| NETCONF | A. Clemm |
| Internet-Draft | Huawei |
| Intended status: Standards Track | E. Voit |
| Expires: April 25, 2019 | Cisco Systems |
| A. Gonzalez Prieto | |
| VMware | |
| A. Tripathy | |
| E. Nilsen-Nygaard | |
| Cisco Systems | |
| A. Bierman | |
| YumaWorks | |
| B. Lengyel | |
| Ericsson | |
| October 22, 2018 |
Subscription to YANG Datastores
draft-ietf-netconf-yang-push-20
Via the mechanism described in this document, subscriber applications may request a continuous, customized stream of updates from a YANG datastore. Providing such visibility into updates enables new capabilities based on the remote mirroring and monitoring of configuration and operational state.
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 April 25, 2019.
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
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This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English.
Traditional approaches to providing visibility into managed entities from remote have been built on polling. With polling, data is periodically requested and retrieved by a client from a server to stay up-to-date. However, there are issues associated with polling-based management:
A more effective alternative to polling is for an application to receive automatic and continuous updates from a targeted subset of a datastore. Accordingly, there is a need for a service that allows applications to subscribe to updates from a datastore and that enables the server (also referred to as publisher) to push and in effect stream those updates. The requirements for such a service have been documented in [RFC7923].
This document defines a corresponding solution that is built on top of "Custom Subscription to Event Streams" [I-D.draft-ietf-netconf-subscribed-notifications]. Supplementing that work are YANG data model augmentations, extended RPCs, and new datastore specific update notifications. Transport options for [I-D.draft-ietf-netconf-subscribed-notifications] will work seamlessly with this solution.
This document uses the terminology defined in [RFC7950], [RFC8341], [RFC8342], and [I-D.draft-ietf-netconf-subscribed-notifications]. In addition, the following terms are introduced:
This document specifies a solution that provides a subscription service for updates from a datastore. This solution supports dynamic as well as configured subscriptions to updates of datastore nodes. Subscriptions specify when notification messages (also referred to as "push updates") should be sent and what data to include in update records. Datastore node updates are subsequently pushed from the publisher to the receiver per the terms of the subscription.
YANG-push subscriptions are defined using a YANG data model. This model enhances the subscription model defined in [I-D.draft-ietf-netconf-subscribed-notifications] with capabilities that allow subscribers to subscribe to datastore node updates, specifically to specify the update triggers defining when to generate update records as well as what to include in an update record. Key enhancements include:
A dynamic subscription request SHOULD be declined if a publisher's assessment is that it may be unable to provide update records meeting the terms of an "establish-subscription" or "modify-subscription" RPC request. In this case, a subscriber may quickly follow up with a new RPC request using different parameters.
Random guessing of different parameters by a subscriber is to be discouraged. Therefore, in order to minimize the number of subscription iterations between subscriber and publisher, a dynamic subscription supports a simple negotiation between subscribers and publishers for subscription parameters. This negotiation is in the form of supplemental information which should be inserted within error responses to a failed RPC request. This returned error response information, when considered, should increase the likelihood of success for subsequent RPC requests. Such hints include suggested periodic time intervals, acceptable dampening periods, and size estimates for the number or objects which would be returned from a proposed selection filter. However, there are no guarantees that subsequent requests which consider these hints will be accepted.
On-change subscriptions allow receivers to receive updates whenever changes to targeted objects occur. As such, on-change subscriptions are particularly effective for data that changes infrequently, yet for which applications need to be quickly notified whenever a change does occur with minimal delay.
On-change subscriptions tend to be more difficult to implement than periodic subscriptions. Accordingly, on-change subscriptions may not be supported by all implementations or for every object.
Whether or not to accept or reject on-change subscription requests when the scope of the subscription contains objects for which on-change is not supported is up to the publisher implementation. A publisher MAY accept an on-change subscription even when the scope of the subscription contains objects for which on-change is not supported. In that case, updates are sent only for those objects within the scope that do support on-change updates, whereas other objects are excluded from update records, even if their values change. In order for a subscriber to determine whether objects support on-change subscriptions, objects are marked accordingly on a publisher. Accordingly, when subscribing, it is the responsibility of the subscriber to ensure it is aware of which objects support on-change and which do not. For more on how objects are so marked, see Section 3.10.
Alternatively, a publisher MAY decide to simply reject an on-change subscription in case the scope of the subscription contains objects for which on-change is not supported. In case of a configured subscription, the publisher MAY suspend the subscription.
To avoid flooding receivers with repeated updates for subscriptions containing fast-changing objects, or objects with oscillating values, an on-change subscription allows for the definition of a dampening period. Once an update record for a given object is generated, no other updates for this particular subscription will be created until the end of the dampening period. Values sent at the end of the dampening period are the values that are current at the end of the dampening period of all changed objects. Changed objects include those which were deleted or newly created during that dampening period. If an object has returned to its original value (or even has been created and then deleted) during the dampening-period, that value (and not the interim change) will still be sent. This will indicate churn is occurring on that object.
On-change subscriptions can be refined to let users subscribe only to certain types of changes. For example, a subscriber might only want object creations and deletions, but not modifications of object values.
Putting it all together, following is the conceptual process for creating an update record as part of an on-change subscription:
Note: In cases where a subscriber wants to have separate dampening periods for different objects, the subscriber has the option to create multiple subscriptions with different selection filters.
A subscription to updates from a datastore is intended to obviate the need for polling. However, in order to do so, it is critical that subscribers can rely on the subscription and have confidence that they will indeed receive the subscribed updates without having to worry about updates being silently dropped. In other words, a subscription constitutes a promise on the side of the publisher to provide the receivers with updates per the terms of the subscription.
Now, there are many reasons why a publisher may at some point no longer be able to fulfill the terms of the subscription, even if the subscription had been entered into with good faith. For example, the volume of datastore nodes may be larger than anticipated, the interval may prove too short to send full updates in rapid succession, or an internal problem may prevent objects from being collected. For this reason, the solution that is defined in this document mandates that a publisher notifies receivers immediately and reliably whenever it encounters a situation in which it is unable to keep the terms of the subscription, and provides the publisher with the option to suspend the subscription in such a case. This includes indicating the fact that an update is incomplete as part of a push-update or push-change-update notification, as well as emitting a subscription-suspended notification as applicable. This is described further in Section 3.11.1.
A publisher SHOULD reject a request for a subscription if it is unlikely that the publisher will be able to fulfill the terms of that subscription request. In such cases, it is preferable to have a subscriber request a less resource intensive subscription than to deal with frequently degraded behavior.
In a periodic subscription, the data included as part of an update record corresponds to data that could have been read using a retrieval operation.
In an on-change subscription, update records need to indicate not only values of changed datastore nodes but also the types of changes that occurred since the last update. Therefore, encoding rules for data in on-change updates will generally follow YANG-patch operation as specified in [RFC8072]. The YANG-patch will describe what needs to be applied to the earlier state reported by the preceding update, to result in the now-current state. Note that contrary to [RFC8072], objects encapsulated are not restricted to only configuration objects.
A publisher indicates the type of change to a datastore node using the different YANG patch operations: the "create" operation is used for newly created objects (except entries in a user-ordered list), the "delete" operation is used for deleted objects (including in user-ordered lists), the "replace" operation is used when only the object value changes, the "insert" operation is used when a new entry is inserted in a list, and the "move" operation is used when an existing entry in a user-ordered list is moved.
However, a patch must be able to do more than just describe the delta from the previous state to the current state. As per Section 3.3, it must also be able to identify whether transient changes have occurred on an object during a dampening period. To support this, it is valid to encode a YANG patch operation so that its application would result in no change between the previous and current state. This indicates that some churn has occurred on the object. An example of this would be a patch that indicates a "create" operation for a datastore node where the receiver believes one already exists, or a "replace" operation which replaces a previous value with the same value. Note that this means that the "create" and "delete" errors described in [RFC8072] section 2.5 are not errors, and are valid operations with YANG-Push.
A subscription must specify both the selection filters and the datastore against which these selection filters will be applied. This information is used to choose and subsequently push data from the publisher's datastore to the receivers.
Only a single selection filter can be applied to a subscription at a time. An RPC request proposing a new selection filter replaces any existing filter. The following selection filter types are included in the yang-push data model, and may be applied against a datastore:
These filters are intended to be used as selectors that define which objects are within the scope of a subscription. A publisher MUST support at least one type of selection filter.
XPath itself provides powerful filtering constructs and care must be used in filter definition. Consider an XPath filter which only passes a datastore node when an interface is up. It is up to the receiver to understand implications of the presence or absence of objects in each update.
When the set of selection filtering criteria is applied for a periodic subscription, then they are applied whenever a periodic update record is constructed, and only datastore nodes that pass the filter and to which a receiver has access are provided to that receiver. If the same filtering criteria is applied to an on-change subscription, only the subset of those datastore nodes supporting on-change is provided. A datastore node which doesn't support on-change is never sent as part of an on-change subscription's "push-update" or "push-change-update" (see Section 3.7).
Contrary to traditional data retrieval requests, datastore subscription enables an unbounded series of update records to be streamed over time. Two generic YANG notifications for update records have been defined for this: "push-update" and "push-change-update".
A "push-update" notification defines a complete, filtered update of the datastore per the terms of a subscription. This type of YANG notification is used for continuous updates of periodic subscriptions. A "push-update" notification can also be used for the on-change subscriptions in two cases. First, it MUST be used as the initial "push-update" if there is a need to synchronize the receiver at the start of a new subscription. It also MAY be sent if the publisher later chooses to resync an on-change subscription. The "push-update" update record contains an instantiated datastore subtree with all of the subscribed contents. The content of the update record is equivalent to the contents that would be obtained had the same data been explicitly retrieved using a datastore retrieval operation using the same transport with the same filters applied.
A "push-change-update" notification is the most common type of update for on-change subscriptions. The update record in this case contains the set of changes that datastore nodes have undergone since the last notification message. In other words, this indicates which datastore nodes have been created, deleted, or have had changes to their values. In cases where multiple changes have occurred over the course of a dampening period and the object has not been deleted, the object's most current value is reported. (In other words, for each object, only one change is reported, not its entire history. Doing so would defeat the purpose of the dampening period.)
"Push-update" and "push-change-update" are encoded and placed within notification messages, and ultimately queued for egress over the specified transport.
The following is an example of a notification message for a subscription tracking the operational status of a single Ethernet interface (per [RFC8343]). This notification message is encoded XML over NETCONF as per [I-D.draft-ietf-netconf-netconf-event-notifications].
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2017-10-25T08:00:11.22Z</eventTime>
<push-update xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<id>1011</id>
<datastore-contents>
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
<interface>
<name>eth0</name>
<oper-status>up</oper-status>
</interface>
</interfaces>
</datastore-contents>
</push-update>
</notification>
Figure 1: Push example
The following is an example of an on-change notification message for the same subscription.
<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
<eventTime>2017-10-25T08:22:33.44Z</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>replace</operation>
<target>/ietf-interfaces:interfaces</target>
<value>
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
<interface>
<name>eth0</name>
<oper-status>down</oper-status>
</interface>
</interfaces>
</value>
</edit>
</yang-patch>
</datastore-changes>
</push-change-update>
</notification>
Figure 2: Push example for on change
Of note in the above example is the 'patch-id' with a value of '0'. Per [RFC8072], the 'patch-id' is an arbitrary string. With YANG Push, the publisher SHOULD put into the 'patch-id' a counter starting at '0' which increments with every 'push-change-update' generated for a subscription. If used as a counter, this counter MUST be reset to '0' anytime a resynchronization occurs (i.e., with the sending of a 'push-update'). Also if used as a counter, the counter MUST be reset to '0' after passing a maximum value of '4294967295' (i.e. maximum value that can be represented using uint32 data type). Such a mechanism allows easy identification of lost or out-of-sequence update records.
The RPCs defined within [I-D.draft-ietf-netconf-subscribed-notifications] have been enhanced to support datastore subscription negotiation. Also, new error codes have been added that are able to indicate why a datastore subscription attempt has failed, along with new yang-data that MAY be used to include details on input parameters that might result in a successful subsequent RPC invocation.
The establishment or modification of a datastore subscription can be rejected for multiple reasons. This includes a too large subtree request, or the inability of the publisher to push update records as frequently as requested. In such cases, no subscription is established. Instead, the subscription-result with the failure reason is returned as part of the RPC response. As part of this response, a set of alternative subscription parameters MAY be returned that would likely have resulted in acceptance of the subscription request. The subscriber may consider these as part of future subscription attempts.
In the case of a rejected request for an establishment of a datastore subscription, if there are hints, the hints SHOULD be transported within a yang-data "establish-subscription-datastore-error-info" container inserted into the RPC error response, in lieu of the "establish-subscription-stream-error-info" that is inserted in case of a stream subscription.
Below is a tree diagram for "establish-subscription-datastore-error-info". All tree diagrams used in this document follow the notation defined in [RFC8340]
yang-data establish-subscription-datastore-error-info
+--ro establish-subscription-datastore-error-info
+--ro reason? identityref
+--ro period-hint? yang:timeticks
+--ro filter-failure-hint? string
+--ro object-count-estimate? uint32
+--ro object-count-limit? uint32
+--ro kilobytes-estimate? uint32
+--ro kilobytes-limit? uint32
Figure 3: Tree diagram for establish-subscription-datastore-error-info
Similarly, in the case of a rejected request for modification of a datastore subscription, if there are hints, the hints SHOULD be transported within a yang-data "modify-subscription-datastore-error-info" container inserted into the RPC error response, in lieu of the "modify-subscription-stream-error-info" that is inserted in case of a stream subscription.
Below is a tree diagram for "modify-subscription-datastore-error-info".
yang-data modify-subscription-datastore-error-info
+--ro modify-subscription-datasore-error-info
+--ro reason? identityref
+--ro period-hint? yang:timeticks
+--ro filter-failure-hint? string
+--ro object-count-estimate? uint32
+--ro object-count-limit? uint32
+--ro kilobytes-estimate? uint32
+--ro kilobytes-limit? uint32
Figure 4: Tree diagram for modify-subscription-datastore-error-info
A receiver of subscription data MUST only be sent updates for which it has proper authorization. A publisher MUST ensure that no non-authorized data is included in push updates. To do so, it needs to apply all corresponding checks applicable at the time of a specific pushed update and if necessary silently remove any non-authorized data from datastore subtrees. This enables YANG data pushed based on subscriptions to be authorized equivalently to a regular data retrieval (get) operation.
Each "push-update" and "push-change-update" MUST have access control applied, as is depicted in the following diagram. This includes validating that read access is permitted for any new objects selected since the last notification message was sent to a particular receiver. To accomplish this, implementations SHOULD support the conceptual authorization model of [RFC8341], specifically section 3.2.4.
+-----------------+ +--------------------+
push-update or --> | datastore node | yes | add datastore node |
push-change-update | access allowed? | ---> | to update record |
+-----------------+ +--------------------+
Figure 5: Updated [RFC8341] access control for push updates
A publisher MUST allow for the possibility that a subscription's selection filter references non-existent data or data that a receiver is not allowed to access. Such support permits a receiver the ability to monitor the entire lifecyle of some datastore tree without needing to explicitly enumerate every individual datastore node. If, after access control has been applied, there are no objects remaining in an update record, then (in case of a periodic subscription) only a single empty "push-update" notification MUST be sent. Empty "push-change-update" messages (in case of an on-change subscription) MUST NOT be sent. This is required to ensure that clients cannot surreptitiously monitor objects that they do not have access to via carefully crafted selection filters. By the same token, changes to objects that are filtered MUST NOT affect any dampening intervals.
A publisher MAY choose to reject an establish-subscription request which selects non-existent data or data that a receiver is not allowed to access. As reason, the error identity "unchanging-selection" SHOULD be returned. In addition, a publisher MAY choose to terminate a dynamic subscription or suspend a configured receiver when the authorization privileges of a receiver change, or the access controls for subscribed objects change. In that case, the publisher SHOULD include the error identity "unchanging-selection" as reason when sending the "subscription-terminated" respectively "subscription-suspended" notification. Such a capability enables the publisher to avoid having to support continuous and total filtering of a subscription's content for every update record. It also reduces the possibility of leakage of access-controlled objects.
If read access into previously accessible nodes has been lost due to a receiver permissions change, this SHOULD be reported as a patch "delete" operation for on-change subscriptions. If not capable of handling such receiver permission changes with such a "delete", publisher implementations MUST force dynamic subscription re-establishment or configured subscription re-initialization so that appropriate filtering is installed.
In some cases, a publisher supporting on-change notifications may not be able to push on-change updates for some object types. Reasons for this might be that the value of the datastore node changes frequently (e.g., [RFC8343]'s in-octets counter), that small object changes are frequent and meaningless (e.g., a temperature gauge changing 0.1 degrees), or that the implementation is not capable of on-change notification for a particular object.
In those cases, it will be important for client applications to have a way to identify for which objects on-change notifications are supported and for which ones they are not supported. Otherwise client applications will have no way of knowing whether they can indeed rely on their on-change subscription to provide them with the change updates that they are interested in. In other words, if implementations do not provide a solution and do not support comprehensive on-change notifiability, clients of those implementations will have no way of knowing what their on-change subscription actually covers.
Implementations are therefore strongly advised to provide a solution to this problem. It is expected that such a solution will be standardized at some point in the future. In the meantime and until this occurs, implementations SHOULD provide their own solution.
Particularly in the case of on-change updates, it is important that these updates do not get lost. In case the loss of an update is unavoidable, it is critical that the receiver is notified accordingly.
Update records for a single subscription MUST NOT be resequenced prior to transport.
It is conceivable that under certain circumstances, a publisher will recognize that it is unable to include within an update record the full set of objects desired per the terms of a subscription. In this case, the publisher MUST act as follows.
Note: It is perfectly acceptable to have a series of "push-change-update" notifications (and even "push update" notifications) serially queued at the transport layer awaiting transmission. It is not required for the publisher to merge pending update records sent at the same time.
It is far preferable to decline a subscription request than to accept such a request when it cannot be met.
Whether or not a subscription can be supported will be determined by a combination of several factors such as the subscription update trigger (on-change or periodic), the period in which to report changes (one second periods will consume more resources than one hour periods), the amount of data in the datastore subtree that is being subscribed to, and the number and combination of other subscriptions that are concurrently being serviced.
The YANG data model for datastore push subscriptions is depicted in the following figure. The tree diagram follows the notation defined in [RFC8340]. New schema objects defined here (i.e., beyond those from [I-D.draft-ietf-netconf-subscribed-notifications]) are identified with "yp". For the reader's convenience, in order to compact the tree representation, some nodes that are defined in ietf-subscribed-notifications and that are not essential to the understanding of the data model defined here have been removed. This is indicated by "..." in the diagram where applicable.
module: ietf-subscribed-notifications
...
+--rw filters
| ...
| +--rw yp:selection-filter* [filter-id]
| +--rw yp:filter-id string
| +--rw (yp:filter-spec)?
| +--:(yp:datastore-subtree-filter)
| | +--rw yp:datastore-subtree-filter? <anydata>
| | {sn:subtree}?
| +--:(yp:datastore-xpath-filter)
| +--rw yp:datastore-xpath-filter? yang:xpath1.0
| {sn:xpath}?
+--rw subscriptions
+--rw subscription* [id]
| ...
+--rw (target)
| +--:(stream)
| | ...
| +--:(yp:datastore)
| +--rw yp:datastore identityref
| +--rw (yp:selection-filter)?
| +--:(yp:by-reference)
| | +--rw yp:selection-filter-ref
| | selection-filter-ref
| +--:(yp:within-subscription)
| +--rw (yp:filter-spec)?
| +--:(yp:datastore-subtree-filter)
| | +--rw yp:datastore-subtree-filter?
| | <anydata> {sn:subtree}?
| +--:(yp:datastore-xpath-filter)
| +--rw yp:datastore-xpath-filter?
| yang:xpath1.0 {sn:xpath}?
| ...
+--rw (yp:update-trigger)
+--:(yp:periodic)
| +--rw yp:periodic!
| +--rw yp:period yang:timeticks
| +--rw yp:anchor-time? yang:date-and-time
+--:(yp:on-change) {on-change}?
+--rw yp:on-change!
+--rw yp:dampening-period? yang:timeticks
+--rw yp:sync-on-start? boolean
+--rw yp:excluded-change* change-type
rpcs:
+---x establish-subscription
| +---w input
| | ...
| | +---w (target)
| | | +--:(stream)
| | | | ...
| | | +--:(yp:datastore)
| | | +---w yp:datastore identityref
| | | +---w (yp:selection-filter)?
| | | +--:(yp:by-reference)
| | | | +---w yp:selection-filter-ref
| | | | selection-filter-ref
| | | +--:(yp:within-subscription)
| | | +---w (yp:filter-spec)?
| | | +--:(yp:datastore-subtree-filter)
| | | | +---w yp:datastore-subtree-filter?
| | | | <anydata> {sn:subtree}?
| | | +--:(yp:datastore-xpath-filter)
| | | +---w yp:datastore-xpath-filter?
| | | yang:xpath1.0 {sn:xpath}?
| | | ...
| | +---w (yp:update-trigger)
| | +--:(yp:periodic)
| | | +---w yp:periodic!
| | | +---w yp:period yang:timeticks
| | | +---w yp:anchor-time? yang:date-and-time
| | +--:(yp:on-change) {on-change}?
| | +---w yp:on-change!
| | +---w yp:dampening-period? yang:timeticks
| | +---w yp:sync-on-start? boolean
| | +---w yp:excluded-change* change-type
| +--ro output
| +--ro id subscription-id
| +--ro replay-start-time-revision? yang:date-and-time
| {replay}?
+---x modify-subscription
| +---w input
| ...
| +---w (target)
| | ...
| | +--:(yp:datastore)
| | +---w (yp:selection-filter)?
| | +--:(yp:by-reference)
| | | +---w yp:selection-filter-ref
| | | selection-filter-ref
| | +--:(yp:within-subscription)
| | +---w (yp:filter-spec)?
| | +--:(yp:datastore-subtree-filter)
| | | +---w yp:datastore-subtree-filter?
| | | <anydata> {sn:subtree}?
| | +--:(yp:datastore-xpath-filter)
| | +---w yp:datastore-xpath-filter?
| | yang:xpath1.0 {sn:xpath}?
| | ...
| +---w (yp:update-trigger)
| +--:(yp:periodic)
| | +---w yp:periodic!
| | +---w yp:period yang:timeticks
| | +---w yp:anchor-time? yang:date-and-time
| +--:(yp:on-change) {on-change}?
| +---w yp:on-change!
| +---w yp:dampening-period? yang:timeticks
+---x delete-subscription
| ...
+---x kill-subscription
...
yang-data (for placement into rpc error responses)
...
notifications:
+---n replay-completed {replay}?
| ...
+---n subscription-completed
| ...
+---n subscription-started {configured}?
| | ...
| +--ro (target)
| | ...
| | +--:(yp:datastore)
| | +--ro yp:datastore identityref
| | +--ro (yp:selection-filter)?
| | +--:(yp:by-reference)
| | | +--ro yp:selection-filter-ref
| | | selection-filter-ref
| | +--:(yp:within-subscription)
| | +--ro (yp:filter-spec)?
| | +--:(yp:datastore-subtree-filter)
| | | +--ro yp:datastore-subtree-filter?
| | | <anydata> {sn:subtree}?
| | +--:(yp:datastore-xpath-filter)
| | +--ro yp:datastore-xpath-filter?
| | yang:xpath1.0 {sn:xpath}?
| ...
| +--ro (yp:update-trigger)
| +--:(yp:periodic)
| | +--ro yp:periodic!
| | +--ro yp:period yang:timeticks
| | +--ro yp:anchor-time? yang:date-and-time
| +--:(yp:on-change) {on-change}?
| +--ro yp:on-change!
| +--ro yp:dampening-period? yang:timeticks
| +--ro yp:sync-on-start? boolean
| +--ro yp:excluded-change* change-type
+---n subscription-resumed
| ...
+---n subscription-modified
| ...
| +--ro (target)
| | | ...
| | +--:(yp:datastore)
| | +--ro yp:datastore identityref
| | +--ro (yp:selection-filter)?
| | +--:(yp:by-reference)
| | | +--ro yp:selection-filter-ref
| | | selection-filter-ref
| | +--:(yp:within-subscription)
| | +--ro (yp:filter-spec)?
| | +--:(yp:datastore-subtree-filter)
| | | +--ro yp:datastore-subtree-filter?
| | | <anydata> {sn:subtree}?
| | +--:(yp:datastore-xpath-filter)
| | +--ro yp:datastore-xpath-filter?
| | yang:xpath1.0 {sn:xpath}?
| ...
| +--ro (yp:update-trigger)?
| +--:(yp:periodic)
| | +--ro yp:periodic!
| | +--ro yp:period yang:timeticks
| | +--ro yp:anchor-time? yang:date-and-time
| +--:(yp:on-change) {on-change}?
| +--ro yp:on-change!
| +--ro yp:dampening-period? yang:timeticks
| +--ro yp:sync-on-start? boolean
| +--ro yp:excluded-change* change-type
+---n subscription-terminated
| ...
+---n subscription-suspended
...
module: ietf-yang-push
rpcs:
+---x resync-subscription {on-change}?
+---w input
+---w id sn:subscription-id
yang-data: (for placement into rpc error responses)
+-- resync-subscription-error
| +--ro reason? identityref
| +--ro period-hint? timeticks
| +--ro filter-failure-hint? string
| +--ro object-count-estimate? uint32
| +--ro object-count-limit? uint32
| +--ro kilobytes-estimate? uint32
| +--ro kilobytes-limit? uint32
+-- establish-subscription-error-datastore
| +--ro reason? identityref
| +--ro period-hint? timeticks
| +--ro filter-failure-hint? string
| +--ro object-count-estimate? uint32
| +--ro object-count-limit? uint32
| +--ro kilobytes-estimate? uint32
| +--ro kilobytes-limit? uint32
+-- modify-subscription-error-datastore
+--ro reason? identityref
+--ro period-hint? timeticks
+--ro filter-failure-hint? string
+--ro object-count-estimate? uint32
+--ro object-count-limit? uint32
+--ro kilobytes-estimate? uint32
+--ro kilobytes-limit? uint32
notifications:
+---n push-update
| +--ro id? sn:subscription-id
| +--ro datastore-contents? <anydata>
| +--ro incomplete-update? empty
+---n push-change-update {on-change}?
+--ro id? sn:subscription-id
+--ro datastore-changes?
| +--ro yang-patch
| +--ro patch-id string
| +--ro ypatch:comment? string
| +--ro ypatch:edit* [edit-id]
| +--ro ypatch:edit-id string
| +--ro ypatch:operation enumeration
| +--ro ypatch:target target-resource-offset
| +--ro ypatch:point? target-resource-offset
| +--ro ypatch:where? enumeration
| +--ro ypatch:value?
+--ro incomplete-update? empty
Figure 6: Model structure
Selected components of the model are summarized below.
Both configured and dynamic subscriptions are represented within the list "subscription". New parameters extending the basic subscription data model in [I-D.draft-ietf-netconf-subscribed-notifications] include:
Subscription state notifications and mechanism are reused from [I-D.draft-ietf-netconf-subscribed-notifications]. Notifications "subscription-started" and "subscription-modified" have been augmented to include the datastore specific objects.
Along with the subscribed content, there are other objects which might be part of a "push-update" or "push-change-update" notification.
An "id" (that identifies the subscription) MUST be transported along with the subscribed contents. This allows a receiver to differentiate which subscription resulted in a particular update record.
A "time-of-update" which represents the time an update record snapshot was generated. A receiver MAY assume that at this point in time a publisher's objects have the values that were pushed.
An "incomplete-update" leaf. This leaf indicates that not all changes which have occurred since the last update are actually included with this update. In other words, the publisher has failed to fulfill its full subscription obligations. (For example a datastore was unable to provide the full set of datastore nodes to a publisher process.) To facilitate re-synchronization of on-change subscriptions, a publisher MAY subsequently send a "push-update" containing a full selection snapshot of subscribed data.
YANG-Push subscriptions are established, modified, and deleted using RPCs augmented from [I-D.draft-ietf-netconf-subscribed-notifications].
The subscriber sends an establish-subscription RPC with the parameters in section 3.1. An example might look like:
<netconf:rpc message-id="101"
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">
<yp:datastore xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex="http://example.com/sample-data/1.0">
/ex:foo
</yp:datastore-xpath-filter>
<yp:periodic>
<yp:period>500</yp:period>
</yp:periodic>
</establish-subscription>
</netconf:rpc>
Figure 7: Establish-subscription RPC
A positive response includes the "id" of the accepted subscription. In that case a publisher may respond:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<id
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
52
</id>
</rpc-reply>
Figure 8: Establish-subscription positive RPC response
A subscription can be rejected for multiple reasons, including the lack of authorization to establish a subscription, no capacity to serve the subscription at the publisher, or the inability of the publisher to select datastore content at the requested cadence.
If a request is rejected because the publisher is not able to serve it, the publisher SHOULD include in the returned error hints which help a subscriber understand subscription parameters might have been accepted for the request. These hints would be included within the yang-data structure "establish-subscription-error-datastore". However even with these hints, there are no guarantee that subsequent requests will in fact be accepted.
The specific parameters to be returned as part of the RPC error response depend on the specific transport that is used to manage the subscription. For example, in the case of NETCONF [I-D.draft-ietf-netconf-netconf-event-notifications], when a subscription request is rejected, the NETCONF RPC reply would be expected to include an "rpc-error" element with the following elements:
For example, for the following request:
<netconf:rpc message-id="101"
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">
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex="http://example.com/sample-data/1.0">
/ex:foo
</yp:datastore-xpath-filter>
<yp:on-change>
<yp:dampening-period>100</yp:dampening-period>
</yp:on-change>
</establish-subscription>
</netconf:rpc>
Figure 9: Establish-subscription request example 2
a publisher that cannot serve on-change updates but periodic updates might return the following:
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<rpc-error>
<error-type>application</error-type>
<error-tag>operation-failed</error-tag>
<error-severity>error</error-severity>
<error-path>/yp:periodic/yp:period</error-path>
<error-info>
<yp:establish-subscription-error-datastore>
<yp:reason>yp:on-change-unsupported</yp:reason>
</yp:establish-subscription-error-datastore>
</error-info>
</rpc-error>
</rpc-reply>
Figure 10: Establish-subscription error response example 2
The subscriber MAY invoke the "modify-subscription" RPC for a subscription it previously established. The subscriber will include newly desired values in the "modify-subscription" RPC. Parameters not included MUST remain unmodified. Below is an example where a subscriber attempts to modify the period and datastore XPath filter of a subscription.
<netconf:rpc message-id="102"
xmlns:netconf="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">
<id>1011</id>
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex="http://example.com/sample-data/1.0">
/ex:bar
</yp:datastore-xpath-filter>
<yp:periodic>
<yp:period>250</yp:period>
</yp:periodic>
</modify-subscription>
</netconf:rpc>
Figure 11: Modify subscription request
The publisher MUST respond to the subscription modification request. If the request is rejected, the existing subscription is left unchanged, and the publisher MUST send an RPC error response. This response might have hints encapsulated within the yang-data structure "modify-subscription-error-datastore". A subscription MAY be modified multiple times.
The specific parameters to be returned in as part of the RPC error response depend on the specific transport that is used to manage the subscription. In the case of NETCONF [I-D.draft-ietf-netconf-netconf-event-notifications], when a subscription request is rejected, the NETCONF RPC reply MUST include an "rpc-error" element with the following elements:
A configured subscription cannot be modified using "modify-subscription" RPC. Instead, the configuration needs to be edited as needed.
To stop receiving updates from a subscription and effectively delete a subscription that had previously been established using an "establish-subscription" RPC, a subscriber can send a "delete-subscription" RPC, which takes as only input the subscription's "id". This RPC is unmodified from [I-D.draft-ietf-netconf-subscribed-notifications].
This RPC is supported only for on-change subscriptions previously established using an "establish-subscription" RPC. For example:
<netconf:rpc message-id="103"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<resync-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push"
xmlns:sn="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
<id>1011</id>
</resync-subscription>
</netconf:rpc>
Resync subscription
On receipt, a publisher must either accept the request and quickly follow with a "push-update", or send an appropriate error within an rpc error response. Within an error response, the publisher MAY include supplemental information about the reasons within the yang-data structure "resync-subscription-error".
To make subscription requests, the subscriber needs to know the YANG datastore schemas used by the publisher, which are available via the YANG Library module, ietf-yang-library.yang from [RFC7895]. The receiver is expected to know the YANG library information before starting a subscription.
The set of modules, revisions, features, and deviations can change at run-time (if supported by the publisher implementation). For this purpose, the YANG library provides a simple "yang-library-change" notification that informs the subscriber that the library has changed. In this case, a subscription may need to be updated to take the updates into account. The receiver may also need to be informed of module changes in order to process updates regarding datastore nodes from changed modules correctly.
<CODE BEGINS> file "ietf-yang-push@2018-10-22.yang"
module ietf-yang-push {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push";
prefix yp;
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-subscribed-notifications {
prefix sn;
reference
"draft-ietf-netconf-subscribed-notifications:
Customized Subscriptions to a Publisher's Event Streams
NOTE TO RFC Editor: Please replace above reference to
draft-ietf-netconf-subscribed-notifications with RFC number
when published (i.e. RFC xxxx).";
}
import ietf-datastores {
prefix ds;
reference
"RFC 8342: Network Management Datastore Architecture (NMDA)";
}
import ietf-restconf {
prefix rc;
reference
"RFC 8040: RESTCONF Protocol";
}
import ietf-yang-patch {
prefix ypatch;
reference
"RFC 8072: YANG Patch";
}
organization "IETF";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Editor: Alexander Clemm
<mailto:ludwig@clemm.org>
Editor: Eric Voit
<mailto:evoit@cisco.com>
Editor: Alberto Gonzalez Prieto
<mailto:agonzalezpri@vmware.com>
Editor: Ambika Prasad Tripathy
<mailto:ambtripa@cisco.com>
Editor: Einar Nilsen-Nygaard
<mailto:einarnn@cisco.com>
Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description
"This module contains YANG specifications for YANG push.
Copyright (c) 2018 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
draft-ietf-netconf-yang-push-20; see the RFC itself for full
legal notices.
NOTE TO RFC EDITOR: Please replace above reference to
draft-ietf-netconf-yang-push-20 with RFC number when published
(i.e. RFC xxxx).";
revision 2018-10-22 {
description
"Initial revision.
NOTE TO RFC EDITOR:
(1)Please replace the above revision date to
the date of RFC publication when published.
(2) Please replace the date in the file name
(ietf-yang-push@2018-10-22.yang) to the date of RFC
publication.
(3) Please replace the following reference to
draft-ietf-netconf-yang-push-20 with RFC number when
published (i.e. RFC xxxx).";
reference
"draft-ietf-netconf-yang-push-20";
}
/*
* FEATURES
*/
feature on-change {
description
"This feature indicates that on-change triggered
subscriptions are supported.";
}
/*
* IDENTITIES
*/
/* Error type identities for datastore subscription */
identity resync-subscription-error {
description
"Problem found while attempting to fulfill an
'resync-subscription' RPC request. ";
}
identity cant-exclude {
base sn:establish-subscription-error;
description
"Unable to remove the set of 'excluded-changes'. This means
the publisher is unable to restrict 'push-change-update's to
just the change types requested for this subscription.";
}
identity datastore-not-subscribable {
base sn:establish-subscription-error;
base sn:subscription-terminated-reason;
description
"This is not a subscribable datastore.";
}
identity no-such-subscription-resync {
base resync-subscription-error;
description
"Referenced subscription doesn't exist. This may be as a
result of a non-existent subscription ID, an ID which
belongs to another subscriber, or an ID for configured
subscription.";
}
identity on-change-unsupported {
base sn:establish-subscription-error;
description
"On-change is not supported for any objects which are
selectable by this filter.";
}
identity on-change-sync-unsupported {
base sn:establish-subscription-error;
description
"Neither sync on start nor resynchronization are supported
for this subscription. This error will be used for two
reasons. First if an 'establish-subscription' RPC includes
'sync-on-start', yet the publisher can't support sending a
'push-update' for this subscription for reasons other than
'on-change-unsupported' or 'sync-too-big'. And second,
if the 'resync-subscription' RPC is invoked either for an
existing periodic subscription, or for an on-change
subscription which can't support resynchronization.";
}
identity period-unsupported {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-suspended-reason;
description
"Requested time period or dampening-period is too short. This
can be for both periodic and on-change subscriptions (with or
without dampening.) Hints suggesting alternative periods may
be returned as supplemental information.";
}
identity update-too-big {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-suspended-reason;
description
"Periodic or on-change push update datatrees exceed a maximum
size limit. Hints on estimated size of what was too big may
be returned as supplemental information.";
}
identity sync-too-big {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base resync-subscription-error;
base sn:subscription-suspended-reason;
description
"Sync-on-start or resynchronization datatree exceeds a
maximum size limit. Hints on estimated size of what was too
big may be returned as supplemental information.";
}
identity unchanging-selection {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
base sn:subscription-terminated-reason;
description
"Selection filter is unlikely to ever select datatree nodes.
This means that based on the subscriber's current access
rights, the publisher recognizes that the selection filter is
unlikely to ever select datatree nodes which change. Examples
for this might be that node or subtree doesn't exist, read
access is not permitted for a receiver, or static objects
that only change at reboot have been chosen.";
}
/*
* TYPE DEFINITIONS
*/
typedef change-type {
type enumeration {
enum "create" {
description
"A change that refers to the creation of a new datastore
node.";
}
enum "delete" {
description
"A change that refers to the deletion of a datastore
node.";
}
enum "insert" {
description
"A change that refers to the insertion of a new
user-ordered datastore node.";
}
enum "move" {
description
"A change that refers to a reordering of the target
datastore node";
}
enum "replace" {
description
"A change that refers to a replacement of the target
datastore node's value.";
}
}
description
"Specifies different types of datastore changes.";
reference
"RFC 8072 section 2.5, with a delta that it is valid for a
receiver to process an update record which performs a create
operation on a datastore node the receiver believes exists,
or to process a delete on a datastore node the receiver
believes is missing.";
}
typedef selection-filter-ref {
type leafref {
path "/sn:filters/yp:selection-filter/yp:filter-id";
}
description
"This type is used to reference a selection filter.";
}
/*
* GROUP DEFINITIONS
*/
grouping datastore-criteria {
description
"A grouping to define criteria for which selected objects
from a targeted datastore should be included in push
updates.";
leaf datastore {
type identityref {
base ds:datastore;
}
mandatory true;
description
"Datastore from which to retrieve data.";
}
uses selection-filter-objects;
}
grouping selection-filter-types {
description
"This grouping defines the types of selectors for objects
from a datastore.";
choice filter-spec {
description
"The content filter specification for this request.";
anydata datastore-subtree-filter {
if-feature "sn:subtree";
description
"This parameter identifies the portions of the
target datastore to retrieve.";
reference
"RFC 6241: Network Configuration Protocol, Section 6.";
}
leaf datastore-xpath-filter {
if-feature "sn:xpath";
type yang:xpath1.0;
description
"This parameter contains an XPath expression identifying
the portions of the target datastore to retrieve.
If the expression returns a node-set, all nodes in the
node-set are selected by the filter. Otherwise, if the
expression does not return a node-set, the filter
doesn't select any nodes.
The expression is evaluated in the following XPath
context:
o The set of namespace declarations are those in scope
on the 'datastore-xpath-filter' leaf element.
o The set of variable bindings is empty.
o The function library is the core function library, and
the XPath functions defined in section 10 in RFC 7950.
o The context node is the root node of the target
datastore.";
}
}
}
grouping selection-filter-objects {
description
"This grouping defines a selector for objects from a
datastore.";
choice selection-filter {
description
"The source of the selection filter applied to the
subscription. This will come either referenced from a
global list, or be provided within the subscription
itself.";
case by-reference {
description
"Incorporate a filter that has been configured
separately.";
leaf selection-filter-ref {
type selection-filter-ref;
mandatory true;
description
"References an existing selection filter which is to be
applied to the subscription.";
}
}
case within-subscription {
description
"Local definition allows a filter to have the same
lifecycle as the subscription.";
uses selection-filter-types;
}
}
}
grouping update-policy-modifiable {
description
"This grouping describes the datastore specific subscription
conditions that can be changed during the lifetime of the
subscription.";
choice update-trigger {
when "../sn:target/yp:datastore";
mandatory true;
description
"Defines necessary conditions for sending an event record to
the subscriber.";
case periodic {
container periodic {
presence "indicates a periodic subscription";
description
"The publisher is requested to notify periodically the
current values of the datastore as defined by the
selection filter.";
leaf period {
type yang:timeticks;
mandatory true;
description
"Duration of time which should occur between periodic
push updates, in one hundredths of a second.";
}
leaf anchor-time {
type yang:date-and-time;
description
"Designates a timestamp before or after which a
series of periodic push updates are determined. The
next update will take place at a whole multiple
interval from the anchor time. For example, for an
anchor time is set for the top of a particular
minute and a period interval of a minute, updates
will be sent at the top of every minute this
subscription is active.";
}
}
}
case on-change {
if-feature "on-change";
container on-change {
presence "indicates an on-change subscription";
description
"The publisher is requested to notify changes in
values in the datastore subset as defined by a
selection filter.";
leaf dampening-period {
type yang:timeticks;
default 0;
description
"Specifies the minimum interval between the assembly
of successive update records for a single receiver
of a subscription. Whenever subscribed objects
change, and a dampening period interval (which may
be zero) has elapsed since the previous update
record creation for a receiver, then any subscribed
objects and properties which have changed since the
previous update record will have their current
values marshalled and placed into a new update
6 record.";
}
}
}
}
}
grouping update-policy {
description
"This grouping describes the datastore specific subscription
conditions of a subscription.";
uses update-policy-modifiable {
augment "update-trigger/on-change/on-change" {
description
"Includes objects not modifiable once subscription is
established.";
leaf sync-on-start {
type boolean;
default "true";
description
"When this object is set to false, it restricts an
on-change subscription from sending push-update
notifications. When false, pushing a full selection
per the terms of the selection filter MUST NOT be done
for this subscription. Only updates about changes,
i.e. only push-change-update notifications are sent.
When true (default behavior), in order to facilitate a
receiver's synchronization, a full update is sent when
the subscription starts using a push-update
notification. After that, push-change-update
notifications are exclusively sent unless the
publisher chooses to resync the subscription via a new
push-update notification.";
}
leaf-list excluded-change {
type change-type;
description
"Use to restrict which changes trigger an update.
For example, if modify is excluded, only creation and
deletion of objects is reported.";
}
}
}
}
grouping hints {
description
"Parameters associated with some error for a subscription
made upon a datastore.";
leaf period-hint {
type yang:timeticks;
description
"Returned when the requested time period is too short. This
hint can assert a viable period for either a periodic push
cadence or an on-change dampening interval.";
}
leaf filter-failure-hint {
type string;
description
"Information describing where and/or why a provided filter
was unsupportable for a subscription.";
}
leaf object-count-estimate {
type uint32;
description
"If there are too many objects which could potentially be
returned by the selection filter, this identifies the
estimate of the number of objects which the filter would
potentially pass.";
}
leaf object-count-limit {
type uint32;
description
"If there are too many objects which could be returned by
the selection filter, this identifies the upper limit of
the publisher's ability to service for this subscription.";
}
leaf kilobytes-estimate {
type uint32;
description
"If the returned information could be beyond the capacity
of the publisher, this would identify the data size which
could result from this selection filter.";
}
leaf kilobytes-limit {
type uint32;
description
"If the returned information would be beyond the capacity
of the publisher, this identifies the upper limit of the
publisher's ability to service for this subscription.";
}
}
/*
* RPCs
*/
rpc resync-subscription {
if-feature "on-change";
description
"This RPC allows a subscriber of an active on-change
subscription to request a full push of objects.
A successful invocation results in a push-update of all
datastore nodes that the subscriber is permitted to access.
This RPC can only be invoked on the same session on which the
subscription is currently active. In case of an error, a
resync-subscription-error is sent as part of an error
response.";
input {
leaf id {
type sn:subscription-id;
mandatory true;
description
"Identifier of the subscription that is to be resynced.";
}
}
}
rc:yang-data resync-subscription-error {
container resync-subscription-error {
description
"If a 'resync-subscription' RPC fails, the subscription is
not resynced and the RPC error response MUST indicate the
reason for this failure. This yang-data MAY be inserted as
structured data within a subscription's RPC error response
to indicate the failure reason.";
leaf reason {
type identityref {
base resync-subscription-error;
}
mandatory true;
description
"Indicates the reason why the publisher has declined a
request for subscription resynchronization.";
}
uses hints;
}
}
augment "/sn:establish-subscription/sn:input" {
when "sn:target/yp:datastore";
description
"This augmentation adds additional subscription parameters
that apply specifically to datastore updates to RPC input.";
uses update-policy;
}
augment "/sn:establish-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid target
for the subscription to RPC input.";
case datastore {
description
"Information specifying the parameters of an request for a
datastore subscription.";
uses datastore-criteria;
}
}
rc:yang-data establish-subscription-datastore-error-info {
container establish-subscription-datastore-error-info {
description
"If any 'establish-subscription' RPC parameters are
unsupportable against the datastore, a subscription is not
created and the RPC error response MUST indicate the reason
why the subscription failed to be created. This yang-data
MAY be inserted as structured data within a subscription's
RPC error response to indicate the failure reason. This
yang-data MUST be inserted if hints are to be provided back
to the subscriber.";
leaf reason {
type identityref {
base sn:establish-subscription-error;
}
description
"Indicates the reason why the subscription has failed to
be created to a targeted datastore.";
}
uses hints;
}
}
augment "/sn:modify-subscription/sn:input" {
when "sn:target/yp:datastore";
description
"This augmentation adds additional subscription parameters
specific to datastore updates.";
uses update-policy-modifiable;
}
augment "/sn:modify-subscription/sn:input/sn:target" {
description
"This augmentation adds the datastore as a valid target
for the subscription to RPC input.";
case datastore {
description
"Information specifying the parameters of an request for a
datastore subscription.";
uses selection-filter-objects;
}
}
rc:yang-data modify-subscription-datastore-error-info {
container modify-subscription-datastore-error-info {
description
"This yang-data MAY be provided as part of a subscription's
RPC error response when there is a failure of a
'modify-subscription' RPC which has been made against a
datastore. This yang-data MUST be used if hints are to be
provides back to the subscriber.";
leaf reason {
type identityref {
base sn:modify-subscription-error;
}
description
"Indicates the reason why the subscription has failed to
be modified.";
}
uses hints;
}
}
/*
* NOTIFICATIONS
*/
notification push-update {
description
"This notification contains a push update, containing data
subscribed to via a subscription. This notification is sent
for periodic updates, for a periodic subscription. It can
also be used for synchronization updates of an on-change
subscription. This notification shall only be sent to
receivers of a subscription. It does not constitute a
general-purpose notification that would be subscribable as
part of the NETCONF event stream by any receiver.";
leaf id {
type sn:subscription-id;
description
"This references the subscription which drove the
notification to be sent.";
}
anydata datastore-contents {
description
"This contains the updated data. It constitutes a snapshot
at the time-of-update of the set of data that has been
subscribed to. The snapshot corresponds to the same
snapshot that would be returned in a corresponding get
operation with the same selection filter parameters
applied.";
}
leaf incomplete-update {
type empty;
description
"This is a flag which indicates that not all datastore
nodes subscribed to are included with this update. In
other words, the publisher has failed to fulfill its full
subscription obligations, and despite its best efforts is
providing an incomplete set of objects.";
}
}
notification push-change-update {
if-feature "on-change";
description
"This notification contains an on-change push update. This
notification shall only be sent to the receivers of a
subscription; it does not constitute a general-purpose
notification.";
leaf id {
type sn:subscription-id;
description
"This references the subscription which drove the
notification to be sent.";
}
container datastore-changes {
description
"This contains the set of datastore changes of the
target datastore starting at the time of the
previous update, per the terms of the subscription.
The datastore changes are encoded per RFC 8027
(YANG Patch).";
uses ypatch:yang-patch;
}
leaf incomplete-update {
type empty;
description
"The presence of this object indicates not all changes which
have occurred since the last update are included with this
update. In other words, the publisher has failed to
fulfill its full subscription obligations, for example in
cases where it was not able to keep up with a change
burst.";
}
}
augment "/sn:subscription-started" {
description
"This augmentation adds datastore-specific objects to
the notification that a subscription has started.";
uses update-policy;
}
augment "/sn:subscription-started/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the notification that a subscription has started.";
case datastore {
uses datastore-criteria {
refine "selection-filter/within-subscription" {
description
"Specifies the selection filter and where it
originated from. If the 'selection-filter-ref' is
populated, the filter within the subscription came
from the 'filters' container. Otherwise it is
populated in-line as part of the subscription itself.";
}
}
}
}
augment "/sn:subscription-modified" {
description
"This augmentation adds datastore-specific objects to
the notification that a subscription has been modified.";
uses update-policy;
}
augment "/sn:subscription-modified/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the notification that a subscription has been
modified.";
case datastore {
uses datastore-criteria {
refine "selection-filter/within-subscription" {
description
"Specifies where the selection filter, and where it
came from within the subscription and then populated
within this notification. If the
'selection-filter-ref' is populated, the filter within
the subscription came from the 'filters' container.
Otherwise it is populated in-line as part of the
subscription itself.";
}
}
}
}
/*
* DATA NODES
*/
augment "/sn:filters" {
description
"This augmentation allows the datastore to be included as part
of the selection filtering criteria for a subscription.";
list selection-filter {
key "filter-id";
description
"A list of pre-configured filters that can be applied
to datastore subscriptions.";
leaf filter-id {
type string;
description
"An identifier to differentiate between selection
filters.";
}
uses selection-filter-types;
}
}
augment "/sn:subscriptions/sn:subscription" {
when "sn:target/yp:datastore";
description
"This augmentation adds many datastore specific objects to a
subscription.";
uses update-policy;
}
augment "/sn:subscriptions/sn:subscription/sn:target" {
description
"This augmentation allows the datastore to be included as
part of the selection filtering criteria for a subscription.";
case datastore {
uses datastore-criteria;
}
}
}
<CODE ENDS>
This document registers the following namespace URI in the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-yang-push
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers the following YANG module in the "YANG Module Names" registry [RFC6020]:
Name: ietf-yang-push
Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-push
Prefix: yp
Reference: draft-ietf-netconf-yang-push-20.txt (RFC form)
The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246].
The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.
There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability. (It should be noted that the YANG module augments the YANG module from [I-D.draft-ietf-netconf-subscribed-notifications]. All security considerations that are listed there are relevant also for datastore subscriptions. In the following, we focus on the data nodes that are newly introduced here.)
For their valuable comments, discussions, and feedback, we wish to acknowledge Tim Jenkins, Martin Bjorklund, Kent Watsen, Susan Hares, Yang Geng, Peipei Guo, Michael Scharf, Guangying Zheng, Tom Petch, Henk Birkholz, Reshad Rahman, Qin Wu, Rohit Ranade, and Rob Wilton.
| [I-D.draft-ietf-netconf-subscribed-notifications] | Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A. and E. Nilsen-Nygaard, "Custom Subscription to Event Streams", Internet-Draft draft-ietf-netconf-subscribed-notifications-13, August 2018. |
| [RFC3688] | Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004. |
| [RFC6020] | Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010. |
| [RFC6470] | Bierman, A., "Network Configuration Protocol (NETCONF) Base Notifications", RFC 6470, DOI 10.17487/RFC6470, February 2012. |
| [RFC6991] | Schoenwaelder, J., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013. |
| [RFC7895] | Bierman, A., Bjorklund, M. and K. Watsen, "YANG Module Library", RFC 7895, DOI 10.17487/RFC7895, June 2016. |
| [RFC7950] | Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016. |
| [RFC8040] | Bierman, A., Bjorklund, M. and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017. |
| [RFC8072] | Bierman, A., Bjorklund, M. and K. Watsen, "YANG Patch Media Type", RFC 8072, DOI 10.17487/RFC8072, February 2017. |
| [RFC8341] | Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018. |
| [RFC8342] | Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K. and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018. |
Rejection of an RPC for any reason is indicated by via RPC error response from the publisher. Valid RPC errors returned include both existing transport layer RPC error codes, such as those seen with NETCONF in [RFC6241], as well as subscription specific errors such as those defined within the YANG model. As a result, how subscription errors are encoded within an RPC error response is transport dependent.
References to specific identities within the either the subscribed-notifications YANG model or the yang-push YANG model may be returned as part of the error responses resulting from failed attempts at datastore subscription. Following are valid errors per RPC (note: throughout this section the prefix 'sn' indicates an item imported from the subscribed-notifications.yang model):
establish-subscription modify-subscription
---------------------- -------------------
cant-exclude sn:filter-unsupported
datastore-not-subscribable sn:insufficient-resources
sn:dscp-unavailable sn:no-such-subscription
sn:filter-unsupported period-unsupported
sn:insufficient-resources update-too-big
on-change-unsupported sync-too-big
on-change-sync-unsupported unchanging-selection
period-unsupported
update-too-big resync-subscription
sync-too-big --------------------
unchanging-selection no-such-subscription-resync
sync-too-big
delete-subscription kill-subscription
---------------------- -----------------
sn:no-such-subscription sn:no-such-subscription
There is one final set of transport independent RPC error elements included in the YANG model. These are the following four yang-data structures for failed datastore subscriptions:
1. yang-data establish-subscription-error-datastore
This MUST be returned if information identifying the reason for an
RPC error has not been placed elsewhere within the transport
portion of a failed "establish-subscription" RPC response. This
MUST be sent if hints are included.
2. yang-data modify-subscription-error-datastore
This MUST be returned if information identifying the reason for an
RPC error has not been placed elsewhere within the transport
portion of a failed "modifiy-subscription" RPC response. This
MUST be sent if hints are included.
3. yang-data sn:delete-subscription-error
This MUST be returned if information identifying the reason for an
RPC error has not been placed elsewhere within the transport
portion of a failed "delete-subscription" or "kill-subscription"
RPC response.
4. yang-data resync-subscription-error
This MUST be returned if information identifying the reason for an
RPC error has not been placed elsewhere within the transport
portion of a failed "resync-subscription" RPC response.
A subscription may be unexpectedly terminated or suspended independent of any RPC or configuration operation. In such cases, indications of such a failure MUST be provided. To accomplish this, the following types of error identities may be returned within the corresponding subscription state change notification:
subscription-terminated subscription-suspended
----------------------- ----------------------
datastore-not-subscribable sn:insufficient-resources
sn:filter-unavailable period-unsupported
sn:no-such-subscription update-too-big
sn:suspension-timeout synchronization-size
unchanging-selection
(To be removed by RFC editor prior to publication)
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