





Network Working Group                                       R. Enns, Ed.
Request for Comments: 4741                              Juniper Networks
Category: Standards Track                                  December 2006


                     NETCONF Configuration Protocol

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) The IETF Trust (2006).

Abstract

   The Network Configuration Protocol (NETCONF) defined in this document
   provides mechanisms to install, manipulate, and delete the
   configuration of network devices.  It uses an Extensible Markup
   Language (XML)-based data encoding for the configuration data as well
   as the protocol messages.  The NETCONF protocol operations are
   realized on top of a simple Remote Procedure Call (RPC) layer.
























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Table of Contents

   1. Introduction ....................................................5
      1.1. Protocol Overview ..........................................6
      1.2. Capabilities ...............................................7
      1.3. Separation of Configuration and State Data .................7
   2. Transport Protocol Requirements .................................8
      2.1. Connection-Oriented Operation ..............................9
      2.2. Authentication, Integrity, and Confidentiality .............9
      2.3. Authentication .............................................9
      2.4. Mandatory Transport Protocol ..............................10
   3. XML Considerations .............................................10
      3.1. Namespace .................................................10
      3.2. No Document Type Declarations .............................10
   4. RPC Model ......................................................10
      4.1. <rpc> Element .............................................10
      4.2. <rpc-reply> Element .......................................12
      4.3. <rpc-error> Element .......................................12
      4.4. <ok> Element ..............................................16
      4.5. Pipelining ................................................16
   5. Configuration Model ............................................16
      5.1. Configuration Datastores ..................................16
      5.2. Data Modeling .............................................17
   6. Subtree Filtering ..............................................17
      6.1. Overview ..................................................17
      6.2. Subtree Filter Components .................................18
           6.2.1. Namespace Selection ................................18
           6.2.2. Attribute Match Expressions ........................19
           6.2.3. Containment Nodes ..................................19
           6.2.4. Selection Nodes ....................................20
           6.2.5. Content Match Nodes ................................20
      6.3. Subtree Filter Processing .................................22
      6.4. Subtree Filtering Examples ................................22
           6.4.1. No Filter ..........................................22
           6.4.2. Empty Filter .......................................23
           6.4.3. Select the Entire <users> Subtree ..................23
           6.4.4. Select All <name> Elements within the
                  <users> Subtree ....................................25
           6.4.5. One Specific <user> Entry ..........................26
           6.4.6. Specific Elements from a Specific <user> Entry .....27
           6.4.7. Multiple Subtrees ..................................28
           6.4.8. Elements with Attribute Naming .....................29
   7. Protocol Operations ............................................31
      7.1. <get-config> ..............................................31
      7.2. <edit-config> .............................................34
      7.3. <copy-config> .............................................39
      7.4. <delete-config> ...........................................41
      7.5. <lock> ....................................................42



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      7.6. <unlock> ..................................................44
      7.7. <get> .....................................................45
      7.8. <close-session> ...........................................47
      7.9. <kill-session> ............................................48
   8. Capabilities ...................................................49
      8.1. Capabilities Exchange .....................................49
      8.2. Writable-Running Capability ...............................50
           8.2.1. Description ........................................50
           8.2.2. Dependencies .......................................50
           8.2.3. Capability Identifier ..............................50
           8.2.4. New Operations .....................................51
           8.2.5. Modifications to Existing Operations ...............51
      8.3. Candidate Configuration Capability ........................51
           8.3.1. Description ........................................51
           8.3.2. Dependencies .......................................52
           8.3.3. Capability Identifier ..............................52
           8.3.4. New Operations .....................................52
           8.3.5. Modifications to Existing Operations ...............53
      8.4. Confirmed Commit Capability ...............................55
           8.4.1. Description ........................................55
           8.4.2. Dependencies .......................................55
           8.4.3. Capability Identifier ..............................56
           8.4.4. New Operations .....................................56
           8.4.5. Modifications to Existing Operations ...............56
      8.5. Rollback on Error Capability ..............................57
           8.5.1. Description ........................................57
           8.5.2. Dependencies .......................................57
           8.5.3. Capability Identifier ..............................57
           8.5.4. New Operations .....................................57
           8.5.5. Modifications to Existing Operations ...............57
      8.6. Validate Capability .......................................58
           8.6.1. Description ........................................58
           8.6.2. Dependencies .......................................58
           8.6.3. Capability Identifier ..............................58
           8.6.4. New Operations .....................................58
      8.7. Distinct Startup Capability ...............................60
           8.7.1. Description ........................................60
           8.7.2. Dependencies .......................................60
           8.7.3. Capability Identifier ..............................60
           8.7.4. New Operations .....................................60
           8.7.5. Modifications to Existing Operations ...............60
      8.8. URL Capability ............................................61
           8.8.1. Description ........................................61
           8.8.2. Dependencies .......................................61
           8.8.3. Capability Identifier ..............................62
           8.8.4. New Operations .....................................62
           8.8.5. Modifications to Existing Operations ...............62




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      8.9. XPath Capability ..........................................63
           8.9.1. Description ........................................63
           8.9.2. Dependencies .......................................63
           8.9.3. Capability Identifier ..............................63
           8.9.4. New Operations .....................................63
           8.9.5. Modifications to Existing Operations ...............63
   9. Security Considerations ........................................64
   10. IANA Considerations ...........................................66
      10.1. NETCONF XML Namespace ....................................66
      10.2. NETCONF XML Schema .......................................66
      10.3. NETCONF Capability URNs ..................................66
   11. Authors and Acknowledgements ..................................68
   12. References ....................................................68
      12.1. Normative References .....................................68
      12.2. Informative References ...................................69
   Appendix A. NETCONF Error List ....................................70
   Appendix B. XML Schema for NETCONF RPC and Protocol Operations ....74
   Appendix C. Capability Template ...................................86
      C.1. capability-name (template) ................................86
           C.1.1. Overview ...........................................86
           C.1.2. Dependencies .......................................86
           C.1.3. Capability Identifier ..............................86
           C.1.4. New Operations .....................................86
           C.1.5. Modifications to Existing Operations ...............86
           C.1.6. Interactions with Other Capabilities ...............86
   Appendix D.  Configuring Multiple Devices with NETCONF ............87
      D.1. Operations on Individual Devices ..........................87
           D.1.1. Acquiring the Configuration Lock ...................87
           D.1.2. Loading the Update .................................88
           D.1.3. Validating the Incoming Configuration ..............89
           D.1.4. Checkpointing the Running Configuration ............89
           D.1.5. Changing the Running Configuration .................90
           D.1.6. Testing the New Configuration ......................91
           D.1.7. Making the Change Permanent ........................91
           D.1.8. Releasing the Configuration Lock ...................92
      D.2. Operations on Multiple Devices ............................92
   Appendix E. Deferred Features .....................................93














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1.  Introduction

   The NETCONF protocol defines a simple mechanism through which a
   network device can be managed, configuration data information can be
   retrieved, and new configuration data can be uploaded and
   manipulated.  The protocol allows the device to expose a full, formal
   application programming interface (API).  Applications can use this
   straightforward API to send and receive full and partial
   configuration data sets.

   The NETCONF protocol uses a remote procedure call (RPC) paradigm.  A
   client encodes an RPC in XML [1] and sends it to a server using a
   secure, connection-oriented session.  The server responds with a
   reply encoded in XML.  The contents of both the request and the
   response are fully described in XML DTDs or XML schemas, or both,
   allowing both parties to recognize the syntax constraints imposed on
   the exchange.

   A key aspect of NETCONF is that it allows the functionality of the
   management protocol to closely mirror the native functionality of the
   device.  This reduces implementation costs and allows timely access
   to new features.  In addition, applications can access both the
   syntactic and semantic content of the device's native user interface.

   NETCONF allows a client to discover the set of protocol extensions
   supported by a server.  These "capabilities" permit the client to
   adjust its behavior to take advantage of the features exposed by the
   device.  The capability definitions can be easily extended in a
   noncentralized manner.  Standard and non-standard capabilities can be
   defined with semantic and syntactic rigor.  Capabilities are
   discussed in Section 8.

   The NETCONF protocol is a building block in a system of automated
   configuration.  XML is the lingua franca of interchange, providing a
   flexible but fully specified encoding mechanism for hierarchical
   content.  NETCONF can be used in concert with XML-based
   transformation technologies, such as XSLT [8], to provide a system
   for automated generation of full and partial configurations.  The
   system can query one or more databases for data about networking
   topologies, links, policies, customers, and services.  This data can
   be transformed using one or more XSLT scripts from a task-oriented,
   vendor-independent data schema into a form that is specific to the
   vendor, product, operating system, and software release.  The
   resulting data can be passed to the device using the NETCONF
   protocol.






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   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 RFC 2119 [3].

1.1.  Protocol Overview

   NETCONF uses a simple RPC-based mechanism to facilitate communication
   between a client and a server.  The client can be a script or
   application typically running as part of a network manager.  The
   server is typically a network device.  The terms "device" and
   "server" are used interchangeably in this document, as are "client"
   and "application".

   A NETCONF session is the logical connection between a network
   administrator or network configuration application and a network
   device.  A device MUST support at least one NETCONF session and
   SHOULD support multiple sessions.  Global configuration attributes
   can be changed during any authorized session, and the effects are
   visible in all sessions.  Session-specific attributes affect only the
   session in which they are changed.

   NETCONF can be conceptually partitioned into four layers:

              Layer                      Example
         +-------------+      +-----------------------------+
     (4) |   Content   |      |     Configuration data      |
         +-------------+      +-----------------------------+
                |                           |
         +-------------+      +-----------------------------+
     (3) | Operations  |      | <get-config>, <edit-config> |
         +-------------+      +-----------------------------+
                |                           |
         +-------------+      +-----------------------------+
     (2) |     RPC     |      |    <rpc>, <rpc-reply>       |
         +-------------+      +-----------------------------+
                |                           |
         +-------------+      +-----------------------------+
     (1) |  Transport  |      |   BEEP, SSH, SSL, console   |
         |   Protocol  |      |                             |
         +-------------+      +-----------------------------+

   1.  The transport protocol layer provides a communication path
       between the client and server.  NETCONF can be layered over any
       transport protocol that provides a set of basic requirements.
       Section 2 discusses these requirements.

   2.  The RPC layer provides a simple, transport-independent framing
       mechanism for encoding RPCs.  Section 4 documents this protocol.



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   3.  The operations layer defines a set of base operations invoked as
       RPC methods with XML-encoded parameters.  Section 7 details the
       list of base operations.

   4.  The content layer is outside the scope of this document.  Given
       the current proprietary nature of the configuration data being
       manipulated, the specification of this content depends on the
       NETCONF implementation.  It is expected that a separate effort to
       specify a standard data definition language and standard content
       will be undertaken.

1.2.  Capabilities

   A NETCONF capability is a set of functionality that supplements the
   base NETCONF specification.  The capability is identified by a
   uniform resource identifier (URI).  These URIs should follow the
   guidelines as described in Section 8.

   Capabilities augment the base operations of the device, describing
   both additional operations and the content allowed inside operations.
   The client can discover the server's capabilities and use any
   additional operations, parameters, and content defined by those
   capabilities.

   The capability definition may name one or more dependent
   capabilities.  To support a capability, the server MUST support any
   capabilities upon which it depends.

   Section 8 defines the capabilities exchange that allows the client to
   discover the server's capabilities.  Section 8 also lists the set of
   capabilities defined in this document.

   Additional capabilities can be defined at any time in external
   documents, allowing the set of capabilities to expand over time.
   Standards bodies may define standardized capabilities, and
   implementations may define proprietary ones.  A capability URI MUST
   sufficiently distinguish the naming authority to avoid naming
   collisions.

1.3.  Separation of Configuration and State Data

   The information that can be retrieved from a running system is
   separated into two classes, configuration data and state data.
   Configuration data is the set of writable data that is required to
   transform a system from its initial default state into its current
   state.  State data is the additional data on a system that is not





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   configuration data such as read-only status information and collected
   statistics.  When a device is performing configuration operations, a
   number of problems would arise if state data were included:

   o  Comparisons of configuration data sets would be dominated by
      irrelevant entries such as different statistics.

   o  Incoming data could contain nonsensical requests, such as attempts
      to write read-only data.

   o  The data sets would be large.

   o  Archived data could contain values for read-only data items,
      complicating the processing required to restore archived data.

   To account for these issues, the NETCONF protocol recognizes the
   difference between configuration data and state data and provides
   operations for each.  The <get-config> operation retrieves
   configuration data only, while the <get> operation retrieves
   configuration and state data.

   Note that the NETCONF protocol is focused on the information required
   to get the device into its desired running state.  The inclusion of
   other important, persistent data is implementation specific.  For
   example, user files and databases are not treated as configuration
   data by the NETCONF protocol.

   If a local database of user authentication data is stored on the
   device, whether it is included in configuration data is an
   implementation-dependent matter.

2.  Transport Protocol Requirements

   NETCONF uses an RPC-based communication paradigm.  A client sends a
   series of one or more RPC request operations, which cause the server
   to respond with a corresponding series of RPC replies.

   The NETCONF protocol can be layered on any transport protocol that
   provides the required set of functionality.  It is not bound to any
   particular transport protocol, but allows a mapping to define how it
   can be implemented over any specific protocol.

   The transport protocol MUST provide a mechanism to indicate the
   session type (client or server) to the NETCONF protocol layer.

   This section details the characteristics that NETCONF requires from
   the underlying transport protocol.




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2.1.  Connection-Oriented Operation

   NETCONF is connection-oriented, requiring a persistent connection
   between peers.  This connection must provide reliable, sequenced data
   delivery.

   NETCONF connections are long-lived, persisting between protocol
   operations.  This allows the client to make changes to the state of
   the connection that will persist for the lifetime of the connection.
   For example, authentication information specified for a connection
   remains in effect until the connection is closed.

   In addition, resources requested from the server for a particular
   connection MUST be automatically released when the connection closes,
   making failure recovery simpler and more robust.  For example, when a
   lock is acquired by a client, the lock persists until either it is
   explicitly released or the server determines that the connection has
   been terminated.  If a connection is terminated while the client
   holds a lock, the server can perform any appropriate recovery.  The
   lock operation is further discussed in Section 7.5.

2.2.  Authentication, Integrity, and Confidentiality

   NETCONF connections must provide authentication, data integrity, and
   confidentiality.  NETCONF depends on the transport protocol for this
   capability.  A NETCONF peer assumes that appropriate levels of
   security and confidentiality are provided independently of this
   document.  For example, connections may be encrypted in TLS [9] or
   SSH [10], depending on the underlying protocol.

2.3.  Authentication

   NETCONF connections must be authenticated.  The transport protocol is
   responsible for authentication.  The peer assumes that the
   connection's authentication information has been validated by the
   underlying protocol using sufficiently trustworthy mechanisms and
   that the peer's identity has been sufficiently proven.

   One goal of NETCONF is to provide a programmatic interface to the
   device that closely follows the functionality of the device's native
   interface.  Therefore, it is expected that the underlying protocol
   uses existing authentication mechanisms defined by the device.  For
   example, a device that supports RADIUS [11] should allow the use of
   RADIUS to authenticate NETCONF sessions.

   The authentication process should result in an identity whose
   permissions are known to the device.  These permissions MUST be
   enforced during the remainder of the NETCONF session.



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2.4.  Mandatory Transport Protocol

   A NETCONF implementation MUST support the SSH transport protocol
   mapping [4].

3.  XML Considerations

   XML serves as the encoding format for NETCONF, allowing complex
   hierarchical data to be expressed in a text format that can be read,
   saved, and manipulated with both traditional text tools and tools
   specific to XML.

   This section discusses a small number of XML-related considerations
   pertaining to NETCONF.

3.1.  Namespace

   All NETCONF protocol elements are defined in the following namespace:

      urn:ietf:params:xml:ns:netconf:base:1.0

   NETCONF capability names MUST be URIs [5].  NETCONF capabilities are
   discussed in Section 8.

3.2.  No Document Type Declarations

   Document type declarations MUST NOT appear in NETCONF content.

4.  RPC Model

   The NETCONF protocol uses an RPC-based communication model.  NETCONF
   peers use <rpc> and <rpc-reply> elements to provide transport
   protocol-independent framing of NETCONF requests and responses.

4.1.  <rpc> Element

   The <rpc> element is used to enclose a NETCONF request sent from the
   client to the server.

   The <rpc> element has a mandatory attribute "message-id", which is an
   arbitrary string chosen by the sender of the RPC that will commonly
   encode a monotonically increasing integer.  The receiver of the RPC
   does not decode or interpret this string but simply saves it to be
   used as a "message-id" attribute in any resulting <rpc-reply>
   message.  For example:






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       <rpc message-id="101"
            xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <some-method>
           <!-- method parameters here... -->
         </some-method>
       </rpc>

   If additional attributes are present in an <rpc> element, a NETCONF
   peer MUST return them unmodified in the <rpc-reply> element.

   The name and parameters of an RPC are encoded as the contents of the
   <rpc> element.  The name of the RPC is an element directly inside the
   <rpc> element, and any parameters are encoded inside this element.

   The following example invokes a method called <my-own-method>, which
   has two parameters, <my-first-parameter>, with a value of "14", and
   <another-parameter>, with a value of "fred":

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <my-own-method xmlns="http://example.net/me/my-own/1.0">
         <my-first-parameter>14</my-first-parameter>
         <another-parameter>fred</another-parameter>
       </my-own-method>
     </rpc>

   The following example invokes a <rock-the-house> method with a
   <zip-code> parameter of "27606-0100":

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rock-the-house xmlns="http://example.net/rock/1.0">
         <zip-code>27606-0100</zip-code>
       </rock-the-house>
     </rpc>

   The following example invokes the NETCONF <get> method with no
   parameters:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get/>
     </rpc>








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4.2.  <rpc-reply> Element

   The <rpc-reply> message is sent in response to an <rpc> operation.

   The <rpc-reply> element has a mandatory attribute "message-id", which
   is equal to the "message-id" attribute of the <rpc> for which this is
   a response.

   A NETCONF peer MUST also return any additional attributes included in
   the <rpc> element unmodified in the <rpc-reply> element.

   The response name and response data are encoded as the contents of
   the <rpc-reply> element.  The name of the reply is an element
   directly inside the <rpc-reply> element, and any data is encoded
   inside this element.

   For example:

   The following <rpc> element invokes the NETCONF <get> method and
   includes an additional attribute called "user-id".  Note that the
   "user-id" attribute is not in the NETCONF namespace.  The returned
   <rpc-reply> element returns the "user-id" attribute, as well as the
   requested content.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
          xmlns:ex="http://example.net/content/1.0"
          ex:user-id="fred">
       <get/>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
          xmlns:ex="http://example.net/content/1.0"
          ex:user-id="fred">
       <data>
         <!-- contents here... -->
       </data>
     </rpc-reply>

4.3.  <rpc-error> Element

   The <rpc-error> element is sent in <rpc-reply> messages if an error
   occurs during the processing of an <rpc> request.

   If a server encounters multiple errors during the processing of an
   <rpc> request, the <rpc-reply> MAY contain multiple <rpc-error>
   elements.  However, a server is not required to detect or report more



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   than one <rpc-error> element, if a request contains multiple errors.
   A server is not required to check for particular error conditions in
   a specific sequence.  A server MUST return an <rpc-error> element if
   any error conditions occur during processing and SHOULD return an
   <rpc-error> element if any warning conditions occur during
   processing.

   A server MUST NOT return application-level- or data-model-specific
   error information in an <rpc-error> element for which the client does
   not have sufficient access rights.

   The <rpc-error> element includes the following information:

   error-type: Defines the conceptual layer that the error occurred.
      Enumeration.  One of:

      *  transport

      *  rpc

      *  protocol

      *  application

   error-tag: Contains a string identifying the error condition.  See
      Appendix A for allowed values.

   error-severity: Contains a string identifying the error severity, as
      determined by the device.  One of:

      *  error

      *  warning

   error-app-tag: Contains a string identifying the data-model-specific
      or implementation-specific error condition, if one exists.  This
      element will not be present if no appropriate application error
      tag can be associated with a particular error condition.

   error-path: Contains the absolute XPath [2] expression identifying
      the element path to the node that is associated with the error
      being reported in a particular rpc-error element.  This element
      will not be present if no appropriate payload element can be
      associated with a particular error condition, or if the
      'bad-element' QString returned in the 'error-info' container is
      sufficient to identify the node associated with the error.  When





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      the XPath expression is interpreted, the set of namespace
      declarations are those in scope on the rpc-error element,
      including the default namespace.

   error-message: Contains a string suitable for human display that
      describes the error condition.  This element will not be present
      if no appropriate message is provided for a particular error
      condition.  This element SHOULD include an xml:lang attribute as
      defined in [1] and discussed in [12].

   error-info: Contains protocol- or data-model-specific error content.
      This element will not be present if no such error content is
      provided for a particular error condition.  The list in Appendix A
      defines any mandatory error-info content for each error.  After
      any protocol-mandated content, a data model definition may mandate
      that certain application-layer error information be included in
      the error-info container.  An implementation may include
      additional elements to provide extended and/or implementation-
      specific debugging information.

   Appendix A enumerates the standard NETCONF errors.

   Example:

      An error is returned if an <rpc> element is received without a
      message-id attribute.  Note that only in this case is it
      acceptable for the NETCONF peer to omit the message-id attribute
      in the <rpc-reply> element.

     <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get-config>
         <source>
           <running/>
         </source>
       </get-config>
     </rpc>

     <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rpc-error>
         <error-type>rpc</error-type>
         <error-tag>missing-attribute</error-tag>
         <error-severity>error</error-severity>
         <error-info>
           <bad-attribute>message-id</bad-attribute>
           <bad-element>rpc</bad-element>
         </error-info>
       </rpc-error>
     </rpc-reply>



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      The following <rpc-reply> illustrates the case of returning
      multiple <rpc-error> elements.

      Note that the data models used in the examples in this section use
      the <name> element to distinguish between multiple instances of
      the <interface> element.

     <rpc-reply message-id="101"
       xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
       xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rpc-error>
         <error-type>application</error-type>
         <error-tag>invalid-value</error-tag>
         <error-severity>error</error-severity>
         <error-message xml:lang="en">
           MTU value 25000 is not within range 256..9192
         </error-message>
         <error-info>
           <top xmlns="http://example.com/schema/1.2/config">
             <interface>
               <name>Ethernet0/0</name>
               <mtu>25000</mtu>
             </interface>
           </top>
         </error-info>
       </rpc-error>
       <rpc-error>
         <error-type>application</error-type>
         <error-tag>invalid-value</error-tag>
         <error-severity>error</error-severity>
         <error-message xml:lang="en">
           Invalid IP address for interface Ethernet1/0
         </error-message>
         <error-info>
           <top xmlns="http://example.com/schema/1.2/config">
             <interface xc:operation="replace">
               <name>Ethernet1/0</name>
               <address>
                 <name>1.4</name>
                 <prefix-length>24</prefix-length>
               </address>
             </interface>
           </top>
         </error-info>
       </rpc-error>
     </rpc-reply>





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4.4.  <ok> Element

   The <ok> element is sent in <rpc-reply> messages if no errors or
   warnings occurred during the processing of an <rpc> request.  For
   example:

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

4.5.  Pipelining

   NETCONF <rpc> requests MUST be processed serially by the managed
   device.  Additional <rpc> requests MAY be sent before previous ones
   have been completed.  The managed device MUST send responses only in
   the order the requests were received.

5.  Configuration Model

   NETCONF provides an initial set of operations and a number of
   capabilities that can be used to extend the base.  NETCONF peers
   exchange device capabilities when the session is initiated as
   described in Section 8.1.

5.1.  Configuration Datastores

   NETCONF defines the existence of one or more configuration datastores
   and allows configuration operations on them.  A configuration
   datastore is defined as the complete set of configuration data that
   is required to get a device from its initial default state into a
   desired operational state.  The configuration datastore does not
   include state data or executive commands.

   Only the <running> configuration datastore is present in the base
   model.  Additional configuration datastores may be defined by
   capabilities.  Such configuration datastores are available only on
   devices that advertise the capabilities.

   o  Running: The complete configuration currently active on the
      network device.  Only one configuration datastore of this type
      exists on the device, and it is always present.  NETCONF protocol
      operations refer to this datastore using the <running> element.

   The capabilities in Sections 8.3 and 8.7 define the <candidate> and
   <startup> configuration datastores, respectively.





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5.2.  Data Modeling

   Data modeling and content issues are outside the scope of the NETCONF
   protocol.  An assumption is made that the device's data model is
   well-known to the application and that both parties are aware of
   issues such as the layout, containment, keying, lookup, replacement,
   and management of the data, as well as any other constraints imposed
   by the data model.

   NETCONF carries configuration data inside the <config> element that
   is specific to device's data model.  The protocol treats the contents
   of that element as opaque data.  The device uses capabilities to
   announce the set of data models that the device implements.  The
   capability definition details the operation and constraints imposed
   by data model.

   Devices and managers may support multiple data models, including both
   standard and proprietary data models.

6.  Subtree Filtering

6.1.  Overview

   XML subtree filtering is a mechanism that allows an application to
   select particular XML subtrees to include in the <rpc-reply> for a
   <get> or <get-config> operation.  A small set of filters for
   inclusion, simple content exact-match, and selection is provided,
   which allows some useful, but also very limited, selection
   mechanisms.  The agent does not need to utilize any data-model-
   specific semantics during processing, allowing for simple and
   centralized implementation strategies.

   Conceptually, a subtree filter is comprised of zero or more element
   subtrees, which represent the filter selection criteria.  At each
   containment level within a subtree, the set of sibling nodes is
   logically processed by the server to determine if its subtree and
   path of elements to the root are included in the filter output.

   All elements present in a particular subtree within a filter must
   match associated nodes present in the server's conceptual data model.
   XML namespaces may be specified (via 'xmlns' declarations) within the
   filter data model.  If they are, the declared namespace must first
   exactly match a namespace supported by the server.  Note that prefix
   values for qualified namespaces are not relevant when comparing
   filter elements to elements in the underlying data model.  Only data
   associated with a specified namespace will be included in the filter
   output.




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   Each node specified in a subtree filter represents an inclusive
   filter.  Only associated nodes in underlying data model(s) within the
   specified configuration datastore on the server are selected by the
   filter.  A node must exactly match the namespace and hierarchy of
   elements given in the filter data, except that the filter absolute
   path name is adjusted to start from the layer below <filter>.

   Response messages contain only the subtrees selected by the filter.
   Any selection criteria that were present in the request, within a
   particular selected subtree, are also included in the response.  Note
   that some elements expressed in the filter as leaf nodes will be
   expanded (i.e., subtrees included) in the filter output.  Specific
   data instances are not duplicated in the response in the event that
   the request contains multiple filter subtree expressions that select
   the same data.

6.2.  Subtree Filter Components

   A subtree filter is comprised of XML elements and their XML
   attributes.  There are five types of components that may be present
   in a subtree filter:

   o  Namespace Selection

   o  Attribute Match Expressions

   o  Containment Nodes

   o  Selection Nodes

   o  Content Match Nodes

6.2.1.  Namespace Selection

   If namespaces are used, then the filter output will only include
   elements from the specified namespace.  A namespace is considered to
   match (for filter purposes) if the content of the 'xmlns' attributes
   are the same in the filter and the underlying data model.  Note that
   namespace selection cannot be used by itself.  At least one element
   must be specified in the filter any elements to be included in the
   filter output.

   Example:

     <filter type="subtree">
       <top xmlns="http://example.com/schema/1.2/config"/>
     </filter>




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   In this example, the <top> element is a selection node, and only this
   node and any child nodes (from the underlying data model) in the
   'http://example.com/schema/1.2/config' namespace will be included in
   the filter output.

6.2.2.  Attribute Match Expressions

   An attribute that appears in a subtree filter is part of an
   "attribute match expression".  Any number of (unqualified or
   qualified) XML attributes may be present in any type of filter node.
   In addition to the selection criteria normally applicable to that
   node, the selected data must have matching values for every attribute
   specified in the node.  If an element is not defined to include a
   specified attribute, then it is not selected in the filter output.

   Example:

     <filter type="subtree">
       <t:top xmlns:t="http://example.com/schema/1.2/config">
         <t:interfaces>
           <t:interface t:ifName="eth0"/>
         </t:interfaces>
       </t:top>
     </filter>

   In this example, the <top>, <interfaces>, and <interface> elements
   are containment nodes, and 'ifName' is an attribute match expression.
   Only 'interface' nodes in the 'http://example.com/schema/1.2/config'
   namespace that have an 'ifName' attribute with the value 'eth0' and
   occur within 'interfaces' nodes within 'top' nodes will be included
   in the filter output.

6.2.3.  Containment Nodes

   Nodes that contain child elements within a subtree filter are called
   "containment nodes".  Each child element can be any type of node,
   including another containment node.  For each containment node
   specified in a subtree filter, all data model instances that exactly
   match the specified namespaces, element hierarchy, and any attribute
   match expressions are included in the filter output.

   Example:

     <filter type="subtree">
       <top xmlns="http://example.com/schema/1.2/config">
         <users/>
       </top>
     </filter>



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   In this example, the <top> element is a containment node.

6.2.4.  Selection Nodes

   An empty leaf node within a filter is called a "selection node", and
   it represents an "explicit selection" filter on the underlying data
   model.  Presence of any selection nodes within a set of sibling nodes
   will cause the filter to select the specified subtree(s) and suppress
   automatic selection of the entire set of sibling nodes in the
   underlying data model.  For filtering purposes, an empty leaf node
   can be declared either with an empty tag (e.g., <foo/>) or with
   explicit start and end tags (e.g., <foo> </foo>).  Any whitespace
   characters are ignored in this form.

   Example:

     <filter type="subtree">
       <top xmlns="http://example.com/schema/1.2/config">
         <users/>
       </top>
     </filter>

   In this example, the <top> element is a containment node, and the
   <users> element is a selection node.  Only 'users' nodes in the
   'http://example.com/schema/1.2/config' namespace that occur within a
   'top' element that is the root of the configuration datastore will be
   included in the filter output.

6.2.5.  Content Match Nodes

   A leaf node that contains simple content is called a "content match
   node".  It is used to select some or all of its sibling nodes for
   filter output, and it represents an exact-match filter on the leaf
   node element content.  The following constraints apply to content
   match nodes:

   o  A content match node must not contain nested elements (i.e., must
      resolve to a simpleType in the XML Schema Definition (XSD)).

   o  Multiple content match nodes (i.e., sibling nodes) are logically
      combined in an "AND" expression.

   o  Filtering of mixed content is not supported.

   o  Filtering of list content is not supported.

   o  Filtering of whitespace-only content is not supported.




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   o  A content match node must contain non-whitespace characters.  An
      empty element (e.g., <foo></foo>) will be interpreted as a
      selection node (e.g., <foo/>).

   o  Leading and trailing whitespace characters are ignored, but any
      whitespace characters within a block of text characters are not
      ignored or modified.

   If all specified sibling content match nodes in a subtree filter
   expression are 'true', then the filter output nodes are selected in
   the following manner:

   o  Each content match node in the sibling set is included in the
      filter output.

   o  If any containment nodes are present in the sibling set, then they
      are processed further and included if any nested filter criteria
      are also met.

   o  If any selection nodes are present in the sibling set, then all of
      them are included in the filter output.

   o  Otherwise (i.e., there are no selection or containment nodes in
      the filter sibling set), all the nodes defined at this level in
      the underlying data model (and their subtrees, if any) are
      returned in the filter output.

   If any of the sibling content match node tests are 'false', then no
   further filter processing is performed on that sibling set, and none
   of the sibling subtrees are selected by the filter, including the
   content match node(s).

   Example:

     <filter type="subtree">
       <top xmlns="http://example.com/schema/1.2/config">
         <users>
           <user>
             <name>fred</name>
           </user>
         </users>
       </top>
     </filter>

   In this example, the <users> and <user> nodes are both containment
   nodes, and <name> is a content match node.  Since no sibling nodes of
   <name> are specified (and therefore no containment or selection
   nodes), all of the sibling nodes of <name> are returned in the filter



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   output.  Only 'user' nodes in the
   'http://example.com/schema/1.2/config' namespace that match the
   element hierarchy and for which the <name> element is equal to 'fred'
   will be included in the filter output.

6.3.  Subtree Filter Processing

   The filter output (the set of selected nodes) is initially empty.

   Each subtree filter can contain one or more data model fragments,
   which represent portions of the data model that should be selected
   (with all child nodes) in the filter output.

   Each subtree data fragment is compared by the server to the internal
   data models supported by the server.  If the entire subtree data-
   fragment filter (starting from the root to the innermost element
   specified in the filter) exactly matches a corresponding portion of
   the supported data model, then that node and all its children are
   included in the result data.

   The server processes all nodes with the same parent node (sibling
   set) together, starting from the root to the leaf nodes.  The root
   elements in the filter are considered in the same sibling set
   (assuming they are in the same namespace), even though they do not
   have a common parent.

   For each sibling set, the server determines which nodes are included
   (or potentially included) in the filter output, and which sibling
   subtrees are excluded (pruned) from the filter output.  The server
   first determines which types of nodes are present in the sibling set
   and processes the nodes according to the rules for their type.  If
   any nodes in the sibling set are selected, then the process is
   recursively applied to the sibling sets of each selected node.  The
   algorithm continues until all sibling sets in all subtrees specified
   in the filter have been processed.

6.4.  Subtree Filtering Examples

6.4.1.  No Filter

   Leaving out the filter on the get operation returns the entire data
   model.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get/>
     </rpc>




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     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <!-- ... entire set of data returned ... -->
       </data>
     </rpc-reply>

6.4.2.  Empty Filter

   An empty filter will select nothing because no content match or
   selection nodes are present.  This is not an error.  The filter type
   attribute used in these examples is discussed further in Section 7.1.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get>
         <filter type="subtree">
         </filter>
       </get>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
       </data>
     </rpc-reply>

6.4.3.  Select the Entire <users> Subtree

   The filter in this example contains one selection node (<users>), so
   just that subtree is selected by the filter.  This example represents
   the fully-populated <users> data model in most of the filter examples
   that follow.  In a real data model, the <company-info> would not
   likely be returned with the list of users for a particular host or
   network.

   NOTE: The filtering and configuration examples used in this document
   appear in the namespace "http://example.com/schema/1.2/config".  The
   root element of this namespace is <top>.  The <top> element and its
   descendents represent an example configuration data model only.

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



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           <top xmlns="http://example.com/schema/1.2/config">
             <users/>
           </top>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>
             <user>
               <name>root</name>
               <type>superuser</type>
               <full-name>Charlie Root</full-name>
               <company-info>
                 <dept>1</dept>
                 <id>1</id>
               </company-info>
             </user>
             <user>
               <name>fred</name>
               <type>admin</type>
               <full-name>Fred Flintstone</full-name>
               <company-info>
                 <dept>2</dept>
                 <id>2</id>
               </company-info>
             </user>
             <user>
               <name>barney</name>
               <type>admin</type>
               <full-name>Barney Rubble</full-name>
               <company-info>
                 <dept>2</dept>
                 <id>3</id>
               </company-info>
             </user>
           </users>
         </top>
       </data>
     </rpc-reply>

   The following filter request would have produced the same result, but
   only because the container <users> defines one child element
   (<user>).




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     <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/schema/1.2/config">
             <users>
               <user/>
             </users>
           </top>
         </filter>
       </get-config>
     </rpc>

6.4.4.  Select All <name> Elements within the <users> Subtree

   This filter contains two containment nodes (<users>, <user>) and one
   selector node (<name>).  All instances of the <name> element in the
   same sibling set are selected in the filter output.  The manager may
   need to know that <name> is used as an instance identifier in this
   particular data structure, but the server does not need to know that
   meta-data in order to process the request.

     <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/schema/1.2/config">
             <users>
               <user>
                 <name/>
               </user>
             </users>
           </top>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>



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             <user>
               <name>root</name>
             </user>
             <user>
               <name>fred</name>
             </user>
             <user>
               <name>barney</name>
             </user>
           </users>
         </top>
       </data>
     </rpc-reply>

6.4.5.  One Specific <user> Entry

   This filter contains two containment nodes (<users>, <user>) and one
   content match node (<name>).  All instances of the sibling set
   containing <name> for which the value of <name> equals "fred" are
   selected in the filter output.

     <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/schema/1.2/config">
             <users>
               <user>
                 <name>fred</name>
               </user>
             </users>
           </top>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>
             <user>
               <name>fred</name>
               <type>admin</type>
               <full-name>Fred Flintstone</full-name>



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               <company-info>
                 <dept>2</dept>
                 <id>2</id>
               </company-info>
             </user>
           </users>
         </top>
       </data>
     </rpc-reply>

6.4.6.  Specific Elements from a Specific <user> Entry

   This filter contains two containment nodes (<users>, <user>), one
   content match node (<name>), and two selector nodes (<type>,
   <full-name>).  All instances of the <type> and <full-name> elements
   in the same sibling set containing <name> for which the value of
   <name> equals "fred" are selected in the filter output.  The
   <company-info> element is not included because the sibling set
   contains selection nodes.

     <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/schema/1.2/config">
             <users>
               <user>
                 <name>fred</name>
                 <type/>
                 <full-name/>
               </user>
             </users>
           </top>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>
             <user>
               <name>fred</name>
               <type>admin</type>



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               <full-name>Fred Flintstone</full-name>
             </user>
           </users>
         </top>
       </data>
     </rpc-reply>

6.4.7.  Multiple Subtrees

   This filter contains three subtrees (name=root, fred, barney).

   The "root" subtree filter contains two containment nodes (<users>,
   <user>), one content match node (<name>), and one selector node
   (<company-info>).  The subtree selection criteria is met, and just
   the company-info subtree for "root" is selected in the filter output.

   The "fred" subtree filter contains three containment nodes (<users>,
   <user>, <company-info>), one content match node (<name>), and one
   selector node (<id>).  The subtree selection criteria is met, and
   just the <id> element within the company-info subtree for "fred" is
   selected in the filter output.

   The "barney" subtree filter contains three containment nodes
   (<users>, <user>, <company-info>), two content match nodes (<name>,
   <type>), and one selector node (<dept>).  The subtree selection
   criteria is not met because user "barney" is not a "superuser", and
   the entire subtree for "barney" (including its parent <user> entry)
   is excluded from the filter output.

     <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/schema/1.2/config">
             <users>
               <user>
                 <name>root</name>
                 <company-info/>
               </user>
               <user>
                 <name>fred</name>
                 <company-info>
                   <id/>
                 </company-info>
               </user>



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               <user>
                 <name>barney</name>
                 <type>superuser</type>
                 <company-info>
                   <dept/>
                 </company-info>
               </user>
             </users>
           </top>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>
             <user>
               <name>root</name>
               <company-info>
                 <dept>1</dept>
                 <id>1</id>
               </company-info>
             </user>
             <user>
               <name>fred</name>
               <company-info>
                 <id>2</id>
               </company-info>
             </user>
           </users>
         </top>
       </data>
     </rpc-reply>

6.4.8.  Elements with Attribute Naming

   In this example, the filter contains one containment node
   (<interfaces>), one attribute match expression (ifName), and one
   selector node (<interface>).  All instances of the <interface>
   subtree that have an ifName attribute equal to "eth0" are selected in
   the filter output.  The filter data elements and attributes must be
   qualified because the ifName attribute will not be considered part of
   the 'schema/1.2' namespace if it is unqualified.






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     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get>
         <filter type="subtree">
           <t:top xmlns:t="http://example.com/schema/1.2/stats">
             <t:interfaces>
               <t:interface t:ifName="eth0"/>
             </t:interfaces>
           </t:top>
         </filter>
       </get>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <t:top xmlns:t="http://example.com/schema/1.2/stats">
           <t:interfaces>
             <t:interface t:ifName="eth0">
               <t:ifInOctets>45621</t:ifInOctets>
               <t:ifOutOctets>774344</t:ifOutOctets>
             </t:interface>
           </t:interfaces>
         </t:top>
       </data>
     </rpc-reply>

   If ifName were a child node instead of an attribute, then the
   following request would produce similar results.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get>
         <filter type="subtree">
           <top xmlns="http://example.com/schema/1.2/stats">
             <interfaces>
               <interface>
                 <ifName>eth0</ifName>
               </interface>
             </interfaces>
           </top>
         </filter>
       </get>
     </rpc>







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7.  Protocol Operations

   The NETCONF protocol provides a small set of low-level operations to
   manage device configurations and retrieve device state information.
   The base protocol provides operations to retrieve, configure, copy,
   and delete configuration datastores.  Additional operations are
   provided, based on the capabilities advertised by the device.

   The base protocol includes the following protocol operations:

   o  get

   o  get-config

   o  edit-config

   o  copy-config

   o  delete-config

   o  lock

   o  unlock

   o  close-session

   o  kill-session

   A protocol operation may fail for various reasons, including
   "operation not supported".  An initiator should not assume that any
   operation will always succeed.  The return values in any RPC reply
   should be checked for error responses.

   The syntax and XML encoding of the protocol operations are formally
   defined in the XML schema in Appendix B.  The following sections
   describe the semantics of each protocol operation.

7.1.  <get-config>

   Description:

      Retrieve all or part of a specified configuration.









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   Parameters:

      source:

         Name of the configuration datastore being queried, such as
         <running/>.

      filter:

         The filter element identifies the portions of the device
         configuration to retrieve.  If this element is unspecified, the
         entire configuration is returned.

         The filter element may optionally contain a "type" attribute.
         This attribute indicates the type of filtering syntax used
         within the filter element.  The default filtering mechanism in
         NETCONF is referred to as subtree filtering and is described in
         Section 6.  The value "subtree" explicitly identifies this type
         of filtering.

         If the NETCONF peer supports the :xpath capability
         (Section 8.9), the value "xpath" may be used to indicate that
         the select attribute on the filter element contains an XPath
         expression.

   Positive Response:

      If the device can satisfy the request, the server sends an
      <rpc-reply> element containing a <data> element with the results
      of the query.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

   Example: To retrieve the entire <users> subtree:

     <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/schema/1.2/config">
             <users/>
           </top>



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         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/config">
           <users>
             <user>
               <name>root</name>
               <type>superuser</type>
               <full-name>Charlie Root</full-name>
               <company-info>
                 <dept>1</dept>
                 <id>1</id>
               </company-info>
             </user>
             <!-- additional <user> elements appear here... -->
           </users>
         </top>
       </data>
     </rpc-reply>

   If the configuration is available in multiple formats, such as XML
   and text, an XML namespace can be used to specify which format is
   desired.  In the following example, the client uses a specific
   element (<config-text>) in a specific namespace to indicate to the
   server the desire to receive the configuration in an alternative
   format.  The server may support any number of distinct formats or
   views into the configuration data, with the client using the <filter>
   parameter to select between them.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get-config>
         <source>
           <running/>
         </source>
         <filter type="subtree">
           <!-- request a text version of the configuration -->
           <config-text xmlns="http://example.com/text/1.2/config"/>
         </filter>
       </get-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">



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       <data>
         <config-text xmlns="http://example.com/text/1.2/config">
           <!-- configuration text... -->
         </config-text>
       </data>
     </rpc-reply>

      Section 6 contains additional examples of subtree filtering.

7.2.  <edit-config>

   Description:

      The <edit-config> operation loads all or part of a specified
      configuration to the specified target configuration.  This
      operation allows the new configuration to be expressed in several
      ways, such as using a local file, a remote file, or inline.  If
      the target configuration does not exist, it will be created.  If a
      NETCONF peer supports the :url capability (Section 8.8), the <url>
      element can appear instead of the <config> parameter and should
      identify a local configuration file.

      The device analyzes the source and target configurations and
      performs the requested changes.  The target configuration is not
      necessarily replaced, as with the <copy-config> message.  Instead,
      the target configuration is changed in accordance with the
      source's data and requested operations.

   Attributes:

      operation:

         Elements in the <config> subtree may contain an "operation"
         attribute.  The attribute identifies the point in the
         configuration to perform the operation and MAY appear on
         multiple elements throughout the <config> subtree.

         If the operation attribute is not specified, the configuration
         is merged into the configuration datastore.

         The operation attribute has one of the following values:

         merge: The configuration data identified by the element
            containing this attribute is merged with the configuration
            at the corresponding level in the configuration datastore
            identified by the target parameter.  This is the default
            behavior.




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         replace: The configuration data identified by the element
            containing this attribute replaces any related configuration
            in the configuration datastore identified by the target
            parameter.  Unlike a <copy-config> operation, which replaces
            the entire target configuration, only the configuration
            actually present in the config parameter is affected.

         create: The configuration data identified by the element
            containing this attribute is added to the configuration if
            and only if the configuration data does not already exist on
            the device.  If the configuration data exists, an
            <rpc-error> element is returned with an <error-tag> value of
            data-exists.

         delete: The configuration data identified by the element
            containing this attribute is deleted in the configuration
            datastore identified by the target parameter.

   Parameters:

      target:

         Name of the configuration datastore being edited, such as
         <running/> or <candidate/>.

      default-operation:

         Selects the default operation (as described in the "operation"
         attribute) for this <edit-config> request.  The default value
         for the default-operation parameter is "merge".

         The default-operation parameter is optional, but if provided,
         it must have one of the following values:

         merge: The configuration data in the <config> parameter is
            merged with the configuration at the corresponding level in
            the target datastore.  This is the default behavior.

         replace: The configuration data in the <config> parameter
            completely replaces the configuration in the target
            datastore.  This is useful for loading previously saved
            configuration data.

         none: The target datastore is unaffected by the configuration
            in the <config> parameter, unless and until the incoming
            configuration data uses the "operation" attribute to request
            a different operation.  If the configuration in the <config>
            parameter contains data for which there is not a



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            corresponding level in the target datastore, an <rpc-error>
            is returned with an <error-tag> value of data-missing.
            Using "none" allows operations like "delete" to avoid
            unintentionally creating the parent hierarchy of the element
            to be deleted.

      test-option:

         The test-option element may be specified only if the device
         advertises the :validate capability (Section 8.6).

         The test-option element has one of the following values:

         test-then-set: Perform a validation test before attempting to
            set.  If validation errors occur, do not perform the
            <edit-config> operation.  This is the default test-option.

         set: Perform a set without a validation test first.

      error-option:

         The error-option element has one of the following values:

         stop-on-error: Abort the edit-config operation on first error.
            This is the default error-option.

         continue-on-error: Continue to process configuration data on
            error; error is recorded, and negative response is generated
            if any errors occur.

         rollback-on-error: If an error condition occurs such that an
            error severity <rpc-error> element is generated, the server
            will stop processing the edit-config operation and restore
            the specified configuration to its complete state at the
            start of this edit-config operation.  This option requires
            the server to support the :rollback-on-error capability
            described in Section 8.5.

      config:

         A hierarchy of configuration data as defined by one of the
         device's data models.  The contents MUST be placed in an
         appropriate namespace, to allow the device to detect the
         appropriate data model, and the contents MUST follow the
         constraints of that data model, as defined by its capability
         definition.  Capabilities are discussed in Section 8.





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   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent containing an <ok> element.

   Negative Response:

      An <rpc-error> response is sent if the request cannot be completed
      for any reason.

   Example:

      The <edit-config> examples in this section utilize a simple data
      model, in which multiple instances of the 'interface' element may
      be present, and an instance is distinguished by the 'name' element
      within each 'interface' element.

      Set the MTU to 1500 on an interface named "Ethernet0/0" in the
      running configuration:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <config>
           <top xmlns="http://example.com/schema/1.2/config">
             <interface>
               <name>Ethernet0/0</name>
               <mtu>1500</mtu>
             </interface>
           </top>
         </config>
       </edit-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

      Add an interface named "Ethernet0/0" to the running configuration,
      replacing any previous interface with that name:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>



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         <target>
           <running/>
         </target>
         <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
           <top xmlns="http://example.com/schema/1.2/config">
             <interface xc:operation="replace">
               <name>Ethernet0/0</name>
               <mtu>1500</mtu>
               <address>
                 <name>192.0.2.4</name>
                 <prefix-length>24</prefix-length>
               </address>
             </interface>
           </top>
         </config>
       </edit-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

      Delete the configuration for an interface named "Ethernet0/0" from
      the running configuration:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <default-operation>none</default-operation>
         <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
           <top xmlns="http://example.com/schema/1.2/config">
             <interface xc:operation="delete">
               <name>Ethernet0/0</name>
             </interface>
           </top>
         </config>
       </edit-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>




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      Delete interface 192.0.2.4 from an OSPF area (other interfaces
      configured in the same area are unaffected):

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <default-operation>none</default-operation>
         <config xmlns:xc="urn:ietf:params:xml:ns:netconf:base:1.0">
           <top xmlns="http://example.com/schema/1.2/config">
             <protocols>
               <ospf>
                 <area>
                   <name>0.0.0.0</name>
                   <interfaces>
                     <interface xc:operation="delete">
                       <name>192.0.2.4</name>
                     </interface>
                   </interfaces>
                 </area>
               </ospf>
             </protocols>
           </top>
         </config>
       </edit-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

7.3.  <copy-config>

   Description:

      Create or replace an entire configuration datastore with the
      contents of another complete configuration datastore.  If the
      target datastore exists, it is overwritten.  Otherwise, a new one
      is created, if allowed.

      If a NETCONF peer supports the :url capability (Section 8.8), the
      <url> element can appear as the <source> or <target> parameter.

      Even if it advertises the :writable-running capability, a device
      may choose not to support the <running/> configuration datastore



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      as the <target> parameter of a <copy-config> operation.  A device
      may choose not to support remote-to-remote copy operations, where
      both the <source> and <target> parameters use the <url> element.

      If the source and target parameters identify the same URL or
      configuration datastore, an error MUST be returned with an error-
      tag containing invalid-value.

   Parameters:

      target:

         Name of the configuration datastore to use as the destination
         of the copy operation.

      source:

         Name of the configuration datastore to use as the source of the
         copy operation or the <config> element containing the
         configuration subtree to copy.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that includes an <ok> element.

   Negative Response:

      An <rpc-error> element is included within the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <copy-config>
         <target>
           <running/>
         </target>
         <source>
           <url>https://user@example.com:passphrase/cfg/new.txt</url>
         </source>
       </copy-config>
     </rpc>







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     <rpc-reply message-id="101"
         xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

7.4.  <delete-config>

   Description:

      Delete a configuration datastore.  The <running> configuration
      datastore cannot be deleted.

      If a NETCONF peer supports the :url capability (Section 8.8), the
      <url> element can appear as the <target> parameter.

   Parameters:

      target:

         Name of the configuration datastore to delete.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that includes an <ok> element.

   Negative Response:

      An <rpc-error> element is included within the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <delete-config>
         <target>
           <startup/>
         </target>
       </delete-config>
     </rpc>

      <rpc-reply message-id="101"
           xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>





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7.5.  <lock>

   Description:

      The lock operation allows the client to lock the configuration
      system of a device.  Such locks are intended to be short-lived and
      allow a client to make a change without fear of interaction with
      other NETCONF clients, non-NETCONF clients (e.g., SNMP and command
      line interface (CLI) scripts), and human users.

      An attempt to lock the configuration MUST fail if an existing
      session or other entity holds a lock on any portion of the lock
      target.

      When the lock is acquired, the server MUST prevent any changes to
      the locked resource other than those requested by this session.
      SNMP and CLI requests to modify the resource MUST fail with an
      appropriate error.

      The duration of the lock is defined as beginning when the lock is
      acquired and lasting until either the lock is released or the
      NETCONF session closes.  The session closure may be explicitly
      performed by the client, or implicitly performed by the server
      based on criteria such as failure of the underlying transport, or
      simple inactivity timeout.  This criteria is dependent on the
      implementation and the underlying transport.

      The lock operation takes a mandatory parameter, target.  The
      target parameter names the configuration that will be locked.
      When a lock is active, using the <edit-config> operation on the
      locked configuration and using the locked configuration as a
      target of the <copy-config> operation will be disallowed by any
      other NETCONF session.  Additionally, the system will ensure that
      these locked configuration resources will not be modified by other
      non-NETCONF management operations such as SNMP and CLI.  The
      <kill-session> message (at the RPC layer) can be used to force the
      release of a lock owned by another NETCONF session.  It is beyond
      the scope of this document to define how to break locks held by
      other entities.

      A lock MUST not be granted if either of the following conditions
      is true:

      *  A lock is already held by any NETCONF session or another
         entity.






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      *  The target configuration is <candidate>, it has already been
         modified, and these changes have not been committed or rolled
         back.

      The server MUST respond with either an <ok> element or an
      <rpc-error>.

      A lock will be released by the system if the session holding the
      lock is terminated for any reason.

   Parameters:

      target:

         Name of the configuration datastore to lock.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that contains an <ok> element.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

      If the lock is already held, the <error-tag> element will be
      'lock-denied' and the <error-info> element will include the
      <session-id> of the lock owner.  If the lock is held by a non-
      NETCONF entity, a <session-id> of 0 (zero) is included.  Note that
      any other entity performing a lock on even a partial piece of a
      target will prevent a NETCONF lock (which is global) from being
      obtained on that target.

   Example:

      The following example shows a successful acquisition of a lock.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <lock>
         <target>
           <running/>
         </target>
       </lock>
     </rpc>





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     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/> <!-- lock succeeded -->
     </rpc-reply>

   Example:

      The following example shows a failed attempt to acquire a lock
      when the lock is already in use.


     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <lock>
         <target>
           <running/>
         </target>
       </lock>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <rpc-error> <!-- lock failed -->
         <error-type>protocol</error-type>
         <error-tag>lock-denied</error-tag>
         <error-severity>error</error-severity>
         <error-message>
           Lock failed, lock is already held
         </error-message>
         <error-info>
           <session-id>454</session-id>
           <!-- lock is held by NETCONF session 454 -->
         </error-info>
       </rpc-error>
     </rpc-reply>

7.6.  <unlock>

   Description:

      The unlock operation is used to release a configuration lock,
      previously obtained with the <lock> operation.

      An unlock operation will not succeed if any of the following
      conditions are true:

      *  the specified lock is not currently active




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      *  the session issuing the <unlock> operation is not the same
         session that obtained the lock

      The server MUST respond with either an <ok> element or an
      <rpc-error>.

   Parameters:

      target:

         Name of the configuration datastore to unlock.

         A NETCONF client is not permitted to unlock a configuration
         datastore that it did not lock.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that contains an <ok> element.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <unlock>
         <target>
          <running/>
         </target>
       </unlock>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

7.7.  <get>

   Description:

      Retrieve running configuration and device state information.





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   Parameters:

      filter:

         This parameter specifies the portion of the system
         configuration and state data to retrieve.  If this parameter is
         empty, all the device configuration and state information is
         returned.

         The filter element may optionally contain a 'type' attribute.
         This attribute indicates the type of filtering syntax used
         within the filter element.  The default filtering mechanism in
         NETCONF is referred to as subtree filtering and is described in
         Section 6.  The value 'subtree' explicitly identifies this type
         of filtering.

         If the NETCONF peer supports the :xpath capability
         (Section 8.9), the value "xpath" may be used to indicate that
         the select attribute of the filter element contains an XPath
         expression.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent.  The <data> section contains the appropriate subset.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get>
         <filter type="subtree">
           <top xmlns="http://example.com/schema/1.2/stats">
             <interfaces>
               <interface>
                 <ifName>eth0</ifName>
               </interface>
             </interfaces>
           </top>
         </filter>
       </get>
     </rpc>




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     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <data>
         <top xmlns="http://example.com/schema/1.2/stats">
           <interfaces>
             <interface>
               <ifName>eth0</ifName>
               <ifInOctets>45621</ifInOctets>
               <ifOutOctets>774344</ifOutOctets>
             </interface>
           </interfaces>
         </top>
       </data>
     </rpc-reply>

7.8.  <close-session>

   Description:

      Request graceful termination of a NETCONF session.

      When a NETCONF server receives a <close-session> request, it will
      gracefully close the session.  The server will release any locks
      and resources associated with the session and gracefully close any
      associated connections.  Any NETCONF requests received after a
      <close-session> request will be ignored.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that includes an <ok> element.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <close-session/>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>



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7.9.  <kill-session>

   Description:

      Force the termination of a NETCONF session.

      When a NETCONF entity receives a <kill-session> request for an
      open session, it will abort any operations currently in process,
      release any locks and resources associated with the session, and
      close any associated connections.

      If a NETCONF server receives a <kill-session> request while
      processing a confirmed commit (Section 8.4), it must restore the
      configuration to its state before the confirmed commit was issued.

      Otherwise, the <kill-session> operation does not roll back
      configuration or other device state modifications made by the
      entity holding the lock.

   Parameters:

      session-id:

         Session identifier of the NETCONF session to be terminated.  If
         this value is equal to the current session ID, an
         'invalid-value' error is returned.

   Positive Response:

      If the device was able to satisfy the request, an <rpc-reply> is
      sent that includes an <ok> element.

   Negative Response:

      An <rpc-error> element is included in the <rpc-reply> if the
      request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <kill-session>
         <session-id>4</session-id>
       </kill-session>
     </rpc>






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     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

8.  Capabilities

   This section defines a set of capabilities that a client or a server
   MAY implement.  Each peer advertises its capabilities by sending them
   during an initial capabilities exchange.  Each peer needs to
   understand only those capabilities that it might use and MUST ignore
   any capability received from the other peer that it does not require
   or does not understand.

   Additional capabilities can be defined using the template in
   Appendix C.  Future capability definitions may be published as
   standards by standards bodies or published as proprietary extensions.

   A NETCONF capability is identified with a URI.  The base capabilities
   are defined using URNs following the method described in RFC 3553
   [6].  Capabilities defined in this document have the following
   format:

      urn:ietf:params:netconf:capability:{name}:1.0

   where {name} is the name of the capability.  Capabilities are often
   referenced in discussions and email using the shorthand :{name}.  For
   example, the foo capability would have the formal name
   "urn:ietf:params:netconf:capability:foo:1.0" and be called ":foo".
   The shorthand form MUST NOT be used inside the protocol.

8.1.  Capabilities Exchange

   Capabilities are advertised in messages sent by each peer during
   session establishment.  When the NETCONF session is opened, each peer
   (both client and server) MUST send a <hello> element containing a
   list of that peer's capabilities.  Each peer MUST send at least the
   base NETCONF capability, "urn:ietf:params:netconf:base:1.0".

   A server sending the <hello> element MUST include a <session-id>
   element containing the session ID for this NETCONF session.  A client
   sending the <hello> element MUST NOT include a <session-id> element.

   A server receiving a <session-id> element MUST NOT continue the
   NETCONF session.  Similarly, a client that does not receive a
   <session-id> element in the server's <hello> message MUST NOT
   continue the NETCONF session.  In both cases, the underlying
   transport should be closed.



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   In the following example, a server advertises the base NETCONF
   capability, one NETCONF capability defined in the base NETCONF
   document, and one implementation-specific capability.

   <hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <capabilities>
       <capability>
         urn:ietf:params:netconf:base:1.0
       </capability>
       <capability>
         urn:ietf:params:netconf:capability:startup:1.0
       </capability>
       <capability>
         http://example.net/router/2.3/myfeature
       </capability>
     </capabilities>
     <session-id>4</session-id>
   </hello>

   Each peer sends its <hello> element simultaneously as soon as the
   connection is open.  A peer MUST NOT wait to receive the capability
   set from the other side before sending its own set.

8.2.  Writable-Running Capability

8.2.1.  Description

   The :writable-running capability indicates that the device supports
   direct writes to the <running> configuration datastore.  In other
   words, the device supports edit-config and copy-config operations
   where the <running> configuration is the target.

8.2.2.  Dependencies

   None.

8.2.3.  Capability Identifier

   The :writable-running capability is identified by the following
   capability string:

      urn:ietf:params:netconf:capability:writable-running:1.0









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8.2.4.  New Operations

   None.

8.2.5.  Modifications to Existing Operations

8.2.5.1.  <edit-config>

   The :writable-running capability modifies the <edit-config> operation
   to accept the <running> element as a <target>.

8.2.5.2.  <copy-config>

   The :writable-running capability modifies the <copy-config> operation
   to accept the <running> element as a <target>.

8.3.  Candidate Configuration Capability

8.3.1.  Description

   The candidate configuration capability, :candidate, indicates that
   the device supports a candidate configuration datastore, which is
   used to hold configuration data that can be manipulated without
   impacting the device's current configuration.  The candidate
   configuration is a full configuration data set that serves as a work
   place for creating and manipulating configuration data.  Additions,
   deletions, and changes may be made to this data to construct the
   desired configuration data.  A <commit> operation may be performed at
   any time that causes the device's running configuration to be set to
   the value of the candidate configuration.

   The <commit> operation effectively sets the running configuration to
   the current contents of the candidate configuration.  While it could
   be modeled as a simple copy, it is done as a distinct operation for a
   number of reasons.  In keeping high-level concepts as first class
   operations, we allow developers to see more clearly both what the
   client is requesting and what the server must perform.  This keeps
   the intentions more obvious, the special cases less complex, and the
   interactions between operations more straightforward.  For example,
   the :confirmed-commit capability (Section 8.4) would make no sense as
   a "copy confirmed" operation.

   The candidate configuration may be shared among multiple sessions.
   Unless a client has specific information that the candidate
   configuration is not shared, it must assume that other sessions may
   be able to modify the candidate configuration at the same time.  It
   is therefore prudent for a client to lock the candidate configuration
   before modifying it.



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   The client can discard any uncommitted changes to the candidate
   configuration by executing the <discard-changes> operation.  This
   operation reverts the contents of the candidate configuration to the
   contents of the running configuration.

8.3.2.  Dependencies

   None.

8.3.3.  Capability Identifier

   The :candidate capability is identified by the following capability
   string:

      urn:ietf:params:netconf:capability:candidate:1.0

8.3.4.  New Operations

8.3.4.1.  <commit>

   Description:

         When a candidate configuration's content is complete, the
         configuration data can be committed, publishing the data set to
         the rest of the device and requesting the device to conform to
         the behavior described in the new configuration.

         To commit the candidate configuration as the device's new
         current configuration, use the <commit> operation.

         The <commit> operation instructs the device to implement the
         configuration data contained in the candidate configuration.
         If the device is unable to commit all of the changes in the
         candidate configuration datastore, then the running
         configuration MUST remain unchanged.  If the device does
         succeed in committing, the running configuration MUST be
         updated with the contents of the candidate configuration.

         If the system does not have the :candidate capability, the
         <commit> operation is not available.

   Positive Response:

         If the device was able to satisfy the request, an <rpc-reply>
         is sent that contains an <ok> element.






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   Negative Response:

         An <rpc-error> element is included in the <rpc-reply> if the
         request cannot be completed for any reason.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <commit/>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

8.3.4.2.  <discard-changes>

   If the client decides that the candidate configuration should not be
   committed, the <discard-changes> operation can be used to revert the
   candidate configuration to the current running configuration.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <discard-changes/>
     </rpc>

   This operation discards any uncommitted changes by resetting the
   candidate configuration with the content of the running
   configuration.

8.3.5.  Modifications to Existing Operations

8.3.5.1.  <get-config>, <edit-config>, <copy-config>, and <validate>

   The candidate configuration can be used as a source or target of any
   <get-config>, <edit-config>, <copy-config>, or <validate> operation
   as a <source> or <target> parameter.  The <candidate> element is used
   to indicate the candidate configuration:











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     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get-config> <!-- any NETCONF operation -->
         <source>
           <candidate/>
         </source>
       </get-config>
     </rpc>

8.3.5.2.  <lock> and <unlock>

   The candidate configuration can be locked using the <lock> operation
   with the <candidate> element as the <target> parameter:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <lock>
         <target>
           <candidate/>
         </target>
       </lock>
     </rpc>

   Similarly, the candidate configuration is unlocked using the
   <candidate> element as the <target> parameter:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <unlock>
         <target>
           <candidate/>
         </target>
       </unlock>
     </rpc>

   When a client fails with outstanding changes to the candidate
   configuration, recovery can be difficult.  To facilitate easy
   recovery, any outstanding changes are discarded when the lock is
   released, whether explicitly with the <unlock> operation or
   implicitly from session failure.











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8.4.  Confirmed Commit Capability

8.4.1.  Description

   The :confirmed-commit capability indicates that the server will
   support the <confirmed> and <confirm-timeout> parameters for the
   <commit> protocol operation.  See Section 8.3 for further details on
   the <commit> operation.

   A confirmed commit operation MUST be reverted if a follow-up commit
   (called the "confirming commit") is not issued within 600 seconds (10
   minutes).  The timeout period can be adjusted with the
   <confirm-timeout> element.  The confirming commit can itself include
   a <confirmed> parameter.

   If the session issuing the confirmed commit is terminated for any
   reason before the confirm timeout expires, the server MUST restore
   the configuration to its state before the confirmed commit was
   issued.

   If the device reboots for any reason before the confirm timeout
   expires, the server MUST restore the configuration to its state
   before the confirmed commit was issued.

   If a confirming commit is not issued, the device will revert its
   configuration to the state prior to the issuance of the confirmed
   commit.  Note that any commit operation, including a commit which
   introduces additional changes to the configuration, will serve as a
   confirming commit.  Thus to cancel a confirmed commit and revert
   changes without waiting for the confirm timeout to expire, the
   manager can explicitly restore the configuration to its state before
   the confirmed commit was issued.

   For shared configurations, this feature can cause other configuration
   changes (for example, via other NETCONF sessions) to be inadvertently
   altered or removed, unless the configuration locking feature is used
   (in other words, the lock is obtained before the edit-config
   operation is started).  Therefore, it is strongly suggested that in
   order to use this feature with shared configuration databases,
   configuration locking should also be used.

8.4.2.  Dependencies

   The :confirmed-commit capability is only relevant if the :candidate
   capability is also supported.






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8.4.3.  Capability Identifier

   The :confirmed-commit capability is identified by the following
   capability string:

      urn:ietf:params:netconf:capability:confirmed-commit:1.0

8.4.4.  New Operations

   None.

8.4.5.  Modifications to Existing Operations

8.4.5.1.  <commit>

   The :confirmed-commit capability allows 2 additional parameters to
   the <commit> operation.

   Parameters:

      confirmed:

            Perform a confirmed commit operation.

      confirm-timeout:

            Timeout period for confirmed commit, in seconds.  If
            unspecified, the confirm timeout defaults to 600 seconds.

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <commit>
         <confirmed/>
         <confirm-timeout>120</confirm-timeout>
       </commit>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>








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8.5.  Rollback on Error Capability

8.5.1.  Description

   This capability indicates that the server will support the
   'rollback-on-error' value in the <error-option> parameter to the
   <edit-config> operation.

   For shared configurations, this feature can cause other configuration
   changes (for example, via other NETCONF sessions) to be inadvertently
   altered or removed, unless the configuration locking feature is used
   (in other words, the lock is obtained before the edit-config
   operation is started).  Therefore, it is strongly suggested that in
   order to use this feature with shared configuration databases,
   configuration locking also be used.

8.5.2.  Dependencies

   None

8.5.3.  Capability Identifier

   The :rollback-on-error capability is identified by the following
   capability string:

      urn:ietf:params:netconf:capability:rollback-on-error:1.0

8.5.4.  New Operations

   None.

8.5.5.  Modifications to Existing Operations

8.5.5.1.  <edit-config>

   The :rollback-on-error capability allows the 'rollback-on-error'
   value to the <error-option> parameter on the <edit-config> operation.


     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <error-option>rollback-on-error</error-option>
         <config>
           <top xmlns="http://example.com/schema/1.2/config">



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             <interface>
               <name>Ethernet0/0</name>
               <mtu>100000</mtu>
             </interface>
           </top>
         </config>
       </edit-config>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>

8.6.  Validate Capability

8.6.1.  Description

   Validation consists of checking a candidate configuration for
   syntactical and semantic errors before applying the configuration to
   the device.

   If this capability is advertised, the device supports the <validate>
   protocol operation and checks at least for syntax errors.  In
   addition, this capability supports the test-option parameter to the
   <edit-config> operation and, when it is provided, checks at least for
   syntax errors.

8.6.2.  Dependencies

   None.

8.6.3.  Capability Identifier

   The :validate capability is identified by the following capability
   string:

      urn:ietf:params:netconf:capability:validate:1.0

8.6.4.  New Operations

8.6.4.1.  <validate>

   Description:

         This protocol operation validates the contents of the specified
         configuration.




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   Parameters:

      source:

            Name of the configuration datastore being validated, such as
            <candidate> or the <config> element containing the
            configuration subtree to validate.

   Positive Response:

         If the device was able to satisfy the request, an <rpc-reply>
         is sent that contains an <ok> element.

   Negative Response:

         An <rpc-error> element is included in the <rpc-reply> if the
         request cannot be completed for any reason.

         A validate operation can fail for any of the following reasons:

         +  Syntax errors

         +  Missing parameters

         +  References to undefined configuration data

   Example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <validate>
         <source>
           <candidate/>
         </source>
       </validate>
     </rpc>

     <rpc-reply message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <ok/>
     </rpc-reply>










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8.7.  Distinct Startup Capability

8.7.1.  Description

   The device supports separate running and startup configuration
   datastores.  Operations that affect the running configuration will
   not be automatically copied to the startup configuration.  An
   explicit <copy-config> operation from the <running> to the <startup>
   must be invoked to update the startup configuration to the current
   contents of the running configuration.  NETCONF protocol operations
   refer to the startup datastore using the <startup> element.

8.7.2.  Dependencies

   None.

8.7.3.  Capability Identifier

   The :startup capability is identified by the following capability
   string:

      urn:ietf:params:netconf:capability:startup:1.0

8.7.4.  New Operations

   None.

8.7.5.  Modifications to Existing Operations

8.7.5.1.  General

   The :startup capability adds the <startup/> configuration datastore
   to arguments of several NETCONF operations.  The server MUST support
   the following additional values:

















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   +--------------------+--------------------------+-------------------+
   | Operation          | Parameters               | Notes             |
   +--------------------+--------------------------+-------------------+
   | <get-config>       | <source>                 |                   |
   |                    |                          |                   |
   | <copy-config>      | <source> <target>        |                   |
   |                    |                          |                   |
   | <lock>             | <target>                 |                   |
   |                    |                          |                   |
   | <unlock>           | <target>                 |                   |
   |                    |                          |                   |
   | <validate>         | <source>                 | If :validate is   |
   |                    |                          | advertised        |
   +--------------------+--------------------------+-------------------+

   To save the startup configuration, use the copy-config operation to
   copy the <running> configuration datastore to the <startup>
   configuration datastore.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <copy-config>
         <source>
           <running/>
         </source>
         <target>
           <startup/>
         </target>
       </copy-config>
     </rpc>

8.8.  URL Capability

8.8.1.  Description

   The NETCONF peer has the ability to accept the <url> element in
   <source> and <target> parameters.  The capability is further
   identified by URL arguments indicating the URL schemes supported.

8.8.2.  Dependencies

   None.









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8.8.3.  Capability Identifier

   The :url capability is identified by the following capability string:

   urn:ietf:params:netconf:capability:url:1.0?scheme={name,...}

   The :url capability URI MUST contain a "scheme" argument assigned a
   comma-separated list of scheme names indicating which schemes the
   NETCONF peer supports.  For example:

      urn:ietf:params:netconf:capability:url:1.0?scheme=http,ftp,file

8.8.4.  New Operations

   None.

8.8.5.  Modifications to Existing Operations

8.8.5.1.  <edit-config>

   The :url capability modifies the <edit-config> operation to accept
   the <url> element as an alternative to the <config> parameter.  If
   the <url> element is specified, then it should identify a local
   configuration file.

8.8.5.2.  <copy-config>

   The :url capability modifies the <copy-config> operation to accept
   the <url> element as the value of the <source> and the <target>
   parameters.

8.8.5.3.  <delete-config>

   The :url capability modifies the <delete-config> operation to accept
   the <url> element as the value of the <target> parameters.  If this
   parameter contains a URL, then it should identify a local
   configuration file.

8.8.5.4.  <validate>

   The :url capability modifies the <validate> operation to accept the
   <url> element as the value of the <source> parameter.









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8.9.  XPath Capability

8.9.1.  Description

   The XPath capability indicates that the NETCONF peer supports the use
   of XPath expressions in the <filter> element.  XPath is described in
   [2].

   The XPath expression must return a node-set.

   The XPath expression is evaluated in a context where the context node
   is the root node, and the set of namespace declarations are those in
   scope on the filter element, including the default namespace.

8.9.2.  Dependencies

   None.

8.9.3.  Capability Identifier

   The :xpath capability is identified by the following capability
   string:

      urn:ietf:params:netconf:capability:xpath:1.0

8.9.4.  New Operations

   None.

8.9.5.  Modifications to Existing Operations

8.9.5.1.  <get-config> and <get>

   The :xpath capability modifies the <get> and <get-config> operations
   to accept the value "xpath" in the type attribute of the filter
   element.  When the type attribute is set to "xpath", a select
   attribute MUST be present on the filter element.  The select
   attribute will be treated as an XPath expression and used to filter
   the returned data.  The filter element itself MUST be empty in this
   case.

   For example:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <get-config>
         <source>
           <running/>



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         </source>
         <!-- get the user named fred -->
         <filter type="xpath" select="top/users/user[name='fred']"/>
        </get-config>
     </rpc>

9.  Security Considerations

   This document does not specify an authorization scheme, as such a
   scheme should be tied to a meta-data model or a data model.
   Implementors SHOULD provide a comprehensive authorization scheme with
   NETCONF.

   Authorization of individual users via the NETCONF server may or may
   not map 1:1 to other interfaces.  First, the data models may be
   incompatible.  Second, it may be desirable to authorize based on
   mechanisms available in the transport protocol layer (TELNET, SSH,
   etc).

   In addition, operations on configurations may have unintended
   consequences if those operations are also not guarded by the global
   lock on the files or objects being operated upon.  For instance, a
   partially complete access list could be committed from a candidate
   configuration unbeknownst to the owner of the lock of the candidate
   configuration, leading to either an insecure or inaccessible device
   if the lock on the candidate configuration does not also apply to the
   <copy-config> operation when applied to it.

   Configuration information is by its very nature sensitive.  Its
   transmission in the clear and without integrity checking leaves
   devices open to classic eavesdropping attacks.  Configuration
   information often contains passwords, user names, service
   descriptions, and topological information, all of which are
   sensitive.  Because of this, this protocol should be implemented
   carefully with adequate attention to all manner of attack one might
   expect to experience with other management interfaces.

   The protocol, therefore, must minimally support options for both
   confidentiality and authentication.  It is anticipated that the
   underlying protocol (SSH, BEEP, etc) will provide for both
   confidentiality and authentication, as is required.  It is further
   expected that the identity of each end of a NETCONF session will be
   available to the other in order to determine authorization for any
   given request.  One could also easily envision additional
   information, such as transport and encryption methods, being made
   available for purposes of authorization.  NETCONF itself provide no
   means to re-authenticate, much less authenticate.  All such actions
   occur at lower layers.



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   Different environments may well allow different rights prior to and
   then after authentication.  Thus, an authorization model is not
   specified in this document.  When an operation is not properly
   authorized, a simple "access denied" is sufficient.  Note that
   authorization information may be exchanged in the form of
   configuration information, which is all the more reason to ensure the
   security of the connection.

   That having been said, it is important to recognize that some
   operations are clearly more sensitive by nature than others.  For
   instance, <copy-config> to the startup or running configurations is
   clearly not a normal provisioning operation, whereas <edit-config>
   is.  Such global operations MUST disallow the changing of information
   that an individual does not have authorization to perform.  For
   example, if a user A is not allowed to configure an IP address on an
   interface but user B has configured an IP address on an interface in
   the <candidate> configuration, user A must not be allowed to commit
   the <candidate> configuration.

   Similarly, just because someone says "go write a configuration
   through the URL capability at a particular place", this does not mean
   that an element should do it without proper authorization.

   The <lock> operation will demonstrate that NETCONF is intended for
   use by systems that have at least some trust of the administrator.
   As specified in this document, it is possible to lock portions of a
   configuration that a principal might not otherwise have access to.
   After all, the entire configuration is locked.  To mitigate this
   problem, there are two approaches.  It is possible to kill another
   NETCONF session programmatically from within NETCONF if one knows the
   session identifier of the offending session.  The other possible way
   to break a lock is to provide an function within the device's native
   user interface.  These two mechanisms suffer from a race condition
   that may be ameliorated by removing the offending user from an AAA
   server.  However, such a solution is not useful in all deployment
   scenarios, such as those where SSH public/private key pairs are used.















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10.  IANA Considerations

10.1.  NETCONF XML Namespace

   This document registers a URI for the NETCONF XML namespace in the
   IETF XML registry [7].

   Following the format in RFC 3688, IANA has made the following
   registration.

   URI: urn:ietf:params:xml:ns:netconf:base:1.0

   Registrant Contact: The IESG.

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

10.2.  NETCONF XML Schema

   This document registers a URI for the NETCONF XML schema in the IETF
   XML registry [7].

   Following the format in RFC 3688, IANA has made the following
   registration.

   URI: urn:ietf:params:xml:schema:netconf

   Registrant Contact: The IESG.

   XML: Appendix B of this document.

10.3.  NETCONF Capability URNs

   This document creates a registry that allocates NETCONF capability
   identifiers.  Additions to the registry require IETF Standards
   Action.

   The initial content of the registry contains the capability URNs
   defined in Section 8.

   Following the guidelines in RFC 3553 [6], IANA assigned a NETCONF
   sub-namespace as follows:

   Registry name: netconf

   Specification: Section 8 of this document.

   Repository: The following table.




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   +--------------------+----------------------------------------------+
   | Index              | Capability Identifier                        |
   +--------------------+----------------------------------------------+
   | :writable-running  | urn:ietf:params:netconf:capability:writable- |
   |                    | running:1.0                                  |
   |                    |                                              |
   | :candidate         | urn:ietf:params:netconf:capability:candidate |
   |                    | :1.0                                         |
   |                    |                                              |
   | :confirmed-commit  | urn:ietf:params:netconf:capability:confirmed |
   |                    | -commit:1.0                                  |
   |                    |                                              |
   | :rollback-on-error | urn:ietf:params:netconf:capability:rollback- |
   |                    | on-error:1.0                                 |
   |                    |                                              |
   | :validate          | urn:ietf:params:netconf:capability:validate: |
   |                    | 1.0                                          |
   |                    |                                              |
   | :startup           | urn:ietf:params:netconf:capability:startup:1 |
   |                    | .0                                           |
   |                    |                                              |
   | :url               | urn:ietf:params:netconf:capability:url:1.0   |
   |                    |                                              |
   | :xpath             | urn:ietf:params:netconf:capability:xpath:1.0 |
   +--------------------+----------------------------------------------+

   Index value: The capability name.
























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11.  Authors and Acknowledgements

   This document was written by:

      Andy Bierman

      Ken Crozier, Cisco Systems

      Rob Enns, Juniper Networks

      Ted Goddard, IceSoft

      Eliot Lear, Cisco Systems

      Phil Shafer, Juniper Networks

      Steve Waldbusser

      Margaret Wasserman, ThingMagic

   The authors would like to acknowledge the members of the NETCONF
   working group.  In particular, we would like to thank Wes Hardaker
   for his persistance and patience in assisting us with security
   considerations.  We would also like to thank Randy Presuhn, Sharon
   Chisholm, Juergen Schoenwalder, Glenn Waters, David Perkins, Weijing
   Chen, Simon Leinen, Keith Allen, and Dave Harrington for all of their
   valuable advice.

12.  References

12.1.  Normative References

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

   [2]  Clark, J. and S. DeRose, "XML Path Language (XPath) Version
        1.0", World Wide Web Consortium Recommendation,
        http://www.w3.org/TR/1999/REC-xpath-19991116, November 1999.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Wasserman, M. and T. Goddard, "Using the NETCONF Configuration
        Protocol over Secure SHell (SSH)", RFC 4742, December 2006.





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   [5]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
        Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
        January 2005.

   [6]  Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An IETF
        URN Sub-namespace for Registered Protocol Parameters", BCP 73,
        RFC 3553, June 2003.

   [7]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
        January 2004.

12.2.  Informative References

   [8]   Clark, J., "XSL Transformations (XSLT) Version 1.0", World Wide
         Web Consortium Recommendation, http://www.w3.org/TR/1999/REC-
         xslt-19991116, November 1999.

   [9]   Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
         Protocol Version 1.1", RFC 4346, April 2006.

   [10]  Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) Protocol
         Architecture", RFC 4251, January 2006.

   [11]  Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote
         Authentication Dial In User Service (RADIUS)", RFC 2865,
         June 2000.

   [12]  Hollenbeck, S., Rose, M., and L. Masinter, "Guidelines for the
         Use of Extensible Markup Language (XML) within IETF Protocols",
         BCP 70, RFC 3470, January 2003.





















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Appendix A.  NETCONF Error List

   Tag:         in-use
   Error-type:  protocol, application
   Severity:    error
   Error-info:  none
   Description: The request requires a resource that already in use.

   Tag:         invalid-value
   Error-type:  protocol, application
   Severity:    error
   Error-info:  none
   Description: The request specifies an unacceptable value for one
                or more parameters.

   Tag:         too-big
   Error-type:  transport, rpc, protocol, application
   Severity:    error
   Error-info:  none
   Description: The request or response (that would be generated) is too
                large for the implementation to handle.

   Tag:         missing-attribute
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-attribute> : name of the missing attribute
                <bad-element> : name of the element that should
                contain the missing attribute
   Description: An expected attribute is missing.

   Tag:         bad-attribute
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-attribute> : name of the attribute w/ bad value
                <bad-element> : name of the element that contains
                the attribute with the bad value
   Description: An attribute value is not correct; e.g., wrong type,
                out of range, pattern mismatch.

   Tag:         unknown-attribute
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-attribute> : name of the unexpected attribute
                <bad-element> : name of the element that contains
                the unexpected attribute
   Description: An unexpected attribute is present.





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   Tag:         missing-element
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-element> : name of the missing element
   Description: An expected element is missing.

   Tag:         bad-element
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-element> : name of the element w/ bad value
   Description: An element value is not correct; e.g., wrong type,
                out of range, pattern mismatch.

   Tag:         unknown-element
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-element> : name of the unexpected element
   Description: An unexpected element is present.

   Tag:         unknown-namespace
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  <bad-element> : name of the element that contains
                the unexpected namespace
                <bad-namespace> : name of the unexpected namespace
   Description: An unexpected namespace is present.

   Tag:         access-denied
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  none
   Description: Access to the requested RPC, protocol operation,
                or data model is denied because authorization failed.

   Tag:         lock-denied
   Error-type:  protocol
   Severity:    error
   Error-info:  <session-id> : session ID of session holding the
                requested lock, or zero to indicate a non-NETCONF
                entity holds the lock
   Description: Access to the requested lock is denied because the
                lock is currently held by another entity.









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   Tag:         resource-denied
   Error-type:  transport, rpc, protocol, application
   Severity:    error
   Error-info:  none
   Description: Request could not be completed because of insufficient
                resources.

   Tag:         rollback-failed
   Error-type:  protocol, application
   Severity:    error
   Error-info:  none
   Description: Request to rollback some configuration change (via
                rollback-on-error or discard-changes operations) was
                not completed for some reason.

   Tag:         data-exists
   Error-type:  application
   Severity:    error
   Error-info:  none
   Description: Request could not be completed because the relevant
                data model content already exists. For example,
                a 'create' operation was attempted on data that
                already exists.

   Tag:         data-missing
   Error-type:  application
   Severity:    error
   Error-info:  none
   Description: Request could not be completed because the relevant
                data model content does not exist.  For example,
                a 'replace' or 'delete' operation was attempted on
                data that does not exist.

   Tag:         operation-not-supported
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  none
   Description: Request could not be completed because the requested
                operation is not supported by this implementation.

   Tag:         operation-failed
   Error-type:  rpc, protocol, application
   Severity:    error
   Error-info:  none
   Description: Request could not be completed because the requested
                operation failed for some reason not covered by
                any other error condition.




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   Tag:         partial-operation
   Error-type:  application
   Severity:    error
   Error-info:  <ok-element> : identifies an element in the data model
                for which the requested operation has been completed
                for that node and all its child nodes.  This element
                can appear zero or more times in the <error-info>
                container.

                <err-element> : identifies an element in the data model
                for which the requested operation has failed for that
                node and all its child nodes.  This element
                can appear zero or more times in the <error-info>
                container.

                <noop-element> : identifies an element in the data model
                for which the requested operation was not attempted for
                that node and all its child nodes.  This element
                can appear zero or more times in the <error-info>
                container.
   Description: Some part of the requested operation failed or was
                not attempted for some reason.  Full cleanup has
                not been performed (e.g., rollback not supported)
                by the server.  The error-info container is used
                to identify which portions of the application
                data model content for which the requested operation
                has succeeded (<ok-element>), failed (<bad-element>),
                or not been attempted (<noop-element>).























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Appendix B.  XML Schema for NETCONF RPC and Protocol Operations

   BEGIN

   <?xml version="1.0" encoding="UTF-8"?>
   <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
              targetNamespace="urn:ietf:params:xml:ns:netconf:base:1.0"
              elementFormDefault="qualified"
              attributeFormDefault="unqualified"
              xml:lang="en">
     <!--
       import standard XML definitions
       -->
     <xs:import namespace="http://www.w3.org/XML/1998/namespace"
                schemaLocation="http://www.w3.org/2001/xml.xsd">
       <xs:annotation>
         <xs:documentation>
           This import accesses the xml: attribute groups for the
           xml:lang as declared on the error-message element.
         </xs:documentation>
       </xs:annotation>
     </xs:import>
     <!--
       message-id attribute
       -->
     <xs:simpleType name="messageIdType">
       <xs:restriction base="xs:string">
         <xs:maxLength value="4095"/>
       </xs:restriction>
     </xs:simpleType>
     <!--
       Types used for session-id
     -->
     <xs:simpleType name="SessionId">
       <xs:restriction base="xs:unsignedInt">
         <xs:minInclusive value="1"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="SessionIdOrZero">
       <xs:restriction base="xs:unsignedInt"/>
     </xs:simpleType>
     <!--
       <rpc> element
       -->
     <xs:complexType name="rpcType">
       <xs:sequence>
         <xs:element ref="rpcOperation"/>



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       </xs:sequence>
       <xs:attribute name="message-id" type="messageIdType"
         use="required"/>
       <!--
         Arbitrary attributes can be supplied with <rpc> element.
       -->
       <xs:anyAttribute processContents="lax"/>
     </xs:complexType>
     <xs:element name="rpc" type="rpcType"/>
     <!--
       data types and elements used to construct rpc-errors
       -->
     <xs:simpleType name="ErrorType">
       <xs:restriction base="xs:string">
         <xs:enumeration value="transport"/>
         <xs:enumeration value="rpc"/>
         <xs:enumeration value="protocol"/>
         <xs:enumeration value="application"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="ErrorTag">
       <xs:restriction base="xs:string">
         <xs:enumeration value="in-use"/>
         <xs:enumeration value="invalid-value"/>
         <xs:enumeration value="too-big"/>
         <xs:enumeration value="missing-attribute"/>
         <xs:enumeration value="bad-attribute"/>
         <xs:enumeration value="unknown-attribute"/>
         <xs:enumeration value="missing-element"/>
         <xs:enumeration value="bad-element"/>
         <xs:enumeration value="unknown-element"/>
         <xs:enumeration value="unknown-namespace"/>
         <xs:enumeration value="access-denied"/>
         <xs:enumeration value="lock-denied"/>
         <xs:enumeration value="resource-denied"/>
         <xs:enumeration value="rollback-failed"/>
         <xs:enumeration value="data-exists"/>
         <xs:enumeration value="data-missing"/>
         <xs:enumeration value="operation-not-supported"/>
         <xs:enumeration value="operation-failed"/>
         <xs:enumeration value="partial-operation"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:simpleType name="ErrorSeverity">
       <xs:restriction base="xs:string">
         <xs:enumeration value="error"/>
         <xs:enumeration value="warning"/>
       </xs:restriction>



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     </xs:simpleType>
     <xs:complexType name="errorInfoType">
       <xs:sequence>
         <xs:choice>
           <xs:element name="session-id" type="SessionIdOrZero"/>
           <xs:sequence minOccurs="0" maxOccurs="unbounded">
             <xs:sequence>
               <xs:element name="bad-attribute" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
               <xs:element name="bad-element" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
               <xs:element name="ok-element" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
               <xs:element name="err-element" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
               <xs:element name="noop-element" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
               <xs:element name="bad-namespace" type="xs:QName"
                 minOccurs="0" maxOccurs="1"/>
             </xs:sequence>
           </xs:sequence>
         </xs:choice>
         <!-- elements from any other namespace are also allowed
              to follow the NETCONF elements -->
         <xs:any namespace="##other"
           minOccurs="0" maxOccurs="unbounded"/>
       </xs:sequence>
     </xs:complexType>
     <xs:complexType name="rpcErrorType">
       <xs:sequence>
         <xs:element name="error-type" type="ErrorType"/>
         <xs:element name="error-tag" type="ErrorTag"/>
         <xs:element name="error-severity" type="ErrorSeverity"/>
         <xs:element name="error-app-tag" type="xs:string"
                     minOccurs="0"/>
         <xs:element name="error-path" type="xs:string" minOccurs="0"/>
         <xs:element name="error-message" minOccurs="0">
           <xs:complexType>
             <xs:simpleContent>
               <xs:extension base="xs:string">
                 <xs:attribute ref="xml:lang" use="optional"/>
               </xs:extension>
             </xs:simpleContent>
           </xs:complexType>
         </xs:element>
         <xs:element name="error-info" type="errorInfoType"
           minOccurs="0"/>
       </xs:sequence>



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     </xs:complexType>
     <!--
       <rpc-reply> element
       -->
     <xs:complexType name="rpcReplyType">
       <xs:choice>
         <xs:element name="ok"/>
         <xs:group ref="rpcResponse"/>
       </xs:choice>
       <xs:attribute name="message-id" type="messageIdType"
         use="optional"/>
       <!--
         Any attributes supplied with <rpc> element must be returned
         on <rpc-reply>.
       -->
       <xs:anyAttribute processContents="lax"/>
     </xs:complexType>
     <xs:group name="rpcResponse">
       <xs:sequence>
         <xs:element name="rpc-error" type="rpcErrorType"
           minOccurs="0" maxOccurs="unbounded"/>
         <xs:element name="data" type="dataInlineType" minOccurs="0"/>
       </xs:sequence>
     </xs:group>
     <xs:element name="rpc-reply" type="rpcReplyType"/>
     <!--
       Type for <test-option> parameter to <edit-config>
       -->
     <xs:simpleType name="testOptionType">
       <xs:restriction base="xs:string">
         <xs:enumeration value="test-then-set"/>
         <xs:enumeration value="set"/>
       </xs:restriction>
     </xs:simpleType>
     <!--
       Type for <error-option> parameter to <edit-config>
       -->
     <xs:simpleType name="errorOptionType">
       <xs:restriction base="xs:string">
         <xs:annotation>
           <xs:documentation>
             Use of the rollback-on-error value requires
             the :rollback-on-error capability.
           </xs:documentation>
         </xs:annotation>
         <xs:enumeration value="stop-on-error"/>
         <xs:enumeration value="continue-on-error"/>
         <xs:enumeration value="rollback-on-error"/>



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       </xs:restriction>
     </xs:simpleType>
     <!--
       rpcOperationType: used as a base type for all
       NETCONF operations
       -->
     <xs:complexType name="rpcOperationType"/>
     <xs:element name="rpcOperation"
                 type="rpcOperationType" abstract="true"/>
     <!--
       Type for <config> element
       -->
     <xs:complexType name="configInlineType">
       <xs:complexContent>
         <xs:extension base="xs:anyType"/>
       </xs:complexContent>
     </xs:complexType>
     <!--
       Type for <data> element
       -->
     <xs:complexType name="dataInlineType">
       <xs:complexContent>
         <xs:extension base="xs:anyType"/>
       </xs:complexContent>
     </xs:complexType>
     <!--
       Type for <filter> element
       -->
     <xs:simpleType name="FilterType">
       <xs:restriction base="xs:string">
         <xs:annotation>
           <xs:documentation>
             Use of the xpath value requires the :xpath capability.
          </xs:documentation>
         </xs:annotation>
         <xs:enumeration value="subtree"/>
         <xs:enumeration value="xpath"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="filterInlineType">
       <xs:complexContent>
         <xs:extension base="xs:anyType">
           <xs:attribute name="type"
                         type="FilterType" default="subtree"/>
           <!-- if type="xpath", the xpath expression
           appears in the select element -->
           <xs:attribute name="select"/>
         </xs:extension>



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       </xs:complexContent>
     </xs:complexType>
     <!--
       configuration datastore names
       -->
     <xs:annotation>
       <xs:documentation>
         The startup datastore can be used only if the :startup
         capability is advertised.  The candidate datastore can
         be used only if the :candidate datastore is advertised.
        </xs:documentation>
     </xs:annotation>
     <xs:complexType name="configNameType"/>
     <xs:element name="config-name"
                 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"/>
     <!--
       operation attribute used in <edit-config>
       -->
     <xs:simpleType name="editOperationType">
       <xs:restriction base="xs:string">
         <xs:enumeration value="merge"/>
         <xs:enumeration value="replace"/>
         <xs:enumeration value="create"/>
         <xs:enumeration value="delete"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:attribute name="operation"
                   type="editOperationType" default="merge"/>
     <!--
       <default-operation> element
       -->
     <xs:simpleType name="defaultOperationType">
       <xs:restriction base="xs:string">
         <xs:enumeration value="merge"/>
         <xs:enumeration value="replace"/>
         <xs:enumeration value="none"/>
       </xs:restriction>
     </xs:simpleType>
     <!--
       <url> element
       -->
     <xs:complexType name="configURIType">



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       <xs:annotation>
         <xs:documentation>
           Use of the url element requires the :url capability.
         </xs:documentation>
       </xs:annotation>
       <xs:simpleContent>
         <xs:extension base="xs:anyURI"/>
       </xs:simpleContent>
     </xs:complexType>
     <!--
       Type for <source> element (except <get-config>)
       -->
     <xs:complexType name="rpcOperationSourceType">
       <xs:choice>
         <xs:element name="config" type="configInlineType"/>
         <xs:element ref="config-name"/>
         <xs:element name="url" type="configURIType"/>
       </xs:choice>
     </xs:complexType>
     <!--
       Type for <source> element in <get-config>
       -->
     <xs:complexType name="getConfigSourceType">
       <xs:choice>
         <xs:element ref="config-name"/>
         <xs:element name="url" type="configURIType"/>
       </xs:choice>
     </xs:complexType>
     <!--
       Type for <target> element
       -->
     <xs:complexType name="rpcOperationTargetType">
       <xs:choice>
         <xs:element ref="config-name"/>
         <xs:element name="url" type="configURIType"/>
       </xs:choice>
     </xs:complexType>
     <!--
       <get-config> operation
       -->
     <xs:complexType name="getConfigType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="source"
                         type="getConfigSourceType"/>
             <xs:element name="filter"
                         type="filterInlineType" minOccurs="0"/>



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           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="get-config" type="getConfigType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <edit-config> operation
       -->
     <xs:complexType name="editConfigType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:annotation>
               <xs:documentation>
                 Use of the test-option element requires the
                 :validate capability.  Use of the url element
                 requires the :url capability.
               </xs:documentation>
             </xs:annotation>
             <xs:element name="target"
                         type="rpcOperationTargetType"/>
             <xs:element name="default-operation"
                         type="defaultOperationType"
                         minOccurs="0"/>
             <xs:element name="test-option"
                         type="testOptionType"
                         minOccurs="0"/>
             <xs:element name="error-option"
                         type="errorOptionType"
                         minOccurs="0"/>
             <xs:choice>
               <xs:element name="config"
                           type="configInlineType"/>
               <xs:element name="url"
                           type="configURIType"/>
             </xs:choice>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="edit-config" type="editConfigType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <copy-config> operation
       -->
     <xs:complexType name="copyConfigType">
       <xs:complexContent>



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         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="target" type="rpcOperationTargetType"/>
             <xs:element name="source" type="rpcOperationSourceType"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="copy-config" type="copyConfigType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <delete-config> operation
       -->
     <xs:complexType name="deleteConfigType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="target" type="rpcOperationTargetType"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="delete-config" type="deleteConfigType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <get> operation
       -->
     <xs:complexType name="getType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="filter"
                         type="filterInlineType" minOccurs="0"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="get" type="getType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <lock> operation
       -->
     <xs:complexType name="lockType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="target"
                         type="rpcOperationTargetType"/>



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           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="lock" type="lockType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <unlock> operation
       -->
     <xs:complexType name="unlockType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="target" type="rpcOperationTargetType"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="unlock" type="unlockType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <validate> operation
       -->
     <xs:complexType name="validateType">
       <xs:annotation>
         <xs:documentation>
           The validate operation requires the :validate capability.
         </xs:documentation>
       </xs:annotation>
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="source" type="rpcOperationSourceType"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="validate" type="validateType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <commit> operation
       -->
     <xs:simpleType name="confirmTimeoutType">
       <xs:restriction base="xs:unsignedInt">
         <xs:minInclusive value="1"/>
       </xs:restriction>
     </xs:simpleType>
     <xs:complexType name="commitType">



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       <xs:annotation>
         <xs:documentation>
           The commit operation requires the :candidate capability.
         </xs:documentation>
       </xs:annotation>
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:annotation>
               <xs:documentation>
                 Use of the confirmed and confirm-timeout elements
                 requires the :confirmed-commit capability.
               </xs:documentation>
             </xs:annotation>
             <xs:element name="confirmed" minOccurs="0"/>
             <xs:element name="confirm-timeout"
                         type="confirmTimeoutType"
                         minOccurs="0"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="commit" type="commitType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <discard-changes> operation
       -->
     <xs:complexType name="discardChangesType">
       <xs:annotation>
         <xs:documentation>
           The discard-changes operation requires the
           :candidate capability.
         </xs:documentation>
       </xs:annotation>
       <xs:complexContent>
         <xs:extension base="rpcOperationType"/>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="discard-changes"
                 type="discardChangesType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <close-session> operation
       -->
     <xs:complexType name="closeSessionType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType"/>
       </xs:complexContent>



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     </xs:complexType>
     <xs:element name="close-session" type="closeSessionType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <kill-session> operation
       -->
     <xs:complexType name="killSessionType">
       <xs:complexContent>
         <xs:extension base="rpcOperationType">
           <xs:sequence>
             <xs:element name="session-id"
                         type="SessionId" minOccurs="1"/>
           </xs:sequence>
         </xs:extension>
       </xs:complexContent>
     </xs:complexType>
     <xs:element name="kill-session" type="killSessionType"
                 substitutionGroup="rpcOperation"/>
     <!--
       <hello> element
       -->
     <xs:element name="hello">
       <xs:complexType>
         <xs:sequence>
           <xs:element name="capabilities">
             <xs:complexType>
               <xs:sequence>
                 <xs:element name="capability" type="xs:anyURI"
                   maxOccurs="unbounded"/>
               </xs:sequence>
             </xs:complexType>
           </xs:element>
           <xs:element name="session-id"
                       type="SessionId" minOccurs="0"/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>
   </xs:schema>

   END











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Appendix C.  Capability Template

C.1.  capability-name (template)

C.1.1.  Overview

C.1.2.  Dependencies

C.1.3.  Capability Identifier

   The {name} capability is identified by the following capability
   string:

      {capability uri}

C.1.4.  New Operations

C.1.4.1.  <op-name>

C.1.5.  Modifications to Existing Operations

C.1.5.1.  <op-name>

   If existing operations are not modified by this capability, this
   section may be omitted.

C.1.6.  Interactions with Other Capabilities

   If this capability does not interact with other capabilities, this
   section may be omitted.





















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Appendix D.  Configuring Multiple Devices with NETCONF

D.1.  Operations on Individual Devices

   Consider the work involved in performing a configuration update
   against a single individual device.  In making a change to the
   configuration, the application needs to build trust that its change
   has been made correctly and that it has not impacted the operation of
   the device.  The application (and the application user) should feel
   confident that their change has not damaged the network.

   Protecting each individual device consists of a number of steps:

   o  Acquiring the configuration lock.

   o  Loading the update.

   o  Validating the incoming configuration.

   o  Checkpointing the running configuration.

   o  Changing the running configuration.

   o  Testing the new configuration.

   o  Making the change permanent (if desired).

   o  Releasing the configuration lock.

   Let's look at the details of each step.

D.1.1.  Acquiring the Configuration Lock

   A lock should be acquired to prevent simultaneous updates from
   multiple sources.  If multiple sources are affecting the device, the
   application is hampered in both testing of its change to the
   configuration and in recovery should the update fail.  Acquiring a
   short-lived lock is a simple defense to prevent other parties from
   introducing unrelated changes.

   The lock can be acquired using the <lock> operation.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <lock>
         <target>
           <running/>
         </target>



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       </lock>
     </rpc>

D.1.2.  Loading the Update

   The configuration can be loaded onto the device without impacting the
   running system.  If the :url capability is supported and lists "file"
   as a supported scheme, incoming changes can be placed in a local
   file.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <copy-config>
         <target>
           <url>file://incoming.conf</url>
         </target>
         <source>
           <config>
             <!-- place incoming configuration here -->
           </config>
         </source>
       </copy-config>
     </rpc>

   If the :candidate capability is supported, the candidate
   configuration can be used.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <candidate/>
         </target>
         <config>
           <!-- place incoming configuration here -->
         </config>
       </edit-config>
     </rpc>

   If the update fails, the user file can be deleted using the
   <delete-config> operation, or the candidate configuration can be
   reverted using the <discard-changes> operation.









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D.1.3.  Validating the Incoming Configuration

   Before the incoming configuration is applied, validating it is often
   useful.  Validation allows the application to gain confidence that
   the change will succeed and simplifies recovery if it does not.

   If the device supports the :url capability and lists "file" as a
   supported scheme, use the <validate> operation with the <source>
   parameter set to the proper user file:

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <validate>
         <source>
           <url>file://incoming.conf</url>
         </source>
       </validate>
     </rpc>

   If the device supports the :candidate capability, some validation
   will be performed as part of loading the incoming configuration into
   the candidate.  For full validation, either pass the <validate>
   parameter during the <edit-config> step given above, or use the
   <validate> operation with the <source> parameter set to <candidate>.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <validate>
         <source>
           <candidate/>
         </source>
       </validate>
     </rpc>

D.1.4.  Checkpointing the Running Configuration

   The running configuration can be saved into a local file as a
   checkpoint before loading the new configuration.  If the update
   fails, the configuration can be restored by reloading the checkpoint
   file.

   The checkpoint file can be created using the <copy-config> operation.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <copy-config>
         <target>
           <url>file://checkpoint.conf</url>



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         </target>
         <source>
           <running/>
         </source>
       </copy-config>
     </rpc>

   To restore the checkpoint file, reverse the source and target
   parameters.

D.1.5.  Changing the Running Configuration

   When the incoming configuration has been safely loaded onto the
   device and validated, it is ready to impact the running system.

   If the device supports the :url capability and lists "file" as a
   supported scheme, use the <edit-config> operation to merge the
   incoming configuration into the running configuration.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <config>
           <url>file://incoming.conf</url>
         </config>
       </edit-config>
     </rpc>

   If the device supports the :candidate capability, use the <commit>
   operation to set the running configuration to the candidate
   configuration.  Use the <confirmed> parameter to allow automatic
   reversion to the original configuration if connectivity to the device
   fails.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <commit>
         <confirmed/>
         <confirm-timeout>120</confirm-timeout>
       </commit>
     </rpc>







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D.1.6.  Testing the New Configuration

   Now that the incoming configuration has been integrated into the
   running configuration, the application needs to gain trust that the
   change has affected the device in the way intended without affecting
   it negatively.

   To gain this confidence, the application can run tests of the
   operational state of the device.  The nature of the test is dependent
   on the nature of the change and is outside the scope of this
   document.  Such tests may include reachability from the system
   running the application (using ping), changes in reachability to the
   rest of the network (by comparing the device's routing table), or
   inspection of the particular change (looking for operational evidence
   of the BGP peer that was just added).

D.1.7.  Making the Change Permanent

   When the configuration change is in place and the application has
   sufficient faith in the proper function of this change, the
   application should make the change permanent.

   If the device supports the :startup capability, the current
   configuration can be saved to the startup configuration by using the
   startup configuration as the target of the <copy-config> operation.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <copy-config>
         <target>
           <startup/>
         </target>
         <source>
           <running/>
         </source>
       </copy-config>
     </rpc>

   If the device supports the :candidate capability and a confirmed
   commit was requested, the confirming commit must be sent before the
   timeout expires.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <commit/>
     </rpc>





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D.1.8.  Releasing the Configuration Lock

   When the configuration update is complete, the lock must be released,
   allowing other applications access to the configuration.

   Use the <unlock> operation to release the configuration lock.

     <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <unlock>
         <target>
           <running/>
         </target>
       </unlock>
     </rpc>

D.2.  Operations on Multiple Devices

   When a configuration change requires updates across a number of
   devices, care should be taken to provide the required transaction
   semantics.  The NETCONF protocol contains sufficient primitives upon
   which transaction-oriented operations can be built.  Providing
   complete transactional semantics across multiple devices is
   prohibitively expensive, but the size and number of windows for
   failure scenarios can be reduced.

   There are two classes of multi-device operations.  The first class
   allows the operation to fail on individual devices without requiring
   all devices to revert to their original state.  The operation can be
   retried at a later time, or its failure simply reported to the user.
   An example of this class might be adding an NTP server.  For this
   class of operations, failure avoidance and recovery are focused on
   the individual device.  This means recovery of the device, reporting
   the failure, and perhaps scheduling another attempt.

   The second class is more interesting, requiring that the operation
   should complete on all devices or be fully reversed.  The network
   should either be transformed into a new state or be reset to its
   original state.  For example, a change to a VPN may require updates
   to a number of devices.  Another example of this might be adding a
   class-of-service definition.  Leaving the network in a state where
   only a portion of the devices have been updated with the new
   definition will lead to future failures when the definition is
   referenced.

   To give transactional semantics, the same steps used in single device
   operations listed above are used, but are performed in parallel
   across all devices.  Configuration locks should be acquired on all



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   target devices and kept until all devices are updated and the changes
   made permanent.  Configuration changes should be uploaded and
   validation performed across all devices.  Checkpoints should be made
   on each device.  Then the running configuration can be changed,
   tested, and made permanent.  If any of these steps fail, the previous
   configurations can be restored on any devices upon which they were
   changed.  After the changes have been completely implemented or
   completely discarded, the locks on each device can be released.

Appendix E.  Deferred Features

   The following features have been deferred until a future revision of
   this document.

   o  Granular locking of configuration objects.

   o  Named configuration files/datastores.

   o  Support for multiple NETCONF channels.

   o  Asynchronous notifications.

   o  Explicit protocol support for rollback of configuration changes to
      prior versions.



























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Editor's Address

   Rob Enns
   Juniper Networks
   1194 North Mathilda Ave
   Sunnyvale, CA  94089
   US

   EMail: rpe@juniper.net










































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Full Copyright Statement

   Copyright (C) The IETF Trust (2006).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.






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