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Versions: (draft-lengyel-ngo-partial-lock) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 5717

NETCONF                                                       B. Lengyel
Internet-Draft                                                  Ericsson
Intended status: Standards Track                            M. Bjorklund
Expires: August 23, 2009                                  Tail-f Systems
                                                       February 19, 2009


                      Partial Lock RPC for NETCONF
                   draft-ietf-netconf-partial-lock-07

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 August 23, 2009.

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
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   to this document.

Abstract

   The NETCONF protocol defines the lock and unlock RPCs, used to lock



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   entire configuration datastores.  In some situations, a way to lock
   only parts of a configuration datastore is required.  This document
   defines a capability-based extension to the NETCONF protocol for
   locking portions of a configuration datastore.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Definition of Terms  . . . . . . . . . . . . . . . . . . .  3
   2.  Partial Locking Capability . . . . . . . . . . . . . . . . . .  3
     2.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  3
       2.1.1.  Usage Scenarios  . . . . . . . . . . . . . . . . . . .  4
     2.2.  Dependencies . . . . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Capability Identifier  . . . . . . . . . . . . . . . . . .  5
     2.4.  New Operations . . . . . . . . . . . . . . . . . . . . . .  5
       2.4.1.  <partial-lock> . . . . . . . . . . . . . . . . . . . .  6
       2.4.2.  <partial-unlock> . . . . . . . . . . . . . . . . . . . 10
     2.5.  Modifications to Existing Operations . . . . . . . . . . . 11
     2.6.  Interactions with Other Capabilities . . . . . . . . . . . 12
       2.6.1.  Candidate Configuration Capability . . . . . . . . . . 12
       2.6.2.  Confirmed Commit Capability  . . . . . . . . . . . . . 12
       2.6.3.  Distinct Startup Capability  . . . . . . . . . . . . . 12
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   5.  Appendix A  -  XML Schema for Partial Locking (normative)  . . 14
   6.  Appendix B  - YANG Module for Partial Locking
       (non-normative)  . . . . . . . . . . . . . . . . . . . . . . . 18
   7.  Appendix C - Usage Example - Reserving nodes for future
       editing (non-normative)  . . . . . . . . . . . . . . . . . . . 21
   8.  Appendix D  -  Change Log  . . . . . . . . . . . . . . . . . . 26
     8.1.  06-07  . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     8.2.  05-06  . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     8.3.  04-05  . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     8.4.  03-04  . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     8.5.  02-03  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     8.6.  01-02  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     8.7.  00-01  . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     8.8.  -00  . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 29
     10.2. Informative References . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30







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1.  Introduction

   The [NETCONF] protocol describes the lock and unlock operations that
   operate on entire configuration datastores.  Often, multiple
   management sessions need to be able to modify the configuration of a
   managed device in parallel.  In these cases, locking only parts of a
   configuration datastore is needed.  This document defines a
   capability based extension to the NETCONF protocol to support partial
   locking of NETCONF datastores using a mechanism based on the existing
   XPath filtering mechanisms.

1.1.  Definition of Terms

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

   Additionally the following terms are defined:

   o  Instance Identifier: an XPath expression identifying a specific
      node in the conceptual XML datastore.  It contains an absolute
      path expression in abbreviated syntax, where predicates are used
      only to specify values for nodes defined as keys to distinguish
      multiple instances.

   o  Scope of the lock: initially the set of nodes returned by the
      XPath expressions in a successful partial-lock operation.  The set
      might be modified if some of the nodes are deleted.

   o  Protected area: the set of nodes that are protected from
      modification by the lock.  This consist of nodes in the scope of
      the lock and nodes in subtrees under them.


2.  Partial Locking Capability

2.1.  Overview

   The :partial-lock capability indicates that the device supports the
   locking of its configuration with a more limited scope than a
   complete configuration datastore.  The scope to be locked is
   specified by using restricted or full XPath expressions.  Partial
   locking only affects configuration data.

   The system MUST ensure that configuration resources covered by the
   lock are not modified by other NETCONF or non-NETCONF management
   operations such as SNMP and the CLI.



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   The duration of the partial lock begins when the partial lock is
   granted and lasts until (1) either the corresponding <partial-unlock>
   operation succeeds or (2) the NETCONF session terminates.

   A NETCONF session MAY have multiple parts of one or more datastores
   (running, candidate, startup) locked using partial lock operations.

   The <partial-lock> operation returns a lock-id to identify each
   successfully acquired lock.

2.1.1.  Usage Scenarios

   In the following we describe a few scenarios for partial locking.
   While scenarios using the running datastore are seen as the most
   important, as an example a scenario involving the candidate datastore
   is also presented.  Besides the three described here, there are many
   other usage scenarios possible.

2.1.1.1.  Multiple managers handling the writable running datastore

   Multiple managers are handling the same NETCONF agent simultaneously.
   The agent is handled via the writable running datastore.  Each
   manager has his or her own task, which might involve the modification
   of overlapping sections of the datastore.

   After collecting and analyzing input and preparing the NETCONF
   operations off-line, the manager locks the areas that are important
   for his task using one single <partial-lock> operation.  The manager
   executes a number of <edit-config> operations to modify the
   configuration, then releases the partial-lock.  The lock should be
   held for only a short time (seconds rather then minutes).  The
   manager should collect all human input before locking anything.  As
   each manager locks only a part of the data model, usually multiple
   operators can execute the <edit-config> operations simultaneously.

2.1.1.2.  Multiple managers handling the writable running datastore,
          distinct management areas

   Multiple managers are handling the same NETCONF agent simultaneously.
   The agent is handled via the writable running datastore.  The agent's
   data model contains a number of well defined separate areas that can
   be configured without impacting other areas.  An example can be a
   server with multiple applications running on it, or a number of a
   network elements with a common NETCONF agent for management.

   Each manager has his or her own task, which does not involve the
   modification of overlapping sections of the datastore.




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   The manager locks his area with a <partial-lock> operation, uses a
   number of <edit-config> commands to modify it, later releases the
   lock.  As each manager has his functional area assigned to him, and
   he locks only that area, multiple managers can edit the configuration
   simultaneously.  Locks can be held for extended periods (minutes,
   hours), as this will not hinder other managers.

   This scenario assumes, that the global lock operation from [NETCONF]
   is not used.

2.1.1.3.  Multiple managers handling the candidate datastore in a semi-
          coordinated work mode

   Multiple managers are handling the same NETCONF agent simultaneously.
   The agent is handled via the candidate datastore.  Each manager has
   his or her own task which might involve the modification of
   overlapping sections of the datastore.

   After collecting and analyzing input and preparing the NETCONF
   operations off-line, the manager locks the areas that are important
   for his task using one single <partial-lock> operation in both the
   candidate and the running datastore.  He executes a number of <edit-
   config> operations to modify the configuration, then releases the
   partial-lock.  The lock should be held for only a short time (seconds
   rather then minutes).

   Operators coordinate with each other.  When all of them finish their
   tasks one of them orders commit.  If any of the operators are still
   working, and holds a lock, the commit will fail, and will need to be
   repeated after all managers finish.

2.2.  Dependencies

   The device MUST support restricted XPath expressions in the select
   element, as described in Section 2.4.1.  Optionally, if the :xpath
   capability is also supported (as defined in [NETCONF] chapter 8.9.
   XPath Capability), the device MUST also support using any XPath 1.0
   expression in the select element.

2.3.  Capability Identifier

   urn:ietf:params:netconf:capability:partial-lock:1.0

2.4.  New Operations







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2.4.1.  <partial-lock>

   The <partial-lock> operation allows the client to lock a portion of
   one or more datastores.  The portion to lock is specified with XPath
   expressions in the "select" elements and the list of datastores in
   the "target" elements in the <partial-lock> operation.  Each XPath
   expression MUST return a node set.

   When a NETCONF session holds a lock on a node, no other session or
   non-NETCONF mechanism of the system can change that node or any node
   in the hierarchy of nodes beneath it.

   Locking a node protects the node itself and the complete subtree
   under the node from modification by others.  The set of locked nodes
   is called the scope of the lock, while all the locked nodes and the
   nodes in the subtrees under them make up the protected area.

   In some situations it is desirable that the same set of nodes are
   locked in more than one datastore.  For example, if an interface is
   configured in the candidate datastore, it is dangerous for it to be
   configured by someone else in a possibly conflicting manner in the
   running datastore.  For this reason <partial-lock> allows the locking
   of the same sections of the management data in multiple datastores.

   The XPath expressions are evaluated only once at lock time.
   Thereafter, the scope of the lock is maintained as a set of nodes,
   i.e. the returned nodeset, and not by the XPath expression.  If the
   configuration data is later altered in a way that would make the
   original XPath expressions evaluate to a different set of nodes, this
   does not affect the scope of the partial lock.

   Let's say the agent's data model includes a list of users.  If the
   XPath expression in the partial lock operation covers all users at
   locking, the scope of the lock will be maintained as the list of
   "user" nodes at the time when the lock was granted.  If someone later
   creates a new user, this new user will not be included in the locked-
   nodes list created previously, the new user will not be locked.

   A <partial-lock> operation MUST be handled atomically by the NETCONF
   server.  The server either locks all requested parts of the
   datastore(s) or none.  If during the <partial-lock> operation one of
   the requested parts cannot be locked, the server MUST unlock all
   parts that have already been locked during that operation.

   If a node in the scope of the lock is deleted, it is removed from the
   scope of the lock, so any other session or non-NETCONF mechanism can
   recreate it.  If all nodes in the scope of the lock are deleted, the
   lock will still be present.  However, its scope will become empty



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   (since the lock will not cover any nodes).

   A NETCONF server MUST be able to grant multiple simultaneous partial
   locks to a single NETCONF session.  If the protected area of the
   individual locks overlaps, nodes in the common area MUST be protected
   until all of the locks are released.

   A partial lock operation MUST fail if:

   o  Any NETCONF session (including the current session) owns the
      global lock on any target datastore.

   o  Any part of the area to be protected is already locked (or
      protected by partial locking) by another management session,
      including other NETCONF sessions using <partial-lock> or any other
      non-NETCONF management method.

   o  The NETCONF server implements access control, and the locking user
      does not have sufficient access rights.  The exact handling of
      access rights is outside the scope of this document, but it is
      assumed that there is an access control system that MAY deny or
      allow the partial lock operation.

   The <partial-lock> operation is designed for simplicity, so when a
   partial lock is executed you get what you asked for: a set of nodes
   that are locked for writing.  As a consequence users must observe the
   following:

   o  Locking does not affect read operations.

   o  If part of a datastore is locked, this has no effect on any
      unlocked parts of the datastore.  If this is a problem (e.g.,
      changes depend on data values or nodes outside the protected part
      of the datastore), these nodes should be included in the protected
      area of the lock.

   o  Configuration data can be edited both inside and outside the
      protected area of a lock.  It is the responsibility of the NETCONF
      client application to lock all relevant parts of a datastore that
      are crucial for a specific management action.


   Note: The <partial-lock> operation does not modify the global <lock>
   operation defined in the base NETCONF Protocol [NETCONF].  If part of
   a datastore is already locked by <partial-lock>, then a global lock
   for that datastore MUST fail even if the global lock is requested by
   the NETCONF session that owns the partial lock.




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2.4.1.1.  Parameters, Result, Examples

   Parameters:

   target:  Name of one or more configuration datastores of which a part
       shall be locked.  If multiple datastores are specified the same
       select parameter(s) are evaluated for each of them.

   select:  One or more 'select' elements, each containing an XPath
       expression.  The XPath expression is evaluated in a context where
       the context node is the root of the server's conceptual data
       model, and the set of namespace declarations are those in scope
       on the select element.

       Each select expression is evaluated for each targeted datastore.

       The nodes returned from the select expressions are reported in
       the rpc-reply message.

       Note that if some of the requested nodes exist only in some of
       the targeted datastores, the lock is granted on different nodes
       in different datastores.

       Each select expression MUST return a node set, and at least one
       of the node sets for one of the specified datastores MUST be non-
       empty.

       If the device supports the :xpath capability, any valid XPath 1.0
       expression can be used.  If the device does not support the
       :xpath capability, the XPath expression MUST be limited to an
       Instance Identifier expression.  An Instance Identifier is an
       absolute path expression in abbreviated syntax, where predicates
       are used only to specify values for nodes defined as keys to
       distinguish multiple instances.

















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   Example: Lock virtual router 1 and interface eth1


    <nc:rpc
      xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
      xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
      message-id="135">
        <partial-lock>
            <target>
                <running/>
            </target>
            <select xmlns:rte="http://example.com/ns/route">
                /rte:routing/rte:virtualRouter[rte:routerName='router1']
            </select>
            <select xmlns:if="http://example.com/ns/interface">
                /if:interfaces/if:interface[if:id='eth1']
            </select>
         </partial-lock>
    </nc:rpc>

    <nc:rpc-reply
      xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
      xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
      message-id="135">
        <lock-id>127</lock-id>
        <running>
          <locked-node xmlns:rte="http://example.com/ns/route">
              /rte:routing/rte:virtualRouter[rte:routerName='router1']
          </locked-node>
          <locked-node xmlns:if="http://example.com/ns/interface">
              /if:interfaces/if:interface[if:id='eth1']
          </locked-node>
        </running>
    </nc:rpc-reply>


   Positive Response:

   If the device was able to satisfy the request, an <rpc-reply> is sent
   with a <lock-id> element (lock identifier) in the <rpc-reply>
   element.  A list of locked nodes per datastore is also returned in
   Instance Identifier format.

   Negative Response:

   If a lock is already held by another session on any node within the
   subtrees to be locked, the <error-tag> element is 'lock-denied' and
   the <error-info> element includes the <session-id> of the lock owner.



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   If the lock is held by a non-NETCONF session, a <session-id> of 0
   (zero) is included.  If needed the returned session-id may be used to
   <kill-session> the NETCONF session holding the lock.  The same error
   response is returned if the requesting session already holds the
   (global) lock for the same datastore.

   If any select expression is an invalid XPath expression, the <error-
   tag> is 'invalid-value'.

   If any select expression returns something other than a node set, the
   <error-tag> is 'invalid-value', and the <error-app-tag> is 'not-a-
   node-set'.

   If all the select expressions return an empty node set, the <error-
   tag> is 'operation-failed', and the <error-app-tag> is 'no-matches'.

   If any of the target datastors does not exist, the <error-tag> is
   'invalid-value', the <error-app-tag> is 'invalid-lock-specification'

   If the :xpath capability is not supported and the XPath expression is
   not an Instance Identifier, the <error-tag> is 'invalid-value', the
   <error-app-tag> is 'invalid-lock-specification'.

   If access control denies the partial lock, the <error-tag> is
   'access-denied'.


2.4.1.2.  Deadlock Avoidance

   As with most locking systems, it is possible that two management
   sessions trying to lock different parts of the configuration could
   become dead-locked.  To avoid this situation, clients should lock
   everything they need in one operation.  If locking fails, the client
   should back-off, release any previously acquired locks, and retry the
   procedure after waiting some randomized time interval.


2.4.2.  <partial-unlock>

   The operation unlocks the parts of the datastores that were
   previously locked using <partial-lock> during the same session.

   Parameters:

   lock-id:  Identity of the lock to be unlocked.  This lock-id MUST
       have been received as a response to a lock request by the manager
       during the current session, and MUST NOT have been sent in a
       previous unlock request.



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   Example: Unlock a previously created lock


      <nc:rpc xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
        xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
        message-id="136">
          <partial-unlock>
            <lock-id>127</lock-id>
          </partial-unlock>
      </nc:rpc>


   Positive Response:

   If the device was able to satisfy the request, an <rpc-reply> is sent
   that contains an <ok> element.  A positive response MUST be sent even
   if all of the locked parts of the datastore(s) have already been
   deleted.

   Negative Response:

   If the <lock-id> parameter does not identify a lock which is owned by
   the session, an 'invalid-value' error is returned.

2.5.  Modifications to Existing Operations

   A successful partial lock will cause a subsequent operation to fail
   if that attempts to modify nodes in the protected area of the lock
   and is executed in a NETCONF session other than the session that has
   been granted the lock.  The <error-tag> 'in-use' and the <error-app-
   tag> 'locked' is returned.  All operations that modify the datastore
   are affected, including: <edit-config>, <copy-config>, <delete-
   config>, <commit> and <discard-changes>.  If partial lock prevents
   <edit-config> modifying some data, but the operation includes the
   continue-on-error option, modification of other parts of the
   datastore, which are not protected by partial locking, might still
   succeed.

   If a datastore contains nodes locked by partial lock, this will cause
   the (global) <lock> operation to fail.  The <error-tag> element
   'lock-denied' and an <error-info> element including the <session-id>
   of the lock owner will be returned.  If the lock is held by a non-
   NETCONF session, a <session-id> of 0 (zero) is returned.

   All of these operations are affected only if they are targeting the
   same datastore.





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2.6.  Interactions with Other Capabilities

2.6.1.  Candidate Configuration Capability

   Partial locking of the candidate datastore can only be done if the
   :candidate capability is supported by the device.  Partial locking of
   the candidate datastore does not depend on whether the datastore was
   modified or not.

2.6.2.  Confirmed Commit Capability

   If:

   o  a partial lock is requested for the running datastore, and

   o  the NETCONF server implements the :confirmed-commit capability,
      and

   o  there was a recent confirmed <commit> operation where the
      confirming <commit> operation has not been received

   then the lock MUST be denied, because if the confirmation does not
   arrive, the running datastore MUST be rolled back to its state before
   the commit.  The NETCONF server might therefore need to modify the
   configuration.
   In this case the <error-tag> 'in-use' and the <error-app-tag>
   'outstanding-confirmed-commit' is returned.

2.6.3.  Distinct Startup Capability

   Partial locking of the startup datastore can only be done if the
   :startup capability is supported by the device.


3.  Security Considerations

   The same considerations are relevant as for the base NETCONF Protocol
   [NETCONF].  It is assumed that the <partial-lock> and <partial-
   unlock> RPCs are only allowed for an authenticated user after passing
   some access control mechanism.

   A lock (either a partial lock or a global lock) might prevent other
   users from configuring the system.  The following mechanisms are in
   place to prevent the misuse of this possibility:

      Only an authenticated and authorized user can request a partial
      lock.




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      The partial lock is automatically released when a session is
      terminated regardless of how the session ends.

      The <kill-session> operation makes it possible to terminate other
      users's sessions.

      The NETCONF server may log partial lock requests in an audit
      trail.



   A lock that is hung for some reason (e.g., a broken TCP connection
   that the server has not yet recognised) can be released using another
   NETCONF session by explicitly killing the session owning that lock
   using the <kill-session> operation.

   Partial locking is NOT an authorization mechanism; it SHOULD NOT be
   used to provide security or access control.  Partial locking SHOULD
   only be used as a mechanism for providing consistency when multiple
   managers are trying to configure the node.  It is vital that users
   easily understand the exact scope of a lock.  This is why the scope
   is determined when granting a lock and is not modified thereafter.


4.  IANA Considerations

   This document registers two URIs 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                             |
   +---------------+---------------------------------------------------+
   | :partial-lock | urn:ietf:params:netconf:capability:partial-lock:1 |
   |               | .0                                                |
   +---------------+---------------------------------------------------+

   URI: urn:ietf:params:xml:ns:netconf:partial-lock:1.0

   Registrant Contact: The IESG.

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









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5.  Appendix A  -  XML Schema for Partial Locking (normative)

   The following XML Schema defines the <partial-lock> and <partial-
   unlock> operations:

 <?xml version="1.0" encoding="UTF-8"?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
   xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
   targetNamespace="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
   elementFormDefault="qualified" attributeFormDefault="unqualified">

   <xs:annotation>
     <xs:documentation>
       Schema defining the partial-lock and unlock operations.
       organization "IETF NETCONF Working Group"

       contact
         Netconf Working Group
         Mailing list: netconf@ietf.org
         Web: http://www.ietf.org/html.charters/netconf-charter.html

         Balazs Lengyel
         balazs.lengyel@ericsson.com"

       revision 2009-02-19
         description Initial version, published as RFC yyyy.
 -- RFC Ed.: replace yyyy with actual RFC number and remove this note.
     </xs:documentation>
   </xs:annotation>

   <xs:import namespace="urn:ietf:params:xml:ns:netconf:base:1.0"
     schemaLocation="urn:ietf:params:xml:ns:netconf:base:1.0"/>

   <xs:simpleType name="lock-id-type">
     <xs:annotation>
       <xs:documentation>
         A number identifying a specific
         partial-lock granted to a session.
         It is allocated by the system, and SHOULD
         be used in the unlock operation.
       </xs:documentation>
     </xs:annotation>
     <xs:restriction base="xs:unsignedInt"/>
   </xs:simpleType>

   <xs:complexType name="configNameType"/>
   <xs:element name="config-name"



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       type="configNameType" abstract="true"/>
   <xs:element name="startup" type="configNameType"
       substitutionGroup="config-name"/>
   <xs:element name="candidate" type="configNameType"
       substitutionGroup="config-name"/>
   <xs:element name="running" type="configNameType"
       substitutionGroup="config-name"/>

   <xs:complexType name="partialLockType">
     <xs:annotation>
       <xs:documentation>
         A NETCONF operation that locks part of one or more datastores.
       </xs:documentation>
     </xs:annotation>
     <xs:complexContent>
       <xs:extension base="nc:rpcOperationType">
         <xs:sequence>
           <xs:element name="target" maxOccurs="unbounded">
             <xs:annotation>
               <xs:documentation>
                 A list of one or more datastore names for NETCONF.
                 Each target element MUST contain a different
                 datastore name.
               </xs:documentation>
             </xs:annotation>
             <xs:complexType>
               <xs:sequence>
                   <xs:element ref="config-name"/>
               </xs:sequence>
             </xs:complexType>
           </xs:element>
           <xs:element name="select" type="xs:string"
             maxOccurs="unbounded">
             <xs:annotation>
               <xs:documentation>
                 XPath expression that specifies the scope of the lock.
                 An Instance Identifier expression must be used unless
                 the :xpath capability is supported in which case any
                 XPath 1.0 expression is allowed.
               </xs:documentation>
             </xs:annotation>
           </xs:element>
         </xs:sequence>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>

   <xs:complexType name="partialUnLockType">



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     <xs:annotation>
       <xs:documentation>
         A NETCONF operation that releases a previously acquired
         partial-lock.
       </xs:documentation>
     </xs:annotation>
     <xs:complexContent>
       <xs:extension base="nc:rpcOperationType">
         <xs:sequence>
           <xs:element name="lock-id" type="lock-id-type">
             <xs:annotation>
               <xs:documentation>
                 Identifies the lock to be released. MUST be the value
                 received in the response to the partial-lock operation.
               </xs:documentation>
             </xs:annotation>
           </xs:element>
         </xs:sequence>
       </xs:extension>
     </xs:complexContent>
   </xs:complexType>

   <!-- <partial-lock> operation -->
   <xs:element name="partial-lock" type="partialLockType"
     substitutionGroup="nc:rpcOperation"/>

   <!-- <partial-unlock> operation -->
   <xs:element name="partial-unlock" type="partialUnLockType"
     substitutionGroup="nc:rpcOperation"/>

   <!-- reply to <partial-lock> -->

   <xs:complexType name="contentPartInPartialLockReplyType">
     <xs:annotation>
       <xs:documentation>
         The content of the reply to a successful
         partial-lock request MUST conform to this complex type.
       </xs:documentation>
     </xs:annotation>
     <xs:sequence>
       <xs:element name="lock-id" type="lock-id-type">
         <xs:annotation>
           <xs:documentation>
             Identifies the lock to be released. Must be the value
             received in the response to the partial-lock operation.
           </xs:documentation>
         </xs:annotation>
       </xs:element>



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       <xs:element name="running" minOccurs="0">
         <xs:annotation>
           <xs:documentation>
             List of locked nodes in the running datastore.
           </xs:documentation>
         </xs:annotation>
         <xs:complexType>
           <xs:sequence>
             <xs:element name="locked-node" type="xs:string"
               maxOccurs="unbounded">
             </xs:element>
           </xs:sequence>
         </xs:complexType>
       </xs:element>
       <xs:element name="candidate" minOccurs="0">
         <xs:annotation>
           <xs:documentation>
             List of locked nodes in the candidate datastore.
           </xs:documentation>
         </xs:annotation>
         <xs:complexType>
           <xs:sequence>
             <xs:element name="locked-node" type="xs:string"
               maxOccurs="unbounded">
             </xs:element>
           </xs:sequence>
         </xs:complexType>
       </xs:element>
       <xs:element name="startup" minOccurs="0">
         <xs:annotation>
           <xs:documentation>
             List of locked nodes in the startup datastore.
           </xs:documentation>
         </xs:annotation>
         <xs:complexType>
           <xs:sequence>
             <xs:element name="locked-node" type="xs:string"
               maxOccurs="unbounded">
             </xs:element>
           </xs:sequence>
         </xs:complexType>
       </xs:element>
     </xs:sequence>
   </xs:complexType>

 </xs:schema>





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6.  Appendix B  - YANG Module for Partial Locking (non-normative)

   The following YANG module defines the <partial-lock> and <partial-
   unlock> operations.  The YANG language is defined in
   [I-D.ietf-netmod-yang].

module ietf-netconf-partial-lock {

  namespace urn:ietf:params:xml:ns:netconf:partial-lock:1.0;
  prefix pl;

  organization "IETF Network Configuration (netconf) Working Group";

  contact
   "Netconf Working Group
    Mailing list: netconf@ietf.org
    Web: http://www.ietf.org/html.charters/netconf-charter.html

    Balazs Lengyel
    Ericsson
    balazs.lengyel@ericsson.com";

  description
   "This YANG module defines the <partial-lock> and
    <partial-unlock> operations.";

  revision 2009-02-19 {
    description
     "Initial version, published as RFC yyyy.";
     // RFC Ed.: replace yyyy with actual RFC number & remove this note.
  }

  typedef lock-id-type {
    type uint32;
    description
     "A number identifying a specific partial-lock granted to a session.
      It is allocated by the system, and SHOULD be used in the
      partial-unlock operation.";
  }

  rpc partial-lock {
    description
     "A NETCONF operation that locks part of one or more datastores.";
    input {
      list target {
        min-elements 1;
        description
         "A list of one or more datastore names.



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          Each list entry must contain a different datastore name.";
        choice datastore {
          leaf running   { type empty; }
          leaf candidate { type empty; }
          leaf startup   { type empty; }
        }
      }
      leaf-list select {
        type string;
        min-elements 1;
        description
         "XPath expression that specifies the scope of the lock.
          An Instance Identifier expression MUST be used unless the
          :xpath capability is supported, in which case any XPath 1.0
          expression is allowed.";
      }
    }
    output {
      leaf lock-id {
        type lock-id-type;
        description
         "Identifies the lock, if granted. The lock-id SHOULD be
          used in the partial-unlock rpc.";
      }
      container running {
        leaf-list locked-node {
          type instance-identifier;
          min-elements 1;
          description
           "List of locked nodes in the running datastore";
        }
      }
      container candidate {
        leaf-list locked-node {
          type instance-identifier;
          min-elements 1;
          description
           "List of locked nodes in the candidate datastore";
        }
      }
      container startup {
        leaf-list locked-node {
          type instance-identifier;
          min-elements 1;
          description
           "List of locked nodes in the startup datastore";
        }
      }



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    }
  }

  rpc partial-unlock {
    description
     "A NETCONF operation that releases a previously acquired
      partial-lock.";
    input {
      leaf lock-id {
        type lock-id-type;
        description
         "Identifies the lock to be released. MUST be the value
          received in the response to the partial-lock operation.";
      }
    }
  }
}


































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7.  Appendix C - Usage Example - Reserving nodes for future editing
    (non-normative)

   Partial lock cannot be used to lock non-existent nodes, which would
   effectively attempt to reserve them for future use.  To guarantee
   that a node cannot be created by some other session, the parent node
   should be locked, the top level node of the new subtree created, and
   then locked with another <partial-lock> operation.  After this, the
   lock on the parent node should be removed.

   In this chapter an example illustrating the above is given.

   We want to create <user> Joe under <users>, and start editing it.
   Editing might take a number of minutes.  We want to immediately lock
   Joe so no one will touch it before we are finished with the editing.

   We also want to minimize locking other parts of the datastore as
   multiple managers might be adding users near simultaneously.

   First we check what users are already defined.

   Step 1 - Read existing users


   <rpc message-id="101"
       xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <get-config>
       <source>
         <running/>
       </source>
       <filter type="subtree">
         <top xmlns="http://example.com/users">
           <users/>
         </top>
       </filter>
     </get-config>
   </rpc>



   The NETCONF server sends the following reply.










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   Step 2 - Receiving existing data


   <rpc-reply message-id="101"
        xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <top xmlns="http://example.com/users">
         <users>
           <user>
             <name>fred</name>
             <phone>8327</phone>
           </user>
         </users>
       </top>
     </data>
   </rpc-reply>



   We want to add the new user "Joe" and immediately lock him using
   partial locking.  The way to do this, is to first lock all <user>
   nodes by locking the <users> node.

   Step 3 - Lock users

   <nc:rpc
     xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
         message-id="102">
     <partial-lock>
       <target>
         <running/>
       </target>
       <select xmlns:usr="http://example.com/users">
         /usr:top/usr:users
       </select>
     </partial-lock>
   </nc:rpc>


   The NETCONF server grants the partial lock.  The scope of the lock
   includes only the <users> node.  The lock protects the <users> node
   and all <user> nodes below it from modification (by other sessions).








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   Step 4 - Receive lock

   <nc:rpc-reply
     xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
     message-id="102">
       <lock-id>1</lock-id>
       <running>
         <locked-node xmlns:usr="http://example.com/users">
             /usr:top/usr:users
         </locked-node>
       </running>
   </nc:rpc-reply>


   Next we create user Joe. Joe is protected by the lock received above,
   as it is under the sub-tree rooted at the <users> node.

   Step 5 - Create user Joe

   <rpc message-id="103"
        xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <edit-config>
       <target>
         <running/>
       </target>
       <config>
         <top xmlns:usr="http://example.com/users">
           <users>
             <user>
               <name>Joe</name>
             </user>
           </users>
         </top>
       </config>
     </edit-config>
   </rpc>


   We receive a positive reply to the <edit-config> (not shown).  Next
   we request a lock, that locks only <user> Joe, and release the lock
   on the <users> node.  This will allow other managers to create
   additional new users.








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   Step 6 - Lock user Joe

   <nc:rpc
     xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
         message-id="104">
     <partial-lock>
       <target>
         <running/>
       </target>
       <select xmlns:usr="http://example.com/users">
         /usr:top/usr:users/user[usr:name="Joe"]"
       </select>
     </partial-lock>
   </nc:rpc>


   The NETCONF server grants the partial lock.  The scope of this second
   lock includes only the <user> node with name Joe. The lock protects
   all data below this particular <user> node.

   Step 7 - Receive lock

   <nc:rpc-reply
     xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
     message-id="104">
       <lock-id>2</lock-id>
       <running>
         <locked-node xmlns:usr="http://example.com/users">
             /usr:top/usr:users/user[usr:name="Joe"]"
         </locked-node>
       </running>
   </nc:rpc-reply>


   The scope of the second lock is the <user> node Joe. It protects this
   <user> node and any data below it (e.g. phone number).  At this point
   of time these nodes are protected both by the first and second lock.
   Next we unlock the other <user>s and the <users> node, to allow other
   managers to work on them.  We still keep the second lock, so the
   <user> node Joe and the sub-tree below is still protected.









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   Step 8 - Release lock on <users>

   <nc:rpc xmlns="urn:ietf:params:xml:ns:netconf:partial-lock:1.0"
       xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
       message-id="105">
     <partial-unlock>
       <lock-id>1</lock-id>
     </partial-unlock>
   </nc:rpc>










































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8.  Appendix D  -  Change Log

8.1.  06-07

   Changed XSD and YANG to allow additional proprietary datastores to be
   locked.

8.2.  05-06

   Added usage example

   Clarified error messages

   Clarified interaction with edit-config continue-on-error

   Improved YANG: indentation, canonical order, contact info

   Added usage example in appendix C

   Synchronized YANG and XSD

8.3.  04-05

   Language and editorial updates

   all app-tags are with dashes without spaces

   Added usage scenarios

   Changed encoding

   Clarified definitions, separated scope of lock and protected area

8.4.  03-04

   Minor clarifications

   Added list of locked-nodes to the output of partial-lock.

   Added <target> wrapper around datastore names.

   Allowed atomic/one operation locking of datastore parts in multiple
   datastores.

   Improved English (hopefully)

   Removed the <data> element from rpc-reply following the text of
   rfc4741.



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8.5.  02-03

   Minor clarifications

   Same descriptions in XSD and YANG.

8.6.  01-02

   Made XSD normative

   Clarified that no specific access control is assumed.

   Clarified that non-existing nodes are NOT covered by the lock, even
   if they where existing and covered by the lock when it was originally
   granted.

   Some rewording

   Added app-tags for two of the error cases.

   Made YANG an informative reference

   Enhanced security considerations.

8.7.  00-01

   Added YANG module.

8.8.  -00

   Created from draft-lengyel-ngo-partial-lock-01.txt




















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9.  Acknowledgements

   Thanks to Andy Bierman, Sharon Chisholm, Phil Shafer , David
   Harrington, Mehmet Ersue, Wes Hardaker, Juergen Schoenwaelder and
   many other members of the NETCONF WG for providing important input to
   this document.













































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10.  References

10.1.  Normative References

   [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.

10.2.  Informative References

   [I-D.ietf-netmod-yang]
              Bjorklund, M., "YANG - A data modeling language for
              NETCONF", draft-ietf-netmod-yang-03 (work in progress),
              January 2009.
































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Authors' Addresses

   Balazs Lengyel
   Ericsson

   Email: balazs.lengyel@ericsson.com


   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com







































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