| Internet-Draft | NCTID | July 2023 |
| Lindblad | Expires 5 January 2024 | [Page] |
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.¶
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.¶
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."¶
This Internet-Draft will expire on 5 January 2024.¶
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.¶
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.¶
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 configuration being untouched by others. This mechanism leverages [RFC7232] "Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests".¶
This document defines similar functionality for NETCONF, [RFC6241], for config true data. It also ties this in with YANG-Push, [RFC8641], and "Comparison of Network Management Datastore Architecture (NMDA) Datastores", [RFC9144]. Config false data (operational data, state, statistics) is left out of scope from this document.¶
This document does not change the RESTCONF protocol in any way, and is carefully written to allow implementations to share much of the code between NETCONF and RESTCONF. Note that the NETCONF txid mechanism described in this document uses XML attributes, but the RESTCONF mechanism relies on HTTP Headers instead, and use none of the XML attributes described in this document, nor JSON Metadata (see [RFC7952]).¶
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], [RFC7952], [RFC8040], [RFC8641], and [RFC9144].¶
In addition, this document defines the following terms:¶
A node in the instantiated YANG data tree for which the server maintains a transaction id (txid) value.¶
A protocol implementation that fulfills the principles described in the first part, NETCONF Txid Extension (Section 3), of this document.¶
Abbreviation of Transaction-id¶
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. A similar extension is also defined for servers implememnting "Comparison of NMDA Datastores".¶
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. This document is therefore divided into a two parts; the first part discusses the txid mechanism in an abstract, protocol-neutral way. The second part, Txid Mechanisms (Section 4), then adds the protocol layer, and provides concrete encoding examples.¶
The common use cases for txid mecahnisms are briefly discussed here.¶
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.¶
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.¶
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.¶
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.¶
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.¶
All servers implementing a txid mechanism MUST maintain a top level 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.¶
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.¶
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 17 |
| actions forwarding accept |
| acl A2 (txid: 5152) |
| aces (txid: 5152) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| actions forwarding accept |
| ace R9 (txid: 5152) |
| matches tcp source-port port 22 |
| actions forwarding accept |
v v
In the call flow examples in this document 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. In general, the only operation defined on a pair of txid values is testing them for equality.¶
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 client sends in a txid value of a node that matches the server's txid value for that versioned node, the server prunes (does not return) that subtree from the response. Since the client already knows the txid for this part of the data tree, it is obviosuly already up to date with that part of the configuration, so sending it again would be a waste of time and energy.¶
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:¶
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
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 10 |
| actions forwarding accept |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| actions forwarding accept |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
| actions forwarding accept |
v v
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
When a client retrieves the configuration from the (or a) 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.¶
See the example in Candidate Datastore Transactions (Section 3.7).¶
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 configuration 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 6 |
| actions forwarding accept |
| |
| <------------------------------------------ |
| ok (txid: 7688) |
v v
Client Server
| |
| ------------------------------------------> |
| get-config |
| acls (txid: ?) |
| |
| <------------------------------------------ |
| data |
| acls (txid: 7688) |
| acl A1 (txid: 7688) |
| aces (txid: 7688) |
| ace R1 (txid: 7688) |
| matches ipv4 protocol 6 |
| actions forwarding accept |
| acl A2 (txid: 6614) |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| actions forwarding accept |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
| actions forwarding accept |
v v
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.¶
Client Server
| |
| ------------------------------------------> |
| edit-config |
| config |
| acls |
| acl A1 (txid: 4711) |
| aces (txid: 4711) |
| ace R1 (txid: 4711) |
| matches ipv4 dscp 20 |
| actions forwarding accept |
| |
| <------------------------------------------ |
| 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
When working with the (or a) 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.¶
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 6 |
| actions forwarding accept |
| |
| <------------------------------------------ |
| 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 6 |
| actions forwarding accept |
| ace R2 (txid: 2219) |
| matches ipv4 dscp 21 |
| actions forwarding accept |
| |
| ------------------------------------------> |
| commit (request new txid in response) |
| |
| <------------------------------------------ |
| ok (txid: 7688) |
v v
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;
}
}
}
¶
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 6 |
| actions forwarding accept |
| acl A2 (txid: 6614) |
| energy-tracing true |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| actions forwarding accept |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
| actions forwarding accept |
v v
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.¶
Client Server
| |
| ------------------------------------------> |
| edit-config (request new txid in response) |
| config |
| energy metering-enabled false |
| |
| <------------------------------------------ |
| ok (txid: 9118) |
v v
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 6 |
| actions forwarding accept |
| acl A2 (txid: 9118) |
| aces (txid: 6614) |
| ace R7 (txid: 4711) |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| ace R8 (txid: 5152) |
| matches udp source-port port 22 |
| actions forwarding accept |
| ace R9 (txid: 6614) |
| matches tcp source-port port 830 |
| actions forwarding accept |
v v
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.¶
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.¶
The server MUST ensure the datastore txid value is changed, unless it was already empty.¶
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.¶
A client issuing a YANG-Push establish-subscription or modify-subscription request towards a server that supports ietf-netconf-txid-yang-push.yang MAY request that the server provides updated txid values in YANG-Push on-change subscription updates.¶
This functionality pertains only to on-change updates. This RPC may also be invoked over RESTCONF or other protocols, and might therefore be encoded in JSON.¶
To request txid values (e.g. etag), the client adds a flag in the request (e.g. with-etag). The server then returns the txid (e.g. etag) value in the yang-patch payload (e.g. as etag-value).¶
Client Server
| |
| ------------------------------------------> |
| rpc |
| establish-subscription |
| datastore running |
| datastore-xpath-filter /acls |
| on-change |
| 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 |
| edit-id edit1 |
| operation delete |
| target /acls/acl[A1] |
| edit |
| edit-id edit2 |
| operation merge |
| target /acls/acl[A2]/ace[R7] |
| value |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| etag-value 8008 |
| |
v v
A client issuing an NMDA Datastore compare request towards a server that supports ietf-netconf-txid-nmda-compare.yang MAY request that the server provides updated txid values in the compare reply. Besides NETCONF, this RPC may also be invoked over RESTCONF or other protocols, and might therefore be encoded in JSON.¶
To request txid values (e.g. etag), the client adds a flag in the request (e.g. with-etag). The server then returns the txid (e.g. etag) value in the yang-patch payload (e.g. as etag-value).¶
The txid value returned by the server MUST be the txid value pertaining to the target node in the source or target datastores that is the most recent. If one of the datastores being compared is not a configuration datastore, the txid in the configuration datastore MUST be used. If none of the datastores being compared are a configuration datastore, then txid values MUST NOT be returned at all.¶
The txid to return is the one that pertains to the target node, or in the case of delete, the closest surviving ancestor of the target node.¶
Client Server
| |
| ------------------------------------------> |
| rpc |
| compare |
| source ds:running |
| target ds:operational |
| with-etag true |
| |
| <------------------------------------------ |
| differences |
| yang-patch |
| patch-id 0 |
| edit |
| edit-id edit1 |
| operation delete |
| target /acls/acl[A1] |
| etag-value 8008 |
| edit |
| edit-id edit2 |
| operation merge |
| target /acls/acl[A2]/ace[R7] |
| value |
| matches ipv4 dscp 10 |
| actions forwarding accept |
| etag-value 8008 |
| |
v v
This document defines two txid mechanisms:¶
Servers implementing this specification MUST support the etag attribute txid mechanism and MAY support the last-modified attribute txid mechanism.¶
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.¶
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.¶
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.¶
NETCONF servers that support this extension MUST announce the feature txid-last-modified defined in ietf-netconf-txid.yang.¶
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 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.¶
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.¶
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.¶
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:¶
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:¶
In server messages sent to a client:¶
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>17</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
<acl txid:etag="nc5152">
<name>A2</name>
<aces txid:etag="nc5152">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>22</port>
</source-port>
</tcp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>
¶
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>
<aces txid:etag="nc4711">
<ace txid:etag="nc4711">
<name>R1</name>
<matches>
<ipv4>
<protocol>17</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
<acl txid:etag="nc5152">
<name>A2</name>
<aces txid:etag="nc5152">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>22</port>
</source-port>
</tcp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>
</data>
</rpc>
¶
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>17</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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>
</data>
</rpc>
¶
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>
¶
Or, if a configuration change has taken place under /acls since the client was last updated, the server's response may 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="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>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<ipv4>
<source-port>
<port>22</port>
</source-port>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc6614">
<name>R9</name>
<matches>
<ipv4>
<source-port>
<port>830</port>
</source-port>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc>
¶
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.¶
<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>
¶
A client that wishes to update the ace R1 protocol to tcp might send:¶
<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>6</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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"
txid:etag="nc7688">
<acl txid:etag="nc7688">
<name>A1</name>
<aces txid:etag="nc7688">
<ace txid:etag="nc7688">
<name>R1</name>
<matches>
<ipv4>
<protocol>6</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
<acl txid:etag="nc6614">
<name>A2</name>
<aces txid:etag="nc6614">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc5152">
<name>R8</name>
<matches>
<udp>
<source-port>
<port>22</port>
</source-port>
</udp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc6614">
<name>R9</name>
<matches>
<tcp>
<source-port>
<port>830</port>
</source-port>
</tcp>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
</acls>
</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>6</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
<acl txid:etag="cli2222">
<name>A2</name>
<aces txid:etag="cli2222">
<ace txid:etag="nc4711">
<name>R7</name>
<matches>
<ipv4>
<dscp>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
</aces>
</acl>
</acls>
</data>
</rpc>
¶
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:¶
<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>10</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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:¶
<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>
¶
Let's assume that a get-config towards the running datastore currently contains the following data and txid values:¶
<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>17</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc2219">
<name>R2</name>
<matches>
<ipv4>
<dscp>21</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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 (17) to tcp (6), and then executes a get-config with the txid-request attribute "?" set on the acl A1, the server might respond:¶
<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>6</protocol>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</ace>
<ace txid:etag="nc2219">
<name>R2</name>
<matches>
<ipv4>
<dscp>21</dscp>
</ipv4>
</matches>
<actions>
<forwarding xmlns:acl=
"urn:ietf:params:xml:ns:yang:ietf-access-control-list">
acl:accept
<forwarding>
</actions>
</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.¶
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>
¶
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:¶
<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:on-change/>
<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>
¶
A server might send a subscription update like this:¶
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"
xmlns:ietf-netconf-txid-yp=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid-yang-push">
<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>
<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>
<ietf-netconf-txid-yp:etag-value>
nc8008
</ietf-netconf-txid-yp:etag-value>
</yang-patch>
</datastore-changes>
</push-change-update>
</notification>
¶
The following example is taken from section 5 of [RFC9144]. It compares the difference between the operational and intended datastores for a subtree under "interfaces".¶
In this version of the example, the client requests that txid values, in this case etag-values, are annotated to the result.¶
<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<compare xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"
xmlns:ietf-netconf-txid-nmda-compare=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid-nmda-compare">
<source>ds:operational</source>
<target>ds:intended</target>
<report-origin/>
<ietf-netconf-txid-nmda-compare:with-etag>
true
</ietf-netconf-txid-nmda-compare:with-etag>
<xpath-filter
xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces">
/if:interfaces
</xpath-filter>
</compare>
</rpc>
¶
RPC reply when a difference is detected:¶
<rpc-reply
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
message-id="101">
<differences
xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
xmlns:ietf-netconf-txid-nmda-compare=
"urn:ietf:params:xml:ns:yang:ietf-netconf-txid-nmda-compare">
<yang-patch>
<patch-id>interface status</patch-id>
<comment>
diff between operational (source) and intended (target),
with txid values taken from intended.
</comment>
<edit>
<edit-id>1</edit-id>
<operation>replace</operation>
<target>/ietf-interfaces:interface=eth0/enabled</target>
<value>
<if:enabled>false</if:enabled>
</value>
<source-value>
<if:enabled or:origin="or:learned">true</if:enabled>
</source-value>
<ietf-netconf-txid-nmda-compare:etag-value>
4004
</ietf-netconf-txid-nmda-compare:etag-value>
</edit>
<edit>
<edit-id>2</edit-id>
<operation>create</operation>
<target>/ietf-interfaces:interface=eth0/description</target>
<value>
<if:description>ip interface</if:description>
</value>
<ietf-netconf-txid-nmda-compare:etag-value>
8008
</ietf-netconf-txid-nmda-compare:etag-value>
</edit>
</yang-patch>
</differences>
</rpc-reply>
¶
The same response in RESTCONF (using JSON format):¶
HTTP/1.1 200 OK
Date: Thu, 24 Jan 2019 20:56:30 GMT
Server: example-server
Content-Type: application/yang-data+json
{ "ietf-nmda-compare:output" : {
"differences" : {
"ietf-yang-patch:yang-patch" : {
"patch-id" : "interface status",
"comment" : "diff between intended (source) and operational",
"edit" : [
{
"edit-id" : "1",
"operation" : "replace",
"target" : "/ietf-interfaces:interface=eth0/enabled",
"value" : {
"ietf-interfaces:interface/enabled" : "false"
},
"source-value" : {
"ietf-interfaces:interface/enabled" : "true",
"@ietf-interfaces:interface/enabled" : {
"ietf-origin:origin" : "ietf-origin:learned"
}
},
"ietf-netconf-txid-nmda-compare:etag-value": "4004"
},
{
"edit-id" : "2",
"operation" : "create",
"target" : "/ietf-interfaces:interface=eth0/description",
"value" : {
"ietf-interface:interface/description" : "ip interface"
},
"ietf-netconf-txid-nmda-compare:etag-value": "8008"
}
]
}
}
}
}
¶
<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;
}
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";
}
feature txid-last-modified {
description "Servers implementing this module MUST support the
etag txid mechanism. Servers MAY also support the
last-modified txid mechanism. Support is shown by announcing
this feature.";
}
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;
description
"Indicates whether the client requests the server to include
a txid:etag txid attribute when the configuration has
changed.";
}
leaf with-last-modified {
if-feature txid-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.";
}
grouping txid-value-grouping {
leaf etag-value {
type etag-t;
description
"Indicates server's txid value for a YANG node.";
}
leaf last-modified-value {
if-feature txid-last-modified;
type last-modified-t;
description
"Indicates server's txid value for a YANG node.";
}
description
"Grouping for txid mechanisms, to be augmented into
output of rpcs that return txid metadata for 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 {
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 {
if-feature txid-last-modified;
type last-modified-t;
description
"Indicates server's txid value of the last-modified
attribute for one mismatching element.";
}
}
}
}
<CODE ENDS>¶
<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-yang-push {
prefix yp;
reference
"RFC 8641: Subscriptions to YANG Datastores";
}
import ietf-yang-patch {
prefix ypatch;
reference
"RFC 8072: YANG Patch Media Type";
}
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/>
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;
}
augment "/sn:subscriptions/sn:subscription" {
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses ietf-netconf-txid:txid-grouping;
}
augment "/yp:push-change-update/yp:datastore-changes/" +
"yp:yang-patch" {
description
"This augmentation makes it possible for servers to return
txid-values.";
uses ietf-netconf-txid:txid-value-grouping;
}
}
<CODE ENDS>¶
<CODE BEGINS>
module ietf-netconf-txid-nmda-compare {
yang-version 1.1;
namespace
'urn:ietf:params:xml:ns:yang:ietf-netconf-txid-nmda-compare';
prefix ietf-netconf-txid-nmda-compare;
import ietf-nmda-compare {
prefix cmp;
reference
"RFC 9144: Comparison of Network Management Datastore
Architecture (NMDA) Datastores";
}
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/>
WG List: <netconf@ietf.org>
Author: Jan Lindblad
<mailto:jlindbla@cisco.com>";
description
"NETCONF Transaction ID aware operations for NMDA Compare.
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 2023-05-01 {
description
"Initial revision";
reference
"RFC XXXX: Xxxxxxxxx";
}
augment "/cmp:compare/cmp:input" {
description
"This augmentation makes it possible for clients to request
txids to be returned.";
uses ietf-netconf-txid:txid-grouping;
}
augment "/cmp:compare/cmp:output/cmp:compare-response/" +
"cmp:differences/cmp:differences/cmp:yang-patch/cmp:edit" {
description
"This augmentation makes it possible for servers to return
txid-values.";
container most-recent {
uses ietf-netconf-txid:txid-value-grouping;
}
}
}
<CODE ENDS>¶
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.¶
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.¶
It will also be possible for clients to deduce that a configuration 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.¶
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 four 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 URI: urn:ietf:params:xml:ns:yang:ietf-netconf-txid-nmda-compare Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URIs are XML namespaces.¶
This document registers three 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¶
name: ietf-netconf-txid-yp prefix: ietf-netconf-txid-yp namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-txid-yang-push RFC: XXXX¶
and¶
name: ietf-netconf-txid-nmda-compare
prefix: ietf-netconf-txid-nmda-compare
namespace:
urn:ietf:params:xml:ns:yang:ietf-netconf-txid-nmda-compare
RFC: XXXX
¶
The author wishes to thank Benoît Claise for making this work happen, and the following individuals, who all provided helpful comments: Per Andersson, James Cumming, Kent Watsen, Andy Bierman, Robert Wilton, Qiufang Ma, Jason Sterne and Robert Varga.¶