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Versions: 00 01 draft-clemm-i2rs-yang-network-topo

Network Working Group                                           A. Clemm
Internet-Draft                                                     Cisco
Intended status: Standards Track                      H. Ananthakrishnan
Expires: April 24, 2014                                 Juniper Networks
                                                               J. Medved
                                                               T. Tkacik
                                                                   Cisco
                                                                R. Varga
                                               Pantheon Technologies SRO
                                                              N. Bahadur
                                                        Juniper Networks
                                                        October 21, 2013


                A YANG Data Model for Network Topologies
              draft-clemm-netmod-yang-network-topo-01.txt

Abstract

   This document defines a YANG data model for network topologies.

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
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   This Internet-Draft will expire on April 24, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions and Acronyms  . . . . . . . . . . . . . . . . . .   4
   3.  Network topology model overview . . . . . . . . . . . . . . .   4
     3.1.  Model structure . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Base model: Network Topology  . . . . . . . . . . . . . .   5
       3.2.1.  Main building blocks  . . . . . . . . . . . . . . . .   6
       3.2.2.  Discussion and selected design decisions  . . . . . .   7
       3.2.3.  Open issues and items for further discussion  . . . .   9
     3.3.  Extension of the model with specific topologies . . . . .   9
       3.3.1.  Layer 3 Unicast - IGP . . . . . . . . . . . . . . . .   9
       3.3.2.  OSPF Topology . . . . . . . . . . . . . . . . . . . .  11
       3.3.3.  IS-IS Topology  . . . . . . . . . . . . . . . . . . .  14
       3.3.4.  TED - Traffic Engineering Data  . . . . . . . . . . .  16
   4.  Network Topology YANG module  . . . . . . . . . . . . . . . .  16
   5.  Layer 3 Unicast IGP Topology YANG Module  . . . . . . . . . .  23
   6.  OSPF Topology YANG Module . . . . . . . . . . . . . . . . . .  28
   7.  ISIS Topology YANG Module . . . . . . . . . . . . . . . . . .  32
   8.  TED YANG Module . . . . . . . . . . . . . . . . . . . . . . .  35
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  41
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  42
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  42
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  42
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  42
     12.2.  Informative References . . . . . . . . . . . . . . . . .  42

1.  Introduction

   This document introduces a YANG [RFC6020] [RFC6021] data model for
   network topologies.  The model allows an application to have a



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   holistic view of an entire network, all contained in a single
   conceptual YANG datastore.

   In order to capture information that is specific to of a particular
   type of network topology, the basic model can be augmented and
   adapted.  As a result, the data model is generic in nature and can be
   applied to many network topologies.  For this reason, it is suitable
   for use as a general YANG data model framework to capture network
   topologies also beyond the types that are introduced here.  Specific
   topology types that are covered in this document include Layer 3
   Unicast IGP, IS-IS [RFC1195], and OSPF [RFC2178].  Adaptations and
   extensions to other types of topologies are possible, using similar
   model patterns to the ones that are illustrated.

   There are multiple applications for such a data model.  For example,
   a network controller can use the data model to represent the
   controller's view of a topology it controls and expose it to
   northbound applications via Netconf [RFC6241] or via a ReST Interface
   [I-D.bierman-netconf-restconf] [I-D.lhotka-netmod-yang-json].
   Alternatively, nodes within the network can use the data model to
   capture their understanding of the overall network topology that they
   are contained in, as well as propagate this understanding and compare
   it with that of other nodes.  The data model is generic in nature and
   can be applied to any type of network topology.

   The data model is defined in several YANG modules:

   o  Module "network-topology" contains a generic network topology
      model.  It defines a network topology at its most general level of
      abstraction.  It models aspects such as the nodes and edges that a
      topology graph is composed of, as well as termination points
      contained in the nodes that actually terminate the edges of the
      graph.  A network can contain multiple topologies, for example
      topologies at different layers and overlay topologies.  The model
      therefore allows also to capture the relationship between
      topologies, as well as the dependencies between nodes and
      termination points across topologies.

   o  Module "l3-unicast-igp-topology" applies the general network
      topology model to Layer 3 Unicast IGP topologies.  It augments the
      general topology with information specific to Layer 3 Unicast IGP.
      In doing so, it also illustrates the extension patterns associated
      with extending respectively augmenting the general topology model
      to meet the needs of a specific topology.







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   o  Module "ospf-topology" defines a topology model for OSPF, building
      on and extending the Layer 3 Unicast IGP topology model.  It
      serves as an example of how the general topology model can be
      refined across multiple levels.

   o  Module "isis-topology" defines a topology model for IS-IS, again
      building on and extending the Layer 3 Unicast IGP topology model.

   o  Module "ted", finally, is a helper module, defining information
      kept in the Traffic Engineering Database (TED) that is leveraged
      by IS-IS and OSPF topologies.

2.  Definitions and Acronyms

   Datastore: A conceptual store of instantiated management information,
   with individual data items represented by data nodes which are
   arranged in hierarchical manner.

   Data subtree: An instantiated data node and the data nodes that are
   hierarchically contained within it.

   HTTP: Hyper-Text Transfer Protocol

   IGP: Interior Gateway Protocol

   IS-IS: Intermediate System to Intermediate System protocol

   LSP: Label Switched Path

   NETCONF: Network Configuration Protocol

   OSPF: Open Shortest Path First, a link state routing protocol

   URI: Uniform Resource Identifier

   ReST: Representational State Transfer, a style of stateless interface
   and protocol that is generally carried over HTTP

   SRLG: Shared Risk Link Group

   TED: Traffic Engineering Database

   YANG: A data definition language for NETCONF

3.  Network topology model overview

   This section provides an overview of the network topology model.  We
   start with the structure of the foundational model that represents a



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   generic topology.  Subsequently, an overview of the specific
   topologies is given - Layer 3 Unicast IGP, OSPF, and IS-IS,
   respectively.  During the course of the discussion, sected design
   choices are explained and the pattern that should be applied to
   extend the model to new types of topologies is presented.

3.1.  Model structure

   The network topology model is defined by the following YANG modules,
   whose relationship is roughly depicted in the figure below.

                    +-----------------------+
                    |    network-topology   |
                    +-----------+-----------+
                                ^
                                |
                                |
                    +-----------^-------------+
                    | l3-unicast-igp-topology |
                    +----+---------------+----+
                         ^               ^
                         |               |
                         |               |
                +--------^-----+   +-----^---------+    +--------+
                | ospf-topology|   | isis-topology |    |  ted   |
                +--------^-----+   +-----^---------+    +----v---+
                         :               :                   :
                         :...............:...................:

                     Figure 1: Overall model structure

   YANG module network-topology defines the basic network topology
   model.  YANG module l3-unicast-igp-topology builds on top of this
   model, augmenting network-topology with additional definitions needed
   to represent Layer 3 Unicast IGP topologies.  This module in turn is
   augmented by YANG modules with additional definitions for OSPF and
   for IS-IS topologies, ospf-topology and isis-topology, respectively.
   Finally, YANG module "ted" contains a set of auxiliary definitions
   used by both ospf-topology and isis-topology, capturing data related
   to traffic engineering.

3.2.  Base model: Network Topology









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   The structure of the network topology data model, as later defined in
   the YANG module "network-topology", is depicted in the following
   diagram.  Brackets enclose list keys, "rw" means configuration data,
   "ro" means operational state data, and "?" designates optional nodes.
   The figure does not depict all definitions; it is intended to
   illustrate the overall structure.

              module: network-topology
                 +--rw network-topology
                    +--rw topology [topology-id]
                       +--rw topology-id          topology-id
                       +--ro server-provided?     boolean
                       +--rw topology-types
                       +--rw underlay-topology [topology-ref]
                       |  +--rw topology-ref    topology-ref
                       +--rw node [node-id]
                       |  +--rw node-id              node-id
                       |  +--rw supporting-node [node-ref]
                       |  |  +--rw node-ref    node-ref
                       |  +--rw termination-point [tp-id]
                       |     +--rw tp-id     tp-id
                       |     +--ro tp-ref*   tp-ref
                       +--rw link [link-id]
                          +--rw link-id            link-id
                          +--rw source
                          |  +--rw source-node    node-ref
                          |  +--rw source-tp?     tp-ref
                          +--rw destination
                          |  +--rw dest-node    node-ref
                          |  +--rw dest-tp?     tp-ref
                          +--rw supporting-link [link-ref]
                             +--rw link-ref    link-ref



3.2.1.  Main building blocks

   A network can contain multiple topologies.  Each topology is captured
   in its own list element, distinguished via a topology-id.  This is
   captured by list "topology", contained underneath the root container
   for this module, "network-topology".

   A topology has a certain type, such as OSPF or IS-IS.  A topology can
   even have multiple types simultaneously.  The type, or types, are
   captured underneath container "topology-types".  This serves as
   container for data nodes that represent specific topology types.  In
   this module, it serves merely as an augmentation target; topology-
   specific modules will later introduce new data nodes to represent new



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   topology types below this target, i.e. insert them below "topology-
   types" by ways of augmentation.

   Topology types SHOULD always be represented using containers, not
   leafs of empty type.  This allows to represent hierarchies of
   topology subtypes within the instance information.  For example, an
   instance of an OSPF topology (which, at the same time, is a layer 3
   unicast IGP topology) would contain underneath "topology-types"
   another container "l3-unicast-igp-topology", which in turn would
   contain a container "ospf-topology".

   A topology can in turn be part of a hierarchy of topologies, building
   on top of other topologies.  Any such topologies are captured in list
   "underlay-topology".

   Furthermore, a topology contains nodes and links, each captured in
   their own list.

   A node has a node-id.  This distinguishes the node from other nodes
   in the list.  In addition, a node has a list of termination points,
   used to terminate links.  An examples of a termination point might be
   a physical or logical port or, more generally, an interface.  Also, a
   node can in turn map onto other nodes in an underlay topology.  This
   is captured in list "supporting-node".

   A link is identified by a link-id, uniquely identifying the link
   within the topology.  Links are point-to-point and unidirectional.
   Accordingly, a link contains a source and a destination.  Both source
   and destination reference a corresponding node, as well as a
   termination point on that node.  Analogous to a node, a link can in
   turn map onto other links an underlay topology.  This is captured in
   list "supporting-link".

3.2.2.  Discussion and selected design decisions

   Rather than maintaining lists in separate containers, the model is
   kept relatively flat in terms of its containment structure.  This
   way, path specifiers used to refer to specific nodes, be it in
   management operations or in specifications of constraints, can remain
   relatively compact.  Of course, this means there is no separate
   structure in instance information that separates elements of
   different lists from one another.  Such structure is semantically not
   required, although it might enhance human readability in some cases.

   In an effort to minimize assumptions of what a topology might
   actually represent, mappings between topologies, nodes, links, and
   termination points are kept strictly generic.  For example, no
   assumptions are made whether a termination point actually refers to



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   an interface, or whether a node refers to a specific "system" or
   device; the model at this generic level makes no provisions for that.
   Any greater specifics about mappings between upper and lower layers
   can be captured in augmenting modules.  For example, if a termination
   point maps to an interface, an augmenting module can augment the
   termination point with a leaf that references the corresponding
   interface [I-D.ietf-netmod-interfaces-cfg].  If a node maps to a
   particular device or network element, an augmenting module can
   augment node with a leaf that references the network element.

   The model makes extensive use of groupings, instead of simply
   defining data nodes "in-line".  This allows to more easily include
   the corresponding data nodes in notifications, which then do not need
   to respecify each data node that is to be included.  The tradeoff for
   this is that it makes the specification of constraints more complex,
   because constraints involving data nodes outside the grouping need to
   be specified in conjunction with a "uses" statement where the
   grouping is applied.  This also means that constraints and XPath-
   statmeents need to specified in such a way that the navigate "down"
   first and select entire sets of nodes, as opposed to being able to
   simply specify them against individual data nodes.

   The topology model includes links that are point-to-point and
   unidirectional.  It does not directly support multipoint and
   bidirectional links.  While this may appear as a limitation, it does
   keep the model simple, generic, and allows it to very easily be
   subjected applications that make use of graph algorithms.
   Birectional conections can be represented through pairs of
   unidirectional links.  By introducing hierarchies of nodes, with
   nodes at one level mapping onto a set of other nodes at another
   level, and the introducing new links for nodes at that level,
   topologies with connections representing non-point-to-point
   communication patterns can be represented.

   Links are terminated by a single termination point, not sets of
   termination points.  Connections involving multihoming or link
   aggregation schemes need to be represented using multiple point-to-
   point links, then defining a link at a higher layer that is supported
   by those individual links.

   In a hierarchy of topologies, there are nodes mapping to nodes, links
   mapping to links, and termination points mapping to termination
   points.  Some of this information is redundant.  Specifically, with
   the link-to-links mapping known, and the termination points of each
   link known, maintaining separate termination point mapping
   information is not needed but can be derived via transitive closure.
   The model does provide for the option to include this information
   explicitly, but does not allow for it to be configured to avoid the



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   potential to introduce (and having to validate) corresponding
   integrity issues.

   A topology's topology types are represented using a container which
   contains a data node for each of its topology types.  A topology can
   encompass several types of topology simultaneously, hence a container
   is used instead of a case construct, with each topology type in turn
   represented by a dedicated presence container itself.  The reason for
   not simply using an empty leaf, or even simpler, do away even with
   the topology container and just use a leaf-list of topology-type
   instead, is to be able to represent "class hierarchies" of topology
   types, with one topology type refining the other.  Topology-type
   specific containers are to be defined in the topology-specific
   modules, augmenting the topology-types container.

3.2.3.  Open issues and items for further discussion

   YANG requires data needs to be designated as either configuration or
   operational data, but not both, yet it is important to have all
   topology information, including vertical cross-topology dependencies,
   captured in one coherent model.  In most cases topology information
   is discovered about a network; the topology is considered a property
   of the network that is reflected in the model.  That said, it is
   conceivable that certain types of topology need to also be
   configurable by an application.

   There are several alternatives in which this can be addressed.  The
   alternative chosen in this draft does not restrict topology
   information as read-only, but includes a flag that indicates for each
   topology whether it should be considered as read-only or configurable
   by applications.

   An alternative would be to designate topology list elements as read
   only.  The read-only topology list includes each topology; it is the
   complete reference.  In parallel a second topology list is
   introduced.  This list serves the purpose of being able to configure
   topologies which are then mirrored in the read-only list.  The
   configurable topology list adheres to the same structure and uses the
   same groupings as its read-only counterpart.  As most data is defined
   in those groupings, the amount of additional definitions required
   will be limited.  A configurable topology will thus be represented
   twice: once in the read-only list of all topologies, a second time in
   a configuration sandbox.

3.3.  Extension of the model with specific topologies

3.3.1.  Layer 3 Unicast - IGP




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   In order to represent a general Layer 3 Unicast IGP topology, the
   basic network topology model needs to be extended.  The corresponding
   extensions are introduced in a separate YANG module "l3-unicast-igp-
   topology".  The structure of those extensions is depicted in the
   following diagram.  Brackets enclose list keys, "rw" means
   configuration, "ro" operational state data, "?" designates optional
   nodes, "*" designates nodes that can have multiple instances.
   Parantheses enclose choice and case nodes.  Data nodes from the
   network-topology module are omitted (indicated by "....."), as long
   as not required to indicate containment structure.  Notifications are
   not depicted.

    module: network-topology
       +--rw network-topology
          +--rw topology [topology-id]
             +.....
             +--rw topology-types
             |  +--rw l3t:l3-unicast-igp-topology?
             .....
             +--rw node [node-id]
             |  .....
             |  +--rw termination-point [tp-id]
             |  |  .....
             |  |  +--rw l3t:igp-termination-point-attributes
             |  |     +--rw (termination-point-type)?
             |  |        +--:(ip)
             |  |        |  +--rw l3t:ip-address*      inet:ip-address
             |  |        +--:(unnumbered)
             |  |           +--rw l3t:unnumbered-id?   uint32
             |  +--rw l3t:igp-node-attributes
             |     +--rw l3t:name?        inet:domain-name
             |     +--rw l3t:flag*        flag-type
             |     +--rw l3t:router-id*   inet:ip-address
             |     +--rw l3t:prefix [prefix]
             |        +--rw l3t:prefix    inet:ip-prefix
             |        +--rw l3t:metric?   uint32
             |        +--rw l3t:flag*     flag-type
             +--rw link [link-id]
             |  .....
             |  +--rw l3t:igp-link-attributes
             |     +--rw l3t:name?     string
             |     +--rw l3t:flag*     flag-type
             |     +--rw l3t:metric?   uint32
             +--rw l3t:igp-topology-attributes
                +--rw l3t:name?   string
                +--rw l3t:flag*   flag-type





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   The module augments the original network-topology module as follows:

   o  A new topology type is introduced, l3-unicast-igp-topology-type.
      This is represented by a container object, which is inserted under
      the "topology-types" container of the network topology module.

   o  Additional topology attributes are introduced, defined in a
      grouping, which augments the "topology" list of the network
      topology module.  The attributes include an IGP name, as well as a
      set of flags (represented through a leaf-list).  Each type of flag
      is represented by a separate identity.  This allows to introduce
      additional flags in augmenting modules that are associated with
      specific IGP topologies, without needing to revise this module.

   o  Additional data objects for nodes are introduced by augmenting the
      "node" list of the network topology module.  New objects include
      again a set of flags, as well as a list of prefixes.  Each prefix
      in turn includes an ip prefix, a metric, and a prefix-specific set
      of flags.

   o  Links are augmented as well with a set of parameters, allowing to
      associate a link with an IGP name, another set of flags, and a
      link metric.

   In addition, the module defines a set of notifications to alert
   clients of any events concerning links, nodes, prefixes, and
   termination points.  Each notification includes an indication of the
   type of event, the topology from which it originated, and the
   affected node, or link, or prefix, or termination point.  In
   addition, as a convenience to applications, additional data of the
   affected node, or link, or termination point (respectively) is
   included.  While this makes notifications larger in volume than they
   would need to be, it avoids the need for subsequent retrieval of
   context information, which also might have changed in the meantime.

3.3.2.  OSPF Topology

   OSPF is the next type of topology represented in the model.  OSPF
   represents a particular type of Layer 3 Unicast IGP.  Accordingly,
   this time the Layer 3 Unicast IGP topology model needs to be
   extended.  The corresponding extensions are introduced in a separate
   YANG module "ospf-topology", whose structure is depicted in the
   following diagram.  For the most part, this module augments "l3
   -unicast-igp-topology".  Like before, brackets enclose list keys,
   "rw" means configuration, "ro" operational state data, "?" designates
   optional nodes, "*" designates nodes that can have multiple
   instances.  Parantheses enclose choice and case nodes.  Data nodes
   from the network-topology module are omitted (indicated by "....."),



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   as long as not required to indicate containment structure.
   Notifications are not depicted.

   module: network-topology
      +--rw network-topology
         +--rw topology [topology-id]
            .....
            +--rw topology-types
            |  +--rw l3t:l3-unicast-igp-topology?
            |     +--rw ospf:ospf?
            .....
            +--rw node [node-id]
            |  .....
            |  +--rw l3t:igp-node-attributes
            |     .....
            |     +--rw l3t:prefix [prefix]
            |     |  +.....
            |     |  +--rw ospf:ospf-prefix-attributes
            |     |     +--rw ospf:forwarding-address?   inet:ipv4-address
            |     +--rw ospf:ospf-node-attributes
            |     |  +--rw (router-type)?
            |     |  |  +--:(abr)
            |     |  |  |  +--rw ospf:abr?                 empty
            |     |  |  +--:(asbr)
            |     |  |  |  +--rw ospf:asbr?                empty
            |     |  |  +--:(internal)
            |     |  |  |  +--rw ospf:internal?            empty
            |     |  |  +--:(pseudonode)
            |     |  |     +--rw ospf:pseudonode?          empty
            |     |  +--rw ospf:dr-interface-id?     uint32
            |     |  +--rw ospf:multi-topology-id*   uint8
            |     |  +--rw ospf:capabilities?        bits
            |     |  +--rw ospf:ted
            |     |     +--rw ospf:te-router-id-ipv4?    inet:ipv4-address
            |     |     +--rw ospf:te-router-id-ipv6?    inet:ipv6-address
            |     |     +--rw ospf:ipv4-local-address [ipv4-prefix]
            |     |     |  +--rw ospf:ipv4-prefix    inet:ipv4-prefix
            |     |     +--rw ospf:ipv6-local-address [ipv6-prefix]
            |     |     |  +--rw ospf:ipv6-prefix      inet:ipv6-prefix
            |     |     |  +--rw ospf:prefix-option?   uint8
            |     |     +--rw ospf:pcc-capabilities?     pcc-capabilities
            |     .....
            +--rw link [link-id]
            |  .....
            |  +--rw l3t:igp-link-attributes
            |     .....
            |     +--rw ospf:ospf-link-attributes
            |     |  +--rw ospf:multi-topology-id?   uint8



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            |     |  +--rw ospf:ted
            |     |     +--rw ospf:color?                     uint32
            |     |     +--rw ospf:max-link-bandwidth?        decimal64
            |     |     +--rw ospf:max-resv-link-bandwidth?   decimal64
            |     |     +--rw ospf:unreserved-bandwidth [priority]
            |     |     |  +--rw ospf:priority     uint8
            |     |     |  +--rw ospf:bandwidth?   decimal64
            |     |     +--rw ospf:te-default-metric?         uint32
            |     |     +--rw ospf:srlg
            |     |        +--rw ospf:interface-switching-capabilities [switching-capability]
            |     |        |  +--rw ospf:switching-capability               ted:switching-capabilities
            |     |        |  +--rw ospf:encoding?                          uint8
            |     |        |  +--rw ospf:max-lsp-bandwidth [priority]
            |     |        |  |  +--rw ospf:priority     uint8
            |     |        |  |  +--rw ospf:bandwidth?   decimal64
            |     |        |  +--rw ospf:packet-switch-capable
            |     |        |  |  +--rw ospf:minimum-lsp-bandwidth?   decimal64
            |     |        |  |  +--rw ospf:interface-mtu?           uint16
            |     |        |  +--rw ospf:time-division-multiplex-capable
            |     |        |     +--rw ospf:minimum-lsp-bandwidth?   decimal64
            |     |        |     +--rw ospf:indication?              uint16
            |     |        +--rw ospf:srlg-values [srlg-value]
            |     |        |  +--rw ospf:srlg-value    uint32
            |     |        +--rw ospf:link-protection-type?               uint16
            |     .....
            +--rw l3t:igp-topology-attributes
               .....
               +--rw ospf:ospf-topology-attributes
               |  +--rw ospf:area-id?   area-id
               .....


   The module augments "l3-unicast-igp-topology" as follows:

   o  A new topology type for an OSPF topology is introduced.  This is
      represented by a container object, which is inserted under the "l3
      -unicast-igp-topology" container of the l3-unicast-igp-topology
      module.  This way, an ospf topology represents both a l3-unicast-
      igp topology and an ospf topology.

   o  Additional topology attributes are defined in a new grouping which
      augments igp-topology-attributes of the l3-unicast-igp-topology
      module.  The attributes include an OSPF area-id identifying the
      OSPF area.

   o  Additional data objects for nodes are introduced by augmenting the
      igp-node-attributes of the l3-unicast-igp-topology module.  New
      objects include router-type, de-interface-id for pseudonodes, list



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      of multi-topology-ids, ospf node capabilities and traffic
      engineering attributes.

   o  Links are augmented with a multi-topology-id and traffic
      engineering link attributes.

   o  Prefixes are augmented with OSPF specific forwarding address.

   In addition, the module extends IGP node, link and prefix
   notifications with OSPF attributes.

3.3.3.  IS-IS Topology

   IS-IS is another type of Layer 3 Unicast IGP.  Like OSPF topology,
   IS-IS topology is defined in a separate module, "isis-topology",
   which augments "l3-unicast-igp-topology".  The structure is depicted
   in the following diagram.  Like before, brackets enclose list keys,
   "rw" means configuration, "ro" operational state data, "?" designates
   optional nodes, "*" designates nodes that can have multiple
   instances.  Parantheses enclose choice and case nodes.  Data nodes
   from the network-topology module are omitted (indicated by "....."),
   as long as not required to indicate containment structure.
   Notifications are not depicted.

   module: network-topology
      +--rw network-topology
         +--rw topology [topology-id]
            .....
            |  +--rw l3t:l3-unicast-igp-topology?
            |     .....
            |     +--rw isis:isis?
            .....
            +--rw node [node-id]
            .....
            |  +--rw l3t:igp-node-attributes
            |     .....
            |     +--rw isis:isis-node-attributes
            |        +--rw isis:iso
            |        |  +--rw isis:iso-system-id?       iso-system-id
            |        |  +--rw isis:iso-pseudonode-id?   iso-pseudonode-id
            |        +--rw isis:net*                 iso-net-id
            |        +--rw isis:multi-topology-id*   uint8
            |        +--rw (router-type)?
            |        |  +--:(level-2)
            |        |  |  +--rw isis:level-2?             empty
            |        |  +--:(level-1)
            |        |  |  +--rw isis:level-1?             empty
            |        |  +--:(level-1-2)



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            |        |     +--rw isis:level-1-2?           empty
            |        +--rw isis:ted
            |           +--rw isis:te-router-id-ipv4?    inet:ipv4-address
            |           +--rw isis:te-router-id-ipv6?    inet:ipv6-address
            |           +--rw isis:ipv4-local-address [ipv4-prefix]
            |           |  +--rw isis:ipv4-prefix    inet:ipv4-prefix
            |           +--rw isis:ipv6-local-address [ipv6-prefix]
            |           |  +--rw isis:ipv6-prefix      inet:ipv6-prefix
            |           |  +--rw isis:prefix-option?   uint8
            |           +--rw isis:pcc-capabilities?     pcc-capabilities
            +--rw link [link-id]
            |  .....
            |  +--rw l3t:igp-link-attributes
            |     .....
            |     +--rw isis:isis-link-attributes
            |        +--rw isis:multi-topology-id?   uint8
            |        +--rw isis:ted
            |           +--rw isis:color?                     uint32
            |           +--rw isis:max-link-bandwidth?        decimal64
            |           +--rw isis:max-resv-link-bandwidth?   decimal64
            |           +--rw isis:unreserved-bandwidth [priority]
            |           |  +--rw isis:priority     uint8
            |           |  +--rw isis:bandwidth?   decimal64
            |           +--rw isis:te-default-metric?         uint32
            |           +--rw isis:srlg
            |              +--rw isis:interface-switching-capabilities [switching-capability]
            |              |  +--rw isis:switching-capability               ted:switching-capabilities
            |              |  +--rw isis:encoding?                          uint8
            |              |  +--rw isis:max-lsp-bandwidth [priority]
            |              |  |  +--rw isis:priority     uint8
            |              |  |  +--rw isis:bandwidth?   decimal64
            |              |  +--rw isis:packet-switch-capable
            |              |  |  +--rw isis:minimum-lsp-bandwidth?   decimal64
            |              |  |  +--rw isis:interface-mtu?           uint16
            |              |  +--rw isis:time-division-multiplex-capable
            |              |     +--rw isis:minimum-lsp-bandwidth?   decimal64
            |              |     +--rw isis:indication?              uint16
            |              +--rw isis:srlg-values [srlg-value]
            |              |  +--rw isis:srlg-value    uint32
            |              +--rw isis:link-protection-type?               uint16
            +--rw l3t:igp-topology-attributes
               ......
               +--rw isis:isis-topogloy-attributes
                  +--rw isis:net?   iso-net-id


   The module augments the l3-unicast-igp-topology as follows:




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   o  A new topology type is introduced, "isis-topology-type".  This is
      represented by a container object, which is inserted under the "l3
      -unicast-igp-topology" container of the l3-unicast-igp-topology
      module.  This way, an isis topology represents both a l3-unicast-
      igp-topology and an isis topology.

   o  Additional topology attributes are introduced in a new grouping
      which augments "igp-topology-attributes" of the l3-unicast-igp-
      topology module.  The attributes include an ISIS NET-id
      identifying the area.

   o  Additional data objects for nodes are introduced by augmenting
      "igp-node-attributes" of the l3-unicast-igp-topology module.  New
      objects include router-type, iso-system-id to identify the router,
      a list of multi-topology-id, a list of NET ids, and traffic
      engineering attributes.

   o  Links are augmented with multi-topology-id and traffic engineering
      link attributes.

   In addition, the module augments IGP nodes and links with ISIS
   attributes.

3.3.4.  TED - Traffic Engineering Data

   Traffic Engineering Data is required both by OSPF and IS-IS, which
   are defined in separate modules.  Information shared by both is
   defined in another module, "ted".  This module defines a set of
   groupings with auxiliary information required and shared by those
   other modules.  This module details traffic-engineering node and link
   attributes:

   o  TED node attributes include te-router-id for IPv4 and IPv6, local
      IPv4 and IPv6 addresses and path computation client capabilities.
      The path computation client capabilities in turn include a bit
      vector for various path computation capabilities.

   o  TED link attributes comprise link color, max-link-bandwidth, max-
      resv-link-bandwidth, unreserved bandwidth and re-metric.  They
      also include SRLG attributes which contains interface switching
      capabilities, a list of SRLG values, and a link protection type.
      The interface switching capabilities in turn contain a list
      element for each switching capability, defining encoding, max-lsp-
      bandwidth, and interface switching specific attributes.

4.  Network Topology YANG module

   <CODE BEGINS>



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   file "network-topology@2013-10-21.yang"
   module network-topology  {
       yang-version 1;
       namespace "urn:TBD:params:xml:ns:yang:network-topology";
       // replace with IANA namespace when assigned
       prefix "nt";

       import ietf-inet-types { prefix "inet"; }

       organization "TBD";

       contact "WILL-BE-DEFINED-LATER";

       description
           "This module defines a model for the topology of a network.
           Key design decisions are as follows:
           A topology consists of a set of nodes and links.
           Links are point-to-point and unidirectional.
           Bidirectional connections need to be represented through
           two separate links.
           Multipoint connections, broadcast domains etc can be represented
           through a hierarchy of nodes, then connecting nodes at
           upper layers of the hierarchy.";

       revision 2013-10-21 {
           description
               "Initial revision.";
       }

       typedef topology-id {
           type inet:uri;
           description
               "An identifier for a topology.";
       }

       typedef node-id {
           type inet:uri;
           description
               "An identifier for a node in a topology.
               The identifier may be opaque.
               The identifier SHOULD be chosen such that the same node in a
               real network topology will always be identified through the
               same identifier, even if the model is instantiated in separate
               datastores. An implementation MAY choose to capture semantics
               in the identifier, for example to indicate the type of node
               and/or the type of topology that the node is a part of.";
       }




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       typedef link-id {
           type inet:uri;
           description
               "An identifier for a link in a topology.
               The identifier may be opaque.
               The identifier SHOULD be chosen such that the same link in a
               real network topology will always be identified through the
               same identifier, even if the model is instantiated in separate
               datastores. An implementation MAY choose to capture semantics
               in the identifier, for example to indicate the type of link
               and/or the type of topology that the link is a part of.";
       }

       typedef tp-id {
           type inet:uri;
           description
               "An identifier for termination points on a node.
               The identifier may be opaque.
               The identifier SHOULD be chosen such that the same TP in a
               real network topology will always be identified through the
               same identifier, even if the model is instantiated in separate
               datastores. An implementation MAY choose to capture semantics
               in the identifier, for example to indicate the type of TP
               and/or the type of node and topology that the TP is a part of.";
       }

       typedef tp-ref {
           type leafref {
               path "/network-topology/topology/node/termination-point/tp-id";
           }
           description
               "A type for an absolute reference to a termination point.
               (This type should not be used for relative references.
               In such a case, a relative path should be used instead.)";
       }
       typedef topology-ref {
           type leafref {
               path "/network-topology/topology/topology-id";
           }
           description
               "A type for an absolute reference a topology instance.";
       }

       typedef node-ref {
           type leafref {
               path "/network-topology/topology/node/node-id";
           }
           description



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               "A type for an absolute reference to a node instance.
               (This type should not be used for relative references.
               In such a case, a relative path should be used instead.)";
       }

       typedef link-ref {
           type leafref {
               path "/network-topology/topology/link/link-id";
           }
           description
               "A type for an absolute reference a link instance.
               (This type should not be used for relative references.
               In such a case, a relative path should be used instead.)";
       }

       grouping tp-attributes {
           description
               "The data objects needed to define a termination point.
               (This only includes a single leaf at this point, used
               to identify the termination point.)
               Provided in a grouping so that in addition to the datastore,
               the data can also be included in notifications.";
           leaf tp-id {
               type tp-id;
           }
           leaf-list tp-ref {
               type tp-ref;
               config false;
               description
                   "The leaf list identifies any termination points that the
                   termination point is dependent on, or maps onto.
                   Those termination points will themselves be contained
                   in a supporting node.
                   This dependency information can be inferred from
                   the dependencies between links.  For this reason,
                   this item is not separately configurable.  Hence no
                   corresponding constraint needs to be articulated.
                   The corresponding information is simply provided by the
                   implementing system.";
           }
       }

       grouping node-attributes {
           description
               "The data objects needed to define a node.
               The objects are provided in a grouping so that in addition to
               the datastore, the data can also be included in notifications
               as needed.";



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           leaf node-id {
               type node-id;
               description
                   "The identifier of a node in the topology.
                   A node is specific to a topology to which it belongs.";
           }
           list supporting-node {
               description
                   "This list defines vertical layering information for nodes.
                   It allows to capture for any given node, which node (or nodes)
                   in the corresponding underlay topology it maps onto.
                   A node can map to zero, one, or more nodes below it;
                   accordingly there can be zero, one, or more elements in the list.
                   If there are specific layering requirements, for example
                   specific to a particular type of topology that only allows
                   for certain layering relationships, the choice
                   below can be augmented with additional cases.
                   A list has been chosen rather than a leaf-list in order
                   to provide room for augmentations, e.g. for
                   statistics or priorization information associated with
                   supporting nodes.";
               key "node-ref";
               leaf node-ref {
                   type node-ref;
               }
           }
       }

       grouping link-attributes {
           // This is a grouping, not defined inline with the link definition itself,
           // so it can be included in a notification, if needed
           leaf link-id {
               type link-id;
               description
                   "The identifier of a link in the topology.
                   A link is specific to a topology to which it belongs.";
           }
           container source {
               leaf source-node {
                   mandatory true;
                   type node-ref;
                   description
                       "Source node identifier, must be in same topology.";
               }
               leaf source-tp {
                   type tp-ref;
                   description
                       "Termination point within source node that terminates the link.";



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               }
           }
           container destination {
               leaf dest-node {
                   mandatory true;
                   type node-ref;
                   description
                       "Destination node identifier, must be in same topology.";
               }
               leaf dest-tp {
                   type tp-ref;
                   description
                       "Termination point within destination node that terminates the link.";
               }
           }
           list supporting-link {
               key "link-ref";
               leaf link-ref {
                   type link-ref;
               }
           }
       }


       container network-topology {
           list topology {
               description "
                   This is the model of an abstract topology.
                   A topology contains nodes and links.
                   Each topology MUST be identified by
                   unique topology-id for reason that a network could contain many
                   topologies.
               ";
               key "topology-id";
               leaf topology-id {
                   type topology-id;
                   description "
                       It is presumed that a datastore will contain many topologies. To
                       distinguish between topologies it is vital to have UNIQUE
                       topology identifiers.
                   ";
               }
               leaf server-provided {
                   type boolean;
                   config false;
                   description "
                       Indicates whether the topology is configurable by clients,
                       or whether it is provided by the server.  This leaf is



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                       populated by the server implementing the model.
                       It is set to false for topologies that are created by a client;
                       it is set to true otherwise.  If it is set to true, any
                       attempt to edit the topology MUST be rejected.
                   ";
               }
               container topology-types {
                   description
                       "This container is used to identify the type, or types
                       (as a topology can support several types simultaneously),
                       of the topology.
                       Topology types are the subject of several integrity constraints
                       that an implementing server can validate in order to
                       maintain integrity of the datastore.
                       Topology types are indicated through separate data nodes;
                       the set of topology types is expected to increase over time.
                       To add support for a new topology, an augmenting module
                       needs to augment this container with a new empty optional
                       container to indicate the new topology type.
                       The use of a container allows to indicate a subcategorization
                       of topology types.
                       The container SHALL NOT be augmented with any data nodes
                       that serve a purpose other than identifying a particular
                       topology type.
                   ";
               }
               list underlay-topology {
                   key "topology-ref";
                   leaf topology-ref {
                       type topology-ref;
                   }
                   // a list, not a leaf-list, to allow for potential augmentation
                   // with properties specific to the underlay topology,
                   // such as statistics, preferences, or cost.
                   description
                       "Identifies the topology, or topologies, that this topology
                       is dependent on.";
               }

               list node {
                   description "The list of network nodes defined for the topology.";
                   key "node-id";
                   uses node-attributes;
                   must "boolean(../underlay-topology[*]/node[./supporting-nodes/node-ref])";
                       // This constraint is meant to ensure that a referenced node is in fact
                       // a node in an underlay topology.
                   list termination-point {
                       description



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                           "A termination point can terminate a link.
                           Depending on the type of topology, a termination point could,
                           for example, refer to a port or an interface.";
                       key "tp-id";
                       uses tp-attributes;
                   }
               }

               list link {
                   description "
                       A Network Link connects a by Local (Source) node and
                       a Remote (Destination) Network Nodes via a set of the
                       nodes' termination points.
                       As it is possible to have several links between the same
                       source and destination nodes, and as a link could potentially
                       be re-homed between termination points, to ensure that we
                       would always know to distinguish between links, every link
                       is identified by a dedicated link identifier.
                       Note that a link models a point-to-point link, not a multipoint
                       link.
                       Layering dependencies on links in underlay topologies are
                       not represented as the layering information of nodes and of
                       termination points is sufficient.
                   ";
                   key "link-id";
                   uses link-attributes;
                   must "boolean(../underlay-topology/link[./supporting-link]";
                       // Constraint: any supporting link must be part of an underlay topology
                   must "boolean(../node[./source/source-node])";
                       // Constraint: A link must have as source a node of the same topology
                   must "boolean(../node[./destination/dest-node])";
                       // Constraint: A link must have as source a destination of the same topology
                   must "boolean(../node/termination-point[./source/source-tp])";
                       // Constraint: The source termination point must be contained in the source node
                   must "boolean(../node/termination-point[./destination/dest-tp])";
                       // Constraint: The destination termination point must be contained
                       // in the destination node
               }
           }
       }
   }

   <CODE ENDS>


5.  Layer 3 Unicast IGP Topology YANG Module

   <CODE BEGINS>



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   file "l3-unicast-igp-topology@2013-10-21.yang"
   module l3-unicast-igp-topology {
       yang-version 1;
       namespace "urn:TBD:params:xml:ns:yang:nt:l3-unicast-igp-topology";
       // replace with IANA namespace when assigned
       prefix "l3t";
       import network-topology {
           prefix "nt";
       }

       import ietf-inet-types {
           prefix "inet";
       }

       organization "TBD";
       contact "TBD";

       revision "2013-10-21" {
           description "Initial revision";
           reference "TBD";
       }

       typedef igp-event-type {
           description "IGP Event type for notifications";
               type enumeration {
                   enum "add" {
                       value 0;
                           description "An IGP node or link or prefix or termination-point has been added";
                   }
                   enum "remove" {
                       value 1;
                       description "An IGP node or link or prefix or termination-point has been removed";
                   }
                   enum "update" {
                       value 2;
                       description "An IGP node or link or prefix or termination-point has been updated";
                   }
               }
           } // igp-event-type

       identity flag-identity {
           description "Base type for flags";
       }
       identity undefined-flag {
           base "flag-identity";
       }

       typedef flag-type {



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           type identityref {
               base "flag-identity";
           }
       }

       grouping igp-prefix-attributes {
           leaf prefix {
               type inet:ip-prefix;
           }
           leaf metric {
               type uint32;
           }
           leaf-list flag {
               type flag-type;
           }
       }

       grouping l3-unicast-igp-topology-type {
           container l3-unicast-igp-topology {
               presence "indicates L3 Unicast IGP Topology";
           }
       }

       grouping igp-topology-attributes {
           container igp-topology-attributes {
               leaf name {
                   description "Name of the topology";
                       type string;
               }
               leaf-list flag {
                   description "Topology flags";
                   type flag-type;
               }
           }
       }

       grouping igp-node-attributes {
           container igp-node-attributes {
               leaf name {
                   description "Node name";
                   type inet:domain-name;
               }
               leaf-list flag {
                   description "Node operational flags";
                   type flag-type;
               }
               leaf-list router-id {
                   description "Router-id for the node";



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                   type inet:ip-address;
               }
               list prefix {
                   key "prefix";
                   uses igp-prefix-attributes;
               }
           }
       }

       grouping igp-link-attributes {
           container igp-link-attributes {
               leaf name {
                   description "Link Name";
                   type string;
               }
               leaf-list flag {
                   description "Link flags";
                   type flag-type;
               }
               leaf metric {
                   description "Link Metric";
                   type uint32 {
                       range "0..16777215"  {
                           description "
                           ";
                           // OSPF/ISIS supports max 3 byte metric.
                           // Ideally we would like this restriction to be
                           // defined in the derived models, however,
                           // we are not allowed to augment a "must" statement.
                       }
                   }
               }
           }
       } // grouping igp-link-attributes

       grouping igp-termination-point-attributes {
           container igp-termination-point-attributes {
               choice termination-point-type {
                   case ip {
                      leaf-list ip-address {
                       description "IPv4 or IPv6 address";
                       type inet:ip-address;
                       }
                   }
                   case unnumbered {
                       leaf unnumbered-id {
                       description "Unnumbered interface identifier";
                       type uint32;



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                       }
                   }
               }
           }
       } // grouping igp-termination-point-attributes


       augment "/nt:network-topology/nt:topology/nt:topology-types" {
           uses l3-unicast-igp-topology-type;
       }

       augment "/nt:network-topology/nt:topology" {
           when "nt:topology-types/l3-unicast-igp-topology";
           uses igp-topology-attributes;
       }

       augment "/nt:network-topology/nt:topology/nt:node" {
           when "../nt:topology-types/l3-unicast-igp-topology";
           uses igp-node-attributes;
       }
       augment "/nt:network-topology/nt:topology/nt:link" {
           when "../nt:topology-types/l3-unicast-igp-topology";
           uses igp-link-attributes;
       }
       augment "/nt:network-topology/nt:topology/nt:node/nt:termination-point" {
           when "../../nt:topology-types/l3-unicast-igp-topology";
           uses igp-termination-point-attributes;
       }

       notification igp-node-event {
           leaf igp-event-type {
               type igp-event-type;
           }
           leaf topology-ref {
               type nt:topology-ref;
           }
           uses l3-unicast-igp-topology-type;
           uses nt:node-attributes;
           uses igp-node-attributes;
       }

       notification igp-link-event {
           leaf igp-event-type {
               type igp-event-type;
           }
           leaf topology-ref {
               type nt:topology-ref;
           }



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           uses l3-unicast-igp-topology-type;
           uses nt:link-attributes;
           uses igp-link-attributes;
       }

       notification igp-prefix-event {
           leaf igp-event-type {
               type igp-event-type;
           }
           leaf topology-ref {
               type nt:topology-ref;
           }
           leaf node-ref {
               type nt:node-ref;
           }
           uses l3-unicast-igp-topology-type;
           container prefix {
               uses igp-prefix-attributes;
           }
       }

       notification termination-point-event {
           leaf igp-event-type {
               type igp-event-type;
           }
           leaf topology-ref {
               type nt:topology-ref;
           }
           leaf node-ref {
               type nt:node-ref;
           }
           uses l3-unicast-igp-topology-type;
           uses nt:tp-attributes;
           uses igp-termination-point-attributes;
       }
   }

   <CODE ENDS>


6.  OSPF Topology YANG Module

   <CODE BEGINS>
   file "ospf-topology@2013-10-21.yang"
   module ospf-topology {
       yang-version 1;
       namespace "urn:TBD:params:xml:ns:yang:ospf-topology";
       // replace with IANA namespace when assigned



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       prefix "ospf";

       import network-topology {
           prefix "nt";
       }

       import l3-unicast-igp-topology {
           prefix "l3t";
       }
       import ietf-inet-types {
           prefix "inet";
       }
       import ted {
           prefix "ted";
       }

       organization "TBD";
       contact "TBD";
       description "OSPF Topology model";

       revision "2013-10-21" {
           description "Initial revision";
           reference "TBD";
       }

       typedef area-id {
           description "OSPF Area ID";
           type uint32;
       }

       grouping ospf-topology-type {
           container ospf {
               presence "indiates OSPF Topology";
           }
       }

       augment "/nt:network-topology/nt:topology/nt:topology-types/l3t:l3-unicast-igp-topology" {
           uses ospf-topology-type;
       }

       augment "/nt:network-topology/nt:topology/l3t:igp-topology-attributes" {
           when "../nt:topology-types/l3t:l3-unicast-igp-topology/ospf";
           container ospf-topology-attributes {
               leaf area-id {
                   type area-id;
               }
           }
       }



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       augment "/nt:network-topology/nt:topology/nt:node/l3t:igp-node-attributes" {
           when "../../nt:topology-types/l3t:l3-unicast-igp-topology/ospf";
           uses ospf-node-attributes;
       }

       augment "/nt:network-topology/nt:topology/nt:link/l3t:igp-link-attributes" {
           when "../../nt:topology-types/l3t:l3-unicast-igp-topology/ospf";
           uses ospf-link-attributes;
       }

       augment "/nt:network-topology/nt:topology/nt:node/l3t:igp-node-attributes/l3t:prefix" {
           when "../../../nt:topology-types/l3t:l3-unicast-igp-topology/ospf";
           uses ospf-prefix-attributes;
       }

       grouping ospf-node-attributes {
           container ospf-node-attributes {
               choice router-type {
                   case abr {
                       leaf abr {
                           type empty;
                       }
                   }
                   case asbr {
                       leaf asbr {
                           type empty;
                       }
                   }
                   case internal {
                       leaf internal {
                           type empty;
                       }
                   }
                   case pseudonode {
                       leaf pseudonode {
                           type empty;
                       }
                   }
               }
               leaf dr-interface-id {
                   when "../router-type/pseudonode";
                   description "For pseudonodes, DR interface-id";
                   default "0";
                   type uint32;
               }
               leaf-list multi-topology-id {
                   description "List of Multi-Topology Identifier up-to 128 (0-127). RFC 4915";
                   max-elements "128";



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                   type uint8 {
                       range "0..127";
                   }
               }
               leaf capabilities {
                   description "OSPF capabilities as bit vector. RFC 4970";
                   type bits {
                       bit graceful-restart-capable {
                           position 0;
                       }
                       bit graceful-restart-helper {
                           position 1;
                       }
                       bit stub-router-support {
                           position 2;
                       }
                       bit traffic-engineering-support {
                           position 3;
                       }
                       bit point-to-point-over-lan {
                           position 4;
                       }
                       bit experimental-te {
                           position 5;
                       }
                   }
               }
               container ted {
                   uses ted:ted-node-attributes;
               }
           } // ospf
       } // ospf-node-attributes

       grouping ospf-link-attributes {
           container ospf-link-attributes {
               leaf multi-topology-id {
                   type uint8 {
                       range "0..127";
                   }
               }
               container ted {
                   uses ted:ted-link-attributes;
               }
           }
       } // ospf-link-attributes

       grouping ospf-prefix-attributes {
           container ospf-prefix-attributes {



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               leaf forwarding-address {
                   when "../../l3t:l3-unicast-igp-topology/l3t:ospf/l3t:router-type/l3t:asbr";
                   type inet:ipv4-address;
               }
           }
       }

       augment "/l3t:igp-node-event" {
           uses ospf-topology-type;
           uses ospf:ospf-node-attributes;
       }

       augment "/l3t:igp-link-event" {
           uses ospf-topology-type;
           uses ospf:ospf-link-attributes;
       }

       augment "/l3t:igp-prefix-event" {
           uses ospf-topology-type;
           uses ospf:ospf-prefix-attributes;
       }
   }

   <CODE ENDS>


7.  ISIS Topology YANG Module

   <CODE BEGINS>
   file "isis-topology@2013-10-21.yang"
   module isis-topology {
       yang-version 1;
       namespace "urn:TBD:params:xml:ns:yang:network:isis-topology";
       // replace with IANA namespace when assigned
       prefix "isis";
       import network-topology {
           prefix nt;
       }
       import l3-unicast-igp-topology {
           prefix igp;
       }
       import ted {
           prefix ted;
       }

       organization "TBD";
       contact "TBD";
       description "ISIS Topology model";



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       revision "2013-10-21" {
           description "Initial version";
       }
       typedef iso-system-id {
           description "ISO System ID. RFC 1237";
           type string {
               pattern '[0-9a-fA-F]{4}(\.[0-9a-fA-F]{4}){2}';
           }
       }

       typedef iso-pseudonode-id {
           description "ISO pseudonode id for broadcast network";
           type string {
               pattern '[0-9a-fA-F]{2}';
           }
       }
       typedef iso-net-id {
           description "ISO NET ID. RFC 1237";
           type string {
               pattern '[0-9a-fA-F]{2}((\.[0-9a-fA-F]{4}){6})';
           }
       }

       grouping isis-topology-type {
           container isis {
               presence "Indicates ISIS Topology";
           }
       }

       augment "/nt:network-topology/nt:topology/nt:topology-types/igp:l3-unicast-igp-topology" {
           uses isis-topology-type;
       }

       augment "/nt:network-topology/nt:topology/igp:igp-topology-attributes" {
           when "../nt:topology-types/l3t:l3-unicast-igp-topology/isis";
           container isis-topology-attributes {
               leaf net {
                   type iso-net-id;
               }
           }
       }

       augment "/nt:network-topology/nt:topology/nt:node/igp:igp-node-attributes" {
           when "../../nt:topology-types/l3t:l3-unicast-igp-topology/isis";
           uses isis-node-attributes;
       }

       augment "/nt:network-topology/nt:topology/nt:link/igp:igp-link-attributes" {



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           when "../../nt:topology-types/l3t:l3-unicast-igp-topology/isis";
           uses isis-link-attributes;
       }

       grouping isis-node-attributes {
           container isis-node-attributes {
               container iso {
                   leaf iso-system-id {
                       type iso-system-id;
                   }
                   leaf iso-pseudonode-id {
                       default "0";
                       type iso-pseudonode-id;
                   }
               }
               leaf-list net {
                   max-elements 3;
                   type iso-net-id;
               }
               leaf-list multi-topology-id {
                   description "List of Multi Topology Identifier upto 128 (0-127). RFC 4915";
                   max-elements "128";
                   type uint8 {
                       range "0..127";
                   }
               }
               choice router-type {
                   case level-2 {
                       leaf level-2 {
                           type empty;
                       }
                   }
                   case level-1 {
                       leaf level-1 {
                           type empty;
                       }
                   }
                   case level-1-2 {
                       leaf level-1-2 {
                           type empty;
                       }
                   }
               }
               container ted {
                   uses ted:ted-node-attributes;
               }
           }
       }



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       grouping isis-link-attributes {
           container isis-link-attributes {
               leaf multi-topology-id {
                   type uint8 {
                       range "0..127";
                   }
               }
               container ted {
                   uses ted:ted-link-attributes;
               }
           }
       }

       augment "/igp:igp-node-event" {
           uses isis-topology-type;
           uses isis-node-attributes;
       }

       augment "/igp:igp-link-event" {
           uses isis-topology-type;
           uses isis-link-attributes;
       }
   } // Module isis-topology

   <CODE ENDS>


8.  TED YANG Module

   <CODE BEGINS>
   file "ted@2013-10-21.yang"
   module ted {
     yang-version 1;
     namespace "urn:TBD:params:xml:ns:yang:network:ted";
     // replace with IANA namespace when assigned
     prefix ted;

     import ietf-inet-types {
       prefix inet;
     }

     organization "TBD";
     contact
       "TBD";
     description
       "Helper module to hold TED attributes for OSPF/ISIS";

     revision 2013-10-21 {



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       description
         "Initial revision";
     }

     typedef switching-capabilities {
       description
         "Switching Capabilities of an interface.";
       reference
         "RFC 5307: IS-IS Extensions in Support of Generalized
          Multi-Protocol Label Switching (GMPLS)";
       type enumeration {
         enum "PSC-1" {
           description
             "Packet-Switch Capable-1 (PSC-1)";
           value 1;
         }
         enum "PSC-2" {
           description
             "Packet-Switch Capable-2 (PSC-2)";
           value 2;
         }
         enum "PSC-3" {
           description
             "Packet-Switch Capable-3 (PSC-3)";
           value 3;
         }
         enum "PSC-4" {
           description
             "Packet-Switch Capable-4 (PSC-4)";
           value 4;
         }
         enum "L2SC" {
           description
             "Layer-2 Switch Capable (L2SC)";
           value 51;
         }
         enum "TDM" {
           description
             "Time-Division-Multiplex Capable (TDM)";
           value 100;
         }
         enum "LSC" {
           description
             "Lambda-Switch Capable (LSC)";
           value 150;
         }
         enum "FSC" {
           description



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             "Fiber-Switch Capable (FSC)";
           value 200;
         }
       }
     }

     typedef pcc-capabilities {
       description
         "Path Computation Capabilities.";
       reference
         "RFC 5088, draft-ietf-pce-disco-protoc-isis-07.txt
          OSPF/ISIS Protocol Extensions for Path Computation Element (PCE) Discovery.";
       type bits {
         bit path-computation-with-gmpls-link-constraints {
           position 0;
         }
         bit bidirectional-path-computation {
           position 1;
         }
         bit diverse-path-computation {
           position 2;
         }
         bit load-balanced-path-computation {
           position 3;
         }
         bit synchronized-path-computation {
           position 4;
         }
         bit support-for-multiple-objective-functions {
           position 5;
         }
         bit support-for-additive-path-constraints {
           position 6;
         }
         bit support-for-request-prioritization {
           position 7;
         }
         bit support-for-multiple-requests-per-message {
           position 8;
         }
       }
     }

     grouping ted-node-attributes {
       description
         "Identifier to uniquely identify a node in TED";
       reference "RFC 5305, RFC 6119: IPv6 Traffic Engineering in IS-IS/OSPF";
       leaf te-router-id-ipv4 {



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         description
           "Globally unique IPv4 Traffic Engineering Router ID.";
         type inet:ipv4-address;
       }
       leaf te-router-id-ipv6 {
         description
           "Globally unique IPv6 Traffic Engineering Router ID";
         type inet:ipv6-address;
       }
       list ipv4-local-address {
         description
           "List of IPv4 Local Address(OSPF). RFC 5786";
         key "ipv4-prefix";
         leaf ipv4-prefix {
           description
             "Local IPv4 address for the node";
           type inet:ipv4-prefix;
         }
       }
       list ipv6-local-address {
         description
           "List of IPv6 Local Address.";
         reference
           "RFC 5786: Advertising a Router's Local Addresses
            in OSPF Traffic Engineering (TE) Extensions";
         key "ipv6-prefix";
         leaf ipv6-prefix {
           description
             "Local IPv6 address for the node";
           type inet:ipv6-prefix;
         }
         leaf prefix-option {
           description
             "IPv6 prefix option.";
           type uint8;
         }
       }
       leaf pcc-capabilities {
         description
           "OSPF/ISIS PCC capabilities";
         type pcc-capabilities;
       }
     }

     grouping ted-link-attributes {
       description
         "TED Attributes associated with the link.";
       reference "RFC 3630, RFC 3784: IS-IS / OSPF Traffic Engineering (TE)";



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       leaf color {
         description
           "Administrative group or color of the link";
         type uint32;
       }
       leaf max-link-bandwidth {
         description
           "Maximum bandwidth that can be see on this link in this direction. Units in bytes per second";
         type decimal64 {
           fraction-digits 2;
         }
       }
       leaf max-resv-link-bandwidth {
         description
           "Maximum amount of bandwidth that can be reserved in this direction in this link. Units in bytes per second";
         type decimal64 {
           fraction-digits 2;
         }
       }
       list unreserved-bandwidth {
         description
           "Unreserved bandwidth for 0-7 priority levels. Units in bytes per second";
         max-elements "8";
         key "priority";
         leaf priority {
           type uint8 {
             range "0..7";
           }
         }
         leaf bandwidth {
           description
             "Unreserved bandwidth for this level";
           type decimal64 {
             fraction-digits 2;
           }
         }
       }
       leaf te-default-metric {
         description
           "Traffic Engineering Metric";
         type uint32;
       }
       container srlg {
         description
           "Shared Risk Link Group Attributes";
         uses srlg-attributes;
       }
     }



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     grouping srlg-attributes {
       description
         "Shared Risk Link Group Attributes";
       reference
         "RFC 5307, RFC 4203: ISIS / OSPF Extensions in Support of
          Generalized Multi-Protocol Label Switching (GMPLS)";
       list interface-switching-capabilities {
         description
           "List of interface capabilities for this interface";
         key "switching-capability";
         leaf switching-capability {
           description
             "Switching Capability for this interface";
           type ted:switching-capabilities;
         }
         leaf encoding {
           description
             "Encoding supported by this interface";
           type uint8;
         }
         list max-lsp-bandwidth {
           description
             "Maximum LSP Bandwidth at priorities 0-7";
           max-elements "8";
           key "priority";
           leaf priority {
             type uint8 {
               range "0..7";
             }
           }
           leaf bandwidth {
             description
               "Max LSP Bandwidth for this level";
             type decimal64 {
               fraction-digits 2;
             }
           }
         }
         container packet-switch-capable {
           when "../switching-capability = PSC-1 or ../switching-capability = PSC-2 or ../switching-capability = PSC-3 or ../switching-capability = PSC-4";
           description
             "Interface has packet-switching capabilities";
           leaf minimum-lsp-bandwidth {
             description
               "Minimum LSP Bandwidth. Units in bytes per second";
             type decimal64 {
               fraction-digits 2;
             }



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           }
           leaf interface-mtu {
             description
               "Interface MTU";
             type uint16;
           }
         }
         container time-division-multiplex-capable {
           when "../switching-capability = TDM";
           description
             "Interface has time-division multiplex capabilities";
           leaf minimum-lsp-bandwidth {
             description
               "Minimum LSP Bandwidth. Units in bytes per second";
             type decimal64 {
               fraction-digits 2;
             }
           }
           leaf indication {
             description
               "Indication whether the interface supports Standard or Arbitrary SONET/SDH";
             type uint16;
           }
         }
       }
       list srlg-values {
         description
           "List of Shared Risk Link Group this interface belongs to.";
         key "srlg-value";
         leaf srlg-value {
           description
             "Shared Risk Link Group value";
           type uint32;
         }
       }
       leaf link-protection-type {
         description
           "Link Protection Type desired for this link";
         type uint16;
       }
     }
   }

   <CODE ENDS>


9.  Security Considerations




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   The transport protocol used for sending the topology data MUST
   support authentication and SHOULD support encryption.  The data-model
   by itself does not create any security implications.

10.  Contributors

   The model presented in this paper was contributed to by more people
   than can be listed on the author list.  Additional contributors
   include:

   o  Ken Gray, Juniper Networks

   o  Tom Nadeau, Juniper Networks

   o  Aleksandr Zhdankin, Cisco

11.  Acknowledgements

   We wish to acknowledge the helpful contributions, comments, and
   suggestions that were received from Ladislav Lhotka, Andy Bierman,
   Carlos Pignataro, and Juergen Schoenwaelder.

12.  References

12.1.  Normative References

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2178]  Moy, J., "OSPF Version 2", RFC 2178, July 1997.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6021]  Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

12.2.  Informative References

   [I-D.bierman-netconf-restconf]
              Bierman, A., Bjorklund, M., Watsen, K., and R. Fernando,
              "RESTCONF Protocol", draft-bierman-netconf-restconf-02
              (work in progress), October 2013.



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   [I-D.ietf-netmod-interfaces-cfg]
              Bjorklund, M., "A YANG Data Model for Interface
              Management", draft-ietf-netmod-interfaces-cfg-12 (work in
              progress), July 2013.

   [I-D.lhotka-netmod-yang-json]
              Lhotka, L., "Modeling JSON Text with YANG", draft-lhotka-
              netmod-yang-json-02 (work in progress), September 2013.

Authors' Addresses

   Alexander Clemm
   Cisco

   EMail: alex@cisco.com


   Hariharan Ananthakrishnan
   Juniper Networks

   EMail: hanantha@juniper.net


   Jan Medved
   Cisco

   EMail: jmedved@cisco.com


   Tony Tkacik
   Cisco

   EMail: ttkacik@cisco.com


   Robert Varga
   Pantheon Technologies SRO

   EMail: robert.varga@pantheon.sk


   Nitin Bahadur
   Juniper Networks

   EMail: nitinb@juniper.net






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