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Versions: (draft-bierman-netconf-with-defaults) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 6243

NETCONF                                                       A. Bierman
Internet-Draft                                                   Brocade
Intended status: Standards Track                              B. Lengyel
Expires: April 17, 2011                                         Ericsson
                                                        October 14, 2010


                  With-defaults capability for NETCONF
                  draft-ietf-netconf-with-defaults-12

Abstract

   The NETCONF protocol defines ways to read and edit configuration data
   from a NETCONF server.  In some cases, part of this data may not be
   set by the NETCONF client, but rather a default value known to the
   server is used instead.  In many situations the NETCONF client has a
   priori knowledge about default data, so the NETCONF server does not
   need to save it in a NETCONF configuration datastore or send it to
   the client in a retrieval operation reply.  In other situations the
   NETCONF client will need this data from the server.  Not all server
   implementations treat this default data the same way.  This document
   defines a capability-based extension to the NETCONF protocol that
   allows the NETCONF client to identify how defaults are processed by
   the server, and also defines new mechanisms for client control of
   server processing of default 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 April 17, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Defaults Handling Behavior . . . . . . . . . . . . . . . .  5
     1.3.  Client Controlled Retrieval of Default Data  . . . . . . .  5
   2.  Defaults Handling Basic Modes  . . . . . . . . . . . . . . . .  6
     2.1.  'report-all' Basic Mode  . . . . . . . . . . . . . . . . .  6
       2.1.1.  'report-all' Basic Mode Retrieval  . . . . . . . . . .  7
       2.1.2.  'report-all' <with-defaults> Retrieval . . . . . . . .  7
       2.1.3.  'report-all' <edit-config> and <copy-config>
               Behavior . . . . . . . . . . . . . . . . . . . . . . .  7
     2.2.  'trim' Basic Mode  . . . . . . . . . . . . . . . . . . . .  7
       2.2.1.  'trim' Basic Mode Retrieval  . . . . . . . . . . . . .  7
       2.2.2.  'trim' <with-defaults> Retrieval . . . . . . . . . . .  7
       2.2.3.  'trim' <edit-config> and <copy-config> Behavior  . . .  8
     2.3.  'explicit' Basic Mode  . . . . . . . . . . . . . . . . . .  8
       2.3.1.  'explicit' Basic Mode Retrieval  . . . . . . . . . . .  8
       2.3.2.  'explicit' <with-defaults> Retrieval . . . . . . . . .  8
       2.3.3.  'explicit' <edit-config> and <copy-config> Behavior  .  8
   3.  Retrieval of Default Data  . . . . . . . . . . . . . . . . . .  9
     3.1.  'report-all' Retrieval Mode  . . . . . . . . . . . . . . .  9
     3.2.  'trim' Retrieval Mode  . . . . . . . . . . . . . . . . . .  9
     3.3.  'explicit' Retrieval Mode  . . . . . . . . . . . . . . . .  9
     3.4.  'report-all-tagged' Retrieval Mode . . . . . . . . . . . . 10
   4.  With-defaults Capability . . . . . . . . . . . . . . . . . . . 10
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . . 10
     4.3.  Conformance  . . . . . . . . . . . . . . . . . . . . . . . 11
     4.4.  Capability Identifier  . . . . . . . . . . . . . . . . . . 11
     4.5.  New Operations . . . . . . . . . . . . . . . . . . . . . . 11
     4.6.  Modifications to Existing Operations . . . . . . . . . . . 11
       4.6.1.  <get>, <get-config>, and <copy-config> Operations  . . 11
       4.6.2.  <edit-config> Operation  . . . . . . . . . . . . . . . 13
       4.6.3.  Other Operations . . . . . . . . . . . . . . . . . . . 13
     4.7.  Interactions with Other Capabilities . . . . . . . . . . . 14
   5.  YANG Module for the <with-defaults> Parameter  . . . . . . . . 14



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   6.  XSD for the 'wd:default' Attribute . . . . . . . . . . . . . . 17
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
   10. Normative References . . . . . . . . . . . . . . . . . . . . . 19
   Appendix A.  Usage Examples  . . . . . . . . . . . . . . . . . . . 20
     A.1.  Example YANG Module  . . . . . . . . . . . . . . . . . . . 20
     A.2.  Example Data Set . . . . . . . . . . . . . . . . . . . . . 22
     A.3.  Protocol Operation Examples  . . . . . . . . . . . . . . . 23
       A.3.1.  <with-defaults> = 'report-all' . . . . . . . . . . . . 23
       A.3.2.  <with-defaults> = 'report-all-tagged'  . . . . . . . . 24
       A.3.3.  <with-defaults> = 'trim' . . . . . . . . . . . . . . . 27
       A.3.4.  <with-defaults> = 'explicit' . . . . . . . . . . . . . 28
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 29
     B.1.  11-12  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.2.  10-11  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.3.  09-10  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.4.  08-09  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.5.  07-08  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.6.  06-07  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     B.7.  05-06  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     B.8.  04-05  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     B.9.  03-04  . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     B.10. 02-03  . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     B.11. 01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     B.12. 00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     B.13. -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32























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1.  Introduction

   The NETCONF protocol [RFC4741] defines ways to read configuration and
   state data from a NETCONF server.  Part of the configuration data may
   not be set by the NETCONF client, but rather by a default value from
   the data model.  In many situations the NETCONF client has a priori
   knowledge about default data, so the NETCONF server does not need to
   send it to the client.  A priori knowledge can be obtained, e.g., a
   document formally describing the data models supported by the NETCONF
   server.

   It can be important for a client to know exactly how a server
   implementation will handle default data.  There are subtle
   differences in some protocol operations where the defaults handling
   behavior of the server will affect the outcome of the operation.

1.1.  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 [RFC2119].

   Data model schema:  A document or set of documents describing the
      data models supported by the NETCONF server.
   Management Application:  A computer program running outside the
      NETCONF server that configures or supervises the NETCONF server.
      A management application can reach the device e.g. via NETCONF,
      command line interface (CLI) or Simple Network Management Protocol
      (SNMP).
   Schema default data:  Data specified in the data model schema as
      default, that is set or used by the device whenever the NETCONF
      client or other management application/user does not provide a
      specific value for the relevant data node.  Schema default data
      may or may not be stored as part of a configuration datastore,
      depending on the basic mode used by a particular server.
   Default data:  Conceptual data containing a default value.  Default
      data is not kept in a datastore.  Not all servers use the same
      criteria to decide if a data node is actually instantiated in a
      datastore.  If a data node is not present in a datastore, and a
      schema default definition is in use by the server instead, then it
      is considered to be a default data node.
   Default value:  A default value is a value for a data node instance
      that is conceptually in use by the server, when the data node
      instance does not exist.







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   Explicitly set data:  Data that is set to any value by a NETCONF
      client or other management application by the way of an explicit
      management operation, including any data model schema default
      value.  Any value set by the NETCONF server which is not the
      schema defined default value is also considered explicitly set
      data.
   <with-defaults> retrieval:  Refers to a protocol operation which
      includes the <with-default> parameter to control the handling of
      default data.
   :with-defaults:  The shorthand notation for the with-defaults
      capability identifier.

   The following terms are defined in [RFC4741]:
   o  client
   o  datastore
   o  operation
   o  server

   The following term is defined in [RFC6020]:
   o  data node

1.2.  Defaults Handling Behavior

   The defaults handling behavior used by a server will impact NETCONF
   protocol operations in two ways:

   1.  Data retrieval: A server is normally allowed to exclude data
       nodes which it considers to contain the default value.  The
       actual nodes omitted depends on the defaults handling behavior
       used by the server.

   2.  Create and delete operations: The <edit-config> 'operation'
       attribute can be used to create and/or delete specific data
       nodes.  These operations depend on whether the target node
       currently exists or not.  The server's defaults handling behavior
       will determine whether the requested node currently exists in the
       configuration datastore or not.


1.3.  Client Controlled Retrieval of Default Data

   A networking device may have a large number of default values.  Often
   the default values are specifically defined with a reasonable value,
   documented and well-known, so that the management user does not need
   to handle them.  For these reasons it is quite common for networking
   devices to suppress the output of parameters having the default
   value.




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   However, there are use-cases when a NETCONF client will need the
   default data from the server:

   o  The management application often needs a single, definitive and
      complete set of configuration values that determine how the
      networking device works.
   o  Documentation about default values can be unreliable or
      unavailable.
   o  Some management applications might not have the capabilities to
      correctly parse and interpret formal data models.
   o  Human users might want to understand the received data without
      consultation of the documentation.

   In all these cases, the NETCONF client will need a mechanism to
   retrieve default data from a NETCONF server.

   This document defines a NETCONF protocol capability to identify the
   server defaults handling behavior, an XML attribute to identify
   default data, and a YANG module extension to the NETCONF protocol
   that allows the NETCONF client to control whether default data is
   returned by the server.


2.  Defaults Handling Basic Modes

   Not all server implementations treat default data in the same way.
   Instead of forcing a single implementation strategy, this document
   allows a server to advertise a particular style of defaults handling,
   and the client can adjust accordingly.

   NETCONF servers report default data in different ways.  This document
   specifies three standard defaults handling basic modes that a server
   implementor may choose from:

   o  report-all
   o  trim
   o  explicit

   A server MUST select one of the three basic modes defined in this
   section for handling default data.

2.1.  'report-all' Basic Mode

   A server which uses the 'report-all' basic mode does not consider any
   data node to be default data, even schema default data.






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2.1.1.  'report-all' Basic Mode Retrieval

   When data is retrieved from a server using the 'report-all' basic
   mode, and the <with-defaults> parameter is not present, all data
   nodes MUST be reported.

2.1.2.  'report-all' <with-defaults> Retrieval

   The server MUST support the <with-defaults> parameter with a value
   equal to 'report-all', as specified in Section 3.1.

2.1.3.  'report-all' <edit-config> and <copy-config> Behavior

   The server MUST consider every data node to exist, even those
   containing a schema default value.  A valid 'create' operation
   attribute for a data node that contains its schema default value MUST
   fail with a 'data-exists' error-tag.  A valid 'delete' operation
   attribute for a data node that contains its schema default value MUST
   succeed, even though the data node is immediately replaced by the
   server with the default value.

   A server which uses the 'report-all' basic-mode has no concept of a
   default node, so the 'report-all-tagged' <with-defaults> retrieval
   mode is not relevant.  There will never be any tagged nodes, since
   there are no nodes which are omitted in a basic-mode retrieval
   operation.  If the wd:default attribute is present in any
   configuration data, the server MUST return an <rpc-error> response
   with an 'unknown-attribute' error-tag.

2.2.  'trim' Basic Mode

   A server which uses the 'trim' basic mode MUST consider any data node
   set to its schema default value to be default data.

2.2.1.  'trim' Basic Mode Retrieval

   When data is retrieved from a server using the 'trim' basic mode, and
   the <with-defaults> parameter is not present, data nodes MUST NOT be
   reported if they contain the schema default value.  Non-configuration
   data nodes containing the schema default value MUST NOT be reported.

2.2.2.  'trim' <with-defaults> Retrieval

   The server MUST support the <with-defaults> parameter with a value
   equal to 'trim', as specified in Section 3.1.






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2.2.3.  'trim' <edit-config> and <copy-config> Behavior

   The server MUST consider any data node that does not contain its
   schema default value to exist.  A valid 'create' operation attribute
   for a data node that has a schema default value defined MUST succeed.
   A valid 'delete' operation attribute for a missing data node that has
   a schema default value MUST fail.  The server MUST return an <rpc-
   error> response with a 'data-missing' error-tag.

   If a client sets a data node to its schema default value, using any
   valid operation, it MUST succeed, although the data node MUST NOT be
   saved in the NETCONF configuration datastore.  This has the same
   effect as removing the data node and treating it as default data.

   If the server supports the 'report-all-tagged' value for the <with-
   defaults> parameter, then the 'wd:default' attribute MUST be accepted
   in configuration input, as described in Section 4.6.1 and
   Section 4.6.2.

2.3.  'explicit' Basic Mode

   A server which uses the 'explicit' basic mode MUST consider any data
   node that is not explicitly set data to be default data.

2.3.1.  'explicit' Basic Mode Retrieval

   If a client sets a data node to its schema default value, it MUST
   always be reported.  If the server sets a data node to its schema
   default value, it MUST NOT be reported.  Non-configuration data nodes
   containing the schema default value MUST be reported.

2.3.2.  'explicit' <with-defaults> Retrieval

   The server MUST support the <with-defaults> parameter with a value
   equal to 'explicit', as specified in Section 3.3.

2.3.3.  'explicit' <edit-config> and <copy-config> Behavior

   The server considers any data node that is explicitly set data to
   exist.  A valid 'create' operation attribute for a data node that has
   been set by a client to its schema default value MUST fail with a
   'data-exists' error-tag.  A valid 'create' operation attribute for a
   data node that has been set by the server to its schema default value
   MUST succeed.  A valid 'delete' operation attribute for a data node
   that has been set by a client to its schema default value MUST
   succeed.  A valid 'delete' operation attribute for a data node that
   has been set by the server to its schema default value MUST fail with
   a 'data-missing' error-tag.



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   If the server supports the 'report-all-tagged' retrieval mode in its
   :with-defaults capability, then the 'wd:default' attribute MUST be
   accepted in configuration input.  If all NETCONF <edit-config> or
   <copy-config> parameters are valid, then the server will treat a wd:
   default="true" tagged data node as a request to return that node to
   default data.  If this request is valid within the context of the
   requested NETCONF operation, then the data node is removed and
   returned to its default value.  The data node within the NETCONF
   message MUST contain a value in this case, which MUST be equal to the
   schema default value.  If not, the server MUST return an <rpc-error>
   response with a 'invalid-value' error-tag.


3.  Retrieval of Default Data

   This document defines a new parameter, called <with-defaults>, which
   can be added to specific NETCONF operation request messages to
   control how retrieval of default data is treated by the server.

   A server which implements this specification MUST accept the <with-
   defaults> parameter containing the enumeration for any of the
   defaults handling modes it supports.  The <with-defaults> parameter
   contains one of the four enumerations defined in this section.

3.1.  'report-all' Retrieval Mode

   When data is retrieved with a <with-defaults> parameter equal to
   'report-all', all data nodes MUST be reported, including any data
   nodes considered to be default data by the server.

3.2.  'trim' Retrieval Mode

   When data is retrieved with a <with-defaults> parameter equal to
   'trim', data nodes MUST NOT be reported if they contain the schema
   default value.  Non-configuration data nodes containing the schema
   default value MUST NOT be reported.

3.3.  'explicit' Retrieval Mode

   When data is retrieved with a <with-defaults> parameter equal to
   'explicit', a data node which was set by a client to its schema
   default value MUST be reported.  A conceptual data node which would
   be set by the server to the schema default value MUST NOT be
   reported.  Non-configuration data nodes containing the schema default
   value MUST be reported.






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3.4.  'report-all-tagged' Retrieval Mode

   In addition to the basic modes, a special variant of the 'report-all'
   basic mode is available called 'report-all-tagged'.  This mode MUST
   be supported on a server if the 'also-supported' parameter in the
   :with-defaults capability contains the 'report-all-tagged' option.
   Refer to Section 4 for encoding details for this capability.

   In this mode the server returns all data nodes, just like the
   'report-all' mode, except a data node that is considered by the
   server to contain default data will include an XML attribute to
   indicate this condition.  This is useful for an application to
   determine which nodes are considered to contain default data by the
   server, within a single retrieval operation.

   A server which supports 'report-all-tagged' MUST also accept the 'wd:
   default' XML attribute within configuration input to the <edit-
   config> or <copy-config> operations.  Refer to Section 6 for XML
   encoding details of the 'wd:default' XML attribute.


4.  With-defaults Capability

4.1.  Overview

   The :with-defaults capability indicates which defaults handling basic
   mode is supported by the server.  It may also indicate support for
   additional defaults retrieval modes.  These retrieval modes allow a
   NETCONF client to control whether default data is returned by the
   server.  The capability affects both configuration and state data
   (while acknowledging that the usage of default values for state data
   is less prevalent).  Sending of default data is controlled for each
   individual operation separately.

   A NETCONF server implementing the :with-defaults capability:

   o  MUST indicate its basic mode behavior by including the 'basic-
      mode' parameter in the capability URI, as defined in Section 4.4.
   o  MUST support the YANG module defined in Section 5.
   o  SHOULD support the 'report-all' or 'report-all-tagged' defaults
      handling mode.
   o  MAY support additional defaults handling modes.

4.2.  Dependencies

   None





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4.3.  Conformance

   Every NETCONF server SHOULD implement this capability.

4.4.  Capability Identifier

   urn:ietf:params:netconf:capability:with-defaults:1.0

   The identifier MUST have a parameter: "basic-mode".  This indicates
   how the server will treat default data, as defined in Section 2.  The
   allowed values of this parameter are 'report-all', 'trim', and
   'explicit', as defined in Section 2.

   The identifier MAY have another parameter: "also-supported".  This
   parameter indicates which additional default handling modes the
   server supports.  The value of the parameter is a comma separated
   list of one or more modes that are supported beside the mode
   indicated in the 'basic-mode' parameter.  Possible modes are 'report-
   all', 'report-all-tagged', 'trim', and 'explicit', as defined in
   Section 3.

   Note that this protocol capability URI is separate from the YANG
   module capability URI for the YANG module in Section 5.  A server
   which implements this module MUST also advertise a YANG module
   capability URI according to the rules specified in [RFC6020].

   Examples:

   urn:ietf:params:netconf:capability:with-defaults:1.0?basic-
   mode=explicit

   urn:ietf:params:netconf:capability:with-defaults:1.0?basic-
   mode=explicit&also-supported=report-all,report-all-tagged

4.5.  New Operations

   None

4.6.  Modifications to Existing Operations

4.6.1.  <get>, <get-config>, and <copy-config> Operations

   A new <with-defaults> XML element is added to the input for the
   <get>, <get-config> and <copy-config> operations.  If the <with-
   defaults> element is present, it controls the reporting of default
   data.  The server MUST return default data in the NETCONF <rpc-reply>
   messages according to the value of this element, if the server
   supports the specified retrieval mode.



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   This parameter only controls these specified retrieval operations,
   and does not impact any other operations or the non-volatile storage
   of configuration data.

   The <with-defaults> element is defined in the XML namespace for the
   ietf-netconf-with-defaults.yang module in Section 5, not the XML
   namespace for the <get>, <get-config> and <copy-config> operations.

   Allowed values of the with-defaults element are taken from the 'with-
   defaults-type' typedef in Section 5.  The allowed values for a
   particular server are restricted to the values that the server
   indicates it supports within the :with-defaults capability, in the
   'basic-mode' and 'also-supported' parameters.

   If an unsupported value is used, the NETCONF server MUST return an
   <rpc-error> response with an 'invalid-value' error-tag.

   If the <with-defaults> element is not present, the server MUST follow
   its basic mode behavior as indicated by the :with-defaults capability
   identifier's 'basic-mode' parameter, defined in Section 4.4.

   The <get> and <get-config> operations support a separate filtering
   mechanism, using the <filter> parameter.  The defaults filtering is
   conceptually done before the <filter> parameter is processed.  For
   example, if the <with-defaults> parameter is equal to 'report-all',
   then the <filter> parameter is conceptually applied to all data nodes
   and all default data.

   The <copy-config> operation is only affected by the <with-defaults>
   parameter if the target of the operation is specified with the <url>
   parameter.  If the target is a NETCONF configuration datastore (i.e.,
   running, candidate or startup), the <with-defaults> parameter has no
   effect.  The server MUST use its basic mode when copying data to a
   NETCONF configuration datastore.  If the <with-defaults> parameter is
   present in this case, it MUST be silently ignored by the server.

   If the server supports the 'report-all-tagged' mode, then the 'wd:
   default' attribute defined in Section 6 also impacts the <copy-
   config> operation.  If the wd:default attribute is present and set to
   'true', then the server MUST treat the new data node as a request to
   return that node to its default value (i.e., remove it from the
   configuration datastore).  The data node within the NETCONF message
   MUST contain a value in this case, which MUST be equal to the schema
   default value.  If not, the server MUST return an <rpc-error>
   response with a 'invalid-value' error-tag.






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4.6.2.  <edit-config> Operation

   The <edit-config> operation has several editing modes.  The 'create'
   and 'delete' editing operations are affected by the defaults handling
   basic mode.  The other enumeration values for the NETCONF operation
   attribute are not affected.

   If the operation attribute contains the value 'create', and the data
   node already exists in the target configuration datastore, then the
   server MUST return an <rpc-error> response with a 'invalid-value'
   error-tag.

   If the client sets a data node to its schema default value, the
   server MUST accept the request if it is valid.  The server MUST keep
   or discard the new value based on its defaults handling basic mode.
   For the 'trim' basic mode, all schema default values are discarded,
   otherwise a client-provided schema default value is saved in a
   NETCONF configuration datastore.

   If the server supports the 'report-all-tagged' mode, then the 'wd:
   default' attribute defined in Section 6 also impacts the <edit-
   config> operation.  If the wd:default attribute is present and set to
   'true', then the server MUST treat the new data node as a request to
   return that node to its default value (i.e., remove it from the
   configuration datastore).  The data node within the NETCONF message
   MUST contain a value in this case, which MUST be equal to the schema
   default value.  If not, the server MUST return an <rpc-error>
   response with a 'invalid-value' error-tag.

   If the wd:default attribute is present, then the effective operation
   for the target data node MUST be 'create', 'merge' or 'replace'.  If
   not, then the server MUST return an <rpc-error> response with an
   'invalid-value' error-tag.  For example, if 'create' is the effective
   operation, then the create request must be valid on its own (e.g.,
   current data node MUST NOT exist).  The procedure for determining the
   effective operation is defined in [I-D.ietf-netconf-4741bis].  It is
   derived from the 'default-operation' parameter and/or any operation
   attributes that are present in the data node or any of its ancestor
   nodes, within the <edit-config> request.

4.6.3.  Other Operations

   Other operations that return configuration data SHOULD also handle
   default data according to the rules set in this document, and
   explicitly state this in their documentation.  If this is not
   specified in the document defining the respective operation, the
   default handling rules described herein do not affect these
   operations.



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4.7.  Interactions with Other Capabilities

   None


5.  YANG Module for the <with-defaults> Parameter

   The following YANG module defines the addition of the with-defaults
   element to the <get>, <get-config>, and <copy-config> operations.
   The YANG language is defined in [RFC6020].  The above operations are
   defined in YANG in [I-D.ietf-netconf-4741bis].  Every NETCONF server
   which supports the :with-defaults capability MUST implement this YANG
   module.



 <CODE BEGINS> file="ietf-netconf-with-defaults@2010-06-09.yang"

 module ietf-netconf-with-defaults {

    namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults";

    prefix ncwd;

    import ietf-netconf { prefix nc; }

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

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

      WG Chair: Bert Wijnen
                <mailto:bertietf@bwijnen.net>

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

      Editor: Andy Bierman
              <mailto:andy.bierman@brocade.com>

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

    description
     "This module defines an extension to the NETCONF protocol
      that allows the NETCONF client to control how default



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      values are handled by the server in particular NETCONF operations.

      Copyright (c) 2010 IETF Trust and the persons identified as
      the document authors.  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-netmod-with-defaults-10.txt

    revision 2010-06-09 {
      description
        "Initial version.";
      reference
       "RFC XXXX: With-defaults capability for NETCONF";
    }
    // RFC Ed.: replace XXXX with actual
    // RFC number and remove this note

    typedef with-defaults-mode {
       description
         "Possible modes to report default data.";
       reference
          "RFC XXXX; section 3.";
          // RFC Ed.: replace XXXX with actual
          // RFC number and remove this note

       type enumeration {
          enum report-all {
              description
                "All default data is reported.";
              reference
                "RFC XXXX; section 3.1";
                // RFC Ed.: replace XXXX with actual
                // RFC number and remove this note

          }
          enum report-all-tagged {
              description



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                "All default data is reported.
                 Any nodes considered to be default data
                 will contain a 'wd:default' XML attribute,
                 set to 'true'.";
              reference
                "RFC XXXX; section 3.4";
                // RFC Ed.: replace XXXX with actual
                // RFC number and remove this note
          }
          enum trim {
              description
                "Values are not reported if they contain the default.";
              reference
                "RFC XXXX; section 3.2";
                // RFC Ed.: replace XXXX with actual
                // RFC number and remove this note

          }
          enum explicit {
              description
                "Report values that contain the definition of
                 explicitly set data.";
              reference
                "RFC XXXX; section 3.3";
                // RFC Ed.: replace XXXX with actual
                // RFC number and remove this note
          }
      }
    }

    grouping with-defaults-parameters {
      description
        "Contains the <with-defaults> parameter for control
         of defaults in NETCONF retrieval operations.";

      leaf with-defaults {
        description
          "The explicit defaults processing mode requested.";
        reference
          "RFC XXXX; section 4.6.1";
          // RFC Ed.: replace XXXX with actual
          // RFC number and remove this note

        type with-defaults-mode;
      }
    }

    // extending the get-config operation



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    augment /nc:get-config/nc:input {
        description
          "Adds the <with-defaults> parameter to the
           input of the NETCONF <get-config> operation.";
        reference
          "RFC XXXX; section 4.6.1";
          // RFC Ed.: replace XXXX with actual
          // RFC number and remove this note

        uses with-defaults-parameters;
    }

    // extending the get operation
    augment /nc:get/nc:input {
        description
          "Adds the <with-defaults> parameter to
           the input of the NETCONF <get> operation.";
        reference
          "RFC XXXX; section 4.6.1";
          // RFC Ed.: replace XXXX with actual
          // RFC number and remove this note

        uses with-defaults-parameters;
    }

    // extending the copy-config operation
    augment /nc:copy-config/nc:input {
        description
          "Adds the <with-defaults> parameter to
           the input of the NETCONF <copy-config> operation.";
        reference
          "RFC XXXX; section 4.6.1";
          // RFC Ed.: replace XXXX with actual
          // RFC number and remove this note

        uses with-defaults-parameters;
    }

 }

 <CODE ENDS>



6.  XSD for the 'wd:default' Attribute

   The following XML Schema document defines the 'default' attribute,
   described within this document.  This XSD is only relevant if the



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   server supports the 'report-all-tagged' defaults retrieval mode.



 <CODE BEGINS> file="defaults.xsd"

 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
            xmlns="urn:ietf:params:xml:ns:netconf:default:1.0"
            targetNamespace="urn:ietf:params:xml:ns:netconf:default:1.0"
            elementFormDefault="qualified"
            attributeFormDefault="unqualified"
            xml:lang="en">

   <xs:annotation>
     <xs:documentation>
       This schema defines the syntax for the 'default' attribute
       described within this document.
     </xs:documentation>
   </xs:annotation>

   <!--
     default attribute
     -->
   <xs:attribute name="default" type="xs:boolean" default="false">
     <xs:annotation>
       <xs:documentation>
         This attribute indicates whether the data node represented
         by the XML element containing this attribute is considered
         by the server to be default data.  If set to 'true' then
         the data node is default data.  If 'false', then the
         data node is not default data.
       </xs:documentation>
     </xs:annotation>
   </xs:attribute>

 </xs:schema>

 <CODE ENDS>


7.  IANA Considerations

   This document registers the following capability identifier URN in
   the 'Network Configuration Protocol Capability URNs registry':






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      urn:ietf:params:netconf:capability:with-defaults:1.0

   Note that the capability URN is compliant to [RFC4741] section 10.3.

   This document registers two XML namespace URNs in the 'IETF XML
   registry', following the format defined in [RFC3688].

      URI: urn:ietf:params:xml:ns:netconf:default:1.0
      URI: urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults

   Registrant Contact: The NETCONF WG of the IETF.

   XML: N/A, the requested URIs are XML namespaces.

   This document registers one module name in the 'YANG Module Names'
   registry, defined in [RFC6020] .

      name: ietf-netconf-with-defaults
      prefix: ncwd
      namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults
      RFC: XXXX // RFC Ed.: replace XXXX and remove this comment


8.  Security Considerations

   This document defines an extension to existing NETCONF protocol
   operations.  It does not introduce any new or increased security
   risks into the management system.

   The 'with-defaults' capability gives clients control over the
   retrieval of default data from a NETCONF datastore.  The security
   consideration of [I-D.ietf-netconf-4741bis] apply to this document as
   well.


9.  Acknowledgements

   Thanks to Martin Bjorklund, Sharon Chisholm, Phil Shafer, Juergen
   Schoenwaelder, Kent Watsen, Washam Fan and many other members of the
   NETCONF WG for providing important input to this document.


10.  Normative References

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

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



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              January 2004.

   [RFC4741]  Enns, R., "NETCONF Configuration Protocol", RFC 4741,
              December 2006.

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

   [I-D.ietf-netconf-4741bis]
              Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)",
              draft-ietf-netconf-4741bis-04 (work in progress),
              August 2010.

   [W3C.REC-xml-20081126]
              Sperberg-McQueen, C., Yergeau, F., Bray, T., Paoli, J.,
              and E. Maler, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.


Appendix A.  Usage Examples

A.1.  Example YANG Module

   The following YANG module defines an example interfaces table to
   demonstrate how the <with-defaults> parameter behaves for a specific
   data model.

   Note that this is not a real module, and implementation of this
   module is not required for conformance to the :with-defaults
   capability, defined in Section 4.  This module is not to be
   registered with IANA, and is not considered to be a code component.
   It is intentionally very terse, and includes few descriptive
   statements.


     module example {

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

     prefix exam;

     typedef status-type {
        description "Interface status";
        type enumeration {



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          enum ok;
          enum 'waking up';
          enum 'not feeling so good';
          enum 'better check it out';
          enum 'better call for help';
        }
        default ok;
     }

     container interfaces {
         description "Example interfaces group";

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

           leaf name {
             description
               "The administrative name of the interface.
                This is an identifier which is only unique
                within the scope of this list, and only
                within a specific server.";
             type string {
               length "1 .. max";
             }
           }

           leaf mtu {
             description
               "The maximum transmission unit (MTU) value assigned to
                this interface.";
             type uint32;
             default 1500;
           }

           leaf status {
             description
               "The current status of this interface.";
             type status-type;
             config false;
           }
         }
       }
     }







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A.2.  Example Data Set

   The following data element shows the conceptual contents of the
   example server for the protocol operation examples in the next
   section.  This includes all the configuration data nodes, non-
   configuration data nodes, and default leafs.



       <data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <interfaces xmlns="http://example.com/ns/interfaces">
           <interface>
             <name>eth0</name>
             <mtu>8192</mtu>
             <status>up</status>
           </interface>
           <interface>
             <name>eth1</name>
             <mtu>1500</mtu>
             <status>up</status>
           </interface>
           <interface>
             <name>eth2</name>
             <mtu>9000</mtu>
             <status>not feeling so good</status>
           </interface>
           <interface>
             <name>eth3</name>
             <mtu>1500</mtu>
             <status>waking up</status>
           </interface>
         </interfaces>
       </data>


   In this example, the 'mtu' field for each interface entry is set in
   the following manner:

              +--------------+--------------+--------------+
              | name         | set by       | mtu          |
              +--------------+--------------+--------------+
              | eth0         | client       | 8192         |
              | eth1         | server       | 1500         |
              | eth2         | client       | 9000         |
              | eth3         | client       | 1500         |
              +--------------+--------------+--------------+





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A.3.  Protocol Operation Examples

   The following examples shows some <get> operations using the 'with-
   defaults' element.  The data model used for these examples is defined
   in Appendix A.1.

   The client is retrieving all the data nodes within the 'interfaces'
   object, filtered with the <with-defaults> parameter.

A.3.1.  <with-defaults> = 'report-all'

   The behavior of the <with-defaults> parameter handling for the value
   'report-all' is demonstrated in this example.






































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

    <rpc-reply message-id="101"
               xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <data>
        <interfaces xmlns="http://example.com/ns/interfaces">
          <interface>
            <name>eth0</name>
            <mtu>8192</mtu>
            <status>up</status>
          </interface>
          <interface>
            <name>eth1</name>
            <mtu>1500</mtu>
            <status>up</status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <status>not feeling so good</status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu>1500</mtu>
            <status>waking up</status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>



A.3.2.  <with-defaults> = 'report-all-tagged'

   The behavior of the <with-defaults> parameter handling for the value
   'report-all-tagged' is demonstrated in this example.  A 'tagged' data
   node is an element that contains the wd:default XML attribute, set to



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   'true'.

   The actual data nodes tagged by the server depends on the defaults
   handling basic mode used by the server.  Only the data nodes that are
   considered to be default data will be tagged.

   In this example, the server's basic mode is equal to 'trim', so all
   data nodes that would contain the schema default value are tagged.
   If the server's basic mode is 'explicit', then only data nodes that
   are not explicitly set data are tagged.  If the server's basic mode
   is 'report-all', then no data nodes are tagged.








































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    <rpc message-id="102"
         xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <get>
        <filter type="subtree">
          <interfaces xmlns="http://example.com/ns/interfaces"/>
        </filter>
        <with-defaults
         xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
          report-all-tagged
        </with-defaults>
      </get>
    </rpc>

    <rpc-reply message-id="102"
               xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
               xmlns:wd="urn:ietf:params:xml:ns:netconf:default:1.0">
      <data>
        <interfaces xmlns="http://example.com/ns/interfaces">
          <interface>
            <name>eth0</name>
            <mtu>8192</mtu>
            <status wd:default="true">up</status>
          </interface>
          <interface>
            <name>eth1</name>
            <mtu wd:default="true">1500</mtu>
            <status wd:default="true">up</status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <status>not feeling so good</status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu wd:default="true">1500</mtu>
            <status>waking up</status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>










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A.3.3.  <with-defaults> = 'trim'

   The behavior of the <with-defaults> parameter handling for the value
   'trim' is demonstrated in this example.



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

    <rpc-reply message-id="103"
               xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <data>
        <interfaces xmlns="http://example.com/ns/interfaces">
          <interface>
            <name>eth0</name>
            <mtu>8192</mtu>
          </interface>
          <interface>
            <name>eth1</name>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <status>not feeling so good</status>
          </interface>
          <interface>
            <name>eth3</name>
            <status>waking up</status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>








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A.3.4.  <with-defaults> = 'explicit'

   The behavior of the <with-defaults> parameter handling for the value
   'explicit' is demonstrated in this example.



    <rpc message-id="104"
         xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <get>
        <filter type="subtree">
          <interfaces xmlns="http://example.com/ns/interfaces"/>
        </filter>
        <with-defaults
         xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults">
          explicit
        </with-defaults>
      </get>
    </rpc>

    <rpc-reply message-id="104"
               xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <data>
        <interfaces xmlns="http://example.com/ns/interfaces">
          <interface>
            <name>eth0</name>
            <mtu>8192</mtu>
            <status>up</status>
          </interface>
          <interface>
            <name>eth1</name>
            <status>up</status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <status>not feeling so good</status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu>1500</mtu>
            <status>waking up</status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>





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Appendix B.  Change Log

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

B.1.  11-12

   Made editorial clarifications based on AD review.

B.2.  10-11

   Changed term 'database' to 'configuration datastore' or generic
   'datastore'.

B.3.  09-10

   Changed term 'datastore' to 'database'.

   Added term 'default value'.

   Clarified verbage for data node containing a default value.

B.4.  08-09

   Removed non-volatile server requirements.

   Moved some text from basic-mode section into the the retrieval modes
   section.

   Added description and reference statements to the YANG module.

   Many bugfixes and clarifications, based on WGLC review comments.

B.5.  07-08

   Added report-all-tagged mode.

   Changed conformance so report-all or report-all-tagged mode SHOULD be
   supported.

   Clarified capability requirements for each mode, for edit-config and
   NV storage requirements.

   Changed rpc-error details for unsupported with-defaults value.

   Added XSD for wd:default attribute

   Expanded example to show report-all-tagged for a basic-mode=trim
   server.



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B.6.  06-07

   Removed text in capability identifier section about adding YANG
   module capability URI parameters.

   Changed YANG module namespace to match YANG format, and updated
   examples to use this new namespace.

   Fixed some typos.

B.7.  05-06

   Removed ':1.0' from capability URI.

   Removed open issues section because all known issues are closed.

   Moved examples to a separate appendix, and expanded them.

   Added example.yang as an appendix to properly explain the examples
   used within the document.

   Replaced normative term 'SHALL' with 'MUST' to be consistent within
   this document.

   Clarified <with-defaults> behavior for non-configuration data nodes.

   Clarified various sections based on WGLC comments on mailing list.

   Removed some unused terms.

   Reversed the order of the change log sections so the most recent
   changes are shown first.

B.8.  04-05

   Updated I-D and YANG module boiler-plate.

   Removed redundant 'with-defaults' YANG feature.

   Changed definition of 'explicit' mode to match the YANG definition

   Removed XSD because the YANG is normative and the XSD is
   unconstrained, and does not properly extend the 3 affected NETCONF
   operations.

   Made the YANG module a normative section instead of non-normative
   appendix.




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   Changed YANG from an informative to a normative reference,

   Changed 4741bis from an informative to a normative reference because
   the YANG module imports the ietf-netconf module in order to augment
   some operations.

   Updated capability requirements to include YANG module capability
   parameters.

   Added a description statement to the with-defaults leaf definition.

   Update open issues section; ready to close all open issues.

B.9.  03-04

   Clarifications

   Added non-netconf interfaces to the definition of explicitly set
   default data

B.10.  02-03

   Clarifications

   YAM added

   Use the same URN for the capability and the XML namespace to
   accommodate YANG, and avoid two separate URN/URIs being advertised in
   the HELLO message, for such a small function.

B.11.  01-02

   report-all made mandatory

   Placeholder for YAM added, XSD will be removed when 4741 provides the
   NETCONF YAM

   with-defaults is valid for state data as well (if state data has a
   defined default which might not be so frequent).  The definition of
   explicit was modified for state data.

B.12.  00-01

   Changed value set of with-default capability and element

   Added version to URI





Bierman & Lengyel        Expires April 17, 2011                [Page 31]

Internet-Draft                with-defaults                 October 2010


B.13.  -00

   Created from draft-bierman-netconf-with-defaults-01.txt

   It was decided by the NETCONF mailing list, that with-defaults should
   be a sub-element of each affected operation.  While this violates the
   XSD of RFC4741 this is acceptable and follows the ideas behind
   NETCONF and YANG.

   Hopefully it will be clarified in the 4741bis RFC whether such
   extensions are allowed.


Authors' Addresses

   Andy Bierman
   Brocade

   Email: andy.bierman@brocade.com


   Balazs Lengyel
   Ericsson
   Budapest,
   Hungary

   Email: balazs.lengyel@ericsson.com
























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