Transaction ID Mechanism for NETCONF
draft-ietf-netconf-transaction-id-00
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Author | Jan Lindblad | ||
| Last updated | 2023-03-13 (Latest revision 2023-03-09) | ||
| Replaces | draft-lindblad-netconf-transaction-id | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Additional resources | Mailing list discussion | ||
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draft-ietf-netconf-transaction-id-00
NETCONF J. Lindblad
Internet-Draft Cisco Systems
Intended status: Standards Track 9 March 2023
Expires: 10 September 2023
Transaction ID Mechanism for NETCONF
draft-ietf-netconf-transaction-id-00
Abstract
NETCONF clients and servers often need to have a synchronized view of
the server's configuration data stores. The volume of configuration
data in a server may be very large, while data store changes
typically are small when observed at typical client resynchronization
intervals.
Rereading the entire data store and analyzing the response for
changes is an inefficient mechanism for synchronization. This
document specifies an extension to NETCONF that allows clients and
servers to keep synchronized with a much smaller data exchange and
without any need for servers to store information about the clients.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Network Configuration
Working Group mailing list (netconf@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/netconf/.
Source for this draft and an issue tracker can be found at
https://github.com/netconf-wg/transaction-id.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
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This Internet-Draft will expire on 10 September 2023.
Copyright Notice
Copyright (c) 2023 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
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
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. NETCONF Txid Extension . . . . . . . . . . . . . . . . . . . 4
3.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. General Txid Principles . . . . . . . . . . . . . . . . . 6
3.3. Initial Configuration Retrieval . . . . . . . . . . . . . 6
3.4. Subsequent Configuration Retrieval . . . . . . . . . . . 7
3.5. Configuration Retrieval from the Candidate Datastore . . 10
3.6. Conditional Transactions . . . . . . . . . . . . . . . . 11
3.7. Transactions toward the Candidate Datastore . . . . . . . 13
3.8. Dependencies within Transactions . . . . . . . . . . . . 15
3.9. Other NETCONF Operations . . . . . . . . . . . . . . . . 18
3.10. YANG-Push Subscriptions . . . . . . . . . . . . . . . . . 18
4. Txid Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 19
4.1. The etag attribute txid mechanism . . . . . . . . . . . . 20
4.2. The last-modified attribute txid mechanism . . . . . . . 20
4.3. Common features to both etag and last-modified txid
mechanisms . . . . . . . . . . . . . . . . . . . . . . . 21
4.3.1. Candidate Datastore . . . . . . . . . . . . . . . . . 22
4.3.2. Namespaces and Attribute Placement . . . . . . . . . 23
5. Txid Mechanism Examples . . . . . . . . . . . . . . . . . . . 24
5.1. Initial Configuration Response . . . . . . . . . . . . . 24
5.1.1. With etag . . . . . . . . . . . . . . . . . . . . . . 24
5.1.2. With last-modified . . . . . . . . . . . . . . . . . 28
5.2. Configuration Response Pruning . . . . . . . . . . . . . 30
5.3. Configuration Change . . . . . . . . . . . . . . . . . . 34
5.4. Conditional Configuration Change . . . . . . . . . . . . 38
5.5. Reading from the Candidate Datastore . . . . . . . . . . 40
5.6. Commit . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.7. YANG-Push . . . . . . . . . . . . . . . . . . . . . . . . 43
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6. YANG Modules . . . . . . . . . . . . . . . . . . . . . . . . 45
6.1. Base module for txid in NETCONF . . . . . . . . . . . . . 45
6.2. Additional support for txid in YANG-Push . . . . . . . . 49
7. Security Considerations . . . . . . . . . . . . . . . . . . . 51
7.1. NACM Access Control . . . . . . . . . . . . . . . . . . . 51
7.1.1. Hash-based Txid Algorithms . . . . . . . . . . . . . 51
7.2. Unchanged Configuration . . . . . . . . . . . . . . . . . 52
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
9.1. Major changes in -03 since -02 . . . . . . . . . . . . . 53
9.2. Major changes in -02 since -01 . . . . . . . . . . . . . 53
9.3. Major changes in -01 since -00 . . . . . . . . . . . . . 54
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.1. Normative References . . . . . . . . . . . . . . . . . . 55
10.2. Informative References . . . . . . . . . . . . . . . . . 56
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 56
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 56
1. Introduction
When a NETCONF client wishes to initiate a new configuration
transaction with a NETCONF server, a frequently occurring use case is
for the client to find out if the configuration has changed since the
client last communicated with the server. Such changes could occur
for example if another NETCONF client has made changes, or another
system or operator made changes through other means than NETCONF.
One way of detecting a change for a client would be to retrieve the
entire configuration from the server, then compare the result with a
previously stored copy at the client side. This approach is not
popular with most NETCONF users, however, since it would often be
very expensive in terms of communications and computation cost.
Furthermore, even if the configuration is reported to be unchanged,
that will not guarantee that the configuration remains unchanged when
a client sends a subsequent change request, a few moments later.
In order to simplify the task of tracking changes, a NETCONF server
could implement a meta level transaction tag or timestamp for an
entire configuration datastore or YANG subtree, and offer clients a
way to read and compare this tag or timestamp. If the tag or
timestamp is unchanged, clients can avoid performing expensive
operations. Such tags and timestamps are referred to as a
transaction id (txid) in this document.
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Evidence of a transaction id feature being demanded by clients is
that several server implementors have built proprietary and mutually
incompatible mechanisms for obtaining a transaction id from a NETCONF
server.
RESTCONF, [RFC8040], defines a mechanism for detecting changes in
configuration subtrees based on Entity-Tags (ETags) and Last-Modified
txid values.
In conjunction with this, RESTCONF provides a way to make
configuration changes conditional on the server confiuguration being
untouched by others. This mechanism leverages [RFC7232] "Hypertext
Transfer Protocol (HTTP/1.1): Conditional Requests".
This document defines similar functionality for NETCONF, [RFC6241],
and ties this in with YANG-Push, [RFC8641].
2. Conventions and Definitions
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.
This document uses the terminology defined in [RFC6241], [RFC7950],
[RFC8040], and [RFC8641].
In addition, this document defines the following terms:
Versioned node A node in the instantiated YANG data tree for which
the server maintains a transaction id (txid) value.
3. NETCONF Txid Extension
This document describes a NETCONF extension which modifies the
behavior of get-config, get-data, edit-config, edit-data, discard-
changes, copy-config, delete-config and commit such that clients are
able to conditionally retrieve and update the configuration in a
NETCONF server.
For servers implementing YANG-Push, an extension for conveying txid
updates as part of subscription updates is also defined.
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Several low level mechanisms could be defined to fulfill the
requirements for efficient client-server txid synchronization. This
document defines two such mechanisms, the etag txid mechanism and the
last-modified txid mechanism. Additional mechanisms could be added
in future.
3.1. Use Cases
The common use cases for such mecahnisms are briefly discussed here.
Initial configuration retrieval When the client initially connects
to a server, it may be interested to acquire a current view of
(parts of) the server's configuration. In order to be able to
efficiently detect changes later, it may also be interested to
store meta level txid information for subtrees of the
configuration.
Subsequent configuration retrieval When a client needs to reread
(parts of) the server's configuration, it may be interested to
leverage the txid meta data it has stored by requesting the server
to prune the response so that it does not repeat configuration
data that the client is already aware of.
Configuration update with txid return When a client issues a
transaction towards a server, it may be interested to also learn
the new txid meta data the server has stored for the updated parts
of the configuration.
Conditional configuration change When a client issues a transaction
towards a server, it may specify txid meta data for the
transaction in order to allow the server to verify that the client
is up to date with any changes in the parts of the configuration
that it is concerned with. If the txid meta data in the server is
different than the client expected, the server rejects the
transaction with a specific error message.
Subscribe to configuration changes with txid return When a client
subscribes to configuration change updates through YANG-Push, it
may be interested to also learn the the updated txid meta data for
the changed data trees.
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3.2. General Txid Principles
All servers implementing a txid mechanism MUST maintain a txid meta
data value for each configuration datastore supported by the server.
Txid mechanism implementations MAY also maintain txid meta data
values for nodes deeper in the YANG data tree. The nodes for which
the server maintains txids are collectively referred to as the
"versioned nodes".
The server returning txid values for the versioned nodes MUST ensure
the txid values are changed every time there has been a configuration
change at or below the node associated with the txid value. This
means any update of a config true node will result in a new txid
value for all ancestor versioned nodes, up to and including the
datastore root itself.
This also means a server MUST update the txid value for any nodes
that change as a result of a configuration change, regardless of
source, even if the changed nodes are not explicitly part of the
change payload. An example of this is dependent data under YANG
[RFC7950] when- or choice-statements.
The server MUST NOT change the txid value of a versioned node unless
the node itself or a child node of that node has been changed. The
server MUST NOT change any txid values due to changes in config false
data.
3.3. Initial Configuration Retrieval
When a NETCONF server receives a get-config or get-data request
containing requests for txid values, it MUST return txid values for
all versioned nodes below the point requested by the client in the
reply.
The exact encoding varies by mechanism, but all txid mechanisms would
have a special "txid-request" txid value (e.g. "?") which is
guaranteed to never be used as a normal txid value. Clients MAY use
this special txid value associated with one or more nodes in the data
tree to indicate to the server that they are interested in txid
values below that point of the data tree.
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Client Server
| |
| ------------------------------------------> |
| get-config (txid: ?) |
| acls |
| |
| <------------------------------------------ |
| data (txid: 5152) |
| acls (txid: 5152) |
| acl A1 (txid: 4711) |
| aces (txid: 4711) |
| ace R1 (txid: 4711) |
| matches ipv4 protocol udp |
| acl A2 (txid: 5152) |
| aces (txid: 5152) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp AF11 |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| ace R9 (txid: 5152) |
| matches tcp source-port port 22 |
v v
Figure 1: Initial Configuration Retrieval. The server returns
the requested configuration, annotated with txid values. The
most recent change seems to have been an update to the R8 and R9
source-port.
NOTE: In the call flow examples we are using a 4-digit, monotonously
increasing integer as txid. This is convenient and enhances
readability of the examples, but does not reflect a typical
implementation. Servers may assign values randomly. In general, no
information can be derived by observing that some txid value is
numerically or lexicographically lower than another txid value. The
only operation defined on a pair of txid values is testing them for
equality.
3.4. Subsequent Configuration Retrieval
Clients MAY request the server to return txid values in the response
by adding one or more txid values received previously in get-config
or get-data requests.
When a NETCONF server receives a get-config or get-data request
containing a node with a client specified txid value, there are
several different cases:
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* The node is not a versioned node, i.e. the server does not
maintain a txid value for this node. In this case, the server
MUST look up the closest ancestor that is a versioned node, and
use the txid value of that node as the txid value of this node in
the further handling below. The datastore root is always a
versioned node.
* The client specified txid value is different than the server's
txid value for this node. In this case the server MUST return the
contents as it would otherwise have done, adding the txid values
of all child versioned nodes to the response. In case the client
has specified txid values for some child nodes, then these cases
MUST be re-evaluated for those child nodes.
* The client specified txid value matches the server's txid value.
In this case the server MUST return the node decorated with a
special "txid-match" txid value (e.g. "=") to the matching node,
pruning any value and child nodes. A server MUST NOT ever use the
txid-match value (e.g. "=") as an actual txid value.
For list elements, pruning child nodes means that top-level key nodes
MUST be included in the response, and other child nodes MUST NOT be
included. For containers, child nodes MUST NOT be included.
Client Server
| |
| ------------------------------------------> |
| get-config |
| acls (txid: 5152) |
| acl A1 (txid: 4711) |
| aces (txid: 4711) |
| acl A2 (txid: 5152) |
| aces (txid: 5152) |
| |
| <------------------------------------------ |
| data |
| acls (txid: =) |
v v
Figure 2: Response Pruning. Client sends get-config request with
known txid values. Server prunes response where txid matches
expectations.
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Client Server
| |
| ------------------------------------------> |
| get-config |
| acls (txid: 5152) |
| acl A1 (txid: 4711) |
| acl A2 (txid: 5152) |
| |
| <------------------------------------------ |
| data |
| acls (txid: 6614) |
| acl A1 (txid: =) |
| acl A2 (txid: 6614) |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp AF11 |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
v v
Figure 3: Out of band change detected. Client sends get-config
request with known txid values. Server provides update where
changes have happened. Specifically ace R8 is returned since ace
R8 is a child of a node for which the request had a different
txid than the server, and the client did not specify any matching
txid for the ace R8 node.
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Client Server
| |
| ------------------------------------------> |
| get-config |
| acls |
| acls A2 |
| aces |
| ace R7 |
| matches |
| ipv4 |
| dscp (txid: 4711) |
| |
| <------------------------------------------ |
| data |
| acls |
| acl A2 |
| aces |
| ace R7 |
| matches |
| ipv4 |
| dscp (txid: =) |
v v
Figure 4: Versioned nodes. Server lookup of dscp txid gives
4711, as closest ancestor is ace R7 with txid 4711. Since the
server's and client's txid match, the etag value is '=', and the
leaf value is pruned.
3.5. Configuration Retrieval from the Candidate Datastore
When a client retrieves the configuration from the candidate
datastore, some of the configuration nodes may hold the same data as
the corresponding node in the running datastore. In such cases, the
server MUST return the same txid value for nodes in the candidate
datastore as in the running datastore.
If a node in the candidate datastore holds different data than in the
running datastore, the server has a choice of what to return.
* The server MAY return a txid-unknown value (e.g. "!"). This may
be convenient in servers that do not know a priori what txids will
be used in a future, possible commit of the canidate.
* If the txid-unknown value is not returned, the server MUST return
he txid value the node will have after commit, assuming the client
makes no further changes of the candidate datastore.
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See the example in Transactions toward the Candidate Datastore
(Section 3.7).
3.6. Conditional Transactions
Conditional transactions are useful when a client is interested to
make a configuration change, being sure that relevant parts of the
server configuration have not changed since the client last inspected
it.
By supplying the latest txid values known to the client in its change
requests (edit-config etc.), it can request the server to reject the
transaction in case any relevant changes have occurred at the server
that the client is not yet aware of.
This allows a client to reliably compute and send confiuguration
changes to a server without either acquiring a global datastore lock
for a potentially extended period of time, or risk that a change from
another client disrupts the intent in the time window between a read
(get-config etc.) and write (edit-config etc.) operation.
Clients that are also interested to know the txid assigned to the
modified versioned nodes in the model immediately in the response
could set a flag in the rpc message to request the server to return
the new txid with the ok message.
Client Server
| |
| ------------------------------------------> |
| edit-config (request new txid in response) |
| config (txid: 5152) |
| acls (txid: 5152) |
| acl A1 (txid: 4711) |
| aces (txid: 4711) |
| ace R1 (txid: 4711) |
| matches ipv4 protocol tcp |
| |
| <------------------------------------------ |
| ok (txid: 7688) |
v v
Figure 5: Conditional transaction towards the Running datastore
successfully executed. As all the txid values specified by the
client matched those on the server, the transaction was
successfully executed.
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Client Server
| |
| ------------------------------------------> |
| get-config |
| acls (txid: ?) |
| |
| <------------------------------------------ |
| data |
| acls (txid: 7688) |
| acl A1 (txid: 7688) |
| aces (txid: 7688) |
| ace R1 (txid: 7688) |
| matches ipv4 protocol tcp |
| acl A2 (txid: 6614) |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp AF11 |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
v v
Figure 6: The txids are updated on all versioned nodes that were
modified themselves or have a child node that was modified.
If the server rejects the transaction because one or more of the
configuration txid value(s) differs from the client's expectation,
the server MUST return at least one rpc-error with the following
values:
error-tag: operation-failed
error-type: protocol
error-severity: error
Additionally, the error-info tag MUST contain an sx:structure
containing relevant details about one of the mismatching txids. A
server MAY send multiple rpc-errors when multiple txid mismatches are
detected.
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Client Server
| |
| ------------------------------------------> |
| edit-config |
| config |
| acls |
| acl A1 (txid: 4711) |
| aces (txid: 4711) |
| ace R1 (txid: 4711) |
| ipv4 dscp AF22 |
| |
| <------------------------------------------ |
| rpc-error |
| error-tag operation-failed |
| error-type protocol |
| error-severity error |
| error-info |
| mismatch-path /acls/acl[A1] |
| mismatch-etag-value 6912 |
v v
Figure 7: Conditional transaction that fails a txid check. The
client wishes to ensure there has been no changes to the
particular acl entry it edits, and therefore sends the txid it
knows for this part of the configuration. Since the txid has
changed (out of band), the server rejects the configuration
change request and reports an error with details about where the
mismatch was detected.
3.7. Transactions toward the Candidate Datastore
When working with the Candidate datastore, the txid validation
happens at commit time, rather than at individual edit-config or
edit-data operations. Clients add their txid attributes to the
configuration payload the same way. In case a client specifies
different txid values for the same element in successive edit-config
or edit-data operations, the txid value specified last MUST be used
by the server at commit time.
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Client Server
| |
| ------------------------------------------> |
| edit-config (operation: merge) |
| config (txid: 5152) |
| acls (txid: 5152) |
| acl A1 (txid: 4711) |
| type ipv4 |
| |
| <------------------------------------------ |
| ok |
| |
| ------------------------------------------> |
| edit-config (operation: merge) |
| config |
| acls |
| acl A1 |
| aces (txid: 4711) |
| ace R1 (txid: 4711) |
| matches ipv4 protocol tcp |
| |
| <------------------------------------------ |
| ok |
| |
| ------------------------------------------> |
| get-config |
| config |
| acls |
| acl A1 |
| aces (txid: ?) |
| |
| <------------------------------------------ |
| config |
| acls |
| acl A1 |
| aces (txid: 7688 or !) |
| ace R1 (txid: 7688 or !) |
| matches ipv4 protocol tcp |
| ace R2 (txid: 2219) |
| matches ipv4 dscp 21 |
| |
| ------------------------------------------> |
| commit (request new txid in response) |
| |
| <------------------------------------------ |
| ok (txid: 7688) |
v v
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Figure 8: Conditional transaction towards the Candidate datastore
successfully executed. As all the txid values specified by the
client matched those on the server at the time of the commit, the
transaction was successfully executed. If a client issues a get-
config towards the candidate datastore, the server may choose to
return the special txid-unknown value (e.g. "!") or the txid
value that would be used if the candidate was committed without
further changes (when that txid value is known in advance by the
server).
3.8. Dependencies within Transactions
YANG modules that contain when-statements referencing remote parts of
the model will cause the txid to change even in parts of the data
tree that were not modified directly.
Let's say there is an energy-example.yang module that defines a
mechanism for clients to request the server to measure the amount of
energy that is consumed by a given access control rule. The energy-
example module augments the access control module as follows:
module energy-example {
...
container energy {
leaf metering-enabled {
type boolean;
default false;
}
}
augment /acl:acls/acl:acl {
when /energy-example:energy/energy-example:metering-enabled;
leaf energy-tracing {
type boolean;
default false;
}
leaf energy-consumption {
config false;
type uint64;
units J;
}
}
}
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This means there is a system wide switch leaf metering-enabled in
energy-example which disables all energy measurements in the system
when set to false, and that there is a boolean leaf energy-tracing
that controls whether energy measurement is happening for each acl
rule individually.
In this example, we have an initial configuration like this:
Client Server
| |
| ------------------------------------------> |
| get-config |
| energy (txid: ?) |
| acls (txid: ?) |
| |
| <------------------------------------------ |
| data (txid: 7688) |
| energy metering-enabled true (txid: 4711) |
| acls (txid: 7688) |
| acl A1 (txid: 7688) |
| energy-tracing false |
| aces (txid: 7688) |
| ace R1 (txid: 7688) |
| matches ipv4 protocol tcp |
| acl A2 (txid: 6614) |
| energy-tracing true |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp AF11 |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
v v
Figure 9: Initial configuration for the energy example. Note the
energy metering-enabled leaf at the top and energy-tracing leafs
under each acl.
At this point, a client updates metering-enabled to false. This
causes the when-expression on energy-tracing to turn false, removing
the leaf entirely. This counts as a configuration change, and the
txid MUST be updated appropriately.
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Client Server
| |
| ------------------------------------------> |
| edit-config (request new txid in response) |
| config |
| energy metering-enabled false |
| |
| <------------------------------------------ |
| ok (txid: 9118) |
v v
Figure 10: Transaction changing a single leaf. This leaf is the
target of a when-statement, however, which means other leafs
elsewhere may be indirectly modified by this change. Such
indirect changes will also result in txid changes.
After the transaction above, the new configuration state has the
energy-tracing leafs removed. Every such removal or (re)introduction
of a node counts as a configuration change from a txid perspective,
regardless of whether the change has any net configuration change
effect in the server.
Client Server
| |
| ------------------------------------------> |
| get-config |
| energy (txid: ?) |
| acls (txid: ?) |
| |
| <------------------------------------------ |
| data (txid: 9118) |
| energy metering-enabled false (txid: 9118) |
| acls (txid: 9118) |
| acl A1 (txid: 9118) |
| aces (txid: 7688) |
| ace R1 (txid: 7688) |
| matches ipv4 protocol tcp |
| acl A2 (txid: 9118) |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp AF11 |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
v v
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Figure 11: The txid for the energy subtree has changed since that
was the target of the edit-config. The txids of the ACLs have
also changed since the energy-tracing leafs are now removed by
the now false when- expression. Both acl A1 and acl A2 have
their txids updated, even though energy-tracing was already false
for acl A1.
3.9. Other NETCONF Operations
discard-changes The discard-changes operation resets the candidate
datastore to the contents of the running datastore. The server
MUST ensure the txid values in the candidate datastore get the
same txid values as in the running datastore when this operation
runs.
copy-config The copy-config operation can be used to copy contents
between datastores. The server MUST ensure the txid values are
retained and changed as if the data being copied had been sent in
through an edit-config operation.
delete-config The server MUST ensure the datastore txid value is
changed, unless it was already empty.
commit At commit, with regards to the txid values, the server MUST
treat the contents of the candidate datastore as if any txid value
provided by the client when updating the candidate was provided in
a single edit-config towards the running datastore. If the
transaction is rejected due to txid value mismatch, an rpc-error
as described in section Conditional Transactions (Section 3.6)
MUST be sent.
3.10. YANG-Push Subscriptions
A client issuing a YANG-Push establish-subscription or modify-
subscription request towards a server that supports both YANG-Push
[RFC8641] and a txid mechanism MAY request that the server provides
updated txid values in YANG-Push subscription updates.
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Client Server
| |
| ------------------------------------------> |
| rpc |
| establish-subscription |
| datastore running |
| datastore-xpath-filter /acls |
| periodic 500 |
| with-etag true |
| |
| <------------------------------------------ |
| ok |
| |
| <------------------------------------------ |
| notification |
| eventTime 2022-04-04T06:00:24.16Z |
| push-change-update |
| id 89 |
| datastore-changes |
| yang-patch |
| patch-id 0 |
| edit (txid: 8008) |
| edit-id edit1 |
| operation delete |
| target /acls |
| value |
| acl |
| name A1 |
| |
v v
Figure 12: A client requests a YANG-Push subscription for a given
path with txid values included. Later, when the server delivers
a push-change- update notification, the txid is included.
4. Txid Mechanisms
This document defines two txid mechanisms:
* The etag attribute txid mechanism
* The last-modified attribute txid mechanism
Servers implementing this specification MUST support the etag
attribute txid mechanism and MAY support the last-modified attribute
txid mechanism.
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Section NETCONF Txid Extension (Section 3) describes the logic that
governs all txid mechanisms. This section describes the mapping from
the generic logic to specific mechanism and encoding.
If a client uses more than one txid mechanism, such as both etag and
last-modified in a particular message to a server, or patricular
commit, the result is undefined.
4.1. The etag attribute txid mechanism
The etag txid mechanism described in this section is centered around
a meta data XML attribute called "etag". The etag attribute is
defined in the namespace "urn:ietf:params:xml:ns:netconf:txid:1.0".
The etag attribute is added to XML elements in the NETCONF payload in
order to indicate the txid value for the YANG node represented by the
element.
NETCONF servers that support this extension MUST announce the
capability "urn:ietf:params:netconf:capability:txid:etag:1.0".
The etag attribute values are opaque UTF-8 strings chosen freely,
except that the etag string must not contain space, backslash or
double quotes. The point of this restriction is to make it easy to
reuse implementations that adhere to section 2.3.1 in [RFC7232]. The
probability SHOULD be made very low that an etag value that has been
used historically by a server is used again by that server if the
configuration is different.
It is RECOMMENDED that the same etag txid values are used across all
management interfaces (i.e. NETCONF, RESTCONF and any other the
server might implement), if it implements more than one.
The detailed rules for when to update the etag value are described in
section General Txid Principles (Section 3.2). These rules are
chosen to be consistent with the ETag mechanism in RESTCONF,
[RFC8040], specifically sections 3.4.1.2, 3.4.1.3 and 3.5.2.
4.2. The last-modified attribute txid mechanism
The last-modified txid mechanism described in this section is
centered around a meta data XML attribute called "last-modified".
The last-modified attribute is defined in the namespace
"urn:ietf:params:xml:ns:netconf:txid:1.0". The last-modified
attribute is added to XML elements in the NETCONF payload in order to
indicate the txid value for the YANG node represented by the element.
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NETCONF servers that support this extension MUST announce the
capability "urn:ietf:params:netconf:capability:txid:last-
modified:1.0".
The last-modified attribute values are yang:date-and-time values as
defined in ietf-yang-types.yang, [RFC6991].
"2022-04-01T12:34:56.123456Z" is an example of what this time stamp
format looks like. It is RECOMMENDED that the time stamps provided
by the server to closely match the real world clock. Servers MUST
ensure the timestamps provided are monotonously increasing for as
long as the server's operation is maintained.
It is RECOMMENDED that server implementors choose the number of
digits of precision used for the fractional second timestamps high
enough so that there is no risk that multiple transactions on the
server would get the same timestamp.
It is RECOMMENDED that the same last-modified txid values are used
across all management interfaces (i.e. NETCONF and any other the
server might implement), except RESTCONF.
RESTCONF, as defined in [RFC8040], is using a different format for
the time stamps which is limited to one second resolution. Server
implementors that support the Last-Modified txid mechanism over both
RESTCONF and other management protocols are RECOMMENDED to use Last-
Modified timestamps that match the point in time referenced over
RESTCONF, with the fractional seconds part added.
The detailed rules for when to update the last-modified value are
described in section General Txid Principles (Section 3.2). These
rules are chosen to be consistent with the Last-Modified mechanism in
RESTCONF, [RFC8040], specifically sections 3.4.1.1, 3.4.1.3 and
3.5.1.
4.3. Common features to both etag and last-modified txid mechanisms
Clients MAY add etag or last-modified attributes to zero or more
individual elements in the get-config or get-data filter, in which
case they pertain to the subtree(s) rooted at the element(s) with the
attributes.
Clients MAY also add such attributes directly to the get-config or
get-data tags (e.g. if there is no filter), in which case it pertains
to the txid value of the datastore root.
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Clients might wish to send a txid value that is guaranteed to never
match a server constructed txid. With both the etag and last-
modified txid mechanisms, such a txid-request value is "?".
Clients MAY add etag or last-modified attributes to the payload of
edit-config or edit-data requests, in which case they indicate the
client's txid value of that element.
Clients MAY request servers that also implement YANG-Push to return
configuration change subsription updates with etag or last-modified
txid attributes. The client requests this service by adding a with-
etag or with-last-modified flag with the value 'true' to the
subscription request or yang-push configuration. The server MUST
then return such txids on the YANG Patch edit tag and to the child
elements of the value tag. The txid attribute on the edit tag
reflects the txid associated with the changes encoded in this edit
section, as well as parent nodes. Later edit sections in the same
push-update or push-change-update may still supercede the txid value
for some or all of the nodes in the current edit section.
Servers returning txid values in get-config, edit-config, get-data,
edit-data and commit operations MUST do so by adding etag and/or
last-modified txid attributes to the data and ok tags. When servers
prune output due to a matching txid value, the server MUST add a
txid-match attribute to the pruned element, and MUST set the
attribute value to "=", and MUST NOT send any element value.
Servers returning a txid mismatch error MUST return an rpc-error as
defined in section Conditional Transactions (Section 3.6) with an
error-info tag containing a txid-value-mismatch-error-info structure.
4.3.1. Candidate Datastore
When servers return txid values in get-config and get-data operations
towards the candidate datastore, the txid values returned MUST adhere
to the following rules:
* If the versioned node holds the same data as in the running
datastore, the same txid value as the versioned node in running
MUST be used.
* If the versioned node is different in the candidata store than in
the running datastore, the server has a choice of what to return.
The server MAY return the special "txid-unknown" value "!". If
the txid-unknown value is not returned, the server MUST return the
txid value the versioned node will have if the client decides to
commit the candidate datastore without further updates.
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4.3.2. Namespaces and Attribute Placement
The txid attributes are valid on the following NETCONF tags, where
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0",
xmlns:ncds="urn:ietf:params:xml:ns:yang:ietf-netconf-nmda",
xmlns:sn="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications",
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-patch" and
xmlns:ypatch="urn:ietf:params:xml:ns:yang:ietf-yang-patch":
In client messages sent to a server:
* /nc:rpc/nc:get-config
* /nc:rpc/nc:get-config/nc:filter//*
* /nc:rpc/ncds:get-data
* /nc:rpc/ncds:get-data/ncds:subtree-filter//*
* /nc:rpc/ncds:get-data/ncds:xpath-filter//*
* /nc:rpc/nc:edit-config/nc:config
* /nc:rpc/nc:edit-config/nc:config//*
* /nc:rpc/ncds:edit-data/ncds:config
* /nc:rpc/ncds:edit-data/ncds:config//*
In server messages sent to a client:
* /nc:rpc-reply/nc:data
* /nc:rpc-reply/nc:data//*
* /nc:rpc-reply/ncds:data
* /nc:rpc-reply/ncds:data//*
* /nc:rpc-reply/nc:ok
* /yp:push-update/yp:datastore-contents/ypatch:yang-patch/
ypatch:edit
* /yp:push-update/yp:datastore-contents/ypatch:yang-patch/
ypatch:edit/ypatch:value//*
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* /yp:push-change-update/yp:datastore-contents/ypatch:yang-patch/
ypatch:edit
* /yp:push-change-update/yp:datastore-contents/ypatch:yang-patch/
ypatch:edit/ypatch:value//*
5. Txid Mechanism Examples
5.1. Initial Configuration Response
5.1.1. With etag
NOTE: In the etag examples below, we have chosen to use a txid value
consisting of "nc" followed by a monotonously increasing integer.
This is convenient for the reader trying to make sense of the
examples, but is not an implementation requirement. An etag would
often be implemented as a "random" string of characters, with no
comes-before/after relation defined.
To retrieve etag attributes across the entire NETCONF server
configuration, a client might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config txid:etag="?"/>
</rpc>
The server's reply might then be:
<rpc-reply message-id="1"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data txid:etag="nc5152">
<acls xmlns=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc5152">
<acl txid:etag="nc4711">
<name>A1</name>
<aces txid:etag="nc4711">
<ace txid:etag="nc4711">
<name>R1</name>
<matches>
<ipv4>
<protocol>udp</protocol>
</ipv4>
</matches>
</ace>
</aces>
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</acl>
<acl txid:etag="nc5152">
<name>A2</name>
<aces txid:etag="nc5152">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>22</port>
</source-port>
</tcp>
</matches>
</ace>
</aces>
</acl>
</acls>
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"
txid:etag="nc3072">
<groups txid:etag="nc3072">
<group txid:etag="nc3072">
<name>admin</name>
<user-name>sakura</user-name>
<user-name>joe</user-name>
</group>
</groups>
</nacm>
</data>
</rpc>
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To retrieve etag attributes for a specific ACL using an xpath filter,
a client might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="2"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config>
<source>
<running/>
</source>
<filter type="xpath"
xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list"
select="/acl:acls/acl:acl[acl:name='A1']"
txid:etag="?"/>
</get-config>
</rpc>
To retrieve etag attributes for "acls", but not for "nacm", a client
might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="3"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config>
<source>
<running/>
</source>
<filter>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="?"/>
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"/>
</filter>
</get-config>
</rpc>
If the server considers "acls", "acl", "aces" and "acl" to be
versioned nodes, the server's response to the request above might
look like:
<rpc-reply message-id="3"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls xmlns=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc5152">
<acl txid:etag="nc4711">
<name>A1</name>
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<aces txid:etag="nc4711">
<ace txid:etag="nc4711">
<name>R1</name>
<matches>
<ipv4>
<protocol>udp</protocol>
</ipv4>
</matches>
</ace>
</aces>
</acl>
<acl txid:etag="nc5152">
<name>A2</name>
<aces txid:etag="nc5152">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>22</port>
</source-port>
</tcp>
</matches>
</ace>
</aces>
</acl>
</acls>
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"/>
<groups>
<group>
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<name>admin</name>
<user-name>sakura</user-name>
<user-name>joe</user-name>
</group>
</groups>
</nacm>
</data>
</rpc>
5.1.2. With last-modified
To retrieve last-modified attributes for "acls", but not for "nacm",
a client might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="4"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config>
<source>
<running/>
</source>
<filter>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:last-modified="?"/>
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"/>
</filter>
</get-config>
</rpc>
If the server considers "acls", "acl", "aces" and "acl" to be
versioned nodes, the server's response to the request above might
look like:
<rpc-reply message-id="4"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:last-modified="2022-04-01T12:34:56.789012Z">
<acl txid:last-modified="2022-03-20T16:20:11.333444Z">
<name>A1</name>
<aces txid:last-modified="2022-03-20T16:20:11.333444Z">
<ace txid:last-modified="2022-03-20T16:20:11.333444Z">
<name>R1</name>
<matches>
<ipv4>
<protocol>udp</protocol>
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</ipv4>
</matches>
</ace>
</aces>
</acl>
<acl txid:last-modified="2022-04-01T12:34:56.789012Z">
<name>A2</name>
<aces txid:last-modified="2022-04-01T12:34:56.789012Z">
<ace txid:last-modified="2022-03-20T16:20:11.333444Z">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
<ace txid:last-modified="2022-04-01T12:34:56.789012Z">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
</ace>
<ace txid:last-modified="2022-04-01T12:34:56.789012Z">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>22</port>
</source-port>
</tcp>
</matches>
</ace>
</aces>
</acl>
</acls>
<nacm xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-acm"/>
<groups>
<group>
<name>admin</name>
<user-name>sakura</user-name>
<user-name>joe</user-name>
</group>
</groups>
</nacm>
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</data>
</rpc>
5.2. Configuration Response Pruning
A NETCONF client that already knows some txid values MAY request that
the configuration retrieval request is pruned with respect to the
client's prior knowledge.
To retrieve only changes for "acls" that do not have the last known
etag txid value, a client might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="6"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config>
<source>
<running/>
</source>
<filter>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc5152">
<acl txid:etag="nc4711">
<name>A1</name>
<aces txid:etag="nc4711"/>
</acl>
<acl txid:etag="nc5152">
<name>A2</name>
<aces txid:etag="nc5152"/>
</acl>
</filter>
</get-config>
</rpc>
Assuming the NETCONF server configuration is the same as in the
previous rpc-reply example, the server's response to request above
might look like:
<rpc-reply message-id="6"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="="/>
</data>
</rpc>
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Or, if a configuration change has taken place under /acls since the
client was last updated, the server's response may look like:
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<rpc-reply message-id="6"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc6614">
<acl txid:etag="=">
<name>A1</name>
</acl>
<acl txid:etag="nc6614">
<name>A2</name>
<aces txid:etag="nc6614">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<ipv4>
<source-port>
<port>22</port>
</source-port>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc6614">
<name>R9</name>
<matches>
<ipv4>
<source-port>
<port>830</port>
</source-port>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc>
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In case the client provides a txid value for a non-versioned node,
the server needs to treat the node as having the same txid value as
the closest ancestor that does have a txid value.
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="7"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<get-config>
<source>
<running/>
</source>
<filter>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
<acl>
<name>A2</name>
<aces>
<ace>
<name>R7</name>
<matches>
<ipv4>
<dscp txid:etag="nc4711"/>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</filter>
</get-config>
</rpc>
If a txid value is specified for a leaf, and the txid value matches,
the leaf value is pruned.
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<rpc-reply message-id="7"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
<acl>
<name>A2</name>
<aces>
<ace>
<name>R7</name>
<matches>
<ipv4>
<dscp txid:etag="="/>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc-reply>
5.3. Configuration Change
A client that wishes to update the ace R1 protocol to tcp might send:
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<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="8">
<edit-config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:ietf-netconf-txid=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid">
<target>
<running/>
</target>
<test-option>test-then-set</test-option>
<ietf-netconf-txid:with-etag>true<ietf-netconf-txid:with-etag>
<config>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc5152">
<acl txid:etag="nc4711">
<name>A1</name>
<aces txid:etag="nc4711">
<ace txid:etag="nc4711">
<matches>
<ipv4>
<protocol>tcp</protocol>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</config>
</edit-config>
</rpc>
The server would update the protocol leaf in the running datastore,
and return an rpc-reply as follows:
<rpc-reply message-id="8"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<ok txid:etag="nc7688"/>
</rpc-reply>
A subsequent get-config request for "acls", with txid:etag="?" might
then return:
<rpc-reply message-id="9"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
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txid:etag="nc7688">
<acl txid:etag="nc7688">
<name>A1</name>
<aces txid:etag="nc7688">
<ace txid:etag="nc7688">
<name>R1</name>
<matches>
<ipv4>
<protocol>tcp</protocol>
</ipv4>
</matches>
</ace>
</aces>
</acl>
<acl txid:etag="nc6614">
<name>A2</name>
<aces txid:etag="nc6614">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
</ace>
<ace txid:etag="nc6614">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>830</port>
</source-port>
</tcp>
</matches>
</ace>
</aces>
</acl>
</acls>
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</data>
</rpc>
In case the server at this point received a configuration change from
another source, such as a CLI operator, removing ace R8 and R9 in acl
A2, a subsequent get-config request for acls, with txid:etag="?"
might then return:
<rpc-reply message-id="9"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="cli2222">
<acl txid:etag="nc7688">
<name>A1</name>
<aces txid:etag="nc7688">
<ace txid:etag="nc7688">
<name>R1</name>
<matches>
<ipv4>
<protocol>tcp</protocol>
</ipv4>
</matches>
</ace>
</aces>
</acl>
<acl txid:etag="cli2222">
<name>A2</name>
<aces txid:etag="cli2222">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc>
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5.4. Conditional Configuration Change
If a client wishes to delete acl A1 if and only if its configuration
has not been altered since this client last synchronized its
configuration with the server, at which point it received the etag
"nc7688" for acl A1, regardless of any possible changes to other
acls, it might send:
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="10"
xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0"
xmlns:ietf-netconf-txid=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid">
<edit-config>
<target>
<runnign/>
</target>
<test-option>test-then-set</test-option>
<ietf-netconf-txid:with-etag>true<ietf-netconf-txid:with-etag>
<config>
<acls xmlns=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
<acl nc:operation="delete"
txid:etag="nc7688">
<name>A1</name>
</acl>
</acls>
</config>
</edit-config>
</rpc>
If acl A1 now has the etag txid value "nc7688", as expected by the
client, the transaction goes through, and the server responds
something like:
<rpc-reply message-id="10"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<ok txid:etag="nc8008"/>
</rpc-reply>
A subsequent get-config request for acls, with txid:etag="?" might
then return:
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<rpc-reply message-id="11"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc8008">
<acl txid:etag="cli2222">
<name>A2</name>
<aces txid:etag="cli2222">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>AF11</dscp>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc>
In case acl A1 did not have the expected etag txid value "nc7688",
when the server processed this request, it rejects the transaction,
and might send:
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<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list"
xmlns:ietf-netconf-txid=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid"
message-id="11">
<rpc-error>
<error-type>protocol</error-type>
<error-tag>operation-failed</error-tag>
<error-severity>error</error-severity>
<error-info>
<ietf-netconf-txid:txid-value-mismatch-error-info>
<ietf-netconf-txid:mismatch-path>
/acl:acls/acl:acl[acl:name="A1"]
</ietf-netconf-txid:mismatch-path>
<ietf-netconf-txid:mismatch-etag-value>
cli6912
</ietf-netconf-txid:mismatch-etag-value>
</ietf-netconf-txid:txid-value-mismatch-error-info>
</error-info>
</rpc-error>
</rpc-reply>
5.5. Reading from the Candidate Datastore
Let's assume that a get-config towards the running datastore
currently contains the following data and txid values:
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<rpc-reply message-id="12"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
txid:etag="nc4711">
<acl txid:etag="nc4711">
<name>A1</name>
<aces txid:etag="nc4711">
<ace txid:etag="nc4711">
<name>R1</name>
<matches>
<ipv4>
<protocol>udp</protocol>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc2219">
<name>R2</name>
<matches>
<ipv4>
<dscp>21</dscp>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc-reply>
A client issues discard-changes (to make the candidate datastore
equal to the running datastore), and issues an edit-config to change
the R1 protocol from udp to tcp, and then executes a get-config with
the txid-request attribute "?" set on the acl A1, the server might
respond:
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<rpc-reply message-id="13"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<data>
<acls
xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
<acl txid:etag="!">
<name>A1</name>
<aces txid:etag="!">
<ace txid:etag="!">
<name>R1</name>
<matches>
<ipv4>
<protocol>tcp</protocol>
</ipv4>
</matches>
</ace>
<ace txid:etag="nc2219">
<name>R2</name>
<matches>
<ipv4>
<dscp>21</dscp>
</ipv4>
</matches>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc-reply>
Here, the txid-unknown value "!" is sent by the server. This
particular server implementation does not know beforehand which txid
value would be used for this versioned node after commit. It will be
a value different from the current corresponding txid value in the
running datastore.
In case the server is able to predict the txid value that would be
used for the versioned node after commit, it could respond with that
value instead. Let's say the server knows the txid would be "7688"
if the candidate datastore was committed without further changes,
then it would respond with that value in each place where the example
shows "!" above.
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5.6. Commit
The client MAY request that the new etag txid value is returned as an
attribute on the ok response for a successful commit. The client
requests this by adding with-etag to the commit operation.
For example, a client might send:
<rpc message-id="14"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
xmlns:ietf-netconf-txid=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid"
<commit>
<ietf-netconf-txid:with-etag>true<ietf-netconf-txid:with-etag>
</commit>
</rpc>
Assuming the server accepted the transaction, it might respond:
<rpc-reply message-id="15"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:txid="urn:ietf:params:xml:ns:netconf:txid:1.0">
<ok txid:etag="nc8008"/>
</rpc-reply>
5.7. YANG-Push
A client MAY request that the updates for one or more YANG Push
subscriptions are annotated with the txid values. The request might
look like this:
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<netconf:rpc message-id="16"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns=
"urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"
xmlns:ietf-netconf-txid-yp=
"urn:ietf:params:xml:ns:yang:ietf-txid-yang-push">
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:running
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
/acl:acls
</yp:datastore-xpath-filter>
<yp:periodic>
<yp:period>500</yp:period>
</yp:periodic>
<ietf-netconf-txid-yp:with-etag>
true
</ietf-netconf-txid-yp:with-etag>
</establish-subscription>
</netconf:rpc>
In case a client wishes to modify a previous subscription request in
order to no longer receive YANG Push subscription updates, the
request might look like this:
<rpc message-id="17"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<modify-subscription
xmlns=
"urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"
xmlns:ietf-netconf-txid-yp=
"urn:ietf:params:xml:ns:yang:ietf-txid-yang-push">
<id>1011</id>
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:running
</yp:datastore>
<ietf-netconf-txid-yp:with-etag>
false
</ietf-netconf-txid-yp:with-etag>
</modify-subscription>
</rpc>
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A server might send a subscription update like this:
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2022-04-04T06:00:24.16Z</eventTime>
<push-change-update
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<id>89</id>
<datastore-changes>
<yang-patch>
<patch-id>0</patch-id>
<edit txid:etag="nc8008">
<edit-id>edit1</edit-id>
<operation>delete</operation>
<target xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
/acl:acls
</target>
<value>
<acl xmlns=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
<name>A1</name>
</acl>
</value>
</edit>
</yang-patch>
</datastore-changes>
</push-change-update>
</notification>
6. YANG Modules
6.1. Base module for txid in NETCONF
<CODE BEGINS>
module ietf-netconf-txid {
yang-version 1.1;
namespace
'urn:ietf:params:xml:ns:yang:ietf-netconf-txid';
prefix ietf-netconf-txid;
import ietf-netconf {
prefix nc;
}
import ietf-netconf-nmda {
prefix ncds;
}
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import ietf-yang-structure-ext {
prefix sx;
}
import ietf-yang-types {
prefix yang;
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <netconf@ietf.org>
Author: Jan Lindblad
<mailto:jlindbla@cisco.com>";
description
"NETCONF Transaction ID aware operations for NMDA.
Copyright (c) 2022 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
";
revision 2023-03-01 {
description
"Initial revision";
reference
"RFC XXXX: Xxxxxxxxx";
}
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typedef etag-t {
type string {
pattern ".* .*" {
modifier invert-match;
}
pattern '.*".*' {
modifier invert-match;
}
pattern ".*\\.*" {
modifier invert-match;
}
}
description
"Unique Entity-tag txid value representing a specific
transaction. Could be any string that does not contain
spaces, double quotes or backslash. The txid values '?',
'!' and '=' have special meaning.";
}
typedef last-modified-t {
type union {
type yang:date-and-time;
type enumeration {
enum ? {
description "Txid value used by clients that is
guaranteed not to match any txid on the server.";
}
enum ! {
description "Txid value used by servers to indicate
the node in the candidate datastore has changed
relative the running datastore, but not yet received
a new txid value on the server.";
}
enum = {
description "Txid value used by servers to indicate
that contents has been pruned due to txid match
between client and server.";
}
}
}
description
"Last-modified txid value representing a specific transaction.
The txid values '?', '!' and '=' have special meaning.";
}
grouping txid-grouping {
leaf with-etag {
type boolean;
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description
"Indicates whether the client requests the server to include
a txid:etag txid attribute when the configuration has
changed.";
}
leaf with-last-modified {
type boolean;
description
"Indicates whether the client requests the server to include
a txid:last-modified attribute when the configuration has
changed.";
}
description
"Grouping for txid mechanisms, to be augmented into
rpcs that modify configuration data stores.";
}
augment /nc:edit-config/nc:input {
uses txid-grouping;
description
"Injects the txid mechanisms into the
edit-config operation";
}
augment /nc:commit/nc:input {
uses txid-grouping;
description
"Injects the txid mechanisms into the
commit operation";
}
augment /ncds:edit-data/ncds:input {
uses txid-grouping;
description
"Injects the txid mechanisms into the
edit-data operation";
}
sx:structure txid-value-mismatch-error-info {
container txid-value-mismatch-error-info {
description
"This error is returned by a NETCONF server when a client
sends a configuration change request, with the additonal
condition that the server aborts the transaction if the
server's configuration has changed from what the client
expects, and the configuration is found not to actually
not match the client's expectation.";
leaf mismatch-path {
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type instance-identifier;
description
"Indicates the YANG path to the element with a mismatching
etag txid value.";
}
leaf mismatch-etag-value {
type etag-t;
description
"Indicates server's txid value of the etag
attribute for one mismatching element.";
}
leaf mismatch-last-modified-value {
type last-modified-t;
description
"Indicates server's txid value of the last-modified
attribute for one mismatching element.";
}
}
}
}
<CODE ENDS>
6.2. Additional support for txid in YANG-Push
<CODE BEGINS>
module ietf-netconf-txid-yang-push {
yang-version 1.1;
namespace
'urn:ietf:params:xml:ns:yang:ietf-netconf-txid-yang-push';
prefix ietf-netconf-txid-yp;
import ietf-subscribed-notifications {
prefix sn;
reference
"RFC 8639: Subscription to YANG Notifications";
}
import ietf-netconf-txid {
prefix ietf-netconf-txid;
reference
"RFC XXXX: Xxxxxxxxx";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
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WG List: <netconf@ietf.org>
Author: Jan Lindblad
<mailto:jlindbla@cisco.com>";
description
"NETCONF Transaction ID aware operations for YANG Push.
Copyright (c) 2022 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
";
revision 2022-04-01 {
description
"Initial revision";
reference
"RFC XXXX: Xxxxxxxxx";
}
augment "/sn:establish-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters
that apply specifically to datastore updates to RPC input.";
uses ietf-netconf-txid:txid-grouping;
}
augment "/sn:modify-subscription/sn:input" {
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses ietf-netconf-txid:txid-grouping;
}
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augment "/sn:subscriptions/sn:subscription" {
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses ietf-netconf-txid:txid-grouping;
}
}
<CODE ENDS>
7. Security Considerations
7.1. NACM Access Control
NACM, [RFC8341], access control processing happens as usual,
independently of any txid handling, if supported by the server and
enabled by the NACM configuration.
It should be pointed out however, that when txid information is added
to a reply, it may occasionally be possible for a client to deduce
that a configuration change has happened in some part of the
configuration to which it has no access rights.
For example, a client may notice that the root node txid has changed
while none of the subtrees it has access to have changed, and thereby
conclude that someone else has made a change to some part of the
configuration that is not acessible by the client.
7.1.1. Hash-based Txid Algorithms
Servers that implement NACM and choose to implement a hash-based txid
algorithm over the configuration may reveal to a client that the
configuration of a subtree that the client has no access to is the
same as it was at an earlier point in time.
For example, a client with partial access to the configuration might
observe that the root node txid was 1234. After a few configuration
changes by other parties, the client may again observe that the root
node txid is 1234. It may then deduce that the configuration is the
same as earlier, even in the parts of the configuration it has no
access to.
In some use cases, this behavior may be considered a feature, since
it allows a security client to verify that the configuration is the
same as expected, without transmitting or storing the actual
configuration.
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7.2. Unchanged Configuration
It will also be possible for clients to deduce that a confiuration
change has not happened during some period, by simply observing that
the root node (or other subtree) txid remains unchanged. This is
true regardless of NACM being deployed or choice of txid algorithm.
Again, there may be use cases where this behavior may be considered a
feature, since it allows a security client to verify that the
configuration is the same as expected, without transmitting or
storing the actual configuration.
8. IANA Considerations
This document registers the following capability identifier URN in
the 'Network Configuration Protocol (NETCONF) Capability URNs'
registry:
urn:ietf:params:netconf:capability:txid:1.0
This document registers three XML namespace URNs in the 'IETF XML
registry', following the format defined in [RFC3688].
URI: urn:ietf:params:xml:ns:netconf:txid:1.0
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-txid
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-txid-yang-push
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URIs are XML namespaces.
This document registers two module names in the 'YANG Module Names'
registry, defined in [RFC6020].
name: ietf-netconf-txid
prefix: ietf-netconf-txid
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-txid
RFC: XXXX
and
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name: ietf-netconf-txid-yp
prefix: ietf-netconf-txid-yp
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-txid-yang-push
RFC: XXXX
9. Changes
9.1. Major changes in -03 since -02
* Changed the logic around how txids are handled in the candidate
datastore, both when reading (get-config, get-data) and writing
(edit-config, edit-data). Introduced a special "txid-unknown"
value "!".
* Changed the logic of copy-config to be similar to edit-config.
* Clarified how txid values interact with when-dependencies together
with default values.
* Added content to security considerations.
* Added a high-level example for YANG-Push subscriptions with txid.
* Updated language about error-info sent at txid mismatch in an
edit-config: error-info with mismatch details MUST be sent when
mismatch detected, and that the server can choose one of the txid
mismatch occurrences if there is more than one.
* Some rewording and minor additions for clarification, based on
mailing list feedback.
* Divided RFC references into normative and informative.
* Corrected a logic error in the second figure (figure 6) in the
"Conditional Transactions" section
9.2. Major changes in -02 since -01
* A last-modified txid mechanism has been added (back). This
mechanism aligns well with the Last-Modified mechanism defined in
RESTCONF [RFC8040], but is not a carbon copy.
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* YANG Push functionality has been added. This allows YANG Push
users to receive txid updates as part of the configuration
updates. This functionality comes in a separate YANG module, to
allow implementors to cleanly keep all this functionality out.
* Changed name of "versioned elements". They are now called
"versioned nodes".
* Clarified txid behavior for transactions toward the Candidate
datastore, and some not so common situations, such as when a
client specifies a txid for a non-versioned node, and when there
are when-statement dependencies across subtrees.
* Examples provided for the abstract mechanism level with simple
message flow diagrams.
* More examples on protocol level, and with ietf-interfaces as
example target module replaced with ietf-access-control to reduce
confusion.
* Explicit list of XPaths to clearly state where etag or last-
modified attributes may be added by clients and servers.
* Document introduction restructured to remove duplication between
sections and to allow multiple (etag and last-modified) txid
mechanisms.
* Moved the actual YANG module code into proper module files that
are included in the source document. These modules can be
compiled as proper modules without any extraction tools.
9.3. Major changes in -01 since -00
* Updated the text on numerous points in order to answer questions
that appeared on the mailing list.
* Changed the document structure into a general transaction id part
and one etag specific part.
* Renamed entag attribute to etag, prefix to txid, namespace to
urn:ietf:params:xml:ns:yang:ietf-netconf-txid.
* Set capability string to
urn:ietf:params:netconf:capability:txid:1.0
* Changed YANG module name, namespace and prefix to match names
above.
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* Harmonized/slightly adjusted etag value space with RFC 7232 and
RFC 8040.
* Removed all text discussing etag values provided by the client
(although this is still an interesting idea, if you ask the
author)
* Clarified the etag attribute mechanism, especially when it comes
to matching against non-versioned elements, its cascading upwards
in the tree and secondary effects from when- and choice-
statements.
* Added a mechanism for returning the server assigned etag value in
get-config and get-data.
* Added section describing how the NETCONF discard-changes, copy-
config, delete-config and commit operations work with respect to
etags.
* Added IANA Considerations section.
* Removed all comments about open questions.
10. References
10.1. 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/rfc/rfc2119>.
[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/rfc/rfc6241>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/rfc/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/rfc/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/rfc/rfc8040>.
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[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/rfc/rfc8174>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/rfc/rfc8641>.
10.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/rfc/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/rfc/rfc6020>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Conditional Requests", RFC 7232,
DOI 10.17487/RFC7232, June 2014,
<https://www.rfc-editor.org/rfc/rfc7232>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/rfc/rfc8341>.
Acknowledgments
The author wishes to thank Benoit Claise for making this work happen,
and the following individuals, who all provided helpful comments: Per
Andersson, Kent Watsen, Andy Bierman, Robert Wilton, Qiufang Ma,
Jason Sterne and Robert Varga.
Author's Address
Jan Lindblad
Cisco Systems
Email: jlindbla@cisco.com
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