[Docs] [txt|pdf|xml] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

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: January 4, 2010                                        Ericsson
                                                           July 03, 2009


                  With-defaults capability for NETCONF
                  draft-ietf-netconf-with-defaults-02

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
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on January 4, 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 agent.  Part of this data is not set by the NETCONF manager,



Bierman & Lengyel        Expires January 4, 2010                [Page 1]

Internet-Draft                with-defaults                    July 2009


   but rather a default value is used.  In many situations the NETCONF
   manager has a priori knowledge about default data, so the NETCONF
   agent does not need to send it to the manager.  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 manager 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
   2.  With-defaults Capability . . . . . . . . . . . . . . . . . . .  4
     2.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  4
       2.1.1.  Basic handling of default data . . . . . . . . . . . .  4
     2.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Capability Identifier  . . . . . . . . . . . . . . . . . .  5
     2.4.  New Operations . . . . . . . . . . . . . . . . . . . . . .  5
     2.5.  Modifications to Existing Operations . . . . . . . . . . .  5
   3.  Interactions with Other Capabilities . . . . . . . . . . . . .  7
   4.  Data Model XSD . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  ietf-with-defaults YANG Module . . . . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Other default handling modes in the real world?  . . . . . 11
     8.2.  XSD needed?  . . . . . . . . . . . . . . . . . . . . . . . 11
     8.3.  YANG needed? . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  Appendix A  -  Change Log  . . . . . . . . . . . . . . . . . . 12
     9.1.  01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.2.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.3.  -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   11. Normative References . . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15













Bierman & Lengyel        Expires January 4, 2010                [Page 2]

Internet-Draft                with-defaults                    July 2009


1.  Introduction

   The NETCONF protocol defines ways to read configuration data from a
   NETCONF agent.  Part of this data is not set by the NETCONF manager,
   but rather a default value is used.  In many situations the NETCONF
   manager has a priori knowledge about default data, so the NETCONF
   agent does not need to send it to the manager.  A priori knowledge
   can be e.g., a document formally describing the data models supported
   by the NETCONF agent.

   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 manager 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 manager 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 manager 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].







Bierman & Lengyel        Expires January 4, 2010                [Page 3]

Internet-Draft                with-defaults                    July 2009


1.1.2.  NETCONF Terms

   o  Default data: Data that is set or used by the NETCONF agent
      whenever the NETCONF manager does not provide a specific value for
      the relevant data item.  Default values are often specified in
      documents describing the data models supported by the NETCONF
      agent.

   o  Explicitly set default data: Data that is explicitly set by the
      NETCONF manager to its default value.  Some agents 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  agent
   o  application
   o  manager
   o  operation
   o  RPC
   o  RPC request
   o  RPC response


2.  With-defaults Capability

2.1.  Overview

   The :with-defaults capability indicates that the NETCONF agent makes
   it possible for the NETCONF manager 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.  The
   NETCONF agent MUST also indicate its basic behavior, whether it sends
   default data in the absence of any specific request from the NETCONF
   manager.

2.1.1.  Basic 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



Bierman & Lengyel        Expires January 4, 2010                [Page 4]

Internet-Draft                with-defaults                    July 2009


   NETCONF <rpc-reply> messages.

   Different NETCONF agents 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

   NETCONF servers implementing the :with-defaults capability MUST
   support the 'report-all' 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 agent reports default data in <rpc-reply> messages, in the case
   the manager 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 2.1.1.

   The identifier MAY have another parameter: "also-supported".  This
   indicates what other default handling modes does the agent 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 2.1.1.

   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

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



Bierman & Lengyel        Expires January 4, 2010                [Page 5]

Internet-Draft                with-defaults                    July 2009


   operation e.g. <get>, <get-config> or <copy-config>.  If the <with-
   defaults> element is present, it controls the reporting of default
   data.  The agent 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 2.1.1.  The allowed values are restricted to the values
   that the device indicates support for in the with-defaults capability
   in the basic or also-supported parameters.

   If the <with-defaults> element is not present, the agent 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> operation which is using the
   'with-defaults' element.  The manager 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 agent is
   "trim".  As the 'with-defaults' element has the value 'report-all',
   the mtu is returned not just for eth0 but also for eth1.













Bierman & Lengyel        Expires January 4, 2010                [Page 6]

Internet-Draft                with-defaults                    July 2009


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











Bierman & Lengyel        Expires January 4, 2010                [Page 7]

Internet-Draft                with-defaults                    July 2009


   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns="urn:ietf:params:xml:ns:netconf:with-defaults:1.0"
     targetNamespace="urn:ietf:params:xml:ns:netconf: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.  ietf-with-defaults YANG Module

   This section is a placeholder at present.

   If the NETCONF workgroup documents basic NETCONF operations in a YANG
   module (YAM), this section will include a YAM to formally define the
   with-defaults related extension of these operations.  The section
   will be completed only after the 4741bis defines the basic ietf-
   netconf YAM.


6.  IANA Considerations

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



Bierman & Lengyel        Expires January 4, 2010                [Page 8]

Internet-Draft                with-defaults                    July 2009


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

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

   Registrant Contact: The IESG.

   XML: N/A, the requested URI is an XML namespace.







































Bierman & Lengyel        Expires January 4, 2010                [Page 9]

Internet-Draft                with-defaults                    July 2009


7.  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 manager 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.








































Bierman & Lengyel        Expires January 4, 2010               [Page 10]

Internet-Draft                with-defaults                    July 2009


8.  Open Issues

8.1.  Other default handling modes in the real world?

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

8.2.  XSD needed?

   Is the XSD needed?  Does it add any value, any clarity to the
   document?

   Proposal: XSD stays.

8.3.  YANG needed?

   See section ietf-with-defaults YANG Module.


































Bierman & Lengyel        Expires January 4, 2010               [Page 11]

Internet-Draft                with-defaults                    July 2009


9.  Appendix A  -  Change Log

9.1.  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.

9.2.  00-01

   Changed value set of with-default capability and element

   Added version to URI

9.3.  -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.





















Bierman & Lengyel        Expires January 4, 2010               [Page 12]

Internet-Draft                with-defaults                    July 2009


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.














































Bierman & Lengyel        Expires January 4, 2010               [Page 13]

Internet-Draft                with-defaults                    July 2009


11.  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.



































Bierman & Lengyel        Expires January 4, 2010               [Page 14]

Internet-Draft                with-defaults                    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



































Bierman & Lengyel        Expires January 4, 2010               [Page 15]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/