Internet DRAFT - draft-ietf-netconf-privcand
draft-ietf-netconf-privcand
Internet Engineering Task Force JG. Cumming
Internet-Draft Nokia
Intended status: Standards Track R. Wills
Expires: 2 September 2024 Cisco Systems
1 March 2024
NETCONF Private Candidates
draft-ietf-netconf-privcand-02
Abstract
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.
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Definitions and terminology . . . . . . . . . . . . . . . . . 3
2.1. Session specific datastore . . . . . . . . . . . . . . . 3
2.2. Shared candidate configuration . . . . . . . . . . . . . 4
2.3. Private candidate configuration . . . . . . . . . . . . . 4
3. Limitations using the shared candidate configuration for
multiple clients . . . . . . . . . . . . . . . . . . . . 4
3.1. Issues . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Unintended deployment of alternate users configuration
changes . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Current mitigation strategies . . . . . . . . . . . . . . 5
3.2.1. Locking the shared candidate configuration
datastore . . . . . . . . . . . . . . . . . . . . . . 5
3.2.2. Always use the running configuration datastore . . . 6
3.2.3. Fine-grained locking . . . . . . . . . . . . . . . . 6
4. Private candidates solution . . . . . . . . . . . . . . . . . 6
4.1. What is a private candidate . . . . . . . . . . . . . . . 7
4.2. When is a private candidate created . . . . . . . . . . . 7
4.3. When is a private candidate destroyed . . . . . . . . . . 7
4.4. How to signal the use of private candidates . . . . . . . 7
4.4.1. Server . . . . . . . . . . . . . . . . . . . . . . . 7
4.4.2. NETCONF client . . . . . . . . . . . . . . . . . . . 8
4.4.3. RESTCONF client . . . . . . . . . . . . . . . . . . . 9
4.5. Interaction between running and private-candidate(s) . . 10
4.6. Detecting and resolving conflicts . . . . . . . . . . . . 12
4.6.1. What is a conflict? . . . . . . . . . . . . . . . . . 12
4.6.2. Detecting and reporting conflicts . . . . . . . . . . 13
4.6.3. Conflict resolution . . . . . . . . . . . . . . . . . 14
4.6.4. Default resolution mode and advertisement of this
mode . . . . . . . . . . . . . . . . . . . . . . . . 21
4.6.5. Supported resolution modes . . . . . . . . . . . . . 21
4.7. NETCONF operations . . . . . . . . . . . . . . . . . . . 21
4.7.1. New NETCONF operations . . . . . . . . . . . . . . . 21
4.7.2. Updated NETCONF operations . . . . . . . . . . . . . 22
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.1. Normative References . . . . . . . . . . . . . . . . . . 25
7.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Behavior with unaltered NETCONF operations . . . . . 26
A.1. <get> . . . . . . . . . . . . . . . . . . . . . . . . . . 26
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Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
NETCONF [RFC6241] and RESTCONF [RFC8040] 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.
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.
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.
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.
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.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Definitions and terminology
2.1. Session specific datastore
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.
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2.2. Shared candidate configuration
The candidate configuration datastore defined in [RFC6241] is
referenced as the shared candidate configuration in this document.
2.3. Private candidate configuration
A private candidate configuration is a session specific candidate
configuration datastore.
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.
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.
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 [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.
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).
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.
3. Limitations using the shared candidate configuration for multiple
clients
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.
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3.1. Issues
3.1.1. Unintended deployment of alternate users configuration changes
Consider the following scenario:
1. Client 1 modifies item A in the shared candidate configuration
2. Client 2 then modifies item B in the shared candidate
configuration
3. Client 2 then issues a <commit> RPC
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.
3.2. Current mitigation strategies
3.2.1. Locking the shared candidate configuration datastore
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.
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.
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.
Finally, this locking mechanism isn't available to RESTCONF clients.
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3.2.2. Always use the running configuration datastore
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.
3.2.3. Fine-grained locking
[RFC5717] describes a partial lock mechanism that can be used on
specific portions of the shared candidate datastore.
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.
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.
4. Private candidates solution
The use of private candidates resolves the issues detailed earlier in
this document.
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.
Using this approach clients may improve their performance and reduce
the likelihood of blocking other clients from continuing with valid
operational activities.
One or more private candidates may exist at any one time, however, a
private candidate SHOULD:
* Be accessible by one client only
* Be visible by one client only
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.
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4.1. What is a private candidate
A private candidate is defined earlier in the definitions and
terminology section of this document.
4.2. When is a private candidate created
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>.
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.
+----------------------------> private candidate
/
/
+------+-------------------------------> running configuration
^
Private candidate created
4.3. When is a private candidate destroyed
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.
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).
4.4. How to signal the use of private candidates
4.4.1. Server
The server MUST signal its support for private candidates. The
server does this by advertising a new :private-candidate capability:
urn:ietf:params:netconf:capability:private-candidate:1.0
A server may also advertise the :candidate capability as defined in
[RFC6241] if the shared candidate is also supported.
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A non-NMDA capable NETCONF server that advertises the :private-
candidate capability MUST also advertise the :candidate capability.
If the server has not signalled the :private-candidate capability, or
otherwise does not support private candidates, the server MUST:
* Terminate the session when it receives the :private-candidate
capability from a client in a <hello> message,
* Return an <rpc-error> if a client attempts to interact with the
NMDA private-candidate configuration datastore.
4.4.2. NETCONF client
In order to utilise a private candidate configuration within a
NETCONF session, the client must inform the server that it wishes to
do this.
Two approaches are available for a NETCONF client to signal that it
wants to use a private candidate:
4.4.2.1. Client capability declaration
When a NETCONF client connects with a server it sends a list of
client capabilities including one of the :base NETCONF version
capabilties.
In order to enable private candidate mode for the duration of the
NETCONF client session the NETCONF client sends the following
capability:
urn:ietf:params:netconf:capability:private-candidate:1.0
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.
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.
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.
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Using this method, the use of private candidates can be made
available to NMDA and non-NMDA capable servers.
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>)
4.4.2.2. Private candidate datastore
The private candidate configuration datastore is exposed as its own
datastore similar to other NMDA [RFC8342] capable datastores. This
datastore is called private-candidate.
All NMDA operations that support candidate NMDA datastore SHOULD
support the private-candidate datastore.
Any non-NMDA aware NETCONF operations that take a source or target
(destination) may be extended to accept the new datastore.
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.
To use this method the client is not required to send the :private-
candidate capability.
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.
4.4.3. RESTCONF client
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
[RFC8527].
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4.4.3.1. Datastore is not explicitly referenced
When the server advertises the :private-candidate capability and the
client references the "{+restconf}/data" resource described in
Section 3.3.1 of [RFC8040], all edits are made to the client's
private candidate, and the private candidate is automatically
committed.
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.
4.4.3.2. Private candidate datastore is referenced in the request
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.
A commit request is of the form "{+restconf}/operations/ietf-
netconf:commit", using the API described in Section 3.3.2 of
[RFC8040]. The semantics are identical to the NETCONF <commit>
operation.
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.
4.4.3.3. Identifying the private candidate datastore
Each RESTCONF client has its own private candidate datastore. The
client (and hence the private candidate datastore) is identified
using the mechanism described in Section 2.5 of [RFC8040].
4.5. Interaction between running and private-candidate(s)
Multiple operations may be performed on the private candidate in
order to stage changes ready for a commit.
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 [RFC6241].
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commit
+--------------------------+--------> private candidate
/ ^ ^ \
/ edit-config edit-config ⌄
+---+-------------------------------+------> running configuration
^
edit-config
(Private candidate created)
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.
commit
+---------------------+----------------> private candidate 1
/ \
/ edit-config ⌄
+---+------------+-------------+--------------> running configuration
edit-config \
\
+-------------------------> private candidate 2
In this situation, if, how and when private candidate 2 is updated
with the information that the running configuration has changed must
be considered.
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.
It is possible, during an update, for conflicts to occur and the
detection and resolution of these is discussed later in this
document.
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.
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:
* The client requests that the private candidate be refreshed using
a new <update> operation
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* <commit> is issued (which MUST automatically issue an <update>
operation immediately prior to committing the configuration)
* An implmentation chooses to perform an <update> operation after a
change to the running configuration by any other client
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.
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
A <compare> operation may be performed against:
* The initial creation point of the private candidate's branch
* Against the last update point of the private candidate's branch
* Against the running configuration
4.6. Detecting and resolving conflicts
4.6.1. What is a conflict?
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).
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.
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.
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Examples of conflicts include:
* 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.
* 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.
4.6.2. Detecting and reporting conflicts
A conflict can occur when an <update> operation is triggered. This
can occur in a number of ways:
* Manually triggered by the <update> NETCONF operation
* 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.
When a conflict occurs:
* 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).
* 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).
* 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)
The location of the conflict(s) should be reported as a list of
xpaths and values.
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
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4.6.3. Conflict resolution
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.
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.
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.
The following configuration data is used below to illustrate the
behaviour of each resolution method:
<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>
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.
update commit
+--------------------+---+------> private candidate 1
/ / \
/ edit-config / ⌄
+---+--------+--------+--+--------+----> running configuration
edit-config \ ^
\ /
+---+------------------> private candidate 2
commit
There are three defined resolution methods:
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4.6.3.1. Ignore
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.
Example:
Session 1 edits the configuration by submitting the following
<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>
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.
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<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>
Session 1 then sends an <update> NETCONF operation.
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>ignore</resolution-mode>
</update>
</rpc>
The un-conflicting changes are merged and the conflicting ones are
ignored (and not merged from the running into private candidate 1).
The resulting data in private candidate 1 is:
<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>
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4.6.3.2. Overwrite
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.
Example:
Session 1 edits the configuration by submitting the following
<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>
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.
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<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>
Session 1 then sends an <update> NETCONF operation.
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>overwrite</resolution-mode>
</update>
</rpc>
The un-conflicting changes are merged and the conflicting ones are
pushed into the private candidate 1 overwriting the existing changes.
The resulting data in private candidate 1 is:
<configure>
<interfaces>
<interface>
<name>intf_two</name>
<description>Link moved to Paris<description>
</interface>
</interfaces>
</configure>
4.6.3.3. Revert-on-conflict
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.
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No changes, whether conflicting or un-conflicting are merged into the
private candidate configuration.
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.
This resolution method is the default resolution method as it
provides for the highest level of visibility and control to ensure
operational stability.
This resolution method MUST be supported by a server.
Example:
Session 1 edits the configuration by submitting the following
<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>
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.
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<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>
Session 1 then sends an <update> NETCONF operation.
<rpc message-id="update"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<update>
<resolution-mode>revert-on-conflict</resolution-mode>
</update>
</rpc>
A conflict is detected, the update fails with an <rpc-error> and no
merges/overwrite operations happen.
The resulting data in private candidate 1 is:
<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>
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4.6.4. Default resolution mode and advertisement of this mode
The default resolution mode is revert-on-conflict, however, a system
MAY choose to select a different default resolution mode.
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.
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:
urn:ietf:params:netconf:capability:private-candidate:1.0
?default-resolution-mode=overwrite
4.6.5. Supported resolution modes
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:
urn:ietf:params:netconf:capability:private-candidate:1.0
?supported-resolution-modes=revert-on-conflict,ignore
4.7. NETCONF operations
4.7.1. New NETCONF operations
4.7.1.1. <update>
The <update> operation is provided to allow NETCONF clients (or
servers) to trigger a rebase of the private candidate configuration
against the running configuration.
The <update> operation may be triggered manually by the client or
automatically by the server.
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.
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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.
4.7.1.1.1. <resolution-mode> parameter
The <update> operation takes the optional <resolution-mode> parameter
The resolution modes are described earlier in this document and the
accepted inputs are:
* revert-on-conflict (default)
* ignore
* overwrite
4.7.2. Updated NETCONF operations
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.
4.7.2.1. <edit-config>
The <edit-config> operation is updated to accept private-candidate as
valid input to the <target> field.
The use of <edit-config> will create a private candidate
configuration if one does not already exist for that NETCONF session.
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).
Multiple <edit-config> requests may be sent to the private-candidate
datastore in a single session.
4.7.2.2. <edit-data>
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).
The use of <edit-data> will create a private candidate configuration
if one does not already exist for that NETCONF session.
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Multiple <edit-data> requests may be sent to the private-candidate
datastore in a single session.
4.7.2.3. <lock> and <unlock>
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.
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.
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>.
Performing an <unlock> on the private-candidate datastore is a valid
operation
Changes in the private-candidate datastore are not lost when the lock
is released.
4.7.2.4. <compare>
Performing a <compare> [RFC9144] operation with the private-candidate
datastore as either the <source> or <target> is a valid operation.
If <compare> is performed prior to a private candidate configuration
being created, one will be created at that point.
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.
4.7.2.4.1. <reference-point> parameter
This document adds the optional <reference-point> node to the input
of the <compare> operation that accepts the following values:
* last-update
* creation-point
Servers MAY support this functionality but are not required to by
this document.
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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).
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.
4.7.2.5. <get-config>
The <get-config> operation is updated to accept private-candidate as
valid input to the <source> field.
The use of <get-config> will create a private candidate configuration
if one does not already exist for that NETCONF session.
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).
4.7.2.6. <get-data>
The <get-data> operation accepts the private-candidate as a valid
datastore.
The use of <get-data> will create a private candidate configuration
if one does not already exist for that NETCONF session.
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).
4.7.2.7. <copy-config>
The <copy-config> operation is updated to accept private-candidate as
a valid input to the <source> or <target> fields.
4.7.2.8. <delete-config>
The <delete-config> operation is updated to accept private-candidate
as a valid input to the <target> field.
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4.7.2.9. <commit>
The <commit> operation MUST trigger an implicit <update> operation.
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.
5. IANA Considerations
This document requests the registration the the following NETCONF
capabilities:
* urn:ietf:params:netconf:capability:private-candidate:1.0 (Version
1.0)
6. Security Considerations
This document should not affect the security of the Internet.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC9144] Clemm, A., Qu, Y., Tantsura, J., and A. Bierman,
"Comparison of Network Management Datastore Architecture
(NMDA) Datastores", RFC 9144, DOI 10.17487/RFC9144,
December 2021, <https://www.rfc-editor.org/info/rfc9144>.
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[RFC5717] Lengyel, B. and M. Bjorklund, "Partial Lock Remote
Procedure Call (RPC) for NETCONF", RFC 5717,
DOI 10.17487/RFC5717, December 2009,
<https://www.rfc-editor.org/info/rfc5717>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "RESTCONF Extensions to Support the Network
Management Datastore Architecture", RFC 8527,
DOI 10.17487/RFC8527, March 2019,
<https://www.rfc-editor.org/info/rfc8527>.
7.2. Informative References
Appendix A. Behavior with unaltered NETCONF operations
A.1. <get>
The <get> operation does not accept a datastore value and therefore
this document is not applicable to this operation. The use of the
get operation will not create a private candidate configuration.
Contributors
The authors would like to thank Jan Lindblad, Lori-Ann McGrath, Jason
Sterne, Kent Watsen and Rob Wilton for their contributions and
reviews.
Authors' Addresses
James Cumming
Nokia
Email: james.cumming@nokia.com
Robert Wills
Cisco Systems
Email: rowills@cisco.com
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