NETMOD                                                         L. Lhotka
Internet-Draft                                                    CZ.NIC
Intended status: Standards Track                       February 20,                            May 25, 2012
Expires: August 23, November 26, 2012

              A YANG Data Model for Routing Configuration
                    draft-ietf-netmod-routing-cfg-02
                    draft-ietf-netmod-routing-cfg-03

Abstract

   This document contains a specification of four three YANG modules.
   Together they form the core routing data model which serves as a
   basis
   framework for configuring a routing subsystem.  It is therefore
   expected that this module 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 configurations - 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 23, November 26, 2012.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology and Notation . . . . . . . . . . . . . . . . . . .  4
     2.1.  Glossary of New Terms  . . . . . . . . . . . . . . . . . .  4
     2.2.  Prefixes in Data Node Names  . . . . . . . . . . . . . . .  5
   3.  Objectives . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  The Design of the Core Routing Data Model  . . . . . . . . . .  7
     4.1.  Router . . . . . . . . . . . . . . . . . . . . . . . . . . 10
       4.1.1.  Configuration of IPv6 Router Interfaces  . . . . . . . 10
     4.2.  Route  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.3.  Routing Tables . . . . . . . . . . . . . . . . . . . . . . 12
     4.4.  Routing Protocols  . . . . . . . . . . . . . . . . . . . . 13
       4.4.1.  Routing Pseudo-Protocols . . . . . . . . . . . . . . . 14
       4.4.2.  Defining New Routing Protocols . . . . . . . . . . . . 14
     4.5.  Route Filters  . . . . . . . . . . . . . . . . . . . . . . 17
     4.6.  RPC Operation Operations . . . . . . . . . . . . . . . . . . . . . . 18
       4.6.1.  Operation "active-route" . . . . . . . . . . . . . . . 18
       4.6.2.  Operation "route-count"  . . . . . . . . . . . . . . . 19
   5.  IANA AFN and SAFI  Interactions with Other YANG Modules . . . . . . . . . . . . . 20
     5.1.  Module "ietf-interfaces" . . . . . . . . . . . . . . . . 19 . 20
     5.2.  Module "ietf-ip" . . . . . . . . . . . . . . . . . . . . . 20
   6.  Routing YANG Module  . . . . . . . . . . . . . . . . . . . . . 27 22
   7.  IPv4 Unicast Routing YANG Module . . . . . . . . . . . . . . . 37 34
   8.  IPv6 Unicast Routing YANG Module . . . . . . . . . . . . . . . 41 38
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 49 47
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 51 49
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 52 50
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53 51
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 53 51
     12.2. Informative References . . . . . . . . . . . . . . . . . . 53 51
   Appendix A.  Example: Adding a New Routing Protocol  . . . . . . . 54 52
   Appendix B.  Example: Reply to the NETCONF <get> Message . . . . . 57 55
   Appendix C.  Change Log  . . . . . . . . . . . . . . . . . . . . . 63 60
     C.1.  Changes Between Versions -02 and -03 . . . . . . . . . . . 60
     C.2.  Changes Between Versions -01 and -02 . . . . . . . . . . . 63
     C.2. 60
     C.3.  Changes Between Versions -00 and -01 . . . . . . . . . . . 63 61
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 64 62

1.  Introduction

   This document contains a specification of four 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].

   o  Module "iana-afn-safi" contains two type definitions translating
      IANA registries "Address Family Numbers" [IANA-AFN] and
      "Subsequent Address Family Identifiers" [IANA-SAFI] to YANG
      enumerations.

   The first three

   These modules together define the so-called core routing data model.  This data model will serve model,
   which is proposed as a basis for the development of data models for
   more sophisticated routing configurations.  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, advanced functions such as
   route filtering or policy routing etc.  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  container

   o  data model

   o  data node

   o  data type

   o  identity

   o  mandatory node

   o  module

   o  operational state data

   o  prefix

   o  RPC operation

2.1.  Glossary of New Terms
   active route:  a route which is actually used for packet forwarding. 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. 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-cfg" "ietf-ipv4-unicast-routing" and
      "ietf-ipv6-unicast-routing-cfg"
      "ietf-ipv6-unicast-routing" modules.

   direct route:  a route to a directly connected network.

2.2.  Prefixes in Data Node Names

   In this document, names of data nodes 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 with their using the
   standard prefix associated with the corresponding YANG module, as
   shown in Table 1.

            +--------+---------------------------+------------+

           +--------+---------------------------+--------------+
           | Prefix | YANG module               | Reference    |
            +--------+---------------------------+------------+
           +--------+---------------------------+--------------+
           | eth ianaaf | ex-ethernet iana-afn-safi             | [YANG-IF] [IANA-IF-AF] |
           |        |                           |              |
           | if     | ietf-interfaces           | [YANG-IF]    |
           |        |                           |              |
           | ip     | ietf-ip                   | [YANG-IP]    |
           |        |                           |              |
           | rip    | example-rip               | Appendix A   |
           |        |                           |              |
           | rt     | ietf-routing              | Section 6    |
           |        |                           |              |
           | v4ur   | ietf-ipv4-unicast-routing | Section 7    |
           |        |                           |              |
           | v6ur   | ietf-ipv6-unicast-routing | Section 8    |
           |        |                           |              |
           | yang   | ietf-yang-types           | [RFC6021]    |
           |        |                           |              |
           | inet   | ietf-inet-types           | [RFC6021]    |
            +--------+---------------------------+------------+
           +--------+---------------------------+--------------+

             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.  The combined data hierarchy is shown in
   Figure 1, where brackets contain enclose list keys keys, "rw" means configuration,
   "ro" operational state data, and question marks
   indicate "?" means optional data nodes.  Nodes that represent configuration node.
   Parentheses enclose choice and case nodes, and case nodes are
   labeled also
   marked with "rw" while operational state data have the "ro" label. a colon (":").

   +--rw routing
      +--rw router [name]
      |  +--rw name
      |  +--rw router-id?
      |  +--rw description?
      |  +--rw enabled?
      |  +--rw interfaces
      |  |  +--rw interface [name]
      |  |     +--rw name
      |  |     +--rw v6ur:ipv6-router-advertisements
      |  |        +--rw v6ur:send-advertisements?
      |  |        +--rw v6ur:max-rtr-adv-interval?
      |  |        +--rw v6ur:min-rtr-adv-interval?
      |  |        +--rw v6ur:managed-flag?
      |  |        +--rw v6ur:other-config-flag?
      |  |        +--rw v6ur:link-mtu?
      |  |        +--rw v6ur:reachable-time?
      |  |        +--rw v6ur:retrans-timer?
      |  |        +--rw v6ur:cur-hop-limit?
      |  |        +--rw v6ur:default-lifetime?
      |  |        +--rw v6ur:prefix-list
      |  |           +--rw v6ur:prefix [seqno] [prefix-spec]
      |  |              +--rw v6ur:seqno v6ur:prefix-spec
      |  |              +--rw v6ur:prefix-spec? (control-adv-prefixes)?
      |  |                 +--:(no-advertise)
      |  |                 |  +--rw v6ur:no-advertise?
      |  |                 +--:(advertise)
      |  |                    +--rw v6ur:valid-lifetime?
      |  |                    +--rw v6ur:on-link-flag?
      |  |                    +--rw v6ur:preferred-lifetime?
      |  |                    +--rw v6ur:autonomous-flag?
      |  +--rw routing-protocols
      |  |  +--rw routing-protocol [name]
      |  |     +--rw name
      |  |     +--rw description?
      |  |     +--rw type
      |  |     +--rw connected-routing-tables
      |  |     |  +--rw routing-table [name]
      |  |     |     +--rw name
      |  |     |     +--rw import-filter?
      |  |     |     +--rw export-filter?
      |  |     +--rw static-routes
      |  |        +--rw v4ur:ipv4
      |  |        |  +--rw v4ur:route [seqno]
      |  |        |     +--rw v4ur:seqno
      |  |        |     +--rw v4ur:description?
      |  |        |     +--rw v4ur:outgoing-interface?
      |  |        |     +--rw v4ur:dest-prefix? v4ur:dest-prefix
      |  |        |     +--rw v4ur:next-hop?
      |  |        +--rw v6ur:ipv6
      |  |           +--rw v6ur:route [seqno]
      |  |              +--rw v6ur:seqno
      |  |              +--rw v6ur:description?
      |              +--rw v6ur:outgoing-interface?  |              +--rw v6ur:dest-prefix? v6ur:outgoing-interface?
      |              +--rw v6ur:next-hop?
         +--rw route-filters  |              +--rw route-filter [name] v6ur:dest-prefix
      |     +--rw name  |              +--rw description? v6ur:next-hop?
      |  +--rw type?
         +--rw routing-tables
      |     +--rw routing-table [name]
      |        +--rw name
      |        +--rw address-family?
      |        +--rw safi?
      |        +--rw description?
      |        +--ro routes
      |        |  +--ro route
      |        |     +--ro source-protocol? source-protocol
      |        |     +--ro last-modified? age
      |        |     +--ro v4ur:outgoing-interface?
      |        |     +--ro v4ur:dest-prefix?
      |        |     +--ro v4ur:next-hop?
      |        |     +--ro v6ur:outgoing-interface?
      |        |     +--ro v6ur:dest-prefix?
      |        |     +--ro v6ur:next-hop?
      |        +--rw recipient-routing-tables [recipient-name]
      |           +--rw recipient-routing-table [name]
      |              +--rw recipient-name name
      |              +--rw filter?
      +--rw route-filters
         +--rw 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 data model introduces
   several generic components of a routing framework: routers, routing
   tables containing routes, routing protocols, route filters protocols and RPC
   operations. 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 can be realized.

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

             Figure 2: Example setup of the routing subsystem

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

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

   o  Each routing protocol instance, including the "static" and
      "direct" pseudo-protocols, is connected to exactly 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  The forwarding information base (FIB) is a special routing table
      which must always be present.  Typically, the FIB contains the
      "direct" routes for all configured interfaces and also receives
      the active routes from the main routing table.  The operating
      system kernel uses this information for packet forwarding.

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

4.1.  Router

   Each router instance in the core routing data model represents a
   (logical) router whose configuration and operation is independent
   logical router.  The exact semantics of
   other router instances.  Although it it not enforced by the data
   model, different this term is left to
   implementations.  For example, router instances normally do not may be completely
   isolated virtual routers or, alternatively, they may internally share
   any data.  They may, however, communicate with each other via routing
   protocols.

   Logical network
   certain information.

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

   Implementations MAY specify additional rules for the assignment of
   interfaces to logical interface.
   A logical interface MUST NOT routers.  For example, it may be required that
   the sets of interfaces assigned to more than one router
   instance. different logical routers be
   disjoint.

   Apart from the key, each entry of the "/router/interfaces/interface" "rt:interface" list MAY contain
   other configuration or operational state data related to the
   corresponding logical router interface.

4.1.1.  Configuration of IPv6 Router Interfaces

   The module "ietf-ipv6-unicast-routing" augments the definition of the
   data node "/router/interfaces/interface" "rt:interface" 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).

   NOTE: The "IsRouter" flag, which is also required by [RFC4861], was
   omitted.  Is is expected that this variable will be
   implemented in
   another module, either "ietf-interfaces" or "ietf-ip". by the "ietf-ip" module [YANG-IP] (leaf "ip:ip-
   forwarding").

4.2.  Route

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

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

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

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

   The above list of route attributes is sufficient should suffice 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 in 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 -  "source-protocol": name of the routing protocol from which the
      route was originally obtained.

   o  last-modified - date and time of last modification, or
      installation,  "age": number of seconds since the route. route was created or last
      updated.

   Each routing table may only contain routes of the same address
   family.  Address family
   (AFN 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 translated into YANG enumeration types "ianaaf:address-
   family" and "ianaaf:subsequent-address-family" [IANA-IF-AF].

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

   At least the following two and/or "direct" pseudo-protocols, see
   Section 4.4.1.

   One routing tables table MUST be configured present for each router instance and each
   address family supported AFN/SAFI pair:

   1.  Forwarding information base (FIB) contains active routes that are
       used by that router instance.  It is the operating system kernel for forwarding datagrams.

   2.  Main so-
   called main routing table to which all routing protocol instances are
   supporting the given address family SHOULD be connected by default, with default.
   For the exception two address families that are part of the "direct" pseudo-
       protocol (Section 4.4): direct routes only appear in core routing data
   model, the names of the FIB
       table by default.

   The main routing table tables SHOULD serve be as the default source of active
   routes follows:

   o  "main-ipv4-unicast" for the FIB.

   One or more additional IPv4 unicast,

   o  "main-ipv6-unicast" for IPv6 unicast.

   Additional routing tables MAY be configured by creating new entries
   in the "routing-table" list, either being as a part of factory-default configuration
   configuration, or configured by the client. a client's action.

   The naming scheme for additional routing tables, as well as
   restrictions on the number and configurability of routing tables are implementation-
   specific.
   implementation-specific.

   The way how the routing system uses information from routing tables
   is outside the scope of this document.  Typically, implementations
   will either use a forwarding table, or perform a direct look-up in
   the main routing table in conjunction with a route cache.

   Every routing table can serve as a source of routes for other routing
   tables.  To achieve this, one or more recipient routing tables may be
   specified in the configuration of the source routing table.  In
   addition, a route filter may be configured for each recipient routing
   table, which selects and/or manipulates the routes that are passed on
   between the source and recipient routing table.

4.4.  Routing Protocols

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

   Each routing protocol instance is connected to exactly one routing
   table.
   table for each address family that the routing protocol instance
   supports.  By default, every routing protocol instance SHOULD be
   connected to the main routing table. table or tables.  An implementation MAY
   allow any or all routing protocol instances to be configured to use a
   different routing table.

   Routes learned from the network by a routing protocol are passed to
   the connected routing table table(s) and vice versa - routes appearing in a
   routing table are passed to all routing protocols connected to the
   table (except "direct" and "static" pseudo-protocols) and may be
   advertised by that protocol to the network.

   Two independent route filters (see Section 4.5) may be defined for a
   routing protocol instance to control 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 a routing
      protocol instance to the routing table,

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

   Note that, for historical reasons, 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 protocols 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 contain exactly one instance of the
   "direct" pseudo-protocol. pseudo-protocol type.  The name of this instance MUST also
   be "direct".  It is the source of direct routes which for all configured
   address families.  Direct routes are normally supplied by the
   operating system kernel, based on the
   detected and configured configuration of network interfaces, and they
   interface addresses, see Section 5.2.  Direct routes SHOULD by
   default appear in the FIB main routing table. table for each configured address
   family.  However, using the framework defined in this document, the
   target routing table for direct routes MAY be changed by connecting
   the "direct" protocol instance to a non-default routing table.
   Direct routes can also be filtered before they appear in the routing
   table.

   The "static" routing

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

4.4.1.

4.4.2.  Defining New Routing Protocols

   It is expected that future YANG modules will create data models for
   additional routing protocol types.  In order to do so, the  Such a new module has to define
   the protocol-specific information configuration and operational state data, and
   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.  Their definitions
      then defined, preferably in one
      place by means of defining a YANG grouping.  The new attributes
      have to be inserted as operational state data by augmenting the
      definition of "rt:route" inside "rt:routing-table", and possibly
      to other places in the configuration, operational state data and
      RPC input or output.

   o  Per-interface configuration parameters can be added by augmenting
      the data node "rt:interface" (the list of router interfaces).

   o  Other configuration parameters and operational state data can be
      defined by augmenting the "routing-protocol" data node.  By using
      the "when" statement, this augment SHOULD be made conditional and
      valid only if the value of the "rt:type" child leaf equals to the
      new protocol's identity.

   It is recommended RECOMMENDED that both per-interface and other configuration
   data specific to the new protocol be encapsulated in an appropriately
   named container.

   The above steps are implemented by the example YANG module for the
   RIP routing protocol in Appendix A.  First, the module defines a new
   identity for the RIP protocol:

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

   New route attributes specific to the RIP protocol ("metric" and
   "tag") are defined in a grouping and then added to the route
   definitions appearing in "routing-table" and in the output part of
   the "get-route" "active-route" RPC method:

   grouping route-content {
     description
       "RIP-specific route content.";
     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:router/rt:routing-tables/rt:routing-table/"
         + "rt:routes/rt:route" {
     when "../../../../rt:routing-protocols/"
        + "rt:routing-protocol[rt:name=current()/rt:source-protocol]/"
        + "rt:type='rip:rip'" {
       description
         "This augment is only valid if the source protocol from which
          the route originated is RIP.";
     }
     description
       "RIP-specific route components.";
     uses route-content;
   }

   augment "/rt:get-route/rt:output/rt:route" "/rt:active-route/rt:output/rt:route" {
     description
       "Add RIP-specific route content.";
     uses route-content;
   }

   Per-interface configuration data are defined by the following
   "augment" statement:

   augment "/rt:routing/rt:router/rt:interfaces/rt:interface" {
     when "../../rt:routing-protocols/rt:routing-protocol/rt:type  = "
        + "'rip:rip'";
     container rip {
       description
         "Per-interface RIP configuration.";
       leaf enabled {
         type boolean;
         default "true";
       }
       leaf metric {
         type rip-metric;
         default "1";
       }
     }
   }

   Finally, global RIP configuration data are integrated into the "rt:
   routing-protocol" node by using the following "augment" statement,
   which is valid only for routing protocol instances whose type is
   "rip:rip":

   augment "/rt:routing/rt:router/rt:routing-protocols/"
         + "rt:routing-protocol" {
     when "rt:type = 'rip:rip'";
     container rip {
       leaf update-interval {
         type uint8 {
           range "10..60";
         }
         units "seconds";
         default "30";
         description
           "Time interval between periodic updates.";
       }
     }
   }

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 properties. attributes.

   Route filters are global, which means that a configured route filter
   may be used by any or all router instances.

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

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

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

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

   Each route filter is identified by a name which MUST be unique within
   a router instance.  Its type MUST be specified by the "type" identity
   reference - this opens the space for multiple route filtering
   framework implementations.  The default value for the route filter
   type is the identity "deny-all-route-filter" defined in the "ietf-routing"
   module, which represents a route filtering policy in which all routes
   are rejected. "deny-all-route-filter".

4.6.  RPC Operation Operations

   The "ietf-routing" module defines the "get-route" two RPC operation.  It
   is used for querying operations:

   o  active-route,

   o  route-count.

   Their parameters and semantics are described in the following
   subsections.

4.6.1.  Operation "active-route"

   Description:  Retrieve one or more active routes from the forwarding
      information base (FIB) of a router
   instance.  The first input parameter is instance, i.e., the name route(s)
      that are currently used by that router instance for sending
      datagrams to the destination whose address is provided as an input
      parameter.

   Parameters:

      router-name:  Name of the router instance whose FIB is to be queried, and the second parameter is a
         queried.

      destination-address:  Network layer destination address.  Modules for particular address families for which
         the active routes are
   expected to augment requested.

   Positive Response:  One or more "route" elements containing the "destination-address" container with
      active route(s).

   Negative Response:

      If the
   "address" leaf, as it logical router is done in not found, the "ietf-ipv4-unicast-routing" and
   "ietf-ipv6-unicast-routing" modules.

   The server replies with sends an active "rpc-
      error" message with "error-tag" set to "missing-element", and
      "error-app-tag" set to "router-not-found".

      If no route which is used exists for forwarding
   datagrams to the given destination address within address, the selected router
   instance.  Again, modules for particular address families are
   expected server
      sends an "rpc-error" message with "error-tag" set to augment "data-
      missing" and "error-app-tag" set to "no-route".

4.6.2.  Operation "route-count"

   Description:  Retrieve the definition total number of output parameters with AFN/
   SAFI-specific contents.

5.  IANA AFN and SAFI YANG Module

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number and all occurrences routes in a routing table.

   Parameters:

      router-name:  Name of the revision date below with
   the date of RFC publication (and remove this note).

   <CODE BEGINS> file "iana-afn-safi@2012-02-20.yang"

   module iana-afn-safi {

     namespace "urn:ietf:params:xml:ns:yang:iana-afn-safi";

     prefix "ianaaf";

     organization
       "IANA";

     contact
       "Internet Assigned Numbers Authority

        Postal:
        ICANN
        4676 Admiralty Way, Suite 330
        Marina del Rey, CA 90292
        U. S. A.

        Tel: +1 310 823 9358
        E-Mail: iana&iana.org
       ";

     description
       "This YANG module provides two typedefs logical router containing YANG
        definitions for the following IANA-registered enumerations:

        - Address Family Numbers (AFN)

        - Subsequent Address Family Identifiers (SAFI)

        The latest revision routing
         table.

      routing-table:  Name of this YANG module can be obtained from the
        IANA web site.

        Copyright (c) 2012 IETF Trust and routing table.

   Positive Response:  Element "number-of-routes" containing the persons identified as
        authors of
      requested nonnegative number.

   Negative Response:  If the code. All rights reserved.

        Redistribution and use in source and binary forms, with logical router or
        without modification, the routing table is permitted pursuant to, not
      found, the server sends an "rpc-error" message with "error-tag"
      set to "missing-element", and subject "error-app-tag" set to "router-not-
      found" or "routing-table-not-found", respectively.

5.  Interactions with Other YANG Modules

   The semantics of the license terms contained in, core routing data model also depends on several
   configuration parameters that are defined in other YANG modules.  The
   following subsections describe these interactions.

5.1.  Module "ietf-interfaces"

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

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

      If this switch is set
        forth in Section 4.c of to "false" for a given network layer
      interface, the IETF Trust's Legal Provisions
        Relating device MUST behave exactly as if that interface was
      not assigned to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this 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 part of RFC XXXX; see the
        RFC itself set to "false" for full legal notices.
       ";

     revision 2012-02-20 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Configuration";
     }

     typedef address-family {
       type enumeration {
         enum other {
           value "0";
           description
             "none of the following";
         }
         enum ipV4 {
           value "1";
           description
             "IP Version 4";
         }
         enum ipV6 {
           value "2";
           description
             "IP Version 6";
         }
         enum nsap {
           value "3";
           description
             "NSAP";
         }
         enum hdlc {
           value "4";
           description
             "(8-bit multidrop)";
         }
         enum bbn1822 {
           value "5";
           description
             "BBN Report 1822";
         }
         enum all802 {
           value "6";
           description
             "(includes a given interface, then all 802 media plus Ethernet 'canonical
              format')";
         }
         enum e163 {
           value "7";
           description
             "E.163";
         }
         enum e164 {
           value "8";
           description
             "(SMDS, FrameRelay, ATM)";
         }
         enum f69 {
           value "9";
           description
             "(Telex)";
         }
         enum x121 {
           value "10";
           description
             "(X.25, Frame Relay)";
         }
         enum ipx {
           value "11";
           description
             "IPX (Internet Protocol Exchange)";
         }
         enum appleTalk {
           value "12";
           description
             "Apple Talk";
         }
         enum decnetIV {
           value "13";
           description
             "DEC Net Phase IV";
         }
         enum banyanVines {
           value "14";
           description
             "Banyan Vines";
         }
         enum e164withNsap {
           value "15";
           description
             "(E.164 with NSAP format subaddress)";
         }
         enum dns {
           value "16";
           description
             "(Domain Name System)";
         }
         enum distinguishedName {
           value "17";
           description
             "(Distinguished Name, per X.500)";
         }
         enum asNumber {
           value "18";
           description
             "(16-bit quantity, per the AS number space)";
         }
         enum xtpOverIPv4 {
           value "19";
           description
             "XTP over IP version 4";
         }
         enum xtpOverIpv6 {
           value "20";
           description
             "XTP over IP version 6";
         }
         enum xtpNativeModeXTP {
           value "21";
           description
             "XTP native mode XTP";
         }
         enum fibreChannelWWPN {
           value "22";
           description
             "Fibre Channel World-Wide Port Name";
         }
         enum fibreChannelWWNN {
           value "23";
           description
             "Fibre Channel World-Wide Node Name";
         }
         enum gwid {
           value "24";
           description
             "Gateway Identifier";
         }
         enum afi {
           value "25";
           description
             "AFI for L2VPN";
         }
       }
       description
         "This typedef
      IPv4 routing functions related to that interface MUST be disabled.

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

      If this switch is set to "false" for a YANG enumeration given interface, then the
      forwarding of IANA-registered address
          family numbers (AFN).";
       reference
         "Address Family Numbers. IANA, 2011-01-20.
          <http://www.iana.org/assignments/address-family-numbers/
          address-family-numbers.xml>

          IANA-ADDRESS-FAMILY-NUMBERS-MIB DEFINITIONS
          <http://www.iana.org/assignments/ianaaddressfamilynumbers-mib>
         ";
     }

     typedef subsequent-address-family {
       type enumeration {
         enum nlri-unicast {
           value "1";
           description
             "Network Layer Reachability Information used for unicast
              forwarding";
           reference
             "RFC4760";
         }
         enum nlri-multicast {
           value "2";
           description
             "Network Layer Reachability Information used 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 multicast
              forwarding";
           reference
             "RFC4760";
         }
         enum nlri-mpls {
           value "4";
           description
             "Network Layer Reachability Information (NLRI) with MPLS
              Labels";
           reference
             "RFC3107";
         }
         enum mcast-vpn {
           value "5";
           description
             "MCAST-VPN";

           reference
             "draft-ietf-l3vpn-2547bis-mcast-bgp-08";
         }
         enum nlri-dynamic-ms-pw {
           value "6";
           status "obsolete";
           description
             "Network Layer Reachability Information used a given interface, then all
      IPv6 routing functions related to that interface MUST be disabled.

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

      If this switch is set to "false" for Dynamic
              Placement a given interface, then the
      forwarding of Multi-Segment Pseudowires (TEMPORARY -
              Expires 2008-08-23)";
           reference
             "draft-ietf-pwe3-dynamic-ms-pw-13";
         }
         enum tunnel-safi {
           value "64";
           description
             "Tunnel SAFI";
           reference
             "draft-nalawade-kapoor-tunnel-safi-05";
         }
         enum vpls {
           value "65";
           description
             "Virtual Private LAN Service (VPLS)";
           reference
             "RFC4761, RFC6074";
         }
         enum bgp-mdt {
           value "66";
           description
             "BGP MDT SAFI";
           reference
             "RFC6037";
         }
         enum bgp-4over6 {
           value "67";
           description
             "BGP 4over6 SAFI";
           reference
             "RFC5747";
         }
         enum bgp-6over4 {
           value "68";
           description
             "BGP 6over4 SAFI";
           reference
             "mailto:cuiyong&tsinghua.edu.cn";
         }
         enum l1vpn-auto-discovery {
           value "69";
           description
             "Layer-1 VPN auto-discovery information";
           reference
             "draft-ietf-l1vpn-bgp-auto-discovery-05";
         }
         enum mpls-vpn {
           value "128";
           description
             "MPLS-labeled VPN address";
           reference
             "RFC4364";
         }
         enum multicast-bgp-mpls-vpn {
           value "129";
           description
             "Multicast 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 BGP/MPLS IP Virtual Private Networks
              (VPNs)";
           reference
             "draft-ietf-l3vpn-2547bis-mcast-10,
              draft-ietf-l3vpn-2547bis-mcast-10";
         }
         enum route-target-constraints {
           value "132";
           description
             "Route Target constraints";
           reference
             "RFC4684";
         }
         enum ipv4-diss-flow {
           value "133";
           description
             "IPv4 dissemination configuring IPv4 and
   IPv6 addresses and subnet masks.  Configuration of flow specification rules";
           reference
             "RFC5575";
         }
         enum vpnv4-diss-flow {
           value "134";
           description
             "IPv4 dissemination these parameters
   on an enabled interface MUST result in an immediate creation of flow specification rules";
           reference
             "RFC5575";
         }
         enum vpn-auto-discovery {
           value "140";
           description
             "VPN auto-discovery";

           reference
             "draft-ietf-l3vpn-bgpvpn-auto-09";
         }
       }
       description
         "This typedef the
   corresponding direct route (usually in the main routing table).  Its
   destination prefix is a YANG enumeration of IANA-registered
          subsequent set according to the configured IP address family identifiers (SAFI).";
       reference
         "Subsequent Address Family Identifiers (SAFI) Parameters. IANA,
          2011-03-04. <http://www.iana.org/assignments/safi-namespace/
          safi-namespace.xml>
         ";
     }
   }

   <CODE ENDS> and
   subnet 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@2012-02-20.yang" "ietf-routing@2012-05-24.yang"

   module ietf-routing {

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

     prefix "rt";

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

     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 module contains YANG definitions of module defines essential components that may be used
        for configuring a routing subsystem.

        Copyright (c) 2012 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 2012-02-20 2012-05-24 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Configuration";
     }

     /* Identities */

     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.

          Note that use of this filter is equivalent to no filter at
          all.
         ";
     }

     /* 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.";
     }

     /* Groupings */

     grouping afn-safi {
       leaf address-family {
         type ianaaf:address-family;
         default "ipV4"; "ipv4";
         description
           "Address family of routes in the routing table.";
       }
       leaf safi {
         type ianaaf:subsequent-address-family;
         default "nlri-unicast";
         description
           "Subsequent address family identifier of routes in the
            routing table.";
       }
       description
         "This grouping provides two parameters specifying address
          family and subsequent address family.";
     }

     grouping route-content {
       description
         "Generic parameters of routes.

          A module for an address family should define a specific
          version of this grouping containing 'uses rt:route-content'.
         ";
       leaf outgoing-interface {
         type if:interface-ref;
         description
           "Outgoing interface.";
       }
     }

     /* RPC Methods */

     rpc get-route active-route {
       description
         "Query the forwarding information base of a router instance
          whose name is given as
         "Return the first parameter 'router-name'. The
          second parameter 'destination-address' should be augmented active route (or multiple routes, in
          order the case of
          multi-path routing) to support a destination addresses of all supported
          address families. The server returns address.

          Parameters

          1. 'router-name',

          2. 'destination-address'.

          If the route which logical router with 'router-name' doesn't exist, then
          this operation will fail with error-tag 'missing-element' and
          error-app-tag 'router-not-found'.

          If there is
          currently used for forwarding datagrams to that destination
          address, or an error message, if no such active route exists."; for 'destination-address', then
          this operation will fail with error-tag 'data-missing' and
          error-app-tag 'no-route'.
         ";
       input {
         leaf router-name {
           type router-ref;
           mandatory "true";
           description
             "First parameter: name
             "Name of the router instance whose forwarding information
              base is being queried.";
         }
         container destination-address {
           uses afn-safi;
           description
             "Second parameter:
             "Network layer destination address.

              AFN/SAFI-specific modules must augment this container with
              a leaf named 'address'.

             ";
         }
       }
       output {
         container
         list route {
           min-elements "1";
           uses afn-safi;
           uses route-content;
           description
             "Contents of the reply
             "Route contents specific for each address family should be
              defined through augmenting.";
         }
       }
     }

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

          Parameters:

          1. 'router-name',

          2. 'routing-table-name'.

          If the logical router with 'router-name' doesn't exist, then
          this operation will fail with error-tag 'missing-element' and
          error-app-tag 'router-not-found'.

          If the routing table with 'routing-table-name' doesn't exist,
          then this operation will fail with error-tag 'missing-element'
          and error-app-tag 'routing-table-not-found'.
         ";
       input {
         leaf router-name {
           type router-ref;
           mandatory "true";
           description
             "Name of the router instance containing the routing
              table.";
         }
         leaf routing-table {
           type leafref {
             path "/routing/router/routing-tables/routing-table/name";
           }
           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 */

     container routing {
       description
         "Routing parameters.";
       list router {
         key "name";
         unique "interfaces/interface/name"; "router-id";
         description
           "Each
           'Each list entry is a container for configuration and
            operational state data of a single (logical) router."; router.

            Network layer interfaces assigned to the router must have
            their entries in the "interfaces" list.
           ';
         leaf name {
           type string;
           description
             "The unique router name.";
         }
         leaf router-id {
           type inet:ipv4-address;
           description
             "Global router ID in the form of an IPv4 address.

              An implementation may select a value if this parameter is
              not configured.

              Routing protocols may override this global parameter
              inside their configuration.
             ";
         }
         leaf description {
           type string;
           description
             "Textual description of the router.";

         }
         leaf enabled {
           type boolean;
           default "true";
           description
             "Enable or disable the router. The default value is 'true',
              which means that 'true'.

              If this parameter is false, the parent router instance is enabled.";
              disabled, despite any other configuration that might be
              present.
             ";
         }
         container interfaces {
           description
             "Router interface parameters.";
           list interface {
             key "name";
             description
               "List of logical network layer interfaces assigned to the router
                instance. Any logical interface can only be assigned to
                one router
                instance.";
             leaf name {
               type if:interface-ref;
               description
                 "A reference to the name of a configured logical network layer
                  interface.";
             }
           }
         }
         container routing-protocols {
           description
             "Container for the list of configured routing protocol
              instances.";
           list routing-protocol {
             key "name";
             description
               "An instance of a routing protocol.";
             leaf name {
               type string;
               description
                 "The name of the routing protocol instance.";
             }
             leaf description {
               type string;
               description
                 "Textual description of the routing protocol
                  instance.";
             }
             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 routing tables.";
               list routing-table {
                 must "not(../../../../routing-tables/"
                    + "routing-table[current()/" "routing-table[rt:name=current()/"
                    + "preceding-sibling::routing-table/name]/"
                    + "address-family=../../../../routing-tables/"
                    + "routing-table[current()/name]/" "routing-table[rt:name=current()/name]/"
                    + "address-family and ../../../../routing-tables/"
                    + "routing-table[current()/" "routing-table[rt:name=current()/"
                    + "preceding-sibling::routing-table/name]/safi=../"
                    + "../../../routing-tables/routing-table[current()/" "../../../routing-tables/"
                    + "name]/safi)" "routing-table[rt:name=current()/name]/safi)" {
                   error-message "Each routing protocol may have no more "
                               + "more than one connected routing table "
                               + "table for each AFN and SAFI.";
                   description
                     "For each AFN/SAFI pair there may be at most one
                      connected routing table.";
                 }
                 key "name";
                 description
                   "List of routing tables to which the routing protocol
                    instance is connected.

                    Implementation may provide default

                    If no connected routing tables table is defined for some AFN/SAFI pairs, which are used if an
                    address family, the
                    corresponding entry is not configured. routing protocol should be
                    connected by default to the main routing table for
                    that address family.
                   ";
                 leaf name {
                   type leafref {
                     path "../../../../../routing-tables/routing-table/"
                        + "name";
                   }
                   description
                     "Reference to an existing routing table.";
                 }
                 leaf import-filter {
                   type leafref {
                     path "../../../../../route-filters/route-filter/"
                        + "name"; "/routing/route-filters/route-filter/name";
                   }
                   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 leafref {
                     path "../../../../../route-filters/route-filter/"
                        + "name"; "/routing/route-filters/route-filter/name";
                   }
                   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,
                      except for the 'direct' and 'static'
                      pseudo-protocols which accept no routes from any
                      routing table.";
                 }
               }
             }
             container static-routes {
               must "../type='static'" "../type='rt:static'" {
                 error-message "Static routes may be configured only for 'static'
                    routing protocol.";
                 description
                   "This container is only valid for the "
                             + "for 'static' routing protocol.";
               }
               description
                 "Configuration of 'static' pseudo-protocol.";
             }
           }
         }
         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 or 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
                 "The name of the route filter.";
             }
             leaf description {
               type string;
               description
                 "Textual description of the route filter.";
             }
             leaf type {
               type identityref {
                 base route-filter;
               }
               default "deny-all-route-filter";
                 description
                 "Type of the route-filter - an identity derived from
                  the 'route-filter' base identity. The default value
                  represents an all-blocking filter.";
                   "This container is only valid for the 'static'
                    routing protocol.";
               }
               description
                 "Configuration of 'static' pseudo-protocol.";
             }
           }
         }
         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 have the
                same AFN and SAFI.";
             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 routes {
               config "false";
               description
                 "Current contents of the routing table (operational
                  state data).";
               list route {
                 description
                   "A routing table entry. This data node must augmented
                    with information specific for routes of each address
                    family.";
                 uses route-content;
                 leaf source-protocol {
                   type leafref {
                     path "../../../../../routing-protocols/" "/routing/router/routing-protocols/"
                        + "routing-protocol/name";
                   }
                   mandatory "true";
                   description
                     "The name of the routing protocol instance from
                      which the route comes. This routing protocol must
                      be configured (automatically or manually) in the
                      device.";
                 }
                 leaf last-modified age {
                   type yang:date-and-time; uint32;
                   units "seconds";
                   mandatory "true";
                   description
                     "Time stamp of the last modification
                     "The number of seconds since the route.
                      If the route was never modified, it is the time
                      when the parent route was inserted to the routing
                      table.";
                      created or last updated.";
                 }
               }
             }
             list
             container recipient-routing-tables {
               description
                 "Container for recipient routing tables.";
               list recipient-routing-table {
                 key "recipient-name"; "name";
                 description
                   "A list of routing tables that receive routes from
                    this routing table.";
                 leaf recipient-name name {
                   type leafref {
                     path "../../../routing-table/name"; "/routing/router/routing-tables/"
                        + "routing-table/name";
                   }
                   description
                     "The name of the recipient routing table.";
                 }
                 leaf filter {
                   type leafref {
                     path "../../../../route-filters/route-filter/name"; "/routing/route-filters/route-filter/name";
                   }
                   description
                     "A route filter which is applied to the routes
                      passed on 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 or 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
               "The name of the route filter.";
           }
           leaf description {
             type string;
             description
               "Textual description of the route filter.";

           }
           leaf type {
             type identityref {
               base route-filter;
             }
             default "rt:deny-all-route-filter";
             description
               "Type of the route-filter - an identity derived from the
                'route-filter' base identity. The default value
                represents an all-blocking 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@2012-02-20.yang" "ietf-ipv4-unicast-routing@2012-05-25.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 YANG
        definitions for basic
        configuration of and operational state data for IPv4 unicast
        routing.

        Every implementation must preconfigure a routing table with the
        name 'main-ipv4-unicast', which is the main routing table for
        IPv4 unicast.

        Copyright (c) 2012 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 2012-02-20 2012-05-24 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Configuration";
     }

     /* Groupings */

     grouping route-content {
       description
         "Parameters of IPv4 unicast routes.";
       uses rt:route-content;
       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:get-route/rt:input/rt:destination-address" "/rt:active-route/rt:input/rt:destination-address" {
       when "address-family='ipV4' "address-family='ipv4' and 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:get-route' 'rt:active-route' operation.";

       leaf address {
         type inet:ipv4-address;
         description
           "IPv4 destination address.";
       }
     }

     augment "/rt:get-route/rt:output/rt:route" "/rt:active-route/rt:output/rt:route" {
       when "address-family='ipV4' "address-family='ipv4' and safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv4 unicast.";
       }
       description
         "Contents of the reply to 'rt:get-route' 'rt:active-route' operation.";
       uses route-content;
     }

     /* Data nodes */

     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 "seqno";
           ordered-by "user";
           description
             "A user-ordered list of static routes.";
           leaf seqno {
             type uint16; uint32 {
               range "1..max";
             }
             description
               "Sequential number of the route.";
           }
           leaf description {
             type string;
             description
               "Textual description of the route.";
           }
           uses route-content; rt:route-content;
           uses route-content {
             refine "dest-prefix" {
               mandatory "true";
             }
           }
         }
       }
     }

     augment "/rt:routing/rt:router/rt:routing-tables/rt:routing-table/"
           + "rt:routes/rt:route" {
       when "../../rt:address-family='ipV4' "../../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;
     }
   }

   <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@2012-02-20.yang" "ietf-ipv6-unicast-routing@2012-05-24.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";
     }

     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 YANG
        definitions basic
        configuration and operational state data for IPv6 unicast
        routing.

        Every implementation must preconfigure a routing table with the
        name 'main-ipv6-unicast', which is the main routing table for basic configuration of
        IPv6 unicast routing. unicast.

        Copyright (c) 2012 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 2012-02-20 2012-05-24 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Routing Configuration";
     }

     /* Groupings */

     grouping route-content {
       description
         "Specific parameters of IPv6 unicast routes.";
       uses rt:route-content;
       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:get-route/rt:input/rt:destination-address" "/rt:active-route/rt:input/rt:destination-address" {
       when "address-family='ipV6' "address-family='ipv6' and 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:get-route' 'rt:active-route' operation.";
       leaf address {
         type inet:ipv6-address;
         description
           "IPv6 destination address.";
       }
     }

     augment "/rt:get-route/rt:output/rt:route" "/rt:active-route/rt:output/rt:route" {
       when "address-family='ipV6' "address-family='ipv6' and safi='nlri-unicast'" {
         description
           "This augment is valid only for IPv6 unicast.";
       }
       description
         "Contents of the reply to 'rt:get-route' 'rt:active-route' operation.";
       uses route-content;
     }

     /* Data nodes */

     augment "/rt:routing/rt:router/rt:interfaces/rt:interface" {
       when "/if:interfaces/if:interface[name=current()/name] "
          + "/ip:ipv6/ip:enabled='true'" {
         description
           "This augment is only valid for router interfaces with
            enabled IPv6.

            NOTE: Parameter 'is-router' is not included, it is expected
            that it will be implemented by the 'ietf-ip' module.
           ";
       }
       description
         "IPv6-specific parameters of router interfaces.";
       container ipv6-router-advertisements {
         description
           "Parameters of IPv6 Router Advertisements.";
         reference
           "RFC 4861: Neighbor Discovery for IP version 6 (IPv6).

            RFC 4862: IPv6 Stateless Address Autoconfiguration.
           ";

         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.";
         }
         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.";
         }
         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.

              Must be no greater than 0.75 * max-rtr-adv-interval.

              Its default value is dynamic:

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

              The default value is dynamic and should be set to 3 *
              max-rtr-adv-interval.
             ";
         }
         container prefix-list {
           description
             "A list of prefixes to be placed in Prefix Information
              options in Router Advertisement messages sent from the
              interface.

              Default:

              By default, all prefixes that the 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 the list of advertised prefixes.
             ";
           list prefix {
             key "seqno";
             unique "prefix-spec";
             description
               "Advertised prefix entry.";
             leaf seqno {
               type uint8;
               description
                 "Sequential number of the 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 may 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.

                      Implementations may allow valid-lifetime to be
                      specified in two ways:

                      1. a time that decrements in real time, that is,
                         one that will result in a Lifetime lifetime of zero at
                         the specified time in the future,

                      2. a fixed time that stays the same in consecutive
                         advertisements.
                     ";
                 }
                 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.";
                 }
                 leaf preferred-lifetime {
                   type uint32;
                   units "seconds";
                   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.

                      Implementations MAY allow AdvPreferredLifetime preferred-lifetime to be
                      specified in two ways:

                      1. a time that decrements in real time, that is,
                         one that will result in a Lifetime lifetime of zero at a
                         specified time in the future,

                      2. a fixed time that stays the same in consecutive
                         advertisements.
                     ";
                 }
                 leaf autonomous-flag {
                   type boolean;
                   default "true";
                   description
                     "The value to be placed in the Autonomous Flag
                      field in the Prefix Information option.";
                 }
               }
             }
           }
         }
       }
     }

     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 "seqno";
           ordered-by "user";
           description
             "A user-ordered list of static routes.";
           leaf seqno {
             type uint16; uint32 {
               range "1..max";
             }
             description
               "Sequential number of the route.";
           }
           leaf description {
             type string;
             description
               "Textual description of the route.";
           }
           uses route-content; rt:route-content;
           uses route-content {
             refine "dest-prefix" {
               mandatory "true";
             }
           }
         }
       }
     }

     augment "/rt:routing/rt:router/rt:routing-tables/rt:routing-table/"
           + "rt:routes/rt:route" {
       when "../../rt:address-family='ipV6' "../../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;
     }
   }

   <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.
   ----------------------------------------------------------

   ----------------------------------------------------------
   URI: urn:ietf:params:xml:ns:yang:iana-afn-safi

   Registrant Contact: IANA.

   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
   -------------------------------------------------------------------

   -------------------------------------------------------------------
   name:         iana-afn-safi
   namespace:    urn:ietf:params:xml:ns:yang:iana-afn-safi
   prefix:       ianaaf
   reference:    RFC XXXX
   -------------------------------------------------------------------

10.  Security Considerations

   The YANG modules 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 are 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", 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:

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

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

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

   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, Thomas
   Morin, Tom Petch
   and Petch, Juergen Schoenwaelder Schoenwaelder, Dave Thaler and Yi Yang for
   their helpful comments and suggestions.

12.  References

12.1.  Normative References

   [IANA-AFN]
              IANA, "Address Family Numbers.", January 2011.

   [IANA-SAFI]
              IANA, "Subsequent

   [IANA-IF-AF]
              Bjorklund, M., "IANA Interface Type and Address Family Identifiers (SAFI)
              Parameters.", March 2011.
              YANG Modules", draft-ietf-netmod-iana-if-type-02 (work in
              progress), April 2012.

   [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.

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

   [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-03 draft-ietf-netmod-interfaces-cfg-04 (work
              in progress), February April 2012.

   [YANG-IP]  Bjorklund, M., "A YANG Data Model for IP Configuration",
              draft-ietf-netmod-ip-cfg-02
              draft-ietf-netmod-ip-cfg-03 (work in progress),
              February
              April 2012.

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.  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 4.4.1. 4.4.2.

   <CODE BEGINS> file "example-rip@2012-02-20.yang" "example-rip@2012-05-24.yang"

   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
         "RIP-specific route content.";
       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:router/rt:routing-tables/rt:routing-table/"
           + "rt:routes/rt:route" {
       when "../../../../rt:routing-protocols/"
          + "rt:routing-protocol[rt:name=current()/rt:source-protocol]/"
          + "rt:type='rip:rip'" {
         description
           "This augment is only valid if the source protocol from which
            the route originated is RIP.";
       }
       description
         "RIP-specific route components.";
       uses route-content;
     }

     augment "/rt:get-route/rt:output/rt:route" "/rt:active-route/rt:output/rt:route" {
       description
         "Add RIP-specific route content.";
       uses route-content;
     }

     augment "/rt:routing/rt:router/rt:interfaces/rt:interface" {
       when "../../rt:routing-protocols/rt:routing-protocol/rt:type = "
          + "'rip:rip'";
       container rip {
         description
           "Per-interface RIP configuration.";
         leaf enabled {
           type boolean;
           default "true";
         }
         leaf metric {
           type rip-metric;
           default "1";
         }
       }
     }

     augment "/rt:routing/rt:router/rt:routing-protocols/"
           + "rt:routing-protocol" {
       when "rt:type = 'rip:rip'";
       container rip {
         leaf update-interval {
           type uint8 {
             range "10..60";
           }
           units "seconds";
           default "30";
           description
             "Time interval between periodic updates.";
         }
       }
     }
   }

   <CODE ENDS>

Appendix B.  Example: Reply to the NETCONF <get> Message

   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  ex-ethernet [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 3: 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 3: Example network configuration

   Router "A" then could send the following XML document as its reply to
   the NETCONF <get> message:

  <?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:eth="http://example.com/ethernet"
      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>05:00.0</if:location>
      <ip:ipv4>
       <ip:address>
        <ip:ip>192.0.2.1</ip:ip>
        <ip:prefix-length>24</ip:prefix-length>
       </ip:address>
      </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: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>05:00.1</if:location>
      <ip:ipv4>
       <ip:address>
        <ip:ip>198.51.100.1</ip:ip>
        <ip:prefix-length>24</ip:prefix-length>
       </ip:address>
      </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:autoconf>
        <ip:create-global-addresses>false</ip:create-global-addresses>
       </ip:autoconf>
      </ip:ipv6>

     </if:interface>
    </if:interfaces>
    <rt:routing>
     <rt:router>
      <rt:name>rtr0</rt:name>
      <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:seqno>1</v6ur:seqno>
           <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>direct</rt:name>
        <rt:type>rt:direct</rt:type>
       </rt:routing-protocol>
       <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:seqno>1</v4ur:seqno>
           <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:seqno>1</v6ur:seqno>
           <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:connected-routing-tables>
         <rt:routing-table>
          <rt:name>ipv4-unicast-main</rt:name>
          <rt:name>main-ipv4-unicast</rt:name>
         </rt:routing-table>
         <rt:routing-table>
          <rt:name>ipv6-unicast-main</rt:name>
          <rt:name>main-ipv6-unicast</rt:name>
         </rt:routing-table>
        </rt:connected-routing-tables>
       </rt:routing-protocol>
      </rt:routing-protocols>
      <rt:routing-tables>
       <rt:routing-table>
        <rt:name>ipv4-unicast-fib</rt:name>
        <rt:name>main-ipv4-unicast</rt:name>
        <rt:routes>
         <rt:route>
          <v4ur:dest-prefix>192.0.2.1/24</v4ur:dest-prefix>
          <v4ur:outgoing-interface>eth0</v4ur:outgoing-interface>
          <rt:outgoing-interface>eth0</rt:outgoing-interface>
          <rt:source-protocol>direct</rt:source-protocol>
          <rt:last-modified>2012-02-20T17:11:27+01:00</rt:last-modified>
          <rt:age>3512</rt:age>
         </rt:route>
         <rt:route>
          <v4ur:dest-prefix>198.51.100.0/24</v4ur:dest-prefix>
          <v4ur:outgoing-interface>eth1</v4ur:outgoing-interface>
          <rt:outgoing-interface>eth1</rt:outgoing-interface>
          <rt:source-protocol>direct</rt:source-protocol>
          <rt:last-modified>2012-02-20T17:11:27+01:00</rt:last-modified>
          <rt:age>3512</rt:age>
         </rt:route>
         <rt:route>
          <v4ur:dest-prefix>0.0.0.0/0</v4ur:dest-prefix>
          <v4ur:next-hop>192.0.2.2</v4ur:next-hop>
          <rt:source-protocol>st0</rt:source-protocol>
          <rt:last-modified>2012-02-20T18:02:45+01:00</rt:last-modified>
          <v4ur:next-hop>192.0.2.2</v4ur:next-hop>
          <rt:age>2551</rt:age>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
       <rt:routing-table>
        <rt:name>ipv6-unicast-fib</rt:name>
        <rt:address-family>ipV6</rt:address-family>
        <rt:name>main-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>
          <v6ur:outgoing-interface>eth0</v6ur:outgoing-interface>
          <rt:outgoing-interface>eth0</rt:outgoing-interface>
          <rt:source-protocol>direct</rt:source-protocol>
          <rt:last-modified>2012-02-20T17:11:27+01:00</rt:last-modified>
          <rt:age>3513</rt:age>
         </rt:route>
         <rt:route>
          <v6ur:dest-prefix>2001:db8:0:2::/64</v6ur:dest-prefix>
          <v6ur:outgoing-interface>eth1</v6ur:outgoing-interface>
          <rt:outgoing-interface>eth1</rt:outgoing-interface>
          <rt:source-protocol>direct</rt:source-protocol>
          <rt:last-modified>2012-02-20T17:11:27+01:00</rt:last-modified>
         </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-modified>2012-02-20T18:02:45+01:00</rt:last-modified>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
       <rt:routing-table>
        <rt:name>ipv4-unicast-main</rt:name>
        <rt:recipient-routing-tables>
         <rt:recipient-name>ipv4-unicast-fib</rt:recipient-name>
        </rt:recipient-routing-tables>
        <rt:routes>
         <rt:route>
          <v4ur:dest-prefix>0.0.0.0/0</v4ur:dest-prefix>
          <rt:source-protocol>st0</rt:source-protocol>
          <v4ur:next-hop>192.0.2.2</v4ur:next-hop>
          <rt:last-modified>2012-02-20T18:02:45+01:00</rt:last-modified>
          <rt:age>3513</rt:age>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
       <rt:routing-table>
        <rt:name>ipv6-unicast-main</rt:name>
        <rt:address-family>ipV6</rt:address-family>
        <rt:safi>nlri-unicast</rt:safi>
        <rt:recipient-routing-tables>
         <rt:recipient-name>ipv6-unicast-fib</rt:recipient-name>
        </rt:recipient-routing-tables>
        <rt:routes>
         <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-modified>2012-02-20T18:02:45+01:00</rt:last-modified>
          <rt:age>2550</rt:age>
         </rt:route>
        </rt:routes>
       </rt:routing-table>
      </rt:routing-tables>
     </rt:router>
    </rt:routing>
   </data>
  </rpc-reply>

Appendix C.  Change Log

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

C.1.  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".

C.2.  Changes Between Versions -01 and -02

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

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

   o  Direct routes appear by default in the FIB table.

   o  Logical  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.

C.2.

C.3.  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