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

NETCONF                                                       A. Bierman
Internet-Draft                                         InterWorking Labs
Intended status: Standards Track                              B. Lengyel
Expires: September 6, 2010                                      Ericsson
                                                           March 5, 2010


                  With-defaults capability for NETCONF
                  draft-ietf-netconf-with-defaults-05

Abstract

   The NETCONF protocol defines ways to read configuration data from a
   NETCONF server.  Part of this data is not 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 send it to the client.  In other situations
   the NETCONF client will need this data as part of the NETCONF <rpc-
   reply> messages.  This document 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.

Status of this Memo

   This Internet-Draft is submitted to IETF 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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   This Internet-Draft will expire on September 6, 2010.

Copyright Notice




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   Copyright (c) 2010 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 BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
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   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.



























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Current handling of default data . . . . . . . . . . . . .  5
   2.  With-defaults Capability . . . . . . . . . . . . . . . . . . .  6
     2.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . .  6
     2.3.  Conformance  . . . . . . . . . . . . . . . . . . . . . . .  6
     2.4.  Capability Identifier  . . . . . . . . . . . . . . . . . .  6
     2.5.  New Operations . . . . . . . . . . . . . . . . . . . . . .  7
     2.6.  Modifications to Existing Operations . . . . . . . . . . .  7
     2.7.  Interactions with Other Capabilities . . . . . . . . . . .  9
   3.  YANG Module  . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Open Issues . . . . . . . . . . . . . . . . . . . . . 13
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 14
     B.1.  -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     B.2.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     B.3.  01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     B.4.  02-03  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     B.5.  03-04  . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     B.6.  04-05  . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
























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1.  Introduction

   The NETCONF protocol [RFC4741] defines ways to read configuration
   data from a NETCONF server.  Part of this data is not 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 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 a NETCONF client will need the
   default data from the node:

   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 capability-based extension to the NETCONF
   protocol that allows the NETCONF client to control whether default
   data 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 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.






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   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 the
      NETCONF, CLI or SNMP.
   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.  Default data MAY or MAY NOT be
      stored as part of 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.

   In addition the following terms are defined in RFC 4741 and are not
   redefined here:
   o  client
   o  operation
   o  RPC
   o  RPC request
   o  RPC response
   o  server

1.2.  Current handling of default data

   NETCONF does not define whether default data is part of the
   datastore/data model, or if it is meta-data that influences the
   behavior of the NETCONF server, but is not actually part of the
   datastore.  This document is intended to support either type of
   implementation, without deciding which approach is better.

   As a consequence of this approach, NETCONF servers that do not
   implement the :with-defaults capability may or may not return default
   data.

   Different NETCONF servers report default data in different ways.
   This document specifies the following three basic modes:

   report-all:  All default data is always reported.
   trim:  Values are not reported if they match the default value (as
      specified in the data model schema).
   explicit:  Report only values that match the definition of explicitly
      set data.






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2.  With-defaults Capability

2.1.  Overview

   The :with-defaults capability indicates that the NETCONF server makes
   it possible for the 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 MUST
   indicate its basic behavior, whether it sends default data in the
   absence of any specific request from the NETCONF client; and MUST
   support the 'report-all' handling mode and MAY support other modes.

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

2.2.  Dependencies

   None

2.3.  Conformance

   Every NETCONF server SHOULD implement this capability.

2.4.  Capability Identifier

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

   The identifier MUST have a parameter: "basic-mode".  This indicates
   how the server reports default data in <rpc-reply> messages, in the
   case the client does not specify the required behavior in the <rpc>
   request.  The allowed values of this parameter are report-all, trim,
   explicit as listed in Section 1.2.

   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 modes that are supported beside the mode indicated
   in the basic parameter.  Possible modes are taken from the list in
   Section 1.2.

   In addition to these parameters, the identifier MUST have the YANG
   'module' and 'revision' parameters if the ietf-with-defaults YANG
   module is supported, as defined in section 5.6.4 of



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   [I-D.ietf-netmod-yang].

   Example:

   urn:ietf:params:netconf:capability:with-defaults:1.0?module=ietf-
   netconf-with-defaults&revision=2010-03-05&basic-mode=report-all

   urn:ietf:params:netconf:capability:with-defaults:1.0?module=ietf-
   netconf-with-defaults&revision=2010-03-05&basic-mode=report-all&
   also-supported=trim,explicit

2.5.  New Operations

   None

2.6.  Modifications to Existing Operations

   A new <with-defaults> XML [W3C.REC-xml-20001006] child element is
   added to the method-name element.  This is the element that indicates
   the type of the operation e.g. <get>, <get-config> or <copy-config>.
   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 the element.

   Allowed values of the with-defaults element are taken from the list
   in Section 1.2.  The allowed values are restricted to the values that
   the device indicates support for in the with-defaults capability in
   the basic and also-supported parameters.

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

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

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

   <copy-config> is only affected if the target of the operation is a
   URL.  If the target is a NETCONF datastore (running, candidate or
   startup) the capability has no effect; the with-defaults parameter,
   if present, SHALL be silently ignored.




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   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.

   The following example shows a <get-config> operation which is using
   the 'with-defaults' element.  The client is retrieving the
   'interfaces' object, defined in the example.com data model.  (In this
   simple example, the 'name' field is defined as the key, and the 'mtu'
   field is the only other data in the <interface> element).  The
   default value of mtu is '1500'.  The basic default handling for the
   server is "trim".  As the 'with-defaults' element has the value
   'report-all', the mtu is returned not just for eth0 but also for
   eth1.



































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     <rpc message-id="102"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get-config>
         <source>
            <running/>
         </source>
         <filter type="subtree">
           <interfaces xmlns="http://example.com/interfaces/1.2"/>
         </filter>
         <with-defaults
           xmlns="urn:ietf:params:netconf:capability:with-defaults:1.0">
           report-all
         </with-defaults>
       </get-config>
     </rpc>

     <rpc-reply message-id="102"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <interfaces xmlns="http://example.com/interfaces/1.2">
           <interface>
             <name>eth0</name>
             <mtu>8192</mtu>
           </interface>
           <interface>
             <name>eth1</name>
             <mtu>1500</mtu>
           </interface>
         </interfaces>
       </data>
     </rpc-reply>


                                 Figure 1

2.7.  Interactions with Other Capabilities

   None


3.  YANG Module

   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 implement this YANG module.




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   -- RFC Ed.: Insert license information for code as appropriate



 <CODE BEGINS> file="ietf-netconf-with-defaults.yang"

 module ietf-netconf-with-defaults {

    namespace "urn:ietf:params:netconf:capability:with-defaults:1.0";

    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



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      (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-05.txt

    revision 2010-03-05 {
      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 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 {



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        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.  IANA Considerations

   This document registers one capability identifier URN from the
   'Network Configuration Protocol [RFC4741] Capability URNs' registry,
   and registers the same URN for the NETCONF XML namespace in the "IETF
   XML registry" [RFC3688].  Note that the capability URN is compliant
   to [RFC4741] section 10.3.

   +---------------+---------------------------------------------------+
   | Index         | Capability Identifier                             |
   +---------------+---------------------------------------------------+
   | :with-default | urn:ietf:params:netconf:capability:with-defaults: |
   | s             | 1.0                                               |
   +---------------+---------------------------------------------------+


5.  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.  They only suppress data that can already be retrieved with
   the standard protocol operations, and do not add any data to the
   configuration database.





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6.  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.  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-11 (work in progress),
              February 2010.

   [W3C.REC-xml-20001006]
              Sperberg-McQueen, C., Maler, E., Paoli, J., and T. Bray,
              "Extensible Markup Language (XML) 1.0 (Second Edition)",
              World Wide Web Consortium FirstEdition REC-xml-20001006,
              October 2000,
              <http://www.w3.org/TR/2000/REC-xml-20001006>.


Appendix A.  Open Issues

   This section will be removed.  The open issues are closed in this
   revision of the draft, pending working group approval.

   Is the definition of defaults OK?  [The definition of explicitly set
   default data has been changed to 'explicitly set data', and now
   aligns with the YANG definition.]

   Shall we wait for YANG and 4741bis and make the YANG normative?
   [Yes.]



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   Shall we make with-defaults mandatory?  [No.  It is SHOULD, not
   MUST.]


Appendix B.  Change Log

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

B.1.  -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.

B.2.  00-01

   Changed value set of with-default capability and element

   Added version to URI

B.3.  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.4.  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.





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B.5.  03-04

   Clarifications

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

B.6.  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 RPC 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.


Authors' Addresses

   Andy Bierman
   InterWorking Labs
   303 Potrero Street, Suite 52
   Santa Cruz, CA  95060-2760
   USA

   Phone: +1 831 460 7010
   Email: andyb@iwl.com





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   Balazs Lengyel
   Ericsson
   Budapest,
   Hungary

   Email: balazs.lengyel@ericsson.com













































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