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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                                           Netconf Central
Intended status: Standards Track                              B. Lengyel
Expires: February 6, 2010                                       Ericsson
                                                         August 05, 2009


                  With-defaults capability for NETCONF
                  draft-ietf-netconf-with-defaults-03

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 February 6, 2010.

Copyright Notice

   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

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,



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   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 manger 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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1.1.  Requirements Notation  . . . . . . . . . . . . . . . .  3
       1.1.2.  NETCONF Terms  . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Current handling of default data . . . . . . . . . . . . .  4
   2.  With-defaults Capability . . . . . . . . . . . . . . . . . . .  4
     2.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Capability Identifier  . . . . . . . . . . . . . . . . . .  5
     2.4.  New Operations . . . . . . . . . . . . . . . . . . . . . .  5
     2.5.  Modifications to Existing Operations . . . . . . . . . . .  6
   3.  Interactions with Other Capabilities . . . . . . . . . . . . .  7
   4.  Data Model XSD . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Other default handling modes in the real world?  . . . . .  9
   8.  Appendix A -  YANG Module for with-defaults (non-normative)  .  9
   9.  Appendix B  -  Change Log  . . . . . . . . . . . . . . . . . . 12
     9.1.  02-03  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.2.  01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.3.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.4.  -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     11.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14












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1.  Introduction

   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.  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 theses 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

1.1.1.  Requirements Notation

   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].







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1.1.2.  NETCONF Terms

   o  Default data: Data that is set or used by the NETCONF server
      whenever the NETCONF client does not provide a specific value for
      the relevant data item.  Default values SHOULD be specified in
      documents describing the data models supported by the NETCONF
      server.

   o  Explicitly set default data: Data that is explicitly set by the
      NETCONF client to its default value.  Some servers MAY treat
      explicitly set default data as simple default data, as they may
      not be able to differentiate between them.

   In addition the following terms are defined in RFC 4741 and are not
   redefined here:
   o  application
   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 issue, NETCONF servers that do not implement
   the :with-defaults capability may or may not return default data in
   NETCONF <rpc-reply> messages.

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

   o  report-all: All default data is always reported.
   o  trim: Values are not reported if they match the default.
   o  explicit: Report values if they are explicitly set.  For state
      data this has the same effect as report-all


2.  With-defaults Capability






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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 servers 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.

2.2.  Dependencies

   None

2.3.  Capability Identifier

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

   The identifier MUST have a parameter: "basic".  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
   indicates what other default handling modes does the server support.
   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.

   Example:

   urn:ietf:params:netconf:capability:with-defaults:1.0?basic=report-all

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

2.4.  New Operations

   None







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2.5.  Modifications to Existing Operations

   A new <with-defaults> XML 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 the <with-defaults> element is not present, the server follows its
   basic behavior as indicated by the capability identifier's parameter
   see Section 2.3.

   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.

   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


3.  Interactions with Other Capabilities

   None


4.  Data Model XSD

   This section contains an XML Schema Definition
   [W3C.REC-xmlschema-2-20041028] which defines the XML syntax
   associated for the with-defaults XML element.





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

  <xs:annotation>
    <xs:documentation>
      Schema defining the with-defaults element.

      Organization: "IETF NETCONF Working Group"
      Contact Info: balazs.lengyel@ericsson.com
    </xs:documentation>
  </xs:annotation>

  <xs:attribute name="with-defaults" >
    <xs:simpleType>
      <xs:restriction base="xs:string">
        <xs:enumeration value="report-all"/>
        <xs:enumeration value="trim"/>
        <xs:enumeration value="explicit"/>
      </xs:restriction>
    </xs:simpleType>
  </xs:attribute>

</xs:schema>



5.  IANA Considerations

   This document registers one capability identifier URN from the
   "Network Configuration Protocol (NETCONF) 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 [NETCONF] section 10.3.

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







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6.  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 provides client controls 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.


7.  Open Issues

7.1.  Other default handling modes in the real world?

   Are there any other basic default handling modes out there we need to
   include?


8.  Appendix A -  YANG Module for with-defaults (non-normative)

   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].

 module ietf-netconf-with-defaults {

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

    prefix nwd;

    // for the uri data type
    import ietf-netconf { prefix nc; }

    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.

      Copyright (c) 2009 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, are permitted provided that the



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      following conditions are met:

      - Redistributions of source code must retain the above
        copyright notice, this list of conditions and the
        following disclaimer.

      - Redistributions in binary form must reproduce the above
        copyright notice, this list of conditions and the
        following disclaimer in the documentation and/or other
        materials provided with the distribution.

      - Neither the name of Internet Society, IETF or IETF
        Trust, nor the names of specific contributors, may be
        used to endorse or promote products derived from this
        software without specific prior written permission.

      THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
      CONTRIBUTORS 'AS IS' AND ANY EXPRESS OR IMPLIED
      WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
      WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
      PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
      OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
      INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
      (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
      GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
      BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
      LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
      OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      POSSIBILITY OF SUCH DAMAGE.

      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

    reference "RFC XXXX";

    // RFC Ed.: replace XXXX with actual RFC number and remove this note

    // reference "draft-ietf-netconf-with-defaults-03.txt";

    // RFC Ed.: remove the reference statement above and this note.

    contact
      "Send comments to the NETCONF WG mailing list.
       <netconf@ietf.org>";




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    revision 2009-07-01 {
      description
        "Initial version";
    }

    // with-defaults capability defined as a feature
    feature with-defaults {
        description
          "NETCONF :with-defaults capability;
           If the agent advertises the :with-defaults
           capability for a session, then this feature MUST
           also be enabled for that session.  Otherwise,
           this feature MUST NOT be enabled.";
        // RFC Ed.: replace XXXX with actual RFC number and
        // remove this note
        reference "RFC XXXX";
    }

    typedef with-defaults-mode-type {
       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 if they are explicitly set.
                 For state data this has the same effect
                 as report-all";
          }
      }
    }

    // extending the get-config operation
    augment /nc:get-config/nc:input {
        leaf with-defaults {
            type with-defaults-mode-type;
        }
    }

    // extending the get operation



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    augment /nc:get/nc:input {
        leaf with-defaults {
            type with-defaults-mode-type;
        }
    }

    // extending the copy-congig operation
    augment /nc:copy-config/nc:input {
        leaf with-defaults {
            type with-defaults-mode-type;
        }
    }

 }


9.  Appendix B  -  Change Log

9.1.  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.

9.2.  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.

9.3.  00-01

   Changed value set of with-default capability and element

   Added version to URI







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9.4.  -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.


10.  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.


11.  References

11.1.  Normative References

   [W3C.REC-xmlschema-2-20041028]
              Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
              Second Edition", World Wide Web Consortium
              Recommendation REC-xmlschema-2-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

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

   [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.

11.2.  Informative References

   [I-D.ietf-netmod-yang]
              Bjorklund, M., "YANG - A data modeling language for
              NETCONF", draft-ietf-netmod-yang-07 (work in progress),
              July 2009.

   [I-D.ietf-netconf-4741bis]
              Enns, R., Bjorklund, M., Schoenwaelder, J., and A.



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              Bierman, "NETCONF Configuration Protocol",
              draft-ietf-netconf-4741bis-01 (work in progress),
              July 2009.


Authors' Addresses

   Andy Bierman
   Netconf Central
   Simi Valley, CA
   USA

   Email: andy@netconfcentral.com


   Balazs Lengyel
   Ericsson
   Budapest,
   Hungary

   Email: balazs.lengyel@ericsson.com






























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