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Versions: 00 01 02 03 04 05 draft-ietf-netmod-yang-instance-file-format

Network Working Group                                         B. Lengyel
Internet-Draft                                                  Ericsson
Intended status: Standards Track                               B. Claise
Expires: August 10, 2018                             Cisco Systems, Inc.
                                                        February 6, 2018


     YANG Instance Data Files and their use for Documenting Server
                              Capabilities
               draft-lengyel-netmod-yang-instance-data-00

Abstract

   This document specifies a standard file format for YANG instance
   data, that is data that could be stored in a datastore and whose
   syntax and semantics is defined by YANG models.  Instance data files
   can be used to provide information that is defined in design time.
   There is a need to document Server capabilities (which are often
   specified in design time), which should be done using instance data
   files.

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 https://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 August 10, 2018.

Copyright Notice

   Copyright (c) 2018 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
   (https://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



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Terminology

   Instance Data Set: A named set of data items that can be used as
   instance data in a YANG data tree.

   Instance Data File: A file containing an instance data set formatted
   according to the rules described in this document.

2.  Introduction

   A YANG server has a number of server-capabilities that can be
   retrieved from the server using protocols like NETCONF or RESTCONF.
   YANG server capabilities include among other things

   o  data defined in ietf-yang-library (YANG modules, submodules,
      features, deviations, schema-mounts)

   o  datastores supported

   o  alarms supported (draft-vallin-ccamp-alarm-module)

   o  data nodes, subtrees that support or do not support on-change
      notifications (draft-ietf-netconf-yang-push)-

   o  netconf-capabilities

   o  etc.

   While it is good practice to allow a client to query these
   capabilites from the live YANG server, that is often not enough.
   Many of these server-capabilities are relatively stable.  They may
   change

   1.  only at upgrade, or

   2.  rarely (e.g. due to licensing), or

   3.  more frequently

   Most capabilities belong to type 1), some to type 2) and a relatively
   small set to type 3).  Many network nodes only have type 1) or type
   1+2) capabilities.  Stable capabilities are usually defined by a
   vendor in design time, before the product is released.  While these



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   capabilities can be retrieved from the live server in run-time, there
   is a strong need to provide the same data already during design time.
   (Often only a part of all the server capabilities can be made
   available.)

   Often when a network node is released an associated NMS (network
   management system) is also released with it.  The NMS depends on the
   capabilities of the YANG server.  During NMS implementation the
   information about server capabilities is needed.  If the information
   is not available early in some off-line document, but only as
   instance data from the network node, the NMS implementation will be
   delayed, because it has to wait for the network node to be ready.
   Also assuming that all NMS implementors will have a correctly
   configured network node available to retrieve data from, is a very
   expensive proposition.  (An NMS may handle dozens of node types.)

   Beside NMS implementors, system integrators and many others also need
   the same information early.  Examples could be model driven testing,
   generating documentation, etc.

   This document specifies a file format for YANG instance data and
   proposes to use it to provide server capability information, allowing
   vendors to specify capabilities together with the YANG modules.

   The same instance data file format can be used for other purposes,
   like providing initial data for any YANG module.  E.g. a basic set of
   access control groups can be provided either by a device vendor or an
   operator using a network device.

2.1.  Data Life cycle

   Data defined or documented in YANG Instance Data Sets may be used for
   preloading a YANG server with this data, but the server may populate
   the data without using the actual file in which case the Instance
   Data File is only used as documentation.

   While such data will usually not change, a data documented by
   Instance Data Files MAY be changed by the YANG server itself or by
   management operations.  It is out of scope for this document to
   specify a method to prevent this.

   Notifications about the change of data documented by Instance Data
   Sets may be supplied by e.g. the Yang-Push mechanism, but it is out
   of scope for this document.







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2.2.  Use Case 1: Early Documentation of Server Capabilites

   An operator wants to integrate his own in-house built management
   system with the network node from ACME Systems.  The management
   integration must be ready by the time the first AcmeRouter 9000 is
   installed in the network.  To do the integration the operator needs
   the the list of supported YANG modules and features.  While this list
   could be read from the ietf-yang-library via Netconf, in order to
   allow time for developing the management integration, the operator
   demands this information early.  The operator will value that this
   information is available in a standard format, that is actually the
   same format he can later read from the node via Netconf.

2.3.  Use Case 2: Preloading Data

   Defining Access control data is a complex task.  To help with this
   the device vendor pre-defines some of the data.  Among others a set
   of default groups (/nacm:nacm/nacm:groups) are defined e.g. "read-
   only", "operator", "sys-admin".  The operator will often use these
   default groups, but is also free to completely remove them and define
   his own set of groups.

3.  Instance Data File Format

   Two standard formats to represent YANG Instance Data are specified
   based on the XML and JSON serialization.  The XML format is defined
   in [RFC7950] while the JSON format is defined in [RFC7951] with the
   additions below.

   For both formats data is placed in a top level auxiliary container
   named "instance-data".  The purpose of the container, which is not
   part of the real data itself, is to contain the potentially multiple
   top level XML elements and to carry meta-data for the complete
   instance-data-set.

   The XML format SHALL follow the format returned for a NETCONF GET
   operation.  The <instance-data> container SHALL contain all data that
   would be inside the <data> wrapper element.  XML attributes SHOULD
   NOT be used, however if a SW receiving a YANG instance data file
   encounters XML attributes it MUST discard them silently, allowing
   them to be used later for other purposes.

   The JSON format SHALL follow the format of the reply returmed for a
   RESTCONF GET request directed at the datastore resource:
   {+restconf}/data.  ETags and Timestamps SHOULD NOT be included.

   A YANG Instance data file MUST contain a single instance data set.
   Instance data MUST conform to the corresponding YANG Modules.



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   Default values SHOULD NOT but MAY be included.  Config=true and
   config=false data may be mixed in the instance data file.  Instance
   data files MAY contain partial data sets.  This means mandatory, min-
   elements or require-instance=true constrains MAY be violated.

   Meta data, information about the data set itself SHALL be included in
   the instance data file.  Metadata SHALL be formulated following
   [RFC7952] using the annotations defined in module ietf-yang-instance-
   data-annotations.  All metadata SHOULD be connected to the top level
   "instance-data" container.  Meta data SHALL include:

   o  Name of the instance data set

   o  Revision date of the instance data set (later a semantic version
      MAY also be included)

   o  Description of the instance data set.  The description SHOULD
      contain information whether and how the data can change during the
      lifetime of the network element.

   Any other metadata may also be included after these items.

   <instance-data xmlns:ida=
       "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data-annotations"
       ida:instance-data-set="acme-router-modules"
       ida:revision="2108-01-25"
       ida:description="Defines the minimal set of modules that any acme
           will contain. These modules will always be present."
       ida:contact="info@acme.com">
     <modules xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
       <module>
         <name>ietf-system</>
         <revision>2014-08-06</revision>
         <!-- description "A later revision may be used."; -->
         <namespace>urn:ietf:params:xml:ns:yang:ietf-system</namespace>
         <conformance-type>implement</conformance-type>
         <feature>authentication</feature>
         <feature>radius-authentication</feature>
       </module>
     </modules>
   </instance-data>

                 Figure 1: XML Instance Data File example








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{
  "instance-data": {
      "@": {
        "ietf-yang-instance-data-annotations:instance-data-set":
          "acme-router-modules",
        "ietf-yang-instance-data-annotations:revision": "2108-01-25",
        "ietf-yang-instance-data-annotations:contact":
          "info@acme.com",
        "ietf-yang-instance-data-annotations:description":
          "Defines the set of modules that an acme-router will contain."
      },
    "ietf-yang-library:modules-state": {
      "module": [
        {
          "name": "ietf-system",
          "revision": "2014-08-06",
          "namespace": "urn:ietf:params:xml:ns:yang:ietf-system",
          "conformance-type": "implement",
          "feature": ["authentication", "radius-authentication"]
        }
      ]
    }
  }
}

                 Figure 2: JSON Instance Data File example

4.  Providing Initial Data

   YANG instance data files SHOULD be used to provide design time
   information about server capabilities.  The content of the instance
   data file SHOULD describe the capabilities of the server, however
   there is no general guarantee that the capabilities will not change
   over time.  Whether capabilities change and if so, when and how
   SHOULD be described either in the instance data file description
   statements or some other implementation specific manner.  The set of
   server capabilities to be documented will be defined by other
   standards and specifications, and is out of scope for this document.
   Whether and how the instance data files are used by SW implementing a
   YANG server is out of scope for this specification.

5.  YANG Model

   <CODE BEGINS> file "ietf-yang-instance-data-annotations.yang"

 module ietf-yang-instance-data-annotations {
    yang-version 1.1;
    namespace



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      "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data-annotations";
    prefix ida ;

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

    organization  "IETF NETMOD Working Group";
    contact
    "WG Web:   <https://datatracker.ietf.org/wg/netmodf/>

     WG List:  <mailto:netmod@ietf.org>

     Author:  Balazs Lengyel
        <mailto:balazs.lengyel@ericsson.com>";


    description "The module defines annotations to allow defining
       metadata for YANG Instance Data files.";
    reference  "RFC 7950, RFC 7962";

    revision 2017-08-24 {
       description  "Initial revision.";
       reference "RFC XXXX: YANG Instance Data";
    }

    md:annotation instance-data-set {
        type yang:yang-identifier;
       description "Defines the name of a YANG instance data set.

          The annotation SHALL only be used on the top level
          <data> element in RFC XXXX defined YANG Instance Data files.
          Exactly one instance-data-set annotation SHALL be used per
          <data> element.";
     }

     md:annotation contact {
        type string;
       description "Contains the same information the ontact statement
          carries for a YANG module.

          The annotation SHALL only be used on the top level
          <data> element in RFC XXXX defined YANG Instance Data files.
          Zero or one contact annotation SHALL be used per
          <data> element.";
     }

     md:annotation organization {
        type string;



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       description "Contains the same information the organization
          statement carries for a YANG module.

          The annotation SHALL only be used on the top level
          <data> element in RFC XXXX defined YANG instance data files.
          Zero or one organization annotation SHALL be used per
          <data> element.";
     }

     md:annotation revision {
        type string {
           pattern '\d{4}-\d{2}-\d{2}';
        }
       description "Specifies the data the instance-data-set was
          modified for this release.

          The annotation SHALL only be used on the top level
          <data> element in RFC XXXX defined YANG Instance Data files.
          One or more revision annotations SHALL be used per
          <data> element.
          A separate annotation SHOULD be added each time the
          instance-data-set is released.";
     }

     md:annotation description {
        type string;
       description "Defines the name of a YANG instance data set.

          The annotation SHALL be used on the top level <data> element
          in RFC XXXX defined YANG Instance Data files, and MAY be used
          on other data elements of an instance data file.
          Zero one description annotation SHALL be used per element, but
          exactly one description annotation SHALL be used on the top
          level <data> element.";
     }
 }

   <CODE ENDS>

6.  Security Considerations

   To be completed

7.  IANA Considerations

   No IANA action is requested.





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8.  References

8.1.  Normative References

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC7952]  Lhotka, L., "Defining and Using Metadata with YANG",
              RFC 7952, DOI 10.17487/RFC7952, August 2016,
              <https://www.rfc-editor.org/info/rfc7952>.

8.2.  Informative References

   [I-D.ietf-netconf-rfc7895bis]
              Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", draft-ietf-netconf-
              rfc7895bis-04 (work in progress), January 2018.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
              Nygaard, E., Bierman, A., and B. Lengyel, "YANG Datastore
              Subscription", draft-ietf-netconf-yang-push-13 (work in
              progress), February 2018.

   [I-D.vallin-ccamp-alarm-module]
              Vallin, S. and M. Bjorklund, "YANG Alarm Module", draft-
              vallin-ccamp-alarm-module-01 (work in progress), October
              2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses







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   Balazs Lengyel
   Ericsson
   xxx
   1117 Budapest
   Hungary

   Phone: +36-70-330-7909
   Email: balazs.lengyel@ericsson.com


   Benoit Claise
   Cisco Systems, Inc.
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

   Phone: +32 2 704 5622
   Email: bclaise@cisco.com

































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