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draft-ietf-netmod-system-config.xml
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<?xml version="1.0" encoding="US-ASCII"?>
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<rfc category="std" docName="draft-ietf-netmod-system-config-latest"
ipr="trust200902" submissionType="IETF" updates="8342">
<front>
<title abbrev="System-defined Configuration">System-defined
Configuration</title>
<author fullname="Qiufang Ma" initials="Q." role="editor" surname="Ma">
<organization>Huawei</organization>
<address>
<postal>
<street>101 Software Avenue, Yuhua District</street>
<city>Nanjing</city>
<region>Jiangsu</region>
<code>210012</code>
<country>China</country>
</postal>
<email>maqiufang1@huawei.com</email>
</address>
</author>
<author fullname="Qin Wu" initials="Q." surname="Wu">
<organization>Huawei</organization>
<address>
<postal>
<street>101 Software Avenue, Yuhua District</street>
<city>Nanjing</city>
<region>Jiangsu</region>
<code>210012</code>
<country>China</country>
</postal>
<email>bill.wu@huawei.com</email>
</address>
</author>
<author fullname="Chong Feng" initials="C." surname="Feng">
<organization/>
<address>
<email>fengchongllly@gmail.com</email>
</address>
</author>
<date year="2024"/>
<area>ops</area>
<workgroup>NETMOD</workgroup>
<keyword>system config</keyword>
<abstract>
<t>The Network Management Datastore Architecture (NMDA) in RFC 8342
defines several configuration datastores holding configuration. The
contents of these configuration datastores are controlled by clients.
This document introduces the concept of system configuration datastore
holding configuration controlled by the system on which a server is
running. The system configuration can be referenced (e.g., leafref) by
configuration explicitly created by clients.</t>
<t>This document updates RFC 8342.</t>
</abstract>
</front>
<middle>
<section anchor="Introduction" title="Introduction">
<t>The Network Management Datastore Architecture (NMDA) <xref
target="RFC8342"/> defines system configuration as the configuration
that is supplied by the device itself and appears in <operational>
when it is in use (Figure 2 in <xref target="RFC8342"/>).</t>
<t>However, there is a desire to enable a server to better expose the
system configuration, regardless of whether it is in use. For example,
some implementations defines the system configuration which must be
referenced to be active. NETCONF/RESTCONF clients can benefit from a
standard mechanism to retrieve what system configuration is available on
a server.</t>
<t>Some servers allow the descendant nodes of system-defined
configuration to be configured or modified. For example, the system
configuration may contain an almost empty physical interface, while the
client needs to be able to add, modify, or remove a number of descendant
nodes. Some descendant nodes may not be modifiable (e.g., the interface
"type" set by the system).</t>
<t>This document updates the NMDA defined in <xref target="RFC8342"/>
with a read-only conventional configuration datastore called "system" to
expose system-defined configuration. The solution enables configuration
explicitly created by the clients to reference nodes defined in
<system>, override system-provided values, and configure
descendant nodes of system-defined configuration.</t>
<t>The solution defined in this document requires the use of NMDA for
both clients and servers. Conformance to this document requires NMDA
servers implement the "ietf-system-datastore" YANG module (<xref
target="system-datastore"/>).</t>
<section anchor="terminology" title="Terminology">
<t>This document assumes that the reader is familiar with the contents
of <xref target="RFC6241"/>, <xref target="RFC7950"/>, <xref
target="RFC8342"/>, <xref target="RFC8407"/>, and <xref
target="RFC8525"/> and uses terminologies from those documents.</t>
<t>The following terms are defined in this document:<list
style="hanging">
<t hangText="system configuration: ">Configuration that is
provided by the system itself. System configuration is present in
the system configuration datastore (regardless of whether it is
applied or referenced). It is a different and separate concept
from factory default configuration defined in <xref
target="RFC8808"/> (which represents a preset initial
configuration that is used to initialize the configuration of a
server). System configuration may also be referred to as
"system-defined configuration" or "system-provided configuration"
throughout this document.</t>
<t hangText="system configuration datastore: ">A configuration
datastore holding configuration provided by the system itself.
This datastore is referred to as "<system>".</t>
</list>This document redefines the term "conventional configuration
datastore" in <xref section="3" sectionFormat="of" target="RFC8342"/>
to add "system" to the list of conventional configuration
datastores:<list style="hanging">
<t hangText="conventional configuration datastore: ">One of the
following set of configuration datastores: <running>,
<startup>, <candidate>, <system>, and
<intended>. These datastores share a common datastore
schema, and protocol operations allow copying data between these
datastores. The term "conventional" is chosen as a generic
umbrella term for these datastores.</t>
<t hangText="system node: ">An instance in the data tree that is
provided by the system itself. System node may also be called
"system-defined node" or "system-provided node" throughout this
document.</t>
<t hangText="referenced node: ">A referenced node is one of:<list
style="symbols">
<t>Targets of leafref values defined via the "path"
statement.</t>
<t>Targets of "instance-identifier" type values.</t>
<t>Nodes present in an XPath expression of "when"
constraints.</t>
<t>Nodes present in an XPath expression of "must"
constraints.</t>
<t>Nodes defined to satisfy the "mandatory true"
constraints.</t>
<t>Nodes defined to satisfy the "min-elements"
constraints.</t>
</list></t>
</list></t>
</section>
<section title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only
when, they appear in all capitals, as shown here.</t>
</section>
<section title="Updates to RFC 8342">
<t>This document updates <xref format="none" target="RFC8342">RFC
8342</xref> to define a configuration datastore called "system" to
hold system configuration (<xref target="system-ds-def"/>), it also
redefines the term "conventional configuration datastore" from <xref
target="RFC8342"/> to add "system" to the list of conventional
configuration datastores.</t>
<t>Configuration in <running> is merged with <system> to
create the contents of <intended> after the configuration
transformations (e.g., template expansion, removal of inactive
configuration defined in <xref target="RFC8342"/>) have been
performed, as described in <xref target="conceptual-model"/>.</t>
<t>This document also updates the definition of "intended" origin
metadata annotation identity defined in <xref section="5.3.4"
sectionFormat="of" target="RFC8342"/>. The "intended" identity of
origin value defined in <xref target="RFC8342"/> represents the origin
of configuration provided by <intended>, this document updates
its definition as the origin source of configuration explicitly
provided by <running>, and allows a subset of configuration in
<intended> that flows from <system> yet is not configured
or overridden explicitly in <running> to use "system" as its
origin value.</t>
</section>
</section>
<section anchor="categories" title="Kinds of System Configuration">
<t>This document defines two types of system configuration.
Configuration that is immediately-present and configuration that is
conditionally-present. These types of system configuration are described
in <xref target="immediate"/> and <xref target="conditional"/>,
respectively.</t>
<section anchor="immediate" title="Immediately-Present">
<t>Immediately-present refers to system configuration which is
generated in <system> when the device is powered on,
irrespective of physical resource present or not, a special
functionality enabled or not. An example of immediately-present system
configuration is an always-existing loopback interface.</t>
</section>
<section anchor="conditional" title="Conditionally-Present">
<t>Conditionally-present refers to system configuration which is
generated in <system> based on specific conditions being met in
a system. For example, if a physical resource is present (e.g., an
interface card is inserted), the system automatically detects it and
loads associated configuration; when the physical resource is not
present (an interface card is removed), the system configuration will
be automatically cleared. Another example is when a special
functionality is enabled, e.g., when a license or feature is enabled,
specific configuration may be created by the system.</t>
</section>
</section>
<section anchor="system-ds-def"
title="The System Configuration Datastore (<system>)">
<t>Following guidelines for defining datastores in the <xref section="A"
sectionFormat="of" target="RFC8342"/>, this document introduces a new
datastore resource named "system" that represents the system
configuration. NMDA servers compliant with this document MUST implement
a system configuration datastore, and they SHOULD also implement
<intended>.</t>
<t><list style="symbols">
<t>Name: "system".</t>
<t>YANG modules: all.</t>
<t>YANG nodes: all "config true" data nodes up to the root of the
tree, generated by the system.</t>
<t>Management operations: The datastore can be read using network
management protocols such as NETCONF and RESTCONF, but its contents
cannot be changed by manage operations via NETCONF and RESTCONF
protocols.</t>
<t>Origin: This document does not define any new origin identity.
The "system" identity of origin metadata annotation <xref
target="RFC7952"/> is used to indicate the origin of a data item
provided by the system.</t>
<t>Protocols: YANG-driven management protocols, such as NETCONF and
RESTCONF.</t>
<t>Defining YANG module: "ietf-system-datastore" (<xref
target="system-datastore"/>).</t>
</list></t>
<t>The system configuration datastore doesn't persist across
reboots.</t>
</section>
<section anchor="conceptual-model" title="Conceptual Model of Datastores">
<t>Clients may provide configuration nodes that reference nodes defined
in <system>, override system-provided values, and configure
descendant nodes of system-defined configuration in <running>, as
detailed in <xref target="dynamic"/>.</t>
<t>To ensure the validity of <intended>, configuration in
<running> is merged with <system> to become
<intended>, in which process, configuration appearing in
<running> takes precedence over the same node in <system>.
Since it is unspecified how to merge configuration before
transformations, if <system> or <running> includes
configuration that requires further transformation (e.g., template
expansion, removal of inactive configuration defined in <xref
target="RFC8342"/>) before it can be applied, configuration
transformations MUST be performed before <running> is merged with
<system>.</t>
<t>Whenever configuration in <system> changes, the server MUST
also immediately update and validate <intended>.</t>
<t>As a result, Figure 2 in <xref section="5" sectionFormat="of"
target="RFC8342"/> is updated with the below conceptual model of
datastores which incorporates the system configuration datastore.<figure
align="center" title="Architectural Model of Datastores">
<artwork> +-------------+ +-----------+
| <candidate> | | <startup> |
| (ct, rw) |<---+ +---->| (ct, rw) |
+-------------+ | | +-----------+
| | | |
+-----------+ | +-----------+ |
| <system> | +------->| <running> |<--------+
| (ct, ro) | | (ct, rw) |
+-----------+ +-----------+
| |
| |
| | // configuration transformations,
+--------------+---------------+ // e.g., removal of nodes marked
| // as "inactive", expansion of
| // templates
v
+------------+
| <intended> | // subject to validation
| (ct, ro) |
+------------+
| // changes applied, subject to
| // local factors, e.g., missing
| // resources, delays
dynamic |
configuration | +-------- learned configuration
datastores -----+ | +-------- default configuration
| | |
v v v
+---------------+
| <operational> | <-- system state
| (ct + cf, ro) |
+---------------+
ct = config true; cf = config false
rw = read-write; ro = read-only
boxes denote named datastores</artwork>
</figure></t>
<t>Configuration in <system> is undeletable to clients (e.g., a
system-defined list entry can never be removed), even though a node
defined in <system> may be overridden in <running>. If it is
desired to enable a client to delete system configuration, it can be
approximated using <factory-default>, as described in <xref
target="factory"/>. If system initializes a value for a particular leaf
which is overridden by the client with a different value in
<running> (<xref target="modifying"/>), the node in
<running> may be removed later, in which case system-initialized
value defined in <system> may still be in use and appear in
<operational>.</t>
</section>
<section title="Static Characteristics">
<section title="Read-only to Clients">
<t>The system datastore is read-only (i.e., edits towards
<system> directly MUST be denied), though the client may be
allowed to provide configuration that overrides the value of a
system-initialized node (see <xref target="modifying"/>).</t>
</section>
<section title="No Impact to <operational>">
<t>This work has no impact to <operational>. Notably, it does
not define any new origin identity as it is able to use the existing
"system" identity defined in <xref section="5.3.4" sectionFormat="of"
target="RFC8342"/>. <system> enables system-generated nodes to
be defined like configuration, i.e., made visible to clients in order
for being referenced or configurable prior to present in
<operational>. "config false" nodes are out of scope, hence
existing "config false" nodes are not impacted by this work.</t>
</section>
</section>
<section anchor="dynamic" title="Dynamic Behaviors">
<section title="May Change via Software Upgrades or Resource Changes">
<t>The contents of <system> MAY change dynamically under various
conditions, such as license change, software upgrade, and
system-controlled resources change (see <xref target="conditional"/>).
The updates of system configuration may be obtained through YANG
notifications (e.g., on-change notification) <xref
target="RFC8639"/><xref target="RFC8641"/>.</t>
</section>
<section anchor="declare" title="Referencing System Configuration">
<t>Clients may create configuration data in <running> that
references nodes in <system>. Some implementations may define
system nodes solely as a convenience for clients to reference. It is
also possible for the clients to define their customized nodes for
reference.</t>
<t><xref target="declare-example"/> provides an example of a client
referencing system-defined nodes.</t>
</section>
<section anchor="modifying"
title="Modifying (Overriding) System Configuration">
<t>In some cases, a server may allow some parts of system
configuration (e.g., a leaf's value) to be modified. Modification of
system configuration is achieved by the client writing configuration
data in <running> that overrides the values of matched
configuration nodes at the corresponding level in <system>.
Configurations defined in <running> take precedence over system
configuration nodes in <system> if the server allows the nodes
to be modified. The immutability of system configuration is defined in
<xref target="I-D.ietf-netmod-immutable-flag"/>.</t>
<t><xref target="modify-example"/> provides an example of a client
overriding a system-instantiated leaf's value.</t>
</section>
<section title="Configuring Descendant nodes of System Configuration">
<t>A server may also allow a client to add nodes to a list entry in
<system> by writing those additional nodes in <running>.
Those additional data nodes may not exist in <system> (i.e., an
addition rather than an override).</t>
<t><xref target="configure-example"/> provides an example of a client
configuring descendant nodes of a system-defined node.</t>
</section>
</section>
<section title="Relationships to Other Datastores">
<t>This section discusses the interesting relationships of
<system> to other datastores known at the time of this
writing.</t>
<section anchor="factory"
title="The "factory-default" Datastore">
<t>Any deletable system-provided configuration that is populated as
part of <running> by the system at boot up, without being part
of the contents of a <startup> datastore, must be defined in
<factory-default> <xref target="RFC8808"/>, which is used to
initialize <running> when the device is first-time powered on or
reset to its factory default condition.</t>
<t>The <factory-reset> RPC operation can reset <system> to
its factory default contents.</t>
</section>
</section>
<section anchor="system-datastore"
title="The "ietf-system-datastore" Module">
<section title="Data Model Overview">
<t>This YANG module defines a new YANG identity named "system" that
uses the "ds: conventional" identity defined in <xref
target="RFC8342"/> as its base. A client can discover the system
configuration datastore support on the server by reading the YANG
library information from the operational state datastore.</t>
<t>The system datastore is defined as a conventional configuration
datastore and shares a common datastore schema with other conventional
datastores.</t>
<t>The following diagram illustrates the relationship amongst the
"identity" statements defined in the "ietf-system-datastore" and
"ietf-datastores" YANG modules: <figure>
<artwork>Identities:
+--- datastore
| +--- conventional
| | +--- running
| | +--- candidate
| | +--- startup
| | +--- system
| | +--- intended
| +--- dynamic
| +--- operational</artwork>
</figure>The diagram above uses syntax that is similar to but not
defined in <xref target="RFC8340"/>.</t>
</section>
<section title="YANG Module">
<figure>
<preamble><CODE BEGINS> file
"ietf-system-datastore@YYYY-MM-DD.yang"</preamble>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(yang/ietf-system-datastore@YYYY-MM-DD.yang)
]]></artwork>
<postamble><CODE ENDS></postamble>
</figure>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<section title="The "IETF XML" Registry">
<t>This document registers two XML namespace URNs in the 'IETF XML
registry', following the format defined in <xref
target="RFC3688"/>.</t>
<figure>
<artwork> URI: urn:ietf:params:xml:ns:yang:ietf-system-datastore
Registrant Contact: The IESG.
XML: N/A, the requested URIs are XML namespaces.</artwork>
</figure>
</section>
<section title="The "YANG Module Names" Registry">
<t>This document registers two module names in the 'YANG Module Names'
registry, defined in <xref target="RFC6020"/>.</t>
<figure>
<artwork> name: ietf-system-datastore
prefix: sysds
namespace: urn:ietf:params:xml:ns:yang:ietf-system-datatstore
maintained by IANA? N
RFC: XXXX // RFC Ed.: replace XXXX and remove this comment</artwork>
</figure>
</section>
</section>
<section anchor="scecurity" title="Security Considerations">
<t>This section is modeled after the template described in <xref
section="3.7" sectionFormat="of"
target="I-D.ietf-netmod-rfc8407bis"/>.</t>
<t>The "ietf-system-datastore" YANG module defines a data model that is
designed to be accessed via YANG-based management protocols, such as
NETCONF <xref target="RFC6241"/> and RESTCONF <xref target="RFC8040"/>.
These protocols have to use a secure transport layer (e.g., SSH <xref
target="RFC4252"/>, TLS <xref target="RFC8446"/>, and QUIC <xref
target="RFC9000"/>) and have to use mutual authentication.</t>
<t>The Network Configuration Access Control Model (NACM) <xref
target="RFC8341"/> provides the means to restrict access for particular
NETCONF or RESTCONF users to a preconfigured subset of all available
NETCONF or RESTCONF protocol operations and content.</t>
<t>The YANG module only defines a identity that uses the
"ds:conventional" identity as its base. The module by itself does not
expose any data nodes that are writable, date nodes that contain
read-only state, or RPCs. As such, there are no additional security
issues related to the YANG module that need to be considered.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119.xml"?>
<?rfc include="reference.RFC.6241.xml"?>
<?rfc include="reference.RFC.7950.xml"?>
<?rfc include="reference.RFC.8040.xml"?>
<?rfc include="reference.RFC.8341.xml"?>
<?rfc include="reference.RFC.8342.xml"?>
<?rfc include="reference.RFC.8639.xml"?>
<?rfc include="reference.RFC.8641.xml"?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.3688.xml"?>
<?rfc include="reference.RFC.4252.xml"?>
<?rfc include="reference.RFC.6020.xml"?>
<?rfc include="reference.RFC.7952.xml"?>
<?rfc include="reference.RFC.8174.xml"?>
<?rfc include="reference.RFC.8340.xml"?>
<?rfc include="reference.RFC.8407.xml"?>
<?rfc include="reference.RFC.8446.xml"?>
<?rfc include="reference.RFC.8525.xml"?>
<?rfc include="reference.RFC.8808.xml"?>
<?rfc include="reference.RFC.9000.xml"?>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.ietf-netmod-immutable-flag.xml"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
<xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.ietf-netmod-rfc8407bis.xml"
xmlns:xi="http://www.w3.org/2001/XInclude"/>
</references>
<section title="Example of Dynamic Behaviors">
<t>This section presents some sample data models and corresponding
contents of various datastores with different dynamic behaviors
described in <xref target="dynamic"/>. The XML snippets are used only
for illustration purposes.</t>
<t/>
<section anchor="declare-example"
title="Referencing System-defined Nodes">
<t>In this subsection, the following fictional module is used:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/example-application.yang)
]]></artwork>
</figure>A fictional ACL YANG module is used as follows, which
defines a leafref for the leaf-list "application" data node to refer
to an existing application name.<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/example-acl.yang)
]]></artwork>
</figure></t>
<t>The server may predefine some applications as a convenience for
clients, these applications are immediately-present system
configuration. When the device is powered on, the system-instantiated
application entries may be present in <system> as follows:</t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/applications-system.xml)
]]></artwork>
</figure>
<t>The client may also define its customized applications. Suppose the
configuration of applications is present in <running> as
follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/applications-running.xml)
]]></artwork>
</figure></t>
<t>If a client configures an ACL rule referencing some system-provided
or customized applications, the configuration of ACL rule may be shown
as follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/applications-referenced.xml)
]]></artwork>
</figure></t>
<t>As different entries of application configuration in <system>
and <running> is merged to create <intended>,
<operational> might contain the configuration of applications as
follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/applications-declare-operational.xml)
]]></artwork>
</figure></t>
</section>
<section anchor="modify-example"
title="Modifying a System-instantiated Leaf's Value">
<t>This subsection uses the following fictional interface YANG
module:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/example-interface.yang)
]]></artwork>
</figure></t>
<t>Suppose the system provides an immediately-present loopback
interface (named "lo0") with a MTU value "65536", a default IPv4
address of "127.0.0.1", and a default IPv6 address of "::1". The
configuration of "lo0" interface is present in <system> as
follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/interface-system.xml)
]]></artwork>
</figure></t>
<t>A client modifies the value of MTU to 9216 and adds the following
configuration into <running> using a "merge" operation:</t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/interface-running-overridden.xml)
]]></artwork>
</figure>
<t>Then the configuration of interfaces is present in
<operational> as follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/interface-operational-overridden.xml)
]]></artwork>
</figure></t>
</section>
<section anchor="configure-example"
title="Configuring Descendant Nodes of a System-defined Node">
<t>In the above example, imagine the client further configures the
description node of a "lo0" interface in <running> using a
"merge" operation as follows:</t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/interface-running-addition.xml)
]]></artwork>
</figure>
<t>The configuration of interface "lo0" is present in
<operational> as follows:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/interface-operational-addition.xml)
]]></artwork>
</figure></t>
</section>
</section>
<section title="Key Use Cases">
<t>This section provides three use cases related to how <system>
interacts with other datastores (e.g., <candidate>,
<running>, <intended>, and <operational>). The
following fictional interface data model is used:<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(examples/example-interface-management.yang)
]]></artwork>
</figure>For each use case, corresponding sample configuration in
<running>, <system>, <intended> and
<operational> are shown. The XML snippets are used only for
illustration purposes.</t>
<section title="Device Powers On">
<t>When the device is powered on, suppose the system provides an
immediately-present loopback interface (named "lo0") which is not
explicitly configured in <running>. Thus, no configuration for
interfaces appears in <running>;</t>
<t>And the contents of <system> are:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>In this case, the configuration of loopback interface is only
present in <system>, the configuration of interface in
<intended> would be identical to the one in <system> shown
above.</t>
<t>And <operational> will show the system-provided loopback
interface, note that <operational> also includes the default
value specified in the YANG module:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:system">
<interface>
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces></artwork>
</figure>
</section>
<section title="Client Commits Configuration">
<t>If a client creates an interface "et-0/0/0" but the interface does
not physically exist at this point, what is in <running> appears
as follows:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>And the contents of <system> keep unchanged since the
interface is not physically present:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>The contents of <intended> represent the merged data of
<system> and <running>:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>Since the interface named "et-0/0/0" does not exist, the associated
configuration is not present in <operational>, which appears as
follows:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces> </artwork>
</figure>
</section>
<section title="Operator Installs Card into a Chassis">
<t>When the interface is installed by the operator, the system will
detect it and generate the associated conditionally-present interface
configuration in <system>. The contents of <running> keep
unchanged:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>And <system> might appear as follows:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<description>system-defined interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>Then <intended> contains the merged configuration of
<system> and <running>:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces></artwork>
</figure>
<t>And the contents of <operational> appear as follows:</t>
<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type or:origin="or:system">ethernet</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces> </artwork>
</figure>
</section>
<section title="Client further Commits Configuration">
<t>If the client further sets the speed of interface "et-0/0/0" in
<running> using a "merge" operation:<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<speed>10Mb</speed>
</interface>
</interfaces> </artwork>
</figure></t>
<t>The contents of <system> keep unchanged:<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<description>system-defined interface</description>
</interface>
</interfaces> </artwork>
</figure></t>
<t>And the contents of <intended> which represents a merged
results of <running> and <system> are as follows:<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<ip-address>192.168.10.10</ip-address>
<speed>10Mb</speed>
<description>pre-provisioned interface</description>
</interface>
</interfaces> </artwork>
</figure></t>
<t>And <operational> would appear as follows:<figure>
<artwork><interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">