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rfc:rfc5717

Network Working Group B. Lengyel Request for Comments: 5717 Ericsson Category: Standards Track M. Bjorklund

                                                        Tail-f Systems
                                                         December 2009
        Partial Lock Remote Procedure Call (RPC) for NETCONF

Abstract

 The Network Configuration protocol (NETCONF) defines the lock and
 unlock Remote Procedure Calls (RPCs), used to lock 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.

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

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
 (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
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified

Lengyel & Bjorklund Standards Track [Page 1] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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.

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> . . . . . . . . . . . . . . . . . . . .  5
     2.4.2.  <partial-unlock> . . . . . . . . . . . . . . . . . . . 10
   2.5.  Modifications to Existing Operations . . . . . . . . . . . 10
   2.6.  Interactions with Other Capabilities . . . . . . . . . . . 11
     2.6.1.  Candidate Configuration Capability . . . . . . . . . . 11
     2.6.2.  Confirmed Commit Capability  . . . . . . . . . . . . . 11
     2.6.3.  Distinct Startup Capability  . . . . . . . . . . . . . 11
 3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
 4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
 5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
 6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
   6.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
   6.2.  Informative References . . . . . . . . . . . . . . . . . . 13
 Appendix A.  XML Schema for Partial Locking (Normative)  . . . . . 14
 Appendix B.  YANG Module for Partial Locking (Non-Normative) . . . 17
 Appendix C.  Usage Example - Reserving Nodes for Future
              Editing (Non-Normative) . . . . . . . . . . . . . . . 19

Lengyel & Bjorklund Standards Track [Page 2] RFC 5717 Partial Lock RPC for NETCONF December 2009

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 the NETCONF running datastore 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 by the session
    owning the lock.
 o  Protected area: the set of nodes that are protected from
    modification by the lock.  This set consists 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 and only the running
 datastore.  The candidate or the start-up datastore are not affected.

Lengyel & Bjorklund Standards Track [Page 3] RFC 5717 Partial Lock RPC for NETCONF December 2009

 The system MUST ensure that configuration resources covered by the
 lock are not modified by other NETCONF or non-NETCONF management
 operations such as Simple Network Management Protocol (SNMP) and the
 Command Line Interface (CLI).
 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 the running datastore
 locked using partial lock operations.
 The <partial-lock> operation returns a lock-id to identify each
 successfully acquired lock.  The lock-id is unique at any given time
 for a NETCONF server for all partial-locks granted to any NETCONF or
 non-NETCONF sessions.

2.1.1. Usage Scenarios

 In the following, we describe a few scenarios for partial locking.
 Besides the two described here, there are many other usage scenarios
 possible.

2.1.1.1. Multiple Managers Handling the Writable Running Datastore with

        Overlapping Sections
 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 the shortest possible time (e.g., seconds rather than
 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.

Lengyel & Bjorklund Standards Track [Page 4] RFC 5717 Partial Lock RPC for NETCONF December 2009

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
 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.
 The manager locks his area with a <partial-lock> operation, uses a
 number of <edit-config> commands to modify it, and 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 (e.g.,
 minutes, hours), as this will not hinder other managers.
 This scenario assumes that the global lock operation from [NETCONF]
 is not used.

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], Section 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

2.4.1. <partial-lock>

 The <partial-lock> operation allows the client to lock a portion of
 the running datastore.  The portion to lock is specified with XPath
 expressions in the "select" 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.

Lengyel & Bjorklund Standards Track [Page 5] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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.
 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 interface nodes.
 If the XPath expression in the partial-lock operation covers all
 interface nodes at locking, the scope of the lock will be maintained
 as the list of interface nodes at the time when the lock was granted.
 If someone later creates a new interface, this new interface will not
 be included in the locked-nodes list created previously so the new
 interface 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
 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 by the session owning
 the lock, 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 (since the lock will not cover
 any nodes).
 A NETCONF server that supports partial locking MUST be able to grant
 multiple simultaneous partial locks to a single NETCONF session.  If
 the protected area of the individual locks overlap, nodes in the
 common area MUST be protected until all of the overlapping locks are
 released.
 A <partial-lock> operation MUST fail if:
 o  Any NETCONF session (including the current session) owns the
    global lock on the running 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.

Lengyel & Bjorklund Standards Track [Page 6] RFC 5717 Partial Lock RPC for NETCONF December 2009

 o  The requesting user is not successfully authenticated.
 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 the running 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 the 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
 the running datastore is already locked by <partial-lock>, then a
 global lock for the running datastore MUST fail even if the global
 lock is requested by the NETCONF session that owns the partial lock.

2.4.1.1. Parameters, Results, Examples

 Parameters:
 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.
 The nodes returned from the select expressions are reported in the
     rpc-reply message.
 Each select expression MUST return a node set, and at least one of
     the node sets MUST be non-empty.

Lengyel & Bjorklund Standards Track [Page 7] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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.
 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>
          <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>
      <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>
  </nc:rpc-reply>
 Note: The XML Schema in [NETCONF] has a known bug that requires the
 <data> XML element in a <rpc-reply>.  This means that the above
 examples will not validate using the XML Schema found in [NETCONF].
 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 is also returned in Instance
 Identifier format.

Lengyel & Bjorklund Standards Track [Page 8] RFC 5717 Partial Lock RPC for NETCONF December 2009

 Negative Response:
 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 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'.  Access control SHOULD be checked before checking
 for conflicting locks to avoid giving out information about other
 sessions to an unauthorized client.
 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.
 If the lock is held by a non-NETCONF session, a <session-id> of 0
 (zero) SHOULD be included.  The same error response is returned if
 the requesting session already holds the (global) lock for the
 running datastore.
 If needed, the returned session-id may be used to <kill-session> the
 NETCONF session holding the lock.

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 deadlocked.  To avoid this situation, clients SHOULD lock
 everything they need in one operation.  If locking fails, the client
 MUST back-off, release any previously acquired locks, and SHOULD
 retry the procedure after waiting some randomized time interval.

Lengyel & Bjorklund Standards Track [Page 9] RFC 5717 Partial Lock RPC for NETCONF December 2009

2.4.2. <partial-unlock>

 The operation unlocks the parts of the running datastore that were
 previously locked using <partial-lock> during the same session.  The
 operation unlocks the parts that are covered by the lock identified
 by the lock-id parameter.  In case of multiple potentially
 overlapping locks, only the lock identified by the lock-id is
 removed.
 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.
 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 have already been
 deleted.
 Negative Response:
 If the <lock-id> parameter does not identify a lock that 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 operation 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

Lengyel & Bjorklund Standards Track [Page 10] RFC 5717 Partial Lock RPC for NETCONF December 2009

 running datastore are affected, including: <edit-config>, <copy-
 config>, <delete-config>, <commit>, and <discard-changes>.  If
 partial lock prevents <edit-config> from 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 the 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
 running datastore.

2.6. Interactions with Other Capabilities

2.6.1. Candidate Configuration Capability

 The candidate datastore cannot be locked using the <partial-lock>
 operation.

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

 The startup datastore cannot be locked using the <partial-lock>
 operation.

Lengyel & Bjorklund Standards Track [Page 11] RFC 5717 Partial Lock RPC for NETCONF December 2009

3. Security Considerations

 The same considerations are relevant as for the base NETCONF protocol
 [NETCONF]. <partial-lock> and <partial-unlock> RPCs MUST only be
 allowed for an authenticated user. <partial-lock> and <partial-
 unlock> RPCs SHOULD only be allowed for an authorized user.  However,
 as NETCONF access control is not standardized and not a mandatory
 part of a NETCONF implementation, it is strongly recommended, but
 OPTIONAL (although nearly all implementations include some kind of
 access control).
 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:
    A user, that is not successfully authenticated, MUST NOT be
    granted a partial lock.
    Only an authorized user SHOULD be able to request a partial lock.
    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' 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 recognized) 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 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.

Lengyel & Bjorklund Standards Track [Page 12] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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.

5. Acknowledgements

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

6. References

6.1. 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.

6.2. Informative References

 [YANG]     Bjorklund, M., "YANG - A data modeling language for
            NETCONF", Work in Progress, December 2009.

Lengyel & Bjorklund Standards Track [Page 13] RFC 5717 Partial Lock RPC for NETCONF December 2009

Appendix A. XML Schema for Partial Locking (Normative)

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

<?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 2009-10-19
          description Initial version, published as RFC 5717.
      </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>

Lengyel & Bjorklund Standards Track [Page 14] RFC 5717 Partial Lock RPC for NETCONF December 2009

  <xs:complexType name="partialLockType">
      <xs:annotation>
          <xs:documentation>
              A NETCONF operation that locks parts of
                the running datastore.
          </xs:documentation>
      </xs:annotation>
      <xs:complexContent>
          <xs:extension base="nc:rpcOperationType">
              <xs:sequence>
                  <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">
      <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>

Lengyel & Bjorklund Standards Track [Page 15] RFC 5717 Partial Lock RPC for NETCONF December 2009

      </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 a partial-lock operation.
              </xs:documentation>
            </xs:annotation>
          </xs:element>
          <xs:element name="locked-node" type="xs:string"
              maxOccurs="unbounded">
              <xs:annotation>
                  <xs:documentation>
                      List of locked nodes in the running datastore.
                  </xs:documentation>
              </xs:annotation>
          </xs:element>
      </xs:sequence>
  </xs:complexType>

</xs:schema>

 <CODE ENDS>

Lengyel & Bjorklund Standards Track [Page 16] RFC 5717 Partial Lock RPC for NETCONF December 2009

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 [YANG].
 <CODE BEGINS>

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 2009-10-19 {
  description
   "Initial version, published as RFC 5717.";
}
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 parts of the running datastore.";
  input {
    leaf-list select {
      type string;
      min-elements 1;
      description

Lengyel & Bjorklund Standards Track [Page 17] RFC 5717 Partial Lock RPC for NETCONF December 2009

       "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.";
    }
    leaf-list locked-node {
      type instance-identifier;
      min-elements 1;
      description
       "List of locked nodes in the running datastore";
    }
  }
}
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 a partial-lock operation.";
    }
  }
}

}

 <CODE ENDS>

Lengyel & Bjorklund Standards Track [Page 18] RFC 5717 Partial Lock RPC for NETCONF December 2009

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 section, 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 running 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.

Lengyel & Bjorklund Standards Track [Page 19] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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.
 Note that if we would lock all the <user> nodes using the select
 expression '/usr:top/usr:users/usr:user'; this would not lock the new
 user Joe, which we will create after locking.  So we rather have to
 lock 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>
     <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).

Lengyel & Bjorklund Standards Track [Page 20] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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>
     <locked-node xmlns:usr="http://example.com/users">
         /usr:top/usr:users
     </locked-node>
 </nc:rpc-reply>
 Next we create user Joe.  Joe is protected by the lock received
 above, as it is under the subtree 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.

Lengyel & Bjorklund Standards Track [Page 21] RFC 5717 Partial Lock RPC for NETCONF December 2009

 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>
     <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>
     <locked-node xmlns:usr="http://example.com/users">
         /usr:top/usr:users/user[usr:name="Joe"]"
     </locked-node>
 </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 subtree below is still protected.
 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>

Lengyel & Bjorklund Standards Track [Page 22] RFC 5717 Partial Lock RPC for NETCONF December 2009

Authors' Addresses

 Balazs Lengyel
 Ericsson
 EMail: balazs.lengyel@ericsson.com
 Martin Bjorklund
 Tail-f Systems
 EMail: mbj@tail-f.com

Lengyel & Bjorklund Standards Track [Page 23]

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