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Versions: 00 01 02 draft-nmdsdt-netmod-revised-datastores

Internet Engineering Task Force                                R. Wilton
Internet-Draft                                             Cisco Systems
Intended status: Experimental                          November 30, 2015
Expires: June 2, 2016


          "With-config-state" Capability for NETCONF/RESTCONF
                  draft-wilton-netmod-opstate-yang-01

Abstract

   This document proposes a possible alternative solution for handling
   applied configuration state in YANG as described in draft-openconfig-
   netmod-opstate-01.  The proposed solution, roughly modelled on the
   with-defaults NETCONF/RESTCONF capability, aims to meet the key
   requirements set out in draft-openconfig-netmod-opstate-01 without
   the need for YANG module authors to explicitly duplicate
   configuration nodes in both configuration and operational containers.
   This draft does not address the issue of co-location of configuration
   and operational state for interfaces, nor does it provide a NETCONF
   mechanism to retrieve operational data separately from configuration
   data.

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 June 2, 2016.

Copyright Notice

   Copyright (c) 2015 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



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   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
     1.1.  Change history  . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  "With-config-state" encoding scheme . . . . . . . . . . . . .   5
     3.1.  cfg-intended  . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  cfg-applied . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  cfg-status  . . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  cfg-status-reason . . . . . . . . . . . . . . . . . . . .   6
     3.5.  Non-leaf config nodes . . . . . . . . . . . . . . . . . .   7
   4.  Retrieval of intended and applied configuration . . . . . . .   7
     4.1.  all-cfg . . . . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  intended-cfg-only . . . . . . . . . . . . . . . . . . . .   8
     4.3.  applied-cfg-only  . . . . . . . . . . . . . . . . . . . .   8
     4.4.  diff-cfg-only . . . . . . . . . . . . . . . . . . . . . .   8
   5.  "With-config-state" Capability  . . . . . . . . . . . . . . .   8
     5.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Dependencies  . . . . . . . . . . . . . . . . . . . . . .   9
     5.3.  Capability Identifier . . . . . . . . . . . . . . . . . .   9
   6.  Suggested layout of data models . . . . . . . . . . . . . . .   9
   7.  Addressing the requirements of the Consistent Modeling of
       Operational State Data draft  . . . . . . . . . . . . . . . .   9
     7.1.  Addressing requirement 3: 'To interact with both intended
           and applied configuration'  . . . . . . . . . . . . . . .   9
     7.2.  Addressing requirement 4.1: Applied config as part of
           operational state . . . . . . . . . . . . . . . . . . . .  10
     7.3.  Addressing requirement 4.2: Support for both
           transactional, synchronous management systems as well as
           distributed, asynchronous management systems  . . . . . .  10
     7.4.  Addressing requirement 4.3: Separation of configuration
           and operational state data; ability to retrieve them
           independently . . . . . . . . . . . . . . . . . . . . . .  11
     7.5.  Addressing requirement 4.4: Ability to retreive
           operational state corresponding only to derived values,
           statistics, etc . . . . . . . . . . . . . . . . . . . . .  11
     7.6.  Addressing requirement 4.5: Consistent schema locations
           for configuration and corresponding operational state
           data  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12



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   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  12
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Appendix A.  Encoding examples for NETCONF and RESTCONF . . . . .  13
     A.1.  NETCONF get-config request using with-config-state with
           all-cfg option  . . . . . . . . . . . . . . . . . . . . .  14
     A.2.  NETCONF get-config request using with-config-state with
           diff-cfg-only option  . . . . . . . . . . . . . . . . . .  16
     A.3.  NETCONF get-config request using with-config-state with
           applied-cfg-only option . . . . . . . . . . . . . . . . .  18
     A.4.  RESTCONF GET request using with-config-state with all-cfg
           option (JSON) . . . . . . . . . . . . . . . . . . . . . .  20
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   The Consistent Modeling of Operational State Data Internet Draft
   [I-D.openconfig-netmod-opstate] sets out a number of operational
   requirements and proposed solutions for handling intended and applied
   config state when using YANG models.  This document sets out a
   possible alternative solution for some of those requirements.

   The solution proposed in this document does not require any changes
   to any existing YANG modules to support intended and applied config
   state.  In particular: the proposed solution does not require the
   data models to be explicitly modelled with separate configuration and
   operational containers, and it does not require that all
   configuration and operational state nodes and leaves to be defined as
   groupings.

   Nor does the proposed solution make explicit use of separate
   datastores to model intended configuration separately from applied
   configuration.

   Instead, the solution proposed here is a method for generating an
   enhanced schema based on any YANG model that is optionally used by
   network management protocols.  This enhanced schema includes up to
   four data leaves for each configuration node defined in the YANG
   model.  These cover both the intended and applied values, along with
   an additional reason code and message if the applied configuration
   does not match the intended configuration.

   Although the solution described here is only defined in the context
   of NETCONF and RESTCONF, it should be possible to extend the same
   YANG config data encoding mechanism to other protocol schemes used to
   access YANG data if required.



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1.1.  Change history

   The only change from draft version 00 is to fix a couple of mistakes
   in the example YANG module.

1.2.  Terminology

   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 RFC 2119 [RFC2119].

   The following terms are defined in Consistent Modeling of Operational
   State Data Internet Draft [I-D.openconfig-netmod-opstate], and
   reproduced here for convenience.

      intended configuration - this data represents the state that the
      network operator intends the system to be in.  This data is
      colloquially referred to as the 'configuration' of the system.

      applied configuration - this data represets the state that the
      network element is actually in, i.e. that which is currently being
      run by particular software modules (e.g. the BGP daemon), or other
      systems within the device (e.g. a secondary control-plane, or line
      card).

      derived state - this data represents information which is
      generated as part of the system's own interactions.  For example,
      derived state may consist of the results of protocol interactions
      (such as the negotiated duplex state of an Ethernet link),
      statistics (such as message queue depth), or counters (such as
      packet input or output bytes).

   The following additional terms are used in this document:

      operational nodes - this term is colloquially used in this draft
      to refer to "config false" YANG nodes.

2.  Objectives

   The aim of this draft is to provide a partial alternative solution to
   the requirements set out in Consistent Modeling of Operational State
   Data Internet Draft [I-D.openconfig-netmod-opstate].  An explanation
   of how the specific requirements are addressed is described in
   Section 7.







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3.  "With-config-state" encoding scheme

   The solution proposed in this document makes use of a new encoding
   scheme that is used to represent YANG configuration nodes in NETCONF
   and RESTCONF.  An optional parameter, called <with-config-state> and
   defined below, indicates when this new encoding scheme is used.

   When the with-config-state option is used each YANG configuration
   leaf in the datastore is returned in a different format.  Rather than
   being encoded as an XML or JSON leaf element that holds the
   configured value, it is instead returned as a node element, with the
   same name as the YANG config leaf, that contains up to four separate
   leaf elements.  The four leaf elements that the node may contain are
   'cfg-intended', 'cfg-applied', 'cfg-status', and 'cfg-status-reason'.
   Theses leaves are externally addressable through using the full path
   of the leaf, providing explicit distinct paths for intended
   configuration vs applied configuration.  These elements are described
   in more detail in the following sub-sections.  Concrete examples of
   the encoding for NETCONF and RESTCONF requests are given in
   Appendix A.

3.1.  cfg-intended

   The cfg-intended leaf represents the intended configuration of the
   device, and is of the same datatype and holds the same value as the
   normal YANG data model configuration leaf.  The cfg-intended leaf is
   only present if the associated configuration node exists in the YANG
   data model.

   The cfg-intended leaf is semantically equivalent to the config leaf
   in the YANG data model that is based on, and hence is logically read/
   writable.  In particular, when the <with-config-state> parameter is
   used, management requests to modify the configuration may also use
   the full path to the cfg-intended leaf.  The server semantics for
   writing to the cfg-intended leaf are exactly the same as for writing
   to the standard YANG config node path - the flexibility is provided
   as a convenience to the NMS client.

3.2.  cfg-applied

   The cfg-applied leaf represents the applied configuration, and is of
   the same datatype as a normal YANG data model configuration leaf.  If
   there is no configuration currently in effect then the cfg-applied
   leaf is not present.

   The cfg-applied leaf is read only.

   To give some examples:



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      If the configuration has been successfully applied then the cfg-
      applied leaf would exactly match the cfg-intended leaf.

      If a new item of configuration is in the process of being applied
      then the cfg-intended leaf holds the intended configuration value,
      and the cfg-applied leaf would not be present until the
      configuration is in effect.

      If an existing item of configuration is in the process of being
      deleted then the cfg-applied leaf would hold the current
      configuration value, and the cfg-intended leaf would not be
      present.  Once the delete operation has completed, the
      configuration node element itself would logically be deleted.

      If the configuration value of an existing item of configuration is
      in the process of being changed, then the cfg-intended leaf would
      hold the new proposed value, and the cfg-applied leaf would hold
      the existing value that is currently in effect.

3.3.  cfg-status

   The cfg-status leaf is used, when required, to indicate why the value
   of the cfg-applied leaf does not match the value of the cfg-intended
   leaf.  It is only present when the values of the cfg-intended and
   cfg-applied leaves do not match.

   The cfg-status leaf is read only.

   The cfg-status leaf can take one of following values:

      in-progress - the config operation is in the process of being
      applied.

      waiting - the config operation is waiting for other configuration
      to be applied or hardware to be available before it can be
      applied.  Additional specific information may be provided in the
      cfg-status-reason leaf.

      failed - the config operation failed to be applied.  Additional
      information may be provided in the cfg-status-reason leaf to
      indicate the reason for the failure.

3.4.  cfg-status-reason

   The cfg-status-reason leaf may be used to provide additional
   information as to why the value of the cfg-applied leaf does not
   match the value of the cfg-intended leaf.




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   The cfg-status-reason leaf may only be present in the case that the
   cfg-status leaf is present and is set to either waiting or failed.

   The cfg-status-reason leaf is read only.

3.5.  Non-leaf config nodes

   Non-leaf config nodes require some special handling.  In particular,
   containers with presence and list elements must be considered.

   The proposed solution for both types of node is the same.  The cfg-
   intended, cfg-applied, cfg-status, and cfg-status-reason leaf nodes
   are implicitly added as direct descendants of the presence-container
   or list element.

   Note: There is an open issue that using these leaves directly opens
   up a potential naming clash between the "cfg-*" names above and
   existing explicitly defined child nodes in the YANG module
   definition.  There are a few possible ways that this might be
   addressed:

      Making the four "cfg-*" leaves reserved names.  I.e. to ensure
      that they are not used in general YANG modules.

      By inserting an implicit node between all child nodes under the
      container or list element.  This would automatically ensure that
      there can be no naming clash between the defined YANG nodes and
      the implicitly added "cfg-*" leaves.

      By using a reserved namespace for the "cfg-*" leaves to ensure
      that they cannot clash with any explicitly defined in the YANG
      module.

4.  Retrieval of intended and applied configuration

   To make use of the new encoding scheme defined above, this document
   defines a new parameter, called <with-config-state>, which can be
   added to specific NETCONF operation request messages, or as a
   RESTCONF query parameter, to control how retrieval of configuration
   nodes is treated by the server.

   The <with-config-state> parameter is supported for the following
   NETCONF operations: <get>, <get-config>, <edit-config>, <delete-
   config>.

   The <with-config-state> query parameter is supported for the
   following RESTCONF operations: GET, PUT, POST, PATCH, DELETE.




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   Use of the <with-config-state> parameter ensures that all config
   nodes are always returned using the defined encoding.  It also allows
   servers to explicitly reference the cfg-* leaves in requests and
   updates.

   A server that implements this specification MUST accept the <with-
   config-state> parameter containing the enumeration for any of the
   with-config-state modes it supports.  The <with-config-state>
   parameter contains one of the four enumerated values defined in this
   section.

4.1.  all-cfg

   When data is retrieved with a <with-config-state> parameter equal to
   'all-cfg', all 'cfg-*' nodes are reported using the encoding scheme
   defined in Section 3.

4.2.  intended-cfg-only

   When data is retrieved with a <with-config-state> parameter equal to
   'intended-cfg', only the 'cfg-intended' leaves are reported using the
   encoding scheme defined in Section 3.  All other 'cfg-*' leaves are
   omitted.

4.3.  applied-cfg-only

   When data is retrieved with a <with-config-state> parameter equal to
   'applied-cfg-only', only the 'cfg-applied' leaves are reported using
   the encoding scheme defined in Section 3.  All other 'cfg-*' leaves
   are omitted.

4.4.  diff-cfg-only

   When data is retrieved with a <with-config-state> parameter equal to
   'diff-cfg-only', config nodes are only returned if the value of the
   cfg-intended leaf does not match the value of the cfg-applied leaf.
   If the config node is returned then all appropriate 'cfg-*' leaves
   are returned as per the encoding scheme defined in Section 3.

5.  "With-config-state" Capability

5.1.  Overview

   The :with-config-state capability indicates whether a server supports
   the with-config-state functionality.  For a server that indicates
   support for the :with-config-state capability it must support at
   least the 'all-cfg' option.  It may also indicate support for the
   additional with-config-state retrieval modes.



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5.2.  Dependencies

   None

5.3.  Capability Identifier

   urn:ietf:params:netconf:capability:with-config-state:1.0

   The identifer has a paramater: "also-supported".  This parameter
   indicates which additional enumeration values (besides 'all-cfg') the
   server will accept for the <with-config-state> parameter in
   Section 4.  The value of the parameter is a comma-separated list of
   one or more modes that are supported.  Possible modes are 'intended-
   cfg-only', 'applied-cfg-only', 'diff-cfg-only' as defined in
   Section 4.

6.  Suggested layout of data models

   Generally, to ensure that operational data and configuration data can
   be easily related, this draft recommends that configuration and
   associated operational nodes be co-located in the same YANG
   container.  More precisely, YANG clients should be able to assume
   that configuration and operational nodes within the same container
   are implicitly related.

7.  Addressing the requirements of the Consistent Modeling of
    Operational State Data draft

7.1.  Addressing requirement 3: 'To interact with both intended and
      applied configuration'

   The proposed solution in this draft provides a way for a NMS to
   explicitly access both the intended and applied configuration state
   of configuration nodes.  It also provides a convenient way that both
   the intended and applied configuration values can be returned and
   easily compared.  It also has the following additional benefits:

      It optionally provides additional information as to why the
      applied configuration does not match the intended configuration.

      It does not force the YANG modules to use groupings for
      configuration data so that it can be mirrored in the operational
      state.  In particular, it places no burden to support an eventual
      consistency configuration model on YANG modules that do not need
      to operate in that environment.






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      The <with-config-state> parameter in the extension allows the
      client to request that only configuration nodes that are not in
      the intended state are returned.

   This draft also addresses the issue of allowing a NMS to easily
   relate configuration and operational state.  As should be clear the
   relationship between cfg-intended and cfg-applied states for a
   particular node are trivially and efficiently mappable for all YANG
   configuration nodes.  With the exception of interface operational
   state, that is not addressed by this draft, the relationship between
   configuration and derived state is acheived through the convention
   that co-located configuration and operational state be held in the
   same YANG container.  This is semantically similar to the approach in
   Consistent Modeling of Operational State Data Internet Draft
   [I-D.openconfig-netmod-opstate] that implicitly binds the contents of
   the 'config' and 'state' YANG container nodes together if they are
   rooted to the same parent YANG container.

7.2.  Addressing requirement 4.1: Applied config as part of operational
      state

   This requirement is met through the use of the separate cfg-intended
   and cfg-applied implict leaf nodes that are available when using the
   <with-config-state> extension parameter set to 'intended-cfg-only' or
   'applied-cfg-only' with either the NETCONF <get-config> operation or
   the RESTCONF GET request with the 'content' query parameter set to
   'config'.

7.3.  Addressing requirement 4.2: Support for both transactional,
      synchronous management systems as well as distributed,
      asynchronous management systems

   Devices that only support a transactional sychronous management
   system have the choice of either not supporting the <with-config-
   state> extension, or alternatively may achieve compliance with this
   extension fairly easily by returning the same value for both cfg-
   intended and cfg-applied leaf nodes, and always omitting the cfg-
   status and cfg-status-reason leaves.  Any requests using the path to
   the cfg-intended and cfg-applied leaves can be mapped back to the
   base config leaf defined in the YANG data model.  Any explicit
   requests get or get-config requests for cfg-status and cfg-status-
   reason can be rejected.

   Devices that support an asynchronous configuration system would
   implement support for the extension and provide the cfg-* leaves
   defined in this draft when requested.





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7.4.  Addressing requirement 4.3: Separation of configuration and
      operational state data; ability to retrieve them independently

   The first point is addressed by the proposed solution.  Config and
   operational data are already split, and the naming of the cfg-
   intended vs cfg-applied leaves provides a clear distinction between
   intended configuration, applied configuration, and derived state.

   The second point is not fully addressed by this draft.  The proposed
   protocol extension allows for just the intended config vs applied
   config nodes to be returned.  RESTCONF already supports querying
   config separately from operational state through use of the 'content'
   query paremeter.  A separate NETCONF protocol extension would be
   required to return just the operational nodes without any of the
   configuration nodes, such as the <get-state> enhancement described in
   Operational State Enhancements for YANG, NETCONF, and RESTCONF
   [I-D.kwatsen-netmod-opstate].

7.5.  Addressing requirement 4.4: Ability to retreive operational state
      corresponding only to derived values, statistics, etc

   Not directly addressed by this draft.  RESTCONF already supports
   querying config separately from operational state through use of the
   'content' query paremeter.  A separate NETCONF protocol extension
   would be required to return just the operational nodes without any of
   the configuration nodes, such as the <get-state> enhancement
   described in Operational State Enhancements for YANG, NETCONF, and
   RESTCONF [I-D.kwatsen-netmod-opstate].

7.6.  Addressing requirement 4.5: Consistent schema locations for
      configuration and corresponding operational state data

   Section 4.5 of Consistent Modeling of Operational State Data Internet
   Draft [I-D.openconfig-netmod-opstate] indicates that it is desirable
   to have a well defined path to retrieve the cfg-intended vs cfg-
   applied values to avoid requiring external context when referencing
   that information.  This is achieved by allowing paths in the NETCONF
   and RESTCONF protocols to include one of the cfg-state leaves when
   using the <with-config-state> extension.  E.g. if the path to a
   particular config leaf was normally /..path-to-leaf../cfg-leaf then
   the intended config value could be referenced and obtained by using
   /..path-to-leaf../cfg-leaf/cfg-intended.  The cfg-applied, cfg-
   status, and cfg-status-reason leaves can all be referenced and
   accessed in a similar fashion.

   Containers with presence are not leaf nodes, and hence require
   slightly differently handling to configuration leaf nodes.  The
   proposed solution is that containers with presence contain the cfg-



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   intended, cfg-applied, cfg-status, and cfg-status-reason leaf nodes
   as direct descendants of the container node and hence can be accessed
   using the same scheme as for config leaves.  E.g. if the path to a
   particular container with presence was normally /..path-to-p-
   container../cfg-p-container/ then the intended config value could be
   referenced and obtained by using /..path-to-p-container../cfg-p-
   container/cfg-intended.  The cfg-applied, cfg-status, and cfg-status-
   reason leaves can all be referenced and accessed in a similar
   fashion.

8.  Acknowledgements

   The authors wish to thank Einar Nilsen-Nygaard, Neil Ketley, Peyman
   Owladi for their helpful comments, ideas and expertise contributing
   to this draft.

9.  IANA Considerations

   TBD.  This document would at least need to register a new capability
   identifier URN in the 'Network Configuration Protocol (NETCONF)
   Capability URNs' registry for the with-config-state optional
   capability.'".

10.  Security Considerations

   The proposal in this document does not have any security
   considerations beyond the existing NETCONF/RESTCONF/YANG security
   considerations.

11.  References

11.1.  Normative References

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-08 (work in
              progress), October 2015.

   [I-D.openconfig-netmod-opstate]
              Shakir, R., Shaikh, A., and M. Hines, "Consistent Modeling
              of Operational State Data in YANG", draft-openconfig-
              netmod-opstate-01 (work in progress), July 2015.

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




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   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC6243]  Bierman, A. and B. Lengyel, "With-defaults Capability for
              NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011,
              <http://www.rfc-editor.org/info/rfc6243>.

11.2.  Informative References

   [I-D.kwatsen-netmod-opstate]
              Watsen, K., Bierman, A., Bjorklund, M., and J.
              Schoenwaelder, "Operational State Enhancements for YANG,
              NETCONF, and RESTCONF", draft-kwatsen-netmod-opstate-00
              (work in progress), September 2015.

Appendix A.  Encoding examples for NETCONF and RESTCONF

   A sample encoding of the <with-config-state> enhancement is described
   below.

   A simple example module is provided to illustrate the subsequent
   examples.  This is not a real module, and is not intended for any
   real use.





















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   module example-interfaces {

     namespace "http://example.com/ns/interfaces";

     prefix exam;

     container interfaces {
       description "Example interfaces group";

       list interface {
         key name;
         description "Example interface entry";

         leaf name {
           type string {
             length "1 .. max";
           }
           description
             "The administrative name of the interface.";
         }

         leaf mtu {
           type uint32;
           default 1514;
           description
             "The maximum transmission unit (MTU) value assigned to
              this interface.";
         }
       }
     }
   }

A.1.  NETCONF get-config request using with-config-state with all-cfg
      option

   A get-config request is made for the interfaces subtree using the
   <with-config-state> enhancement and 'all-cfg' option that returns all
   config nodes with explicit cfg-intended and cfg-applied leaves, and
   cfg-status and cfg-status-reason leaves when appropriate.

   In this example, at the time of processing the get-config request,
   the NETCONF server is also asynchronously processing a request to set
   the MTU leaf to 9000 for 4 interface config nodes.








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<rpc message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <get-config>
    <filter type="subtree">
      <interfaces xmlns="http://example.com/ns/interfaces"/>
    </filter>
    <with-config-state
     xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-config-state">
      all-cfg
    </with-config-state>
  </get>
</rpc>

   The response indicates that at the time of the reply:

      The request to set the MTU leaf on eth0/0 to 9000 has completed.

      The request to change the MTU leaf on eth0/1 from 2000 to 9000 is
      in progress.

      The request to set the MTU leaf on eth0/2 to 9000 is in progress.

      The request to set the MTU leaf on eth1/0 to 9000 is blocked
      because the necessary hardware is not present.

   <rpc-reply message-id="101"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <interfaces xmlns="http://example.com/ns/interfaces">
         <interface>
           <cfg-intended/>
           <cfg-actual/>
           <name>
             <cfg-intended>eth0/0</cfg-intended>
             <cfg-actual>eth0/0</cfg-actual>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-actual>9000</cfg-actual>
           </mtu>
         </interface>
         <interface>
           <cfg-intended/>
           <cfg-actual/>
           <name>
             <cfg-intended>eth0/1</cfg-intended>
             <cfg-actual>eth0/1</cfg-actual>
           </name>



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           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-actual>2000</cfg-actual>
             <cfg-status>in-progress</cfg-status>
           </mtu>
         </interface>
         <interface>
           <cfg-intended/>
           <cfg-actual/>
           <name>
             <cfg-intended>eth0/2</cfg-intended>
             <cfg-actual>eth0/2</cfg-actual>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-status>in-progress</cfg-status>
           </mtu>
         </interface>
         <interface>
           <cfg-intended/>
           <cfg-status>waiting</cfg-status>
           <cfg-status-reason>Linecard 1 is not available
           </cfg-status-reason>
           <name>
             <cfg-intended>eth1/0</cfg-intended>
             <cfg-status>waiting</cfg-status>
             <cfg-status-reason>Linecard 1 is not available
             </cfg-status-reason>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-status>waiting</cfg-status>
             <cfg-status-reason>Linecard 1 is not available
             </cfg-status-reason>
           </mtu>
         </interface>
       </interfaces>
     </data>
   </rpc-reply>

A.2.  NETCONF get-config request using with-config-state with diff-cfg-
      only option

   A get-config request is made for the interfaces subtree using the
   <with-config-state> enhancement and 'diff-cfg-only' option that only
   returns nodes where the cfg-intended node does not match the cfg-
   applied node.  Appropriate parent nodes are also returned.




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   As per the previous examples, at the time of processing the get-
   config request, the NETCONF server is also asynchronously processing
   a request to set the MTU leaf to 9000 for 4 interface config nodes.

<rpc message-id="102"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <get-config>
    <filter type="subtree">
      <interfaces xmlns="http://example.com/ns/interfaces"/>
    </filter>
    <with-config-state
     xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-config-state">
      diff-cfg-only
    </with-config-state>
  </get>
</rpc>

   The response indicates that the outstanding configuration requests
   still to be processed are:

      The request to change the MTU leaf on eth0/1 from 2000 to 9000 is
      in progress.

      The request to set the MTU leaf on eth0/2 to 9000 is in progress.

      The request to set the MTU leaf on eth1/0 to 9000 is blocked
      because the necessary hardware is not present.

   <rpc-reply message-id="102"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <interfaces xmlns="http://example.com/ns/interfaces">
         <interface>
           <cfg-intended/>
           <cfg-actual/>
           <name>
             <cfg-intended>eth0/1</cfg-intended>
             <cfg-actual>eth0/1</cfg-actual>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-actual>2000</cfg-actual>
             <cfg-status>in-progress</cfg-status>
           </mtu>
         </interface>
         <interface>
           <cfg-intended/>
           <cfg-actual/>



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           <name>
             <cfg-intended>eth0/2</cfg-intended>
             <cfg-actual>eth0/2</cfg-actual>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-status>in-progress</cfg-status>
           </mtu>
         </interface>
         <interface>
           <cfg-intended/>
           <cfg-status>waiting</cfg-status>
           <cfg-status-reason>Linecard 1 is not available
           </cfg-status-reason>
           <name>
             <cfg-intended>eth1/0</cfg-intended>
             <cfg-status>waiting</cfg-status>
             <cfg-status-reason>Linecard 1 is not available
             </cfg-status-reason>
           </name>
           <mtu>
             <cfg-intended>9000</cfg-intended>
             <cfg-status>waiting</cfg-status>
             <cfg-status-reason>Linecard 1 is not available
             </cfg-status-reason>
           </mtu>
         </interface>
       </interfaces>
     </data>
   </rpc-reply>

A.3.  NETCONF get-config request using with-config-state with applied-
      cfg-only option

   A get-config request is made for the interfaces subtree using the
   <with-config-state> enhancement and 'applied-cfg-only' option that
   only returns the currently applied configuration.

   As per the previous examples, At the time of processing the get-
   config request, the NETCONF server is also asynchronously processing
   a request to set the MTU leaf to 9000 for 4 interface config nodes.










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<rpc message-id="103"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <get-config>
    <filter type="subtree">
      <interfaces xmlns="http://example.com/ns/interfaces"/>
    </filter>
    <with-config-state
     xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-config-state">
      applied-cfg-only
    </with-config-state>
  </get>
</rpc>

   The response indicates that the current applied configuration of the
   selected nodes is:

      The MTU leaf of eth0/0 is 9000.

      The MTU leaf of eth0/1 is 2000.

      Eth0/2 has no MTU leaf applied.

      [Implicitly - there is no applied configuration for Eth1/0 since
      the hardware is not present.]



























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   <rpc-reply message-id="103"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <interfaces xmlns="http://example.com/ns/interfaces">
         <interface>
           <cfg-actual/>
           <name>
             <cfg-actual>eth0/0</cfg-actual>
           </name>
           <mtu>
             <cfg-actual>9000</cfg-actual>
           </mtu>
         </interface>
         <interface>
           <cfg-actual/>
           <name>
             <cfg-actual>eth0/1</cfg-actual>
           </name>
           <mtu>
             <cfg-actual>2000</cfg-actual>
           </mtu>
         </interface>
         <interface>
           <cfg-actual/>
           <name>
             <cfg-actual>eth0/2</cfg-actual>
           </name>
         </interface>
       </interfaces>
     </data>
   </rpc-reply>

A.4.  RESTCONF GET request using with-config-state with all-cfg option
      (JSON)

   An equivalent RESTCONF/JSON example to Appendix A.1 is provided to
   illustrate the equivalent JSON encoding.

   A REST GET request is made for all config data using the <with-
   config-state> enhancement and 'all-cfg' option that all returns all
   config nodes with explicit cfg-intended and cfg-applied leaves.

   In this example, at the time of processing the GET request, the
   RESTCONF server is also asynchronously processing a request to set
   the MTU leaf to 9000 for 4 interface config nodes.






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GET /restconf/data/example-events:events?content=config&with-config-state=all-cfg
  HTTP/1.1
Host: example.com
Accept: application/yang.data+json

   As per Appendix A.1, the response indicates that at the time of the
   reply:

      The request to set the MTU leaf on eth0/0 to 9000 has completed.

      The request to change the MTU leaf on eth0/1 from 2000 to 9000 is
      in progress.

      The request to set the MTU leaf on eth0/2 to 9000 is in progress.

      The request to set the MTU leaf on eth1/0 to 9000 is blocked
      because the necessary hardware is not present.

   HTTP/1.1 200 OK
   Date: Mon, 1 Apr 2015 04:01:00 GMT
   Server: example-server
   Content-Type: application/yang.data+json

   {
   "example:interfaces": [
     {
       "cfg-intended" = null,
       "cfg-actual" = null,
       "name" : {
         "cfg-intended" = "eth0/0",
         "cfg-actual" = "eth0/0"
       },
       "mtu" : {
         "cfg-intended" = 9000,
         "cfg-actual" = 9000
       },
     },
     {
       "cfg-intended" = null,
       "cfg-actual" = null,
       "name" : {
         "cfg-intended" = "eth0/1",
         "cfg-actual" = "eth0/1"
       },
       "mtu" : {
         "cfg-intended" = 9000,
         "cfg-actual" = 2000,
         "cfg-status" = "in-progress"



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       },
     },
     {
       "cfg-intended" = null,
       "cfg-actual" = null,
       "name" : {
         "cfg-intended" = "eth0/2",
         "cfg-actual" = "eth0/2"
       },
       "mtu" : {
         "cfg-intended" = 9000,
         "cfg-status" = "in-progress"
       },
     },
     {
       "cfg-intended" = null,
       "cfg-status" = "waiting",
       "cfg-status-reason" = "Linecard 1 is not available",
       "name" : {
         "cfg-intended" = "eth1/0",
         "cfg-status" = "waiting",
         "cfg-status-reason" = "Linecard 1 is not available",
       },
       "mtu" : {
         "cfg-intended" = 9000,
         "cfg-status" = "waiting",
         "cfg-status-reason" = "Linecard 1 is not available",
       },
     },
   ]
   }

Author's Address

   Robert Wilton
   Cisco Systems

   Email: rwilton@cisco.com













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