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rfc:rfc6243

Internet Engineering Task Force (IETF) A. Bierman Request for Comments: 6243 Brocade Category: Standards Track B. Lengyel ISSN: 2070-1721 Ericsson

                                                             June 2011
                With-defaults Capability for NETCONF

Abstract

 The Network Configuration Protocol (NETCONF) 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 is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6243.

Bierman & Lengyel Standards Track [Page 1] RFC 6243 with-defaults June 2011

Copyright Notice

 Copyright (c) 2011 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   1.2.  Default-Handling Behavior  . . . . . . . . . . . . . . . .  5
   1.3.  Client Controlled Retrieval of Default Data  . . . . . . .  5
 2.  Default-Handling Basic Modes . . . . . . . . . . . . . . . . .  6
   2.1.  'report-all' Basic Mode  . . . . . . . . . . . . . . . . .  6
     2.1.1.  'report-all' Basic Mode Retrieval  . . . . . . . . . .  6
     2.1.2.  'report-all' <with-defaults> Retrieval . . . . . . . .  6
     2.1.3.  'report-all' <edit-config> and <copy-config>
             Behavior . . . . . . . . . . . . . . . . . . . . . . .  6
   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  . . .  7
   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 . . . . . . . . . . . .  9
 4.  With-defaults Capability . . . . . . . . . . . . . . . . . . . 10
   4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
   4.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . . 10
   4.3.  Capability Identifier  . . . . . . . . . . . . . . . . . . 10
   4.4.  New Operations . . . . . . . . . . . . . . . . . . . . . . 11
   4.5.  Modifications to Existing Operations . . . . . . . . . . . 11
     4.5.1.  <get>, <get-config>, and <copy-config> Operations  . . 11
     4.5.2.  <edit-config> Operation  . . . . . . . . . . . . . . . 12

Bierman & Lengyel Standards Track [Page 2] RFC 6243 with-defaults June 2011

     4.5.3.  Other Operations . . . . . . . . . . . . . . . . . . . 13
   4.6.  Interactions with Other Capabilities . . . . . . . . . . . 13
 5.  YANG Module for the <with-defaults> Parameter  . . . . . . . . 13
 6.  XSD for the 'default' Attribute  . . . . . . . . . . . . . . . 17
 7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
 8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
 9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
 10. Normative References . . . . . . . . . . . . . . . . . . . . . 19
 Appendix A.  Usage Examples  . . . . . . . . . . . . . . . . . . . 20
   A.1.  Example YANG Module  . . . . . . . . . . . . . . . . . . . 20
   A.2.  Example Data Set . . . . . . . . . . . . . . . . . . . . . 21
   A.3.  Protocol Operation Examples  . . . . . . . . . . . . . . . 22
     A.3.1.  <with-defaults> = 'report-all' . . . . . . . . . . . . 22
     A.3.2.  <with-defaults> = 'report-all-tagged'  . . . . . . . . 23
     A.3.3.  <with-defaults> = 'trim' . . . . . . . . . . . . . . . 24
     A.3.4.  <with-defaults> = 'explicit' . . . . . . . . . . . . . 25

1. Introduction

 The NETCONF protocol [RFC6241] 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.,
 from 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 default-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 the Simple Network Management
    Protocol (SNMP).

Bierman & Lengyel Standards Track [Page 3] RFC 6243 with-defaults June 2011

 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.
 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 that is not the schema
    defined default value is also considered explicitly set data.
 <with-defaults> retrieval:  Refers to a protocol operation that
    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 [RFC6241]:
 o  client
 o  datastore
 o  operation
 o  server
 The following term is defined in [RFC6020]:
 o  data node

Bierman & Lengyel Standards Track [Page 4] RFC 6243 with-defaults June 2011

1.2. Default-Handling Behavior

 The default-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 that it considers to contain the default value.  The actual
     nodes omitted depend on the default-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 or not the target node
     currently exists.  The server's default-handling behavior will
     determine whether or not the requested node currently exists in
     the configuration datastore.

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.
 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's default-handling behavior, an XML
 [W3C.REC-xmlschema-0-20041028] attribute to identify default data,

Bierman & Lengyel Standards Track [Page 5] RFC 6243 with-defaults June 2011

 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. Default-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 default-handling,
 and the client can adjust accordingly.  Client implementations are
 expected to be powerful enough to support all three of the server
 basic default-handling modes.
 NETCONF servers report default data in different ways.  This document
 specifies three standard default-handling basic modes that a server
 implementer 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 that uses the 'report-all' basic mode does not consider any
 data node to be default data, even schema default data.

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

 If the 'report-all' basic mode is used by the server, then 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

Bierman & Lengyel Standards Track [Page 6] RFC 6243 with-defaults June 2011

 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 that 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 that are omitted in a basic-mode retrieval
 operation.  If the '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 that 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

 If the 'trim' basic mode is used by the server, then the server MUST
 support the <with-defaults> parameter with a value equal to 'trim',
 as specified in Section 3.2.

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 'default' attribute MUST be

Bierman & Lengyel Standards Track [Page 7] RFC 6243 with-defaults June 2011

 accepted in configuration input, as described in Section 4.5.1 and
 Section 4.5.2.

2.3. 'explicit' Basic Mode

 A server that 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

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

2.3.2. 'explicit' <with-defaults> Retrieval

 If the 'explicit' basic mode is used by the server, 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.
 If the server supports the 'report-all-tagged' retrieval mode in its
 :with-defaults capability, then the '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
 tagged data node (i.e., the 'default' attribute set to 'true' or '1')
 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 an 'invalid-value' error-
 tag.

Bierman & Lengyel Standards Track [Page 8] RFC 6243 with-defaults June 2011

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 that implements this specification MUST accept the
 <with-defaults> parameter containing the enumeration for any of the
 default-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 that was set by a client to its schema
 default value MUST be reported.  A conceptual data node that 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.

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.

Bierman & Lengyel Standards Track [Page 9] RFC 6243 with-defaults June 2011

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

4. With-defaults Capability

4.1. Overview

 The :with-defaults capability indicates which default-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 4.3.
 o  MUST support the YANG module defined in Section 5 for the default-
    handling mode indicated by the 'basic-mode' parameter.
 o  SHOULD support the YANG module in Section 5 for the default-
    handling mode identified by the 'report-all' or 'report-all-
    tagged' enumeration value.
 o  If the 'report-all-tagged' default-handling mode is supported,
    then the 'default' attribute MUST be supported.
 o  MAY support the YANG module in Section 5 for additional default-
    handling modes.

4.2. Dependencies

 None.

4.3. 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.

Bierman & Lengyel Standards Track [Page 10] RFC 6243 with-defaults June 2011

 The identifier MAY have another parameter: "also-supported".  This
 parameter indicates which additional enumeration values (besides the
 basic-mode enumeration) the server will accept for the
 <with-defaults> parameter in Section 5.  The value of the parameter
 is a comma-separated list of one or more modes that are supported
 besides 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
 that 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

4.4. New Operations

 None.

4.5. Modifications to Existing Operations

4.5.1. <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.
 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

Bierman & Lengyel Standards Track [Page 11] RFC 6243 with-defaults June 2011

 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 4.3.
 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
 'default' attribute defined in Section 6 also impacts the
 <copy-config> operation.  If the 'default' attribute is present and
 set to 'true' or '1', 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 an 'invalid-value' error-tag.

4.5.2. <edit-config> Operation

 The <edit-config> operation has several editing modes.  The 'create'
 and 'delete' editing operations are affected by the default-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 an 'invalid-value'
 error-tag.

Bierman & Lengyel Standards Track [Page 12] RFC 6243 with-defaults June 2011

 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 default-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
 'default' attribute defined in Section 6 also impacts the
 <edit-config> operation.  If the 'default' attribute is present and
 set to 'true' or '1', 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 an 'invalid-value' error-tag.
 If the '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 [RFC6241].  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.

4.5.3. 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.

4.6. 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 [RFC6241].  Every NETCONF server that supports the
 :with-defaults capability MUST implement this YANG module.

Bierman & Lengyel Standards Track [Page 13] RFC 6243 with-defaults June 2011

<CODE BEGINS> file="ietf-netconf-with-defaults@2011-06-01.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:  <netconf@ietf.org>
     WG Chair: Bert Wijnen
               <bertietf@bwijnen.net>
     WG Chair: Mehmet Ersue
               <mehmet.ersue@nsn.com>
     Editor: Andy Bierman
             <andy.bierman@brocade.com>
     Editor: Balazs Lengyel
             <balazs.lengyel@ericsson.com>";
   description
    "This module defines an extension to the NETCONF protocol
     that allows the NETCONF client to control how default
     values are handled by the server in particular NETCONF
     operations.
     Copyright (c) 2011 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 6243; see
     the RFC itself for full legal notices.";

Bierman & Lengyel Standards Track [Page 14] RFC 6243 with-defaults June 2011

   revision 2011-06-01 {
     description
       "Initial version.";
     reference
      "RFC 6243: With-defaults Capability for NETCONF";
   }
   typedef with-defaults-mode {
      description
        "Possible modes to report default data.";
      reference
         "RFC 6243; Section 3.";
      type enumeration {
         enum report-all {
             description
               "All default data is reported.";
             reference
               "RFC 6243; Section 3.1";
         }
         enum report-all-tagged {
             description
               "All default data is reported.
                Any nodes considered to be default data
                will contain a 'default' XML attribute,
                set to 'true' or '1'.";
             reference
               "RFC 6243; Section 3.4";
         }
         enum trim {
             description
               "Values are not reported if they contain the default.";
             reference
               "RFC 6243; Section 3.2";
         }
         enum explicit {
             description
               "Report values that contain the definition of
                explicitly set data.";
             reference
               "RFC 6243; Section 3.3";
         }
     }
   }
   grouping with-defaults-parameters {
     description
       "Contains the <with-defaults> parameter for control
        of defaults in NETCONF retrieval operations.";

Bierman & Lengyel Standards Track [Page 15] RFC 6243 with-defaults June 2011

     leaf with-defaults {
       description
         "The explicit defaults processing mode requested.";
       reference
         "RFC 6243; Section 4.5.1";
       type with-defaults-mode;
     }
   }
   // extending the get-config operation
   augment /nc:get-config/nc:input {
       description
         "Adds the <with-defaults> parameter to the
          input of the NETCONF <get-config> operation.";
       reference
         "RFC 6243; Section 4.5.1";
       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 6243; Section 4.5.1";
       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 6243; Section 4.5.1";
       uses with-defaults-parameters;
   }
}
<CODE ENDS>

Bierman & Lengyel Standards Track [Page 16] RFC 6243 with-defaults June 2011

6. XSD for the 'default' Attribute

 The following XML Schema document [W3C.REC-xml-20081126] defines the
 'default' attribute, described within this document.  This XSD is
 only relevant if the server supports the 'report-all-tagged' defaults
 retrieval mode.
 The 'default' attribute uses the XSD data type 'boolean'.  In
 accordance with Section 3.2.2.1 of XML Schema Part 2: Datatypes, the
 allowable lexical representations for the xs:boolean datatype are the
 strings "0" and "false" for the concept of false and the strings "1"
 and "true" for the concept of true.  Implementations MUST support
 both styles of lexical representation.

<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' or '1', then
      the data node is default data.  If 'false' or '0', then the
      data node is not default data.
    </xs:documentation>
  </xs:annotation>
</xs:attribute>

Bierman & Lengyel Standards Track [Page 17] RFC 6243 with-defaults June 2011

</xs:schema>

<CODE ENDS>

7. IANA Considerations

 This document registers the following capability identifier URN in
 the 'Network Configuration Protocol (NETCONF) Capability URNs'
 registry:
    urn:ietf:params:netconf:capability:with-defaults:1.0
 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: 6243

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 [RFC6241] applies to this document as well.

Bierman & Lengyel Standards Track [Page 18] RFC 6243 with-defaults June 2011

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,
            January 2004.
 [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
            Network Configuration Protocol (NETCONF)", RFC 6020,
            October 2010.
 [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
            and A.  Bierman, Ed., "Network Configuration Protocol
            (NETCONF)", RFC 6241, June 2011.
 [W3C.REC-xml-20081126]
            Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
            F. Yergeau, "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>.
 [W3C.REC-xmlschema-0-20041028]
            Fallside, D. and P. Walmsley, "XML Schema Part 0: Primer
            Second Edition", World Wide Web Consortium Recommendation
            REC-xmlschema-0-20041028, October 2004,
            <http://www.w3.org/TR/2004/REC-xmlschema-0-20041028>.

Bierman & Lengyel Standards Track [Page 19] RFC 6243 with-defaults June 2011

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 {
        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 that is only unique
              within the scope of this list, and only
              within a specific server.";
           type string {

Bierman & Lengyel Standards Track [Page 20] RFC 6243 with-defaults June 2011

             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;
         }
       }
     }
   }

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>

Bierman & Lengyel Standards Track [Page 21] RFC 6243 with-defaults June 2011

           <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         |
            +--------------+--------------+--------------+

A.3. Protocol Operation Examples

 The following examples show 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.
  <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>

Bierman & Lengyel Standards Track [Page 22] RFC 6243 with-defaults June 2011

      <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 'default' XML attribute, set to
 'true' or '1'.
 The actual data nodes tagged by the server depend on the default-
 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.
  <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>

Bierman & Lengyel Standards Track [Page 23] RFC 6243 with-defaults June 2011

      <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>

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

Bierman & Lengyel Standards Track [Page 24] RFC 6243 with-defaults June 2011

       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>

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>

Bierman & Lengyel Standards Track [Page 25] RFC 6243 with-defaults June 2011

  <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>

Authors' Addresses

 Andy Bierman
 Brocade
 EMail: andy.bierman@brocade.com
 Balazs Lengyel
 Ericsson
 Budapest,
 Hungary
 EMail: balazs.lengyel@ericsson.com

Bierman & Lengyel Standards Track [Page 26]

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