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draft-ietf-netconf-privcand-02.xml
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draft-ietf-netconf-privcand-02.xml
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<?xml version='1.0' encoding='utf-8'?>
<!--
draft-rfcxml-general-template-standard-01
This template includes examples of the most commonly used features of RFCXML with comments
explaining how to customise them. This template can be quickly turned into an I-D by editing
the examples provided. Look for [REPLACE], [REPLACE/DELETE], [CHECK] and edit accordingly.
Note - 'DELETE' means delete the element or attribute, not just the contents.
Documentation is at https://authors.ietf.org/en/templates-and-schemas
-->
<?xml-model href="rfc7991bis.rnc"?>
<!-- Required for schema validation and schema-aware editing -->
<!-- <?xml-stylesheet type="text/xsl" href="rfc2629.xslt" ?> -->
<!-- This third-party XSLT can be enabled for direct transformations in XML processors, including most browsers -->
<!DOCTYPE rfc [
<!ENTITY nbsp " ">
<!ENTITY zwsp "​">
<!ENTITY nbhy "‑">
<!ENTITY wj "⁠">
]>
<!-- If further character entities are required then they should be added to the DOCTYPE above.
Use of an external entity file is not recommended. -->
<rfc xmlns:xi="http://www.w3.org/2001/XInclude"
category="std"
docName="draft-ietf-netconf-privcand-02"
ipr="trust200902"
obsoletes=""
updates=""
submissionType="IETF"
xml:lang="en"
version="3"
consensus="true">
<front>
<title abbrev="NETCONF Private Candidates">NETCONF Private Candidates</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-netconf-privcand-02"/>
<author fullname="James Cumming" initials="JG" surname="Cumming">
<organization>Nokia</organization>
<address>
<email>[email protected]</email>
</address>
</author>
<author fullname="Robert Wills" initials="R" surname="Wills">
<organization>Cisco Systems</organization>
<address>
<email>[email protected]</email>
</address>
</author>
<date year="2024" month="03" day="01"/>
<!-- On draft subbmission:
* If only the current year is specified, the current day and month will be used.
* If the month and year are both specified and are the current ones, the current day will
be used
* If the year is not the current one, it is necessary to specify at least a month and day="1" will be used.
-->
<area>General</area>
<workgroup>Internet Engineering Task Force</workgroup>
<!-- "Internet Engineering Task Force" is fine for individual submissions. If this element is
not present, the default is "Network Working Group", which is used by the RFC Editor as
a nod to the history of the RFC Series. -->
<keyword>NETCONF</keyword>
<abstract>
<t>This document provides a mechanism to extend the Network Configuration Protocol
(NETCONF) and RESTCONF protocol to support multiple clients making configuration changes simultaneously and
ensuring that they commit only those changes that they defined.</t>
<t>This document addresses two specific aspects: The interaction with a private candidate
over the NETCONF and RESTCONF protocols and the methods to identify and resolve conflicts between
clients.</t>
</abstract>
</front>
<middle>
<section>
<name>Introduction</name>
<t><xref target="RFC6241">NETCONF</xref> and <xref target="RFC8040">RESTCONF</xref>
both provide a mechanism for one or more
clients to make configuration changes to a device running as a NETCONF/RESTCONF
server. Each client has the ability to make one or more
configuration change to the servers shared candidate configuration.<br/><br/>
As the name shared candidate suggests, all clients have access to the same candidate
configuration. This means that multiple clients may make changes to the shared
candidate prior to the configuration being committed. This behavior may be
undesirable as one client may unwittingly commit the configuration changes made
by another client. <br/><br/>
NETCONF provides a way to mitigate this behavior by allowing clients
to place a lock on the shared candidate. The placing of this lock means that
no other client may make any changes until that lock is released. This behavior
is, in many situations, also undesirable. <br/><br/>
Many network devices already support private candidates configurations,
where a user (machine or otherwise) is able to edit a personal copy of a devices
configuration without blocking other users from doing so.<br/><br/>
This document details the extensions to the NETCONF protocol in order to support
the use of private candidates. It also describes how the RESTCONF protocol can be
used on a system that implements private candidates.</t>
<section>
<name>Requirements Language</name>
<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>
<section>
<name>Definitions and terminology</name>
<section>
<name>Session specific datastore</name>
<t>A session specific datastore is a configuration datastore that,
unlike the candidate and running configuration datastores which
have only one per system, is bound to the specific NETCONF session.
</t>
</section>
<section>
<name>Shared candidate configuration</name>
<t>The candidate configuration datastore defined in
<xref target="RFC6241"/> is referenced as the shared candidate
configuration in this document.</t>
</section>
<section>
<name>Private candidate configuration</name>
<t>A private candidate configuration is a session specific candidate
configuration datastore.</t>
<t>When a private candidate is used by NETCONF, the specific session
(and user) that created the private
candidate configuration is the only session (user) that has access
to it over NETCONF. Devices may expose this to other users through
other interfaces but this is out of scope for this document.</t>
<t>When a private candidate is used by RESTCONF, the client that created
the private candidate configuration is the only client that has access
to it over RESTCONF.</t>
<t>The private candidate configuration contains a full copy of the running
configuration when it is created (in the same way as a branch does in
a source control management system and in the same way as the candidate
configuration datastore as defined in <xref target="RFC6241"/>).
Any changes made to it, for example, through the use of operations such
as <edit-config> and <edit-data>, are made in this private
candidate configuration.</t>
<t>Obtaining this private candidate over NETCONF or RESTCONF will display the entire
configuration, including all changes made to it. Performing a <commit>
operation will merge the changes from the private candidate into the
running configuration (the same as a merge in source code management systems).
A <discard-changes> operation will revert the private candidate to the
branch's initial state or it's state at the last <commit> (whichever
is most recent).</t>
<t>All changes made to this private candidate configuration are held
separately from any other candidate configuration changes, whether
made by other users to the shared candidate or any other private candidate,
and are not visible to or accessible by anyone else.</t>
</section>
</section>
<section>
<name>Limitations using the shared candidate configuration for multiple clients</name>
<t>The following sections describe some limitations and mitigation factors in
more detail for the use of the shared candidate configuration during multi-client
configuration over NETCONF or RESTCONF.</t>
<section>
<name>Issues</name>
<section>
<name>Unintended deployment of alternate users configuration changes</name>
<t>Consider the following scenario:</t>
<ol>
<li>Client 1 modifies item A in the shared candidate configuration</li>
<li>Client 2 then modifies item B in the shared candidate configuration</li>
<li>Client 2 then issues a <commit> RPC</li>
</ol>
<t>In this situation, both client 1 and client 2 configurations will be committed by
client 2. In a machine-to-machine environment client 2 may not have been aware of
the change to item A and, if they had been aware, may have decided not to proceed.
</t>
</section>
</section>
<section>
<name>Current mitigation strategies</name>
<section>
<name>Locking the shared candidate configuration datastore</name>
<t>
In order to resolve unintended deployment of alternate users configuration changes
as described above NETCONF provides the ability to lock a datastore in order to
restrict other users from editing and committed changes.
</t>
<t>This does resolve the specific issue above, however, it introduces another issue.
Whilst one of the clients holds a lock, no other client may edit the configuration.
This will result in the client failing and having to retry. Whilst this may be a
desirable consequence when two clients are editing the same section of the configuration,
where they are editing different sections this behavior may hold up valid operational
activity.</t>
<t>Additionally, a lock placed on the shared candidate configuration must also lock the
running configuration, otherwise changes committed directly into the running datastore
may conflict.</t>
<t>Finally, this locking mechanism isn't available to RESTCONF clients.</t>
</section>
<section>
<name>Always use the running configuration datastore</name>
<t>The use of the running configuration datastore as the target for all configuration
changes does not resolve any issues regarding blocking of system access in the case a
lock is taken, nor does it provide a solution for multiple NETCONF and RESTCONF clients as each
configuration change is applied immediately and the client has no knowledge of the
current configuration at the point in time that they commenced the editing activity nor
at the point they commit the activity.</t>
</section>
<section>
<name>Fine-grained locking</name>
<t><xref target="RFC5717"/> describes a partial lock mechanism that
can be used on specific portions of the shared candidate datastore.</t>
<t>Partial locking does not solve the issues of staging a set of
configuration changes such that only those changes get committed in a
commit operation, nor does it solve the issue of multiple clients
editing the same parts of the configuration at the same time.</t>
<t>Partial locking additionally requires that the client is aware of
any interdependencies within the servers YANG models in order to lock all
parts of the tree.</t>
</section>
</section>
</section>
<section>
<name>Private candidates solution</name>
<t>The use of private candidates resolves the issues
detailed earlier in this document.</t>
<t>NETCONF sessions and RESTCONF clients are able to utilize the concept of private candidates
in order to streamline network operations, particularly for
machine-to-machine communication.</t>
<t>Using this approach clients may improve their performance and reduce the
likelihood of blocking other clients from continuing with valid operational
activities.</t>
<t>One or more private candidates may exist at any one time, however, a
private candidate SHOULD:</t>
<ul>
<li>Be accessible by one client only</li>
<li>Be visible by one client only</li>
</ul>
<t>Additionally, the choice of using a shared candidate configuration
datastore or a private candidate configuration datastore MUST be for
the entire duration of the NETCONF session.</t>
<section>
<name>What is a private candidate</name>
<t>A private candidate is defined earlier in the definitions and terminology
section of this document.</t>
</section>
<section>
<name>When is a private candidate created</name>
<t>A private candidate datastore is created when the first RPC that requires access
to it is sent to the server. This could be, for example, an <edit-config>.</t>
<t>When the private candidate is created a copy of the running configuration is
made and stored in it. This can be considered the same as creating a branch in a
source code repository.</t>
<artwork>
+----------------------------> private candidate
/
/
+------+-------------------------------> running configuration
^
Private candidate created
</artwork>
</section>
<section>
<name>When is a private candidate destroyed</name>
<t>A private candidate is valid for the duration of the NETCONF session,
or the duration of the existence of the RESTCONF client. Issuing
a <commit> operation will not close the private candidate but will issue an
implicit <update> operation resyncing changes from the running configuration.
More details on this later in this document.</t>
<t>A NETCONF session that is operating using a private candidate will
discard all uncommitted changes in that session's private candidate and destroy
the private candidate if the session is closed through a deliberate user action or
disconnected for any other reason (such as a loss of network connectivity).</t>
</section>
<section>
<name>How to signal the use of private candidates</name>
<section>
<name>Server</name>
<t>The server MUST signal its support for private candidates. The server
does this by advertising a new :private-candidate capability:</t>
<sourcecode>
urn:ietf:params:netconf:capability:private-candidate:1.0
</sourcecode>
<t>A server may also advertise the :candidate capability as defined in
<xref target="RFC6241"/> if the shared candidate is also supported.</t>
<t>A non-NMDA capable NETCONF server that advertises the :private-candidate
capability MUST also advertise the :candidate capability.</t>
<t>If the server has not signalled the :private-candidate capability,
or otherwise does not support private candidates, the server MUST:</t>
<ul>
<li>Terminate the session when it receives the :private-candidate
capability from a client in a <hello> message,</li>
<li>Return an <rpc-error> if a client attempts to interact with the
NMDA private-candidate configuration datastore.</li>
</ul>
</section>
<section>
<name>NETCONF client</name>
<t>In order to utilise a private candidate configuration within a NETCONF
session, the client must inform the server that it wishes to do this.</t>
<t>Two approaches are available for a NETCONF client to signal that it wants
to use a private candidate:</t>
<section>
<name>Client capability declaration</name>
<t>When a NETCONF client connects with a server it sends a list of client
capabilities including one of the :base NETCONF version capabilties.</t>
<t>In order to enable private candidate mode for the duration of the NETCONF
client session the NETCONF client sends the following capability:</t>
<sourcecode>
urn:ietf:params:netconf:capability:private-candidate:1.0
</sourcecode>
<t>In order for the use of private candidates to be established using this
approach both the NETCONF server and the NETCONF client MUST advertise
this capability.</t>
<t>When a server receives the client capability its mode of operation
will be set to private candidate mode for the duration of the NETCONF
session.</t>
<t>All RPC requests that target the candidate configuration datastore
will operate in exactly the same way as they would do when using the
shared candidate configuration datastore, however, when the server
receives a request to act upon the candidate configuration datastore it
instead uses the session's private candidate configuration datastore.</t>
<t>Using this method, the use of private candidates can be made available
to NMDA and non-NMDA capable servers.</t>
<t>No protocol extensions are required for the transitioning of candidates between
the shared mode and the private mode and no extensions are required for any
RPCs (including <lock>)</t>
</section>
<section>
<name>Private candidate datastore</name>
<t>The private candidate configuration datastore is exposed as its
own datastore similar to other <xref target="RFC8342">NMDA</xref>
capable datastores. This datastore is called private-candidate.</t>
<t>All NMDA operations that support candidate NMDA datastore SHOULD
support the private-candidate datastore.</t>
<t>Any non-NMDA aware NETCONF operations that take a source or target
(destination) may be extended to accept the new datastore.</t>
<t>The ability for the server to support private candidates is optional
and SHOULD be signalled in NMDA supporting servers as a datastore in addition
to the server capabilities described earlier in this document.</t>
<t>To use this method the client is not required to send the
:private-candidate capability.</t>
<t>The first datastore referenced (either candidate or private-candidate) in
any NETCONF operation will define which mode that NETCONF session will
operate in for its duration. As an example, performing a <get-data>
operation on the private-candidate datastore will switch the session into
private candidate configuration mode and subsequent <edit-config>
operations that reference the candidate configuration datastore MUST fail.</t>
</section>
</section>
<section>
<name>RESTCONF client</name>
<t>RESTCONF doesn't provide a mechanism for the client to advertise a capability.
Therefore when a RESTCONF server advertises the :private-candidate capability, the
decision of whether to use a private candidate depends on whether a datastore is
explicitly referenced in the request using the RESTCONF extensions for NMDA
<xref target="RFC8527"/>.</t>
<section>
<name>Datastore is not explicitly referenced</name>
<t>When the server advertises the :private-candidate capability and the client
references the "{+restconf}/data" resource described in
<xref target="RFC8040" sectionFormat="of" section="3.3.1" />,
all edits are made to the client's private candidate, and the private candidate
is automatically committed.</t>
<t>This ensures backwards compatibility with RESTCONF clients that are not aware of
private candidates, because those clients will expect their changes to be
committed immediately.</t>
</section>
<section>
<name>Private candidate datastore is referenced in the request</name>
<t>When the private-candidate datastore is explicitly referenced as an NMDA datastore,
edits are made to the client's private candidate, but the private candidate is not
committed. To commit the changes, the client must explicitly send a commit request.</t>
<t>A commit request is of the form "{+restconf}/operations/ietf-netconf:commit",
using the API described in <xref target="RFC8040" sectionFormat="of" section="3.3.2" />.
The semantics are identical to the NETCONF <commit> operation.</t>
<t>Similarly, the client can perform ietf-netconf:discard-changes,
ietf-netconf:validate, and ietf-netconf:cancel-commit operations (if the appropriate
capabilities are implemented). The semantics are identical to NETCONF.</t>
</section>
<section>
<name>Identifying the private candidate datastore</name>
<t>Each RESTCONF client has its own private candidate datastore. The client
(and hence the private candidate datastore) is identified using the mechanism
described in <xref target="RFC8040" sectionFormat="of" section="2.5" />.</t>
</section>
</section>
</section>
<section>
<name>Interaction between running and private-candidate(s)</name>
<t>Multiple operations may be performed on the private candidate in order
to stage changes ready for a commit.</t>
<t>In the simplest example, a session may create a private candidate configuration,
perform multiple operations (such as <edit-config>) on it and then
perform a <commit> operation to merge the private candidate configuration
into the running configuration in line with semantics in <xref target="RFC6241"/>.
</t>
<artwork>
commit
+--------------------------+--------> private candidate
/ ^ ^ \
/ edit-config edit-config ⌄
+---+-------------------------------+------> running configuration
^
edit-config
(Private candidate created)
</artwork>
<t>More complex scenarios need to be considered, when multiple private candidate
sessions are working on their own configuration (branches) and they make commits
into the running configuration.</t>
<artwork>
commit
+---------------------+----------------> private candidate 1
/ \
/ edit-config ⌄
+---+------------+-------------+--------------> running configuration
edit-config \
\
+-------------------------> private candidate 2
</artwork>
<t>In this situation, if, how and when private candidate 2 is updated with the
information that the running configuration has changed must be considered.</t>
<t>As described earlier, the client MUST be aware of changes to it's private candidate
configuration so it can be assured that it is only committing its own modifications.
It should also be aware of any changes to the current running configuration.</t>
<t>It is possible, during an update, for conflicts to occur and the detection and
resolution of these is discussed later in this document.</t>
<t>A good way to understand the interaction between candidates is to consider them as
branches such as you might find in a source code management system.</t>
<t>Each private candidate is treated as a separate branch and changes made to the
running configuration are not placed into a private candidate datastore except in one
of the following situations:</t>
<ul>
<li>The client requests that the private candidate be refreshed using a new <update>
operation</li>
<li><commit> is issued (which MUST automatically issue an <update> operation
immediately prior to committing the configuration)</li>
<li>An implmentation chooses to perform an <update> operation after a change to
the running configuration by any other client</li>
</ul>
<t>It is possible for a private candidate configuration to become significantly out of
sync with the running configuration should the private candidate be open for a long time,
however, most NETCONF configuration activities (between the first
<edit-config>/<edit-data> and a <commit>) are short-lived.</t>
<t>An implementation may choose, optionally, to automatically perform an <update>
operation after a change to the running configuration from another client. However, this
choice should be made with caution as it will replace, overwrite, or otherwise alter
(depending on the servers default resolution mode, discussed later) the private candidate
configuration without notifying the client</t>
<t>A <compare> operation may be performed against:</t>
<ul>
<li>The initial creation point of the private candidate's branch</li>
<li>Against the last update point of the private candidate's branch</li>
<li>Against the running configuration</li>
</ul>
</section>
<section>
<name>Detecting and resolving conflicts</name>
<section>
<name>What is a conflict?</name>
<t>A conflict is when the intent of the client may have
been different had it had a different starting point. In configuration
terms, a conflict occurs when the same set of nodes in a configuration being
altered by one user are changed between the start of the configuration
preparation (the first <edit-config>/<edit-data> operation)
and the conclusion of this configuration session (terminated by a
<commit> operation).</t>
<t>The situation where conflicts have the potential of occurring are when
multiple configuration sessions are in progress and one session commits
changes into the running configuration after the private candidate
(branch) was created. </t>
<t>When this happens a conflict occurs if the nodes modified in the running
configuration are the same nodes that are modified in the private candidate
configuration.</t>
<t>Examples of conflicts include:</t>
<ul>
<li>An interface has been deleted in the running configuration that existed
when the private candidate was created. A change to a child node of this specific
interface is made in the private candidate using the default merge operation
would, instead of changing the child node, both recreate the interface and then
set the child node.</li>
<li>A leaf has been modified in the running configuration from the value that
it had when the private candidate was created. The private candidate configuration
changes that leaf to another value.</li>
</ul>
</section>
<section>
<name>Detecting and reporting conflicts</name>
<t>A conflict can occur when an <update> operation is triggered. This
can occur in a number of ways:</t>
<ul>
<li>Manually triggered by the <update> NETCONF operation</li>
<li>Automatically triggered by the server running an <update>
operation, such as when a <commit> operation is performed by the
client in the private candidate session.</li>
</ul>
<t>When a conflict occurs:</t>
<ul>
<li>The client MUST be given the opportunity to re-evaluate its intent based
on the new information. The resolution of the conflict may be manual or
automatic depending on the server and client decision (discussed later in
this document).</li>
<li>A <commit> operation (that MUST trigger an automatic <update>
operation immediately before) MUST fail. It MUST inform the client of the
conflict and SHOULD detail the location of the conflict(s).</li>
<li>A <update> operation MUST fail unless the server has explicitly
configured a system-wide default resolution mode of ignore or overwrite
(discussed later in this document)</li>
</ul>
<t>The location of the conflict(s) should be reported as a list of
xpaths and values.</t>
<t>Note: If a server implementation has chosen to automatically issue an
<update> operation every time a change is made to the running configuration
the server MUST have the system-wide default resolution mode set to ignore or
overwrite</t>
</section>
<section>
<name>Conflict resolution</name>
<t>Conflict resolution defines which configuration elements are retained
when a conflict is resolved; those from the running configuration or
those from the private candidate configuration.</t>
<t>When a conflict is detected in any client triggered activity, the client
MUST be informed. The client then has a number of options available to
resolve the conflict.</t>
<t>An <update> operation uses the resolution method specified in the
request, or the system default resolution mode if not specified. The <update>
operation is discussed later in this document.</t>
<t>The following configuration data is used below to illustrate the behaviour
of each resolution method:</t>
<sourcecode type="xml">
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to London<description>
</interface>
<interface>
<name>intf_two</name>
<description>Link to Tokyo<description>
</interface>
</interfaces>
</configure>
</sourcecode>
<t>The example workflow is shown in this diagram and is used for the purpose
of the examples below. In these examples the reader should assume that the
<update> operation is manually provided by a client working in
pruvate candidate 1.</t>
<artwork>
update commit
+--------------------+---+------> private candidate 1
/ / \
/ edit-config / ⌄
+---+--------+--------+--+--------+----> running configuration
edit-config \ ^
\ /
+---+------------------> private candidate 2
commit
</artwork>
<t>There are three defined resolution methods:</t>
<section>
<name>Ignore</name>
<t>When using the ignore resolution method items in the running
configuration that are not in conflict with the private candidate
configuration are merged from the running configuration
into the private candidate configuration. Nodes that are in conflict
are ignored and not merged. The outcome of this is that the private
candidate configuration reflects changes in the running that were not
being worked on and those that are being worked on in the private
candidate remain in the private candidate. Issuing a <commit>
operation at this point will overwrite the running configuration with
the conflicted items from the private candidate configuration.</t>
<t>Example:</t>
<t>Session 1 edits the configuration by submitting the following</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to San Francisco<description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 2 then edits the configuration deleting the
interface intf_one, updating the description on interface
intf_two and commits the configuration to the running
configuration datastore.</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name operation="delete">intf_one</name>
</interface>
<interface>
<name>intf_two</name>
<description>Link moved to Paris</description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 1 then sends an <update> NETCONF operation.</t>
<sourcecode type="xml">
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>ignore</resolution-mode>
</update>
</rpc>
</sourcecode>
<t>The un-conflicting changes are merged and the conflicting
ones are ignored (and not merged from the running into
private candidate 1).</t>
<t>The resulting data in private candidate 1 is:</t>
<sourcecode type="xml">
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to San Francisco<description>
</interface>
<interface>
<name>intf_two</name>
<description>Link moved to Paris<description>
</interface>
</interfaces>
</configure>
</sourcecode>
</section>
<section>
<name>Overwrite</name>
<t>When using the overwrite resolution method items in the running
configuration that are not in conflict with the private candidate
configuration are merged from the running configuration into the
private candidate configuration. Nodes that are in conflict are
pushed from the running configuration into the private candidate
configuration, overwriting any previous changes in the private
candidate configuration. The outcome of this is that the private
candidate configuration reflects the changes in the running
configuration that were not being worked on as well as changing
those being worked on in the private candidate to new values.</t>
<t>Example:</t>
<t>Session 1 edits the configuration by submitting the following</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to San Francisco<description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 2 then edits the configuration deleting the
interface intf_one, updating the description on interface
intf_two and commits the configuration to the running
configuration datastore.</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name operation="delete">intf_one</name>
</interface>
<interface>
<name>intf_two</name>
<description>Link moved to Paris</description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 1 then sends an <update> NETCONF operation.</t>
<sourcecode type="xml">
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>overwrite</resolution-mode>
</update>
</rpc>
</sourcecode>
<t>The un-conflicting changes are merged and the conflicting
ones are pushed into the private candidate 1 overwriting the
existing changes.</t>
<t>The resulting data in private candidate 1 is:</t>
<sourcecode type="xml">
<configure>
<interfaces>
<interface>
<name>intf_two</name>
<description>Link moved to Paris<description>
</interface>
</interfaces>
</configure>
</sourcecode>
</section>
<section>
<name>Revert-on-conflict</name>
<t>When using the revert-on-conflict resolution method an update
will fail to complete when any conflicting node is found. The
session issuing the update will be informed of the failure.</t>
<t>No changes, whether conflicting or un-conflicting are merged into
the private candidate configuration.</t>
<t>The owner of the private candidate session must then take deliberate
and specific action to adjust the private candidate configuration to
rectify the conflict. This may be by issuing further <edit-config>
or <edit-data> operations, by issuing a <discard-changes>
operation or by issuing an <update> operation with a
different resolution method.</t>
<t>This resolution method is the default resolution method as it
provides for the highest level of visibility and control to ensure
operational stability.</t>
<t>This resolution method MUST be supported by a server.</t>
<t>Example:</t>
<t>Session 1 edits the configuration by submitting the following</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to San Francisco<description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 2 then edits the configuration deleting the
interface intf_one, updating the description on interface
intf_two and commits the configuration to the running
configuration datastore.</t>
<sourcecode type="xml">
<rpc message-id="config"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<edit-config>
<target><candidate/><target>
<config>
<configure>
<interfaces>
<interface>
<name operation="delete">intf_one</name>
</interface>
<interface>
<name>intf_two</name>
<description>Link moved to Paris</description>
</interface>
</interfaces>
</configure>
</config>
</edit-config>
</rpc>
</sourcecode>
<t>Session 1 then sends an <update> NETCONF operation.</t>
<sourcecode type="xml">
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>revert-on-conflict</resolution-mode>
</update>
</rpc>
</sourcecode>
<t>A conflict is detected, the update fails with an <rpc-error>
and no merges/overwrite operations happen.</t>
<t>The resulting data in private candidate 1 is:</t>
<sourcecode type="xml">
<configure>
<interfaces>
<interface>
<name>intf_one</name>
<description>Link to San Francisco<description>
</interface>
<interface>
<name>intf_two</name>
<description>Link to Tokyo<description>
</interface>
</interfaces>
</configure>
</sourcecode>
</section>
</section>
<section>
<name>Default resolution mode and advertisement of this mode</name>
<t>The default resolution mode is revert-on-conflict, however, a system MAY
choose to select a different default resolution mode.</t>
<t>The default resolution mode MUST be advertised in the :private-candidate
capability by adding the default-resolution-mode parameter if the system default
is anything other than revert-on-conflict. If the system default resolution
mode is revert-on-conflict then advertising this in the :private-candidate
capability is optional.</t>
<t>In this example, a server has configured a default system-wide resolution mode
of overwrite which MUST be signalled with the :private-candidate capability as
follows:</t>
<sourcecode>
urn:ietf:params:netconf:capability:private-candidate:1.0
?default-resolution-mode=overwrite
</sourcecode>
</section>
<section>
<name>Supported resolution modes</name>
<t>A server SHOULD support all three resolution modes, however, if the server
does not support all three modes, the server MUST report the supported modes
in the :private-candidate capability using the supported-resolution-modes,
for example:</t>
<sourcecode>
urn:ietf:params:netconf:capability:private-candidate:1.0
?supported-resolution-modes=revert-on-conflict,ignore
</sourcecode>
</section>
</section>
<section>
<name>NETCONF operations</name>
<section>
<name>New NETCONF operations</name>
<section>
<name><update></name>
<t>The <update> operation is provided to allow NETCONF clients
(or servers) to trigger a rebase of the private candidate configuration
against the running configuration.</t>
<t>The <update> operation may be triggered manually by the
client or automatically by the server.</t>
<t>The <update> operation MUST be implicitly triggered by a specific
NETCONF session issuing a <commit> operation when using private
candidates. The actual order of operations in the server MUST be to issue
the implicit <update> operation first and then the <commit>
operation.</t>
<t>A <commit> operation that fails the implicit <update> operation
SHOULD fail. The client is then required to make a specific decision to rectify
the issue prior to committing. This may be to edit the private candidate
configuration or to issue a manual <update> operation with a specific
resolution mode selected.</t>
<section>
<name><resolution-mode> parameter</name>
<t>The <update> operation takes the optional
<resolution-mode> parameter</t>
<t>The resolution modes are described earlier in this document
and the accepted inputs are:</t>
<ul>
<li>revert-on-conflict (default)</li>
<li>ignore</li>
<li>overwrite</li>
</ul>
</section>
</section>
</section>
<section>
<name>Updated NETCONF operations</name>
<t>Specific NETCONF operations altered by this document are listed in this section.
Any notable behavior with existing unaltered NETCONF operations is noted in the
appendix.</t>
<section>
<name><edit-config></name>
<t>The <edit-config> operation is updated to accept
private-candidate as valid input to the <target> field.</t>
<t>The use of <edit-config> will create a private candidate
configuration if one does not already exist for that NETCONF
session.</t>
<t>Sending an <edit-config> request to private-candidate
after one has been sent to the shared candidate datastore
in the same session will fail (and visa-versa).</t>
<t>Multiple <edit-config> requests may be sent to the
private-candidate datastore in a single session.</t>
</section>
<section>
<name><edit-data></name>
<t>The <edit-data> operation is updated to accept
private-candidate as valid input to the <datastore> field.
(datastore is an identityref and so the actual input will be
ds:private-candidate).</t>
<t>The use of <edit-data> will create a private candidate
configuration if one does not already exist for that NETCONF
session.</t>
<t>Multiple <edit-data> requests may be sent to the
private-candidate datastore in a single session.</t>
</section>
<section>
<name><lock> and <unlock></name>
<t>Performing a <lock> on the private-candidate datastore is a valid operation, although
it is understood that the practical effect of this is a 'no op' as only one session may edit
the locked private candidate.</t>
<t>If the client's intention is that no other session may commit changes to the system then
the client should issue a <lock> operation on the running candidate.</t>
<t>Other NETCONF sessions are still able to create a new private-candidate
configurations, make edits to them and perform operations on them, such as
<update> or <discard-changes>.</t>
<t>Performing an <unlock> on the private-candidate datastore is a valid operation</t>
<t>Changes in the private-candidate datastore are not lost when the lock is released.</t>
</section>
<section>
<name><compare></name>
<t>Performing a <xref target="RFC9144"><compare></xref> operation
with the private-candidate datastore as either the <source>
or <target> is a valid operation.</t>
<t>If <compare> is performed prior to a private candidate configuration
being created, one will be created at that point.</t>
<t>The <compare> operation is extended by this document to allow the ability to
compare the private-candidate datastore (at its current point in time) with the
same private-candidate datastore at an earlier point in time or with another datastore.</t>
<section>
<name><reference-point> parameter</name>
<t>This document adds the optional <reference-point> node to the input of
the <compare> operation that accepts the following values:</t>
<ul>
<li>last-update</li>
<li>creation-point</li>
</ul>
<t>Servers MAY support this functionality but are not required to by this document.</t>
<t>The last-update selection of <reference-point> will provide an output
comparing the current private-candidate configuration datastore with the same
private-candidate datastore at the time it was last updated using the <update>
NETCONF operation described in this document (whether automatically or manually triggered).</t>
<t>The creation-point selection of <reference-point> will provide an output
comparing the current private-candidate configuration datastore with the same
private-candidate datastore at the time this private-candidate was initially created.</t>
</section>
</section>
<section>
<name><get-config></name>
<t>The <get-config> operation is updated to accept private-candidate as
valid input to the <source> field.</t>
<t>The use of <get-config> will create a private candidate configuration
if one does not already exist for that NETCONF session.</t>
<t>Sending an <get-config> request to private-candidate
after one has been sent to the shared candidate datastore
in the same session will fail (and visa-versa).</t>
</section>
<section>
<name><get-data></name>
<t>The <get-data> operation accepts the private-candidate as a valid datastore.</t>
<t>The use of <get-data> will create a private candidate configuration
if one does not already exist for that NETCONF session.</t>
<t>Sending an <get-data> request to private-candidate
after one has been sent to the shared candidate datastore
in the same session will fail (and visa-versa).</t>
</section>
<section>
<name><copy-config></name>
<t>The <copy-config> operation is updated to accept private-candidate as
a valid input to the <source> or <target> fields.</t>
</section>
<section>
<name><delete-config></name>
<t>The <delete-config> operation is updated to accept private-candidate as
a valid input to the <target> field.</t>
</section>
<section>
<name><commit></name>
<t>The <commit> operation MUST trigger an implicit <update> operation.</t>
<t>Nothing in this document alters the standard behavior of the <persist> or
<persist-id> options and these SHOULD work when using the private-candidate
configuration datastore.</t>
</section>
</section>
</section>
</section>
<section anchor="IANA">
<!-- All drafts are required to have an IANA considerations section. See RFC 8126 for a guide.-->
<name>IANA Considerations</name>
<t>This document requests the registration the the following NETCONF capabilities:</t>
<ul><li>urn:ietf:params:netconf:capability:private-candidate:1.0 (Version 1.0)</li></ul>
</section>
<section anchor="Security">
<!-- All drafts are required to have a security considerations section. See RFC 3552 for a guide. -->
<name>Security Considerations</name>
<t>This document should not affect the security of the Internet.</t>
</section>
<!-- NOTE: The Acknowledgements and Contributors sections are at the end of this template -->
</middle>