NETMOD                                                         L. Lhotka
Internet-Draft                                                    CZ.NIC
Intended status: Standards Track                       February 23,                           July 13, 2013
Expires: August 27, 2013 January 14, 2014

                A YANG Data Model for Routing Management
                    draft-ietf-netmod-routing-cfg-09
                    draft-ietf-netmod-routing-cfg-10

Abstract

   This document contains a specification of three YANG modules.
   Together they form the core routing data model which serves as a
   framework for configuring and managing a routing subsystem.  It is
   expected that these modules will be augmented by additional YANG
   modules defining data models for individual routing protocols and
   other related functions.  The core routing data model provides common
   building blocks for such extensions - router instances, routes,
   routing tables, routing protocols and route filters.

Status of this Memo

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   This Internet-Draft will expire on August 27, 2013. January 14, 2014.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology and Notation . . . . . . . . . . . . . . . . . . .  5
     2.1.  Glossary of New Terms  . . . . . . . . . . . . . . . . . .  5
     2.2.  Tree Diagrams  . . . . . . . . . . . . . . . . . . . . . .  6
     2.3.  Prefixes in Data Node Names  . . . . . . . . . . . . . . .  6
   3.  Objectives . . . . . . . . . . . . . . . . . . . . . . . . . .  8
   4.  The Design of the Core Routing Data Model  . . . . . . . . . .  9
     4.1.  Router . . . . . . . . . . . . . . . . . . . . . . . . . . 12
       4.1.1.  Configuration  Parameters of IPv6 Router Interfaces . . . . . . . 12 . . 13
     4.2.  Routes . . . . . . . . . . . . . . . . . . . . . . . . . . 14 15
     4.3.  Routing Tables . . . . . . . . . . . . . . . . . . . . . . 14 15
       4.3.1.  User-Defined Routing Tables  . . . . . . . . . . . . . 16
     4.4.  Routing Protocols  . . . . . . . . . . . . . . . . . . . . 16 17
       4.4.1.  Routing Pseudo-Protocols . . . . . . . . . . . . . . . 16 17
       4.4.2.  Defining New Routing Protocols . . . . . . . . . . . . 17 18
     4.5.  Route Filters  . . . . . . . . . . . . . . . . . . . . . . 18 19
     4.6.  RPC Operations . . . . . . . . . . . . . . . . . . . . . . 19 20
   5.  Interactions with Other YANG Modules . . . . . . . . . . . . . 20 21
     5.1.  Module "ietf-interfaces" . . . . . . . . . . . . . . . . . 20 21
     5.2.  Module "ietf-ip" . . . . . . . . . . . . . . . . . . . . . 20 21
   6.  Routing YANG Module  . . . . . . . . . . . . . . . . . . . . . 22 23
   7.  IPv4 Unicast Routing YANG Module . . . . . . . . . . . . . . . 36 42
   8.  IPv6 Unicast Routing YANG Module . . . . . . . . . . . . . . . 40 46
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 50 59
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 52 61
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 53 62
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54 63
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 54 63
     12.2. Informative References . . . . . . . . . . . . . . . . . . 54 63
   Appendix A.  The Complete Data Tree Trees . . . . . . . . . . . . . . . 64
     A.1.  Configuration Data . . . . . . . . . . . . . . . . . . . . 55 64
     A.2.  Operational State Data . . . . . . . . . . . . . . . . . . 65
   Appendix B.  Example: Adding a New Routing Protocol  . . . . . . . 57 68
   Appendix C.  Example: NETCONF <get> Reply  . . . . . . . . . . . . 60 71
   Appendix D.  Change Log  . . . . . . . . . . . . . . . . . . . . . 65 77
     D.1.  Changes Between Versions -09 and -10 . . . . . . . . . . . 77
     D.2.  Changes Between Versions -08 and -09 . . . . . . . . . . . 65
     D.2. 77
     D.3.  Changes Between Versions -07 and -08 . . . . . . . . . . . 65
     D.3. 77
     D.4.  Changes Between Versions -06 and -07 . . . . . . . . . . . 65
     D.4. 77
     D.5.  Changes Between Versions -05 and -06 . . . . . . . . . . . 65
     D.5. 78
     D.6.  Changes Between Versions -04 and -05 . . . . . . . . . . . 66
     D.6. 78
     D.7.  Changes Between Versions -03 and -04 . . . . . . . . . . . 67
     D.7. 79
     D.8.  Changes Between Versions -02 and -03 . . . . . . . . . . . 67
     D.8. 79
     D.9.  Changes Between Versions -01 and -02 . . . . . . . . . . . 68
     D.9. 80
     D.10. Changes Between Versions -00 and -01 . . . . . . . . . . . 68 80
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 69 82

1.  Introduction

   This document contains a specification of the following YANG modules:

   o  Module "ietf-routing" provides generic components of a routing
      data model.

   o  Module "ietf-ipv4-unicast-routing" augments the "ietf-routing"
      module with additional data specific to IPv4 unicast.

   o  Module "ietf-ipv6-unicast-routing" augments the "ietf-routing"
      module with additional data specific to IPv6 unicast, including
      the router configuration variables required by [RFC4861].

   These modules together define the so-called core routing data model,
   which is proposed as a basis for the development of data models for
   configuration and management of more sophisticated routing systems.
   While these three modules can be directly used for simple IP devices
   with static routing, their main purpose is to provide essential
   building blocks for more complicated setups involving multiple
   routing protocols, multicast routing, additional address families,
   and advanced functions such as route filtering or policy routing.  To
   this end, it is expected that the core routing data model will be
   augmented by numerous modules developed by other IETF working groups.

2.  Terminology and Notation

   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 [RFC2119].

   The following terms are defined in [RFC6241]:

   o  client

   o  message

   o  protocol operation

   o  server

   The following terms are defined in [RFC6020]:

   o  augment

   o  configuration data

   o  data model

   o  data node

   o  feature

   o  mandatory node

   o  module

   o  state data

   o  RPC operation

2.1.  Glossary of New Terms

   active route:  a route that is actually used for sending packets.  If
      there are multiple candidate routes with a matching destination
      prefix, then it is up to the routing algorithm to select the
      active route (or several active routes in the case of multi-path
      routing).

   core routing data model:  YANG data model resulting from the
      combination of "ietf-routing", "ietf-ipv4-unicast-routing" and
      "ietf-ipv6-unicast-routing" modules.

   direct route:  a route to a directly connected network.

   system-controlled entry:  An entry of a list in operational state
      data ("config false") that is created by the system independently
      of what has been explicitly configured.  An example is the default
      routing table.  A client cannot cause this entry to be deleted but
      may be able to configure it.

   user-controlled entry:  An entry of a list in operational state data
      ("config false") that is created and deleted as a direct
      consequence of certain configuration changes.  An example is an
      additional user-defined routing table.

2.2.  Tree Diagrams

   A simplified graphical representation of the complete data tree is
   presented in Appendix A, and similar diagrams of its various subtrees
   appear in the main text.  The meaning of the symbols in these
   diagrams is as follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Abbreviations before data node names: "rw" means configuration
      (read-write) and "ro" state data (read-only).

   o  Symbols after data node names: "?" means an optional node and "*"
      denotes a "list" or "leaf-list".

   o  Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

   o  Ellipsis ("...") stands for contents of subtrees that are not
      shown.

2.3.  Prefixes in Data Node Names

   In this document, names of data nodes, RPC methods and other data
   model objects are used mostly without a prefix, as long as it is
   clear from the context in which YANG module each name is defined.
   Otherwise, names are prefixed using the standard prefix associated
   with the corresponding YANG module, as shown in Table 1.

           +--------+---------------------------+--------------+
           | Prefix | YANG module               | Reference    |
           +--------+---------------------------+--------------+
           | ianaaf | iana-afn-safi             | [IANA-IF-AF] [IANA-AF]    |
           |        |                           |              |
           | if     | ietf-interfaces           | [YANG-IF]    |
           |        |                           |              |
           | ip     | ietf-ip                   | [YANG-IP]    |
           |        |                           |              |
           | rt     | ietf-routing              | Section 6    |
           |        |                           |              |
           | v4ur   | ietf-ipv4-unicast-routing | Section 7    |
           |        |                           |              |
           | v6ur   | ietf-ipv6-unicast-routing | Section 8    |
           |        |                           |              |
           | yang   | ietf-yang-types           | [RFC6021bis] |
           |        |                           |              |
           | inet   | ietf-inet-types           | [RFC6021bis] |
           +--------+---------------------------+--------------+

             Table 1: Prefixes and corresponding YANG modules

3.  Objectives

   The initial design of the core routing data model was driven by the
   following objectives:

   o  The data model should be suitable for the common address families,
      in particular IPv4 and IPv6, and for unicast and multicast
      routing, as well as Multiprotocol Label Switching (MPLS).

   o  Simple routing setups, such as static routing, should be
      configurable in a simple way, ideally without any need to develop
      additional YANG modules.

   o  On the other hand, the core routing framework must allow for
      complicated setups involving multiple routing tables and multiple
      routing protocols, as well as controlled redistributions of
      routing information.

   o  Device vendors will want to map the data models built on this
      generic framework to their proprietary data models and
      configuration interfaces.  Therefore, the framework should be
      flexible enough to facilitate such a mapping and accommodate data
      models with different logic.

4.  The Design of the Core Routing Data Model

   The core routing data model consists of three YANG modules.  The
   first module, "ietf-routing", defines the generic components of a
   routing system.  The other two modules, "ietf-ipv4-unicast-routing"
   and "ietf-ipv6-unicast-routing", augment the "ietf-routing" module
   with additional data nodes that are needed for IPv4 and IPv6 unicast
   routing, respectively.  An  Figures 1 and 2 show abridged view views of the
   configuration and operational state data hierarchy is
   shown in Figure 1. hierarchies.  See Appendix A
   for the complete data tree. trees.

   +--rw routing
      +--rw router router* [name]
      |  +--rw name
      |  +--rw type?
      |  +--rw enabled?
      |  +--rw router-id?
      |  +--rw description?
      |  +--rw main-routing-tables default-routing-tables
      |  |  +--rw main-routing-table default-routing-table* [address-family safi]
      |  |     +--rw address-family
      |  |     +--rw safi
      |  |     +--rw name? name
      |  +--rw interfaces
      |  |  +--rw interface interface* [name]
      |  |     +--rw name
      |  |     +--rw v6ur:ipv6-router-advertisements
      |  |           ...
      |  +--rw routing-protocols
      |     +--rw routing-protocol routing-protocol* [name]
      |        +--rw name
      |        +--rw description?
      |        +--rw enabled?
      |        +--rw type
      |        +--rw connected-routing-tables
      |        |     ...
      |        +--rw static-routes
      |              ...
      +--rw routing-tables
      |  +--rw routing-table routing-table* [name]
      |     +--rw name
      |     +--rw address-family
      |     +--rw safi
      |     +--rw description?
      |     +--ro routes
      |     |  +--ro route
      |     |        ...
      |     +--rw recipient-routing-tables
      |        +--rw recipient-routing-table recipient-routing-table* [name]
      |              ...
      +--rw route-filters
         +--rw route-filter route-filter* [name]
            +--rw name
            +--rw description?
            +--rw type

                  Figure 1: Data hierarchy of the core routing data model.

   As can be seen from Figure 1, the core routing Configuration data model introduces
   several generic components of a routing framework: routers, routing
   tables containing lists of routes, routing protocols and route
   filters. hierarchy.

   +--ro routing-state
      +--ro router* [name]
      |  +--ro name
      |  +--ro type?
      |  +--ro router-id?
      |  +--ro default-routing-tables
      |  |  +--ro default-routing-table* [address-family safi]
      |  |     +--ro address-family
      |  |     +--ro safi
      |  |     +--ro name
      |  +--ro interfaces
      |  |  +--ro interface* [name]
      |  |     +--ro name
      |  |     +--ro v6ur:ipv6-router-advertisements
      |  |           ...
      |  +--ro routing-protocols
      |     +--ro routing-protocol* [name]
      |        +--ro name
      |        +--ro type
      |        +--ro connected-routing-tables
      |              ...
      +--ro routing-tables
      |  +--ro routing-table* [name]
      |     +--ro name
      |     +--ro address-family
      |     +--ro safi
      |     +--ro routes
      |     |  +--ro route*
      |     |        ...
      |     +--ro recipient-routing-tables
      |        +--ro recipient-routing-table* [name]
      |              ...
      +--ro route-filters
         +--ro route-filter* [name]
            +--ro name
            +--ro type

                Figure 2: Operational state data hierarchy.

   As can be seen from Figures 1 and 2, the core routing data model
   introduces several generic components of a routing framework:
   routers, routing tables containing lists of routes, routing protocols
   and route filters.  The following subsections describe these
   components in more detail.

   By combining the components in various ways, and possibly augmenting
   them with appropriate contents defined in other modules, various
   routing setups systems can be realized.

   +--------+
   | direct |    +---+    +--------------+    +---+    +--------------+
   | routes |--->| F |--->|              |<---| F |<---|              |
   +--------+    +---+    |    main   default    |    +---+    |  additional  |
                          |   routing    |             |   routing    |
   +--------+    +---+    |    table     |    +---+    |    table     |
   | static |--->| F |--->|              |--->| F |--->|              |
   | routes |    +---+    +--------------+    +---+    +--------------+
   +--------+                 ^      |                     ^      |
                              |      v                     |      v
                            +---+  +---+                 +---+  +---+
                            | F |  | F |                 | F |  | F |
                            +---+  +---+                 +---+  +---+
                              ^      |                     ^      |
                              |      v                     |      v
                            +----------+                 +----------+
                            | routing  |                 | routing  |
                            | protocol |                 | protocol |
                            +----------+                 +----------+

                Figure 2: 3: Example setup of a routing system

   The example in Figure 2 3 shows a typical (though certainly not the
   only possible) organization of a more complex routing subsystem for a
   single address family.  Several of its features are worth mentioning:

   o  Along with the main default routing table, which must is always be present, an
      additional routing table is configured.

   o  Each routing protocol instance, including the "static" and
      "direct" pseudo-protocols, is connected to one routing table with
      which it can exchange routes (in both directions, except for the
      "static" and "direct" pseudo-protocols).

   o  Routing tables may also be connected to each other and exchange
      routes in either direction (or both).

   o  Route exchanges along all connections may be controlled by means
      of route filters, denoted by "F" in Figure 2. 3.

4.1.  Router

   Each router instance in the core routing data model represents a
   logical router.  The exact semantics of this term is left to
   implementations.  For example, router instances may be completely
   isolated virtual routers or, alternatively, they may internally share
   certain information.

   A router instance together with its operational status is represented
   as an entry of the list "/routing-state/router", and identified by a
   unique name.  Configuration of that router instance appears as entry
   of the list "/routing/router" whose key is the router instance name.

   An implementation MAY support multiple types of logical routers
   simultaneously.  Instances of all router types are organized as
   entries of the same flat "router" list.  In order to discriminate
   router instances belonging to different types, the "type" leaf is
   defined as a child of the "router" node.

   An implementation MAY create one or more system-controlled router
   entries, and MAY also pose restrictions on allowed router types and
   on the number of supported instances for each type.  For example, a
   simple router implementation may support only one system-controlled
   router instance of the default type "standard-router". "standard-router" and may not
   allow creation of any user-controlled instances.

   Each network layer interface has to be assigned to one or more router
   instances in order to be able to participate in packet forwarding,
   routing protocols and other operations of those router instances.
   The assignment is accomplished by creating a corresponding entry in
   the list of router interfaces ("rt:interface").  The key of the list
   entry is the name of a configured network layer interface, i.e., the
   value of a node /if:interfaces/if:interface/if:name defined in see the
   "ietf-interfaces" module [YANG-IF].

   In YANG terms, the list of router interfaces is modeled as the "list"
   node rather than "leaf-list" in order to allow for adding, via
   augmentation, other configuration or state data related to the
   corresponding router interface.

   Implementations MAY specify additional rules for the assignment of
   interfaces to logical routers.  For example, it may be required that
   the sets of interfaces assigned to different logical routers be
   disjoint.

4.1.1.  Configuration  Parameters of IPv6 Router Interfaces

   The module "ietf-ipv6-unicast-routing" augments the definition of the
   data node "rt:interface" "rt:interface", in both configuration and operational state
   data, with definitions of the following
   configuration variables as required by
   [RFC4861], sec. 6.2.1:

   o  send-advertisements,

   o  max-rtr-adv-interval,
   o  min-rtr-adv-interval,

   o  managed-flag,

   o  other-config-flag,

   o  link-mtu,

   o  reachable-time,

   o  retrans-timer,

   o  cur-hop-limit,

   o  default-lifetime,

   o  prefix-list: a list of prefixes to be advertised.

      The following parameters are associated with each prefix in the
      list:

      *  valid-lifetime,

      *  on-link-flag,

      *  preferred-lifetime,

      *  autonomous-flag.

   The definitions and descriptions of the above parameters can be found
   in the text of the module "ietf-ipv6-unicast-routing" (Section 8).

   NOTES:

   1.  The "IsRouter" flag, which is also required by [RFC4861], is
       implemented in the "ietf-ip" module [YANG-IP] (leaf "ip:
       forwarding").

   2.  The original specification [RFC4861] allows the implementations
       to decide whether the "valid-lifetime" and "preferred-lifetime"
       parameters remain the same in consecutive advertisements, or
       decrement in real time.  However, the latter behavior seems
       problematic because the values might be reset again to the
       (higher) configured values after a configuration is reloaded.
       Moreover, no implementation is known to use the decrementing
       behavior.  The "ietf-ipv6-unicast-routing" module therefore
       assumes the former behavior with constant values.

4.2.  Routes

   Routes are basic elements of information in a routing system.  The
   core routing data model defines only the following minimal set of
   route attributes:

   o  "dest-prefix": IP prefix specifying the set of destination
      addresses for which the route may be used.  This attribute is
      mandatory.

   o  "next-hop": IP address of an adjacent router or host to which
      packets with destination addresses belonging to "dest-prefix"
      should be sent.

   o  "outgoing-interface": network interface that should be used for
      sending packets with destination addresses belonging to "dest-
      prefix".

   The above list of route attributes suffices for a simple static
   routing configuration.  It is expected that future modules defining
   routing protocols will add other route attributes such as metrics or
   preferences.

   Routes and their attributes are used both in configuration data, for
   example as manually configured static routes, and in operational
   state data, for example as entries in routing tables.

4.3.  Routing Tables

   Routing tables are lists of routes complemented with administrative
   data, namely:

   o  "source-protocol": name type of the routing protocol from which the
      route was originally obtained.

   o  "last-updated": the date and time when the route was last updated,
      or inserted into the routing table.

   Each routing table must contain only routes of the same address
   family.  Address family information consists of two parameters -
   "address-family" and "safi" (Subsequent Address Family Identifier,
   SAFI).  The permitted values for these two parameters are defined by
   IANA and represented using YANG enumeration types "ianaaf:address-
   family" datatypes "ianaaf:
   address-family" and "ianaaf:subsequent-address-family" [IANA-IF-AF]. [IANA-AF].

   In the core routing data model, routing tables are operational state
   data represented as entries of the "routing-table" node represents
   configuration while the descendant list of routes is defined as state
   data. "/routing-state/
   routing-tables/routing-table".  The contents of route lists routing tables are
   controlled and manipulated by routing protocol operations which may
   result in route additions, removals and modifications.  This also
   includes manipulations via the "static" and/or "direct" pseudo-protocols, pseudo-
   protocols, see Section 4.4.1.

   In order to activate an address family for use within a router
   instance, a client configures an entry of the list /routing/router/
   main-routing-tables/main-routing-table.  This entry contains a
   reference to a routing table which henceforth serves as the so-called
   main routing table for the router instance and address family.
   Section 4.4 explains the role of main routing tables.

   Routing tables are global, which means that a configured routing table may be
   used by any or all router instances.

   Server implementations  However, an implementation MAY pose
   specify rules and restrictions regarding the number of
   supported for sharing routing tables, and rules tables among
   router instances.

   Each router instance must have, for configuration and use every supported address family,
   one routing table selected as the so-called default routing table.
   This selection is recorded in the list "default-routing-table".  The
   role of default routing tables.  For example:

   o  A server may support no more than tables is explained in Section 4.4.

   Simple router implementations will typically create one system-
   controlled routing table per supported address
      family.

   o  Router instances (of family, and declare it
   as a certain type) may not be allowed to share
      routing tables, i.e., each default routing table is used by no more than
      one (via a system-controlled entry of the
   "default-routing-table" list).

4.3.1.  User-Defined Routing Tables

   More complex router instance.

   For servers supporting implementations allow for multiple routing tables
   per address family, family that are used for policy routing and other
   purposes.  If it is the case, the NETCONF server SHALL advertise the
   feature "user-defined-routing-tables".  This feature activates
   additional nodes in both configuration and operational state data,
   and enables the client to:

   o  Configure new user-controlled routing tables can be configured by creating new entries
      in the
   "routing-table" list, either "/routing/routing-tables/routing-table" list.

   o  Configure any (system-controlled or user-controlled) routing table
      as the default routing table for an address family.

   o  Connect a part of factory-default
   configuration, or by routing protocol instance to a client's action.

   The way how non-default routing table
      (see Section 4.4).

   o  Configure a routing system uses information from table as a recipient routing tables for
   actual packet forwarding is outside the scope table of this document. another
      routing table (see below).

   Every routing table can serve as a source of routes for other routing
   tables.
   tables of the same address family.  To achieve this, one or more
   recipient routing tables may be specified in the configuration of the
   source routing table.  Optionally, a route filter may be configured
   for any or all recipient routing tables.  Such a route filter then
   selects and/or manipulates the routes that are passed between the
   source and recipient routing table.

   A routing table MUST NOT appear among its own recipient routing
   tables.  A recipient routing table also MUST be of the same address
   family as its source routing table.

4.4.  Routing Protocols

   The core routing data model provides an open-ended framework for
   defining multiple routing protocol instances within each a router
   instance.  Each routing protocol instance MUST be assigned a type,
   which is an identity derived from the "rt:routing-protocol" base
   identity.  The core routing data model defines two identities for the
   direct and static pseudo-protocols (Section 4.4.1).

   Each routing protocol instance is connected to exactly one routing
   table for each address family that the routing protocol instance
   supports.  Routes learned from the network by a routing protocol are
   normally installed into the connected routing table(s) and,
   conversely, routes from the connected routing table(s) are normally
   injected into the routing protocol.  However, routing protocol
   implementations MAY specify rules that restrict this exchange of
   routes in either direction (or both directions).

   A

   On devices supporting the "user-defined-routing-tables" feature, a
   routing table (system-controlled or user-controlled) is connected to
   a routing protocol instance by
   creating configuring a corresponding entry in
   the "connected-routing-table" list.  If such an entry is not
   configured for an address family, then the
   main default routing table MUST
   be used as the connected routing table for this address family.

   In addition, two independent route filters (see Section 4.5) may be
   configured for each connected routing table to apply client-defined
   policies controlling the exchange of routes in both directions
   between the routing protocol instance and the connected routing
   table:

   o  import filter controls which routes are passed from the routing
      protocol instance to the connected routing table,

   o  export filter controls which routes the routing protocol instance
      receives from the connected routing table.

   Note that the terms import and export are used from the viewpoint of
   a routing table.

4.4.1.  Routing Pseudo-Protocols

   The core routing data model defines two special routing protocol
   types - "direct" and "static".  Both are in fact pseudo-protocols,
   which means that they are confined to the local device and do not
   exchange any routing information with neighboring routers.  Routes
   from both "direct" and "static" protocol instances are passed to the
   connected routing table (subject to route filters, if any), but an
   exchange in the opposite direction is not allowed.

   Every router instance MUST implement exactly one instance of the
   "direct" pseudo-protocol type.  The name of this instance MUST also
   be "direct".  It is the source of direct routes for all configured
   address families.  Direct routes are normally supplied by the
   operating system kernel, based on the configuration of network
   interface addresses, see Section 5.2.  The "direct" pseudo-protocol
   MUST always be connected to the main default routing tables of all
   supported address families.  Unlike other routing protocol types,
   this connection cannot be changed in the configuration.  Direct
   routes MAY be filtered before they appear in the main default routing
   table.

   A pseudo-protocol of the type "static" allows for specifying routes
   manually.  It MAY be configured in zero or multiple instances,
   although a typical configuration will have exactly one instance per
   logical router.

   Static routes are configured within the "static-routes" container,
   see Figure 3. 4.

   +--rw static-routes
      +--rw v4ur:ipv4
      |  +--rw v4ur:route v4ur:route* [id]
      |     +--rw v4ur:id
      |     +--rw v4ur:description?
      |     +--rw v4ur:outgoing-interface?
      |     +--rw v4ur:dest-prefix
      |     +--rw v4ur:next-hop?
      +--rw v6ur:ipv6
         +--rw v6ur:route v6ur:route* [id]
            +--rw v6ur:id
            +--rw v6ur:description?
            +--rw v6ur:outgoing-interface?
            +--rw v6ur:dest-prefix
            +--rw v6ur:next-hop?

              Figure 3: 4: Structure of "static-routes" subtree.

4.4.2.  Defining New Routing Protocols

   It is expected that future YANG modules will create data models for
   additional routing protocol types.  Such a new module has to define
   the protocol-specific configuration and state data, and it has to fit
   it into the core routing framework in the following way:

   o  A new identity MUST be defined for the routing protocol and its
      base identity MUST be set to "rt:routing-protocol", or to an
      identity derived from "rt:routing-protocol".

   o  Additional route attributes MAY be defined, preferably in one
      place by means of defining a YANG grouping.  The new attributes
      have to be inserted as state data by augmenting the definitions of
      the nodes

          /rt:routing-tables/rt:routing-table/rt:route

      and

          /rt:active-route/rt:output/rt:route,

      and possibly other places in the configuration, state data and RPC
      input or output.

   o  Configuration parameters and and/or state data for the new protocol
      can be defined by augmenting the "routing-protocol" data node. node
      under both "/routing" and "/routing-state".

   o  Per-interface configuration, including activation of the routing
      protocol on individual interfaces, can use references to entries
      in the list of router interfaces (rt:interface).

   By using the "when" statement, the augmented configuration parameters
   and state data specific to the new protocol SHOULD be made
   conditional and valid only if the value of "rt:type" or "rt:source-
   protocol" is equal to the new protocol's identity.  It is also
   RECOMMENDED that the protocol-
   specific protocol-specific data be encapsulated in
   appropriately named containers.

   The above steps are implemented by the example YANG module for the
   RIP routing protocol in Appendix B.

4.5.  Route Filters

   The core routing data model provides a skeleton for defining route
   filters that can be used to restrict the set of routes being
   exchanged between a routing protocol instance and a connected routing
   table, or between a source and a recipient routing table.  Route
   filters may also manipulate routes, i.e., add, delete, or modify
   their attributes.

   Route filters are global, which means that a configured route filter
   may be used by any or all router instances.  However, an
   implementation MAY specify rules and restrictions for sharing route
   filters among router instances.

   By itself, the route filtering framework defined in this document
   allows for applying only two extreme routing policies which are
   represented by the following pre-defined route filter types:

   o  "deny-all-route-filter": all routes are blocked,

   o  "allow-all-route-filter": all routes are permitted.

   Note that the

   The latter type is equivalent to no route filter.

   It is expected that more comprehensive route filtering frameworks
   will be developed separately.

   Each route filter is identified by a name which MUST be unique within
   the entire configuration. name.  Its type MUST be
   specified by the "type" identity reference - this opens the space for
   multiple route filtering framework implementations.

4.6.  RPC Operations

   The "ietf-routing" module defines two RPC operations:

   o  active-route: query the routing system for the active route(s)
      that are currently used for sending datagrams to a destination
      host whose address is passed as an input parameter.

   o  route-count: retrieve the total number of entries in a routing
      table.

5.  Interactions with Other YANG Modules

   The semantics of the core routing data model also depend on several
   configuration parameters that are defined in other YANG modules.

5.1.  Module "ietf-interfaces"

   The following boolean switch is defined in the "ietf-interfaces" YANG
   module [YANG-IF]:

   /if:interfaces/if:interface/if:enabled

      If this switch is set to "false" for a given network layer
      interface, the device MUST behave exactly as if that interface was
      not assigned to any logical router at all.

5.2.  Module "ietf-ip"

   The following boolean switches are defined in the "ietf-ip" YANG
   module [YANG-IP]:

   /if:interfaces/if:interface/ip:ipv4/ip:enabled

      If this switch is set to "false" for a given interface, then all
      IPv4 routing functions related to that interface MUST be disabled.

   /if:interfaces/if:interface/ip:ipv4/ip:forwarding

      If this switch is set to "false" for a given interface, then the
      forwarding of IPv4 datagrams to and from this interface MUST be
      disabled.  However, the interface may participate in other routing
      functions, such as routing protocols.

   /if:interfaces/if:interface/ip:ipv6/ip:enabled

      If this switch is set to "false" for a given interface, then all
      IPv6 routing functions related to that interface MUST be disabled.

   /if:interfaces/if:interface/ip:ipv6/ip:forwarding

      If this switch is set to "false" for a given interface, then the
      forwarding of IPv6 datagrams to and from this interface MUST be
      disabled.  However, the interface may participate in other routing
      functions, such as routing protocols.

   In addition, the "ietf-ip" module allows for configuring IPv4 and
   IPv6 addresses and network prefixes or masks on network layer
   interfaces.  Configuration of these parameters on an enabled
   interface MUST result in an immediate creation of the corresponding
   direct route.  The destination prefix of this route is set according
   to the configured IP address and network prefix/mask, and the
   interface is set as the outgoing interface for that route.

6.  Routing YANG Module

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number and all occurrences of the revision date below with
   the date of RFC publication (and remove this note).

   <CODE BEGINS> file "ietf-routing@2013-02-23.yang" "ietf-routing@2013-07-13.yang"

   module ietf-routing {

     namespace "urn:ietf:params:xml:ns:yang:ietf-routing";

     prefix "rt";

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

     import ietf-interfaces {
       prefix "if";
     }

     import iana-afn-safi {
       prefix "ianaaf";
     }

     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

     contact
       "WG Web: <http://tools.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        WG Chair: David Kessens
        <mailto:david.kessens@nsn.com>

        WG Chair: Juergen Schoenwaelder
        <mailto:j.schoenwaelder@jacobs-university.de>

        Editor: Ladislav Lhotka
        <mailto:lhotka@nic.cz>
       ";

     description
       "This YANG module defines essential components that may be used for configuring the management
        of a routing subsystem.

        Copyright (c) 2012 2013 IETF Trust and the persons identified as
        authors of the code. All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices.
       ";

     revision 2013-02-23 2013-07-13 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Management";
     }

     /* Features */

     feature user-defined-routing-tables {
       description
         "Indicates that the device supports additional routing tables
          defined by the user.

          Devices that do not support this feature MUST provide exactly
          one routing table per supported address family. These routing
          tables then appear as entries of the list
          /routing-state/routing-tables/routing-table.
         ";
     }

     /* Identities */

     identity router-type {
       description
         "Base identity from which router type identities are derived.

          It is primarily intended for discriminating among different
          types of logical routers or router virtualization.
         ";
     }

     identity standard-router {
       base router-type;
       description
         "This identity represents a standard router.";
     }

     identity routing-protocol {
       description
         "Base identity from which routing protocol identities are
          derived.";
     }

     identity direct {
       base routing-protocol;
       description
         "Routing pseudo-protocol which provides routes to directly
          connected networks.";
     }

     identity static {
       base routing-protocol;
       description
         "Static routing pseudo-protocol.";
     }

     identity route-filter {
       description
         "Base identity from which all route filters are derived.";
     }

     identity deny-all-route-filter {
       base route-filter;
       description
         "Route filter that blocks all routes.";
     }

     identity allow-all-route-filter {
       base route-filter;
       description
         "Route filter that permits all routes.";
     }

     /* Type Definitions */

     typedef router-ref {
       type leafref {
         path "/rt:routing/rt:router/rt:name";
       }
       description
         "This type is used for leafs that reference a router instance
          configuration.";

     }

     typedef router-state-ref {
       type leafref {
         path "/rt:routing-state/rt:router/rt:name";
       }
       description
         "This type is used for leafs that reference state data of a
          router instance.";
     }

     typedef routing-table-ref {
       type leafref {
         path "/rt:routing/rt:routing-tables/rt:routing-table/rt:name";
       }
       description
         "This type is used for leafs that reference a routing table."; table
          configuration.";
     }

     typedef routing-table-state-ref {
       type leafref {
         path "/rt:routing-state/rt:routing-tables/rt:routing-table/"
            + "rt:name";
       }
       description
         "This type is used for leafs that reference a routing table in
          state data.";
     }

     typedef route-filter-ref {
       type leafref {
         path "/rt:routing/rt:route-filters/rt:route-filter/rt:name";
       }
       description
         "This type is used for leafs that reference a route filter."; filter
          configuration.";
     }

     typedef route-filter-state-ref {
       type leafref {
         path "/rt:routing-state/rt:route-filters/rt:route-filter/"
            + "rt:name";
       }
       description
         "This type is used for leafs that reference a route filter in
          state data.";
     }
     /* Groupings */

     grouping afn-safi {
       description
         "This grouping provides two parameters specifying address
          family and subsequent address family.";
       leaf address-family {
         type ianaaf:address-family;
         mandatory "true";
         description
           "Address family.";
       }
       leaf safi {
         type ianaaf:subsequent-address-family;
         mandatory "true";
         description
           "Subsequent address family.";
       }
     }

     grouping router-id {
       description
         "This grouping provides the definition of router ID.";
       leaf router-id {
         type yang:dotted-quad;
         description
           "Router ID - 32-bit number in the form of a dotted quad.";
       }
     }

     grouping route-content {
       description
         "Generic parameters of routes."; static routes (configuration).";
       leaf outgoing-interface {
         type if:interface-ref;
         description
           "Outgoing interface.";
       }
     }

     /* RPC Methods */

     rpc active-route

     grouping route-state-content {
       description
         "Return the active route (or multiple routes, in the case
         "Generic parameters of routes in state data.";
       leaf outgoing-interface {
         type if:interface-state-ref;
         description
           "Outgoing interface.";
       }

     }

     /* RPC Methods */

     rpc active-route {
       description
         "Return the active route (or multiple routes, in the case of
          multi-path routing) to a destination address.

          Parameters

          1. 'router-name',

          2. 'destination-address'.

          If the router instance with 'router-name' doesn't exist, then
          this operation SHALL fail with error-tag 'data-missing' and
          error-app-tag 'router-not-found'.

          If no active route for 'destination-address' exists, no output
          is returned - the server SHALL send an <rpc-reply> containing
          a single element <ok>.
         ";
       input {
         leaf router-name {
           type router-ref; router-state-ref;
           mandatory "true";
           description
             "Name of the router instance whose forwarding information
              base is being queried.";
         }
         container destination-address {
           description
             "Network layer destination address.

              Address family specific modules MUST augment this
              container with a leaf named 'address'.
             ";
           uses afn-safi;
         }
       }
       output {
         list route {
           description
             "List of active routes.

              Route contents specific for each address family is
              expected be defined through augmenting.

             ";
           uses afn-safi;
           uses route-content;
         }
       }
     }

     rpc route-count {
       description
         "Return the current number of routes in a routing table.

          Parameters:

          1. 'routing-table-name'.

          If the routing table with the name specified in
          'routing-table-name' doesn't exist, then this operation SHALL
          fail with error-tag 'data-missing' and error-app-tag
          'routing-table-not-found'.
         ";
       input {
         leaf routing-table {
           type routing-table-ref; routing-table-state-ref;
           mandatory "true";
           description
             "Name of the routing table.";
         }
       }
       output {
         leaf number-of-routes {
           type uint32;
           mandatory "true";
           description
             "Number of routes in the routing table.";
         }
       }
     }

     /* Data Nodes Operational state data */

     container routing routing-state {
       config "false";
       description
         "Routing parameters.";
         "Operational state of the routing subsystem.";
       list router {
         key "name";
         description
           "Each list entry is a container for configuration and operational state data of
            a single (logical) router instance.

            An implementation MAY create one or more instances on its
            own, other instances MAY be created by configuration.
           ";
         leaf name {
           type string;
           description
             "An arbitrary
             "The name of the router instance.";
         }
         leaf type {
           type identityref {
             base router-type;
           }
           default "rt:standard-router";
           description
             "This leaf specifies the
             "The router type.

              It is type, primarily intended as a means for discriminating
              among different types of logical routers, route
              virtualization, master-slave arrangements etc., while
              keeping all such router instances in the same flat list.
             ";
         }
         leaf enabled {
           type boolean;
           default "true";
           description
             "Enable/disable the router instance.

              If this parameter is false, the parent router instance is
              disabled, despite any other configuration that might be
              present.
             ";
         }
         leaf
         uses router-id {
           type yang:dotted-quad;
           description
             "Global router ID - 32-bit number in the form of a dotted
              quad. ID.

              An implementation MAY select may choose a value if this parameter none is
              not
              configured.

              Routing protocols MAY override this global parameter
              inside their configuration. parameter.
             ";
         }
         leaf description {
           type string;
           description
             "Textual description of the router.";
         }
         container main-routing-tables default-routing-tables {
           description
             "Main
             "Default routing tables used by the router instance.";
           list main-routing-table {
             must "address-family=/routing/routing-tables/"
                + "routing-table[name=current()/name]/"
                + "address-family and safi=/routing/routing-tables/"
                + "routing-table[name=current()/name]/safi" default-routing-table {
               error-message "Address family mismatch.";
               description
                 "The entry's address family MUST match that of the
                  referenced routing table.";
             }
             key "address-family safi";
             description
               "Each list entry specifies the main default routing table for
                one address family.

                The main default routing table is operationally connected to
                all routing protocols for which a connected routing
                table has not been explicitly configured.

                The 'direct' pseudo-protocol is always connected to the
                main
                default routing table.

                Address families that don't have their entry in this
                list MUST NOT be used in the rest of the router instance
                configuration. tables.
               ";

             uses afn-safi;
             leaf name {
               type routing-table-ref; routing-table-state-ref;
               mandatory "true";
               description
                 "Name of an existing routing table to be used as the
                  main
                  default routing table for the given router instance
                  and address family.";
             }
           }
         }
         container interfaces {
           description
             "Router interface parameters."; interfaces.";
           list interface {
             key "name";
             description
               "List of network layer interfaces assigned to the router
                instance.";
             leaf name {
               type if:interface-ref; if:interface-state-ref;
               description
                 "A reference to the name of a configured network layer
                  interface.";
             }
           }
         }
         container routing-protocols {
           description
             "Container for the list of configured routing protocol instances.";
           list routing-protocol {
             key "name";
             description
               "An instance
               "Operational state of a routing protocol."; protocol instance.
               ";
             leaf name {
               type string;
               description
                 "An arbitrary
                 "The name of the routing protocol instance.";
             }
             leaf description type {
               type string;
               description
                 "Textual identityref {
                 base routing-protocol;
               }
               mandatory "true";
               description
                 "Type of the routing protocol
                  instance."; protocol.";
             }
             leaf enabled
             container connected-routing-tables {
               type boolean;
               default "true";
               if-feature user-defined-routing-tables;
               description
                 "Enable/disable the routing protocol instance.

                  If this parameter is false, the parent routing
                  protocol instance is disabled, despite any other
                  configuration that might be present.
                 ";
             }
             leaf type {
               type identityref {
                 base routing-protocol;
               }
               mandatory "true";
               description
                 "Type of the routing protocol - an identity derived
                  from the 'routing-protocol' base identity.";
             }
             container connected-routing-tables {
               description
                 "Container for connected
                 "Container for connected routing tables.
                 ";
               list connected-routing-table {
                 must "not(/routing/routing-tables/"
                    + "routing-table[name=current()/"
                    + "preceding-sibling::connected-routing-table/"
                    + "name and address-family=/routing/routing-tables/"
                    + "routing-table[name=current()/name]/"
                    + "address-family and safi=/routing/routing-tables/"
                    + "routing-table[name=current()/name]/safi])" {
                   error-message "Duplicate address family for "
                               + "connected routing tables.";
                   description
                     "For each AFN/SAFI pair there MUST NOT be more than
                      one connected routing table.";

                 }
                 key "name";
                 description
                   "List of routing tables to which the routing protocol
                    instance is connected (at most one routing table per
                    address family).

                    If no connected routing table is configured for an
                    address family, the routing protocol MUST be
                    operationally connected to the main routing table
                    for that address family.
                   ";
                 leaf name {
                   type routing-table-ref;
                   must "../../../type != 'rt:direct' or "
                      + "../../../../../main-routing-tables/ "
                      + "main-routing-table/name=." {
                     error-message "The 'direct' protocol can be "
                                 + "connected only to a main routing "
                                 + "table.";
                     description
                       "For the 'direct' pseudo-protocol, the connected
                        routing table must always be a main routing
                        table.";
                   } routing-table-state-ref;
                   description
                     "Name of an existing routing table.";
                 }
                 leaf import-filter {
                   type route-filter-ref; route-filter-state-ref;
                   description
                     "Reference to a route filter that is used for
                      filtering routes passed from this routing protocol
                      instance to the routing table specified by the
                      'name' sibling node.

                      If this leaf is not present, the behavior is
                      protocol-specific, but typically it means that all
                      routes are accepted.
                     ";
                 }
                 leaf export-filter {
                   type route-filter-ref; route-filter-state-ref;
                   description
                     "Reference to a route filter that is used for
                      filtering routes passed from the routing table
                      specified by the 'name' sibling node to this
                      routing protocol instance.

                      If this leaf is not present, the behavior is
                      protocol-specific - typically it means that all
                      routes are accepted.

                      The 'direct' and 'static' pseudo-protocols accept
                      no routes from any routing table.
                     ";
                 }
               }
             }
             container static-routes {
               when "../type='rt:static'" {
                 description
                   "This container is only valid for the 'static'
                    routing protocol.";
               }
               description
                 "Configuration of 'static' pseudo-protocol.

                  Address family specific modules augment this node with
                  their lists of routes.
                 ";
             }

           }
         }
       }
       container routing-tables {
         description
           "Container for configured routing tables.";
         list routing-table {
           key "name";
           description
             "Each entry represents a routing table identified by the
              'name' key. All routes in a routing table MUST belong to
              the same address family."; family.

              The server MUST create the default routing table for each
              address family, and MAY create other routing tables.
              Additional routing tables MAY be created in the
              configuration.
             ";
           leaf name {
             type string;
             description
               "An arbitrary
               "The name of the routing table.";
           }
           uses afn-safi;
           leaf description
           container routes {
             type string;
             description
               "Textual
             description
               "Current contents of the routing table.";
           }
           container routes {
             config "false";
             description
               "Current contents of the routing table (state data).";
             list route {
               description
                 "A routing table entry. This data node MUST be
                  augmented with information specific for routes of each
                  address family.";
               uses route-content; route-state-content;
               leaf source-protocol {
                 type string; identityref {
                   base routing-protocol;
                 }
                 mandatory "true";
                 description
                   'Routing
                   "Type of the routing protocol instance from which the route
                    originated.

                    It must be either "direct" or the name of a
                    configured routing protocol instance.
                   ';
                    originated.";
               }
               leaf last-updated {
                 type yang:date-and-time;
                 description
                   "Time stamp of the last modification of the route. If
                    the route was never modified, it is the time when
                    the route was inserted into the routing table.";

               }
             }
           }
           container recipient-routing-tables {
             if-feature user-defined-routing-tables;
             description
               "Container for recipient routing tables.";
             list recipient-routing-table {
               must "name != ../../name" {
                 error-message "Source and recipient routing tables "
                             + "are identical.";
                 description
                   "A routing table MUST NOT appear among its recipient
                    routing tables.";
               }
               must "/routing/routing-tables/"
                  + "routing-table[name=current()/name]/"
                  + "address-family=../../address-family and /routing/"
                  + "routing-tables/routing-table[name=current()/name]/"
                  + "safi=../../safi" {
                 error-message "Address family mismatch.";
                 description
                   "Address family of the recipient routing table MUST
                    match the source table.";

               }
               key "name";
               description
                 "List of routing tables that receive routes from this
                  routing table.";
               leaf name {
                 type routing-table-ref; routing-table-state-ref;
                 description
                   "The name of the recipient routing table.";
               }
               leaf filter {
                 type route-filter-ref; route-filter-state-ref;
                 description
                   "A route filter which is applied to the routes passed
                    to the recipient routing table.";
               }
             }
           }
         }
       }
       container route-filters {
         description
           "Container for configured route filters.";
         list route-filter {
           key "name";
           description
             "Route filters are used for filtering and/or manipulating
              routes that are passed between a routing protocol and a
              routing table and vice versa, or between two routing
              tables.

              It is expected that other modules augment this list with
              contents specific for a particular route filter type.
             ";
           leaf name {
             type string;
             description
               "An arbitrary
               "The name of the route filter.";
           }
           leaf description {
             type string;
             description
               "Textual description of the route filter.";
           }
           leaf type {
             type identityref {
               base route-filter;
             }
             mandatory "true";
             description
               "Type of the route-filter - an identity derived from the
                'route-filter' base identity.";
           }
         }
       }
     }
   }

   <CODE ENDS>

7.  IPv4 Unicast Routing YANG Module

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with

     /* Configuration Data */

     container routing {
       description
         "Configuration parameters for the
   actual RFC number and all occurrences routing subsystem.";
       list router {
         key "name";
         description
           "Configuration of a router instance.
           ";
         leaf name {
           type string;
           description
             "The name of the revision date below with router instance.

              The names for system-created router instances are assigned
              by the date of RFC publication (and remove this note).

   <CODE BEGINS> file "ietf-ipv4-unicast-routing@2013-02-23.yang"

   module ietf-ipv4-unicast-routing system. The same name then has to be used in the
              configuration.

              An arbitrary name may be chosen if the router instance is
              created in the configuration.
             ";
         }
         leaf type {

     namespace "urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing";

     prefix "v4ur";

     import ietf-routing
           type identityref {
       prefix "rt";
             base router-type;
           }

     import ietf-inet-types {
       prefix "inet";
           default "rt:standard-router";
           description
             "The router type.";
         }

     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

     contact
       "WG Web: <http://tools.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        WG Chair: David Kessens
        <mailto:david.kessens@nsn.com>

        WG Chair: Juergen Schoenwaelder
        <mailto:j.schoenwaelder@jacobs-university.de>

        Editor: Ladislav Lhotka
        <mailto:lhotka@nic.cz>
       ";
         leaf enabled {
           type boolean;
           default "true";
           description
       "This YANG module augments the 'ietf-routing' module with basic
        configuration and state data for IPv4 unicast routing.

        Copyright (c) 2012 IETF Trust and
             "Enable/disable the persons identified as
        authors of router instance.

              If this parameter is false, the code. All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, parent router instance is permitted pursuant to,
              disabled and subject to
        the license terms contained in, the Simplified BSD License set
        forth does not appear in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices. operational state data,
              despite any other configuration that might be present.
             ";

     revision 2013-02-23 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Management";
         }

     /* Groupings */

     grouping route-content
         uses router-id {
           description
         "Parameters
             "Configuration of IPv4 unicast routes.";
       leaf dest-prefix {
         type inet:ipv4-prefix;
         description
           "IPv4 destination prefix."; the global router ID.";
         }
         leaf next-hop description {
           type inet:ipv4-address; string;
           description
             "Textual description
           "IPv4 address of the next hop.";
       } router instance.";
         }

     /* RPC Methods */

     augment "/rt:active-route/rt:input/rt:destination-address" {
       when "rt:address-family='ipv4' and rt:safi='nlri-unicast'"
         container default-routing-tables {
           if-feature user-defined-routing-tables;
           description
           "This augment is valid only for IPv4 unicast.";
       }
       description
         "The 'address' leaf augments the 'rt:destination-address'
          parameter
             "Configuration of the 'rt:active-route' operation.";
       leaf address {
         type inet:ipv4-address;
         description
           "IPv4 destination address.";
       }

     }

     augment "/rt:active-route/rt:output/rt:route" {
       when "rt:address-family='ipv4' and rt:safi='nlri-unicast'" {
         description
           "This augment is valid only default routing tables used by the
              router instance.

              The default routing table for IPv4 unicast.";
       } an addressed family if by
              default connected to all routing protocol instances
              supporting that address family, and always receives direct
              routes.
             ";
           list default-routing-table {
             must "address-family=/routing/routing-tables/"
                + "routing-table[name=current()/name]/"
                + "address-family and safi=/routing/routing-tables/"
                + "routing-table[name=current()/name]/safi" {
               error-message "Address family mismatch.";
               description
         "Contents
                 "The entry's address family MUST match that of the reply to 'rt:active-route' operation.";
       uses route-content;
                  referenced routing table.";
             }

     /* Data nodes */

     augment "/rt:routing/rt:router/rt:routing-protocols/"
           + "rt:routing-protocol/rt:static-routes" {
             key "address-family safi";
             description
         "This augment defines
               "Each list entry configures the configuration default routing table for
                one address family.";
             uses afn-safi;
             leaf name {
               type string;
               mandatory "true";
               description
                 "Name of an existing routing table to be used as the 'static'
          pseudo-protocol with data specific
                  default routing table for IPv4 unicast."; the given router instance
                  and address family.";
             }

           }
         }
         container ipv4 interfaces {
           description
             "Configuration of a 'static' pseudo-protocol instance
            consists router interface parameters.";
           list interface {
             key "name";
             description
               "List of network layer interfaces assigned to the router
                instance.";
             leaf name {
               type if:interface-ref;
               description
                 "A reference to the name of a list configured network layer
                  interface.";
             }
           }
         }
         container routing-protocols {
           description
             "Configuration of routes."; routing protocol instances.";
           list route routing-protocol {
             key "id";
           ordered-by "user"; "name";
             description
             "A user-ordered list
               "Each entry contains configuration of static routes."; a routing protocol
                instance.";
             leaf id name {
               type uint32 {
               range "1..max";
             } string;
               description
               "Numeric identifier
                 "An arbitrary name of the route.

                It is not required that the routes be sorted by their
                'id'.
               "; routing protocol instance.";
             }
             leaf description {
               type string;
               description
                 "Textual description of the route."; routing protocol
                  instance.";
             }
           uses rt:route-content;
           uses route-content {
             refine "dest-prefix"
             leaf enabled {
               mandatory "true";

             }
           }
               type boolean;
               default "true";
               description
                 "Enable/disable the routing protocol instance.

                  If this parameter is false, the parent routing
                  protocol instance is disabled and does not appear in
                  operational state data, despite any other
                  configuration that might be present.
                 ";

             }
             leaf type {
               type identityref {
                 base routing-protocol;
               }
               mandatory "true";
               description
                 "Type of the routing protocol - an identity derived
                  from the 'routing-protocol' base identity.";
             }

     augment "/rt:routing/rt:routing-tables/rt:routing-table/rt:routes/"
           + "rt:route"
             container connected-routing-tables {
       when "../../rt:address-family = 'ipv4'
               if-feature user-defined-routing-tables;
               description
                 "Configuration of connected routing tables.
                 ";
               list connected-routing-table {
                 must "not(/routing/routing-tables/"
                    + "routing-table[name=current()/"
                    + "preceding-sibling::connected-routing-table/"
                    + "name and ../../rt:safi = " address-family=/routing/routing-tables/"
                    + "'nlri-unicast'" "routing-table[name=current()/name]/"
                    + "address-family and safi=/routing/routing-tables/"
                    + "routing-table[name=current()/name]/safi])" {
         description
           "This augment is valid only
                   error-message "Duplicate address family for IPv4 unicast.";
       } "
                               + "connected routing tables.";
                   description
         "This augment defines the content of IPv4 unicast routes.";
       uses route-content;
     }
                     "For each AFN/SAFI pair there MUST NOT be more than
                      one connected routing table.";
                 }

   <CODE ENDS>

8.  IPv6 Unicast Routing YANG Module

   RFC Ed.: In this section, replace all occurrences
                 key "name";
                 description
                   "List of 'XXXX' with routing tables to which the
   actual RFC number and all occurrences of routing protocol
                    instance is connected (at most one routing table per
                    address family).

                    If no connected routing table is configured for an
                    address family, the revision date below with routing protocol is connected to
                    the date of RFC publication (and remove this note).

   <CODE BEGINS> file "ietf-ipv6-unicast-routing@2013-02-23.yang"

   module ietf-ipv6-unicast-routing default routing table for that address family.
                   ";
                 leaf name {

     namespace "urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing";

     prefix "v6ur";

     import ietf-routing
                   type routing-table-ref;
                   must "../../../type != 'rt:direct' or "
                      + "../../../../../default-routing-tables/ "
                      + "default-routing-table/name=." {
       prefix "rt";
     }

     import
                     error-message "The 'direct' protocol can be "
                                 + "connected only to a default "
                                 + "routing table.";
                     description
                       "For the 'direct' pseudo-protocol, the connected
                        routing table must always be a default routing
                        table.";
                   }
                   description
                     "Name of an existing routing table.";
                 }
                 leaf import-filter {
                   type route-filter-ref;
                   description
                     "Configuration of import filter.";
                 }
                 leaf export-filter {
                   type route-filter-ref;
                   description
                     "Configuration of export filter.";
                 }
               }
             }
             container static-routes {
               when "../type='rt:static'" {
                 description
                   "This container is only valid for the 'static'
                    routing protocol.";
               }
               description
                 "Configuration of the 'static' pseudo-protocol.

                  Address family specific modules augment this node with
                  their lists of routes.
                 ";
             }
           }
         }
       }
       container routing-tables {
         description
           "Configured routing tables.";
         list routing-table {
           key "name";
           description
             "Each entry represents a configured routing table
              identified by the 'name' key.

              Entries having the same key as a system-provided entry of
              the list /routing-state/routing-tables/routing-tables are
              used for configuring parameters of that entry. Other
              entries define additional user-provided routing tables.

             ";
           leaf name {
             type string;
             description
               "The name of the routing table.";
           }
           uses afn-safi;
           leaf description {
             type string;
             description
               "Textual description of the routing table.";
           }
           container recipient-routing-tables {
             if-feature user-defined-routing-tables;
             description
               "Configuration of recipient routing tables.";
             list recipient-routing-table {
               must "name != ../../name" {
                 error-message "Source and recipient routing tables "
                             + "are identical.";
                 description
                   "A routing table MUST NOT appear among its recipient
                    routing tables.";
               }
               must "/routing/routing-tables/"
                  + "routing-table[name=current()/name]/"
                  + "address-family=../../address-family and /routing/"
                  + "routing-tables/routing-table[name=current()/name]/"
                  + "safi=../../safi" {
                 error-message "Address family mismatch.";
                 description
                   "Address family of the recipient routing table MUST
                    match the source table.";
               }
               key "name";
               description
                 "Each entry configures a recipient routing table.";
               leaf name {
                 type routing-table-ref;
                 description
                   "The name of the recipient routing table.";
               }
               leaf filter {
                 type route-filter-ref;
                 description
                   "A route filter which is applied to the routes passed
                    to the recipient routing table.";
               }

             }
           }
         }
       }
       container route-filters {
         description
           "Configuration of route filters.";
         list route-filter {
           key "name";
           description
             "Each entry configures a named route filter.";
           leaf name {
             type string;
             description
               "The name of the route filter.";
           }
           leaf description {
             type string;
             description
               "Textual description of the route filter.";
           }
           leaf type {
             type identityref {
               base route-filter;
             }
             mandatory "true";
             description
               "Type of the route filter..";
           }
         }
       }
     }
   }

   <CODE ENDS>

7.  IPv4 Unicast Routing YANG Module

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number and all occurrences of the revision date below with
   the date of RFC publication (and remove this note).

   <CODE BEGINS> file "ietf-ipv4-unicast-routing@2013-07-13.yang"

   module ietf-ipv4-unicast-routing {

     namespace "urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing";

     prefix "v4ur";

     import ietf-routing {
       prefix "rt";
     }

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

     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

     contact
       "WG Web: <http://tools.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        WG Chair: David Kessens
        <mailto:david.kessens@nsn.com>

        WG Chair: Juergen Schoenwaelder
        <mailto:j.schoenwaelder@jacobs-university.de>

        Editor: Ladislav Lhotka
        <mailto:lhotka@nic.cz>
       ";

     description
       "This YANG module augments the 'ietf-routing' module with basic
        configuration and operational state data for IPv4 unicast
        routing.

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

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices.
       ";

     revision 2013-07-13 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Management";
     }

     /* Groupings */

     grouping route-content {
       description
         "Parameters of IPv4 unicast routes.";
       leaf dest-prefix {
         type inet:ipv4-prefix;
         description
           "IPv4 destination prefix.";
       }
       leaf next-hop {
         type inet:ipv4-address;
         description
           "IPv4 address of the next hop.";
       }
     }

     /* RPC Methods */

     augment "/rt:active-route/rt:input/rt:destination-address" {
       when "rt:address-family='ipv4' and rt:safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv4 unicast.";
       }
       description
         "The 'address' leaf augments the 'rt:destination-address'
          parameter of the 'rt:active-route' operation.";
       leaf address {
         type inet:ipv4-address;
         description
           "IPv4 destination address.";

       }
     }

     augment "/rt:active-route/rt:output/rt:route" {
       when "rt:address-family='ipv4' and rt:safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv4 unicast.";
       }
       description
         "Contents of the reply to 'rt:active-route' operation.";
       uses route-content;
     }

     /* Operational state */

     augment "/rt:routing-state/rt:routing-tables/rt:routing-table/"
           + "rt:routes/rt:route" {
       when "../../rt:address-family = 'ipv4' and ../../rt:safi = "
          + "'nlri-unicast'" {
         description
           "This augment is valid only for IPv4 unicast.";
       }
       description
         "This augment defines the content of IPv4 unicast routes.";
       uses route-content;
     }

     /* Configuration */

     augment "/rt:routing/rt:router/rt:routing-protocols/"
           + "rt:routing-protocol/rt:static-routes" {
       description
         "This augment defines the configuration of the 'static'
          pseudo-protocol with data specific for IPv4 unicast.";
       container ipv4 {
         description
           "Configuration of a 'static' pseudo-protocol instance
            consists of a list of routes.";
         list route {
           key "id";
           ordered-by "user";
           description
             "A user-ordered list of static routes.";
           leaf id {
             type uint32 {
               range "1..max";
             }
             description
               "Numeric identifier of the route.

                It is not required that the routes be sorted by their
                'id'.
               ";
           }
           leaf description {
             type string;
             description
               "Textual description of the route.";
           }
           uses rt:route-content;
           uses route-content {
             refine "dest-prefix" {
               mandatory "true";
             }
           }
         }
       }
     }
   }

   <CODE ENDS>

8.  IPv6 Unicast Routing YANG Module

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number and all occurrences of the revision date below with
   the date of RFC publication (and remove this note).

   <CODE BEGINS> file "ietf-ipv6-unicast-routing@2013-07-13.yang"

   module ietf-ipv6-unicast-routing {

     namespace "urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing";

     prefix "v6ur";

     import ietf-routing {
       prefix "rt";
     }

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

     import ietf-interfaces {
       prefix "if";
     }

     import ietf-ip {
       prefix "ip";
     }

     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

     contact
       "WG Web: <http://tools.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        WG Chair: David Kessens
        <mailto:david.kessens@nsn.com>

        WG Chair: Juergen Schoenwaelder
        <mailto:j.schoenwaelder@jacobs-university.de>

        Editor: Ladislav Lhotka
        <mailto:lhotka@nic.cz>
       ";

     description
       "This YANG module augments the 'ietf-routing' module with basic
        configuration and operational state data for IPv6 unicast
        routing.

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

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices.
       ";

     revision 2013-07-13 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Management";
     }

     /* Groupings */

     grouping route-content {
       description
         "Specific parameters of IPv6 unicast routes.";
       leaf dest-prefix {
         type inet:ipv6-prefix;
         description
           "IPv6 destination prefix.";
       }
       leaf next-hop {
         type inet:ipv6-address;
         description
           "IPv6 address of the next hop.";
       }
     }

     /* RPC Methods */

     augment "/rt:active-route/rt:input/rt:destination-address" {
       when "rt:address-family='ipv6' and rt:safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv6 unicast.";

       }
       description
         "The 'address' leaf augments the 'rt:destination-address'
          parameter of the 'rt:active-route' operation.";
       leaf address {
         type inet:ipv6-address;
         description
           "IPv6 destination address.";
       }
     }

     augment "/rt:active-route/rt:output/rt:route" {
       when "rt:address-family='ipv6' and rt:safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv6 unicast.";
       }
       description
         "Contents of the reply to 'rt:active-route' operation.";
       uses route-content;
     }

     /* Operational state data */

     augment "/rt:routing-state/rt:router/rt:interfaces/rt:interface" {
       when "/if:interfaces/if:interface[if:name=current()/rt:name]/"
          + "ip:ipv6/ip:enabled='true'" {
         description
           "This augment is only valid for router interfaces with
            enabled IPv6.";
       }
       description
         "IPv6-specific parameters of router interfaces.";
       container ipv6-router-advertisements {
         description
           "Parameters of IPv6 Router Advertisements.";
         leaf send-advertisements {
           type boolean;
           default "false";
           description
             "A flag indicating whether or not the router sends periodic
              Router Advertisements and responds to Router
              Solicitations.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvSendAdvertisements.";
         }
         leaf max-rtr-adv-interval {
           type uint16 {
             range "4..1800";
           }
           units "seconds";
           default "600";
           description
             "The maximum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MaxRtrAdvInterval.";
         }
         leaf min-rtr-adv-interval {
           type uint16 {
             range "3..1350";
           }
           units "seconds";
           description
             "The minimum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.

              The default value to be used operationally if this leaf is
              not configured is determined as follows:

              - if max-rtr-adv-interval >= 9 seconds, the default value
                is 0.33 * max-rtr-adv-interval;

              - otherwise it is 0.75 * max-rtr-adv-interval.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MinRtrAdvInterval.";
         }
         leaf managed-flag {
           type boolean;
           default "false";
           description
             "The boolean value to be placed in the 'Managed address
              configuration' flag field in the Router Advertisement.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvManagedFlag.";
         }
         leaf other-config-flag {
           type boolean;
           default "false";
           description
             "The boolean value to be placed in the 'Other
              configuration' flag field in the Router Advertisement.";

           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvOtherConfigFlag.";
         }
         leaf link-mtu {
           type uint32;
           default "0";
           description
             "The value to be placed in MTU options sent by the router.
              A value of zero indicates that no MTU options are sent.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvLinkMTU.";
         }
         leaf reachable-time {
           type uint32 {
             range "0..3600000";
           }
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Reachable Time field in the
              Router Advertisement messages sent by the router. The
              value zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvReachableTime.";
         }
         leaf retrans-timer {
           type uint32;
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Retrans Timer field in the
              Router Advertisement messages sent by the router. The
              value zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvRetransTimer.";
         }
         leaf cur-hop-limit {
           type uint8;
           default "64";
           description
             "The default value to be placed in the Cur Hop Limit field
              in the Router Advertisement messages sent by the router.
              The value should be set to the current diameter of the
              Internet. The value zero means unspecified (by this
              router).

              The default SHOULD be set to the value specified in IANA
              Assigned Numbers that was in effect at the time of
              implementation.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvCurHopLimit.

              IANA: IP Parameters,
              http://www.iana.org/assignments/ip-parameters
             ";
         }

     import ietf-interfaces
         leaf default-lifetime {
       prefix "if";
     }

     import ietf-ip
           type uint16 {
       prefix "ip";
             range "0..9000";
           }

     organization
       "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

     contact
       "WG Web: <http://tools.ietf.org/wg/netmod/>
        WG List: <mailto:netmod@ietf.org>

        WG Chair: David Kessens
        <mailto:david.kessens@nsn.com>

        WG Chair: Juergen Schoenwaelder
        <mailto:j.schoenwaelder@jacobs-university.de>

        Editor: Ladislav Lhotka
        <mailto:lhotka@nic.cz>
       ";
           units "seconds";
           description
       "This YANG module augments the 'ietf-routing' module with basic
        configuration and state data for IPv6 unicast routing.

        Copyright (c) 2012 IETF Trust and
             "The value to be placed in the persons identified as
        authors Router Lifetime field of
              Router Advertisements sent from the code. All rights reserved.

        Redistribution and use interface, in source and binary forms, with seconds.
              MUST be either zero or
        without modification, is permitted pursuant to, between max-rtr-adv-interval and subject
              9000 seconds. A value of zero indicates that the router is
              not to be used as a default router. These limits may be
              overridden by specific documents that describe how IPv6
              operates over different link layers.

              If this parameter is not configured, a value of 3 *
              max-rtr-adv-interval SHOULD be used.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvDefaultLifeTime.";
         }
         container prefix-list {
           description
             "A list of prefixes that are placed in Prefix Information
              options in Router Advertisement messages sent from the license terms contained in,
              interface.

              By default, these are all prefixes that the Simplified BSD License set
        forth router
              advertises via routing protocols as being on-link for the
              interface from which the advertisement is sent.

              The link-local prefix SHOULD NOT be included in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part list
              of RFC XXXX; see the
        RFC itself for full legal notices. advertised prefixes.
             ";

     revision 2013-02-23 {
       description
         "Initial revision.";

           reference
             "RFC XXXX: A YANG Data Model 4861: Neighbor Discovery for Routing Management";
     }

     /* Groupings */

     grouping route-content IP version 6 (IPv6) -
              AdvPrefixList.";
           list prefix {
             key "prefix-spec";
             description
         "Specific parameters of IPv6 unicast routes.";
               "Advertised prefix entry with parameters.";
             leaf dest-prefix prefix-spec {
               type inet:ipv6-prefix;
               description
                 "IPv6 destination address prefix.";
             }
             leaf next-hop valid-lifetime {
               type inet:ipv6-address; uint32;
               units "seconds";
               default "2592000";
               description
           "IPv6 address of
                 "The value to be placed in the next hop.";
       } Valid Lifetime in the
                  Prefix Information option. The designated value of all
                  1's (0xffffffff) represents infinity.
                 ";
               reference
                 "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
                  AdvValidLifetime.";
             }

     /* RPC Methods */

     augment "/rt:active-route/rt:input/rt:destination-address" {
       when "rt:address-family='ipv6' and rt:safi='nlri-unicast'"
             leaf on-link-flag {
               type boolean;
               default "true";
               description
           "This augment is valid only
                 "The value to be placed in the on-link flag ('L-bit')
                  field in the Prefix Information option.";
               reference
                 "RFC 4861: Neighbor Discovery for IPv6 unicast."; IP version 6 (IPv6) -
                  AdvOnLinkFlag.";
             }
             leaf preferred-lifetime {
               type uint32;
               units "seconds";
               default "604800";
               description
                 "The 'address' leaf augments value to be placed in the 'rt:destination-address'
          parameter of Preferred Lifetime in
                  the 'rt:active-route' operation."; Prefix Information option, in seconds. The
                  designated value of all 1's (0xffffffff) represents
                  infinity.";
               reference
                 "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
                  AdvPreferredLifetime.";
             }
             leaf address autonomous-flag {
               type inet:ipv6-address; boolean;
               default "true";
               description
           "IPv6 destination address.";
                 "The value to be placed in the Autonomous Flag field in
                  the Prefix Information option.";
               reference
                 "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
                  AdvAutonomousFlag.";
             }
           }
         }
       }
     }

     augment "/rt:active-route/rt:output/rt:route" "/rt:routing-state/rt:routing-tables/rt:routing-table/"
           + "rt:routes/rt:route" {
       when "rt:address-family='ipv6' "../../rt:address-family = 'ipv6' and rt:safi='nlri-unicast'" ../../rt:safi = "
          + "'nlri-unicast'" {
         description
           "This augment is valid only for IPv6 unicast.";
       }
       description
         "Contents of
         "This augment defines the reply to 'rt:active-route' operation."; content of IPv6 unicast routes.";
       uses route-content;
     }

     /* Data nodes Configuration */

     augment "/rt:routing/rt:router/rt:interfaces/rt:interface" {
       when "/if:interfaces/if:interface[if:name=current()/rt:name]/"
          + "ip:ipv6/ip:enabled='true'" {
         description
           "This augment is only valid for router interfaces with
            enabled IPv6.";
       }
       description
         "IPv6-specific
         "Configuration of IPv6-specific parameters of router
          interfaces.";
       container ipv6-router-advertisements {
         description
           "Parameters
           "Configuration of IPv6 Router Advertisements."; Advertisements.

            See the corresponding parameters under /rt:routing-state for
            detailed descriptions and references.
           ";
         leaf send-advertisements {
           type boolean;
           default "false";
           description
             "A flag indicating whether or not the router sends periodic
              Router Advertisements and responds to Router
              Solicitations.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvSendAdvertisements.";
         }
         leaf max-rtr-adv-interval {
           type uint16 {
             range "4..1800";
           }
           units "seconds";
           default "600";
           description
             "The maximum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MaxRtrAdvInterval.";
         }
         leaf min-rtr-adv-interval {
           type uint16 {
             range "3..1350";
           }
           units "seconds";
           must ". <= 0.75 * ../max-rtr-adv-interval" {
             description
               "The value MUST NOT be greater than 75 % of
                'max-rtr-adv-interval'.";
           }
           description
             "The minimum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.

              The default value to be used operationally if this leaf is
              not configured is determined as follows:

              - if max-rtr-adv-interval >= 9 seconds, the default value
                is 0.33 * max-rtr-adv-interval;

              - otherwise it is 0.75 * max-rtr-adv-interval.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MinRtrAdvInterval.";
         }
         leaf managed-flag {
           type boolean;
           default "false";
           description
             "The boolean value to be placed in the 'Managed address
              configuration' flag field in the Router Advertisement.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvManagedFlag.";
         }
         leaf other-config-flag {
           type boolean;
           default "false";
           description
             "The boolean value to be placed in the 'Other
              configuration' flag field in the Router Advertisement.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvOtherConfigFlag.";
         }
         leaf link-mtu {
           type uint32;
           default "0";
           description
             "The value to be placed in MTU options sent by the router.
              A value of zero indicates that no MTU options are sent.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvLinkMTU.";
         }
         leaf reachable-time {
           type uint32 {
             range "0..3600000";
           }
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Reachable Time field in the
              Router Advertisement messages sent by the router. The
              value zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvReachableTime.";
         }
         leaf retrans-timer {
           type uint32;
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Retrans Timer field in the
              Router Advertisement messages sent by the router. The
              value zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvRetransTimer.";
         }
         leaf cur-hop-limit {
           type uint8;
           default "64";
           description
             "The default value to be placed in the Cur Hop Limit field
              in the Router Advertisement messages sent by the router.
              The value should be set to the current diameter of the
              Internet. The value zero means unspecified (by this
              router).

              The default SHOULD be set to the value specified in IANA
              Assigned Numbers that was in effect at the time of
              implementation.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvCurHopLimit.

              IANA: IP Parameters,
              http://www.iana.org/assignments/ip-parameters sent by the router.
             ";
         }
         leaf default-lifetime {
           type uint16 {
             range "0..9000";
           }
           units "seconds";
           description
             "The value to be placed in the Router Lifetime field of
              Router Advertisements sent from the interface, in seconds.
              MUST be either zero or between max-rtr-adv-interval and
              9000 seconds. A value of zero indicates that the router is
              not to be used as a default router. These limits may be
              overridden by specific documents that describe how IPv6
              operates over different link layers.

              If this parameter is not configured, a value of 3 *
              max-rtr-adv-interval SHOULD be used.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvDefaultLifeTime.";
         }
         container prefix-list {
           description
             "A list
             "Configuration of prefixes to be placed in Prefix
              Information options in Router Advertisement messages sent
              from the interface.

              By default, all prefixes that the router advertises via
              routing protocols as being on-link for the interface from
              which the advertisement is sent.

              Prefixes that are advertised by default but do not have
              their entries in the child 'prefix' list are advertised
              with the default values of all parameters.

              The link-local prefix SHOULD NOT be included in the list
              of advertised prefixes.
             ";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvPrefixList.";
           list prefix {
             key "prefix-spec";
             description
               "Advertised prefix entry.";
             leaf prefix-spec {
               type inet:ipv6-prefix;
               description
                 "IPv6 address prefix.";
             }
             choice control-adv-prefixes {
               default "advertise";
               description
                 "The prefix either may be explicitly removed from the
                  set of advertised prefixes, or parameters with which
                  it is advertised may be specified (default case).";
               leaf no-advertise {
                 type empty;
                 description
                   "The prefix will not be advertised.

                    This can be used for removing the prefix from the
                    default set of advertised prefixes.
                   ";
               }
               case advertise {
                 leaf valid-lifetime {
                   type uint32;
                   units "seconds";
                   default "2592000";
                   description
                     "The value to be placed in the Valid Lifetime in
                      the Prefix Information option, in seconds. The
                      designated value of all 1's (0xffffffff)
                      represents infinity.
                     ";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvValidLifetime."; option.";
                 }
                 leaf on-link-flag {
                   type boolean;
                   default "true";
                   description
                     "The value to be placed in the on-link flag
                      ('L-bit') field in the Prefix Information
                      option.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvOnLinkFlag.";
                 }
                 leaf preferred-lifetime {
                   type uint32;
                   units "seconds";
                   must ". <= ../valid-lifetime" {
                     description
                       "This value MUST NOT be greater than
                        valid-lifetime.";
                   }
                   default "604800";
                   description
                     "The value to be placed in the Preferred Lifetime
                      in the Prefix Information option, in seconds. The
                      designated value of all 1's (0xffffffff)
                      represents infinity.
                     ";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvPreferredLifetime."; option.";
                 }
                 leaf autonomous-flag {
                   type boolean;
                   default "true";
                   description
                     "The value to be placed in the Autonomous Flag
                      field in the Prefix Information option.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvAutonomousFlag.";
                 }
               }
             }
           }
         }
       }
     }

     augment "/rt:routing/rt:router/rt:routing-protocols/"
           + "rt:routing-protocol/rt:static-routes" {
       description
         "This augment defines the configuration of the 'static'
          pseudo-protocol with data specific for IPv6 unicast.";
       container ipv6 {
         description
           "Configuration of a 'static' pseudo-protocol instance
            consists of a list of routes.";
         list route {
           key "id";
           ordered-by "user";
           description
             "A user-ordered list of static routes.";
           leaf id {
             type uint32 {
               range "1..max";
             }
             description
               "Numeric identifier of the route.

                It is not required that the routes be sorted by their
                'id'.
               ";

           }
           leaf description {
             type string;
             description
               "Textual description of the route.";
           }
           uses rt:route-content;
           uses route-content {
             refine "dest-prefix" {
               mandatory "true";
             }
           }
         }
       }
     }

     augment "/rt:routing/rt:routing-tables/rt:routing-table/rt:routes/"
           + "rt:route" {
       when "../../rt:address-family = 'ipv6' and ../../rt:safi = "
          + "'nlri-unicast'" {
         description
           "This augment is valid only for IPv6 unicast.";
       }
       description
         "This augment defines the content of IPv6 unicast routes.";
       uses route-content; rt:route-content;
           uses route-content {
             refine "dest-prefix" {
               mandatory "true";
             }
           }
         }
       }
     }
   }

   <CODE ENDS>

9.  IANA Considerations

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number (and remove this note).

   This document registers the following namespace URIs in the IETF XML
   registry [RFC3688]:

   ----------------------------------------------------------
   URI: urn:ietf:params:xml:ns:yang:ietf-routing

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.
   ----------------------------------------------------------

   ----------------------------------------------------------
   URI: urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.
   ----------------------------------------------------------

   ----------------------------------------------------------
   URI: urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.
   ----------------------------------------------------------

   This document registers the following YANG modules in the YANG Module
   Names registry [RFC6020]:

   -------------------------------------------------------------------
   name:         ietf-routing
   namespace:    urn:ietf:params:xml:ns:yang:ietf-routing
   prefix:       rt
   reference:    RFC XXXX
   -------------------------------------------------------------------

   -------------------------------------------------------------------
   name:         ietf-ipv4-unicast-routing
   namespace:    urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing
   prefix:       v4ur
   reference:    RFC XXXX
   -------------------------------------------------------------------

   -------------------------------------------------------------------
   name:         ietf-ipv6-unicast-routing
   namespace:    urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing
   prefix:       v6ur
   reference:    RFC XXXX
   -------------------------------------------------------------------

10.  Security Considerations

   Configuration and state data conforming to the core routing data
   model (defined in this document) are designed to be accessed via the
   NETCONF protocol [RFC6241].  The lowest NETCONF layer is the secure
   transport layer and the mandatory-to-implement secure transport is
   SSH [RFC6242].

   A number of data nodes defined in the YANG modules belonging to the
   configuration part of the core routing data model are writable/creatable/deletable writable/
   creatable/deletable (i.e., "config true" in YANG terms, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations to these data nodes,
   such as "edit-
   config", "edit-config", can have negative effects on the network if
   the protocol operations are not properly protected.

   The vulnerable "config true" subtrees and data nodes are the
   following:

   /routing/router/interfaces/interface  This list assigns a network
      layer interface to a router instance and may also specify
      interface parameters related to routing.

   /routing/router/routing-protocols/routing-protocol  This list
      specifies the routing protocols configured on a device.

   /routing/route-filters/route-filter  This list specifies the
      configured route filters which represent administrative policies
      for redistributing and modifying routing information.

   /routing/routing-tables/routing-table  This list specifies the
      configured routing tables used by the device.

   Unauthorized access to any of these lists can adversely affect the
   routing subsystem of both the local device and the network.  This may
   lead to network malfunctions, delivery of packets to inappropriate
   destinations and other problems.

11.  Acknowledgments

   The author wishes to thank Martin Bjorklund, Joel Halpern,
   Wes Hardaker, Andrew McGregor, Xiang Li, Thomas Morin, Tom Petch,
   Bruno Rijsman, Juergen Schoenwaelder, Phil Shafer, Dave Thaler and
   Yi Yang for their helpful comments and suggestions.

12.  References

12.1.  Normative References

   [IANA-IF-AF]

   [IANA-AF]  Bjorklund, M., "IANA Interface Type Address Family Numbers and Subsequent
              Address Family Identifiers YANG Modules", draft-ietf-netmod-iana-if-type-04 Module",
              draft-ietf-netmod-iana-afn-safi-00 (work in progress), June 2012.
              July 2013.

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

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

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

   [RFC6021bis]
              Schoenwaelder, J., Ed., "Common YANG Data Types",
              draft-ietf-netmod-rfc6021-bis-00
              draft-ietf-netmod-rfc6021-bis-03 (work in progress),
              February
              May 2013.

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

   [YANG-IF]  Bjorklund, M., "A YANG Data Model for Interface
              Configuration", draft-ietf-netmod-interfaces-cfg-09
              Management", draft-ietf-netmod-interfaces-cfg-12 (work in
              progress), February July 2013.

   [YANG-IP]  Bjorklund, M., "A YANG Data Model for IP Configuration", Management",
              draft-ietf-netmod-ip-cfg-09 (work in progress),
              February 2013.

12.2.  Informative References

   [RFC6087]  Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", RFC 6087, January 2011.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

Appendix A.  The Complete Data Tree Trees

   This appendix presents the complete configuration and operational
   state data tree trees of the core routing data model.

   See Section 2.2 for an explanation of symbols. the symbols used.  Data type of
   every leaf node is shown near the right end of the corresponding
   line.

A.1.  Configuration Data

 +--rw routing
    +--rw router router* [name]
    |  +--rw name                      string
    |  +--rw type?                     identityref
    |  +--rw enabled?                  boolean
    |  +--rw router-id?                yang:dotted-quad
    |  +--rw description?              string
    |  +--rw main-routing-tables default-routing-tables
    |  |  +--rw main-routing-table default-routing-table* [address-family safi]
    |  |     +--rw address-family    ianaaf:address-family
    |  |     +--rw safi              ianaaf:subsequent-address-family
    |  |     +--rw name?             routing-table-ref name              string
    |  +--rw interfaces
    |  |  +--rw interface interface* [name]
    |  |     +--rw name                               if:interface-ref
    |  |     +--rw v6ur:ipv6-router-advertisements
    |  |        +--rw v6ur:send-advertisements?    boolean
    |  |        +--rw v6ur:max-rtr-adv-interval?   uint16
    |  |        +--rw v6ur:min-rtr-adv-interval?   uint16
    |  |        +--rw v6ur:managed-flag?           boolean
    |  |        +--rw v6ur:other-config-flag?      boolean
    |  |        +--rw v6ur:link-mtu?               uint32
    |  |        +--rw v6ur:reachable-time?         uint32
    |  |        +--rw v6ur:retrans-timer?          uint32
    |  |        +--rw v6ur:cur-hop-limit?          uint8
    |  |        +--rw v6ur:default-lifetime?       uint16
    |  |        +--rw v6ur:prefix-list
    |  |           +--rw v6ur:prefix v6ur:prefix* [prefix-spec]
    |  |              +--rw v6ur:prefix-spec           inet:ipv6-prefix
    |  |              +--rw (control-adv-prefixes)?
    |  |                 +--:(no-advertise)
    |  |                 |  +--rw v6ur:no-advertise?         empty
    |  |                 +--:(advertise)
    |  |                    +--rw v6ur:valid-lifetime?       uint32
    |  |                    +--rw v6ur:on-link-flag?         boolean
    |  |                    +--rw v6ur:preferred-lifetime?   uint32
    |  |                    +--rw v6ur:autonomous-flag?      boolean
    |  +--rw routing-protocols
    |     +--rw routing-protocol routing-protocol* [name]
    |        +--rw name                        string
    |        +--rw description?                string
    |        +--rw enabled?                    boolean
    |        +--rw type                        identityref
    |        +--rw connected-routing-tables
    |        |  +--rw connected-routing-table connected-routing-table* [name]
    |        |     +--rw name             routing-table-ref
    |        |     +--rw import-filter?   route-filter-ref
    |        |     +--rw export-filter?   route-filter-ref
    |        +--rw static-routes
    |           +--rw v4ur:ipv4
    |           |  +--rw v4ur:route [id]  +--rw v4ur:route* [id]
    |           |     +--rw v4ur:id                    uint32
    |           |     +--rw v4ur:description?          string
    |           |     +--rw v4ur:outgoing-interface?   if:interface-ref
    |           |     +--rw v4ur:dest-prefix           inet:ipv4-prefix
    |           |     +--rw v4ur:next-hop?             inet:ipv4-address
    |           +--rw v6ur:ipv6
    |              +--rw v6ur:route* [id]
    |                 +--rw v6ur:id                    uint32
    |                 +--rw v6ur:description?          string
    |                 +--rw v6ur:outgoing-interface?   if:interface-ref
    |                 +--rw v6ur:dest-prefix           inet:ipv6-prefix
    |                 +--rw v6ur:next-hop?             inet:ipv6-address
    +--rw routing-tables
    |  +--rw routing-table* [name]
    |     +--rw name                    string
    |     +--rw address-family          ianaaf:address-family
    |     +--rw safi                    ianaaf:subsequent-address-family
    |     +--rw description?            string
    |     +--rw recipient-routing-tables
    |        +--rw recipient-routing-table* [name]
    |           +--rw name      routing-table-ref
    |           +--rw filter?   route-filter-ref
    +--rw route-filters
       +--rw route-filter* [name]
          +--rw name           string
          +--rw description?   string
          +--rw type           identityref

A.2.  Operational State Data

 +--ro routing-state
    +--ro router* [name]
    |  +--ro name                      string
    |  +--ro type?                     identityref
    |  +--ro router-id?                yang:dotted-quad
    |  +--ro default-routing-tables
    |  |  +--ro default-routing-table* [address-family safi]
    |  |     +--ro address-family    ianaaf:address-family
    |  |     +--ro safi              ianaaf:subsequent-address-family
    |  |     +--ro name              routing-table-state-ref
    |  +--ro interfaces
    |  |  +--ro interface* [name]
    |  |     +--ro name                         if:interface-state-ref
    |  |     +--ro v6ur:ipv6-router-advertisements
    |  |        +--ro v6ur:send-advertisements?    boolean
    |  |        +--ro v6ur:max-rtr-adv-interval?   uint16
    |  |        +--ro v6ur:min-rtr-adv-interval?   uint16
    |  |        +--ro v6ur:managed-flag?           boolean
    |  |        +--ro v6ur:other-config-flag?      boolean
    |  |        +--ro v6ur:link-mtu?               uint32
    |  |        +--ro v6ur:reachable-time?         uint32
    |  |        +--ro v6ur:retrans-timer?          uint32
    |  |        +--ro v6ur:cur-hop-limit?          uint8
    |  |        +--ro v6ur:default-lifetime?       uint16
    |  |        +--ro v6ur:prefix-list
    |  |           +--ro v6ur:prefix* [prefix-spec]
    |  |              +--ro v6ur:prefix-spec           inet:ipv6-prefix
    |  |     +--rw v4ur:id              +--ro v6ur:valid-lifetime?       uint32
    |  |     +--rw v4ur:description?          string              +--ro v6ur:on-link-flag?         boolean
    |  |     +--rw v4ur:outgoing-interface?   if:interface-ref              +--ro v6ur:preferred-lifetime?   uint32
    |  |     +--rw v4ur:dest-prefix           inet:ipv4-prefix              +--ro v6ur:autonomous-flag?      boolean
    |  +--ro routing-protocols
    |     +--rw v4ur:next-hop?             inet:ipv4-address     +--ro routing-protocol* [name]
    |           +--rw v6ur:ipv6        +--ro name                        string
    |              +--rw v6ur:route [id]        +--ro type                        identityref
    |                 +--rw v6ur:id                    uint32        +--ro connected-routing-tables
    |                 +--rw v6ur:description?          string           +--ro connected-routing-table* [name]
    |                 +--rw v6ur:outgoing-interface?   if:interface-ref              +--ro name             routing-table-state-ref
    |                 +--rw v6ur:dest-prefix           inet:ipv6-prefix              +--ro import-filter?   route-filter-state-ref
    |                 +--rw v6ur:next-hop?             inet:ipv6-address
    +--rw              +--ro export-filter?   route-filter-state-ref
    +--ro routing-tables
    |  +--rw routing-table  +--ro routing-table* [name]
    |     +--rw     +--ro name                    string
    |     +--rw     +--ro address-family          ianaaf:address-family
    |     +--rw     +--ro safi                    ianaaf:subsequent-address-family
    |     +--rw description?            string
    |     +--ro routes
    |     |  +--ro route route*
    |     |     +--ro outgoing-interface?   if:interface-ref   if:interface-state-ref
    |     |     +--ro source-protocol       string       identityref
    |     |     +--ro last-updated?         yang:date-and-time
    |     |     +--ro v4ur:dest-prefix?     inet:ipv4-prefix
    |     |     +--ro v4ur:next-hop?        inet:ipv4-address
    |     |     +--ro v6ur:dest-prefix?     inet:ipv6-prefix
    |     |     +--ro v6ur:next-hop?        inet:ipv6-address
    |     +--rw     +--ro recipient-routing-tables
    |        +--rw recipient-routing-table        +--ro recipient-routing-table* [name]
    |           +--rw           +--ro name      routing-table-ref      routing-table-state-ref
    |           +--rw           +--ro filter?   route-filter-ref
    +--rw   route-filter-state-ref
    +--ro route-filters
       +--rw route-filter
       +--ro route-filter* [name]
          +--rw
          +--ro name    string
          +--rw description?   string
          +--rw
          +--ro type    identityref

Appendix B.  Example: Adding a New Routing Protocol

   This appendix demonstrates how the core routing data model can be
   extended to support a new routing protocol.  The YANG module
   "example-rip" shown below is intended only as an illustration rather
   than a real definition of a data model for the RIP routing protocol.
   For the sake of brevity, we do not follow all the guidelines
   specified in [RFC6087].  See also Section 4.4.2.

   module example-rip {

     namespace "http://example.com/rip";

     prefix "rip";

     import ietf-routing {
       prefix "rt";
     }

     identity rip {
       base rt:routing-protocol;
       description
         "Identity for the RIP routing protocol.";
     }

     typedef rip-metric {
       type uint8 {
         range "0..16";
       }
     }

     grouping route-content {
       description
         "This grouping defines RIP-specific route attributes.";
       leaf metric {
         type rip-metric;
       }
       leaf tag {
         type uint16;
         default "0";
         description
           "This leaf may be used to carry additional info, e.g. AS
            number.";
       }
     }

     augment "/rt:routing/rt:routing-tables/rt:routing-table/rt:routes/" "/rt:routing-state/rt:routing-tables/rt:routing-table/"
           + "rt:route" "rt:routes/rt:route" {

       when "rt:source-protocol = 'rip:rip'" {
         description
           "This augment is only valid for a routes whose source
            protocol is RIP.";
       }
       description
         "RIP-specific route attributes.";
       uses route-content;
     }

     augment "/rt:active-route/rt:output/rt:route" {
       description
         "RIP-specific route attributes in the output of 'active-route'
          RPC.";
       uses route-content;
     }

     augment "/rt:routing/rt:router/rt:routing-protocols/"
           + "rt:routing-protocol" {
       when "rt:type = 'rip:rip'" {
         description
           'This
           "This augment is only valid for a routing protocol instance
            of type "rip".'; 'rip'.";
       }
       container rip {
         description
           "RIP instance configuration.";
         container interfaces {
           description
             "Per-interface RIP configuration.";
           list interface {
             key "name";
             description
               "RIP is enabled on interfaces that have an entry in this
                list, unless 'enabled' is set to 'false' for that
                entry.";
             leaf name {
               type leafref {
                 path "../../../../../../rt:interfaces/rt:interface/"
                    + "rt:name";
               }
             }
             leaf enabled {
               type boolean;
               default "true";
             }
             leaf metric {
               type rip-metric;
               default "1";
             }
           }
         }
         leaf update-interval {
           type uint8 {
             range "10..60";
           }
           units "seconds";
           default "30";
           description
             "Time interval between periodic updates.";
         }
       }
     }
   }

Appendix C.  Example: NETCONF <get> Reply

   This section contains a sample reply to the NETCONF <get> message,
   which could be sent by a server supporting (i.e., advertising them in
   the NETCONF <hello> message) the following YANG modules:

   o  ietf-interfaces [YANG-IF],

   o  ietf-ip [YANG-IP],

   o  ietf-routing (Section 6),

   o  ietf-ipv4-unicast-routing (Section 7),

   o  ietf-ipv6-unicast-routing (Section 8).

   We assume a simple network setup as shown in Figure 4: 5: router "A"
   uses static default routes with the "ISP" router as the next hop.
   IPv6 router advertisements are configured only on the "eth1"
   interface and disabled on the upstream "eth0" interface.

                   +-----------------+
                   |                 |
                   |    Router ISP   |
                   |                 |
                   +--------+--------+
                            |2001:db8:0:1::2
                            |192.0.2.2
                            |
                            |
                            |2001:db8:0:1::1
                        eth0|192.0.2.1
                   +--------+--------+
                   |                 |
                   |     Router A    |
                   |                 |
                   +--------+--------+
                        eth1|198.51.100.1
                            |2001:db8:0:2::1
                            |

                  Figure 4: 5: Example network configuration

   A reply to the NETCONF <get> message sent by router "A" would then be
   as follows:

   <?xml version="1.0"?>
   <rpc-reply
     message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns:v4ur="urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing"
     xmlns:v6ur="urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing"
     xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces"
     xmlns:ip="urn:ietf:params:xml:ns:yang:ietf-ip"
     xmlns:rt="urn:ietf:params:xml:ns:yang:ietf-routing">
    <data>
     <if:interfaces>
      <if:interface>
       <if:name>eth0</if:name>
       <if:type>ethernetCsmacd</if:type>
      <if:location>eth0</if:location>
       <if:description>
         Uplink to ISP.
       </if:description>
       <ip:ipv4>
        <ip:address>
         <ip:ip>192.0.2.1</ip:ip>
         <ip:prefix-length>24</ip:prefix-length>
        </ip:address>
        <ip:forwarding>true</ip:forwarding>
       </ip:ipv4>
       <ip:ipv6>
        <ip:address>
         <ip:ip>2001:0db8:0:1::1</ip:ip>
         <ip:prefix-length>64</ip:prefix-length>
        </ip:address>
        <ip:forwarding>true</ip:forwarding>
        <ip:autoconf>
         <ip:create-global-addresses>false</ip:create-global-addresses>
        </ip:autoconf>
       </ip:ipv6>
      </if:interface>
      <if:interface>
       <if:name>eth1</if:name>
       <if:type>ethernetCsmacd</if:type>
      <if:location>eth1</if:location>
       <if:description>
         Interface to the internal network.
       </if:description>
       <ip:ipv4>
        <ip:address>
         <ip:ip>198.51.100.1</ip:ip>
         <ip:prefix-length>24</ip:prefix-length>
        </ip:address>
        <ip:forwarding>true</ip:forwarding>
       </ip:ipv4>
       <ip:ipv6>
        <ip:address>
         <ip:ip>2001:0db8:0:2::1</ip:ip>
         <ip:prefix-length>64</ip:prefix-length>
        </ip:address>
        <ip:forwarding>true</ip:forwarding>
        <ip:autoconf>
         <ip:create-global-addresses>false</ip:create-global-addresses>
        </ip:autoconf>
       </ip:ipv6>
      </if:interface>
     </if:interfaces>
     <if:interfaces-state>
      <if:interface>
       <if:name>eth0</if:name>
       <if:type>ethernetCsmacd</if:type>
       <if:phys-address>00:0C:42:E5:B1:E9</if:phys-address>
       <if:oper-status>up</if:oper-status>
       <if:statistics>
        <if:discontinuity-time>
          2013-07-02T17:11:27+00:58
        </if:discontinuity-time>
       </if:statistics>
      </if:interface>
      <if:interface>
       <if:name>eth1</if:name>
       <if:type>ethernetCsmacd</if:type>
       <if:oper-status>up</if:oper-status>
       <if:phys-address>00:0C:42:E5:B1:EA</if:phys-address>
       <if:statistics>
        <if:discontinuity-time>
          2013-07-02T17:11:27+00:59
        </if:discontinuity-time>
       </if:statistics>
      </if:interface>
     </if:interfaces-state>
     <rt:routing>
      <rt:router>
       <rt:name>rtr0</rt:name>
      <rt:router-id>192.0.2.1</rt:router-id>
       <rt:description>Router A</rt:description>
      <rt:main-routing-tables>
       <rt:main-routing-table>
        <rt:address-family>ipv4</rt:address-family>
        <rt:safi>nlri-unicast</rt:safi>
        <rt:name>ipv4-unicast</rt:name>
       </rt:main-routing-table>
       <rt:main-routing-table>
        <rt:address-family>ipv6</rt:address-family>
        <rt:safi>nlri-unicast</rt:safi>
        <rt:name>ipv6-unicast</rt:name>
       </rt:main-routing-table>
      </rt:main-routing-tables>
       <rt:interfaces>
        <rt:interface>
        <rt:name>eth0</rt:name>
       </rt:interface>
       <rt:interface>
         <rt:name>eth1</rt:name>
         <v6ur:ipv6-router-advertisements>
          <v6ur:send-advertisements>true</v6ur:send-advertisements>
          <v6ur:prefix-list>
           <v6ur:prefix>
            <v6ur:prefix-spec>2001:db8:0:2::/64</v6ur:prefix-spec>
           </v6ur:prefix>
          </v6ur:prefix-list>

         </v6ur:ipv6-router-advertisements>
        </rt:interface>
       </rt:interfaces>
       <rt:routing-protocols>
        <rt:routing-protocol>
         <rt:name>st0</rt:name>
         <rt:description>
          Static routing is used for the internal network.
         </rt:description>
         <rt:type>rt:static</rt:type>
         <rt:static-routes>
          <v4ur:ipv4>
           <v4ur:route>
            <v4ur:id>1</v4ur:id>
            <v4ur:dest-prefix>0.0.0.0/0</v4ur:dest-prefix>
            <v4ur:next-hop>192.0.2.2</v4ur:next-hop>
           </v4ur:route>
          </v4ur:ipv4>
          <v6ur:ipv6>
           <v6ur:route>
            <v6ur:id>1</v6ur:id>
            <v6ur:dest-prefix>::/0</v6ur:dest-prefix>
            <v6ur:next-hop>2001:db8:0:1::2</v6ur:next-hop>
           </v6ur:route>
          </v6ur:ipv6>
         </rt:static-routes>
        </rt:routing-protocol>
       </rt:routing-protocols>
      </rt:router>
     </rt:routing>
     <rt:routing-state>
      <rt:router>
       <rt:name>rtr0</rt:name>
       <rt:router-id>192.0.2.1</rt:router-id>
       <rt:default-routing-tables>
        <rt:default-routing-table>
         <rt:address-family>ipv4</rt:address-family>
         <rt:safi>nlri-unicast</rt:safi>
         <rt:name>ipv4-unicast</rt:name>
        </rt:default-routing-table>
        <rt:default-routing-table>
         <rt:address-family>ipv6</rt:address-family>
         <rt:safi>nlri-unicast</rt:safi>
         <rt:name>ipv6-unicast</rt:name>
        </rt:default-routing-table>
       </rt:default-routing-tables>
       <rt:interfaces>
        <rt:interface>
         <rt:name>eth0</rt:name>
        </rt:interface>
        <rt:interface>
         <rt:name>eth1</rt:name>
         <v6ur:ipv6-router-advertisements>
          <v6ur:send-advertisements>true</v6ur:send-advertisements>
          <v6ur:prefix-list>
           <v6ur:prefix>
            <v6ur:prefix-spec>2001:db8:0:2::/64</v6ur:prefix-spec>
           </v6ur:prefix>
          </v6ur:prefix-list>
         </v6ur:ipv6-router-advertisements>
        </rt:interface>
       </rt:interfaces>
       <rt:routing-protocols>
        <rt:routing-protocol>
         <rt:name>st0</rt:name>
         <rt:type>rt:static</rt:type>
        </rt:routing-protocol>
       </rt:routing-protocols>
      </rt:router>
      <rt:routing-tables>
       <rt:routing-table>
        <rt:name>ipv4-unicast</rt:name>
        <rt:address-family>ipv4</rt:address-family>
        <rt:safi>nlri-unicast</rt:safi>
        <rt:routes>
         <rt:route>
          <v4ur:dest-prefix>192.0.2.1/24</v4ur:dest-prefix>
          <rt:outgoing-interface>eth0</rt:outgoing-interface>
         <rt:source-protocol>direct</rt:source-protocol>
         <rt:last-updated>2012-10-02T17:11:27+01:00</rt:last-updated>
          <rt:source-protocol>rt:direct</rt:source-protocol>
          <rt:last-updated>2013-07-02T17:11:27+01:00</rt:last-updated>
         </rt:route>
         <rt:route>
          <v4ur:dest-prefix>198.51.100.0/24</v4ur:dest-prefix>
          <rt:outgoing-interface>eth1</rt:outgoing-interface>
         <rt:source-protocol>direct</rt:source-protocol>
         <rt:last-updated>2012-10-02T17:11:27+01:00</rt:last-updated>
          <rt:source-protocol>rt:direct</rt:source-protocol>
          <rt:last-updated>2013-07-02T17:11:27+01:00</rt:last-updated>
         </rt:route>
         <rt:route>
          <v4ur:dest-prefix>0.0.0.0/0</v4ur:dest-prefix>
         <rt:source-protocol>st0</rt:source-protocol>
          <rt:source-protocol>rt:static</rt:source-protocol>
          <v4ur:next-hop>192.0.2.2</v4ur:next-hop>
         <rt:last-updated>2012-10-02T18:02:45+01:00</rt:last-updated>
          <rt:last-updated>2013-07-02T18:02:45+01:00</rt:last-updated>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
       <rt:routing-table>
        <rt:name>ipv6-unicast</rt:name>
        <rt:address-family>ipv6</rt:address-family>
        <rt:safi>nlri-unicast</rt:safi>
        <rt:routes>
         <rt:route>
          <v6ur:dest-prefix>2001:db8:0:1::/64</v6ur:dest-prefix>
          <rt:outgoing-interface>eth0</rt:outgoing-interface>
         <rt:source-protocol>direct</rt:source-protocol>
         <rt:last-updated>2012-10-02T17:11:27+01:00</rt:last-updated>
          <rt:source-protocol>rt:direct</rt:source-protocol>
          <rt:last-updated>2013-07-02T17:11:27+01:00</rt:last-updated>
         </rt:route>
         <rt:route>
          <v6ur:dest-prefix>2001:db8:0:2::/64</v6ur:dest-prefix>
          <rt:outgoing-interface>eth1</rt:outgoing-interface>
         <rt:source-protocol>direct</rt:source-protocol>
         <rt:last-updated>2012-10-02T17:11:27+01:00</rt:last-updated>
          <rt:source-protocol>rt:direct</rt:source-protocol>
          <rt:last-updated>2013-07-02T17:11:27+01:00</rt:last-updated>
         </rt:route>
         <rt:route>
          <v6ur:dest-prefix>::/0</v6ur:dest-prefix>
          <v6ur:next-hop>2001:db8:0:1::2</v6ur:next-hop>
         <rt:source-protocol>st0</rt:source-protocol>
         <rt:last-updated>2012-10-02T18:02:45+01:00</rt:last-updated>
          <rt:source-protocol>rt:static</rt:source-protocol>
          <rt:last-updated>2013-07-02T18:02:45+01:00</rt:last-updated>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
      </rt:routing-tables>
    </rt:routing>
     </rt:routing-state>
    </data>
   </rpc-reply>

Appendix D.  Change Log

   RFC Editor: remove this section upon publication as an RFC.

D.1.  Changes Between Versions -09 and -10

   o  Added subtree for operational state data ("/routing-state").

   o  Terms "system-controlled entry" and "user-controlled entry"
      defined and used.

   o  New feature "user-defined-routing-tables".  Nodes that are useful
      only with user-defined routing tables are now conditional.

   o  Added grouping "router-id".

   o  In routing tables, "source-protocol" attribute of routes now
      reports only protocol type, and its datatype is "identityref".

   o  Renamed "main-routing-table" to "default-routing-table".

D.2.  Changes Between Versions -08 and -09

   o  Fixed "must" expresion for "connected-routing-table".

   o  Simplified "must" expression for "main-routing-table".

   o  Moved per-interface configuration of a new routing protocol under
      'routing-protocol'.  This also affects the 'example-rip' module.

D.2.

D.3.  Changes Between Versions -07 and -08

   o  Changed reference from RFC6021 to RFC6021bis.

D.3.

D.4.  Changes Between Versions -06 and -07

   o  The contents of <get-reply> in Appendix C was updated: "eth[01]"
      is used as the value of "location", and "forwarding" is on for
      both interfaces and both IPv4 and IPv6.

   o  The "must" expression for "main-routing-table" was modified to
      avoid redundant error messages reporting address family mismatch
      when "name" points to a non-existent routing table.

   o  The default behavior for IPv6 RA prefix advertisements was
      clarified.

   o  Changed type of "rt:router-id" to "ip:dotted-quad".

   o  Type of "rt:router-id" changed to "yang:dotted-quad".

   o  Fixed missing prefixes in XPath expressions.

D.4.

D.5.  Changes Between Versions -05 and -06

   o  Document title changed: "Configuration" was replaced by
      "Management".

   o  New typedefs "routing-table-ref" and "route-filter-ref".

   o  Double slashes "//" were removed from XPath expressions and
      replaced with the single "/".

   o  Removed uniqueness requirement for "router-id".

   o  Complete data tree is now in Appendix A.

   o  Changed type of "source-protocol" from "leafref" to "string".

   o  Clarified the relationship between routing protocol instances and
      connected routing tables.

   o  Added a must constraint saying that a routing table connected to
      the direct pseudo-protocol must not be a main routing table.

D.5.

D.6.  Changes Between Versions -04 and -05

   o  Routing tables are now global, i.e., "routing-tables" is a child
      of "routing" rather than "router".

   o  "must" statement for "static-routes" changed to "when".

   o  Added "main-routing-tables" containing references to main routing
      tables for each address family.

   o  Removed the defaults for "address-family" and "safi" and made them
      mandatory.

   o  Removed the default for route-filter/type and made this leaf
      mandatory.

   o  If there is no active route for a given destination, the "active-
      route" RPC returns no output.

   o  Added "enabled" switch under "routing-protocol".

   o  Added "router-type" identity and "type" leaf under "router".

   o  Route attribute "age" changed to "last-updated", its type is
      "yang:date-and-time".

   o  The "direct" pseudo-protocol is always connected to main routing
      tables.

   o  Entries in the list of connected routing tables renamed from
      "routing-table" to "connected-routing-table".

   o  Added "must" constraint saying that a routing table must not be
      its own recipient.

D.6.

D.7.  Changes Between Versions -03 and -04

   o  Changed "error-tag" for both RPC methods from "missing element" to
      "data-missing".

   o  Removed the decrementing behavior for advertised IPv6 prefix
      parameters "valid-lifetime" and "preferred-lifetime".

   o  Changed the key of the static route lists from "seqno" to "id"
      because the routes needn't be sorted.

   o  Added 'must' constraint saying that "preferred-lifetime" must not
      be greater than "valid-lifetime".

D.7.

D.8.  Changes Between Versions -02 and -03

   o  Module "iana-afn-safi" moved to I-D "iana-if-type".

   o  Removed forwarding table.

   o  RPC "get-route" changed to "active-route".  Its output is a list
      of routes (for multi-path routing).

   o  New RPC "route-count".

   o  For both RPCs, specification of negative responses was added.

   o  Relaxed separation of router instances.

   o  Assignment of interfaces to router instances needn't be disjoint.

   o  Route filters are now global.

   o  Added "allow-all-route-filter" for symmetry.

   o  Added Section 5 about interactions with "ietf-interfaces" and
      "ietf-ip".

   o  Added "router-id" leaf.

   o  Specified the names for IPv4/IPv6 unicast main routing tables.

   o  Route parameter "last-modified" changed to "age".

   o  Added container "recipient-routing-tables".

D.8.

D.9.  Changes Between Versions -01 and -02

   o  Added module "ietf-ipv6-unicast-routing".

   o  The example in Appendix C now uses IP addresses from blocks
      reserved for documentation.

   o  Direct routes appear by default in the forwarding table.

   o  Network layer interfaces must be assigned to a router instance.
      Additional interface configuration may be present.

   o  The "when" statement is only used with "augment", "must" is used
      elsewhere.

   o  Additional "must" statements were added.

   o  The "route-content" grouping for IPv4 and IPv6 unicast now
      includes the material from the "ietf-routing" version via "uses
      rt:route-content".

   o  Explanation of symbols in the tree representation of data model
      hierarchy.

D.9.

D.10.  Changes Between Versions -00 and -01

   o  AFN/SAFI-independent stuff was moved to the "ietf-routing" module.

   o  Typedefs for AFN and SAFI were placed in a separate "iana-afn-
      safi" module.

   o  Names of some data nodes were changed, in particular "routing-
      process" is now "router".

   o  The restriction of a single AFN/SAFI per router was lifted.

   o  RPC operation "delete-route" was removed.

   o  Illegal XPath references from "get-route" to the datastore were
      fixed.

   o  Section "Security Considerations" was written.

Author's Address

   Ladislav Lhotka
   CZ.NIC

   Email: lhotka@nic.cz