |   PNC3   |
                  -----      (  Network  )    ----------
                (       )    (  Domain 2 )        |
               (         )    (         )       -----
              (  Network  )    (       )      (       )
              (  Domain 1 )      -----       (         )
               (         )                  (  Network  )
                (       )                   (  Domain 3 )
                  -----                      (         )
                                              (       )
                                                -----

                     Figure 2: Controlling Hierarchies

   The NEs within network domains 1, 2 and 3 of Figure 1 are controlled,
   respectively, by PNC1, PNC2 and PNC3 of Figure 2.  The MDSC control
   the end-to-end network through the MPIs toward the underlying PNCs.

   The ACTN framework facilitates separating the network and service
   control from the underlying technology.  It helps the customer to
   define the network as desired by business needs.  The CMI is defined
   to keep a minimal level of dependency (or no dependency at all) from
   the underlying network technologies.  The MPI instead requires some
   specialization according to the domain technology.




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   The control interfaces within the scope of this document are the
   three MPIs, as shown in Figure 2.

   The split of functionality at the MPI in the ACTN architecture
   between the MDSC and the PNCs, is equivalent to separation
   functionality assumed in the ONF T-API interface, as described in the
   ONF T-API multi-domain use cases [ONF_TR-527].  Furthermore, this
   functional separation is similarly defined in the MEF PRESTO
   interface between the Service Orchestration Functionality (SOF) and
   the Infrastructure Control and Management (ICM) in the MEF LSO
   Architecture [MEF55].

   This document does not make any assumption about the control
   architecture of the customer IP network: in line with [RFC8453], the
   CNC is just a functional component within the customer control
   architecture which is capable of requesting connectivity services on
   demand between IP routers at the CMI.

   The CNC can request connectivity services between IP routers which
   can be attached to different transport network domains (e.g., between
   R1 and R8 in Figure 1) or to the same transport network domain (e.g.,
   between R1 and R3 in Figure 1).  Since the CNC is not aware of the
   transport network controller hierarchy, the mechanisms used by the
   CNC to request connectivity services at the CMI is also unaware
   whether the requested service spans a single-domain or multi-domains.

   It is assumed that the CMI allows the CNC to provide all the
   necessary information needed by the MDSC to understand the
   connectivity service request and to determine the network
   configurations to be requested, at the MPIs, to its underlying PNCs
   to support the requested connectivity service.

   The MDSC, after having received a single-domain service request from
   the CNC at the CMI (e.g., between R1 and R3 in Figure 1), can follow
   the same procedures, described above for the multi-domain service,
   and decide the network configuration to request only at the MPI of
   the PNC controlling that domain (e.g., MPI1 of PNC1 in Figure 2).

4.2.  Topology Abstractions

   Abstraction provides a selective method for representing connectivity
   information within a domain.  There are multiple methods to abstract
   a network topology.  This document assumes the abstraction method
   defined in [RFC7926]:

      Abstraction is the process of applying policy to the available TE
      information within a domain, to produce selective information that
      represents the potential ability to connect across the domain.



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      Thus, abstraction does not necessarily offer all possible
      connectivity options, but it presents a general view of potential
      connectivity according to the policies that determine how the
      domain's administrator wants to allow the domain resources to be
      used.

   [RFC8453] Provides the context of topology abstraction in the ACTN
   architecture and discusses a few alternatives for the abstraction
   methods for both packet and optical networks.  This is an important
   consideration since the choice of the abstraction method impacts
   protocol design and the information it carries.  According to
   [RFC8453], there are three types of topologies:

   *  White topology: This is a case where the PNC provides the actual
      network topology to the MDSC without any hiding or filtering.  In
      this case, the MDSC has the full knowledge of the underlying
      network topology;

   *  Black topology: The entire domain network is abstracted as a
      single virtual node with the access links and inter-domain links
      without disclosing any node internal connectivity information;

   *  Grey topology: This abstraction level is between black topology
      and white topology from a granularity point of view.

   Each PNC should provide the MDSC a network topology abstraction
   hiding the internal details of the physical domain network topology
   controlled by the PNC.  As described in section 3 of [RFC8453], the
   level of abstraction provided by each PNC is based on the PNC
   configuration parameters and it is independent of the abstractions
   provided by other PNCs.  Therefore, it is possible that different
   PNCs provides different topology abstractions.  The MDSC can operate
   on each MPI abstract topology regardless of, and independently from,
   the type of abstraction provided by its underlying PNC.

   For analyzing how the MDSC can operate on an abstract topology
   provided by several PNCs that independently applied different
   abstraction policies and therefore provided different types of
   abstract topologies, the following assumptions are made for the
   reference network in Figure 1:

   *  PNC1 and PNC2 provide black topology abstractions which expose at
      MPI1, and MPI2 respectively, a single virtual node (representing
      the whole network domain 1, and domain 2 respectively).

   *  PNC3 provides a white topology abstraction which exposes at MPI3
      all the physical nodes and links within network domain 3.




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   The MDSC should be capable of stitching together the abstracted
   topologies provided by each PNC to build its view of the multi-
   domain network topology.  This topology knowledge may require proper
   oversight, including the application of local policy, configuration
   methods, and the application of a trust model.  Methods of how to
   manage these aspects are out of scope for this document, but
   recomandations are provided in the Security section of this document.

   The MDSC can also provide topology abstraction of its view of the
   multi-domain network topology at its CMIs depending on the customers'
   needs and policies: it can provide different topology abstractions at
   different CMIs.  Analyzing the topology abstractions provided by the
   MDSC to its CMIs is outside the scope of this document.

4.3.  Service Configuration

   In the following scenarios, it is assumed that the CNC is capable of
   requesting connectivity services from the MDSC, for example, to
   interconnect IP routers.

   The type of connectivity services depends on the type of physical
   links (e.g.  OTN link, ETH link or SDH link) between the routers and
   transport network.

   The packet processing inside IP routers, including packet
   encapsualation and decapsulation, Ri (PKT -> foo) and Rj (foo ->
   PKT), are assumed to be performed by means that are not under the
   control of, and not visible to, the MDSC or to the PNCs.  Therefore,
   these mechanisms are outside the scope of this document.

4.3.1.  ODU Transit

   The physical links interconnecting the IP routers and the transport
   network can be 10G OTN links.

   In this case, it is assumed that the physical/optical
   interconnections below the ODU layer (up to the OTU2 trail) are pre-
   provisioned using mechanisms which are outside the scope of this
   document and not exposed at the MPIs between the PNCs and the MDSC.

   For simplicity of the description, it is also assumed that these
   interfaces are not channelized (i.e., they can only support one
   ODU2).

   When a 10Gb IP connectivity service between R1 and R8 is needed, an
   ODU2 end-to-end connection needs to be created, passing through
   transport network nodes S3, S1, S2, S31, S33, S34, S15 and S18, which
   belong to different PNC domains (multi-domain service request):



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         R1 [(PKT) -> ODU2], S3 [(ODU2]), S1 [(ODU2]), S2 [(ODU2]),
         S31 [(ODU2)], S33 [(ODU2)], S34 [(ODU2)],
         S15 [(ODU2)], S18 [(ODU2)], R8 [ODU2 -> (PKT)]

   The MDSC receives, at the CMI, the request to create an ODU2 transit
   service between the access links on S3 and S18, which belong to
   different PNC domains (multi-domain service request).  The MDSC also
   determines the network configuration requests to be sent to its
   underlying PNCs, at the MPIs, to coordinate the setup of a multi-
   domain ODU2 connection segment between the access links on S3 and
   S18.

   When a 10Gb IP connectivity service between R1 and R3 is needed, an
   ODU2 end-to-end connection needs to be created, passing through
   transport network nodes S3, S5 and S6 which belong to the same PNC
   domain (single- domain service request):

         R1 [(PKT) -> ODU2], S3 [(ODU2)], S5 [(ODU2)], S6 [(ODU2)],
         R3 [ODU2 -> (PKT)]

   As described in Section 4.1, the mechanisms, used by the CNC at the
   CMI, are independent on whether the service request is single-domain
   service or multi-domain.

   The MDSC can figure out that it needs to setup an ODU2 transit
   service between the access links on S3 and S6, which belong to the
   same PNC domain (single-domain service request) and it decides the
   proper network configuration to request PNC1.

4.3.2.  EPL over ODU

   The physical links interconnecting the IP routers and the transport
   network can be 10G Ethernet physical links (10GE).

   In this case, it is assumed that the Ethernet physical interfaces (up
   to the MAC layer) are pre-provisioned using mechanisms which are
   outside the scope of this document and not exposed at the MPIs
   between the PNCs and the MDSC.

   When a 10Gb IP connectivity service between R1 and R8 is needed, an
   EPL service needs to be created, supported by an ODU2 end-to-end
   connection, between transport network nodes S3 and S18, passing
   through transport network nodes S1, S2, S31, S33, S34 and S15, which
   belong to different PNC domains (multi-domain service request):

         R1 [(PKT) -> ETH], S3 [ETH -> (ODU2)], S1 [(ODU2)],
         S2 [(ODU2)], S31 [(ODU2)), S33 [(ODU2)], S34 [(ODU2)],
         S15 [(ODU2)], S18 [(ODU2) -> ETH], R8 [ETH -> (PKT)]



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   The MDSC receives, at the CMI, the request to create an EPL service
   between the access links on S3 and S18, which belong to different PNC
   domains (multi-domain service request).  The MDSC determines the
   network configurations to request, at the MPIs, to its underlying
   PNCs, to coordinate the setup of an end-to-end ODU2 connection
   between the nodes S3 and S8, including the configuration of the
   adaptation functions inside these edge nodes, such as S3 [ETH ->
   (ODU2)] and S18 [(ODU2) -> ETH].

   When a 10Gb IP connection between R1 and R2 is needed, an EPL service
   needs to be created, supported by a ODU2 end-to-end connection
   between transport network nodes S3 and S6, passing through the
   transport network node S5, which belong to the same PNC domain
   (single-domain service request):

         R1 [(PKT) -> ETH], S3 [ETH -> (PKT)] S5 [(ODU2)],
         S6 [(ODU2) -> ETH], R2 [ETH -> (PKT)]

   As described in Section 4.1, the mechanisms used by the CNC at the
   CMI are independent on whether the service request is single-domain
   service or multi-domain.

   Based on the assumption above, in this case, the MDSC can figure out
   that it needs to setup an EPL service between the access links on S3
   and S6, that belong to the same PNC domain (single-domain service
   request) and it decides the proper network configuration to request
   PNC1.

4.3.3.  Transparent Client Services

   [ITU-T_G.709] defines mappings of different Transparent Client layers
   into ODU.  Most of them are used to provide Private Line services
   over an OTN transport network supporting a variety of types of
   physical access links (e.g., Ethernet, SDH STM-N, Fibre Channel,
   InfiniBand, etc.) interconnect the IP routers and the transport
   network.

   When a 10Gb IP connectivity service between R1 and R8 is needed,
   using, for example SDH physical links between the IP routers and the
   transport network, an STM-64 Private Line service needs to be
   created, supported by a ODU2 end-to-end connection, between transport
   network nodes S3 and S18, passing through transport network nodes S1,
   S2, S31, S33, S34 and S15, which belong to different PNC domains
   (multi-domain service request):

         R1 [(PKT) -> STM-64], S3 [STM-64 -> (ODU2)], S1 [(ODU2)],
         S2 [(ODU2)], S31 [(ODU2)], S33 [(ODU2)], S34[(ODU2)],
         S15 [(ODU2)], S18 [(ODU2) -> STM-64], R8 [STM-64 -> (PKT)]



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   As described (Section 4.1) the CNC provides the essential information
   to permit the MDSC to compute which type of service is needed, in
   this case, an STM-64 Private Line Service between the access links on
   S3 and S8, and it also decides the network configurations, including
   the configuration of the adaptation functions inside these edge
   nodes, such as S3 [STM-64 -> (ODU2)] and S18 [(ODU2) -> STM-64].

   When a 10Gb IP connectivity service between R1 and R3 is needed, an
   STM-64 Private Line service needs to be created between R1 and R3
   (single-domain service request):

     R1 [(PKT) -> STM-64], S3[STM-64 -> (ODU2)], S5 [(ODU2)],
     S6 [(ODU2) -> STM-64], R3[STM-64 -> (PKT)]

   As described in Section 4.1, the mechanisms, used by the CNC at the
   CMI, are independent on whether the service request is single-domain
   service or multi-domain.

   Based on the assumption above, in this case, the MDSC can figure out
   that it needs to setup an STM-64 Private Line service between the
   access links on S3 and S6, which belong to the same PNC domain
   (single-domain service request), and it decides the proper network
   configuration to request PNC1.

4.3.4.  EVPL over ODU

   When the physical links interconnecting the IP routers and the
   transport network are Ethernet physical links, it is also possible
   that different Ethernet services (e.g., EVPL) can share the same
   physical access link using different VLANs.

   As described in Section 4.3.2, it is assumed that the Ethernet
   physical interfaces (up to the MAC layer) are pre-provisioned.

   When two 1Gb IP links between R1 to R2 and between R1 and R8 are
   needed, two EVPL services need to be created, supported by two ODU0
   end-to-end connections:

         R1 [(PKT) -> VLAN], S3 [VLAN -> (ODU0)], S5 [(ODU0)],
         S6 [(ODU0) -> VLAN], R2 [VLAN -> (PKT)]

         R1 [(PKT) -> VLAN], S3[VLAN -> (ODU0)], S1 [(ODU0)],
         S2 [(ODU0)], S31 [(ODU0)], S33 [(ODU0)], S34 [(ODU0)],
         S15 [(ODU0)], S18 [(ODU0) -> VLAN], R8[VLAN -> (PKT)]







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   It is worth noting that the first EVPL service is required between
   access links which belong to the same PNC domain (single-domain
   service request) while the second EVPL service is required between
   access links which belong to different PNC domains (multi-domain
   service request).

   Since the two EVPL services share the same Ethernet physical link
   between R1 and S3, different VLAN IDs are associated with different
   EVPL services: for example, VLAN IDs 10 and 20 respectively.

   Based on the assumptions described in Section 4.3.2, the CNC sends a
   request to the MDSC, at the CMI, to set up these EVPL services.  The
   MDSC will determine the network configurations to request to the
   underlying PNCs, as described in Section 4.3.2.

4.4.  Multi-Function Access Links

   Some physical links interconnecting the IP routers and the transport
   network can be configured in different modes, e.g., as OTU2 trail or
   STM-64 or 10GE physical links.

   This configuration can be pre-provisioned by means which are outside
   the scope of this document.  In this case, these links will appear at
   the MPI as links supporting only one mode (depending on how the link
   has been pre-provisioned) and will be controlled at the MPI as
   discussed in Section 4.3: for example, a 10G multi-function access
   link can be pre-provisioned as an OTU2 trail (Section 4.3.1), a 10GE
   physical link (Section 4.3.2) or an STM-64 physical link
   (Section 4.3.3).

   It is also possible not to configure these links a-priori and let the
   MDSC (or, in case of a single-domain service request, the PNC) decide
   how to configure these links, based on the service configuration.

   For example, if the physical link between R1 and S3 is a multi-
   functional access link while the physical links between R4 and S6 and
   between R8 and S18 are STM-64 and 10GE physical links respectively,
   it is possible to configure either an STM-64 Private Line service
   between R1 and R4 or an EPL service between R1 and R8.

   The traffic flow between R1 and R4 can be summarized as:

         R1 [(PKT) -> STM-64], S3 [STM-64 -> (ODU2)], S5 [(ODU2)],
         S6 [(ODU2) -> STM-64], R4 [STM-64 -> (PKT)]

   The traffic flow between R1 and R8 can be summarized as:





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         R1 [(PKT) -> ETH], S3 [ETH -> (ODU2)], S1 [(ODU2)],
         S2 [(ODU2)], S31 [(ODU2)), S33 [(ODU2)], S34 [(ODU2)],
         S15 [(ODU2)], S18 [(ODU2) -> ETH], R8 [ETH -> (PKT)]

   The CNC is capable of requesting, via the CMI, the setup of either an
   STM-64 Private Line service, between R1 and R4, or an EPL service,
   between R1 and R8.

   The MDSC, based on the service being requested, decides the network
   configurations to request, at the MPIs, to its underlying PNCs, to
   coordinate the setup of an end-to-end ODU2 connection, either between
   nodes S3 and S6, or between nodes S3 and S18, including the
   configuration of the adaptation functions on these edge nodes, and in
   particular whether the multi-function access link between R1 and S3
   should operate as an STM-64 or as a 10GE physical link.

   Assumptions used in this example, as well as the service scenarios of
   Section 4.3, include:

   *  the R1-S3 and R8-S18 access links will be multi-function access
      links, which can be configured as an OTU2 trail or as an STM-64 or
      a 10GE physical link;

   *  the R3-S6 access link will be a multi-function access link which
      can be configured as an OTU2 trail or as an STM-64 physical link;

   *  the R4-S6 access link is pre-provisioned as an STM-64 physical
      link;

   *  all the other access links (and, in particular, the R2-S6 access
      links) are pre-provisioned as 10GE physical links, up to the MAC
      layer.

4.5.  Protection and Restoration Configuration

   As described in [RFC4427], recovery can be performed by either
   protection switching or restoration mechanisms.  This section
   describes only services which are protected with linear protection,
   considering both end-to-end and segment protection, as defined in
   [ITU-T_G.808.1] and [RFC4427].  The description of services using
   dynamic restoration is outside the scope of this document.

   The MDSC needs to be capable of determining the network
   configurations to request different PNCs to coordinate the protection
   switching configuration to support protected connectivity services
   described in Section 4.3.





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   In the service examples described in Section 4.3, switching within
   the transport network domain is only performed at the OTN ODU layer.
   Therefore, it is also assumed that protection switching within the
   transport network also occurs at the OTN ODU layer, using the
   mechanisms defined in [ITU-T_G.873.1].

4.5.1.  Linear Protection (End-to-End)

   To protect the connectivity services described in Section 4.3 from
   failures within the OTN multi-domain transport network, the MDSC can
   decide to request its underlying PNCs to configure ODU2 linear
   protection between the transport network edge nodes (e.g., nodes S3
   and S18 for the services setup between R1 and R8).

   It is assumed that the OTN linear protection is configured as 1+1
   unidirectional protection switching type according to the definition
   in [ITU-T_G.808.1] and [ITU-T_G.873.1], as well as in [RFC4427].

   In these scenarios, a working transport entity and a protection
   transport entity, as defined in [ITU-T_G.808.1], (or a working LSP
   and a protection LSP, as defined in [RFC4427]) should be configured
   in the data plane.

   Two cases can be considered:

   *  In one case, the working and protection transport entities pass
      through the same PNC domains:

            Working transport entity:     S3, S1, S2,
                                          S31, S33, S34,
                                          S15, S18

            Protection transport entity:  S3, S4, S8,
                                          S32,
                                          S12, S17, S18

   *  In another case, the working and protection transport entities can
      pass through different PNC domains:

            Working transport entity:     S3, S5, S7,
                                          S11, S12, S17, S18

            Protection transport entity:  S3, S1, S2,
                                          S31, S33, S34,
                                          S15, S18






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   The PNCs should be capable of reporting to the MDSC which, is the
   active transport entity, as defined in [ITU-T_G.808.1], in the data
   plane.

   Given the fast dynamic of protection switching operations in the data
   plane (e.g., 50ms switching time), this reporting is not expected to
   be in real-time.

   It is also worth noting that with unidirectional protection
   switching, e.g., 1+1 unidirectional protection switching, the active
   transport entity may be different in the two directions.

4.5.2.  Segmented Protection

   To protect the connectivity services defined in Section 4.3 from
   failures within the OTN multi-domain transport network, the MDSC can
   decide to request its underlying PNCs to configure ODU2 linear
   protection between the edge nodes of each domain.

   For example, the MDSC can request PNC1 to configure linear protection
   between its edge nodes S3 and S2:

         Working transport entity:     S3, S1, S2

         Protection transport entity:  S3, S4, S8, S2

    MDSC can also request PNC2 to configure linear protection between
    its edge nodes S15 and S18:

         Working transport entity:     S15, S18

         Protection transport entity:  S15, S12, S17, S18

   MDSC can also request PNC3 to configure linear protection between its
   edge nodes S31 and S34:

         Working transport entity:     S31, S33, S34

         Protection transport entity:  S31, S32, S34

4.6.  Event Notifications and Alarms

   To realize the three functions of topology update, service update,
   and restoration, the following notification types need to be
   supported:

   1.  Object create




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   2.  Object delete

   3.  Object state change

   4.  Alarm

   There are three types of topology abstraction types defined in
   Section 4.1, Paragraph 16, and the notifications should also be
   abstracted.  The PNC and MDSC should coordinate together to determine
   the notification policy.  This will include information such as when
   an intra-domain alarm occurred.  The PNC may not report the alarm,
   but it should provide notification of the service state change to the
   MDSC.

   Detailed analysis and methods of how event alarms are triggered,
   managed and propagated are outside the scope of this document.

4.7.  Path Computation with Constraints

   It is possible to define constraints to be taken into account during
   path computation procedures (e.g., Include Route Object (IRO) and
   Exclude Route Object (XRO) [RFC5521]).

   For example, the CNC can request, at the CMI, an ODU transit service,
   as described in Section 4.3.1, between R1 and R8 with the constraint
   to pass through the link from S2 to S31 (IRO), such that a qualified
   path could be:

         R1 [(PKT) -> ODU2], S3 [(ODU2]), S1 [(ODU2]), S2 [(ODU2]),
         S31 [(ODU2)], S33 [(ODU2)], S34 [(ODU2)],
         S15 [(ODU2)], S18 [(ODU2)], R8 [ODU2 -> (PKT)]

   If the CNC instead requested to pass through the link from S8 to S12,
   then the above path would not be qualified, while the following would
   be:

        R1 [(PKT) -> ODU2], S3[(ODU2]), S1 [(ODU2]), S2[(ODU2]),
        S8 [(ODU2]), S12[(ODU2]), S15 [(ODU2]), S18[(ODU2]), R8 [ODU2 ->
        (PKT)]

   The mechanisms used by the CNC to provide path constraints at the
   CMI, are outside the scope of this document.  It is assumed that the
   MDSC can satisfy these constraints and take them into account in its
   path computation procedures (which would decide at least which
   domains and inter-domain links) and in the path computation
   constraints to provide to its underlying PNCs, to be taken into
   account in the path computation procedures implemented by the PNCs
   (with a more detailed view of topology).



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   Further detailed analysis is outside the scope of this document.

5.  YANG Model Analysis

   This section analyses how the IETF YANG models can be used at the
   MPIs, between the MDSC and the PNCs, to support the scenarios
   described in Section 4.

   The YANG models described in [ACTN-YANG] are assumed to be used at
   the MPI.

   Section 5.1 describes the different topology abstractions provided to
   the MDSC by each PNC via its own MPI.

   Section 5.2 describes how the MDSC can request different PNCs, via
   their own MPIs, the network configuration needed to setup the
   different services described in Section 4.3.

   Section 5.3 describes how the protection scenarios can be deployed,
   including end-to-end protection and segment protection, for both
   intra-domain and inter-domain scenario.

5.1.  YANG Models for Topology Abstraction

   This section analyses how each PNC can report its respective abstract
   topology to the MDSC, as described in Section 4.1, Paragraph 16,
   using the Topology YANG models, defined in [RFC8345], with the TE
   Topology YANG augmentations, provided in [RFC8795], and the OTN
   technology-specific YANG augmentations, defined in [OTN-TOPO] or the
   Ethernet client technology-specific YANG augmentations, defined in
   [CLIENT-TOPO].

   As described in Section 4.1, the OTU4 trails on inter-domain and
   intra-domain physical links are pre-provisioned and, therefore, not
   exposed at the MPIs.  Only the TE Links they support can be exposed
   at the MPI, depending on the topology abstraction performed by the
   PNC.

   The access links can be multi-function access links, as described in
   Section 4.4.

   As described in Section 4.1, each physical access link has a
   dedicated set of ODU termination and adaptation resources.








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   The [OTN-TOPO] model allows reporting within the OTN abstract
   topology also the access links which are capable of supporting the
   transparent client layers, defined in Section 4.3.3 and in
   [CLIENT-SIGNAL].  These links can also be multi-function access links
   that can be configured as transparent client physical links (e.g.,
   STM-64 physical link) or as an OTUk trail.

   In order to support the EPL and EVPL services, described in
   Section 4.3.2 and Section 4.3.4, the access links, which are capable
   of being configured as Ethernet physical links, are reported by each
   PNC within its respective Ethernet abstract topology, using the
   Topology YANG models, defined in [RFC8345], with the TE Topology YANG
   augmentations, defined in [RFC8795], and the Ethernet client
   technology-specific YANG augmentations, defined in [CLIENT-TOPO].
   These links can also be multi-function access links that can be
   configured as an Ethernet physical link, an OTUk trail, or as a
   transparent client physical links (e.g., STM-64 physical link).  In
   this case, these physical access links are represented in both the
   OTN and Ethernet abstract topologies.

   The PNC reports the capabilities of the access or inter-domain link
   ends it can control.  It is the MDSC responsibility to request
   configuration of these links matching the capabilities of both link
   ends.

   It is worth noting that in the network scenarios analyzed in this
   document (where switching is performed only at the ODU layer), the
   Ethernet abstract topologies reported by the PNCs describes only the
   Ethernet client access links: no Ethernet TE switching capabilities
   are reported in these Ethernet abstract topologies, to report that
   the underlying networt domain is not capable supporting Ethernet TE
   Tunnels/LSPs.

5.1.1.  Domain 1 Black Topology Abstraction

   PNC1 provides the required black topology abstraction, as described
   in Section 4.1, Paragraph 16.  It exposes at MPI1 to the MDSC, two TE
   Topology instances with only one TE node each.

   The first TE Topology instance reports the domain 1 OTN abstract
   topology view (MPI1 OTN Topology), using the OTN technology-specific
   augmentations [OTN-TOPO], with only one abstract TE node (i.e., AN1)
   moreover, only inter-domain and access abstract TE links (which
   represent the inter-domain physical links and the access physical
   links that can support ODU, or transparent client layers, both), as
   shown in Figure 3 below.





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                      ...................................
                      :                                 :
                      :       +-----------------+       :
                      :       |                 |       :
              (R1)- - --------|                 |-------- - -(S31)
                      : AN1-1 |                 | AN1-7 :
                      :       |                 |       :
              (R3)- - --------|                 |       :
                      : AN1-2 |       AN1       |       :
                      :       |                 |       :
              (R4)- - --------|                 |-------- - -(S32)
                      : AN1-3 |                 | AN1-6 :
                      :       |                 |       :
                      :       +-----------------+       :
                      :          |          |           :
                      :    AN1-4 |          | AN1-5     :
                      :..........|..........|...........:

                                 |          |
                               (S11)      (S12)

    Figure 3: OTN Abstract Topology exposed at MPI1 (MPI1 OTN Topology)

   The second TE Topology instance reports the domain 1 Ethernet
   abstract topology view (MPI1 ETH Topology), using the Ethernet
   technology-specific augmentations [CLIENT-TOPO], with only one
   abstract TE node (i.e., AN1) and only access abstract TE links (which
   represent the access physical links which can support Ethernet client
   layers), as shown in Figure 4 below.

                      ...................................
                      :                                 :
                      :       +-----------------+       :
                      :       |                 |       :
              (R1)- - --------|                 |       :
                      : AN1-1 |                 |       :
                      :       |                 |       :
              (R2)- - --------|                 |       :
                      : AN1-8 |       AN1       |       :
                      :       |                 |       :
                      :       |                 |       :
                      :       |                 |       :
                      :       |                 |       :
                      :       +-----------------+       :
                      :                                 :
                      :.................................:

    Figure 4: ETH Abstract Topology exposed at MPI1 (MPI1 ETH Topology)



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   The OTU4 trails on the inter-domain physical links (e.g., the link
   between S2 and S31) are pre-provisioned and exposed as external TE
   Links, within the MPI1 OTN topology (e.g., the external TE Link
   terminating on AN1-7 TE Link Termination Point (LTP) abstracting the
   OTU4 trail between S2 and S31).

   The PNC1 exports at MPI1 the following external TE Links, within the
   MPI1 OTN topology, representing the multi-function access links under
   its control:

   *  two abstract TE Links, terminating on LTP AN1-1 and AN1-2
      respectively, abstracting the physical access link between S3 and
      R1 and the access link between S6 and R3 respectively, reporting
      that they can support STM-64 client signals as well as ODU2
      connections;

   *  one abstract TE Link, terminating on LTP AN1-3, abstracting the
      physical access link between S6 and R4, reporting that it can
      support STM-64 client signals but no ODU2 connections.

   The information about the 10GE access link between S6 and R2 as well
   as the fact that the access link between S3 and R1 can also be
   configured as a 10GE link cannot be exposed by PNC1 within the MPI1
   OTN topology.

   Therefore, PNC1 exports at MPI1, within the MPI1 ETH topology, two
   abstract TE Links, terminating on LTP AN1-1 and AN1-8 respectively,
   abstracting the physical access link between S3 and R1 and the access
   link between S6 and R2 respectively, reporting that they can support
   Ethernet client signal with port-based and VLAN-based
   classifications.

   PNC1 should expose at MPI1 also the ODU termination and adaptation
   resources that are available to carry client signals (e.g., Ethernet
   or STM-N) over OTN.  This information is reported by the Tunnel
   Termination Points (TTPs) within the MPI1 OTN Topology.

   In particular, PNC1 will report, within the MPI1 OTN Topology, one
   TTP for each access link (i.e., AN1-1, AN1-2, AN1-3 and AN1-8) and
   will assign a transition link or an inter-layer lock identifier,
   which is unique across all the TE Topologies PNC1 is exposing at
   MPI1, to each TTP and access link's LTP pair.

   For simplicity purposes, this document assigns the same number to the
   LTP-ID, TTP-ID and ILL-ID that corresponds to the same access link
   (i.e., 1, 2, 3 and 8 respectively for the LTP, TTP and Inter-Layer
   Lock (IIL) corresponding with the access links AN1-1, AN1-2, AN1-3
   and AN1-8).



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   The PNC1 native topology would represent the physical network
   topology of the domain controlled by the PNC, as shown in Figure 5.

                     ..................................
                     :                                :
                     :     Physical Topology @ PNC1   :
                     :                                :
                     :        +----+        +----+    :
                     :        |    |S1-1    |    |S2-3:
                     :        | S1 |--------| S2 |----- - -(S31)
                     :        +----+    S2-1+----+    :
                     :     S1-2/               |S2-2  :
                     :    S3-4/                |      :
                     :    +----+   +----+      |      :
                     :    |    |3 1|    |      |      :
             (R1)- - -----| S3 |---| S4 |      |      :
                     :S3-1+----+   +----+      |      :
                     :   S3-2 \        \S4-2   |      :
                     :         \S5-1    \      |      :
                     :        +----+     \     |      :
                     :        |    |      \S8-2|      :
                     :        | S5 |       \   |      :
                     :        +----+        \  |S8-1  :
             (R2)- - ------  2/    \3        \ |      :
                     :S6-1 \ /5     \1        \|      :
                     :    +----+   +----+   +----+    :
                     :    |    |   |    |   |    |S8-5:
             (R3)- - -----| S6 |---| S7 |---| S8 |----- - -(S32)
                     :S6-2+----+4 2+----+4 3+----+    :
                     :     /         |        |       :
             (R3)- - ------     S7-3 |        | S8-4  :
                     :S6-3           |        |       :
                     :...............|........|.......:

                                     |        |
                                   (S11)    (S12)

               Figure 5: Physical Topology controlled by PNC1

   The PNC1 native topology is not exposed, and therefore it is the
   PNC's responsibility to abstract the whole domain physical topology
   as a single TE node and to maintain a mapping between the LTPs
   exposed at MPI abstract topologies and the associated physical
   interfaces controlled by the PNC:







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      Physical Interface     OTN Topology LTP     ETH Topology LTP
          (Figure 5)          (Figure 3)            (Figure 4)
              S2-3               AN1-7
              S3-1               AN1-1                 AN1-1
              S6-1                                     AN1-8
              S6-2               AN1-2
              S6-3               AN1-3
              S7-3               AN1-4
              S8-4               AN1-5
              S8-5               AN1-6

   Appendix B.1.1 provides the detailed JSON code example ("mpi1-otn-
   topology.json") describing how the MPI1 ODU Topology is reported by
   the PNC1, using the [RFC8345], [RFC8795] and [OTN-TOPO] YANG models,
   at MPI1.

   Appendix B.1.2 provides the detailed JSON code example ("mpi1-eth-
   topology.json") describing how the MPI1 ETH Topology is reported by
   the PNC1, using the [RFC8345], [RFC8795] and [CLIENT-TOPO] YANG
   models, at MPI1.

   It is worth noting that this JSON code example does not provide all
   the attributes defined in the relevant YANG models, including:

   *  YANG attributes that are outside the scope of this document are
      not shown;

   *  The attributes describing the set of label values that are
      available at the inter-domain links (label-restriction container)
      are also not shown to simplify the JSON code example;

   *  The comments describing the rationale for not including some
      attributes in this JSON code example even if in the scope of this
      document are identified with the prefix "// comment" and included
      only in the first object instance (e.g., in the Access Link from
      the AN1-1 description or in the AN1-1 LTP description).

5.1.2.  Domain 2 Black Topology Abstraction

   PNC2 provides the required black topology abstraction, as described
   in Section 4.1, Paragraph 16, to expose to the MDSC, at MPI2, two TE
   Topology instances with only one TE node each:

   *  the first instance reports the domain 2 OTN abstract topology view
      (MPI2 OTN Topology), with only one abstract node (i.e., AN2) and
      only inter-domain and access abstract TE links (which represent
      the inter-domain physical links and the access physical links that
      can support ODU, transparent client layers, or both);



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   *  the instance reports the domain 2 Ethernet abstract topology view
      (MPI2 ETH Topology), with only one abstract TE node (i.e., AN2)
      and only access abstract TE links (which represent the access
      physical links which can support Ethernet client layers).

   PNC2 also reports the ODU termination and adaptation resources which
   are available to carry client signals (e.g., Ethernet or STM-N) over
   OTN in the TTPs within the MPI2 OTN Topology.

   In particular, PNC2 reports in both the MPI2 OTN Topology and MPI2
   ETH Topology an access link that abstracts the multi-function
   physical access link between S18 and R8, and terminates on the AN2-1
   LTP that corresponds to the S18-3 physical interface, within the PNC2
   native topology.  It also reports in the MPI2 ODU Topology an AN2-1
   TTP which abstracts the ODU termination and adaptation resources
   dedicated to this physical access link and the inter-layer lock
   between the AN2-1 TTP, and the AN2-1 LTPs reported within the MPI2
   OTN Topology and the MPI2 ETH Topology.

5.1.3.  Domain 3 White Topology Abstraction

   PNC3 provides the required white topology abstraction, as described
   in Section 4.1, Paragraph 16, to expose to the MDSC, at MPI3, two TE
   Topology instances with multiple TE nodes, one for each physical
   node:

   *  the first instance reports the domain 3 OTN topology view (MPI3
      OTN Topology), with four TE nodes, which represent the four
      physical nodes (i.e.  S31, S32, S33 and S34), and abstract TE
      links, which represent the inter-domain and internal physical
      links;

   *  the second instance reports the domain 3 Ethernet abstract
      topology view (MPI3 ETH Topology), with only two TE nodes, which
      represent the two edge physical nodes (i.e., S31 and S33) and only
      the two access TE links which represent the access physical links.

   PNC3 also reports the ODU termination and adaptation resources which
   are available to carry client signals (e.g., Ethernet or STM-N) over
   OTN in the TTPs within the MPI3 OTN Topology.

5.1.4.  Multi-domain Topology Merging

   MDSC does not have any knowledge of the topologies of each domain
   until each PNC reports its abstract topologies, so the MDSC needs to
   merge these abstract topologies, provided by different PNCs, to build
   its topology view of the multi-domain network (MDSC multi-domain
   native topology), as described in section 4.3 of [RFC8795].



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   The topology of each domain may be in an abstracted shape (refer to
   section 5.2 of [RFC8453] for a different level of abstraction), while
   the inter-domain link information must be complete and fully
   configured by the MDSC.

   The inter-domain link information is reported to the MDSC by the two
   PNCs, controlling the two ends of the inter-domain link.

   The MDSC needs to know how to merge these inter-domain links.  One
   possibility is to use the plug-id information, defined in [RFC8795]:
   two inter-domain TE links, within two different MPI abstract
   topologies, terminating on two LTPs reporting the same plug-id value
   can be merged as a single intra-domain link, within any MDSC native
   topology.

   The value of the reported plug-id information can be either assigned
   by a central network authority and configured within the two PNC
   domains.  Alternatively, it may be discovered using an automatic
   discovery mechanisms (e.g., LMP-based, as defined in [RFC6898]).

   In case the plug-id values are assigned by a central authority, it is
   under the central authority's responsibility to assign unique values.

   In case the plug-id values are automatically discovered, the
   information discovered by the automatic discovery mechanisms needs to
   be encoded as a bit string within the plug-id value.  This encoding
   is implementation-specific, but the encoding rules need to be
   consistent across all the PNCs.

   In case of co-existence within the same network of multiple sources
   for the plug-id (e.g., central authority and automatic discovery or
   even different automatic discovery mechanisms), it is needed that the
   plug-id namespace is partitioned to avoid that different sources
   assign the same plug-id value to different inter-domain links.  Also,
   the encoding of the plug-id namespace within the plug-id value is
   implementation-specific and will need to be consistent across all the
   PNCs.

   This document assumes that the plug-id is assigned by a central
   authority, with the first octet set to 0x00 to represent the central
   authority namespace.  The configuration method used, within each PNC
   domain, are outside the scope of this document.

   For example, this document assumes that the following plug-id values
   are assigned, by administrative configuration, to the inter-domain
   links shown in Figure 1:





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           Inter-Domain Link     Plug-ID Value

              S2-S31               0x000231
              S7-S11               0x000711
              S8-S12               0x000812
              S8-S32               0x000832
              S12-S32              0x001232
              S15-S34              0x001534

   Based on the plug-id values, the MDSC can merge the abstract
   topologies exposed by the underlying PNCs, as described in
   Section 5.1.1, Section 5.1.2 and Section 5.1.3 above, into its multi-
   domain native TE topology, as shown in Figure 6.

                   ........................
                   :                      :
                   :   Network domain 1   :   .............
                   :   Black Topology     :   :           :
                   :     Abstraction      :   :  Network  :
                   : AN1-1                :   :  domain 3 :
           (R1)- - ----------+            :   :  (White)  :
                   :          \   +--------------+        :
           (R2)- - ---------+ +  /        :   :   \       :
                   :         \| /         :   :    \      :
           (R3)- - --------- AN1 --+      :   :    S31 ---- - (R5)
                   :         /|\    \     :   :   /   \   :   :
           (R4)- - ---------+ | \    +--------- S32   S33 - - (R6)
                   :          |  \        :   :/  \   /   :
                   :          |   +---+   :   /    S34    :
                   :..........|.......|...:  /:   /       :
                              |       |     / :../........:
                              |       |    /    /
                   ...........|.......|.../..../....
                   :          |       |  /    /    :
                   : Network  |       + /    /     :
                   : domain 2 |      / /    /      :
                   :          |     / /    /       :
                   :          |    + / +--+        :
                   :          |    |/ /            :
                   : Black    +--- AN2 ------------- - -(R7)
                   : Topology      | |     AN2-1   :
                   : Abstraction   | +-------------- - -(R8)
                   :               |               :
                   :               +---------------- - -(R9)
                   :                               :
                   :...............................:

       Figure 6: Multi-domain Abstract Topology controlled by an MDSC



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5.2.  YANG Models for Service Configuration

   This section analyses how the MDSC can request the different PNCs to
   setup different multi-domains services, as described in Section 4.3,
   using the TE Tunnel YANG model, defined in [TE-TUNNEL], with the OTN
   technology-specific augmentations, defined in [OTN-TUNNEL] with the
   client service YANG model defined in [CLIENT-SIGNAL].

   The service configuration procedure is assumed to be initiated (step
   1 in Figure 7) at the CMI from CNC to MDSC.  Analysis of the CMI
   models (e.g., L1CSM, L2SM, VN) are outside the scope of this
   document, but it is assumed that the CMI YANG models provide all the
   information that allows the MDSC to understand that it needs to
   coordinate the setup of a multi-domain ODU data plane connection
   (which can be either an end-to-end connection or a segment
   connection) and, when needed, also the configuration of the
   adaptation functions in the edge nodes belonging to different
   domains.

































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                                    |
                                    | {1}
                                    V
                             ----------------
                            |           {2}  |
                            | {3}  MDSC      |
                            |                |
                             ----------------
                              ^     ^      ^
                       {3.1}  |     |      |
                    +---------+     |{3.2} |
                    |               |      +----------+
                    |               V                 |
                    |           ----------            |{3.3}
                    |          |   PNC2   |           |
                    |           ----------            |
                    |               ^                 |
                    V               | {4.2}           |
                ----------          V                 |
               |   PNC1   |       -----               V
                ----------      (Network)        ----------
                    ^          ( Domain 2)      |   PNC3   |
                    | {4.1}   (          _)      ----------
                    V          (        )            ^
                  -----       C==========D           | {4.3}
                (Network)    /  (       ) \          V
               ( Domain 1)  /     -----    \       -----
              (           )/                \    (Network)
              A===========B                  \  ( Domain 3)
             / (         )                    \(           )
         AP-1   (       )                      X===========Z
                  -----                         (         ) \
                                                 (       )   AP-2
                                                   -----

                    Figure 7: Multi-domain Service Setup

   As an example, the objective in this section is to configure a
   connectivity service between R1 and R8, such as one of the services
   described in Section 4.3.  The inter-domain path is assumed to be R1
   <-> S3 <-> S1 <-> S2 <-> S31 <-> S33 <-> S34 <->S15 <-> S18 <-> R8
   (see the physical topology in Figure 1).

   According to the different client signal types, different adaptations
   can be required to be configured at the edge nodes (i.e., S3 and
   S18).





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   After receiving such request, MDSC determines the domain sequence,
   i.e., domain 1 <-> domain 3 <-> domain 2, with corresponding PNCs and
   the inter-domain links (step 2 in Figure 7).

   As described in [PATH-COMPUTE], the domain sequence can be determined
   by running the MDSC own path computation on the MDSC native topology,
   defined in Section 5.1.4, if and only if the MDSC has enough topology
   information.  Otherwise, the MDSC can send path computation requests
   to the different PNCs (steps 2.1, 2.2 and 2.3 in Figure 7) and use
   this information to determine the optimal path on its internal
   topology and, therefore, the domain sequence.

   The MDSC will then decompose the tunnel request into a few TE tunnel
   segments and request different PNCs to setup each intra-domain TE
   tunnel segment (steps 3, 3.1, 3.2 and 3.3 in Figure 7).

   The MDSC will take care of the configuration of both the intra-
   domain TE tunnel segments and inter-domain TE tunnel hand-off via
   corresponding MPI (using the TE tunnel YANG model defined in
   [TE-TUNNEL] and the OTN tunnel YANG model augmentations defined in
   [OTN-TUNNEL]) through all the PNCs controlling the domains selected
   during path computation.  More specifically, for the inter-domain TE
   tunnel hand-off, taking into account that the inter-domain links are
   all OTN links, the list of timeslots and the TPN value assigned to
   that ODUk connection at the inter-domain link needs to be configured
   by the MDSC.

   The configuration of the timeslots and the TPN value used by the ODU2
   connection on the internal links within a PNC domain (i.e., on the
   internal links within domain1) is outside the scope of this document,
   since it is a matter of the PNC domain internal implementation.

   However, the configuration of the timeslots used by the ODU2
   connection at the transport network domain boundaries (e.g., on the
   inter-domain links) needs to take into account the timeslots
   available on physical nodes belonging to different PNC domains (e.g.,
   on node S2 within PNC1 domain and node S31 within PNC3 domain).  Each
   PNC provides to the MDSC, at the MPI, the list of available timeslots
   on the inter-domain links using the TE Topology

   YANG model and OTN Topology augmentation.  The TE Topology YANG model
   in [RFC8795] is being updated to report the label set information.
   See section 1.7 of [TE-TUTORIAL] for more details.

   The MDSC, when coordinating the setup of a multi-domain ODU
   connection, also configures the data plane resources (i.e., the list
   of timeslots and the TPN) to be used on the inter-domain links.  The
   MDSC can know the timeslots which are available on the physical OTN



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   nodes terminating the inter-domain links (e.g., S2 and S31) from the
   OTN Topology information exposed, at the MPIs, by the PNCs
   controlling the OTN physical nodes (e.g., PNC1 and PNC3 controlling
   the physical nodes S2 and S31, respectively).

   In any case, the access link configuration is done only on the PNCs
   that control the access links (e.g., PNC-1 and PNC-3) and not on the
   PNCs of transit domain(s) (e.g., PNC-2).  An access link will be
   configured by MDSC after the OTN tunnel is set up.

   Access configuration will vary and will be dependent on each type of
   service.  Further discussion and examples are provided in the
   following sub-sections.

5.2.1.  ODU Transit Service

   In this scenario, described in Section 4.3.1, the physical access
   links are configured as 10G OTN links and, as described in
   Section 5.1, reported by each PNC as TE Links within the OTN abstract
   topologies they expose to the MDSC.

   When an IP link, between R1 and R8 is needed, the CNC requests, at
   the CMI, the MDSC to setup an ODU transit service.

   From its native topology, shown in Figure 6, the MDSC understands, by
   means which are outside the scope of this document, that R1 is
   attached to the access link terminating on AN1-1 LTP in the MPI1 OTN
   Abstract Topology (Figure 3), exposed by PNC1, and that R8 is
   attached to the access link terminating on AN2-1 LTP in the MPI2
   Abstract Topology, exposed by PNC2.

   MDSC then performs multi-domain path computation (step 2 in Figure 7)
   and requests PNC1, PNC2 and PNC3, at MPI1, MPI2 and MPI3
   respectively, to setup ODU2 (Transit Segment) Tunnels within the OTN
   Abstract Topologies they expose (MPI1 OTN Abstract Topology, MPI2 OTN
   Abstract Topology and MPI3 OTN Abstract Topology, respectively).

   The MDSC requests, at MPI1, PNC1 to setup an ODU2 (Transit Segment)
   Tunnel with one primary path between AN-1 and AN1-7 LTPs, within the
   MPI1 OTN Abstract Topology (Figure 3), using the TE Tunnel YANG
   model, defined in [TE-TUNNEL], with the OTN technology-specific
   augmentations, defined in [OTN-TUNNEL]:

   *  Source and Destination TTPs are not specified (since it is a
      Transit Tunnel): i.e., the source, src-tp-id, destination and dst-
      tp-id attributes of the TE tunnel instance are empty





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   *  Ingress and egress points are indicated in the route-object-
      include-exclude list of the explicit-route-objects of the primary
      path:

      -  The first element references the access link terminating on
         AN1-1 LTP

      -  The last two element reference respectively the inter-domain
         link terminating on AN1-7 LTP and the data plane resources
         (i.e., the list of timeslots and the TPN) used by the ODU2
         connection over that link.

   Appendix B.2.1 provides the detailed JSON code ("mpi1-odu2-service-
   config.json") describing how the setup of this ODU2 (Transit Segment)
   Tunnel can be requested by the MDSC, using the [TE-TUNNEL] and
   [OTN-TUNNEL] YANG models at MPI1.

   PNC1 knows, as described in the mapping table in Section 5.1.1, that
   AN-1 and AN1-7 LTPs within the MPI1 OTN Abstract Topology it exposes
   at MPI1 correspond to the S3-1 and S2-3 LTPs, respectively, within
   its native topology.  Therefore it performs path computation for an
   ODU2 connection between these LTPs within its native topology, and
   sets up the ODU2 cross-connections within the physical nodes S3, S1
   and S2.

   Since the R1-S3 access link is a multi-function access link, PNC1
   also configures the OTU2 trail before setting up the ODU2 cross-
   connection in node S3.

   As part of the OUD2 cross-connection configuration in node S2, PNC1
   configures the data plane resources (i.e., the list of timeslots and
   the TPN), to be used by this ODU2 connection on the S2-S31 inter-
   domain link, as requested by the MDSC.

   Following similar requests from MDSC to setup ODU2 (Transit Segment)
   Tunnels within the OTN Abstract Topologies they expose, PNC2 then
   sets up ODU2 cross-connections on nodes S31 and S33 while PNC3 sets
   up ODU2 cross-connections on nodes S15 and S18.  PNC2 also configures
   the OTU2 trail on the S18-R8 multi-function access link.

5.2.1.1.  Single Domain Example

   To setup an ODU2 end-to-end connection, supporting an IP link,
   between R1 and R3, the CNC requests, at the CMI, the MDSC to setup an
   ODU transit service.






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   Following the procedures described in Section 5.2.1, MDSC requests
   only PCN1 to setup the ODU2 (Transit Segment) Tunnel between the
   access links terminating on AN-1 and AN1-2 LTPs within the MPI1
   Abstract Topology and PNC1 sets up ODU2 cross-connections on nodes
   S3, S5 and S6.  PNC1 also configures the OTU2 trails on the R1-S3 and
   R3-S6 multi-function access links.

5.2.2.  EPL over ODU Service

   In this scenario, described in Section 4.3.2, the access links are
   configured as 10GE Links and, as described in Section 5.1, reported
   by each PNC as TE Links within the ETH abstract topologies they
   expose to the MDSC.

   When this IP link, between R1 and R8, is needed, the CNC requests, at
   the CMI, the MDSC to setup an EPL service.

   From its native topology, shown in Figure 6, the MDSC understands, by
   means which are outside the scope of this document, that R1 is
   attached to the access link terminating on AN1-1 LTP in the MPI1 ETH
   Abstract Topology, exposed by PNC1, and that R8 is attached to the
   access link terminating on AN2-1 LTP in the MPI2 ETH Abstract
   Topology, exposed by PNC2.

   As described in Section 5.1.1 and Section 5.1.2:

   *  the AN1-1 LTP, within the MPI1 ETH Abstract Topology, and the
      AN1-1 TTP, within the MPI1 OTN Abstract Topology, have the same
      IIL identifier (within the scope of MPI1);

   *  the AN2-1 LTP, within the MPI2 ETH Abstract Topology, and the
      AN2-1 TTP, within the MPI2 OTN Abstract Topology, have the same
      IIL identifier (within the scope of MPI2).

   Therefore, the MDSC also understands that it needs to coordinate the
   setup of a multi-domain ODU2 Tunnel between AN1-1 and AN2-1 TTPs,
   abstracting the ODU termination and adaptation resources on S3-1 and
   S18-3 physical interfaces, within the OTN Abstract Topologies exposed
   by PNC1 and PNC2, respectively.

   MDSC then performs multi-domain path computation (step 2 in Figure 7)
   and then requests:

   *  PNC1, at MPI1, to setup an ODU2 (Head Segment) Tunnel within the
      MPI1 OTN Abstract Topology;






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   *  PNC1, at MPI1, to steer the Ethernet client traffic from/to AN1-1
      LTP, within the MPI1 ETH Abstract Topology, thought that ODU2
      (Head Segment) Tunnel;

   *  PNC3, at MPI3, to setup an ODU2 (Transit Segment) Tunnel within
      the MPI3 OTN Abstract Topology;

   *  PNC2, at MPI2, to setup ODU2 (Tail Segment) Tunnel within the MPI2
      OTN Abstract Topology;

   *  PNC2, at MPI2, to steer the Ethernet client traffic to/from AN2-1
      LTP, within the MPI2 ETH Abstract Topology, through that ODU2
      (Tail Segment) Tunnel.

   MDSC requests, at MPI1, PNC1 to setup an ODU2 (Head Segment) Tunnel
   with one primary path between the AN1-1 TTP and AN1-7 LTP, within the
   MPI1 OTN Abstract Topology (Figure 3), using the TE Tunnel YANG
   model, defined in [TE-TUNNEL], with the OTN technology-specific
   augmentations, defined in [OTN-TUNNEL]:

   *  Only the Source TTP (i.e., AN1 TE-Node and AN1-1 TTP) is specified
      (since it is a Head Segment Tunnel): therefore the Destination TTP
      is not specified

   *  The egress point in indicated in the route-object-include-exclude
      list of the explicit-route-objects of the primary path:

      -  The last two element reference respectively the inter-domain
         link terminating on AN1-7 LTP and the data plane resources
         (i.e., the list of timeslots and the TPN) used by the ODU2
         connection over that link.

   Since there is not enough information about which client traffic
   should be steered to the OTN Tunnel, the ODU2 (Head Segment) Tunnel
   is setup with the administrative auto state, as defined in
   [TE-TUNNEL].

   Appendix B.2.2 provides the detailed JSON code ("mpi1-odu2-tunnel-
   config.json") describing how the setup of this ODU2 (Head Segment)
   Tunnel can be requested by the MDSC, using the [TE-TUNNEL] and
   [OTN-TUNNEL] YANG models at MPI1.

   MDSC requests, at MPI1, PNC1 to steer the Ethernet client traffic
   from/to AN1-2 LTP, within the MPI1 ETH Abstract Topology (Figure 4),
   thought the MPI1 ODU2 (Head Segment) Tunnel, using the Ethernet
   Client YANG model, defined in [CLIENT-SIGNAL].





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   Appendix B.2.3 provides the detailed JSON code ("mpi1-epl-service-
   config.json") describing how the setup of this EPL service using the
   ODU2 Tunnel can be requested by the MDSC, using the [CLIENT-SIGNAL]
   YANG model at MPI1.

   PNC1 knows, as described in the table in Section 5.1.1, that the
   AN1-1 TTP and the AN1-7 LTP, within the MPI1 OTN Abstract Topology it
   exposes at MPI1, correspond to S3-1 TTP and S2-3 LTP, respectively,
   within its native topology.  Therefore it performs path computation,
   for an ODU2 connection between S3-1 TTP and S2-3 LTP within its
   native topology, and sets up the ODU2 cross-connections within the
   physical nodes S3, S1 and S2, as shown in Section 4.3.2.

   As part of the OUD2 cross-connection configuration in node S2, PNC1
   configures the data plane resources (i.e., the list of timeslots and
   the TPN), to be used by this ODU2 connection on the S2-S31 inter-
   domain link, as requested by the MDSC.

   After the configuration of the ODU2 cross-connection in node S3, PNC1
   also configures the [ETH -> (ODU)] and [(ODU2) -> ETH] adaptation
   functions, within node S3, as shown in Section 4.3.2.

   Since the R1-S3 access link is a multi-function access link, PNC1
   also configures the 10GE link before this step.

   Following similar requests from MDSC to setup ODU2 (Segment) Tunnels
   within the OTN Abstract Topologies, they expose as well as the
   steering of the Ethernet client traffic, PNC3 then sets up ODU2
   cross-connections on nodes S31 and S33 while PNC2 sets up ODU2 cross-
   connections on nodes S15 and S18 as well as the [ETH -> (ODU2)] and
   [(ODU2) -> ETH] adaptation functions in node S18, as shown in
   Section 4.3.2.  PNC2 also configures the 10GE link on the S18-R8
   multi-function access link.

5.2.2.1.  Single Domain Example

   When this IP link, between R1 and R2, is needed, the CNC requests, at
   the CMI, the MDSC to setup an EPL service.

   Following the procedures described in Section 5.2.2, the MDSC
   requests PCN1 to:

   *  Setup an ODU2 (end-to-end) Tunnel between the AN1-1 and AN1-2
      TTPs, abstracting S3-1 and S6-1 TTPs, within the MPI1 OTN Abstract
      Topology exposed by PNC1 at MPI1;






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   *  Steer the Ethernet client traffic between the AN1-1 and AN1-8
      LTPs, exposed by PNC1 within MPI1 ETH Abstract Topology, through
      that ODU2 (end-to-end) Tunnel.

   Then PNC1 sets up ODU2 cross-connections on nodes S3, S5 and S6 as
   well as the [ETH -> (ODU)] and [(ODU2) -> ETH] adaptation functions
   in nodes S3 and S6, as shown in Section 4.3.2.  PNC1 also configures
   the 10GE link on the R1-S3 multi-function access link (the R2-S6
   access link has been pre-provisioned as a 10GE link, as described in
   Section 4.4).

5.2.3.  Other OTN Client Services

   In this scenario, described in Section 4.3.3, the access links are
   configured as STM-64 links and, as described in Section 5.1, reported
   by each PNC as TE Links within the OTN Abstract Topologies they
   expose to the MDSC.

   The CNC requests, at the CMI, MDSC to setup an STM-64 Private Line
   service between R1 and R8.

   Following similar procedures as described in Section 5.2.2, the MDSC
   understands that:

   *  R1 is attached to the access link terminating on AN1-1 LTP in the
      MPI1 OTN Abstract Topology, exposed by PNC1, and that R8 is
      attached to the access link terminating on AN2-1 LTP in the MPI2
      OTN Abstract Topology, exposed by PNC2;

   *  it needs to coordinate the setup of a multi-domain ODU2 Tunnel
      between the AN1-1 and AN2-1 TTPs, abstracting the ODU termination
      and adaptation resources on S3-1 and S18-3 physical interfaces,
      within the OTN Abstract Topologies exposed by PNC1 and PNC2,
      respectively.

   The MDSC then performs multi-domain path computation (step 2 in
   Figure 7) and then requests:

   *  PNC1, at MPI1, to setup an ODU2 (Head Segment) Tunnel within the
      MPI1 OTN Abstract Topology;

   *  PNC1, at MPI1, to steer the STM-64 transparent client traffic
      from/to AN1-1 LTP, within the MPI1 OTN Abstract Topology, thought
      that ODU2 (Head Segment) Tunnel;

   *  PNC3, at MPI3, to setup an ODU2 (Transit Segment) Tunnel within
      the MPI3 OTN Abstract Topology;




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   *  PNC2, at MPI2, to setup ODU2 (Tail Segment) Tunnel within the MPI2
      OTN Abstract Topology;

   *  PNC2, at MPI2, to steer the STM-64 transparent client traffic to/
      from AN2-1 LTP, within the MPI2 ETH Abstract Topology, through
      that ODU2 (Tail Segment) Tunnel.

   PNC1, PNC2 and PNC3 then sets up the ODU2 cross-connections within
   the physical nodes S3, S1, S2, S31, S33, S15 and S18 as well as the
   [STM-64 -> (ODU)] and [(ODU2) -> STM-64] adaptation functions in
   nodes S3 and S18, as shown in Section 4.3.3.  PNC1 and PNC2 also
   configure the STM-64 links on the R1-S3 and R8-S18 multi-function
   access links, respectively.

5.2.3.1.  Single Domain Example

   When an IP link, between R1 and R3, is needed, the CNC requests, at
   the CMI, the MDSC to setup an STM-64 Private Line service.

   The MDSC and PNC1 follows similar procedures as described in
   Section 5.2.2.1 to set up ODU2 cross-connections on nodes S3, S5 and
   S6 as well as the [STM-64 -> (ODU)] and [(ODU2) -> STM-64] adaptation
   functions in nodes S3 and S6, as shown in Section 4.3.3.  PNC1 also
   configures the STM-64 links on the R1-S3 and R3-S6 multi-function
   access links.

5.2.4.  EVPL over ODU Service

   In this scenario, described in Section 4.3.2, the access links are
   configured as 10GE links, as described in Section 5.2.2 above.

   The CNC requests, at the CMI, the MDSC to setup two EVPL services:
   one between R1 and R2, and another between R1 and R8.

   Following similar procedures as described in Section 5.2.2 and
   Section 5.2.2.1, MDSC understands that:

   *  R1 and R2 are attached to the access links terminating
      respectively on AN1-1 and AN1-8 LTPs in the MPI1 ETH Abstract
      Topology, exposed by PNC1, and that R8 is attached to the access
      link terminating on AN2-1 LTP in the MPI2 ETH Abstract Topology,
      exposed by PNC2;

   *  To setup the first (single-domain) EVPL service, between R1 and
      R2, it needs to coordinate the setup of a single-domain ODU0
      Tunnel between the AN1-1 and AN1-8 TTPs, abstracting S3-1 and S6-1
      TTPs, within the OTN Abstract Topology exposed by PNC1;




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   *  To setup the second (multi-domain) EPVL service, between R1 and
      R8, it needs to coordinate the setup of a multi-domain ODU0 Tunnel
      between the AN1-1 and AN2-1 TTPs, abstracting the ODU termination
      and adaptation resources on S3-1 and S18-3 physical interfaces,
      within the OTN Abstract Topologies exposed by PNC1 and PNC2,
      respectively.

   To setup the first (single-domain) EVPL service between R1 and R2,
   the MDSC and PNC1 follows similar procedures as described in
   Section 5.2.2.1 to set up ODU0 cross-connections on nodes S3, S5 and
   S6 as well as the [VLAN -> (ODU0)] and [(ODU0) -> VLAN] adaptation
   functions, in nodes S3 and S6, as shown in Section 4.3.2.  PNC1 also
   configures the 10GE link on the R1-S3 multi-function access link.

   As part of the [VLAN -> (ODU0)] and [(ODU0) -> VLAN] adaptation
   functions configurations in nodes S2 and S6, PNC1 configures also the
   classification rules required to associate only the Ethernet client
   traffic received with VLAN ID 10 on the R1-S3 and R2-S6 access links
   with this EVPL service.  The MDSC provides this information to PNC1
   using the [CLIENT-SIGNAL] model.

   To setup the second (multi-domain) EVPL service between R1 and R8,
   the MDSC, PNC1, PNC2 and PNC3 follows similar procedures as described
   in Section 5.2.2 to setup the ODU0 cross-connections within the
   physical nodes S3, S1, S2, S31, S33, S15 and S18 as well as the [VLAN
   -> (ODU0)] and [(ODU0) -> VLAN] adaptation functions in nodes S3 and
   S18, as shown in Section 4.3.2.  PNC2 also configures the 10GE link
   on the R8-S18 multi-function access link (the R1-S3 10GE link has
   been already configured when the first EVPL service has been setup).

   As part of the [VLAN -> (ODU0)] and [(ODU0) -> VLAN] adaptation
   functions configurations in nodes S3 and S18, PNC1 and, respectively,
   PNC2 configure also the classification rules required to associated
   only the Ethernet client traffic received with VLAN ID 20 on the
   R1-S3 and R8-S18 access links with this EVPL service.  The MDSC
   provides this information to PNC1 and PNC2 using the [CLIENT-SIGNAL]
   model.

5.3.  YANG Models for Protection Configuration

5.3.1.  Linear Protection (end-to-end)

   As described in Section 4.5.1, the MDSC can decide to protect a
   multi-domain connectivity service by setting up ODU linear protection
   switching between edge nodes controlled by different PNCs (e.g.,
   nodes S3 and S8, controlled by PNC1 and PNC2 respectively, to protect
   services between R1 and R8).




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   MDSC performs path computation, as described in Section 5.2, to
   compute both the paths for working and protection transport entities:
   the computed paths can pass through these exact PNC domains or
   through different transit PNC domains.

   Considering the case, described in Section 4.5.1, where the working
   and protection transport entities pass through the same domain, MDSC
   would perform the same steps described in Section 5.2 to setup the
   ODU Tunnel and to configure the steering of the client traffic
   between the access links and the ODU Tunnel.  The only differences
   are in the configuration of the ODU Tunnels.

   MDSC requests at the MPI1, PNC1 to setup an ODU2 (Head Segment)
   Tunnel within the MPI1 OTN Abstract Topology (Figure 3), using the TE
   Tunnel YANG model, defined in [TE-TUNNEL], with the OTN technology-
   specific augmentations, defined in [OTN-TUNNEL], with one primary
   path and one secondary path with 1+1 protection switching enabled:

   *  Only the Source TTP (i.e., AN1-1 TTP) is specified (since it is a
      Head Segment Tunnel), as described in Section 5.2.2;

   *  The egress point for the working transport entity in indicated in
      the route-object-include-exclude list of the explicit-route-
      objects of the primary path, as described in Section 5.2.2;

   *  The protection switching end-point in indicated in the route-
      object-include-exclude list of the explicit-route-objects of the
      secondary path:

      -  The first element references the TE-Node of the Source TTP
         (i.e., AN1 TE-Node);

   *  The egress point for the protection transport entity in indicated
      in the route-object-include-exclude list of the explicit-route-
      objects of the secondary path:

      -  The last two element reference respectively the inter-domain
         link terminating on AN1-6 LTP and the data plane resources
         (i.e., the list of timeslots and the TPN) used by the ODU2
         connection over that link.











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   PNC1 knows, as described in the table in Section 5.1.1, that the
   AN1-1 TTP, AN1-7 LTP and the AN1-6 LTP, within the MPI1 OTN Abstract
   Topology it exposes at MPI1, correspond to S3-1 TTP, S2-3 LTP and the
   S8-5 LTP, respectively, within its native topology.  It also
   understands, from the route-object-include-exclude list of the
   explicit-route-objects of the secondary path configuration (whose
   last two elements represent an inter-domain link), that node S3 is
   the end-point of the protection group while the other end-point is
   outside of its control domain.

   PNC1 can perform path computation within its native topology and
   setup the ODU connections in nodes S3, S1, S2, S4 and S8 as well as
   configure the protection group in node S3.

5.3.2.  Segmented Protection

   Under specific policies, it is possible to deploy a segmented
   protection for multi-domain services.  The configuration of the
   segmented protection can be divided into a few steps, considering the
   example in Section 4.5.2, the following steps would be used.

   MDSC performs path computation, as described in Section 5.2, to
   compute all the paths for working and protection transport entities,
   which pass through the same PNC domains and inter-domain links: the
   MDSC would perform the same steps described in Section 5.2 to setup
   the ODU Tunnel and to configure the steering of the client traffic
   between the access links and the ODU Tunnel.  The only differences
   are in the configuration of the ODU Tunnels.

   MDSC requests at the MPI1, PNC1 to setup an ODU2 (Head Segment)
   Tunnel within the MPI1 OTN Abstract Topology (Figure 3), using the TE
   Tunnel YANG model, defined in [TE-TUNNEL], with the OTN technology-
   specific augmentations, defined in [OTN-TUNNEL], with one primary
   path and one secondary path with 1+1 protection switching enabled:

   *  Only the Source TTP (i.e., AN1-1 TTP) is specified (since it is a
      Head Segment Tunnel), as described in Section 5.2.2;

   *  The egress point (i.e., AN1-7 LTP) is indicated in the route-
      object-include-exclude list of the explicit-route-objects of the
      primary path, as described in Section 5.2.2;

   *  The protection switching end-points are indicated in the route-
      object-include-exclude list of the explicit-route-objects of the
      secondary path:

      -  The first element references the TE-Node of the Source TTP
         (i.e., AN1 TE-Node);



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      -  The last element references the TE-Node of the egress point
         (i.e., AN1 TE-Node).

   As described in Section 5.2.2, PNC1 knows that the AN1-1 TTP and the
   AN1-7 LTP, within the MPI1 OTN Abstract Topology it exposes at MPI1,
   correspond to S3-1 TTP and the S2-3 LTP, respectively, within its
   native topology.  It also understands, from the route-object-include-
   exclude list of the explicit-route-objects of the secondary path

   configuration (whole last element represent an abstract node
   terminating the inter-domain link used for the primary path), that
   the protection group should be terminated in nodes S3 and S2.

   PNC1 will perform path computations using its native topology and
   setup the ODU connections in nodes S3, S1, S2, S4 and S8 as well as
   configure the protection group in nodes S3 and S2.

   Following similar requests from MDSC to setup ODU2 (Segment) Tunnels,
   with segment protection, within the OTN Abstract Topologies they
   expose.  PNC3 then sets up ODU2 cross-connections on nodes S31, S32,
   S33 and S34 and segment protection between nodes S31 and D34.  PNC2
   sets up ODU2 cross-connections on nodes S15, S12, S17 and S18 and
   segment protection between nodes S15 and S18.

   MDSC stitch the configuration above to form its internal view of the
   end-to-end tunnel with segmented protection.

   Given the configuration above, the protection capability has been
   deployed on the tunnels.  The head-end node of each domain can do the
   switching once there is a failure on one of the tunnel segments.  For
   example, in Network domain 1, when there is a failure on the S1-S2
   lin, the head-end nodes S2 and S3 will automatically do the switching
   to S3-S4-S8-S2.  This switching will be reported to the corresponding
   PNC (PNC1 in this example) and then MDSC.  Other PNCs (PNC2 and PNC3
   in this example) will not be aware of the failure and switching, nor
   do the nodes in network domains 2 and 3.

5.4.  Notifications

   Notification mechanisms are required for the scenarios analyzed in
   this draft, as described in Section 4.6.

   The notification mechanisms are protocol-dependent.  It is assumed
   that the RESTCONF protocol, defined in [RFC8040] is optional, and may
   be used at the MPIs mentioned in this document.






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   From the perspective of MPI, the MDSC is the client while the PNC is
   acting as the server of the notification.  The essential event
   streams, subscription and processing rules after receiving
   notification can be found in section 6 of [RFC8040].

   Additional alarm reporting functions and alarm report management may
   be found in [ITU-T_X.733] and [ITU-T_X.734]

   Further detailed analysis of notification management is outside the
   scope of this document.

5.5.  Path Computation with Constraints

   The path computation constraints that can be supported at the MPI
   using the IETF YANG models defined in [TE-TUNNEL] and [PATH-COMPUTE].

   When there is a technology-specific network (e.g., OTN), the
   corresponding technology (e.g., OTN) model should also be used to
   specify the tunnel information on MPI, with the constraint included
   in TE Tunnel model.

   Further detailed analysis is outside the scope of this document.

6.  Security Considerations

   This document analyses the applicability of the YANG models being
   defined by the IETF to support OTN single and multi-domain scenarios.

   When deploying ACTN functional components the securing of external
   interfaces and hardening of resource datastores, the protection of
   confidential information, and limit the access of function, should
   all be carefully considered.  Section 9 of [RFC8453] highlights that
   implementations should consider encrypting data that flows between
   key components, especially when they are implemented at remote nodes.
   Further discussion on securing the interface between the MDSC and
   PNCs via the MDSC-PNC Interface (MPI) is discussed in section 9.2 of
   [RFC8453].

   The YANG modules highlighted in this document are designed to be
   accessed via network configuration protocols such as NETCONF
   [RFC6241] or RESTCONF [RFC8040].  When using NETCONF, utilizing a
   secure transport via Secure Shell (SSH) [RFC6242] is mandatory.  If
   using RESTCONF, then secure transport via TLS [RFC8446] is mandatory.
   When using either NETCONF or RESTCONF, the use of Network
   Configuration Access Control Model (NACM) [RFC8341] may be used to
   restrict access to specific protocol operations and content.





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6.1.  OTN Security

   Inherently OTN networks ensure privacy and security via hard
   partitioning of traffic onto dedicated circuits.  The separation of
   network traffic makes it difficult to intercept data transferred
   between nodes over OTN-channelized links.

   Within OTN environments, the (General Communication Channel) GCC is
   used for OAM functions such as performance monitoring, fault
   detection, and signaling.  The GCC control channel should be secured
   using a suitable mechanism.

7.  IANA Considerations

   This document requires no IANA actions.

8.  References

8.1.  Normative References

   [CLIENT-SIGNAL]
              Zheng, H., Guo, A., Busi, I., Snitser, A., and F. Lazzeri,
              "A YANG Data Model for Transport Network Client Signals",
              Work in Progress, Internet-Draft, draft-ietf-ccamp-client-
              signal-yang-06, 5 January 2022,
              <https://www.ietf.org/archive/id/draft-ietf-ccamp-client-
              signal-yang-06.txt>.

   [CLIENT-TOPO]
              Zheng, H., Guo, A., Busi, I., Xu, Y., Zhao, Y., and X.
              Liu, "A YANG Data Model for Ethernet TE Topology", Work in
              Progress, Internet-Draft, draft-ietf-ccamp-eth-client-te-
              topo-yang-02, 7 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-ccamp-eth-
              client-te-topo-yang-02.txt>.

   [ITU-T_G.709]
              ITU-T Recommendation G.709, "Interfaces for the optical
              transport network", ITU-T G.709 , March 2020.

   [ITU-T_G.808.1]
              International Telecommunication Union, "Generic protection
              switching - Linear trail and subnetwork protection", ITU-T
              Recommendation G.808.1 , May 2014.







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   [ITU-T_G.873.1]
              International Telecommunication Union, "Optical transport
              network (OTN): Linear protection", ITU-T Recommendation
              G.873.1 , October 2017.

   [OTN-TOPO] Zheng, H., Busi, I., Liu, X., Belotti, S., and O. G. D.
              Dios, "A YANG Data Model for Optical Transport Network
              Topology", Work in Progress, Internet-Draft, draft-ietf-
              ccamp-otn-topo-yang-14, 7 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-ccamp-otn-
              topo-yang-14.txt>.

   [OTN-TUNNEL]
              Zheng, H., Busi, I., Belotti, S., Lopez, V., and Y. Xu,
              "OTN Tunnel YANG Model", Work in Progress, Internet-Draft,
              draft-ietf-ccamp-otn-tunnel-model-15, 7 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-ccamp-otn-
              tunnel-model-15.txt>.

   [PATH-COMPUTE]
              Busi, I., Belotti, S., Dios, O. G. D., Sharma, A., and D.
              Ceccarelli, "A YANG Data Model for requesting path
              computation", Work in Progress, Internet-Draft, draft-
              ietf-teas-yang-path-computation-18, 22 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-yang-
              path-computation-18.txt>.

   [RFC4427]  Mannie, E., Ed. and D. Papadimitriou, Ed., "Recovery
              (Protection and Restoration) Terminology for Generalized
              Multi-Protocol Label Switching (GMPLS)", RFC 4427,
              DOI 10.17487/RFC4427, March 2006,
              <https://www.rfc-editor.org/info/rfc4427>.

   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
              Computation Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC5521]  Oki, E., Takeda, T., and A. Farrel, "Extensions to the
              Path Computation Element Communication Protocol (PCEP) for
              Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April
              2009, <https://www.rfc-editor.org/info/rfc5521>.









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   [RFC7926]  Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
              Ceccarelli, D., and X. Zhang, "Problem Statement and
              Architecture for Information Exchange between
              Interconnected Traffic-Engineered Networks", BCP 206,
              RFC 7926, DOI 10.17487/RFC7926, July 2016,
              <https://www.rfc-editor.org/info/rfc7926>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

   [RFC8453]  Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
              Abstraction and Control of TE Networks (ACTN)", RFC 8453,
              DOI 10.17487/RFC8453, August 2018,
              <https://www.rfc-editor.org/info/rfc8453>.

   [RFC8795]  Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Gonzalez de Dios, "YANG Data Model for Traffic
              Engineering (TE) Topologies", RFC 8795,
              DOI 10.17487/RFC8795, August 2020,
              <https://www.rfc-editor.org/info/rfc8795>.

   [TE-TUNNEL]
              Saad, T., Gandhi, R., Liu, X., Beeram, V. P., Bryskin, I.,
              and O. G. D. Dios, "A YANG Data Model for Traffic
              Engineering Tunnels, Label Switched Paths and Interfaces",
              Work in Progress, Internet-Draft, draft-ietf-teas-yang-te-
              29, 7 February 2022, <https://www.ietf.org/archive/id/
              draft-ietf-teas-yang-te-29.txt>.

8.2.  Informative References

   [ACTN-YANG]
              Lee, Y., Zheng, H., Ceccarelli, D., Yoon, B. Y., and S.
              Belotti, "Applicability of YANG models for Abstraction and
              Control of Traffic Engineered Networks", Work in Progress,
              Internet-Draft, draft-ietf-teas-actn-yang-09, 7 March
              2022, <https://www.ietf.org/archive/id/draft-ietf-teas-
              actn-yang-09.txt>.

   [ITU-T_X.733]
              International Telecommunication Union, "Information
              technology - Open Systems Interconnection - Systems
              Management: Alarm reporting function", ITU-T
              Recommendation X.733 , February 1992.





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   [ITU-T_X.734]
              International Telecommunication Union, "Information
              technology - Open Systems Interconnection - Systems
              Management: Event report management function", ITU-T
              Recommendation X.734 , September 1992.

   [MEF55]    MEF Forum, "Lifecycle Service Orchestration (LSO):
              Reference Architecture and Framework", MEF 55 , March
              2016,
              <https://www.mef.net/Assets/Technical_Specifications/PDF/
              MEF_55.pdf>.

   [ONF_TR-527]
              Open Networking Foundation, "Functional Requirements for
              Transport API", ONF Technical Recommendation TR-527 , May
              2014.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6898]  Li, D., Ceccarelli, D., and L. Berger, "Link Management
              Protocol Behavior Negotiation and Configuration
              Modifications", RFC 6898, DOI 10.17487/RFC6898, March
              2013, <https://www.rfc-editor.org/info/rfc6898>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8309]  Wu, Q., Liu, W., and A. Farrel, "Service Models
              Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
              <https://www.rfc-editor.org/info/rfc8309>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.




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   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

   [TE-TUTORIAL]
              Bryskin, I., Beeram, V. P., Saad, T., and X. Liu, "TE
              Topology and Tunnel Modeling for Transport Networks", Work
              in Progress, Internet-Draft, draft-ietf-teas-te-topo-and-
              tunnel-modeling-06, 12 July 2020,
              <https://www.ietf.org/archive/id/draft-ietf-teas-te-topo-
              and-tunnel-modeling-06.txt>.

Appendix A.  Validating a JSON fragment against a YANG Model

   The objective is to have a tool that allows validating whether a
   piece of JSON code embedded in an Internet-Draft is compliant with a
   YANG model without using a client/server.

A.1.  JSON CODE

   This document provides some detailed JSON code examples to describe
   how the YANG models being developed by the IETF (TEAS and CCAMP WG in
   particular) may be used.  The scenario examples are provided using
   JSON to facilitate readability.

   Different objects need to have an identifier.  The convention used to
   create mnemonic identifiers is to use the object name (e.g., S3 for
   node S3), followed by its type (e.g., NODE), separated by a "-",
   followed by "-ID".  For example, the mnemonic identifier for AN1
   would be AN1-NODE-ID.

   The JSON language does not inherently support the insertion of
   comments.  This document will insert comments into the JSON code as
   JSON name/value pair with the JSON name string starting with the "//"
   characters.  For example, when describing the example of a TE
   Topology instance representing the ODU Abstract Topology exposed by
   the Transport PNC, the following comment has been added to the JSON
   code:

         "// comment": "ODU Abstract Topology @ MPI",

   The JSON code examples provided in this document have been validated
   against the YANG models following the validation process described in
   Appendix A, which would not consider the comments.






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   To have successful validation of the examples, some numbering scheme
   has been defined to assign identifiers to the different entities
   which would pass the syntax checks.  In that case, to simplify the
   reading, another JSON name/value pair formatted as a comment and
   using the mnemonic identifiers is also provided.  For example, the
   identifier of AN1 (AN1-NODE-ID) has been assumed to be "192.0.2.1"
   and would be shown in the JSON code example using the two JSON name/
   value pair:

         "// te-node-id": "AN1-NODE-ID",

         "te-node-id": "192.0.2.1",

   The first JSON name/value pair will be automatically removed in the
   first step of the validation process, while the second JSON name/
   value pair will be validated against the YANG model definitions.

A.2.  Manipulation of JSON fragments

   This section describes the various ways JSON fragments are used in
   the I-D processing and how to manage them.

   Let's call "folded-JSON" the JSON embedded in the I-D: it fits the 72
   chars width and it is acceptable for it to be invalid JSON.

   We then define "unfolded-JSON" a valid JSON fragment having the same
   contents of the "folded-JSON " without folding, i.e. limits on the
   text width.  The folding/unfolding operation may be done according to
   [RFC8792].  The "unfolded-JSON" can be edited by the authors using
   JSON editors with the advantages of syntax validation and pretty-
   printing.

   Both the "folded" and the "unfolded" JSON fragments can include
   comments having descriptive fields and directives we'll describe
   later to facilitate the reader and enable some automatic processing.

   The presence of comments in the "unfolded-JSON" fragment makes it an
   invalid JSON encoding of YANG data.  Therefore we call "naked JSON"
   the JSON where the comments have been stripped out: not only it is
   valid JSON but it is a valid JSON encoding of YANG data.

   The following schema resumes these definitions:









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                        unfold_it -->             stripper -->

              Folded-JSON           Unfolded-JSON             Naked JSON

                        <-- fold_it              <-- author edits

    <=72-chars?    must              may                      may

    valid JSON?     may             must                     must

    JSON-encoding
    of YANG data?   may              may                     must

   The validation toolchain has been designed to take a JSON in any of
   the three formats and validate it automatically against a set of
   relevant YANG modules using available open-source tools.

   The tool used to validate the JSON examples in this document can be
   found at: https://github.com/ietf-ccamp-wg/json-yang/tree/2.2

A.3.  Comments in JSON fragments

   We found it useful to introduce two kinds of comments, both defined
   as key-value pairs where the key starts with "//":

   *  free-form descriptive comments, e.g."// comment" : "refine this"
      to describe properties of JSON fragments.

   *  machine-usable directives e.g. "// header" : {"reference-drafts" :
      { "ietf-routing-types@2017-12-04": "rfc8294",}} which can be used
      to automatically download from the network the relevant I-Ds or
      RFCs and extract from them the YANG models of interest.  This is
      particularly useful to keep consistency when the drafting work is
      rapidly evolving.

A.4.  Validation of JSON fragments: DSDL-based approach

   The idea is to generate a JSON driver file (JTOX) from YANG, then use
   it to translate JSON to XML and validate it against the DSDL schemas,
   as shown in Figure 8.

   Useful link: https://github.com/mbj4668/pyang/wiki/XmlJson









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                              (2)
                  YANG-module ---> DSDL-schemas (RNG,SCH,DSRL)
                         |                  |
                         | (1)              |
                         |                  |
         Config/state  JTOX-file            | (4)
                \        |                  |
                 \       |                  |
                  \      V                  V
         JSON-file------------> XML-file ----------------> Output
                    (3)

           Figure 8: DSDL-based approach for JSON code validation

   In order to allow the use of comments following the convention
   defined in Section 3, without impacting the validation process, these
   comments will be automatically removed from the JSON-file that will
   be validated.

A.5.  Validation of JSON fragments: why not using an XSD-based approach

   This approach has been analyzed and discarded because no longer
   supported by pyang.

   The idea is to convert YANG to XSD, JSON to XML and validate it
   against the XSD, as shown in Figure 9:

                        (1)
            YANG-module ---> XSD-schema - \       (3)
                                           +--> Validation
            JSON-file------> XML-file ----/
                        (2)

           Figure 9: XSD-based approach for JSON code validation

   The pyang support for the XSD output format was deprecated in 1.5 and
   removed in 1.7.1.  However, pyang 1.7.1 is necessary to work with
   YANG 1.1 so the process shown in Figure 9 will stop just at step (1).

Appendix B.  Detailed JSON Examples

   The JSON code examples provided in this appendix have been validated
   using the tools in Appendix A and folded using the tool in [RFC8792].

B.1.  JSON Examples for Topology Abstractions






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B.1.1.  JSON Code: mpi1-otn-topology.json

   This is the JSON code reporting the OTN Topology @ MPI1:

   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   {
     "// header": {
       "last-update": "March 15, 2022",
       "title": "ODU Black Topology @ MPI1",
       "missing-attributes": true,
       "reference-drafts": {
         "ietf-routing-types@2017-12-04": "rfc8294",
         "ietf-te-types@2020-06-10": "rfc8776",
         "ietf-layer1-types@2021-02-19": "draft-ietf-ccamp-layer1-types\
   \-10",
         "ietf-network@2018-02-26": "rfc8345",
         "ietf-network-topology@2018-02-26": "rfc8345",
         "ietf-te-topology@2020-08-06": "rfc8795",
         "ietf-otn-topology@2021-07-08": "draft-ietf-ccamp-otn-topo-yan\
   \g-13"
       }
     },
     "ietf-network:networks": {
       "network": [
         {
           "network-id": "providerId/201/clientId/300/topologyId/otn-bl\
   \ack-topology",
           "network-types": {
             "ietf-te-topology:te-topology": {
               "ietf-otn-topology:otn-topology": {}
             }
           },
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 201,
             "client-id": 300,
             "topology-id": "otn-black-topology"
           },
           "// comment ietf-te-topology:te": "presence container requir\
   \es: provider-id, client-id and te-topology-id",
           "ietf-te-topology:te": {
             "name": "OTN Black Topology @ MPI1"
           },
           "ietf-network:node": [
             {
               "// node description": {
                 "name": "AN1",
                 "identifier": "192.0.2.1",



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                 "type": "Abstract Node",
                 "physical node(s)": "The whole network domain 1"
               },
               "node-id": "192.0.2.1",
               "ietf-te-topology:te-node-id": "192.0.2.1",
               "ietf-te-topology:te": {
                 "te-node-attributes": {
                   "name": "AN11",
                   "is-abstract": [
                     null
                   ],
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "tunnel-termination-point": [
                   {
                     "// comment tunnel-tp-id": "AN1-1 TTP-ID (1 -> 0x0\
   \1 -> 'AQ==' in base64)",
                     "tunnel-tp-id": "AQ==",
                     "name": "AN1-1 OTN TTP",
                     "// comment encoding and switching-capability": "O\
   \TN (ODU)",
                     "switching-capability": "ietf-te-types:switching-o\
   \tn",
                     "encoding": "ietf-te-types:lsp-encoding-oduk",
                     "// comment inter-layer-lock-id": "{ AN1-1 ILL-ID \
   \(1) }",
                     "inter-layer-lock-id": [
                       1
                     ],
                     "admin-status": "up",
                     "oper-status": "up"
                   },
                   {
                     "// comment tunnel-tp-id": "AN1-2 TTP-ID (2 -> 0x0\
   \2 -> 'Ag==' in base64)",
                     "tunnel-tp-id": "Ag==",
                     "name": "AN1-2 OTN TTP",
                     "// comment encoding and switching-capability": "O\
   \TN (ODU)",
                     "switching-capability": "ietf-te-types:switching-o\
   \tn",
                     "encoding": "ietf-te-types:lsp-encoding-oduk",
                     "// comment inter-layer-lock-id": "{ AN1-2 ILL-ID \
   \(2) }",
                     "inter-layer-lock-id": [
                       2
                     ],



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                     "admin-status": "up",
                     "oper-status": "up"
                   },
                   {
                     "// comment tunnel-tp-id": "AN1-3 TTP-ID (3 -> 0x0\
   \3 -> 'Awo=' in base64)",
                     "tunnel-tp-id": "Awo=",
                     "name": "AN1-3 OTN TTP",
                     "// comment encoding and switching-capability": "O\
   \TN (ODU)",
                     "switching-capability": "ietf-te-types:switching-o\
   \tn",
                     "encoding": "ietf-te-types:lsp-encoding-oduk",
                     "// comment inter-layer-lock-id": "{ AN1-3 ILL-ID \
   \(3) }",
                     "inter-layer-lock-id": [
                       3
                     ],
                     "admin-status": "up",
                     "oper-status": "up"
                   },
                   {
                     "// comment tunnel-tp-id": "AN1-8 TTP-ID (8 -> 0x0\
   \8 -> 'CA==' in base64)",
                     "tunnel-tp-id": "CA==",
                     "name": "AN1-8 OTN TTP",
                     "// comment encoding and switching-capability": "O\
   \TN (ODU)",
                     "switching-capability": "ietf-te-types:switching-o\
   \tn",
                     "encoding": "ietf-te-types:lsp-encoding-oduk",
                     "// comment inter-layer-lock-id": "{ AN1-8 ILL-ID \
   \(1) }",
                     "inter-layer-lock-id": [
                       8
                     ],
                     "admin-status": "up",
                     "oper-status": "up"
                   }
                 ]
               },
               "ietf-network-topology:termination-point": [
                 {
                   "// ltp description": {
                     "name": "AN1-1 LTP",
                     "link type(s)": "Multi-function (OTU2, STM-64 and \
   \10GE)",
                     "physical node": "S3",



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                     "unnumberd/ifIndex": 1,
                     "port type": "tributary port",
                     "connected to": "R1"
                   },
                   "tp-id": "1",
                   "ietf-te-topology:te-tp-id": 1,
                   "ietf-te-topology:te": {
                     "name": "AN1-1 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\
   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,
                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU2"
                               }
                             }
                           }
                         ]
                       }
                     ],
                     "// not-present inter-domain-plug-id": "Use of plu\
   \g-id for access Link is outside the scope of this document",
                     "// comment inter-layer-lock-id": "{ AN1-1 ILL-ID \
   \(1) }",
                     "inter-layer-lock-id": [
                       1
                     ],
                     "admin-status": "up",
                     "oper-status": "up",
                     "ietf-otn-topology:client-svc": {
                       "client-facing": true,
                       "supported-client-signal": [
                         "ietf-layer1-types:STM-64"
                       ]
                     }
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-2 LTP",
                     "link type(s)": "Multi-function (OTU2 and STM-64)"\



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   \,
                     "physical node": "S6",
                     "unnumberd/ifIndex": 2,
                     "port type": "tributary port",
                     "connected to": "R3"
                   },
                   "tp-id": "2",
                   "ietf-te-topology:te-tp-id": 2,
                   "ietf-te-topology:te": {
                     "name": "AN1-2 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\
   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,
                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU2"
                               }
                             }
                           }
                         ]
                       }
                     ],
                     "// not-present inter-domain-plug-id": "Use of plu\
   \g-id for access Link is outside the scope of this document",
                     "// comment inter-layer-lock-id": "{ AN1-2 ILL-ID \
   \(2) }",
                     "inter-layer-lock-id": [
                       2
                     ],
                     "admin-status": "up",
                     "oper-status": "up",
                     "ietf-otn-topology:client-svc": {
                       "client-facing": true,
                       "supported-client-signal": [
                         "ietf-layer1-types:STM-64"
                       ]
                     }
                   }
                 },
                 {
                   "// ltp description": {



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                     "name": "AN1-3 LTP",
                     "link type(s)": "STM-64",
                     "physical node": "S6",
                     "unnumberd/ifIndex": 3,
                     "port type": "tributary port",
                     "connected to": "R4"
                   },
                   "tp-id": "3",
                   "ietf-te-topology:te-tp-id": 3,
                   "ietf-te-topology:te": {
                     "name": "AN1-3 LTP",
                     "// not-present interface-switching-capability": "\
   \STM-64 Access Link only (no ODU switching)",
                     "// not-present inter-domain-plug-id": "Use of plu\
   \g-id for access Link is outside the scope of this document",
                     "// comment inter-layer-lock-id": "{ AN1-3 ILL-ID \
   \(3) }",
                     "inter-layer-lock-id": [
                       3
                     ],
                     "admin-status": "up",
                     "oper-status": "up",
                     "ietf-otn-topology:client-svc": {
                       "client-facing": true,
                       "supported-client-signal": [
                         "ietf-layer1-types:STM-64"
                       ]
                     }
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-4 LTP",
                     "link type(s)": "OTU4",
                     "physical node": "S7",
                     "unnumberd/ifIndex": 3,
                     "port type": "inter-domain port",
                     "connected to": "S11"
                   },
                   "tp-id": "4",
                   "ietf-te-topology:te-tp-id": 4,
                   "ietf-te-topology:te": {
                     "name": "AN1-4 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\



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   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,
                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU4"
                               }
                             }
                           }
                         ]
                       }
                     ],
                     "// comment inter-domain-plug-id": "S7-S11 Plug-id\
   \ (0x000711 -> AAcR)",
                     "inter-domain-plug-id": "AAcR",
                     "// not-present inter-layer-lock-id": "ODU Server \
   \Layer topology not exposed",
                     "admin-status": "up",
                     "oper-status": "up",
                     "// not-present ietf-otn-topology:client-svc": "OT\
   \N inter-domain link"
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-5 LTP",
                     "link type(s)": "OTU4",
                     "physical node": "S8",
                     "unnumberd/ifIndex": 4,
                     "port type": "inter-domain port",
                     "connected to": "S12"
                   },
                   "tp-id": "5",
                   "ietf-te-topology:te-tp-id": 5,
                   "ietf-te-topology:te": {
                     "name": "AN1-5 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\
   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,



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                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU4"
                               }
                             }
                           }
                         ]
                       }
                     ],
                     "// comment inter-domain-plug-id": "S8-S12 Plug-id\
   \ (0x000812 -> AAgS)",
                     "inter-domain-plug-id": "AAgS",
                     "// not-present inter-layer-lock-id": "ODU Server \
   \Layer topology not exposed",
                     "admin-status": "up",
                     "oper-status": "up",
                     "// not-present ietf-otn-topology:client-svc": "OT\
   \N inter-domain link"
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-6 LTP",
                     "link type(s)": "OTU4",
                     "physical node": "S8",
                     "unnumberd/ifIndex": 5,
                     "port type": "inter-domain port",
                     "connected to": "S32"
                   },
                   "tp-id": "6",
                   "ietf-te-topology:te-tp-id": 6,
                   "ietf-te-topology:te": {
                     "name": "AN1-6 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\
   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,
                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU4"
                               }
                             }



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                           }
                         ]
                       }
                     ],
                     "// comment inter-domain-plug-id": "S8-S32 Plug-id\
   \ (0x000832 -> AAgy)",
                     "inter-domain-plug-id": "AAgy",
                     "// not-present inter-layer-lock-id": "ODU Server \
   \Layer topology not exposed",
                     "admin-status": "up",
                     "oper-status": "up",
                     "// not-present ietf-otn-topology:client-svc": "OT\
   \N inter-domain link"
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-7 LTP",
                     "link type(s)": "OTU4",
                     "physical node": "S2",
                     "unnumberd/ifIndex": 3,
                     "port type": "inter-domain port",
                     "connected to": "S31"
                   },
                   "tp-id": "7",
                   "ietf-te-topology:te-tp-id": 7,
                   "ietf-te-topology:te": {
                     "name": "AN1-7 LTP",
                     "interface-switching-capability": [
                       {
                         "// comment encoding and switching-capability"\
   \: "OTN (ODU)",
                         "switching-capability": "ietf-te-types:switchi\
   \ng-otn",
                         "encoding": "ietf-te-types:lsp-encoding-oduk",
                         "max-lsp-bandwidth": [
                           {
                             "priority": 0,
                             "te-bandwidth": {
                               "ietf-otn-topology:otn": {
                                 "odu-type": "ietf-layer1-types:ODU4"
                               }
                             }
                           }
                         ]
                       }
                     ],
                     "// comment inter-domain-plug-id": "S2-S31 Plug-id\



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   \ (0x000231 -> AAIx)",
                     "inter-domain-plug-id": "AAIx",
                     "// not-present inter-layer-lock-id": "ODU Server \
   \Layer topology not exposed",
                     "admin-status": "up",
                     "oper-status": "up",
                     "// not-present ietf-otn-topology:client-svc": "OT\
   \N inter-domain link"
                   }
                 }
               ]
             }
           ],
           "ietf-network-topology:link": [
             {
               "// link description": {
                 "name": "Access Link from AN1-1",
                 "type": "Multi-function access link (OTU2, STM-64 and \
   \10GE)",
                 "physical link": "Link from S3-1 to R1"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/1",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "1"
               },
               "// not-present destination": "access link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Access Link from AN1-1",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\
   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU4"
                             }



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                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 1
                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 1
                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 1
                           }
                         ]
                       }
                     }
                   ],
                   "// not-present ietf-otn-topology:tsg": "Access Link\
   \ with no HO-ODU termination and LO-ODU switching",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }



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             },
             {
               "// link description": {
                 "name": "Access Link from AN1-2",
                 "type": "Multi-function access link (OTU2 and STM-64)"\
   \,
                 "physical link": "Link from S6-2 to R3"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/2",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "2"
               },
               "// not-present destination": "access link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Access Link from AN1-2",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\
   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU2"
                             }
                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 1



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                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 1
                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 1
                           }
                         ]
                       }
                     }
                   ],
                   "// not-present ietf-otn-topology:tsg": "Access Link\
   \ with no HO-ODU termination and LO-ODU switching",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Access Link from AN1-3",
                 "type": "STM-64 Access link",
                 "physical link": "Link from S6-3 to R4"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/3",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "3"
               },
               "// not-present destination": "access link",



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               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Access Link from AN1-3",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "// not-present interface-switching-capability": "ST\
   \M-64 Access Link only (no ODU switching)",
                   "// not-present max-link-bandwidth": "STM-64 Access \
   \Link only (no ODU switching)",
                   "// not-present max-resv-link-bandwidth": "STM-64 Ac\
   \cess Link only (no ODU switching)",
                   "// not-present unreserved-bandwidth": "STM-64 Acces\
   \s Link only (no ODU switching)",
                   "// not-present ietf-otn-topology:tsg": "STM-64 Acce\
   \ss Link only (no HO-ODU termination and LO-ODU switching)",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Inter-domain Link from AN1-4",
                 "type": "OTU4 inter-domain link",
                 "physical link": "Link from S7-3 to S11"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/4",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "4"
               },
               "// not-present destination": "inter-domain link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Inter-domain Link from AN1-4",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\



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   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU2"
                             }
                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80



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                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU4",
                             "number": 1
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 10
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU0",
                             "number": 80
                           }
                         ]
                       }
                     }
                   ],
                   "ietf-otn-topology:tsg": "ietf-layer1-types:tsg-1.25\
   \G",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Inter-domain Link from AN1-5",
                 "type": "OTU4 inter-domain link",
                 "physical link": "Link from S8-4 to S12"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/5",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "5"
               },
               "// not-present destination": "inter-domain link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {



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                   "name": "Inter-domain Link from AN1-5",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\
   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU4"
                             }
                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {



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                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU4",
                             "number": 1
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 10
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU0",
                             "number": 80
                           }
                         ]
                       }
                     }
                   ],
                   "ietf-otn-topology:tsg": "ietf-layer1-types:tsg-1.25\
   \G",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Inter-domain Link from AN1-6",
                 "type": "OTU4 inter-domain link",



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                 "physical link": "Link from S8-5 to S32"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/6",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "6"
               },
               "// not-present destination": "inter-domain link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Inter-domain Link from AN1-6",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\
   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU4"
                             }
                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {



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                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU4",
                             "number": 1
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 10
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU0",
                             "number": 80
                           }
                         ]
                       }
                     }
                   ],
                   "ietf-otn-topology:tsg": "ietf-layer1-types:tsg-1.25\
   \G",
                   "admin-status": "up"



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                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Inter-domain Link from AN1-7",
                 "type": "OTU4 inter-domain link",
                 "physical link": "Link from S2-3 to S31"
               },
               "link-id": "teNodeId/192.0.2.1teLinkId/7",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "7"
               },
               "// not-present destination": "inter-domain link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Inter-domain Link from AN1-7",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "interface-switching-capability": [
                     {
                       "// comment encoding and switching-capability": \
   \"OTN (ODU)",
                       "switching-capability": "ietf-te-types:switching\
   \-otn",
                       "encoding": "ietf-te-types:lsp-encoding-oduk",
                       "max-lsp-bandwidth": [
                         {
                           "priority": 0,
                           "te-bandwidth": {
                             "ietf-otn-topology:otn": {
                               "odu-type": "ietf-layer1-types:ODU4"
                             }
                           }
                         }
                       ]
                     }
                   ],
                   "// comment label-restrictions": "Outside the scope \
   \of this JSON example",
                   "max-link-bandwidth": {
                     "te-bandwidth": {



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                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "max-resv-link-bandwidth": {
                     "te-bandwidth": {
                       "ietf-otn-topology:odulist": [
                         {
                           "odu-type": "ietf-layer1-types:ODU4",
                           "number": 1
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU2",
                           "number": 10
                         },
                         {
                           "odu-type": "ietf-layer1-types:ODU0",
                           "number": 80
                         }
                       ]
                     }
                   },
                   "unreserved-bandwidth": [
                     {
                       "priority": 0,
                       "te-bandwidth": {
                         "ietf-otn-topology:odulist": [
                           {
                             "odu-type": "ietf-layer1-types:ODU4",
                             "number": 1
                           },
                           {
                             "odu-type": "ietf-layer1-types:ODU2",
                             "number": 10
                           },
                           {



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                             "odu-type": "ietf-layer1-types:ODU0",
                             "number": 80
                           }
                         ]
                       }
                     }
                   ],
                   "ietf-otn-topology:tsg": "ietf-layer1-types:tsg-1.25\
   \G",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             }
           ]
         }
       ]
     }
   }

B.1.2.  JSON Code: mpi1-eth-topology.json

   This is the JSON code reporting the ETH Topology @ MPI1:

   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   {
     "// header": {
       "last-update": "March 15, 2022",
       "title": "ETH Black Topology @ MPI1",
       "reference-drafts": {
         "ietf-routing-types@2017-12-04": "rfc8294",
         "ietf-te-types@2020-06-10": "rfc8776",
         "ietf-network@2018-02-26": "rfc8345",
         "ietf-network-topology@2018-02-26": "rfc8345",
         "ietf-te-topology@2020-08-06": "rfc8795",
         "ietf-eth-tran-types@2021-07-07": "draft-ietf-ccamp-client-sig\
   \nal-yang-05",
         "ietf-eth-te-topology@2019-11-18": "draft-ietf-ccamp-eth-clien\
   \t-te-topo-yang-00"
       }
     },
     "ietf-network:networks": {
       "network": [
         {
           "network-id": "providerId/201/clientId/300/topologyId/eth-bl\



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   \ack-topology",
           "network-types": {
             "ietf-te-topology:te-topology": {
               "ietf-eth-te-topology:eth-tran-topology": {}
             }
           },
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 201,
             "client-id": 300,
             "topology-id": "eth-black-topology"
           },
           "// comment ietf-te-topology:te": "presence container requir\
   \es: provider-id, client-id and te-topology-id",
           "ietf-te-topology:te": {
             "name": "ETH Black Topology @ MPI1"
           },
           "ietf-network:node": [
             {
               "// node description": {
                 "name": "AN1",
                 "identifier": "192.0.2.1",
                 "type": "Abstract Node",
                 "physical node(s)": "The whole network domain 1"
               },
               "node-id": "192.0.2.1",
               "ietf-te-topology:te-node-id": "192.0.2.1",
               "// comment supporting-node": "Not used because topology\
   \ hierarchy is outside the scope of this JSON example",
               "ietf-te-topology:te": {
                 "te-node-attributes": {
                   "name": "AN11",
                   "is-abstract": [
                     null
                   ],
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present tunnel-termination-point": "ETH Access\
   \ Links only (no ETH TE switching)"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "// ltp description": {
                     "name": "AN1-1 LTP",
                     "link type(s)": "Multi-function (OTU2, STM-64 and \
   \10GE)",
                     "physical node": "S3",
                     "unnumberd/ifIndex": 1,



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                     "port type": "tributary port",
                     "connected to": "R1"
                   },
                   "tp-id": "1",
                   "ietf-te-topology:te-tp-id": 1,
                   "ietf-te-topology:te": {
                     "name": "AN1-1 LTP",
                     "// not-present interface-switching-capability": "\
   \ETH Access Link only (no ETH TE switching)",
                     "// comment inter-domain-plug-id": "Use of plug-id\
   \ for access Link is outside the scope of this document",
                     "// comment inter-layer-lock-id": "AN1-1 ILL-ID (1\
   \)",
                     "inter-layer-lock-id": [
                       1
                     ],
                     "admin-status": "up",
                     "oper-status": "up"
                   },
                   "// comment ietf-eth-te-topology:ingress-bandwidth-p\
   \rofile": "Outside the scope of this JSON example",
                   "ietf-eth-te-topology:eth-svc": {
                     "client-facing": true,
                     "supported-classification": {
                       "port-classification": true,
                       "vlan-classification": {
                         "vlan-tag-classification": true,
                         "outer-tag": {
                           "supported-tag-types": [
                             "ietf-eth-tran-types:classify-c-vlan"
                           ],
                           "vlan-range": "1-4094"
                         }
                       }
                     },
                     "supported-vlan-operations": {
                       "transparent-vlan-operations": true
                     }
                   }
                 },
                 {
                   "// ltp description": {
                     "name": "AN1-8 LTP",
                     "link type(s)": "10GE",
                     "physical node": "S6",
                     "unnumberd/ifIndex": 1,
                     "port type": "tributary port",
                     "connected to": "R2"



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                   },
                   "tp-id": "8",
                   "ietf-te-topology:te-tp-id": 8,
                   "ietf-te-topology:te": {
                     "name": "AN1-8 LTP",
                     "// comment inter-layer-lock-id": "AN1-8 ILL-ID (8\
   \)",
                     "// not-present interface-switching-capability": "\
   \ETH Access Link only (no ETH TE switching)",
                     "// comment inter-domain-plug-id": "Use of plug-id\
   \ for access Link is outside the scope of this document",
                     "inter-layer-lock-id": [
                       8
                     ],
                     "admin-status": "up",
                     "oper-status": "up"
                   },
                   "// comment ingress-bandwidth-profile": "Outside the\
   \ scope of this JSON example",
                   "ietf-eth-te-topology:eth-svc": {
                     "client-facing": true,
                     "supported-classification": {
                       "port-classification": true,
                       "vlan-classification": {
                         "vlan-tag-classification": true,
                         "outer-tag": {
                           "supported-tag-types": [
                             "ietf-eth-tran-types:classify-c-vlan"
                           ],
                           "vlan-range": "1-4094"
                         }
                       }
                     },
                     "supported-vlan-operations": {
                       "transparent-vlan-operations": true
                     }
                   }
                 }
               ]
             }
           ],
           "ietf-network-topology:link": [
             {
               "// link description": {
                 "name": "Access Link from AN1-1",
                 "type": "Multi-function access link (OTU2, STM-64 and \
   \10GE)",
                 "physical link": "Link from S3-1 to R1"



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               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/1",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "1"
               },
               "// not-present destination": "access link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Access Link from AN1-1",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",
                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "// not-present interface-switching-capability": "ET\
   \H Access Link only (no ETH TE switching)",
                   "// not-present label-restrictions": "ETH Access Lin\
   \k only (no ETH TE switching)",
                   "// not-present max-link-bandwidth": "ETH Access Lin\
   \k only (no ETH TE switching)",
                   "// not-present max-resv-link-bandwidth": "ETH Acces\
   \s Link only (no ETH TE switching)",
                   "// not-present unreserved-bandwidth": "ETH Access L\
   \ink only (no ETH TE switching)",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             },
             {
               "// link description": {
                 "name": "Access Link from AN1-8",
                 "type": "10GE access link",
                 "physical link": "Link from S6-1 to R2"
               },
               "link-id": "teNodeId/192.0.2.1/teLinkId/8",
               "source": {
                 "source-node": "192.0.2.1",
                 "source-tp": "8"
               },
               "// not-present destination": "access link",
               "ietf-te-topology:te": {
                 "te-link-attributes": {
                   "name": "Access Link from AN1-8",
                   "// not-present external-domain": "The plug-id is us\
   \ed instead of this container",



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                   "// not-present is-abstract": "The access link is no\
   \t abstract",
                   "// not-present interface-switching-capability": "ET\
   \H Access Link only (no ETH TE switching)",
                   "// not-present label-restrictions": "ETH Access Lin\
   \k only (no ETH TE switching)",
                   "// not-present max-link-bandwidth": "ETH Access Lin\
   \k only (no ETH TE switching)",
                   "// not-present max-resv-link-bandwidth": "ETH Acces\
   \s Link only (no ETH TE switching)",
                   "// not-present unreserved-bandwidth": "ETH Access L\
   \ink only (no ETH TE switching)",
                   "admin-status": "up"
                 },
                 "oper-status": "up",
                 "// not-present is-transitional": "It is not a transit\
   \ional link"
               }
             }
           ]
         }
       ]
     }
   }

B.2.  JSON Examples for Service Configuration

B.2.1.  JSON Code: mpi1-odu2-service-config.json

   This is the JSON code reporting the ODU2 transit service
   configuration @ MPI1:

   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   {
     "// header": {
       "// last-update": "March 15, 2022",
       "// title": "ODU2 Service Configuration @ MPI1",
       "reference-drafts": {
       "ietf-routing-types@2017-12-04": "rfc8294",
       "ietf-te-types@2020-06-10": "rfc8776",
       "ietf-layer1-types@2021-02-19": "draft-ietf-ccamp-layer1-types-1\
   \0",
       "ietf-te@2021-02-20": "draft-ietf-teas-yang-te-26",
       "ietf-otn-tunnel@2021-06-25": "draft-ietf-ccamp-otn-tunnel-model\
   \-14"
       }
     },



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     "// missing-attributes": true,
     "// restconf_operation": {
       "operation": "POST",
       "url": "http://{{PNC1-ADDR}}/restconf/data/ietf-te:te/tunnels"
     },
     "ietf-te:te": {
       "tunnels": {
         "tunnel": [
           {
             "name": "mpi1-odu2-service",
             "// comment identifier": "ODU2-SERVICE-TUNNEL-ID @ MPI1",
             "identifier": 1,
             "description": "ODU2 Service implemented by ODU2 OTN Tunne\
   \l Segment @ MPI1",
             "// comment encoding and switching-type": "OTN (ODU)",
             "encoding": "ietf-te-types:lsp-encoding-oduk",
             "switching-type": "ietf-te-types:switching-otn",
             "// not-present source": "Transit tunnel segment",
             "// not-present src-tunnel-tp-id": "Transit tunnel segment\
   \",
             "// not-present destination": "Transit tunnel segment",
             "// not-present dst-tunnel-tp-id": "Transit tunnel segment\
   \",
             "bidirectional": true,
             "// default protection": {
               "// default enable": false
             },
             "// default restoration": {
               "// default enable": false
             },
             "// comment te-topology-identifier": "ODU Black Topology @\
   \ MPI1",
             "te-topology-identifier": {
               "provider-id": 201,
               "client-id": 300,
               "topology-id": "otn-black-topology"
             },
             "te-bandwidth": {
               "ietf-otn-tunnel:otn": {
                 "ietf-otn-tunnel:odu-type": "ietf-layer1-types:ODU2"
               }
             },
             "admin-state": "ietf-te-types:tunnel-admin-state-up",
             "primary-paths": {
               "primary-path": [
                 {
                   "name": "mpi1-odu2-service-primary-path",
                   "// not-present te-bandwidth": "The tunnel bandwidth\



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   \ is used",
                   "explicit-route-objects-always": {
                     "route-object-include-exclude": [
                       {
                         "// comment": "Tunnel hand-off OTU2 ingress in\
   \terface (S3-1 -> AN1-1)",
                         "index": 1,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "unnumbered-link-hop": {
                           "// comment node-id": "AN1 NODE-ID",
                           "node-id": "192.0.2.1",
                           "// comment link-tp-id": "AN1-1 LTP",
                           "link-tp-id": 1,
                           "// default hop-type": "strict",
                           "// default direction": "outgoing"
                         }
                       },
                       {
                         "// comment": "Tunnel hand-off ODU2 ingress la\
   \bel (ODU2 over OTU2) at S3-1 (AN1-1)",
                         "index": 2,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "label-hop": {
                           "te-label": {
                             "ietf-otn-tunnel:otn-tpn": 1,
                             "// not-present ietf-otn-tunnel:tsg": "Not\
   \ applicable for ODUk over OTUk",
                             "// not-present ietf-otn-tunnel:ts-list": \
   \"Not applicable for ODUk over OTUk",
                             "// default direction": "forward"
                           }
                         }
                       },
                       {
                         "// comment": "Tunnel hand-off OTU4 egress int\
   \erface (S2-3 -> AN1-7)",
                         "index": 3,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "unnumbered-link-hop": {
                           "// comment node-id": "AN1 Node",
                           "node-id": "192.0.2.1",
                           "// comment link-tp-id": "AN1-7 LTP",
                           "link-tp-id": 7,
                           "// default hop-type": "strict",
                           "// default direction": "outgoing"



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                         }
                       },
                       {
                         "// comment": "Tunnel hand-off ODU2 egress lab\
   \el (ODU2 over OTU4) at S2-3 (AN1-7)",
                         "index": 4,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "label-hop": {
                           "te-label": {
                             "ietf-otn-tunnel:otn-tpn": 1,
                             "ietf-otn-tunnel:tsg": "ietf-layer1-types:\
   \tsg-1.25G",
                             "ietf-otn-tunnel:ts-list": "1-8",
                             "// default direction": "forward"
                           }
                         }
                       }
                     ]
                   }
                 }
               ]
             }
           }
         ]
       }
     }
   }

B.2.2.  JSON Code: mpi1-odu2-tunnel-config.json

   This is the JSON code reporting the ODU2 head tunnel segment
   configuration @ MPI1:

   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   {
     "// header": {
       "last-update": "March 15, 2022",
       "title": "ODU2 Tunnel Configuration @ MPI1",
       "reference-drafts": {
         "ietf-routing-types@2017-12-04": "rfc8294",
         "ietf-te-types@2020-06-10": "rfc8776",
         "ietf-layer1-types@2021-02-19": "draft-ietf-ccamp-layer1-types\
   \-10",
         "ietf-te@2021-02-20": "draft-ietf-teas-yang-te-26",
         "ietf-otn-tunnel@2021-06-25": "draft-ietf-ccamp-otn-tunnel-mod\
   \el-14"



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     },
       "// missing-attributes": true,
       "// restconf-operation": {
         "operation": "POST",
         "url": "http://{{PNC1-ADDR}}/restconf/data/ietf-te:te/tunnels"
       }
     },
     "ietf-te:te": {
       "tunnels": {
         "tunnel": [
           {
             "name": "mpi1-odu2-tunnel",
             "// comment identifier": "ODU2-TUNNEL-ID @ MPI1",
             "identifier": 2,
             "description": "TNBI Example for an ODU2 Head Tunnel Segme\
   \nt @ MPI1",
             "// comment encoding and switching-type": "OTN (ODU)",
             "encoding": "ietf-te-types:lsp-encoding-oduk",
             "switching-type": "ietf-te-types:switching-otn",
             "// comment source": "AN1 Node-ID",
             "source": "192.0.2.1",
             "// comment src-tunnel-tp-id": "AN1-1 TTP-ID (1 -> 0x01 ->\
   \ 'AQ==' in base64)",
             "src-tunnel-tp-id": "AQ==",
             "// not-present destination": "Head tunnel segment",
             "// not-present dst-tunnel-tp-id": "Head tunnel segment",
             "bidirectional": true,
             "// default protection": {
               "// default enable": false
             },
             "// default restoration": {
               "// default enable": false
             },
             "// comment te-topology-identifier": "ODU Black Topology @\
   \ MPI1",
             "te-topology-identifier": {
               "provider-id": 201,
               "client-id": 300,
               "topology-id": "otn-black-topology"
             },
             "te-bandwidth": {
               "ietf-otn-tunnel:otn": {
                 "ietf-otn-tunnel:odu-type": "ietf-layer1-types:ODU2"
               }
             },
             "admin-state": "ietf-te:tunnel-admin-auto",
             "primary-paths": {
               "primary-path": [



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                 {
                   "name": "mpi1-odu2-tunnel-primary-path",
                   "// not-present te-bandwidth": "The tunnel bandwidth\
   \ is used",
                   "explicit-route-objects-always": {
                     "route-object-include-exclude": [
                       {
                         "// comment": "Tunnel hand-off OTU4 egress int\
   \erface (AN1-7 LTP)",
                         "index": 1,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "unnumbered-link-hop": {
                           "// comment node-id": "AN1 NODE-ID",
                           "node-id": "192.0.2.1",
                           "// comment link-tp-id": "AN1-7 LTP-ID",
                           "link-tp-id": 7,
                           "// default hop-type": "strict",
                           "// default direction": "outgoing"
                         }
                       },
                       {
                         "// comment": "Tunnel hand-off ODU2 egress lab\
   \el (ODU2 over OTU4)",
                         "index": 2,
                         "explicit-route-usage": "ietf-te-types:route-i\
   \nclude-object",
                         "label-hop": {
                           "te-label": {
                             "ietf-otn-tunnel:otn-tpn": 2,
                             "ietf-otn-tunnel:tsg": "ietf-layer1-types:\
   \tsg-1.25G",
                             "ietf-otn-tunnel:ts-list": "9-16",
                             "// default direction": "forward"
                           }
                         }
                       }
                     ]
                   }
                 }
               ]
             }
           }
         ]
       }
     }
   }




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B.2.3.  JSON Code: mpi1-epl-service-config.json

   This is the JSON code reporting the EPL service configuration @ MPI:

   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   {
     "// header": {
       "last-update": "March 15, 2022",
       "title": "EPL Configuration @ MPI1",
       "reference-drafts": {
         "ietf-routing-types@2017-12-04": "rfc8294",
         "ietf-te@2021-05-16": "draft-ietf-teas-yang-te-27",
         "ietf-te-types@2020-06-10": "rfc8776",
         "ietf-eth-tran-types@2021-07-07": "draft-ietf-ccamp-client-sig\
   \nal-yang-05",
         "ietf-eth-tran-service@2021-01-11": "draft-ietf-ccamp-client-s\
   \ignal-yang-05"
       },
       "missing-attributes": true,
       "restconf-operation": {
         "operation": "POST",
         "url": "http://{{PNC1-ADDR}}/restconf/data/ietf-eth-tran-servi\
   \ce:etht-svc/etht-svc-instances"
       }
     },
     "ietf-eth-tran-service:etht-svc": {
       "etht-svc-instances": [
         {
           "etht-svc-name": "mpi1-epl-service",
           "etht-svc-descr": "TNBI Example for an EPL over ODU2 Service\
   \ @ MPI1",
           "// default etht-svc-type": "ietf-eth-tran-types:p2p-svc",
           "// comment te-topology-identifier": "ETH Black Topology @ M\
   \PI1",
           "te-topology-identifier": {
             "provider-id": 201,
             "client-id": 300,
             "topology-id": "eth-black-topology"
           },
           "etht-svc-end-points": [
             {
               "// comment": "10GE Service End-Point at the access inte\
   \rface (S3-1 -> AN1-1)",
               "etht-svc-end-point-name": "mpi1-epl-an1-1-service-end-p\
   \oint",
               "etht-svc-end-point-descr": "Ethernet Service End-Point \
   \at S3-1 (AN1-1) access link",



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               "etht-svc-access-points": [
                 {
                   "// comment": "10GE Service Access Point at the acce\
   \ss interface (S3-1 -> AN1-1)",
                   "access-point-id": "mpi-epl-an1-1-service-access-poi\
   \nt",
                   "// comment access-node-id": "AN1 NODE-ID",
                   "access-node-id": "192.0.2.1",
                   "// comment access-ltp-id": "AN1-1 LTP-ID",
                   "access-ltp-id": 1
                 }
               ],
               "service-classification-type": "ietf-eth-tran-types:port\
   \-classification",
               "// comment ingress-egress-bandwidth-profile": "Outside \
   \the scope of this JSON example",
               "// comment not present vlan-operations": "Transparent V\
   \LAN operations"
             }
           ],
           "underlay": {
             "otn-tunnels": [
               {
                 "// comment tunnel-name": "ODU2 Head Tunnel Segment @ \
   \MPI1",
                 "name": "mpi1-odu2-tunnel"
               }
             ]
           },
           "admin-status": "ietf-te-types:tunnel-admin-state-up"
         }
       ]
     }
   }

Acknowledgments

   The authors would like to thank all members of the Transport NBI
   Design Team involved in the definition of use cases, gap analysis and
   guidelines for using the IETF YANG models at the Northbound Interface
   (NBI) of a Transport SDN Controller.

   The authors would like to thank Xian Zhang, Anurag Sharma, Sergio
   Belotti, Tara Cummings, Michael Scharf, Karthik Sethuraman, Oscar
   Gonzalez de Dios, and Hans Bjursrom for having initiated the work on
   gap analysis for transport NBI and having provided foundations work
   for the development of this document.




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   The authors would like to thank the authors of the TE Topology and
   Tunnel YANG models [RFC8795] and [TE-TUNNEL], in particular, Igor
   Bryskin, Vishnu Pavan Beeram, Tarek Saad and Xufeng Liu, for their
   support in addressing any gap identified during the analysis work.

   The authors would like to thank Henry Yu and Aihua Guo for their
   input and review of the URIs structures used within the JSON code
   examples.

   This work was supported in part by the European Commission funded
   H2020-ICT-2016-2 METRO-HAUL project (G.A. 761727).

   This document was prepared using kramdown.

   Previous versions of this document was prepared using 2-Word-
   v2.0.template.dot.

Contributors

   Yang Zhao
   China Mobile
   Email: zhaoyangyjy@chinamobile.com


   Sergio Belotti
   Nokia
   Email: sergio.belotti@nokia.com


   Gianmarco Bruno
   Ericsson
   Email: gianmarco.bruno@ericsson.com


   Young Lee
   Sung Kyun Kwan University
   Email: younglee.tx@gmail.com


   Victor Lopez
   Nokia
   Email: victor.lopez@nokia.com


   Carlo Perocchio
   Ericsson
   Email: carlo.perocchio@ericsson.com




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Internet-Draft    Transport NBI Applicability-Statement       March 2022


   Ricard Vilalta
   CTTC
   Email: ricard.vilalta@cttc.es


   Michael Scharf
   Hochschule Esslingen - University of Applied Sciences
   Email: michael.scharf@hs-esslingen.de


   Dieter Beller
   Nokia
   Email: dieter.beller@nokia.com


Authors' Addresses

   Italo Busi (editor)
   Huawei
   Email: italo.busi@huawei.com


   Daniel King (editor)
   Old Dog Consulting
   Email: daniel@olddog.co.uk


   Haomian Zheng (editor)
   Huawei
   Email: zhenghaomian@huawei.com


   Yunbin Xu (editor)
   CAICT
   Email: xuyunbin@ritt.cn
















Busi, et al.            Expires 26 September 2022              [Page 91]