NETCONF                                                       A. Bierman
Internet-Draft                                         InterWorking Labs
Intended status: Standards Track                              B. Lengyel
Expires: October November 21, 2010                                      Ericsson
                                                          April 19,
                                                            May 20, 2010

                  With-defaults capability for NETCONF
                  draft-ietf-netconf-with-defaults-07
                  draft-ietf-netconf-with-defaults-08

Abstract

   The NETCONF protocol defines ways to read and edit configuration data
   from a NETCONF server.  Part of this data is may not be set by the
   NETCONF client, but rather a default value is used.  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
   datastore or send it to the client. client in a retrieval operation reply.
   In other situations the NETCONF client will need this data as part of
   the NETCONF <rpc-
   reply> <rpc-reply> messages.  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 handled by the server,
   and control whether default values are part of NETCONF <rpc-reply>
   messages or <copy-config> output to the target URL. a file.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October November 21, 2010.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Current handling of default data .  Defaults Handling Behavior . . . . . . . . . . . .  5
   2.  With-defaults Capability . . . .  5
     1.3.  Client Controlled Retrieval of Default Data  . . . . . . .  5
   2.  Defaults Handling Basic Modes  . . . . . . . .  6
     2.1.  Overview . . . . . . . .  6
     2.1.  'report-all' Basic Mode  . . . . . . . . . . . . . . . . .  6
     2.2.  Dependencies
       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> Behavior  . . . . .  6
     2.3.  Conformance . . . .  6
       2.1.4.  'report-all' Non-volatile Storage Behavior . . . . . .  7
     2.2.  'trim' Basic Mode  . . . . . . . . . . . . .  6
     2.4.  Capability Identifier . . . . . . .  7
       2.2.1.  'trim' Basic Mode Retrieval  . . . . . . . . . . .  6
     2.5.  New Operations . .  7
       2.2.2.  'trim' <with-defaults> Retrieval . . . . . . . . . . .  7
       2.2.3.  'trim' <edit-config> Behavior  . . . . . . . . .  7
     2.6.  Modifications to Existing Operations . . .  7
       2.2.4.  'trim' Non-volatile Storage Behavior . . . . . . . .  7
     2.7.  Interactions with Other Capabilities .  8
     2.3.  'explicit' Basic Mode  . . . . . . . . . .  8
   3.  YANG Module . . . . . . . .  8
       2.3.1.  'explicit' Basic Mode Retrieval  . . . . . . . . . . .  8
       2.3.2.  'explicit' <with-defaults> Retrieval . . . . . .  8
   4.  IANA Considerations . . .  8
       2.3.3.  'explicit' <edit-config> Behavior  . . . . . . . . . .  8
       2.3.4.  'explicit' Non-volatile Storage Behavior . . . . . . .  9
   3.  Retrieval of Default Data  . 10
   5.  Security Considerations . . . . . . . . . . . . . . . . .  9
     3.1.  'report-all-tagged' Retrieval Mode . . 11
   6.  Acknowledgements . . . . . . . . . .  9
   4.  With-defaults Capability . . . . . . . . . . . . . 11
   7.  Normative References . . . . . . 10
     4.1.  Overview . . . . . . . . . . . . . . . 11
   Appendix A.  Usage Examples . . . . . . . . . . 10
     4.2.  Dependencies . . . . . . . . . 12
     A.1.  Example YANG Module . . . . . . . . . . . . . . 10
     4.3.  Conformance  . . . . . 12
     A.2.  Example Data Set . . . . . . . . . . . . . . . . . . 10
     4.4.  Capability Identifier  . . . 14
     A.3.  Protocol Operation Examples . . . . . . . . . . . . . . . 15
       A.3.1.  <with-defaults> = 'report-all' 10
     4.5.  New Operations . . . . . . . . . . . . 15
       A.3.2.  <with-defaults> = 'trim' . . . . . . . . . . 11
     4.6.  Modifications to Existing Operations . . . . . 16
       A.3.3.  <with-defaults> = 'explicit' . . . . . . 11
       4.6.1.  <get>, <get-config>, and <copy-config> Operations  . . 11
       4.6.2.  <edit-config> Operation  . . . . . 17
   Appendix B.  Change Log . . . . . . . . . . 12
       4.6.3.  Other Operations . . . . . . . . . . . 18
     B.1.  06-07 . . . . . . . . 12
     4.7.  Interactions with Other Capabilities . . . . . . . . . . . 13
   5.  YANG Module for the <with-defaults> Parameter  . . . . . . . 19
     B.2.  05-06 . 13
   6.  XSD for the 'wd:default' Attribute . . . . . . . . . . . . . . 15
   7.  IANA Considerations  . . . . . . . . . . . 19
     B.3.  04-05 . . . . . . . . . . 16
   8.  Security Considerations  . . . . . . . . . . . . . . . . 19
     B.4.  03-04 . . . 17
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
     B.5.  02-03 17
   10. Normative References . . . . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Usage Examples  . . . . . 20
     B.6.  01-02 . . . . . . . . . . . . . . 18
     A.1.  Example YANG Module  . . . . . . . . . . . . 20
     B.7.  00-01 . . . . . . . 18
     A.2.  Example Data Set . . . . . . . . . . . . . . . . . . . . . 20
     B.8.  -00
     A.3.  Protocol Operation Examples  . . . . . . . . . . . . . . . 21
       A.3.1.  <with-defaults> = 'report-all' . . . . . . . . . . . . 21
   Authors' Addresses
       A.3.2.  <with-defaults> = 'report-all-tagged'  . . . . . . . . 22
       A.3.3.  <with-defaults> = 'trim' . . . . . . . . . . . . . . . 25
       A.3.4.  <with-defaults> = 'explicit' . 21

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 e.g., a document
   formally describing the data models supported by the NETCONF server.

   A networking device may have a large number of default values.  Often
   the default values are not interesting or specifically defined with a
   "reasonable" value, so that the management user does not have 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 . . . . . . . . . . . . 26
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 27
     B.1.  07-08  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     B.2.  06-07  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     B.3.  05-06  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     B.4.  04-05  . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     B.5.  03-04  . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     B.6.  02-03  . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     B.7.  01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.8.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     B.9.  -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29

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 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,
      CLI or 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 item.  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:  Data considered by a particular server to contain a
      default value.  Default data is not kept in a configuration
      datastore.
   Explicitly set data:  Data that is set to any value by a NETCONF
      client or other management application by the way of an actual
      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.

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

   The following term is defined in [I-D.ietf-netmod-yang]:
   o  data node

1.2.  Defaults Handling Behavior

   The defaults handling behavior used by a server will impact NETCONF
   protocol operations in three 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.  The nodes that are returned in this case are
       the only nodes the server considers to exist in the datastore.

   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
       datastore or not.

   3.  NV Storage: The server's defaults handling behavior will affect
       which data nodes are saved in non-volatile storage.

1.3.  Client Controlled Retrieval of Default Data

   A networking device may have a large number of default values.  Often
   the default values are not interesting or specifically defined with a
   "reasonable" value, so that the management user does not have 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 a
      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 default data as part
   of the NETCONF <rpc-reply> messages.

   This document defines a NETCONF protocol capability to identify the
   server defaults handling behavior, and a YANG module extension to the
   NETCONF protocol that allows the NETCONF client will need to control whether
   default data is returned in certain NETCONF <rpc-reply> messages.

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.

2.1.1.  'report-all' Basic Mode Retrieval

   All data nodes MUST be reported.

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

   All data nodes MUST be reported, including any data nodes considered
   to be default data by the server.

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

   The server MUST consider every data node to exist, even those
   represented by a schema default value.

   o  A valid 'create' operation for a data node that contains its
      schema default value MUST fail with a 'data-exists' error-tag.
   o  A valid 'delete' operation 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.

2.1.4.  'report-all' Non-volatile Storage Behavior

   All data nodes MUST be saved in non-volatile storage.

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

   Data nodes MUST NOT be reported if they match the schema default
   value.  Non-configuration data nodes containing the schema default
   value MUST NOT be reported.

2.2.2.  'trim' <with-defaults> Retrieval

   Data nodes MUST NOT be reported if they match the schema default
   value.  Non-configuration data nodes containing the schema default
   value MUST NOT be reported.

2.2.3.  'trim' <edit-config> Behavior

   The server MUST consider any data from the node: node that does not contain its
   schema default value to exist.

   o  The management application often needs  A valid 'create' operation for a single, definitive data node that has a schema
      default value defined MUST succeed.
   o  A valid 'delete' operation for a missing data node that has a
      schema default value MUST fail with a 'data-missing' error-tag.
   o  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 datastore.  This has the same affect
      as removing the data node and
      complete set of treating it as default data.

   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 values input.  If all NETCONF sub-operation
   parameters are valid, then the server will treat a tagged data node
   as a request to return that determine how 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.  If the data
   node within the NETCONF message contains a
      networking device works.
   o  Documentation about value in this case, it
   MUST be equal to the schema default values can value.

2.2.4.  'trim' Non-volatile Storage Behavior

   All data nodes, except those set to their schema default value, MUST
   be unreliable or
      unavailable.
   o  Some management applications might not have saved in non-volatile storage.

2.3.  'explicit' Basic Mode

   A server which uses the capabilities 'explicit' basic mode MUST consider any data
   node that is not explicitly set data to
      correctly parse and interpret formal be default data.

2.3.1.  'explicit' Basic Mode Retrieval

   If a client set a data models.
   o  Human users might want node to its schema default value, it MUST
   always be reported.  If the server set a data node to understand the received its schema
   default value, it MUST NOT be reported.  Non-configuration data without
      consultation of the documentation.

   In all these cases nodes
   containing the NETCONF client will need schema default value MUST be reported.

2.3.2.  'explicit' <with-defaults> Retrieval

   If a client set a data as part
   of node to its schema default value, it MUST be
   reported.  If the NETCONF <rpc-reply> messages.

   This document defines server set a capability-based extension data node to its schema default value,
   it MUST NOT be reported.  Non-configuration data nodes containing the NETCONF
   protocol that allows the NETCONF client to control whether
   schema default value MUST be reported.

2.3.3.  'explicit' <edit-config> Behavior

   The server considers any data node that is part of NETCONF <rpc-reply> messages.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are explicitly set data to be interpreted as described in [RFC2119].

   Data model schema:
   exist.

   o  A document or set of documents describing the valid 'create' operation for a data models supported node that has been set by the NETCONF server.

   Management Application: a
      client to its schema default value MUST fail with a 'data-exists'
      error-tag.
   o  A computer program running outside the
      NETCONF server valid 'create' operation for a data node that configures or supervises has been set by
      the NETCONF server. server to its schema default value MUST succeed.
   o  A management application can reach the device e.g. via NETCONF,
      CLI or SNMP.
   Default data:  Data specified in the valid 'delete' operation for a data model node that has been set by a
      client to its schema as default, default value MUST succeed.
   o  A valid 'delete' operation for a data node that is has been set or used by
      the device whenever 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 'wd:default' attribute MUST be
   accepted in configuration input.  If all NETCONF client or
      other management application/user does not provide a specific
      value for sub-operation
   parameters are valid, then the relevant data item.  Default server will treat a tagged data MAY or may not be
      stored node
   as part of a configuration datastore.
   Explicitly set data:  Data request to return that is set node to any value by a NETCONF
      client or other management application by default data.  If this request is
   valid within the way context of an actual
      management the requested NETCONF operation, including any then the
   data model schema node is removed and returned to its default value.  Any value set by  If the data
   node within the NETCONF server which is not message contains a value in this case, it
   MUST be equal to the schema defined default value is also considered value.

2.3.4.  'explicit' Non-volatile Storage Behavior

   All data nodes that are explicitly set
      data.

   In addition the following terms are defined data MUST be saved in RFC 4741 and are not
   redefined here:
   o  client
   o  operation
   o  server

1.2.  Current handling non-
   volatile storage.

3.  Retrieval of default data Default Data

   This document defines a new parameter, called <with-defaults>, which
   can be added to specific NETCONF does not define whether operation request messages to
   control how retrieval of default data is part treated by the server.

   The server MUST accept the <with-defaults> parameter containing the
   enumeration for any of the
   datastore/data model, or if defaults handling modes it is meta-data supports, as
   defined in Section 5.

   The <with-defaults> parameter contains one of the three basic mode
   enumerations defined above, to request that influences the
   behavior retrieval operation
   be performed using the specified defaults handling basic mode.

3.1.  'report-all-tagged' Retrieval Mode

   In addition to the basic modes, a special variant of '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 NETCONF server, but is not actually part of server returns all data nodes, just like the
   datastore.  This document is intended to support either type of
   implementation, without deciding which approach is better.

   As
   'report-all' mode, except a consequence of this approach, NETCONF servers data node that do not
   implement is considered by the :with-defaults capability may or may not return default
   data.

   Different NETCONF servers report
   server to contain default data in different ways. will include an XML attribute to
   indicate this condition.  This document specifies the following three basic modes:

   report-all:  All default data is always reported.
   trim:  Values useful for an application to
   determine which nodes are not reported if they match the considered to contain default value (as
      specified in the data model schema).  Note that non-configuration data nodes containing by the schema default value are not reported
      either.
   explicit:  Report only values that match
   server, within a single retrieval operation.

   A server which supports 'report-all-tagged' MUST also accept the definition 'wd:
   default' XML attribute it is present within configuration input to
   the <edit-config> or <copy-config> operations.  Refer to Section 6
   for XML encoding details of explicitly
      set data.  For non-configuration data, this has the same affect as
      'report-all'.

2. 'wd:default' XML attribute.

4.  With-defaults Capability

2.1.

4.1.  Overview

   The :with-defaults capability indicates that the NETCONF server makes
   it possible
   supports a specific defaults handling basic mode.  It may also
   indicate support for the additional defaults retrieval modes.  These
   retrieval modes allow a NETCONF client to control whether default
   data is part of NETCONF <rpc-reply> messages.  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 capability:

   o  MUST indicate its basic behavior, whether it sends default data in mode behavior by including the
   absence of any specific request from 'basic-
      mode' parameter in the NETCONF client; and 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 and mode.
   o  MAY support other additional defaults handling modes.

   A server indicating 'explicit' either in the 'basic-mode' or the
   'also-supported' parameter MUST be able to differentiate between
   normal default data and explicitly set data.

2.2.

4.2.  Dependencies

   None

2.3.

4.3.  Conformance

   Every NETCONF server SHOULD implement this capability.

2.4.

4.4.  Capability Identifier

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

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

   The identifier MUST have a parameter: "basic-mode".  This indicates
   how the server reports will treat default data in <rpc-reply> messages, in the
   case the client does not specify the required behavior data, as defined in the <rpc>
   request. Section 2.

   The allowed values of this parameter are report-all, trim,
   explicit 'report-all', 'trim', and
   'explicit', as listed defined in Section 1.2. 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 two more modes that are supported beside the mode
   indicated in the 'basic-mode' parameter.  Possible modes are taken from the
   list 'report-
   all', 'report-all-tagged', 'trim', and 'explicit', as defined in
   Section 1.2. 5.

   Note that this protocol capability URI is separate from the YANG
   module capability URI for the YANG module in Section 3. 5.  A server
   which implements this module will MUST also advertise a YANG module
   capability URI according to the rules specified in
   [I-D.ietf-netmod-yang].

   Examples:

   urn:ietf:params:netconf:capability:with-defaults?basic-mode=report-
   all

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

2.5.

   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

2.6.

4.6.  Modifications to Existing Operations

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

   A new <with-defaults> XML child element is added to the input for the
   <get>, <get-
   config> <get-config> and <copy-config> operations.  If the <with-defaults> <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 element. 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 3, 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 list
   in Section 1.2. 2.  The allowed values are restricted to the values that
   the device indicates support for in it supports within the with-defaults capability capability,
   in the basic 'basic-mode' and also-supported 'also-supported' parameters.

   If an unsupported value is used, the NETCONF server MUST return an
   <rpc-reply> with an <rpc-error> element.  The <error-tag> MUST SHOULD be
   'operation-not-supported',
   'invalid-value', and the <error-app-tag> MUST SHOULD be 'with-
   defaults-mode-not-supported'. 'with-defaults-
   mode-not-supported'.

   If the <with-defaults> element is not present, the server follows MUST follow
   its basic mode behavior as indicated by the with-defaults capability
   identifier's 'basic-
   mode' parameter see 'basic-mode' parameter, defined in Section 2.4.

   Affected operations:
   o  <get>
   o  <get-config>
   o  <copy-config> 4.4.

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

4.6.2.  <edit-config> Operation

   The <edit-config> operation has four sub-operations.  The 'create'
   and 'delete' sub-operations are affected by the defaults handling
   basic mode.

   The 'create' sub-operation MUST fail with a 'data-exists' error-tag
   value if the server considers the target data node to already have a
   current value.

   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 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 database).

   If this editing mode is used, then the effective sub-operation for
   the target is a NETCONF datastore (running, candidate data node MUST be 'create', 'merge' or
   startup) 'replace'.  If
   'create' is the capability has no effect; effective sub-operation, then the with-defaults parameter,
   if present, MUST create request must
   be silently ignored. valid on its own (e.g., current data node MUST NOT exist).  The
   procedure for determining the effective sub-operation is defined in
   [I-D.ietf-netconf-4741bis].  It is derived from the 'default-
   operation' parameter and/or any 'nc:operation' attribute that are
   present in the data node or any of its ancestor nodes, within the
   <edit-config> request message.

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.

2.7.

4.7.  Interactions with Other Capabilities

   None

3.

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 [I-D.ietf-netmod-yang].  The above
   operations are defined in YANG in [I-D.ietf-netconf-4741bis].  Every
   NETCONF server SHOULD which supports the :with-defaults capability MUST
   implement this YANG module.

 <CODE BEGINS> file="ietf-netconf-with-defaults.yang" file="ietf-netconf-with-defaults@2010-05-19.yang"

 module ietf-netconf-with-defaults {

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

    prefix nwd;

    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:andyb@iwl.com>

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

    description
     "This module defines a capability-based extension to the
      NETCONF protocol that allows the NETCONF client to control
      whether default values are part of NETCONF
      <rpc-reply> messages or <copy-config> output to the target URL.

      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-06.txt draft-ietf-netmod-with-defaults-08.txt

    revision 2010-04-19 2010-05-19 {
      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 in
          rpc-reply messages.";
       type enumeration {
          enum report-all {
              description
                "All default data is always reported.";
          }
          enum report-all-tagged {
              description
                "All default data is reported.
                 Any nodes considered to be default data
                 will contain a 'wd:default' XML attribute,
                 set to 'true'.";
          }
          enum trim {
              description
                "Values are not reported if they match the default.";
          }
          enum explicit {
              description
                "Report values that match the definition of
                 explicitly set data.";
          }
      }
    }

    grouping with-defaults-parameters {
      leaf with-defaults {
        description
          "The explicit defaults processing mode requested.";
        type with-defaults-mode;
      }
    }

    // extending the get-config operation
    augment /nc:get-config/nc:input {
        uses with-defaults-parameters;
    }

    // extending the get operation
    augment /nc:get/nc:input {
        uses with-defaults-parameters;
    }

    // extending the copy-config operation
    augment /nc:copy-config/nc:input {
        uses with-defaults-parameters;
    }

 }

 <CODE ENDS>

4.

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
   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"
                 form="qualified"
                 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 one the following capability identifier URN from in
   the 'Network Configuration Protocol [RFC4741] Capability URNs' registry,
   and registers the same URN for the NETCONF XML namespace in the "IETF
   XML registry" [RFC3688]. URNs registry':

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

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

   +----------------+--------------------------------------------------+
   | Index          | Capability Identifier                            |
   +----------------+--------------------------------------------------+
   | :with-defaults | urn:ietf:params:netconf:capability:with-defaults |
   +----------------+--------------------------------------------------+

   This document also registers one module name two XML namespace URNs in the 'YANG Module
   Names' registry, 'IETF XML
   registry', following the format defined in [I-D.ietf-netmod-yang] . [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 following
   data should be recorded NETCONF WG of the IETF.

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

   This document registers one module name in this registry:

   +----------+--------------------------------------------------------+
   | Field    | Value                                                  |
   +----------+--------------------------------------------------------+
   | Module   | ietf-netconf-with-defaults                             |
   | Name     |                                                        |
   | the 'YANG Module   | Names'
   registry, defined in [I-D.ietf-netmod-yang] .

      name: ietf-netconf-with-defaults
      prefix: nwd                                                    |
   | Prefix   |                                                        |
   | XML      |
      namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-with-defaults |
   | Namespac |                                                        |
   | e        |                                                        |
   | Module   |
      RFC: XXXX // RFC Ed.: replace XXXX and remove               |
   | RFC      |                                                        |
   +----------+--------------------------------------------------------+

5. this comment

8.  Security Considerations

   This document defines a minor 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 client control over the
   retrieval of particular types of XML data from a configuration
   database.
   datastore.  They only suppress data that can already be retrieved
   with the standard protocol operations, and do not add any data to the
   configuration database.

6. datastore.

9.  Acknowledgements

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

7.

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.

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

   [I-D.ietf-netconf-4741bis]
              Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)",
              draft-ietf-netconf-4741bis-02 (work in progress),
              February 2010.

   [I-D.ietf-netmod-yang]
              Bjorklund, M., "YANG - A data modeling language for
              NETCONF", draft-ietf-netmod-yang-12 (work in progress),
              April 2010.

   [W3C.REC-xml-20081126]
              Yergeau, F., Maler, E., Bray, T., Paoli, J., Sperberg-McQueen, C., and T. Bray, C.
              Sperberg-McQueen, "Extensible Markup Language (XML) 1.0
              (Fifth Edition)", World Wide Web Consortium
              Recommendation REC-
              xml-20081126, 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 protocol
   capability, defined in Section 2. 4.  This module is not to be
   registered with IANA. IANA, and is not considered to be a code component.
   It is intentionally very terse, and includes few descriptive
   statements.

   <CODE BEGINS> file="example.yang"

     module example {

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

     prefix exam;

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

   <CODE ENDS>

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>
             <itf-status>up</itf-status>
           </interface>
           <interface>
             <name>eth1</name>
             <mtu>1500</mtu>
             <itf-status>up</itf-status>
           </interface>
           <interface>
             <name>eth2</name>
             <mtu>9000</mtu>
             <itf-status>not feeling so good</itf-status>
           </interface>
           <interface>
             <name>eth3</name>
             <mtu>1500</mtu>
             <itf-status>waking up</itf-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 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.

    <rpc message-id="102" 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="102" 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>
            <itf-status>up</itf-status>
          </interface>
          <interface>
            <name>eth1</name>
            <mtu>1500</mtu>
            <itf-status>up</itf-status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <itf-status>not feeling so good</itf-status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu>1500</mtu>
            <itf-status>waking up</itf-status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>

A.3.2.  <with-defaults> = 'trim' '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
   'true'.  Any subtrees within the element are also considered to be
   tagged as dafault data.

   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.

    <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>
            <itf-status wd:default="true">up</itf-status>
          </interface>
          <interface>
            <name>eth1</name>
            <mtu wd:default="true">1500</mtu>
            <itf-status wd:default="true">up</itf-status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <itf-status>not feeling so good</itf-status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu wd:default="true">1500</mtu>
            <itf-status>waking up</itf-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
         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>
            <itf-status>not feeling so good</itf-status>
          </interface>
          <interface>
            <name>eth3</name>
            <itf-status>waking up</itf-status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>

A.3.3.

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

   The behavior of the <with-defaults > <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>
            <itf-status>up</itf-status>
          </interface>
          <interface>
            <name>eth1</name>
            <itf-status>up</itf-status>
          </interface>
          <interface>
            <name>eth2</name>
            <mtu>9000</mtu>
            <itf-status>not feeling so good</itf-status>
          </interface>
          <interface>
            <name>eth3</name>
            <mtu>1500</mtu>
            <itf-status>waking up</itf-status>
          </interface>
        </interfaces>
      </data>
    </rpc-reply>

Appendix B.  Change Log

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

B.1.  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.

B.2.  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.2.

B.3.  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.3.

B.4.  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.

   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.4.

B.5.  03-04

   Clarifications

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

B.5.

B.6.  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.6.

B.7.  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.7.

B.8.  00-01

   Changed value set of with-default capability and element

   Added version to URI

B.8.

B.9.  -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
   InterWorking Labs
   Santa Cruz,
   Scotts Valley, CA
   USA

   Phone: +1 831 460 7010
   Email: andyb@iwl.com
   Balazs Lengyel
   Ericsson
   Budapest,
   Hungary

   Email: balazs.lengyel@ericsson.com