RFC 4741
NETCONF Configuration Protocol
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.
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
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
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
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.
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.
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
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.
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.
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:
<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>
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
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
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>
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>
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.
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.
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