Network Working Group                                       M. Bjorklund
Internet-Draft                                            Tail-f Systems
Intended status: Standards Track                          April 11,                            May 20, 2011
Expires: October 13, November 21, 2011

             A YANG Data Model for Interface Configuration
                  draft-ietf-netmod-interfaces-cfg-00
                  draft-ietf-netmod-interfaces-cfg-01

Abstract

   This document defines a YANG data model for the configuration of
   network interfaces.  It is expected that interface type specific
   configuration data models augment the generic interfaces data model
   defined in this document.

Status of this Memo

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

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

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

   This Internet-Draft will expire on October 13, November 21, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Objectives . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Interfaces Data Model  . . . . . . . . . . . . . . . . . . . .  5
     3.1.  The interface List . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Interface References . . . . . . . . . . . . . . . . . . .  5  6
     3.3.  Interface Layering . . . . . . . . . . . . . . . . . . . .  6
   4.  Interfaces YANG Module . . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  Normative References . . . . . . . . . . . . . . . . . . . . . 15
   Appendix A.  Example: Ethernet Interface Module  . . . . . . . . . 16
   Appendix B.  Example: Ethernet Bonding Interface Module  . . . . . 18
   Appendix C.  Example: VLAN Interface Module  . . . . . . . . . . . 19
   Appendix D.  Example: IP Module  . . . . . . . . . . . . . . . . . 20
   Appendix E.  Example: NETCONF <get> reply  . . . . . . . . . . . . 21
   Appendix F.  ChangeLog . . . . . . . . . . . . . . . . . . . . . . 22
     F.1.  Version -01  . . . . . . . . . . . . . . . . . . . . . . . 22
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22 23

1.  Introduction

   This document defines a YANG [RFC6020] data model for the
   configuration of network interfaces.  It is expected that interface
   type specific configuration data models augment the generic
   interfaces data model defined in this document.

   Network interfaces are central to the configuration of many Internet
   protocols.  Thus, it is important to establish a common data model
   for how interfaces are identified and configured.

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14, [RFC2119].

2.  Objectives

   This section describes some of the design objectives for the model
   presented in Section 4.

   o  It is recognized that existing implementations will have to map
      the interface data model defined in this memo to their proprietary
      native data model.  The new data model should be simple to
      facilitate such mappings.

   o  The data model should be suitable for new implementations to use
      as-is, without requiring a mapping to a different native model.

   o  The data model must be extensible for different specific interface
      types, including vendor-specific types.

   o  References to interfaces should be as simple as possible,
      preferably by using a single leafref.

   o  The mapping to ifIndex [RFC2863] used by SNMP to identify
      interfaces must be clear.

   o  The model must support interface layering, both simple layering
      where one interface is layered on top of exactly one other
      interface, and more complex scenarios where one interface is
      aggregated over N other interfaces, or when N interfaces are
      multiplexed over one other interface.

   o  The data model should support the pre-provisioning of interface
      configuration, i.e., it should be possible to configure an
      interface whose physical interface hardware is not present on the
      device.  It is recommended that devices that support dynamic
      addition and removal of physical interfaces also support pre-
      provisioning.

3.  Interfaces Data Model

   The module "ietf-interfaces" has the following structure:

      +--rw interfaces
         +--rw interface [name]
            +--rw name                        string
            +--rw description?                string
            +--rw type                        ift:iana-if-type
            +--rw location?                   string
            +--rw enabled?                    boolean
            +--ro if-index*                   int32
            +--rw mtu?                        uint32
            +--rw link-up-down-trap-enable?   enumeration

   This module defines one YANG feature:

   snmp-if-mib:  Indicates that the server implements IF-MIB [RFC2863].

3.1.  The interface List

   The data model for interface configuration presented in this document
   uses a flat list of interfaces.  Each interface in the list is
   identified by its name.  Furthermore, each interface has a mandatory
   "type" leaf, and a "location" leaf.  The combination of "type" and
   "location" is unique within the interface list.

   It is expected that interface type specific data models augment the
   interface list, and use the "type" leaf to make the augmentation
   conditional.

   As an example of such an interface type specific augmentation,
   consider this YANG snippet.  For a more complete example, see
   Appendix A.

     import interfaces {
         prefix "if";
     }

     augment "/if:interfaces/if:interface" {
         when "if:type = 'ethernetCsmacd'";

         container ethernet {
             leaf duplex {
                 ...
             }
         }
     }

   The "location" leaf is a string.  It is optional in the data model,
   but if the type represents a physical interface, it is mandatory.
   The format of this string is device- and type-dependent.  The device
   uses the location string to identify the physical or logical entity
   that the configuration applies to.  For example, if a device has a
   single array of 8 ethernet ports, the location can be one of the
   strings "1" to "8".  As another example, if a device has N cards of M
   ports, the location can be on the form "n/m", such as "1/0".

   How a client can learn which types and locations are present on a
   certain device is outside the scope of this document.

3.2.  Interface References

   An interface is uniquely identified by its name.  This property is
   captured in the "interface-ref" typedef, which other YANG modules
   SHOULD use when they need to reference an existing interface.

3.3.  Interface Layering

   There is no generic mechanism for how an interface is configured to
   be layered on top of some other interface.  It is expected that
   interface type specific models define their own objects for interface
   layering, by using "interface-ref" types to reference lower layers.

   Below is an example of a model with such objects.  For a more
   complete example, see Appendix B.

     augment "/if:interfaces/if:interface" {
         when "if:type = 'ieee8023adLag'";

         leaf-list slave-if {
             type if:interface-ref;
             must "/if:interfaces/if:interface[if:name = current()]"
                + "/if:type = 'eth:ethernet'" {
                 description
                     "The type of a slave interface must be ethernet";
             }
         }
         // other bonding config params, failover times etc.
     }

4.  Interfaces YANG Module

   RFC Ed.: update the date below with the date of RFC publication and
   remove this note.

   This YANG module references [RFC2863].

   <CODE BEGINS> file "ietf-interfaces@2011-03-30.yang" "ietf-interfaces@2011-05-20.yang"

   module ietf-interfaces {

     namespace "urn:ietf:params:xml:ns:yang:ietf-interfaces";
     prefix "if"; if;

     import iana-if-type {
       prefix ift;
     }

     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:   Martin Bjorklund
                  <mailto:mbj@tail-f.com>";

     description
       "This module contains a collection of YANG definitions for
        configuring network interfaces.

        Copyright (c) 2011 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.";

     // RFC Ed.: replace XXXX with actual RFC number and remove this
     // note.

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2011-03-29 2011-05-20 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Interface Configuration";
     }

     /* Typedefs */

     typedef interface-ref {
       type leafref {
         path "/if:interfaces/if:interface/if:name";
       }
       description
         "This type is used by data models that need to reference
          interfaces.";
     }

     /* Features */

     feature snmp-if-mib {
       description
         "This feature indicates that the server implements IF-MIB,
          accessible over SNMP."; IF-MIB.";
       reference
         "RFC 2863: The Interfaces Group MIB";
     }

     /* Data nodes */

     container interfaces {
       description
         "Interface parameters.";

       list interface {
         key "name";
         unique "type location";

         description
           "The list of configured interfaces on the device.";

         leaf name {
           type string {
             length "1..255";

           }
           description
             "An arbitrary name for the interface.

              A device MAY restrict the allowed values for this leaf,
              possibly depending on the type and location.

              For example, if a device has a single array of 8 ethernet
              ports, the name might be restricted to be on the form
             'ethN', where N is an integer between '1' and '8'.";
         }

         leaf description {
           type string;
           description
             "A textual description of the interface.

              This leaf MAY be mapped to ifAlias by an implementation.
              Such an implementation MAY restrict the length of the
              value of this leaf so that it matches the restrictions
              of ifAlias.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifAlias";
         }

         leaf type {
           type ift:iana-if-type;
           mandatory true;
           description
             "The type of the interface.

              When an interface entry is created, a server MAY
              initialize the type leaf with a valid value, e.g., if it
              is possible to derive the type from the name of the
              interface.";
         }

         leaf location {
           type string;
           description
             "The device-specific location of the interface of a
              particular type.  The format of the location string
              depends on the interface type and the device.

              Media-specific modules must specify if the location
              is needed for the given type.

              For example, if a device has a single array of 8 ethernet
              ports, the location can be one of '1' to '8'.  As another
              example, if a device has N cards of M ports, the location
              can be on the form 'n/m'.

              When an interface entry is created, a server MAY
              initialize the location leaf with a valid value, e.g., if
              it is possible to derive the location from the name of
              the interface.";
         }

         leaf admin-status enabled {
           type enumeration {
             enum "up" {
               value 1;
             }
             enum "down" {
               value 2;
             }
           } boolean;
           default "up"; "true";
           description
             "The desired state of the interface.

              This leaf contains the configured, desired state of the
              interface.  Systems that implement the IF-MIB use the
              value of this leaf to set IF-MIB.ifAdminStatus after an
              ifEntry has been initialized, as described in RFC 2863.";
           // FIXME: Can we say that changing ifAdminStatus does NOT
           //        change this object?  If not, is the opposite
           //        always true, i.e. that changing ifAdminStatus
           //        results in a change of this object (in running)?
           //        Or should we be silent?
           reference
             "RFC 2863: The Interfaces Group MIB - ifAdminStatus";
         }

         leaf-list if-index {
           if-feature snmp-if-mib;
           type int32 {
             range "1..2147483647";
           }
           config false;
           description
             "The list of ifIndex values for all ifEntries that are
              represented by this interface.  If there is a one-to-one
              mapping between the interface and entries in the ifTable,
              this leaf-list will have a single value.

              Media-specific modules must specify how the type is
              mapped to entries in the ifTable.";
           reference
             "RFC 2863: The Interfaces Group MIB - ifIndex";
         }

         leaf mtu {
           type uint32;
           description
             "The size, in octets, of the largest packet that the
              interface can send and receive.  This node might not be
              valid for all interface types.

              Media-specific modules must specify any restrictions on
              the mtu for their interface type.";
         }

         leaf link-up-down-trap-enable {
           if-feature snmp-if-mib;
           type enumeration {
             enum enabled {
               value 1;
             }
             enum disabled {
               value 2;
             }
           }
           description
             "Indicates whether linkUp/linkDown SNMP traps should be
              generated for this interface.

              If this node is not configured, the value 'enabled' is
              operationally used by the server for interfaces which do
              not operate on top of any other intertface (as defined in
              the ifStackTable), and 'disabled' otherwise.";
           reference
             "RFC 2863: The Interfaces Group MIB -
                        ifLinkUpDownTrapEnable";
         }
       }
     }
   }

   <CODE ENDS>

5.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688].
   Following the format in RFC 3688, the following registration is
   requested to be made.

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

        Registrant Contact: The NETMOD WG of the IETF.

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

   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

     name:         ietf-interfaces
     namespace:    urn:ietf:params:xml:ns:yang:ietf-interfaces
     prefix:       if
     reference:    RFC XXXX

6.  Security Considerations

   TBD.

   The YANG module and submodules defined in this memo are designed to
   be accessed via the NETCONF protocol [I-D.ietf-netconf-4741bis].  The
   lowest NETCONF layer is the secure transport layer and the mandatory-
   to-implement secure transport is SSH [I-D.ietf-netconf-rfc4742bis].

   There are a number of data nodes defined in the YANG module and
   submodules which are writable/creatable/deletable (i.e., config true,
   which is the default).  These data nodes may be considered sensitive
   or vulnerable in some network environments.  Write operations (e.g.,
   edit-config) to these data nodes without proper protection can have a
   negative effect on network operations.  These are the subtrees and
   data nodes and their sensitivity/vulnerability:

   /interfaces/interface:  This list specify the configured interfaces
      on a device.  Unauthorized access to this list could cause the
      device to ignore packets destined to it.

   /interfaces/interface/enabled:  This leaf controls if an interface is
      enabled or not.  Unauthorized access to this leaf could cause the
      device to ignore packets destined to it.

7.  Acknowledgments

   The author wishes to thank Per Hedeland, Ladislav Lhotka, and Juergen
   Schoenwaelder for their helpful comments.

8.  Normative References

   [I-D.ietf-netconf-4741bis]
              Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)",
              draft-ietf-netconf-4741bis-10 (work in progress),
              March 2011.

   [I-D.ietf-netconf-rfc4742bis]
              Wasserman, M. and T. Goddard, "Using the NETCONF
              Configuration Protocol over Secure Shell (SSH)",
              draft-ietf-netconf-rfc4742bis-08 (work in progress),
              March 2011.

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

   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
              MIB", RFC 2863, June 2000.

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

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

Appendix A.  Example: Ethernet Interface Module

   This section gives a simple example of how an Ethernet interface
   module could be defined.  It demonstrates how media-specific
   configuration parameters can be conditionally augmented to the
   generic interface list.  It is not intended as a complete module for
   ethernet configuration.

   module ex-ethernet {
     namespace "http://example.com/ethernet";
     prefix "eth";

     import ietf-interfaces {
       prefix if;
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'ethernetCsmacd'";

       container ethernet {
         must "../if:location" {
           description
             "An ethernet interface must specify the physical location
              of the ethernet hardware.";
         }
         choice transmission-params {
           case auto {
             leaf auto-negotiate {
               type empty;
             }
           }
           case manual {
             leaf duplex {
               type enumeration {
                 enum "half";
                 enum "full";
               }
             }
             leaf speed {
               type enumeration {
                 enum "10Mb";
                 enum "100Mb";
                 enum "1Gb";
                 enum "10Gb";
               }
             }
           }
         }
         // other ethernet specific params...
       }
     }
   }

Appendix B.  Example: Ethernet Bonding Interface Module

   This section gives an example of how interface layering can be
   defined.  An ethernet bonding interface is defined, which bonds
   several ethernet interfaces into one logical interface.

   module ex-ethernet-bonding {
     namespace "http://example.com/ethernet-bonding";
     prefix "bond";

     import ietf-interfaces {
       prefix if;
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'ieee8023adLag'";

       leaf-list slave-if {
         type if:interface-ref;
         must "/if:interfaces/if:interface[if:name = current()]"
            + "/if:type = 'ethernetCsmacd'" {
           description
             "The type of a slave interface must be ethernet.";
         }
       }
       leaf bonding-mode {
         type enumeration {
           enum round-robin;
           enum active-backup;
           enum broadcast;
         }
       }
       // other bonding config params, failover times etc.
     }
   }

Appendix C.  Example: VLAN Interface Module

   This section gives an example of how a vlan interface module can be
   defined.

   module ex-vlan {
     namespace "http://example.com/vlan";
     prefix "vlan";

     import ietf-interfaces {
       prefix if;
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'ethernetCsmacd' or
             if:type = 'ieee8023adLag'";
       leaf vlan-tagging {
         type boolean;
         default false;
       }
     }

     augment "/if:interfaces/if:interface" {
       when "if:type = 'l2vlan'";

       leaf base-interface {
         type if:interface-ref;
         must "/if:interfaces/if:interface[if:name = current()]"
            + "/vlan:vlan-tagging = true" {
           description
             "The base interface must have vlan tagging enabled.";
         }
       }
       leaf vlan-id {
         type uint16 {
           range "1..4094";
         }
         must "../base-interface";
       }
     }
   }

Appendix D.  Example: IP Module

   This section gives an example how an IP module can be defined.

   module ex-ip {

     namespace "http://example.com/ip";
     prefix "ip";

     import ietf-interfaces {
       prefix if;
     }

     import ietf-inet-types {
       prefix inet;
     }

     augment "/if:interfaces/if:interface" {
       container ip {
         list address {
           key "ip";
           leaf ip {
             type inet:ip-address;
           }
           leaf prefix-length {
             type uint16;
             // range depends on type of address
           }
         }
       }
     }
   }

Appendix E.  Example: NETCONF <get> reply

   This section gives an example of a reply to the NETCOMF <get> request
   for a device that implements the example data models above.

   <rpc-reply
       xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
       message-id="101">
     <data>
       <interfaces
           xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
         <interface>
           <name>eth0</name>
           <type>ethernetCsmacd</type>
           <location>0</location>
           <admin-status>up</admin-status>
           <if-index>2</if-index>
           <ip xmlns="http://example.com/ip">
             <address>
               <ip>192.0.2.1</ip>
               <prefix-length>24</prefix-length>
             </address>
           </ip>
         </interface>
         <interface>
           <name>eth1</name>
           <type>ethernetCsmacd</type>
           <location>1</location>
           <admin-status>up</admin-status>
           <if-index>7</if-index>
           <ip xmlns="http://example.com/ip">
             <address>
               <ip>192.168.1.1</ip>
               <prefix-length>24</prefix-length>
             </address>
           </ip>
         </interface>
       </interfaces>
     </data>
   </rpc-reply>

Appendix F.  ChangeLog

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

F.1.  Version -01

   o  Changed leaf "if-admin-status" to leaf "enabled".

   o  Added Security Considerations

Author's Address

   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com