[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01

TEAS Working Group                                         Igor Bryskin
Internet Draft                                      Huawei Technologies
Intended status: Informational                      Vishnu Pavan Beeram
                                                       Juniper Networks
                                                             Tarek Saad
                                                      Cisco Systems Inc
                                                             Xufeng Liu
                                                                  Jabil





Expires: April 23, 2017                                October 23, 2017


          TE Topology and Tunnel Modeling for Transport Networks
             draft-bryskin-teas-te-topo-and-tunnel-modeling-01


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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 23, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors. All rights reserved.






Bryskin, et al.         Expires April 23, 2018                 [Page 1]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Abstract

   This document describes how to model TE topologies and tunnels for
   transport networks, by using the TE topology YANG model [I-D.ietf-
   teas-yang-te-topo] and the TE tunnel YANG model [I-D.ietf-teas-yang-
   te].

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].


Table of Contents

   1. Modeling Considerations........................................3
      1.1. TE Topology Model.........................................3
      1.2. TE Topology Modeling Constructs...........................5
      1.3. Abstract TE Topology Calculation, Configuration and
      Maintenance...................................................22
         1.3.1. Single-Node Abstract TE Topology....................24
         1.3.2. Full Mesh Link Abstract TE Topology.................26
         1.3.3. Star-n-Spokes Abstract TE Topology..................28
         1.3.4. Arbitrary Abstract TE Topology......................29
         1.3.5. Customized Abstract TE Topologies...................30
         1.3.6. Hierarchical Abstract TE Topologies.................31
      1.4. Merging TE Topologies Provided By Multiple Providers.....32
         1.4.1. Dealing With Multiple Abstract TE Topologies Provided By
         The Same Provider..........................................35
      1.5. Configuring Abstract TE Topologies.......................37
      1.6. TE Tunnel Model..........................................38
      1.7. TE Tunnel/Transport Service Modeling Constructs..........40
      1.8. Transport Service Mapping................................53
      1.9. Multi-Domain Transport Service Coordination..............54
   2. Use Cases.....................................................58



Bryskin, et al.         Expires April 23, 2018                 [Page 2]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


      2.1. Use Case 1. Transport service control on a single layer
      multi-domain transport network................................58
      2.2. Use Case 2. End-to-end TE tunnel control on a single layer
      multi-domain transport network................................66
      2.3. Use Case 3. Transport service control on a ODUk/Och multi-
      domain transport network with Ethernet access links...........70
      2.4. Use Case 4. Transport service control on a ODUk/Och multi-
      domain transport network with multi-function access links.....77
      2.5. Use Case 5. Real time updates of IP/MPLS layer TE link
      attributes that depend on supporting transport connectivity (e.g.
      transport SRLGs, propagation delay, etc.).....................80
      2.6. Use Case 6. Virtual Network Service......................81
   3. Security Considerations.......................................84
   4. IANA Considerations...........................................85
   5. References....................................................85
      5.1. Normative References.....................................85
      5.2. Informative References...................................85
   6. Acknowledgments...............................................85
   Appendix A. Data Examples........................................86
      A.1. Use Case 1...............................................86
         A.1.1. Domain 1............................................86
         A.1.2. Domain 2............................................93
         A.1.3. Domain 3............................................99
   Authors' Addresses..............................................105

1. Modeling Considerations

1.1. TE Topology Model

   The TE Topology Model is written in YANG modeling language. It is
   defined and developed by the IETF TEAS WG and is documented as "YANG
   Data Model for TE Topologies" [I-D.ietf-teas-yang-te-topo]. The model
   describes a TE network provider's Traffic Engineering data store as
   it is seen by a client. It allows for the provider to convey to each
   of its clients:

   o  information on network resources available to the client in the
      form of one or several native TE topologies (for example, one for
      each layer network supported by the provider);

   o  one or several abstract TE topologies, customized on per-client
      basis and sorted according to the provider's preference as to how
      the abstract TE topologies are to be used by the client;

   o  updates with incremental changes happened to the previously
      provided abstract/native TE topology elements;



Bryskin, et al.         Expires April 23, 2018                 [Page 3]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  updates on telemetry/state information the client has expressed
      interest in;

   o  overlay/underlay relationships between the TE topologies provided
      to the client (e.g. TE path computed in an underlay TE topology
      supporting a TE link in an overlay TE topology);

   o  client/server inter-layer adaptation relationships between the TE
      topologies provided to the client in the form of TE inter-layer
      locks or transitional links;

   The TE Topology Model allows a network client to:

   o  (Re-)configure/negotiate abstract TE topologies provided to the
      client by a TE network provider, so that said abstract TE
      topologies optimally satisfy the client's needs, constraints and
      optimization criteria, based on the client's network planning,
      service forecasts, telemetry information extracted from the
      network, previous history of service provisioning and performance
      monitoring, etc.;

   o  Obtain abstract/native TE topologies from multiple providers and
      lock them horizontally (inter-domain) and vertically (inter-layer)
      into the client's own native TE topologies;

   o  Configure, with each provider the trigger, frequency and contents
      of the TE topology update notifications;

   o  Configure, with each provider the trigger, frequency and contents
      of the TE topology telemetry (e.g. statistics counters) update
      notifications.


















Bryskin, et al.         Expires April 23, 2018                 [Page 4]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


1.2. TE Topology Modeling Constructs



















                           Figure 1. TE Topology


   o  TE domain - a multi-layer traffic engineered network under direct
      and complete control of a single authority, network provider. TE
      domain can be described by one or more TE topologies. For example,
      separate TE topologies can describe each of the domain's layer
      networks. TE domain can hierarchically encompass/parent other
      (child) TE domains, and can be encompassed by its own parent.

   o  TE topology - a graphical representation of a TE domain. TE
      topology is comprised of TE nodes (TE graph vertices)
      interconnected via TE links (TE graph edges).

   _____________________________________________________________________

      /* TE topology */
      augment /nw:networks/nw:network:
         /* TE topology global ID */
         +--rw provider-id?      te-types:te-global-id
         +--rw client-id?        te-types:te-global-id
         +--rw te-topology-id?   te-types:te-topology-id
      ..................................................................
         /* TE topology general parameters */
           |  +--rw preference?               uint8
           |  +--rw optimization-criterion?   identityref
      ..................................................................


Bryskin, et al.         Expires April 23, 2018                 [Page 5]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


               /* TE topology list of TE nodes */
      augment /nw:networks/nw:network/nw:node:
         +--rw te-node-id?   te-types:te-node-id
      ..................................................................
               /* TE topology list of TE links */
      augment /nw:networks/nw:network/nt:link:
      ..................................................................
              /* TE topology list of TE link termination points */
      augment /nw:networks/nw:network/nw:node/nt:termination-point:
         +--rw te-tp-id?   te-types:te-tp-id
      ..................................................................
   _____________________________________________________________________




























                             Figure 2. TE Node







Bryskin, et al.         Expires April 23, 2018                 [Page 6]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TE node - an element of a TE topology (appears as a vertex on TE
      graph). A TE node represents one or several nodes (physical
      switches), or a fraction of a node. A TE node belongs to and is
      fully defined in exactly one TE topology. A TE node is assigned a
      TE topology scope-unique ID. TE node attributes include
      information related to the data plane aspects of the associated
      node(s) (e.g. TE node's connectivity matrix), as well as
      configuration data (such as TE node name). A given TE node can be
      reached on the TE graph, representing the TE topology, over one of
      TE links terminated by the TE node.


   _____________________________________________________________________

      /* TE node */
      augment /nw:networks/nw:network/nw:node:
         /* TE node ID */
         +--rw te-node-id?   te-types:te-node-id
      ..................................................................
         /* TE node general attributes */
            |  +--rw te-node-attributes */
      ..................................................................
         /* TE node connectivity matrices */
            |     +--rw connectivity-matrices
      ..................................................................
         /* TE node underlay TE topology */
                 |     +--rw underlay-topology {te-topology-hierarchy}?
                 |        +--rw network-ref?   leafref
      ..................................................................
         /* TE node information sources*/
            |  +--ro information-source-entry* [information-source]
      ..................................................................
        /* TE node statistics */
           +--ro statistics
      ..................................................................
        /* TE node TTP list */
           +--rw tunnel-termination-point* [tunnel-tp-id]
      ..................................................................
   _____________________________________________________________________










Bryskin, et al.         Expires April 23, 2018                 [Page 7]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TE link - an element of a TE topology (appears as an edge on TE
      graph), TE link is unidirectional and its arrow indicates the TE
      link's direction. Edges with two arrows on the TE topology graph
      (see Figure 1) represent bi-directional combinations of two
      parallel oppositely directed TE links. A TE link represents one or
      several physical links or a fraction of a physical link.  A TE
      link belongs to and is fully defined in exactly one TE topology. A
      TE link is assigned a TE topology scope-unique ID. TE link
      attributes include parameters related to the data plane aspects of
      the associated link(s) (e.g. unreserved bandwidth, resource
      maps/pools, etc.), as well as the configuration data (such as
      remote node/link IDs, SRLGs, administrative colors, etc.) A TE
      link is connected to a TE node, terminating the TE link via
      exactly one TE link termination point (LTP).


   _____________________________________________________________________

      /* TE link */
      augment /nw:networks/nw:network/nt:link:
      /* TE link bundle information */
            |  +--rw (bundle-stack-level)?
            |  |  |  +--rw bundled-links
            |  |     +--rw component-links
      ..................................................................
      /* TE link general attributes */
          |  +--rw te-link-attributes

      ..................................................................
      /* TE link underlay TE topology */
            |     +--rw underlay! {te-topology-hierarchy}?
            |     |  +--rw primary-path
            |     |  +--rw backup-path* [index]

      ..................................................................
      /* TE link layer network */
           |     +--rw interface-switching-capability* [switching-
      capability encoding]

      ..................................................................
      /* TE link protection type */
           |     |  +--rw protection-type?   uint16

      ..................................................................

      /* TE link supporting TE tunnels */
          |     |  +--rw tunnels


Bryskin, et al.         Expires April 23, 2018                 [Page 8]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017



      ..................................................................
      /* TE link transitional link flag */
           |  +--ro is-transitional?            empty


      ..................................................................
      /* TE link information sources */
            |  +--ro information-source?         te-info-source

      ..................................................................
      /* TE link statistics */
           +--ro statistics

      ..................................................................
   _____________________________________________________________________



   o  Intra-domain TE link - TE link connecting two TE nodes within the
      same TE topology representing a TE network domain (e.g. L14 in
      Figure 1). From the point of view of the TE topology where the
      intra-domain TE link is defined, the TE link is close-ended, that
      is, both local and remote TE nodes of the link are defined in the
      same TE topology.

   o  Inter-domain TE link -  TE link connecting two border TE nodes
      that belong to separate TE topologies describing neighboring TE
      network domains (e.g. L3x in Figure 1). From the point of view of
      the TE topology where the inter-domain TE link is defined, the TE
      link is open-ended, that is, the remote TE node of the link is not
      defined in the TE topology where the local TE node and the TE link
      itself are defined.

      [Note: from the point of view of a TE node terminating an inter-
      domain TE link there is no difference between inter-domain and
      access TE links]

   o  Access TE link - TE link connecting a border TE node of a TE
      topology describing a TE network domain to a TE node of a TE
      topology describing a customer network site (e.g. L1x in Figure 1)
      From the point of view of the TE topology where the access TE link
      is defined, the TE link is open-ended, that is, the remote TE node
      of the link (t.e. TE node representing customer network
      element(s)) is not defined in the TE topology where the local TE
      node and the TE link itself are defined.



Bryskin, et al.         Expires April 23, 2018                 [Page 9]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


      [Note: from the point of view of a TE node terminating an access
      TE link there is no difference between access and inter-domain TE
      links]

   o  Dynamic TE link -  a TE link that shows up in (and disappears
      from) a TE topology as a result of multi-layer traffic
      engineering. Dynamic TE link (supported by a hierarchy TE tunnel
      dynamically set up in a server layer network) is automatically
      (i.e. without explicit configuration request) added to a client
      layer network TE topology to augment the topology with additional
      flexibility to ensure successful completion of the path
      computation for and provisioning of a client layer network
      connection/LSP. For example, an ODUk hierarchy TE tunnel can
      support a dynamic Ethernet layer TE link to enable provisioning of
      an Ethernet layer connection on a network that does not have
      sufficient static Ethernet layer connectivity. Likewise, dynamic
      TE link is automatically removed from the TE topology (and its
      supporting hierarchy TE tunnel released) as soon as the TE link
      stops carrying client layer connections/LSPs.

   o  TE link termination point (LTP) - a conceptual point of connection
      of a TE node to one of the TE links terminated by the TE node (see
      Figure 2a). Unlike TE link, LTP is bi-directional - an inbound TE
      link and an oppositely directed outbound TE link have to be
      connected to the TE node via the same LTP to constitute a bi-
      directional TE link combination.






     Figure 2a. Bi-directional TE link combination (left), independent
                     uni-directional TE links (right)


   _____________________________________________________________________

      /* LTP */
      augment /nw:networks/nw:network/nw:node/nt:termination-point:
      /* LTP ID */
         +--rw te-tp-id?   te-types:te-tp-id
      /* LTP network layer ID */
            |  +--rw interface-switching-capability* [switching-
      capability encoding]
            |  |  +--rw switching-capability    identityref


Bryskin, et al.         Expires April 23, 2018                [Page 10]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  +--rw encoding                identityref
      /* LTP bandwidth information */
            |  |  +--rw max-lsp-bandwidth* [priority]
            |  |     +--rw priority     uint8
            |  |     +--rw bandwidth?   te-bandwidth
      /* LTP inter-layer locks */
            |  +--rw inter-layer-lock-id?              uint32

      ..................................................................
   _____________________________________________________________________



   o  TE tunnel termination point (TTP) - an element of TE topology
      representing one or several potential TE tunnel
      termination/adaptation points (e.g. OCh layer transponder). A TTP
      is hosted by exactly one TE node (see Figure 2). A TTP is assigned
      a TE node scope-unique ID. Depending on the TE node's internal
      constraints, a given TTP hosted by the TE node could be accessed
      via one, several or all TE links originated/terminated from/by the
      TE node. TTP's important attributes include Local Link
      Connectivity List, Adaptation Client Layer List, TE inter-layer
      locks (see below), Unreserved Adaptation Bandwidth (announcing the
      TTP's remaining adaptation resources sharable between all
      potential client LTPs), and Property Flags (indicating
      miscellaneous properties of the TTP, such as capability to support
      1+1 protection for a TE tunnel terminated on the TTP).


   _____________________________________________________________________

      /* TTP */
           +--rw tunnel-termination-point* [tunnel-tp-id]
      /* TTP ID */
               +--rw tunnel-tp-id                           binary
      /* TTP layer network ID */
               |  +--rw switching-capability?        identityref
               |  +--rw encoding?                    identityref
      //* Inter-layer-locks supported by TTP */
               |  +--rw inter-layer-lock-id?         uint32
      /* TTP's protection capabilities */
               |  +--rw protection-type?             identityref
      /* TTP's list of client layer users */
               |  +--rw client-layer-adaptation

      ..................................................................
      /* TTP's Local Link Connectivity List (LLCL) */


Bryskin, et al.         Expires April 23, 2018                [Page 11]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


               |  +--rw local-link-connectivities

      ..................................................................
   _____________________________________________________________________



   o  Label - in the context of circuit switched layer networks
      identifies a particular resource on a TE link (e.g. Och
      wavelength, ODUk container)

      +--:(label)
         +--rw value?   rt-types:generalized-label























                Figure 3. TTP Local Link Connectivity List











Bryskin, et al.         Expires April 23, 2018                [Page 12]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TTP basic local link connectivity list (basic LLCL) - a list of TE
      link/label combinations terminated by the TTP-hosting TE node
      (effectively the same as LTP/label pairs), which the TTP could be
      connected to (see Figure 3, upper left). From the point of view of
      a potential TE path, basic LLCL provides a list of permissible
      LTP/label pairs the TE path needs to start/stop on for a
      connection, taking the TE path, to be successfully terminated on
      the TTP in question.

   o  TTP detailed local link connectivity list (detailed LLCL) - basic
      LLCL extended to provide a set of costs (such as intra-node
      summary TE metric, delay, SRLGs, etc.) associated with each LLCL
      entry (see Figure 3, upper right)


   _____________________________________________________________________

      /* TTP LLCL */
      |  +--rw local-link-connectivities
          |     +--rw number-of-entries?         uint16
          /* LLCL entry */

          /* LLCL entry LTP */
          |        +--rw link-tp-ref                leafref

      ..................................................................

      /* LLC entry label range */
      |     +--rw label-restriction* [inclusive-exclusive label-start]
      |     |  +--rw inclusive-exclusive    enumeration
      |     |  +--rw label-start            rt-types:generalized-label
            |     |  +--rw label-end?             rt-types:generalized-
      label
            |     |  +--rw range-bitmap?          binary

      /* LLCL entry underlay TE path(s) */
      |     +--rw underlay! {te-topology-hierarchy}?
      |     |  +--rw primary-path
      |     |  +--rw backup-path* [index]
      /* LLCL entry protection type */
      |     |  +--rw protection-type?   uint16
      /* LLCL entry supporting TE tunnels */
      |     |  +--rw tunnels
      /* LLCL entry bandwidth parameters */
      |     +--rw max-lsp-bandwidth* [priority]

      ..................................................................


Bryskin, et al.         Expires April 23, 2018                [Page 13]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


      /* LLCL entry metrics  (vector of costs) */
      |     +--rw te-default-metric?         uint32
      |     +--rw te-delay-metric?           uint32
      |     +--rw te-srlgs
      |     |  +--rw value*   te-types:srlg
      |     +--rw te-nsrlgs {nsrlg}?

      ..................................................................
      /* LLCL entry ID */
      |     |  +--rw id*   uint32
   _____________________________________________________________________



   o  TTP adaptation client layer list - a list of client layers that
      could be directly adopted by the TTP. This list is necessary to
      describe complex multi-layer (more than two layer) client-server
      layer hierarchies and, in particular, to identify the position of
      the TTP in said hierarchies.


   _____________________________________________________________________

      /* TTP adaptation client layer list */
               |  +--rw client-layer-adaptation
               |  |  +--rw switching-capability* [switching-capability
      encoding]
               /* Client layer ID */
               |  |     +--rw switching-capability    identityref
               |  |     +--rw encoding                identityref
               /* Adaptation bandwidth available for the client layer */
               |  |     +--rw bandwidth?              te-bandwidth
   _____________________________________________________________________
















Bryskin, et al.         Expires April 23, 2018                [Page 14]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017

























                   Figure 4. TE Node Connectivity Matrix


   o  TE node basic connectivity matrix - a TE node attribute describing
      the TE node's switching capabilities/limitations in the form of
      permissible switching combinations of the TE node's LTP/label
      pairs (see Figure 4, upper left). From the point of view of a
      potential TE path arriving at the TE node at a given inbound
      LTP/label, the node's basic connectivity matrix describes
      permissible outbound LTP/label pairs for the TE path to leave the
      TE node.

   o  TE node detailed connectivity matrix - TE node basic connectivity
      matrix extended to provide a set of costs (such as intra-node
      summary TE metric, delay, SRLGs, etc.) associated with each
      connectivity matrix entry (see Figure 4, upper right).


   _____________________________________________________________________

      /* TE node connectivity matrix */
               |  +--rw connectivity-matrix* [id]
               |     +--rw id                         uint32
               |     +--rw from  /* left LTP */


Bryskin, et al.         Expires April 23, 2018                [Page 15]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


               |     |  +--rw tp-ref?   leafref
               |     +--rw to    /* right LTP */
               |     |  +--rw tp-ref?   leafref
               |     +--rw is-allowed?                boolean

               /* Connectivity matrix entry label range */
               |     +--rw label-restriction* [inclusive-exclusive
      label-start]
               |     |  +--rw inclusive-exclusive    enumeration
               |     |  +--rw label-start            rt-
      types:generalized-label
               |     |  +--rw label-end?             rt-
      types:generalized-label
               |     |  +--rw range-bitmap?          binary

              /* Connectivity matrix entry underlay TE path(s) */
               |     +--rw underlay! {te-topology-hierarchy}?
               |     |  +--rw primary-path
               |     |  +--rw backup-path* [index]
               /* Connectivity matrix entry protection type */
               |     |  +--rw protection-type?   uint16
               /* Connectivity matrix entry supporting TE tunnels */
               |     |  +--rw tunnels
               /* Connectivity matrix entry bandwidth parameters */
               |     +--rw max-lsp-bandwidth* [priority]

      ..................................................................
               /* Connectivity matrix entry metrics (vector of costs) */
               |     +--rw te-default-metric?         uint32
               |     +--rw te-delay-metric?           uint32
               |     +--rw te-srlgs
               |     |  +--rw value*   te-types:srlg
               |     +--rw te-nsrlgs {nsrlg}?

      ..................................................................
               /* Connectivity matrix entry ID */
               |     |  +--rw id*   uint32
   _____________________________________________________________________











Bryskin, et al.         Expires April 23, 2018                [Page 16]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017




















                            Figure 5.  TE Path


   o  TE path - an ordered list of TE node/link IDs (each possibly
      augmented with labels) that interconnects over a TE topology a
      pair of TTPs and could be used by a connection (see Figure 5). A
      TE path could, for example, be a product of a successful path
      computation performed for a given TE tunnel


   _____________________________________________________________________

      /* TE path */

            /* TE topology the path is defined in */
       |     |  |  +--rw network-ref?    leafref
            /* Path type (IRO, XRO, ERO, RRO) */
       |     |  |  +--rw path-type?    identityref

            /* TE path elements */
       |     |  |  +--rw path-element* [path-element-id]
       |     |  |     +--rw path-element-id    uint32
       |     |  |     +--rw index?             uint32
       |     |  |     +--rw (type)?
             /* Numbered TE link path element */
       |     |  |        +--:(ip-address)
       |     |  |        |  +--rw ip-address-hop
       |     |  |        |     +--rw address?    inet:ip-address


Bryskin, et al.         Expires April 23, 2018                [Page 17]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


       |     |  |        |     +--rw hop-type?   te-hop-type
             /* AS number path element */
       |     |  |        +--:(as-number)
       |     |  |        |  +--rw as-number-hop
       |     |  |        |     +--rw as-number?   binary
       |     |  |        |     +--rw hop-type?    te-hop-type
             /* Unnumbered TE link path element */
       |     |  |        +--:(unnumbered-link)
       |     |  |        |  +--rw unnumbered-hop
       |     |  |        |     +--rw te-node-id?      inet:ip-address
       |     |  |        |     +--rw tp-id?   uint32
       |     |  |        |     +--rw hop-type?       te-hop-type
             /* Label path element */
       |     |  |        +--:(label)
       |     |  |        |  +--rw label-hop
       |     |  |        |     +--rw value?   rt-types:generalized-label
       |     |  |        |     +--rw direction?       boolean
       |     |  |        +--:(sid)
       |     |  |           +--rw sid-hop
       |     |  |              +--rw sid?   rt-types:generalized-label
   _____________________________________________________________________



   o  TE path segment - a contiguous fragment of a TE path

















                       Figure 6. TE Inter-Layer Lock






Bryskin, et al.         Expires April 23, 2018                [Page 18]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TE inter-layer lock - a modeling concept describing client-server
      layer adaptation relationships important for multi-layer traffic
      engineering. It is an association of M client layer LTPs and N
      server layer TTPs, within which data arriving at any of the client
      layer LTPs could be adopted onto any of the server layer TTPs. A
      TE inter-layer lock is identified by inter-layer lock ID, which is
      unique across all TE topologies provided by the same provider. The
      client layer LTPs and the server layer TTPs associated by a given
      TE inter-layer lock share the same inter-layer lock ID value.

      In Figure 6 a TE inter-layer lock IL_1 associates six client layer
      LTPs (C_LTP_1 - C_LTP_6) with two server layer TTPs (S_TTP_1 and
      S_TTP_2). As mentioned, they all have the same attribute -inter-
      layer lock ID:  IL_1, which is the only parameter/value indicating
      the association.  A given LTP may have zero, one or more inter-
      layer lock IDs.  In the case of multiple inter-layer lock IDs,
      this implies that the data arriving at the LTP can be adopted onto
      any of TTPs associated with all specified inter-layer locks.  For
      example, C_LTP_1 may be attributed with two inter-layer locks-
      IL_1 and IL_2. This would mean that C_LTP_1 for adaptation
      purposes can use not just TTPs associated with inter-layer lock
      IL_1 (i.e. S_TTP_1 and S_TTP_2 in the Figure), but any of TTPs
      associated with inter-layer lock IL_2. Likewise, a given TTP may
      have one or more inter-layer locks, meaning that it can offer the
      adaptation service to any client layer LTP having an inter-layer
      lock matching one of its own.

      LTPs and TTPs associated within the same TE inter-layer lock may
      be hosted by the same (hybrid, multi-layer) TE node or by multiple
      TE nodes defined in the same or separate TE topologies. The latter
      case is especially important because TE topologies of different
      layer networks could be modeled by separate augmentations of the
      basic (common to all layers) TE topology model.

              |  +--rw inter-layer-lock-id?         uint32

   o  Transitional link - an alternative method of modeling of client-
      server adaptation relationship. Transitional link is a bi-
      directional link connecting an LTP in a client layer to an LTP in
      a server layer, which is associated (via TTP's LLCL) with a server
      layer TTP capable of adopting of the client layer data onto a TE
      tunnel terminated by the TTP. Important attributes pf a
      transitional link are loca;/remote LTP IDs, TE metric and
      available adaptation bandwidth.





Bryskin, et al.         Expires April 23, 2018                [Page 19]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


























               Figure 7.  Native and Abstract TE Topologies


   o  Native TE topology - a TE topology as it is known (to full extent
      and unmodified) to the TE topology provider (see lower part of
      Figure 7.). A native TE topology might be discovered via various
      routing protocols and/or subscribe/publish techniques. For
      example, a first-level TE topology provider (such as a T-SDN
      Domain Controller, DC) may auto-discover its native TE
      topology(ies) by participating in the domain's OSPF-TE protocol
      instance; while a second-level TE topology provider (such as a
      Hierarchical T-SDN Controller. HC) normally builds its native TE
      topology(ies) based on TE topologies exposed by each of the
      subordinate, first- level TE topology providers.

   o  Underlay TE topology - a TE topology that serves as a base for
      constructing overlay TE topologies.







Bryskin, et al.         Expires April 23, 2018                [Page 20]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Overlay TE topology - a TE topology constructed based on one or
      more underlay TE topologies. Each TE node of the overlay TE
      topology represents a separate underlay TE topology (that could be
      mapped onto an arbitrary segment of a native TE topology). Each TE
      link of the overlay TE topology represents, generally speaking, an
      arbitrary TE path in one of the underlay TE topologies. The
      overlay TE topology and the supporting underlay TE topologies may
      represent separate layer networks (e.g. OTN/ODUk and WDM/OCh
      respectively) or the same layer network.

   o  Abstract TE topology - an overlay TE topology created by a
      provider to describe its network in some abstract way. An abstract
      TE topology contains at least one abstract TE topology element,
      such as TE node or TE link. An abstract TE topology is built based
      on contents of one or more of the provider's native TE topologies
      (serving as underlay(s)), the provider's policies and the client's
      preferences (see upper part of Figure 7).

   o  Customized TE topology - a TE topology tailored for a given
      provider's client. A customized TE topology is usually but not
      always an abstract TE topology. For example, a given abstract TE
      topology could be exposed to a group or all provider's clients (in
      which case the abstract TE topology is not a customized TE
      topology). Likewise, a given naive TE topology could be customized
      for a given client (for example, by removing high delay TE links
      the client does not care about). So customized TE topology is not
      an abstract TE topology, because it does not contain abstract TE
      topology elements

   o  TE inter-domain plug - a TE link attribute meaningful for open-
      ended inter-domain/access TE links. It contains a network-wide
      unique value (inter-domain plug ID) that identifies in the network
      a connectivity supporting the inter-domain/access TE link in
      question. It is expected that a given pair of neighboring domain
      TE topologies (provided by separate providers) will have each at
      least one open-ended inter-domain/access TE link with a TE inter-
      domain plug matching to one provided by its neighbor, thus
      allowing for a client of both domains to identify adjacent nodes
      in the separate neighboring TE topologies and resolve the open-
      ended inter-domain/access TE links by connecting them regardless
      of the links respective local/remote node ID/link ID attributes.
      Inter-domain plug IDs may be assigned and managed by a central
      network authority. Alternatively, inter-domain plug IDs could be
      dynamically auto-discovered (e.g. via LMP protocol).

   _____________________________________________________________________



Bryskin, et al.         Expires April 23, 2018                [Page 21]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017



           +--rw external-domain
              |  +--rw network-ref?            leafref
              |  +--rw remote-te-node-id?      te-types:te-node-id
              |  +--rw remote-te-link-tp-id?   te-types:te-tp-id
              |  +--rw plug-id?                uint32
   _____________________________________________________________________



1.3. Abstract TE Topology Calculation, Configuration and Maintenance

   The TE Topology Model does not prescribe what and how abstract TE
   topologies are computed, configured, manipulated and supported by a
   TE network (e.g. transport network) provider. However, it is assumed
   that:

   o  All TE topologies, native or abstract, conveyed to the same or
      different clients, are largely independent one from another. This
      implies that each TE topology, generally speaking, has an
      independent name space for TE node and link IDs, SRLGs, etc.
      (possibly overlapping with the name spaces of other TE
      topologies);

   o  All abstract TE topologies are bound to the respective underlay
      native or abstract TE topologies only by the overlay/underlay
      relationships defined by the TE Topology Model, but, otherwise,
      the abstract TE topologies are decoupled from their respective
      underlay TE topologies.

   It is envisioned that an original set of abstract TE topologies is
   produced by a TE network provider for each of its clients based on
   the provider's local configurations and/or policies, as well as the
   client-specific profiles. The original set of abstract TE topologies
   offered to a client may be accepted by the client as-is.
   Alternatively, the client may choose to negotiate/re-configure the
   abstract TE topologies, so that the latter optimally satisfy the
   client's needs. In particular, for each of the abstract TE topologies
   the client may request adding/removing TE nodes, TE links, TTPs
   and/or modifying re-configurable parameters of the existing
   components. The client may also request different optimization
   criteria as compared to those used for the original abstract TE
   topology optimization, or/and specify various topology-level
   constraints. The provider may accept or reject all or some abstract
   TE topology re-configuration requests. Hence, the abstract TE
   topology negotiation process may take multiple iterations before the
   provider and each of its clients agree upon a set of abstract TE


Bryskin, et al.         Expires April 23, 2018                [Page 22]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   topologies and their contents. Furthermore, the negotiation process
   could be repeated over time to produce new abstract TE topologies
   optimal to best suit evolving circumstances.

















   Figure 8. Native Transport Network Domain TE Topology as an Underlay
                        for Abstract TE Topologies


   Let's assume that a native transport network domain TE topology to be
   as depicted in Figure 8. The popular types of abstract TE topologies
   based on this native TE topology as an underlay are described in the
   following sections.





















Bryskin, et al.         Expires April 23, 2018                [Page 23]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


1.3.1. Single-Node Abstract TE Topology















     Figure 9.  Blocking/Asymmetrical TE Node with Basic Connectivity
                             Matrix Attribute


   In Figure 9, the transport network domain is presented to a client as
   a one-node abstract TE topology, where the single TE node (AN1)
   represents the entire domain and terminates all of the inter-
   domain/access TE links connecting the domain to its adjacent domains
   (i.e. TE links L1...L8). Because AN1 represents the entire domain the
   node's Underlay TE Topology attribute matches the ID of one of the
   domain's native TE topologies (e.g. one presented in Figure 8).
   [Note: all or some of the underlay TE topologies a given abstract TE
   topology depends on could be catered to the client by the provider
   along with the abstract TE topology in question or upon separate
   request(s) issued by the client.]

   One important caveat about abstract TE node AN1 is that it should be
   considered as an asymmetrical/blocking switch, because, generally
   speaking, it is not guaranteed that a suitable TE path exists between
   any given pair of inter-domain TE links into/out of the domain. This
   means from the TE Topology model point of view that there are certain
   limitations as to how AN1's LTPs could be interconnected
   inside/across the TE node. The model allows for asymmetrical/blocking
   switches by specifying for the associated TE nodes a non-empty basic
   connectivity matrix attribute describing permissible inbound-outbound
   TE link/label switching combinations. It is assumed that the
   provider's path computer can compute a set of optimal TE paths,
   connecting inbound TE link/label_x <=> outbound TE link/label_y
   combinations inside the abstract TE node over the TE node's underlay
   TE topology. Based on the results of such computations, AN1's



Bryskin, et al.         Expires April 23, 2018                [Page 24]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   connectivity matrix can be (re-)generated and (re-)conveyed to the
   abstract TE topology client.

   A richer version of the basic connectivity matrix is the detailed
   connectivity matrix. The latter not only describes permissible
   inbound TE link/label_x <=> TE link/label  TE link/label_y switching
   combinations, but also provides connectivity matrix entry specific
   vectors of various costs/metrics (in terms of delay, bandwidth,
   intra-node SRLGs and summary TE metrics) that a potential TE path
   will accrue, should a given connectivity matrix entry be selected by
   the path for crossing the TE node (see Figure 10).















   Figure 10.  Blocking/Asymmetrical TE Node with Detailed Connectivity
                             Matrix Attribute




















Bryskin, et al.         Expires April 23, 2018                [Page 25]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


1.3.2. Full Mesh Link Abstract TE Topology

















              Figure 11.  Full Mesh Link Abstract TE Topology


   In Figure 11, the transport network domain is abstracted in the
   following way.

   o  Each of the underlay native TE topology border TE nodes (i.e., the
      TE nodes terminating at least one inter-domain/access TE link,
      such as TE nodes S3 or S11 in Figure 8) is represented in the
      abstract TE topology as a separate abstract TE node, matching one-
      for-one to the respective border TE node of the underlay TE
      topology. For example, S3' of the abstract TE topology represents
      S3 of the underlay TE topology in Figure 8. [Note that such a
      relationship is modeled via Supporting Node attribute of TE node
      S3' specifying the ID of S3, as well as the ID of the TE topology
      where S3 is defined (i.e. TE topology in Figure 8)]. Likewise, S9'
      represents S9, S11' represents S11 and so forth;














Bryskin, et al.         Expires April 23, 2018                [Page 26]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TE nodes S3', S5', S8', S9' and S11' are interconnected via a full
      mesh of abstract TE links. It is assumed that the provider's path
      computer can compute a set of optimal TE paths over one or more of
      underlay TE topologies (such as presented in Figure 8)- one for
      each of said abstract TE links; and the provider can set up the TE
      tunnels in the network supporting each of the abstract TE links,
      either during the abstract TE topology configuration (in the case
      of committed/pre-established abstract TE links), or at the time
      the first client's connection is placed on the abstract TE link in
      question (the case of uncommitted abstract TE links). [Note that
      so (re-)computed TE paths, as well as the IDs of respective
      underlay TE topologies used for their computation are normally
      catered to the client in the Underlay TE path attribute of the
      associated abstract TE links]

   The configuration parameters of each of the abstract TE links (such
   as layer ID, bandwidth and protection requirements, preferred TE
   paths across the underlay TE topology for the primary and backup
   connections, etc.) are expected to be found in the abstract TE
   topology profiles/templates locally configured with the provider or
   pushed to the provider by the client via the policy NBI. Each of the
   abstract TE links may be later re-configured or removed by direct
   configuration requests issued by the client via TE Topology NBI.
   Likewise, additional abstract TE links may be requested by the client
   at any time.

   Some possible variants/flavors of the Full Mesh Link Abstract TE
   Topology described above are:

   o  Partial Mesh Link Abstract TE Topology (where some of the abstract
      TE links from the full mesh are missing);

   o  Double Mesh Link Abstract TE Topology (where each pair of abstract
      TE nodes is connected via two diverse abstract TE links).















Bryskin, et al.         Expires April 23, 2018                [Page 27]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


1.3.3. Star-n-Spokes Abstract TE Topology
















               Figure 12. Star-n-Spoke Abstract TE Topology


   The Full Mesh Link Abstract TE Topology suffers from the n-squared
   problem; that is, the number of required abstract TE links is
   proportional to square of the number of native TE topology border TE
   nodes. This problem can be mitigated (i.e., the number of required
   abstract TE links may be significantly reduced) by adding, to the
   abstract TE topology, an additional abstract TE node (the star)
   representing one or several interconnected non-border TE nodes from
   the native TE topology. Abstract TE links in the Star-n-Spokes
   Topology connect the star with all other TE nodes of the topology
   (the spokes). For example, abstract TE node AN1 in Figure 12 could
   represent collectively TE nodes S7, S10 and S4 of the native TE
   topology (see Figure 8) with abstract TE links connecting AN1 with
   all other TE nodes in the Star-n-Spokes Abstract TE Topology in
   Figure 12.

   In order to introduce a composite abstract TE node, (e.g. AN1 in
   Figure 12) representing in a given abstract TE topology an arbitrary
   segment of another TE topology (e.g. TE nodes S7, S12 and S4 of the
   TE topology in Figure 8) the TE topology provider is expected to
   perform the following operations:

   o  Copy the TE topology segment to be represented by the abstract TE
      node (i.e. TE nodes S7, S10 and S4 in Figure 8, as well as the TE
      links interconnecting them) into a separate  auxiliary TE topology
      (with a separate TE topology ID);



Bryskin, et al.         Expires April 23, 2018                [Page 28]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Set for each TE node and TE link of the auxiliary TE topology the
      Supporting Node/Link attribute matching the original TE topology
      ID, as well as the ID of the respective original TE node/link of
      the original TE topology.  For example, if S7" of the auxiliary TE
      topology is a copy of S7 of the original TE topology, the
      Supporting Node attribute of S7" will specify the ID of the
      original  TE topology (presented in figure 8) and the ID of S7;

   o  Set for the abstract TE node AN1 the Underlay TE Topology
      attribute matching the auxiliary TE Topology ID

   Furthermore, the Star-n-Spokes Abstract TE topology provider is
   expected to:

   o  Compute/provision TE paths/tunnels supporting each of the abstract
      TE links in Figure 12 (i.e. abstract TE links connecting the
      spokes to the star, AN1) as described in 1.3.2;

   o  Generate the AN1's Basic/Detailed Connectivity Matrix attribute
      based on intra-node path computations performed on the AN1's
      underlay (i.e. auxiliary) TE topology and describing permissible
      inbound TE link/label_x. outbound TE link/label_y switching
      combinations as described in 1.3.1

1.3.4. Arbitrary Abstract TE Topology

















                 Figure 13. Arbitrary Abstract TE Topology


   To achieve an optimal tradeoff between the number of components, the
   amount of information exposed by a transport network provider and the


Bryskin, et al.         Expires April 23, 2018                [Page 29]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   amount of path computations required to keep said information up-to-
   date, the provider may present the TE network domain as an arbitrary
   abstract TE topology comprised of any number of abstract TE nodes
   interconnected by abstract TE links (see Figure 13). Each of the
   abstract TE nodes can represent a single or several interconnected TE
   nodes from the domain's underlay (native or lower level abstract) TE
   topology, or a fraction of an underlay TE node. [Note that each of
   the abstract TE nodes of the TE topology in Figure 13 is expected to
   be introduced and maintained by the provider following the
   instructions as described in 1.3.3; likewise, each of the abstract TE
   links of the topology is expected to be computed, provisioned and
   maintained as described in 1.3.2]

1.3.5. Customized Abstract TE Topologies

























             Figure 14.  Customized Abstract TE Topology(ies)


   A transport network/domain provider may serve more than one client.
   In such a case, the provider "slices" the network/domain resources
   and exposes a slice for each of the clients in the form of a
   customized abstract TE topology. In Figure 14, the provider serves


Bryskin, et al.         Expires April 23, 2018                [Page 30]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   two clients (Blue and Red). Client Blue is provided with the Blue
   abstract TE topology supported by the blue TE tunnels or paths in the
   underlay (native) TE topology (depicted in the Figure with blue
   broken lines). Likewise, client Red is provided with the Red abstract
   TE topology supported by the red TE tunnels or paths in the underlay
   TE topology.

1.3.6. Hierarchical Abstract TE Topologies





















              Figure 15. Hierarchy of Abstract TE Topologies


   As previously mentioned, an underlay TE topology for a given abstract
   TE topology component does not have to be one of the domain's native
   TE topologies - another (lower level) domain's abstract TTE topology
   can be used instead. This means that abstract TE topologies are
   hierarchical in nature.

   Figure 15 provides an example of abstract TE topology hierarchy. In
   this Figure the blue topology is a top level abstract TE topology
   catered to by the provider to one of the domain's clients. One of the
   TE links of the blue topology - link EF - is supported by a TE path
   E'-M-P-Q-N-F' computed in the underlay TE topology (red topology),
   which happens to be domain's (lower level) abstract TE topology..
   Furthermore, as shown, the TE link PQ - one of the TE links
   comprising the E'-M-P-Q-N-F' path - is supported by its own underlay


Bryskin, et al.         Expires April 23, 2018                [Page 31]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   TE path, P'-X-Q' - computed on one of the domain's native TE
   topologies.

   Importantly, each TE link and TE node of a given abstract TE topology
   has, generally speaking, its individual stack/hierarchy of underlay
   TE topologies.

1.4. Merging TE Topologies Provided By Multiple Providers

   A client may receive TE topologies provided by multiple providers,
   each of which managing a separate domain of an interconnected multi-
   domain transport network. In order to make use of said topologies,
   the client is expected to merge (inter-connect) the provided TE
   topologies into one or more client's native TE topologies, each of
   which homogeneously representing the multi-domain transport network.
   This makes it possible for the client to select end-to-end TE paths
   for its TE tunnel connections traversing multiple domains.

   In particular, the process of merging TE topologies includes:

   o  Identifying neighboring TE domains and locking their TE topologies
      horizontally by connecting their inter-domain open-ended TE links;

   o  Renaming TE node, link, and SRLG IDs into ones allocated from a
      separate name space; this is necessary because all TE topologies
      are considered to be, generally speaking, independent with a
      possibility of clashes among TE node, link or SRLG IDs. Original
      TE node/link IDs along with the original TE topology ID are stored
      in the Source attribute of the respective TE nodes/links of the
      merged TE topology;

   o  Locking, TE topologies associated with different layer networks
      vertically according to provided TE inter-layer locks; this is to
      facilitate inter-layer path computations across multiple TE
      topologies provided by the same topology provider.














Bryskin, et al.         Expires April 23, 2018                [Page 32]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017



























                  Figure 16. Merging Domain TE Topologies


   Figure 16 illustrates the process of merging, by the client, of TE
   topologies provided by the client's providers.

   In the Figure, each of the two providers caters to the client a TE
   topology (abstract or native), describing the network domain under
   the respective provider's control. The client, by consulting the
   attributes of the open-ended inter-domain/access TE links - such as
   TE inter-domain plugs or remote TE node/link IDs - is able to
   determine that:

     1. the two domains are adjacent and are interconnected via three
        inter-domain TE links, and;

     2. each domain is connected to a separate customer site, connecting
        the left domain in the Figure to customer devices C-11 and C-12,
        and the right domain to customer devices C-21, C-22 and C-23.





Bryskin, et al.         Expires April 23, 2018                [Page 33]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   Therefore, the client interconnects the open-ended TE links, as shown
   on the upper part of the Figure.

   As mentioned, one way to interconnect the open-ended inter-
   domain/access TE links of neighboring domains is to mandate the
   providers to specify remote nodeID/linkID attributes in the provided
   inter-domain/access TE links. This, however, may prove to be not
   flexible. For example, the providers may not be aware of the
   respective remote nodeID/linked values. More importantly, this option
   does not allow for the client to mix-n-match multiple (more than one)
   TE topologies catered by the same providers (see the next section).
   Another, more flexible, option to resolve the open-ended inter-
   domain/access TE links is by decorating them with the TE inter-domain
   plug attribute. The attribute specifies inter-domain plug ID - a
   network-wide unique value that identifies on the network connectivity
   supporting a given inter-domain/access TE link. Instead of specifying
   remote node ID/link ID, an inter-domain/access TE link may provide a
   non-zero inert-domain plug ID. It is expected that two neighboring
   domain TE topologies (provided by separate providers) will have each
   at least one open-ended inter-domain/access TE link with a TE inter-
   domain plug matching to one provided by its neighbor. For example,
   the inter-domain TE link originating from node S5 of the Domain 1 TE
   topology (Figure 8) and the inter-domain TE link coming from node S3
   of Domain2 TE topology may specify matching TE inter-domain plugs
   (i.e. carrying the same inter-domain plug ID). This would allow for
   the client to identify adjacent nodes in the separate neighboring TE
   topologies and resolve the inter-domain/access TE links connecting
   them regardless of their respective nodeIDs/linkIDs (which, as
   mentioned, could be allocated from independent name spaces).

   Inter-domain plug IDs may be assigned and managed by a central
   network authority. Alternatively, inter-domain plug IDs could be
   dynamically auto-discovered (e.g. via LMP protocol).

   Furthermore, the client renames the TE nodes, links and SRLGs offered
   in the abstract TE topologies by assigning to them IDs allocated from
   a separate name space managed by the client. Such renaming is
   necessary, because the two abstract TE topologies may have their own
   name spaces, generally speaking, independent one from another; hence,
   ID overlaps/clashes are possible. For example, both TE topologies
   have TE nodes named S7, which, after renaming, appear in the merged
   TE topology as S17 and S27 respectively. IDs of the original (i.e.
   abstract TE topology) TE nodes/links along with the ID of the
   abstract TE topology they belong to are stored in the Source
   attribute of the respective TE nodes/links of the merged TE topology.
   For example, the Source attribute of S27 will contain S7 and the TE
   topology ID of the abstract TE topology describing domain 2.


Bryskin, et al.         Expires April 23, 2018                [Page 34]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017




   Once the merging process is complete, the client can use the merged
   TE topology for path computations across both domains, for example,
   to compute a TE path connecting C-11 to C-23.

1.4.1. Dealing With Multiple Abstract TE Topologies Provided By The Same
   Provider























    Figure 17. Multiple Abstract TE Topologies Provided By TE Topology
                                 Providers


   A given provider may expose more than one abstract TE topology to the
   client. For example, one abstract TE topology could be optimized
   based on a lowest-cost criterion, while another one could be based on
   best possible delay metrics, while yet another one could be based on
   maximum bandwidth availability for the client connections.
   Furthermore, the client may request all or some providers to expose
   additional abstract TE topologies, possibly of a different type
   and/or optimized differently, as compared to already-provided TE
   topologies. In any case, the client should be prepared for a provider
   to offer to the client more than one abstract TE topology.



Bryskin, et al.         Expires April 23, 2018                [Page 35]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   It should be up to the client to decide how to mix-and-match multiple
   abstract TE topologies provided by each of the providers, as well as
   how to merge them into the client's native TE topologies. The client
   also decides how many such merged TE topologies it needs to produce
   and maintain. For example, in addition to the merged TE topology
   depicted on the upper part of Figure 16, the client may merge the
   abstract TE topologies received from the two providers, as shown in
   Figure 17, into the client's additional native TE topologies, as
   shown in Figure 18.

   [Note: allowing for the client mix-n-matching of multiple TE
   topologies assumes that TE inter-domain plugs (rather than remote
   nodeID/linked) option is used for identifying neighboring domains and
   inter-domain/access TE link resolution.]






























        Figure 18. Multiple Native (Merged) Client's TE Topologies




Bryskin, et al.         Expires April 23, 2018                [Page 36]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   It is important to keep in mind that each of the three native
   (merged) TE topologies could be used by the client for computing TE
   paths for any of the multi-domain connections. The choice as to which
   topology to use for a given connection depends on the
   connection/tunnel parameters/requirements and the topology's style
   and optimization criteria.

1.5. Configuring Abstract TE Topologies

   When a client receives one or more abstract TE topologies from one of
   its providers, it may accept the topologies as-is and merge then into
   one or more of its own native TE topologies. Alternatively, the
   client may choose to request a re-configuration of one, some or all
   abstract TE topologies provided by the providers. Specifically, with
   respect to a given abstract TE topology, some of its TE nodes/links
   may be requested to be removed, while additional ones may be
   requested to be added. It is also possible that existing TE
   nodes/links may be asked to be re-configured. For example, a set of
   TE links may be requested to be disjoint from each other by
   configuring the same Non Sharing Risk Link Group (NSRLG) attribute
   for all links from the set. Such a configuration would force the
   provider to place TE tunnels supporting the TE links from the set
   onto sufficiently disjoint TE paths computed in the tunnels underlay
   TE topology. Furthermore, the topology-wide optimization criteria may
   be requested to be changed. For example, underlay TE paths supporting
   the abstract TE links, currently optimized to be shortest (least-
   cost) paths, may be requested to be re-optimized based on the minimal
   delay criteria. Additionally, the client may request the providers to
   configure entirely new abstract TE topologies and/or to remove
   existing ones. Furthermore, future periodic or one time additions,
   removals and/or re-configurations of abstract TE topology elements
   and/or their attributes could be (re-)scheduled by the client ahead
   of time.

   It is the responsibility of the client to implement the logic behind
   the above-described abstract TE topology negotiation. It is expected
   that the logic is influenced by the client's local
   configuration/templates, policies conveyed by client's clients, input
   from the network planning process, telemetry processor, analytics
   systems and/or direct human operator commands. Figure 19 exemplifies
   the abstract TE topology negotiation process. As shown in the Figure,
   the original abstract TE topology exposed by a provider was requested
   to be re-configured. Specifically, one of the abstract TE links was
   asked to be removed, while three new ones were asked to be added to
   the abstract TE topology.




Bryskin, et al.         Expires April 23, 2018                [Page 37]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017























       Figure 19.  Provider. Client Abstract TE Topology Negotiation


1.6. TE Tunnel Model

   The TE Tunnel Model is written in YANG modeling language. It is
   defined and developed by the IETF TEAS WG and is documented as "YANG
   Data Model for Traffic Engineering Tunnels and Interfaces" [I-D.ietf-
   teas-yang-te]. Among other things the model describes a TE network
   provider's TE Tunnel data store as it is seen and influenced by a
   client.

   The TE Tunnel Model allows for the provider to convey to each of its
   clients:

   o  information on TE tunnels provided to the client that are fully
      contained within the controlled network domain,

   o  information on multi-domain TE tunnel segments across the network
      domain controlled by the provider;

   o  information on connections/LSPs, supporting TE tunnels and TE
      tunnel segments;

   o  updates in response to changes to the client's active TE
      tunnels/segments and the connections supporting them,


Bryskin, et al.         Expires April 23, 2018                [Page 38]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  updates in response to the TE tunnel/segment telemetry/state
      information the client has expressed an interest in.

   The TE Tunnel Model allows for a TE network client to:

   o  Issue configuration requests to set up, tear down, replace, modify
      and manipulate end-to-end TE tunnels, as well as segments of
      multi-domain TE tunnels across the network controlled by the
      provider;

   o  Request and obtain information on active TE tunnels/segments and
      connections supporting them;

   o  Subscribe to and configure with the provider triggers, pace and
      contents of the TE tunnel/segment change update notifications;

   o  Subscribe to and configure with the provider triggers, pace and
      contents of the TE tunnel/segment event notifications, such as
      detected alarms, faults, protection/restoration actions, etc..

   o  Subscribe to and configure with the provider triggers, pace and
      contents of TE tunnel/segment telemetry (e.g. statistics counters)
      update notifications.


























Bryskin, et al.         Expires April 23, 2018                [Page 39]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


1.7. TE Tunnel/Transport Service Modeling Constructs




























                           Figure 20. TE tunnel


   o  TE tunnel - a connection-oriented service provided by a layer
      network of delivery of a client's data between source and
      destination tunnel termination points. A TE tunnel in a server
      layer network may support a link in a client layer network (e.g.
      OCh layer TE tunnel supporting ODU4 link). In Figure 20, a TE
      tunnel interconnects tunnel termination points resident on
      switches C-R2 and C-R3. A TE tunnel is realized via (supported by,
      mapped onto) one or more layer network connections/LSPs


   _____________________________________________________________________

      /* TE tunnel */
       |  +--rw tunnel* [name]
            |  |  +--rw name                   leafref


Bryskin, et al.         Expires April 23, 2018                [Page 40]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  +--rw identifier?            leafref
      /* TE tunnel configuration parameters */
            |  |  +--rw config
            |  |  |  +--rw name?                   string
            |  |  |  +--rw type?                   identityref
            |  |  |  +--rw identifier?             uint16
            |  |  |  +--rw description?            string
            |  |  |  +--rw switchcap?              identityref
            |  |  |  +--rw encoding?               identityref
            |  |  |  +--rw protection-type?        identityref
            |  |  |  +--rw admin-status?           identityref
            |  |  |  +--rw preference?             uint8
            |  |  |  +--rw reoptimize-timer?       uint16
            |  |  |  +--rw source?                 inet:ip-address
            |  |  |  +--rw destination?            inet:ip-address
            |  |  |  +--rw src-tp-id?              binary
            |  |  |  +--rw dst-tp-id?              binary
            |  |  |  +--rw topology-id?            te-types:te-topology-
      id
            |  |  |  +--rw ignore-overload?        boolean
            |  |  |  +--rw bandwidth-generic?      te-types:te-bandwidth
            |  |  |  +--rw disjointness?           te-types:te-path-
      disjointness
            |  |  |  +--rw setup-priority?         uint8
            |  |  |  +--rw hold-priority?          uint8
            |  |  |  +--rw signaling-type?         identityref
      /* Hierarchy TE tunnel parameters */
            |  |  |  +--rw hierarchical-link-id
            |  |  |  |  +--rw local-te-node-id?      te-types:te-node-id
            |  |  |  |  +--rw local-te-link-tp-id?   te-types:te-tp-id
            |  |  |  |  +--rw remote-te-node-id?     te-types:te-node-id
            |  |  |  |  +--rw te-topology-id?        te-types:te-
      topology-id
      /* Bidirectional TE tunnel parameters */
            |  |  |  +--rw bidirectional
            |  |  |     +--rw association
            |  |  |        +--rw id?              uint16
            |  |  |        +--rw source?          inet:ip-address
            |  |  |        +--rw global-source?   inet:ip-address
            |  |  |        +--rw type?            identityref
            |  |  |        +--rw provisioing?     identityref
      /* TE tunnel state */
            |  |  +--ro state
            |  |  |  +--ro name?                   string
            |  |  |  +--ro type?                   identityref
            |  |  |  +--ro identifier?             uint16
      ..............................................................


Bryskin, et al.         Expires April 23, 2018                [Page 41]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  |  +--ro oper-status?            identityref
      /* TE tunnel primary path and LSP container */
            |  |  +--rw p2p-primary-paths
            |  |  |  +--rw p2p-primary-path* [name]
            |  |  |     +--rw name
                     /* Configuration */
      leafref
            |  |  |     +--rw config
            |  |  |     |  +--rw name?                      string
            |  |  |     |  +--rw preference?                uint8
            |  |  |     |  +--rw path-setup-protocol?       identityref
            |  |  |     |  +--rw path-computation-method?   identityref
            |  |  |     |  +--rw path-computation-server?   inet:ip-
      address
            |  |  |     |  +--rw compute-only?              empty
            |  |  |     |  +--rw use-cspf?                  boolean
            |  |  |     |  +--rw verbatim?                  empty
            |  |  |     |  +--rw lockdown?                  empty
            |  |  |     |  +--rw named-explicit-path?       leafref
            |  |  |     |  +--rw named-path-constraint?     leafref {te-
      types:named-path-constraints}?
                      /* state */
            |  |  |     +--ro state
            |  |  |     |  +--ro name?                       string
            |  |  |     |  +--ro preference?                 uint8
            |  |  |     |  +--ro path-setup-protocol?        identityref
            |  |  |     |  +--ro path-computation-method?    identityref
            |  |  |     |  +--ro path-computation-server?    inet:ip-
      address
            |  |  |     |  +--ro compute-only?               empty
            |  |  |     |  +--ro use-cspf?                   boolean
            |  |  |     |  +--ro verbatim?                   empty
            |  |  |     |  +--ro lockdown?                   empty
            |  |  |     |  +--ro named-explicit-path?        leafref
            |  |  |     |  +--ro named-path-constraint?      leafref
      {te-types:named-path-constraints}?
                        /* Computed path */
                        /* Computed path properties/metrics /
            |  |  |     |  +--ro computed-path-properties
            |  |  |     |  |  +--ro path-metric* [metric-type]
            |  |  |     |  |  |  +--ro metric-type           identityref
            |  |  |     |  |  |  +--ro accumulative-value?   uint64
                        /* Computed path affinities */
            |  |  |     |  |  +--ro path-affinities
            |  |  |     |  |  |  +--ro constraints* [usage]
            |  |  |     |  |  |     |  +--ro usage?
      identityref


Bryskin, et al.         Expires April 23, 2018                [Page 42]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  |     |  |  |     |  +--ro (style)?
            |  |  |     |  |  |     |     +--:(value)
            |  |  |     |  |  |     |     |  +--ro value?            te-
      types:admin-groups
            |  |  |     |  |  |     |     +--:(named)
            |  |  |     |  |  |     |        +--ro affinity-names*
      [name]
            |  |  |     |  |  |     |           +--ro name    string
                        /* Computed path SRLGs */
            |  |  |     |  |  +--ro path-srlgs
            |  |  |     |  |  |  +--ro (style)?
            |  |  |     |  |  |     +--:(values)
            |  |  |     |  |  |     |  +--ro usage?         identityref
            |  |  |     |  |  |     |  +--ro values*        te-
      types:srlg
            |  |  |     |  |  |     +--:(named)
            |  |  |     |  |  |        +--ro constraints* [usage]
            |  |  |     |  |  |           +--ro usage
      identityref
            |  |  |     |  |  |           +--ro constraint
            |  |  |     |  |  |              +--ro srlg-names* [name]
            |  |  |     |  |  |                 +--ro name    string
                        /* Computed path sub-objects */
            |  |  |     |  |  +--ro path-computed-route-objects
      ..............................................................
                        /* LSP (provisioned path) */
            |  |  |     |     +--ro lsp* [source destination tunnel-id
      lsp-id extended-tunnel-id type]
                        /* LSP parameters */
            |  |  |     |        +--ro source                leafref
            |  |  |     |        +--ro destination           leafref
            |  |  |     |        +--ro tunnel-id             leafref
            |  |  |     |        +--ro lsp-id                leafref
            |  |  |     |        +--ro extended-tunnel-id    leafref
            |  |  |     |        +--ro type                  leafref
            |  |  |     |        +--ro signaling-type?       identityref
            |  |  |     +--rw candidate-p2p-secondary-paths
            |  |  |        +--rw candidate-p2p-secondary-path*
      [secondary-path]
            |  |  |           +--rw secondary-path    leafref
            |  |  |           +--rw config
            |  |  |           |  +--rw secondary-path?        leafref
            |  |  |           |  +--rw priority?              uint16
            |  |  |           |  +--rw path-setup-protocol?
      identityref
            |  |  |           +--ro state
            |  |  |              +--ro secondary-path?        leafref


Bryskin, et al.         Expires April 23, 2018                [Page 43]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  |              +--ro priority?              uint16
            |  |  |              +--ro path-setup-protocol?
      identityref
            |  |  |              +--ro active?                boolean

      /* TE tunnel secondary path and LSP container */

            |  |  +--rw p2p-secondary-paths
            |  |  |  +--rw p2p-secondary-path* [name]
      ......................................................
            |  |  |     +--rw name      leafref
            |  |  |     +--rw config (same as for primary path )
      .....................................................
            |  |  |     +--ro state  (same as for primary, except for
      disjointedness_state )
         |        |  +--ro disjointness_state?        te-types:te-path-
      disjointness.....................................................
            |  |  |        +--ro computed-path-properties (same as for
      primary path)
      ..........................................................
          |  |  |        |  +--ro path-affinities (same as for primary
      path)
      ..........................................................
            |  |  |        |  +--ro path-srlgs    (same as for primary
      path)
      ..........................................................
            |  |  |        |  +--ro path-computed-route-objects
      .........................................................
                           /* LSP (provisioned path) */
            |  |  |        +--ro lsp  (same as for the primary LSP)
      ........................................................
   _____________________________________________________________________

















Bryskin, et al.         Expires April 23, 2018                [Page 44]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Tunnel termination point (TTP) - a physical device inside a given
      node/switch realizing a TE tunnel termination function in a given
      layer network, as well as the TE tunnel's adaptation function
      provided for client layer network(s). One example of tunnel
      termination point is an OCh layer transponder. [Note: Tunnel
      termination points are not to be confused with TE tunnel
      termination points, which are TE representations of physical
      tunnel termination points. Similar to physical switches and links
      of the network, such as depicted in Figure 20, being  represented
      on a TE topology describing the network as TE nodes and TE links,
      (physical) tunnel termination points (TTPs) are represented as TE
      tunnel termination points (TE TTPs, see 1.2) hosted by the TE
      nodes. For example, a provisioned connection/LSP starts on a
      source TTP, goes through a chain of physical links and stops on a
      destination TTP. In contrast, TE path (e.g. result of a path
      computation) starts on a source TE TTP, goes through a chain of TE
      links and stops on a destination TE TTP.]


   _____________________________________________________________________

            |  |  |  +--rw source?                 inet:ip-address
            |  |  |  +--rw destination?            inet:ip-address
            |  |  |  +--rw src-tp-id?              binary
            |  |  |  +--rw dst-tp-id?              binary
   _____________________________________________________________________



   o  TE tunnel hand-off point - an access link or inter-domain link by
      which a multi-domain TE tunnel enters or exits a given network
      domain, in conjunction with a layer network resource (such as a
      wavelength channel or ODUk container) allocated on the
      access/inter-domain link for the TE tunnel.

   o  TE tunnel segment - a part of a multi-domain TE tunnel that spans
      a given network domain and is directly and fully controlled by the
      domain's controller, DC. TE tunnel segment is a fragment of a
      multi-domain TE tunnel between

     1. the source tunnel termination point and the TE tunnel hand-off
        point outbound from the TE tunnel's first domain (head TE tunnel
        segment);

     2. inbound and outbound TE tunnel hand-off points into/from a given
        domain (transit TE tunnel segment);



Bryskin, et al.         Expires April 23, 2018                [Page 45]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


     3. inbound TE tunnel hand-off point into the TE tunnel's last
        domain and the destination tunnel termination point (tail TE
        tunnel segment);

   o  Transport service -  the same as TE tunnel segment

   o  Hierarchy TE tunnel - a server layer TE tunnel that supports a
      dynamically created TE link in the client layer network topology
      (e.g. see 1.2)


   _____________________________________________________________________

      /* Hierarchy TE tunnel parameters */
            |  |  |  +--rw hierarchical-link-id
            |  |  |  |  +--rw local-te-node-id?      te-types:te-node-id
            |  |  |  |  +--rw local-te-link-tp-id?   te-types:te-tp-id
            |  |  |  |  +--rw remote-te-node-id?     te-types:te-node-id
            |  |  |  |  +--rw te-topology-id?        te-types:te-
      topology-id
   _____________________________________________________________________



   o  Hierarchy transport service -  the first or the last segment of a
      multi-domain hierarchy TE tunnel

   o  Dependency TE tunnel - a hierarchical TE tunnel provisioned or to
      be provisioned in an immediayely adjacent server layer a given
      client layer TE tunnel depends on (i.e. carried or to be carried
      within)

   o  Potential TE tunnel/segment - a TE tunnel/segment configured in
      COMPUTE_ONLY mode. For such a TE tunnel/segment TE paths to be
      taken by supporting connection(s) is/are computed and monitored,
      but the connection(s) are not provisioned


   _____________________________________________________________________

            |  |  |     |  +--rw path-computation-method?   identityref
            |  |  |     |  +--rw path-computation-server?   inet:ip-
      address
            |  |  |     |  +--rw compute-only?              empty
            |  |  |     |  +--rw use-cspf?                  Boolean
   _____________________________________________________________________



Bryskin, et al.         Expires April 23, 2018                [Page 46]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017































                  Figure 20a. TE Tunnel Connections/LSPs


   o  Layer network connection/connection/LSP - a layer network path
      supporting a TE tunnel by realizing its implied forwarding
      function. Said path is provisioned in a given layer network's data
      plane over a chain of links and cross-connected over switches
      terminating the links. It interconnects the supported TE tunnel's
      source and destination termination points (in the case of end-to-
      end connection) or TE tunnel's hand-off points (in the case of
      transport service connection) or the TE tunnel's two split-merge
      points (in the case of segment protection connection.

      Example: ODU2 connection supporting an ODU2 TE tunnel.

   _____________________________________________________________________



Bryskin, et al.         Expires April 23, 2018                [Page 47]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                        /* LSP (provisioned path) */
            |  |  |     |     +--ro lsp* [source destination tunnel-id
      lsp-id extended-tunnel-id type]
                        /* LSP parameters */
            |  |  |     |        +--ro source                leafref
            |  |  |     |        +--ro destination           leafref
            |  |  |     |        +--ro tunnel-id             leafref
            |  |  |     |        +--ro lsp-id                leafref
            |  |  |     |        +--ro extended-tunnel-id    leafref
            |  |  |     |        +--ro type                  leafref
            |  |  |     |        +--ro signaling-type?       identityref
      ..................................................................
            |  |  |              +--ro priority?              uint16
            |  |  |              +--ro path-setup-protocol?
      identityref
            |  |  |              +--ro active?                Boolean
   _____________________________________________________________________



   o  Working connection - the primary connection of the supported TE
      tunnel or transport service (see Figure 20a).

   o  End-to-end protection connection - a secondary end-to-end
      connection of the supported TE tunnel (e.g. end-to-end 1+1
      protection connection, see Figure 20a).

   o  Segment protection connection - a secondary connection of the
      supported transport service protecting the service over a given
      network domain (e.g. 1+1 segment protection connection, see Figure
      20a)

   o  Restored connection - a connection after successful network
      failure  restorationrestoration procedures

   o  Current connection - the same as restored connection

   o  Nominal connection - a connection as (re-)provisioned upon a
      client configuration request (i.e. a connection before any
      automatic network failure restoration re-configurations are
      carroed out, also a connection after restoration reversion
      procedures are successfully completed)

   o  Unprotected TE tunnel/transport service - TE tunnel/transport
      service supported by a single (working/primary) connection/LSP




Bryskin, et al.         Expires April 23, 2018                [Page 48]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Protected TE tunnel/transport service - TE tunnel/transport
      service supported by one working connection/LSP and at least one
      protection/secondary connection/LSP

   o  Restorable TE tunnel/transport service - TE tunnel/transport
      service with pre-configured automatic network failure restoration
      capabilities

   o  TE tunnel/transport service automatic protection switchover - a
      process of switching of carrying user payload from the
      tunnel's/service's affected by a network failure working
      connection onto one of the tunnel's/service's healthy protection
      connection

   o  TE tunnel/transport service automatic protection reversion - a
      process of switching of carrying user payload from the
      tunnel's/service's protection connection  back onto the
      tunnel's/service's working connection after the latter was
      repaired from network failure

   o  TE tunnel/transport service protection Hold-off time - a
      configured period of time to expire between the moment of
      detecting of the first network failure affecting the
      tunnel's/service's working connection and the begining of the
      tunnel's/service's automatic protection switchover procedures

   o  TE tunnel/transport service protection WTR time - a configured
      period of time to expire between the moment of repairing the last
      network failure affecting the tunnel's/service's working
      connection and the begining of the tunnel's/service's automatic
      protection reversion procedures

   o  TE tunnel/transport service automatic network failure restoration
      - a process of replacing of the tunnel's/service's connection(s)
      affected by one or more network failures away from the point(s) of
      failue

   o  TE tunnel/transport service restoration reversion- a process of
      replacing of the tunnel's/service's connection(s) back onto the
      nominal connection paths after all network failures affecting the
      tunnel's/service's nominal connection(s) are repaired

   o  TE tunnel/transport service restoration Hold-off time - a
      configured period of time to expire between the moment of
      detecting of the first network failure affecting the
      tunnel's/service's nominal or current connection and the beginning
      of the automatic connection restoration procedures


Bryskin, et al.         Expires April 23, 2018                [Page 49]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  TE tunnel/transport service restoration WTR time - a configured
      period of time to expire between the moment of repairing the last
      network failure affecting the tunnel's/service's nominal
      connection and the begining of the connection automatic
      restoration reversion procedures

   o  Configured restoration path - a TE path specified by the client to
      be used during the automatic network failure restoration operation
      on one of the TE tunnel's/transport service's nominal or current
      connections

   o  Pre-computed restoration path - a configured restoration path to
      be validated by a path computer during the TE tunnel/transport
      service setup or client triggered modification

   o  Pre-provisioned restoration path - a pre-computed restoration path
      to be pre-provisioned/pre-signaled in the network (with all
      associated network resources allocated but not necessarily bound
      into cross-connects) during the TE tunnel/transport service setup
      or client triggered modification

   o  Connection configured path - a TE path (see 1.2) over a TE
      topology describing a layer network/domain that specifies (loosely
      or strictly) the client's requirements with respect to an ordered
      list of network nodes, links and resources on the links a given
      connection should go through


   _____________________________________________________________________

      |  |        +--rw explicit-route-object* [index]
            |  |           +--rw index                   leafref
            |  |           +--rw explicit-route-usage?   identityref
      (INCLUDE/EXCLUDE)
            |  |           |  +--rw index?            uint32
            |  |           |  +--rw (type)?
            |  |           |     +--:(numbered)
            |  |           |     |  +--rw numbered-hop
            |  |           |     |     +--rw address?    te-types:te-tp-
      id
            |  |           |     |     +--rw hop-type?   te-hop-type
            |  |           |     +--:(as-number)
            |  |           |     |  +--rw as-number-hop
            |  |           |     |     +--rw as-number?   binary
            |  |           |     |     +--rw hop-type?    te-hop-type
            |  |           |     +--:(unnumbered)
            |  |           |     |  +--rw unnumbered-hop


Bryskin, et al.         Expires April 23, 2018                [Page 50]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |           |     |     +--rw node-id?      te-types:te-
      node-id
            |  |           |     |     +--rw link-tp-id?   te-types:te-
      tp-id
            |  |           |     |     +--rw hop-type?     te-hop-type
            |  |           |     +--:(label)
            |  |           |     |  +--rw label-hop
            |  |           |     |     +--rw value?   rt-
      types:generalized-label
            |  |           |     +--:(sid)
            |  |           |        +--rw sid-hop
            |  |           |           +--rw sid?   rt-
      types:generalized-label
   _____________________________________________________________________



   o  Connection exclusion path - a TE path over a TE topology
      describing a layer network/domain that specifies the client's
      requirements with respect to an unordered list of network nodes,
      links and resources on the links to be avoided  by a given
      connection


   _____________________________________________________________________

      |        |  +--rw route-object-exclude-always* [index]
            |        |  |  +--rw index     leafref
            |        |  |  |  +--rw index?            uint32
            |        |  |  |  +--rw (type)?
            |        |  |  |     +--:(numbered)
            |        |  |  |     |  +--rw numbered-hop
            |        |  |  |     |     +--rw address?    te-types:te-tp-
      id
            |        |  |  |     +--:(as-number)
            |        |  |  |     |  +--rw as-number-hop
            |        |  |  |     |     +--rw as-number?   binary
            |        |  |  |     +--:(unnumbered)
            |        |  |  |     |  +--rw unnumbered-hop
            |        |  |  |     |     +--rw node-id?      te-types:te-
      node-id
            |        |  |  |     |     +--rw link-tp-id?   te-types:te-
      tp-id
            |        |  |  |     +--:(label)
            |        |  |  |     |  +--rw label-hop
            |        |  |  |     |     +--rw value?   rt-
      types:generalized-label


Bryskin, et al.         Expires April 23, 2018                [Page 51]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |        |  |  |     +--:(sid)
            |        |  |  |        +--rw sid-hop
            |        |  |  |           +--rw sid?   rt-
      types:generalized-label
   _____________________________________________________________________



   o  Connection computed path - a TE path over a TE topology describing
      a layer network/domain as computed (subject to all configured
      constraints and optimization criteria) for a given connection to
      take. Computed connection path could be thought as the TE path
      intended to be taken by the connection


   _____________________________________________________________________

       /* Computed path */
                        /* Computed path properties/metrics /
            |  |  |     |  +--ro computed-path-properties
            |  |  |     |  |  +--ro path-metric* [metric-type]
            |  |  |     |  |  |  +--ro metric-type           identityref
            |  |  |     |  |  |  +--ro accumulative-value?   uint64
                        /* Computed path affinities */
            |  |  |     |  |  +--ro path-affinities
            |  |  |     |  |  |  +--ro constraints* [usage]
            |  |  |     |  |  |     |  +--ro usage?
      identityref
            |  |  |     |  |  |     |  +--ro (style)?
            |  |  |     |  |  |     |     +--:(value)
            |  |  |     |  |  |     |     |  +--ro value?            te-
      types:admin-groups
            |  |  |     |  |  |     |     +--:(named)
            |  |  |     |  |  |     |        +--ro affinity-names*
      [name]
            |  |  |     |  |  |     |           +--ro name    string
                        /* Computed path SRLGs */
            |  |  |     |  |  +--ro path-srlgs
            |  |  |     |  |  |  +--ro (style)?
            |  |  |     |  |  |     +--:(values)
            |  |  |     |  |  |     |  +--ro usage?         identityref
            |  |  |     |  |  |     |  +--ro values*        te-
      types:srlg
            |  |  |     |  |  |     +--:(named)
            |  |  |     |  |  |        +--ro constraints* [usage]
            |  |  |     |  |  |           +--ro usage
      identityref


Bryskin, et al.         Expires April 23, 2018                [Page 52]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


            |  |  |     |  |  |           +--ro constraint
            |  |  |     |  |  |              +--ro srlg-names* [name]
            |  |  |     |  |  |                 +--ro name    string
                        /* Computed path sub-objects */
            |  |  |     |  |  +--ro path-computed-route-objects
      ..............................................................
   _____________________________________________________________________



   o  Connection actual path - an active connection's path as
      provisioned in the layer network's data plane in the form of a TE
      path over a TE topology describing the layer network/domain

1.8. Transport Service Mapping











                   Figure 21. Transport Service Mapping


   Let's assume that a provider has exposed to a client its network
   domain in the form of an abstract TE topology, as shown on the left
   side of Figure 21. From then on, the provider should be prepared to
   receive from the client, a request to set up or manipulate a
   transport service with TE path(s) computed for the service
   connection(s) based on and expressed in terms of the provided
   abstract TE topology (as, for example, displayed in red broken line
   on the right side of Figure 21). When this happens, the provider is
   expected to set up the TE tunnels supporting all yet uncommitted
   abstract TE links (e. g, TE link S3'-S8' in the Figure).

   Furthermore, it is the responsibility of the provider to:

   o  Perform all the necessary abstract-to-native translations for the
      specified TE paths (i.e. the transport service connection
      configured paths);



Bryskin, et al.         Expires April 23, 2018                [Page 53]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Provision working and protection connections supporting the
      transport service; as well as replace/modify/delete them in
      accordance with subsequent client's configuration requests;

   o  Perform all the requested recovery operations upon detecting
      network failures affecting the transport service;

   o  Notify the client about all parameter changes, events and other
      telemetry information the client has expressed an interest in,
      with respect to the transport service in question.

1.9. Multi-Domain Transport Service Coordination

   A client of multiple TE network domains may need to
   orchestrate/coordinate its transport service setup/manipulation
   across some or all the domains. One example of such a client is a
   Hierarchical T-SDN Controller, HC, managing a connected multi-domain
   transport network where each of the domains is controlled by a
   separate Domain T-SDN Controller, DC. Said DCs are expected to expose
   TE Topology and TE Tunnel North Bound Interfaces, NBIs,, supported
   respectively by IETF TE Topology and TE Tunnel models (and their
   network layer specific augmentations). HC is assumed to establish
   client-provider relationship with each of the DCs and make use of
   said NBIs to extract from the domains various information (such as TE
   topologies and telemetry), as well as to convey instructions to
   coordinate across multiple domains its transport services set up and
   manipulation.






















Bryskin, et al.         Expires April 23, 2018                [Page 54]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017





























                  Figure 22. Two-Domain Transport Network


   Let's consider, for example, a two-domain transport network as
   represented in Figure 22. Suppose that HC is requested to set up an
   unprotected transport service to provide connectivity between
   customer network elements C-R1 and C-R6. It is assumed that by the
   time the request has arrived, the two DCs have already provided
   abstract TE topologies describing their respective domains, and that
   HC has merged the provided TE topologies into one that homogeneously
   describes the entire transport network (as shown in Figure 23).











Bryskin, et al.         Expires April 23, 2018                [Page 55]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017



























         Figure 23. Two-Domain Transport Network (Abstracted View)


   Consider that HC, using the merged TE topology, selected a TE path to
   be taken by the requested transport service connection as shown on
   the upper part of Figure 24.

   The multi-domain transport service set up coordination includes:

   o  Splitting selected for the transport service TE path(s) into
      segments - one set of segments per each domain involved in the
      service setup;

   o  Issuing a configuration request to each of the involved DCs to set
      up the transport service across the respective domain. Note that
      the connection configured paths are required to be expressed in
      terms of respective abstract TE topologies as exposed to HC by DCs
      (see lower part of Figure 24).






Bryskin, et al.         Expires April 23, 2018                [Page 56]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Waiting for the set up complete confirmation from each of the
      involved DCs. In case one of the DCs reports a failure, HC is
      responsible to carry out the cleanup/rollback procedures by
      requesting all involved DCs to tear down the successfully created
      segments


























   Figure 24. Transport Service Placement Based on Abstract TE Topology


   While processing the received from HC configuration request to set up
   the transport service, each DC is expected to carry out the transport
   service mapping procedures (as described in 1.8) resulting in the set
   up of all the necessary underlay TE tunnels, as well as one or more
   connections supporting the transport service. As a result, the
   requested transport service will be provisioned as shown in Figure
   25.

   The multi-domain transport service tear down coordination entails
   issuing to each of the involved DCs a configuration request to delete
   the transport service in the controlled by the DC domain. DCs are



Bryskin, et al.         Expires April 23, 2018                [Page 57]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   expected in this case to release all network resources allocated for
   the transport service.

   The multi-domain transport service modify coordination implies
   issuing to each of the involved DCs a configuration request to
   replace the transport service connections according to the newly
   provided paths and/or modify the connection parameters according to
   the newly provided configuration.




























         Figure 25. Multi-domain transport service is provisioned


2. Use Cases

2.1. Use Case 1. Transport service control on a single layer multi-
   domain transport network

   Configuration (Figure 26):




Bryskin, et al.         Expires April 23, 2018                [Page 58]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   o  Three-domain multi-vendor ODUk/Och transport network;

   o  The domains are interconnected via ODUk inter-domain links;

   o  Each of the domains is comprised of ODUk/Och network elements
      (switches) from a separate vendor and is controlled by a single
      (vendor specific) T-SDN Domain Controller (DC);

   o  All DCs expose IETF TE Topology and TE Tunnel model based NBIs;

   o  The transport network as a whole is controlled by a single
      hierarchical T-SDN controller (HC);

   o  HC  makes use of the NBIs to set up client-provider relationship
      with each of the DCs and controls via the DCs their respective
      network domains;

   o  Three customer IP/MPLS sites are connected to the transport
      network via ODUk access links;

   o  The customer IP/MPLS routers and the router transport ports
      connecting the routers to the transport network are managed
      autonomously and independently from the transport network.


























Bryskin, et al.         Expires April 23, 2018                [Page 59]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017




























    Figure 26 Three-domain ODUk/Och transport network with ODUk access
                          and inter-domain links


   Objective: Set up/manipulate/delete a shortest delay unprotected or
   protected transport service to provide connectivity between customer
   network elements C-R2 and C-R5

  1) TE Topology discovery

   All DCs provide to HC respective domain ODUk layer abstract TE
   topologies. Let's assume that each such topology is a single-node TE
   topology (as described in 1.3.1, abstract TE topology of this type
   represents the entire domain as a single asymmetrical/blocking TE
   node). Let's further assume that the abstract TE nodes representing
   the domains are attributed with detailed connectivity matrices
   optimized according to the shortest delay criterion. [Note: single-
   node abstract TE topologies are assumed for simplicity sake.
   Alternatively, any DC could have provided an abstract TE topology of
   any type described in 1.3].


Bryskin, et al.         Expires April 23, 2018                [Page 60]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   HC merges the provided TE topologies into its own native TE topology
   (the TE topology merging procedures are discussed in 1.4). The merged
   TE topology, as well as the TE topologies provided by DCs, are
   depicted in Figure 27. The merged TE topology homogeneously describes
   the entire transport network and hence is suitable for path
   computations across the network. Note that the dotted lines in the
   Figure connecting the topology access TE links with customer devices
   illustrate that HC in this use case has neither control nor
   information on the customer devices/ports and, therefore, can only
   provide a connectivity between the requested transport service
   ingress and egress access links (on assumption that the customer
   transport ports are provisioned independently)































    Figure 27. Three-domain single layer transport network abstract TE
                                 topology




Bryskin, et al.         Expires April 23, 2018                [Page 61]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


  2) Transport service path computation

   Using the merged TE topology (Figure 27, upper part) HC selects one
   or more optimal and sufficiently disjoint from each other TE path(s)
   for the requested transport service connection(s). Resulting TE paths
   for the requested end-to-end protected transport service, for
   example, could be as marked on the upper part of Figure 28.

   It is important to keep in mind that HC's path computer is capable of
   performing the necessary path selection only as long as the merged TE
   topology provides the necessary TE visibility for the path selection,
   both intra-domain (e.g. by virtue of provided by the abstract TE
   nodes detailed connectivity matrices) and inter-domain (because of
   provided inter-domain TE link attributes). In case one or more DCs
   is/are not capable of or willing to provide the detailed connectivity
   matrices (that is, DCs expose the respective domains as black boxes -
   unconstrained TE nodes terminating the inter-domain TE links), HC
   will not be able to select the end-to-end TE path(s) for the
   requested transport service on its own. In such a case HC may opt for
   making use of the Path Computation NBI, exposed by the DCs to
   explore/evaluate intra-domain TE path availability in real time. IETF
   TE Tunnel model supports the Path Computation NBI by allowing for the
   configuration of transport services in COMPUTE_ONLY mode. In this
   mode the provider is expected to compute TE paths for a requested
   transport service connections and return the paths in the request's
   response without triggering the connection provisioning in the
   network.

   Consider, for example, the case when none of the DCs has provided the
   detailed connectivity matrix attribute for the abstract TE nodes
   representing the respective domain. In such a case HC may:

     1. Request the ingress domain DC (i.e. DC1) to compute intra-domain
        TE paths connecting the ingress access TE link (i.e. the link
        facing C-R2) with each of the inter-domain TE links (i.e. links
        connecting Domain 1 to Domain 2 and Domain 3 respectively);

     2. Grow the TE paths returned by DC1 in (1) over the respective
        outbound inter-domain TE links;

     3. Request the neighboring DC(s) (e.g. DC3) to compute all intra-
        domain TE paths connecting across the domain all inbound into
        the domain inter-domain TE links reached by the path growing
        process in (2) with all other (outbound) domain's inter-domain
        TE links;




Bryskin, et al.         Expires April 23, 2018                [Page 62]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


     4. Augment the TE paths produced in step (2) with the TE paths
        determined in step (3);

     5. Repeat steps (2), (3) and (4) until the resulting TE paths reach
        the egress  domain (i.e. Domain 2);

     6. Request the egress domain DC (i.e. DC2) to grow each of the TE
        paths across the domain to connect them to the egress access TE
        link (i.e. the link facing C-R5);

     7. Select one (or more) most optimal and sufficiently disjoint from
        each other TE path(s) from the list produced in step (6).

   [Note: The transport service path selection method based on Path
   Computation NBIs exposed by DCs does not scale well and the more
   domains comprise the network and the more inter-domain links
   interconnect them, the worse the method works. Realistically, this
   approach will not work sufficiently well for the networks with more
   than 3 domains]






























Bryskin, et al.         Expires April 23, 2018                [Page 63]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017






























     Figure 28. TE paths computed for the protected transport service


  3) Transport service setup coordination

   HC carries out the multi-domain transport service setup coordination
   as described in 1.9. In particular, HC splits the computed TE path(s)
   into 3 sets of TE path segments - one set per domain (as shown on the
   lower part of Figure 28), and issues a TE tunnel configuration
   request to each of the DCs to set up the requested transport service
   across the domain under the DC's control.  The primary (and
   secondary) connection explicit path(s) is/are specified in the
   requests in terms of respective domain abstract TE topologies.

   While processing the configuration request, each DC performs the
   transport service mapping (as described in 1.8). In particular, the
   DC translates the specified explicit path(s) from abstract into
   native TE topology terms, sets up supporting underlay TE tunnels



Bryskin, et al.         Expires April 23, 2018                [Page 64]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   (e.g. Och TE tunnels), and, then, allocates required ODUk containers
   on the selected links and provisions the ODUk cross-connects on the
   switches terminating the links.

   If the setup is successfully completed in all three domains, the
   transport service connection(s) will be provisioned as depicted in
   Figure 29. If one of the DCs fails to set up its part, all
   successfully provisioned segments will be asked by HC to be released.

  4) Transport service teardown coordination

   HC issues to each of DCs a configuration request to release the
   transport service over the controlled domain, as well as the server
   layer TE tunnels supporting dynamically created links.



























                Figure 29. Transport service is provisioned






Bryskin, et al.         Expires April 23, 2018                [Page 65]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


2.2. Use Case 2. End-to-end TE tunnel control on a single layer multi-
   domain transport network

   Configuration (Figure 26): the same as in use case 1, except that HC
   in this use case controls customer devices/ports by extracting
   information from and pushing configuration to the customer site SDN
   controller(s)  managing the customer devices directly.

   Objective: Set up//delete an unprotected shortest delay TE tunnel
   interconnecting end-to-end C-R2 and C-R5

  1) TE Topology discovery

   As in use case 1 all DCs provide to HC domain ODUk layer abstract TE
   topologies. Additionally in this use the three customer site
   controllers expose the TE Topology and Tunnel model based NBIs to HC.
   Using the TE Topology NBI each customer controller provides to HC the
   respective customer site domain abstract TE topology. Customer site
   abstract TE topologies contain abstract TE nodes representing the
   devices which are directly connected to the transport network. Said
   abstract TE nodes host TE tunnel termination points, TTPs,
   representing the ports over which the customer devices are connected
   to the transport network, and terminate access TE links the TTPs are
   accessible from (see Figure 30).

























Bryskin, et al.         Expires April 23, 2018                [Page 66]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017






























   Figure 30. Abstract TE topologies provided by all network domains and
                              customer sites


















Bryskin, et al.         Expires April 23, 2018                [Page 67]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   HC merges the provided topologies into its own native TE Topology
   (the TE topology merging procedures are discussed in 1.4). The merged
   TE topology is depicted in Figure 31. It homogeneously describes end-
   to-end not only the entire transport network, but also the customer
   sites connected to the network and hence is suitable for TE tunnel
   end to end path computations.

























     Figure 31. Abstract TE topology describing transport network and
                      connected to it customer sites


  2) TE tunnel path computation

   Using the merged TE topology (Figure 31) HC selects an optimal TE
   path for the requested TE tunnel connecting end-to-end the specified
   TE tunnel termination points, TTPs. The resulting TE path, for
   example, could be as marked on the upper part of Figure 32.







Bryskin, et al.         Expires April 23, 2018                [Page 68]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


































               Figure 32. TE path computed for the TE tunnel


  3) TE tunnel setup coordination

   HC carries out the multi-domain TE tunnel setup coordination as
   described for use case 1, except that in this use case HC
   additionally initiates and controls the setup of the TE tunnel's head
   and tail segments on the respective customer sites. Note that the
   customer site controllers behave exactly as transport network domain
   DCs. In particular, they receive issued by HC configuration requests
   to set up the TE tunnel's head and tail segments respectively. While
   processing the requests the customer site controllers perform the
   necessary provisioning of the TE tunnel's source and destination
   termination points, as well as of the local sides of the selected


Bryskin, et al.         Expires April 23, 2018                [Page 69]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   access links. If all segments are successfully provisioned on
   customer sites and network domains, the TE tunnel connection will be
   provisioned as marked in Figure 33.

  4) TE tunnel teardown coordination

   HC issues to each of DCs and customer site controllers a
   configuration request to release respective segments of the TE
   tunnel, as well as the server layer TE tunnels supporting dynamically
   created links.



























                    Figure 33. TE tunnel is provisioned


2.3. Use Case 3. Transport service control on a ODUk/Och multi-domain
   transport network with Ethernet access links

   Configuration (Figure 34): the same as in use case 1, except that all
   access links in this use case are Ethernet layer links (depicted as



Bryskin, et al.         Expires April 23, 2018                [Page 70]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   blue lines in the Figure), while all inter-domain links remain to be
   ODUk layer links.



























     Figure 34. Three-domain ODUk/Och transport network with Ethernet
                            layer access links


   Objective: Set up//delete an unprotected shortest delay transport
   service supporting connectivity between C-R2 and C-R5

  1) TE Topology discovery

   In order to make possible for the necessary in this use case multi-
   layer path computation, each DC exposes to HC two (ODUk layer and
   Ethernet layer) abstract TE topologies,  Additionally, the lower
   layer (ODUk) TE nodes announce hosted by them TE tunnel termination
   points, TTPs, capable of adopting the payload carried over the
   Ethernet layer access links, From the TE Topology model point of view
   this means that said TTPs are attributed with TE inter-layer locks



Bryskin, et al.         Expires April 23, 2018                [Page 71]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   matching ones attributed to Ethernet TE links (i.e. TE links provided
   within Ethernet layer abstract TE topologies).

   Ethernet and ODUk layer single node abstract TE topologies catered to
   HC by each of the DCs are presented in Figure 35.

   HC merges the provided TE topologies into its own native TE Topology
   (the merging procedures are described in 1.4). Importantly in this
   case HC locks the provided TE topologies not only horizontally, but
   vertically as well, thus producing a two-layer TE topology
   homogenously describing both layers of the entire transport network,
   as well as the client-server layer adaptation relationships between
   the two layers. This makes the merged TE topology suitable for multi-
   layer/inter-layer multi-domain transport service path computations.
   The merged TE topology is presented in Figure 36.


















   Figure 35. ODUk and Ethernet layer abstract TE topologies exposed by
                                    DCs













Bryskin, et al.         Expires April 23, 2018                [Page 72]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017






























      Figure 36. Two-layer three-domain transport network abstract TE
                                 topology


  2) Transport service path computation

   Using the merged TE topology (Figure 36) HC selects an optimal TE
   path for the requested transport service.

   Note that if HC's path computer considered only Ethernet layer TE
   nodes and links, the path computation would .fail. This is because
   the Ethernet layer TE nodes (i.e. D1-e, D2-e and D3-e in the Figure)
   are disconnected from each other. However, the inter-layer
   associations (in the form of the TE inter-layer locks) make possible
   for the path computer to select TE path(s) in the lower (ODUk) layer
   that can be used to set up hierarchy TE tunnel(s) supporting
   additional dynamic TE link(s) in the upper (Ethernet ) layer in order
   for the requested transport service path computation to succeed.


Bryskin, et al.         Expires April 23, 2018                [Page 73]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   Let's sssume that the resulting TE path is as marked in Figure 37.
   The red line in the Figure marks the TE path selected for the ODUk
   layer hierarchy TE tunnel supporting the required Ethernet layer
   dynamic TE link.






























     Figure 37. Multi-layer TE path computed for the transport service


  3) Transport service setup coordination











Bryskin, et al.         Expires April 23, 2018                [Page 74]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   HC sets up the requested Ethernet layer transport service in two
   stages. First, it coordinates the end-to-end setup of the ODUk layer
   hierarchy TE tunnel between the selected TTPs. If this operation
   succeeds, a new Ethernet layer dynamic TE link (blue line connecting
   TE nodes D1-e and D2-e in Figure 38) is automatically added to the
   merged abstract TE topology. Importantly, as a part of the hierarchy
   transport service setup both DC1 and DC 2 add a new open-ended
   Ethernet layer inter-domain dynamic TE link to their respective
   abstract TE topologies. Second, HC coordinates the setup of the
   requested (Ethernet layer) transport service. The required TE path
   for the second stage is marked as fat blue line in the Figure. Note
   that DC3 controlling domain 3 is only involved in the first stage,
   but is oblivious to the second stage.





























    Figure 38. A new Ethernet layer TE link supported by ODUk layer TE
     tunnel is added to the provided and merged abstract TE topologies




Bryskin, et al.         Expires April 23, 2018                [Page 75]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   IF all involved DCs confirm successful setup completion, the
   requested transport service, as well as the supporting server layer
   hierarchy TE tunnel, will be provisioned as depicted in Figure 39. If
   one of the DCs fails to set up its segment in either of the layers,
   all successfully provisioned segments will be requested by HC to be
   released.



























    Figure 39. Ethernet transport service and supporting ODUk TE tunnel
                              are provisioned


  4) Transport service teardown coordination

   First, HC issues to DC1 and DC2 a configuration request to release
   the Ethernet layer transport service in the respective domains. After
   that, all three DCs are requested to release the segments of the
   supporting ODUk layer hierarchy TE tunnel. While processing the
   request DC1 and DC2 also remove the dynamic Ethernet layer TE links
   supported by the respective hierarchy TE tunnel's segments, thus the



Bryskin, et al.         Expires April 23, 2018                [Page 76]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   network's abstract TE topologies are reverted back to the state as
   shown in Figures 35 and 36.

2.4. Use Case 4. Transport service control on a ODUk/Och multi-domain
   transport network with multi-function access links

   Configuration (Figure 40): the same as in use case 3, except that all
   access links in this use case are multi-function links (depicted in
   the Figure as blue compound lines). Let's assume that, depending on
   configuration, the multi-function access links in this use case can
   carry either Ethernet or SDH/STM16 layer payload.

   Objective: Set up//delete an unprotected shortest delay SDH/STM16
   layer transport service interconnecting C-R2 and C-R5



























      Figure 40. Three-domain ODUk/Och transport network with multi-
                           function access links





Bryskin, et al.         Expires April 23, 2018                [Page 77]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


  1) TE Topology discovery

   The TE Topology model considers multi-function links as parallel
   mutually exclusive TE links each belonging to a separate layer
   network. For this use case each DC exposes to HC three (ODUk-,
   Ethernet- and SDH/STM16-layer) abstract TE topologies (generally
   speaking, one abstract TE topology per each layer network supported
   by at least one access or inter-domain link).  Like in use case 3,
   the lower layer (ODUk) TE nodes announce hosted by them TE tunnel
   termination points, TTPs, capable in this case of adopting Ethernet,
   SDH/STM16 or both layer payloads, The TTPs are attributed with TE
   inter-layer locks matching ones specified for Ethernet and/or
   SDH/STM16 TE links.

   Ethernet, SDH/STM16 and ODUk layer single-node abstract TE topologies
   catered to HC by each of the DCs are presented in Figure 41.

   HC merges the provided topologies into its own native TE Topology
   (the merging procedures are described in 1.4). As in use case 3 HC
   locks the provided TE topologies not only horizontally (i.e. between
   domains), but vertically (between layers) as well, thus producing a
   three-layer TE topology homogenously describing the three layers of
   the entire transport network, as well as the client-server layer
   adaptation relationships between the layers. This makes the merged TE
   topology suitable for multi-layer/inter-layer multi-domain transport
   service path computations. The merged TE topology is presented in
   Figure 42.






















Bryskin, et al.         Expires April 23, 2018                [Page 78]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   Figure 41. ODUk, Ethernet and SDH/STM16 layer abstract TE topologies
                              exposed by DCs



























     Figure 42. Three-layer three-domain transport network abstract TE
                                 topology


  2) Transport service path computation

   Using the merged TE topology (Figure 42) HC's path computer selects a
   TE path for the requested transport service. For example, for the
   SDH/STM16 layer unprotected transport service the resulting TE path
   could be determined as marked in Figure 43.









Bryskin, et al.         Expires April 23, 2018                [Page 79]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017



























   Figure 43. Multi-layer TE path computed for SDH/STM16 layer transport
                                  service


  3) Transport service setup coordination

   Same as in use case 3.

  4) Transport service teardown coordination

   Same as in use case 3.

2.5. Use Case 5. Real time updates of IP/MPLS layer TE link attributes
   that depend on supporting transport connectivity (e.g. transport
   SRLGs, propagation delay, etc.)

   Configuration (Figure 26): the same as in use case 1,

   Objective: A transport service interconnecting transport ports of two
   IP routers across a transport network is likely to serve a link in
   IP/MPLS layer network, which is usually controlled by a client of the


Bryskin, et al.         Expires April 23, 2018                [Page 80]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   transport network, such as IP/MPLS Controller. Performance of TE
   applications (e.g. path computer) running on the IP/MPLS Controller
   depends on the accuracy of IP/MPLS layer TE link attributes. Some of
   these attributes can change over time and are known real-time only to
   a transport network controller, such as HC. Examples of said
   attributes are transport SRLGs, propagation delay metric, protection
   capacities and status, etc. The objective of this use case is to
   ensure up-to-date state of said attributes in the IP/MPLS
   Controller's internal TED via necessary updates provided in a timely
   manner by the controller (e.g. HC) managing transport connectivity
   supporting IP/MPLS layer links.

   Realization:

   o  HC exposes and supports IETF TE Topology and TE Tunnel model based
      NBIs (the same NBIs that are exposed by DCs serving HC);

   o  IP/MPLS Controller makes use of the exposed NBIs to set up the
      respective client-provider relationships with HC;

   o  IP/MPLS Controller uses the TE Tunnel NBI to configure with HC a
      transport service interconnecting transport ports of a pair of IP
      routers desired to be adjacent in the IP/MPLS layer network. The
      TE Tunnel model allows for specifying in the transport service
      configuration request the TE topology and link IDs of the IP/MPLS
      TE link the requested transport service will be serving;

   o  IP/MPLS Controller uses the TE Topology NBI to subscribe with HC
      on the IP/MPLS TE link notifications with respect to changes in
      the TE link's attributes, such as SRLGs, propagation delay,
      protection capabilities/status, etc.;

   o  HC uses the TE Topology NBI to convey the requested notifications
      when HC learns the attributes IP/MPLS has expressed interest in or
      detects any changes since previous notifications (for example, due
      to network failure restoration/reversion procedures happened to
      the transport connectivity that supports the failure affected
      IP/MPLS links)

2.6. Use Case 6. Virtual Network Service

   Configuration (Figure 26): the same as in use case 1,

   Objective: Set up two Virtual Networks for the client, with Virtual
   Network 1 interconnecting customer IP routers C-R1, C-R7 and C-R4
   over a single-node abstract TE topology, and Virtual Network 2



Bryskin, et al.         Expires April 23, 2018                [Page 81]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


   interconnecting customer IP routers C-R2, C-R3, C-R8, C-R5 and C-R6
   over a full mesh link abstract TE topology as depicted in Figure 44.

   [Note: A client of a transport network may want to limit the
   transport network connectivity of a particular type and quality
   within distinct subsets of its network elements interconnected across
   the transport network. Furthermore, a given transport network may
   serve more than one client. In this case some or all clients may want
   to ensure the availability of transport network resources in case
   dynamic (re-)connecting of their network elements across the
   transport network is envisioned. In all such cases a client may want
   to set up one or more Virtual Networks over provided transport
   network]

  1) Virtual Network setup

   From the client's point of view a Virtual Network setup includes the
   following procedures:

   o  Identifying the Virtual Network membership - a subset of the
      client's network elements/ports to be interconnected over the
      abstract TE topology configured for the Virtual Network. Note that
      from the transport network provider's point of view this
      effectively determines the list of abstract TE topology's open-
      ended access TE links;

   o  Deciding on the Virtual Network's abstract TE topology type (e.g.
      single-node vs. link mesh), optimization criterion (e.g. shortest
      delay vs. smallest cost), bandwidth, link disjointedness,
      adaptation capabilities and other requirements/constraints, as
      well as, whether the TE tunnels supporting the abstract TE
      topology need to be pre-established or established on demand (i.e.
      when respective abstract TE topology elements are selected for a
      client transport service);

   o  Using the IETF TE Topology model based NBI exposed by the
      transport network controller (i.e. HC), configure the Virtual
      Network's abstract TE topology. Let's assume that in this use case
      the abstract TE topology for Virtual Network 1 is configured as a
      single-node abstract TE topology (see section 1.3.1) with the
      abstract TE node's detailed connectivity matrix optimized
      according to the shortest delay criteria. Likewise, the abstract
      TE topology for Virtual Network 2 is configured as a full-mesh
      link abstract TE topology (see section 1.3.2) optimized according
      to the smallest cost criteria with each of the abstract TE links
      to be supported by pre-established end-to-end protected TE
      tunnels.


Bryskin, et al.         Expires April 23, 2018                [Page 82]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


      [Note: Virtual Network's abstract TE topology (re-
      )configuration/negotiation process is no different from one that
      happens, for example, between HC and its providers, DCs, and is
      described in section 1.5]













































Bryskin, et al.         Expires April 23, 2018                [Page 83]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


    Figure 44. Virtual Networks provided for a transport network client


  2) Using Virtual Network

   Recall that use case 1 was about setting up a transport service
   interconnecting customer network elements C-R2 and C-R5 across the
   transport network. With the Virtual Network 2 in place, the client
   could have used the Virtual Network's TE topology to select a TE path
   for the service. The TE Tunnel model based NBI allows for the client
   to specify the Virtual Network's TE topology ID, as well, as the
   selected TE path (for example, as marked in Figure 45) as a
   configured path attribute in the transport service configuration
   request to ensure that the intended transport network resources are
   used for the service.





















   Figure 45. Transport service TE path is selected on Virtual Network's
                                TE topology


3. Security Considerations

   This document does not define networking protocols and data, hence
   are not directly responsible for security risks.




Bryskin, et al.         Expires April 23, 2018                [Page 84]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


4. IANA Considerations

   This document has no actions for IANA.

5. References

5.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.


   [I-D.ietf-teas-yang-te-topo]
             Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
             O. Dios, "YANG Data Model for TE Topologies", draft-ietf-
             teas-yang-te-topo-08 (work in progress), March 2017.

   [I-D.ietf-teas-yang-te]

             Saad, T., Gandhi, R., Liu, X., Beeram, V., Shah, H., and I.
             Bryskin, "A YANG Data Model for Traffic Engineering Tunnels
             and Interfaces", draft-ietf-teas-yang-te-06 (work in
             progress), March 2017.

5.2. Informative References

   [RFC2702] Awduche, D., "Requirements for Traffic Engineering Over
             MPLS", RFC 2702, September 1999.

6. Acknowledgments

   TBD.

















Bryskin, et al.         Expires April 23, 2018                [Page 85]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


Appendix A.                 Data Examples

   This section contains examples of an instance data in the JSON
   encoding [RFC7951].

A.1. Use Case 1

   In the use case described in Section 2.1. , there are three provider
   network domains, each of them is represented as an abstract TE
   topology. The JSON encoded example data configurations for the three
   domains are:

A.1.1. Domain 1

   {
     "networks": {
       "network": [
         {
           "network-types": {
             "te-topology": {}
           },
           "network-id": "otn-domain1-abs",
           "provider-id": 201,
           "client-id": 300,
           "te-topology-id": "te-topology:otn-domain1-abs",
           "node": [
             {
               "node-id": "D1",
               "te-node-id": "2.0.1.1",
               "te": {
                 "te-node-attributes": {
                   "domain-id" : 1,
                   "is-abstract": [null],
                   "underlay-topology": "domain1-och",
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "path-constraints": {
                       "bandwidth-generic": {
                         "te-bandwidth": {
                           "otn": [
                             {
                               "rate-type": "odu1",
                               "counter": 2


Bryskin, et al.         Expires April 23, 2018                [Page 86]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                             }
                           ]
                         }
                       }
                     }
                     "connectivity-matrix": [
                       {
                         "id": 10302,
                         "from": "1-0-3",
                         "to": "1-2-0"
                       },
                       {
                         "id": 10203,
                         "from": "1-0-2",
                         "to": "1-3-0"
                       },
                       {
                         "id": 10311,
                         "from": "1-0-3",
                         "to": "1-11-0"
                       },
                       {
                         "id": 11103,
                         "from": "1-0-11",
                         "to": "1-3-0"
                       },
                       {
                         "id": 10903,
                         "from": "1-0-9",
                         "to": "1-3-0"
                       },
                       {
                         "id": 10309,
                         "from": "1-0-3",
                         "to": "1-9-0"
                       },
                       {
                         "id": 10910,
                         "from": "1-0-9",
                         "to": "1-10-0"
                       },


Bryskin, et al.         Expires April 23, 2018                [Page 87]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                       {
                         "id": 11009,
                         "from": "1-0-10",
                         "to": "1-9-0"
                       },
                       {
                         "id": 20910,
                         "from": "1-1-9",
                         "to": "1-10-0"
                       },
                       {
                         "id": 21009,
                         "from": "1-0-10",
                         "to": "1-9-1"
                       },
                       {
                         "id": 20911,
                         "from": "1-1-9",
                         "to": "1-11-0"
                       },
                       {
                         "id": 21109,
                         "from": "1-0-11",
                         "to": "1-9-1"
                       }
                     ]
                   }
                 }
               },
               "termination-point": [
                 {
                   "tp-id": "1-0-3",
                   "te-tp-id": 10003
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                         }
                     ]
                   }


Bryskin, et al.         Expires April 23, 2018                [Page 88]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                 },
                 {
                   "tp-id": "1-3-0",
                   "te-tp-id": 10300
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                           "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-9",
                   "te-tp-id": 10009
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-9-0",
                   "te-tp-id": 10900
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-1-9",
                   "te-tp-id": 10109
                   "te": {


Bryskin, et al.         Expires April 23, 2018                [Page 89]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-9-1",
                   "te-tp-id": 10901
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-2",
                   "te-tp-id": 10002
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-2-0",
                   "te-tp-id": 10200
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }


Bryskin, et al.         Expires April 23, 2018                [Page 90]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-10",
                   "te-tp-id": 10010
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-10-0",
                   "te-tp-id": 11000
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-11",
                   "te-tp-id": 10011
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-11-0",


Bryskin, et al.         Expires April 23, 2018                [Page 91]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                   "te-tp-id": 11100
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-1-11",
                   "te-tp-id": 10111
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-11-1",
                   "te-tp-id": 11101
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 }
               ]
             }
           ]
         }
       ]
     }
   }


Bryskin, et al.         Expires April 23, 2018                [Page 92]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


A.1.2. Domain 2

   {
     "networks": {
       "network": [
         {
           "network-types": {
             "te-topology": {}
           },
           "network-id": "otn-domain2-abs",
           "provider-id": 202,
           "client-id": 300,
           "te-topology-id": "te-topology:otn-domain2-abs",
           "node": [
             {
               "node-id": "D2",
               "te-node-id": "2.0.2.2",
               "te": {
                 "te-node-attributes": {
                   "is-abstract": [null],
                   "underlay-topology": "domain2-och",
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "path-constraints": {
                       "bandwidth-generic": {
                         "te-bandwidth": {
                           "otn": [
                             {
                               "rate-type": "odu1",
                               "counter": 2
                             }
                           ]
                         }
                       }
                     }
                     "connectivity-matrix": [
                       {
                         "id": 12125,
                         "from": "1-0-21",
                         "to": "1-25-0"
                       },



Bryskin, et al.         Expires April 23, 2018                [Page 93]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                       {
                         "id": 12521,
                         "from": "1-0-25",
                         "to": "1-21-0"
                         },
                       {
                         "id": 12128,
                         "from": "1-0-21",
                         "to": "1-28-0"
                       },
                       {
                         "id": 12821,
                         "from": "1-0-28",
                         "to": "1-21-0"
                       },
                       {
                         "id": 12231,
                         "from": "1-0-22",
                         "to": "1-31-0"
                         },
                       {
                         "id": 13122,
                         "from": "1-0-31",
                         "to": "1-22-0"
                       },
                       {
                         "id": 22228,
                         "from": "1-1-22",
                         "to": "1-28-0"
                       },
                       {
                         "id": 22822,
                         "from": "1-0-28",
                         "to": "1-22-1"
                       },
                       {
                         "id": 12528,
                         "from": "1-0-25",
                         "to": "1-28-0"
                       },
                       {


Bryskin, et al.         Expires April 23, 2018                [Page 94]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                         "id": 12825,
                         "from": "1-0-28",
                         "to": "1-25-0"
                       }
                     ]
                   }
                 }
               },
               "termination-point": [
                 {
                   "tp-id": "1-0-21",
                   "te-tp-id": 10021
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-21-0",
                   "te-tp-id": 12100
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-22",
                   "te-tp-id": 10022
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"


Bryskin, et al.         Expires April 23, 2018                [Page 95]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-22-0",
                   "te-tp-id": 12200
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-1-22",
                   "te-tp-id": 10122
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-22-1",
                   "te-tp-id": 12201
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {


Bryskin, et al.         Expires April 23, 2018                [Page 96]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                   "tp-id": "1-0-25",
                   "te-tp-id": 10025
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-25-0",
                   "te-tp-id": 12500
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-1-25",
                   "te-tp-id": 10125
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-25-1",
                   "te-tp-id": 12501
                   "te": {
                     "interface-switching-capability": [
                       {


Bryskin, et al.         Expires April 23, 2018                [Page 97]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-28",
                   "te-tp-id": 10028
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-28-0",
                   "te-tp-id": 12800
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-31",
                   "te-tp-id": 10031
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }


Bryskin, et al.         Expires April 23, 2018                [Page 98]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                 },
                 {
                   "tp-id": "1-31-0",
                   "te-tp-id": 13100
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 }
               ]
             }
           ]
         }
       ]
     }
   }

A.1.3. Domain 3

   {
     "networks": {
       "network": [
         {
           "network-types": {
             "te-topology": {}
           },
           "network-id": "otn-domain3-abs",
           "provider-id": 203,
           "client-id": 300,
           "te-topology-id": "te-topology:otn-domain3-abs",
           "node": [
             {
               "node-id": "D3",
               "te-node-id": "2.0.3.3",
               "te": {
                 "te-node-attributes": {
                   "is-abstract": [null],



Bryskin, et al.         Expires April 23, 2018                [Page 99]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                   "underlay-topology": "domain3-och",
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "path-constraints": {
                       "bandwidth-generic": {
                         "te-bandwidth": {
                           "otn": [
                             {
                               "rate-type": "odu1",
                               "counter": 2
                             }
                           ]
                         }
                       }
                     }
                     "connectivity-matrix": [
                       {
                         "id": 13638,
                         "from": "1-0-38",
                         "to": "1-38-0"
                       },
                       {
                         "id": 13836,
                         "from": "1-0-38",
                         "to": "1-36-0"
                       },
                       {
                         "id": 13639,
                         "from": "1-0-36",
                         "to": "1-39-0"
                       },
                       {
                         "id": 13936,
                         "from": "1-0-39",
                         "to": "1-36-0"
                       },
                       {
                         "id": 23636,
                         "from": "1-0-36",
                         "to": "1-36-1"
                       },


Bryskin, et al.         Expires April 23, 2018               [Page 100]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                       {
                         "id": 33636,
                         "from": "1-1-36",
                         "to": "1-36-0"
                       },
                       {
                         "id": 13739,
                         "from": "1-0-37",
                         "to": "1-39-0"
                       },
                       {
                         "id": 13937,
                         "from": "1-0-39",
                         "to": "1-37-0"
                       },
                       {
                         "id": 23737,
                         "from": "1-0-37",
                         "to": "1-37-1"
                       },
                       {
                         "id": 33737,
                         "from": "1-1-37",
                         "to": "1-37-0"
                       }
                     ]
                   }
                 }
               },
               "termination-point": [
                 {
                   "tp-id": "1-0-36",
                   "te-tp-id": 10036
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }


Bryskin, et al.         Expires April 23, 2018               [Page 101]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                 },
                 {
                   "tp-id": "1-36-0",
                   "te-tp-id": 13600
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-37",
                   "te-tp-id": 10037
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-37-0",
                   "te-tp-id": 13700
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-1-37",
                   "te-tp-id": 10137
                   "te": {


Bryskin, et al.         Expires April 23, 2018               [Page 102]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-37-1",
                   "te-tp-id": 13701
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-39",
                   "te-tp-id": 10039
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-39-0",
                   "te-tp-id": 13900
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }


Bryskin, et al.         Expires April 23, 2018               [Page 103]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-36",
                   "te-tp-id": 10036
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-36-0",
                   "te-tp-id": 13600
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-0-38",
                   "te-tp-id": 10038
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 },
                 {
                   "tp-id": "1-38-0",


Bryskin, et al.         Expires April 23, 2018               [Page 104]


Internet-Draft     TE Topology and Tunnel Modeling         October 2017


                   "te-tp-id": 13800
                   "te": {
                     "interface-switching-capability": [
                       {
                         "switching-capability": "switching-otn",
                         "encoding": "lsp-encoding-oduk"
                       }
                     ]
                   }
                 }
               ]
             }
           ]
         }
       ]
     }
   }

Authors' Addresses

   Igor Bryskin
   Huawei Technologies
   Email: Igor.Bryskin@huawei.com

   Vishnu Pavan Beeram
   Juniper Networks
   Email: vbeeram@juniper.net

   Tarek Saad
   Cisco Systems Inc
   Email: tsaad@cisco.com

   Xufeng Liu
   Jabil
   Email: Xufeng_Liu@jabil.com











Bryskin, et al.         Expires April 23, 2018               [Page 105]


Html markup produced by rfcmarkup 1.127, available from https://tools.ietf.org/tools/rfcmarkup/