Network Working Group A. Bierman
Internet-Draft YumaWorks
Intended status: Standards Track M. Bjorklund
Expires: October 29, 2016 Tail-f Systems
K. Watsen
Juniper Networks
April 27, 2016

YANG Module Library
draft-ietf-netconf-yang-library-06

Abstract

This document describes a YANG library, which provides information about all the YANG modules used by a network management server (e.g., a Network Configuration Protocol (NETCONF) server). Simple caching mechanisms are provided to allow clients to minimize retrieval of this information.

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 working documents as Internet-Drafts. The list of current Internet-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 29, 2016.

Copyright Notice

Copyright (c) 2016 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

There is a need for standard mechanisms to identify the YANG modules and submodules that are in use by a server that implements YANG data models. If a large number of YANG modules are utilized by the server, then the YANG library contents needed can be relatively large. This information changes very infrequently, so it is important that clients be able to cache the YANG library contents and easily identify whether their cache is out-of-date.

YANG library information can be different on every server, and can change at run-time or across a server reboot.

If the server implements multiple protocols to access the YANG-defined data, each such protocol has it's own conceptual instantiation of the YANG library.

The following information is needed by a client application (for each YANG module in the library) to fully utilize the YANG data modeling language:

1.1. Terminology

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].

The following terms are defined in [RFC6241]:

The following terms are defined in [I-D.ietf-netmod-rfc6020bis]:

The following terms are used within this document:

1.2. Tree Diagrams

A simplified graphical representation of the data model is used in this document. The meaning of the symbols in these diagrams is as follows:

2. YANG Module Library

The "ietf‑yang‑library" module provides information about the YANG library used by a server. This module is defined using YANG version 1, but it supports the description of YANG modules written in any revision of YANG.

YANG Tree Diagram for "ietf‑yang‑library" module:

   +--ro modules-state
      +--ro module-set-id    string
      +--ro module* [name revision]
         +--ro name                   yang:yang-identifier
         +--ro revision               union
         +--ro schema?                inet:uri
         +--ro namespace              inet:uri
         +--ro feature*               yang:yang-identifier
         +--ro deviation* [name revision]
         |  +--ro name        yang:yang-identifier
         |  +--ro revision    union
         +--ro conformance-type       enumeration
         +--ro submodules
            +--ro submodule* [name revision]
               +--ro name        yang:yang-identifier
               +--ro revision    union
               +--ro schema?     inet:uri
	    

2.1. modules-state

This mandatory container holds the identifiers for the YANG data model modules supported by the server.

2.1.1. modules-state/module-set-id

This mandatory leaf contains a unique implementation-specific identifier representing the current set of modules and submodules on a specific server. The value of this leaf MUST change whenever the set of modules and submodules in the YANG library changes. There is no requirement that the same set always results in the same module-set-id value.

This leaf allows a client to fetch the module list once, cache it, and only re-fetch it if the value of this leaf has been changed.

If the value of this leaf changes, the server also generates a "yang‑library‑change" notification, with the new value of "module‑set‑id".

Note that for a NETCONF server that implements YANG 1.1 [I-D.ietf-netmod-rfc6020bis], a change of the "module‑set‑id" value results in a new value for the :yang-library capability defined in [I-D.ietf-netmod-rfc6020bis]. Thus, if such a server implements NETCONF notifications [RFC5277], and the notification "netconf‑capability‑change" [RFC6470], a "netconf‑capability‑change" notification is generated whenever the "module‑set‑id" changes.

2.1.2. modules-state/module

This mandatory list contains one entry for each YANG data model module supported by the server. There MUST be an entry in this list for each revision of each YANG module that is used by the server. It is possible for multiple revisions of the same module to be imported, in addition to an entry for the revision that is implemented by the server.

2.2. YANG Library Module

The "ietf‑yang‑library" module defines monitoring information for the YANG modules used by a server.

The "ietf‑yang‑types" and "ietf‑inet‑types" modules from [RFC6991] are used by this module for some type definitions.

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

<CODE BEGINS> file "ietf-yang-library@2016-04-09.yang"

module ietf-yang-library {
  namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library";
  prefix "yanglib";

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

  organization
    "IETF NETCONF (Network Configuration) Working Group";

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

     WG Chair: Mehmet Ersue
               <mailto:mehmet.ersue@nsn.com>

     WG Chair: Mahesh Jethanandani
               <mailto:mjethanandani@gmail.com>

     Editor:   Andy Bierman
               <mailto:andy@yumaworks.com>

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

     Editor:   Kent Watsen
               <mailto:kwatsen@juniper.net>";

  description
    "This module contains monitoring information about the YANG
     modules and submodules that are used within a YANG-based
     server.

     Copyright (c) 2016 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.: remove this note
  // Note: extracted from draft-ietf-netconf-yang-library-06.txt

  // RFC Ed.: update the date below with the date of RFC publication
  // and remove this note.
  revision 2016-04-09 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Module Library.";
  }

  /*
   * Typedefs
   */

  typedef revision-identifier {
    type string {
      pattern '\d{4}-\d{2}-\d{2}';
    }
    description
      "Represents a specific date in YYYY-MM-DD format.";
  }

  /*
   * Groupings
   */

  grouping module-list {
    description
      "The module data structure is represented as a grouping
       so it can be reused in configuration or another monitoring
       data structure.";

    grouping common-leafs {
      description
        "Common parameters for YANG modules and submodules.";

      leaf name {
        type yang:yang-identifier;
        description
          "The YANG module or submodule name.";
      }
      leaf revision {
        type union {
          type revision-identifier;
          type string { length 0; }
        }
        description
          "The YANG module or submodule revision date.
           A zero-length string is used if no revision statement
           is present in the YANG module or submodule.";
      }
    }

    grouping schema-leaf {
      description
        "Common schema leaf parameter for modules and submodules.";

      leaf schema {
        type inet:uri;
        description
          "Contains a URL that represents the YANG schema
           resource for this module or submodule.

           This leaf will only be present if there is a URL
           available for retrieval of the schema for this entry.";
      }
    }

    list module {
      key "name revision";
      description
        "Each entry represents one revision of one module
         currently supported by the server.";

      uses common-leafs;
      uses schema-leaf;

      leaf namespace {
        type inet:uri;
        mandatory true;
        description
          "The XML namespace identifier for this module.";
      }
      leaf-list feature {
        type yang:yang-identifier;
        description
          "List of YANG feature names from this module that are
           supported by the server, regardless whether they are
           defined in the module or any included submodule.";
      }
      list deviation {
        key "name revision";
        description
          "List of YANG deviation module names and revisions
           used by this server to modify the conformance of
           the module associated with this entry.  Note that
           the same module can be used for deviations for
           multiple modules, so the same entry MAY appear
           within multiple 'module' entries.

           The deviation module MUST be present in the 'module'
           list, with the same name and revision values.
           The 'conformance-type' value will be 'implement' for
           the deviation module.";
        uses common-leafs;
      }
      leaf conformance-type {
        type enumeration {
          enum implement {
            description
              "Indicates that the server implements one or more
               protocol-accessible objects defined in the YANG module
               identified in this entry.  This includes deviation
               statements defined in the module.

               For YANG version 1.1 modules, there is at most one
               module entry with conformance type 'implement' for a
               particular module name, since YANG 1.1 requires that
               at most one revision of a module is implemented.

               For YANG version 1 modules, there SHOULD NOT be more
               than one module entry for a particular module name.";
          }
          enum import {
            description
              "Indicates that the server imports reusable definitions
               from the specified revision of the module, but does
               not implement any protocol accessible objects from
               this revision.

               Multiple module entries for the same module name MAY
               exist. This can occur if multiple modules import the
               same module, but specify different revision-dates in
               the import statements.";
          }
        }
        mandatory true;
        description
          "Indicates the type of conformance the server is claiming
           for the YANG module identified by this entry.";
      }
      container submodules {
        description
          "Contains information about all the submodules used
           by the parent module entry";

        list submodule {
          key "name revision";
          description
            "Each entry represents one submodule within the
             parent module.";
          uses common-leafs;
          uses schema-leaf;
        }
      }
    }
  }

  /*
   * Operational state data nodes
   */

  container modules-state {
    config false;
    description
      "Contains YANG module monitoring information.";

    leaf module-set-id {
      type string;
      mandatory true;
      description
        "Contains a server-specific identifier representing
         the current set of modules and submodules.  The
         server MUST change the value of this leaf if the
         information represented by the 'module' list instances
         has changed.";
    }

    uses module-list;
  }

  /*
   * Notifications
   */

  notification yang-library-change {
    description
      "Generated when the set of modules and submodules supported
       by the server has changed.";
    leaf module-set-id {
      type leafref {
        path "/yanglib:modules-state/yanglib:module-set-id";
      }
      mandatory true;
      description
        "Contains the module-set-id value representing the
         set of modules and submodules supported at the server at
         the time the notification is generated.";
    }
  }

}
	    

<CODE ENDS>

3. IANA Considerations

3.1. YANG Module Registry

This document registers one 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-yang-library
     Registrant Contact: The NETCONF WG of the IETF.
     XML: N/A, the requested URI is an XML namespace.
	    

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

  name:         ietf-yang-library
  namespace:    urn:ietf:params:xml:ns:yang:ietf-yang-library
  prefix:       yanglib
  // RFC Ed.: replace XXXX with RFC number and remove this note
  reference:    RFC XXXX
	    

4. Security Considerations

The YANG module defined in this memo is 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]. Authorization for access to specific portions of conceptual data and operations within this module is provided by the NETCONF access control model (NACM) [RFC6536].

Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:

5. Acknowledgements

Contributions to this material by Andy Bierman are based upon work supported by the The Space & Terrestrial Communications Directorate (S&TCD) under Contract No. W15P7T-13-C-A616. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of The Space & Terrestrial Communications Directorate (S&TCD).

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J. and A. Bierman, "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013.

6.2. Informative References

[I-D.ietf-netmod-rfc6020bis] Bjorklund, M., "The YANG 1.1 Data Modeling Language", Internet-Draft draft-ietf-netmod-rfc6020bis-11, February 2016.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008.
[RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF) Base Notifications", RFC 6470, DOI 10.17487/RFC6470, February 2012.

Appendix A. Change Log

    -- RFC Ed.: remove this section before publication.
	    

A.1. v05 to v06

A.2. v04 to v05

A.3. v03 to v04

A.4. v02 to v03

A.5. v01 to v02

A.6. v00 to v01

A.7. draft-ietf-netconf-restconf-03 to v00

Appendix B. Open Issues

    -- RFC Ed.: remove this section before publication.
	    

The YANG Library issue tracker can be found here:

   https://github.com/netconf-wg/yang-library/issues
	    

Authors' Addresses

Andy Bierman YumaWorks EMail: andy@yumaworks.com
Martin Bjorklund Tail-f Systems EMail: mbj@tail-f.com
Kent Watsen Juniper Networks EMail: kwatsen@juniper.net