NETCONF A. Clemm Internet-Draft Huawei Intended status: Standards Track E. Voit Expires: April 5, 2018 Cisco Systems A. Gonzalez Prieto VMware A. Tripathy E. Nilsen-Nygaard Cisco Systems A. Bierman YumaWorks B. Lengyel Ericsson October 2, 2017 Subscribing to YANG datastore push updates draft-ietf-netconf-yang-push-10 Abstract Providing rapid visibility into changes made on YANG configuration and operational objects enables new capabilities such as remote mirroring of configuration and operational state. Via the mechanism described in this document, subscriber applications may request a continuous, customized stream of updates from a YANG datastore. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 5, 2018. Clemm, et al. Expires April 5, 2018 [Page 1] Internet-Draft YANG-Push October 2017 Copyright Notice Copyright (c) 2017 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 4 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Event Subscription Model . . . . . . . . . . . . . . . . 5 3.2. Negotiation of Subscription Policies . . . . . . . . . . 6 3.3. On-Change Considerations . . . . . . . . . . . . . . . . 6 3.4. Promise-Theory Considerations . . . . . . . . . . . . . . 7 3.5. Data Encodings . . . . . . . . . . . . . . . . . . . . . 8 3.6. Datastore Selection Filters . . . . . . . . . . . . . . . 8 3.7. Streaming Updates . . . . . . . . . . . . . . . . . . . . 10 3.8. Subscription Management . . . . . . . . . . . . . . . . . 13 3.9. Receiver Authorization . . . . . . . . . . . . . . . . . 14 3.10. On-change Notifiable YANG objects . . . . . . . . . . . . 16 3.11. Other Considerations . . . . . . . . . . . . . . . . . . 17 4. A YANG data model for management of datastore push subscriptions . . . . . . . . . . . . . . . . . . . . . . . . 18 4.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2. Subscription configuration . . . . . . . . . . . . . . . 25 4.3. YANG Notifications . . . . . . . . . . . . . . . . . . . 27 Clemm, et al. Expires April 5, 2018 [Page 2] Internet-Draft YANG-Push October 2017 4.4. YANG RPCs . . . . . . . . . . . . . . . . . . . . . . . . 28 5. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 33 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 7. Security Considerations . . . . . . . . . . . . . . . . . . . 48 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 49 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 49 9.1. Normative References . . . . . . . . . . . . . . . . . . 49 9.2. Informative References . . . . . . . . . . . . . . . . . 50 Appendix A. Changes between revisions . . . . . . . . . . . . . 50 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 1. Introduction Traditional approaches to remote visibility 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: o Polling incurs significant latency. This latency prohibits many application types. o Polling cycles may be missed, requests may be delayed or get lost, often when the network is under stress and the need for the data is the greatest. o Polling requests may undergo slight fluctuations, resulting in intervals of different lengths. The resulting data is difficult to calibrate and compare. o For applications that monitor for changes, many remote polling cycles place ultimately fruitless load on the network, devices, and applications. 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 YANG datastore and that enables the 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 Notifications" [subscribe]. Supplementing that work are YANG data model augmentations, extended RPCs, and new datastore specific update notifications. Transport options for [subscribe] will work seamlessly with this solution. Clemm, et al. Expires April 5, 2018 [Page 3] Internet-Draft YANG-Push October 2017 2. Definitions and Acronyms The terms below supplement those defined in [subscribe]. Data node: An instance of management information in a YANG datastore. Data node update: A data item containing the current value/property of a Data node at the time the data node update was created. Datastore: A conceptual store of instantiated management information, with individual data items represented by data nodes which are arranged in hierarchical manner. Data subtree: An instantiated data node and the data nodes that are hierarchically contained within it. Notification message: A transport encapsulated update record(s) and/ or event notification(s) intended to be sent to a receiver. Update notification message: A notification message that contains an update record. Update record: A representation data node update(s) resulting from the application of a filter for a subscription. An update record will include the value/property of one or more data nodes at a point in time. It may contain the update type for each data node (e.g., add, change, delete). Also included may be metadata/headers such as a subscription-id. Update trigger: A mechanism that determines when an update record needs to be generated. YANG-Push: The subscription and push mechanism for YANG datastores that is specified in this document. 3. Solution Overview This document specifies a solution for a push update subscription service. This solution supports the dynamic as well as configured subscriptions to information updates from YANG datastores. Subscriptions specify when update notification messages should be sent and what data to include in update records. YANG objects are subsequently pushed from the publisher to the receiver per the terms of the subscription. Clemm, et al. Expires April 5, 2018 [Page 4] Internet-Draft YANG-Push October 2017 3.1. Event Subscription Model YANG-push subscriptions are defined using a data model that is itself defined in YANG. This model enhances the event subscription model defined in [subscribe] with capabilities that allow subscribers to subscribe to data node updates, specifically to specify the triggers defining when to generate update records as well as what to include in an update record. Key enhancements include: o Specification of selection filters which identify targeted YANG data nodes and/or subtrees within a datastore for which updates are to be pushed. o An encoding (using anydata) for the contents of periodic and on- change push updates. o Specification of update policies contain conditions which trigger the generation and pushing of new update records. There are two types of triggers for subscriptions: periodic and on-change. * For periodic subscriptions, the trigger is specified by two parameters that define when updates are to be pushed. These parameters are the period interval with which to report updates, and an anchor time which can be used to calculate at which point in time updates need to be assembled and sent. * For on-change subscriptions, a trigger occurs whenever a change in the subscribed information is detected. Included are additional parameters such as: + Dampening period: In an on-change subscription, the first change that is detected results in an update to be sent immediately. However, sending successive updates whenever further changes are detected might result in quick exhaustion of resources in case of very rapid changes. In order to protect against that, a dampening period is used to specify the interval which must pass before successive update records for the same subscription are generated. The dampening period collectively applies to the set of all data nodes of a single subscription. This means that when there is a change to a subscribed object, an update record containing that object is created either immediately when no dampening period is already in effect, or at the end of a dampening period. + Change type: This parameter can be used to reduce the types of datastore changes for which updates are sent (e.g., you Clemm, et al. Expires April 5, 2018 [Page 5] Internet-Draft YANG-Push October 2017 might only send when an object is created or deleted, but not when an object value changes). + No Synch on start: defines whether or not a complete push- update of all subscribed data will be sent at the beginning of a subscription. Such early synchronization establishes the frame of reference for subsequent updates. 3.2. Negotiation of Subscription Policies 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 the request. In this case, a subscriber may quickly follow up with a new subscription request using different parameters. Random guessing at different parameters by a subscriber is to be discouraged. Therefore, in order to minimize the number of subscription iterations between subscriber and publisher, dynamic subscriptions SHOULD support a simple negotiation between subscribers and publishers for subscription parameters. This negotiation is in the form of a no-success response to a failed establish or modify subscription request. The no-success message SHOULD include in the returned error response information that, when considered, increases the likelihood of success for subsequent requests. However, there are no guarantees that subsequent requests for this subscriber will be accepted. [subscribe] contains several negotiable subscription parameters. Additional yang-push negotiation information defined in this specification includes hints at acceptable time intervals, size estimates for the number or objects which would be returned from a filter, and the location of an error in a provided filter. 3.3. On-Change Considerations On-change subscriptions allow subscribers to subscribe to 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 Clemm, et al. Expires April 5, 2018 [Page 6] Internet-Draft YANG-Push October 2017 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, whether or not their values actually 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 subscription MAY be suspended. 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 current values of all changed objects which are current at the time the dampening period expires. 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, the last change will still be sent. This will indicate churn is occurring on that object. In cases where a subscriber wants to have separate dampening periods for different objects, multiple subscriptions with different objects in a selection filter can be created. 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. 3.4. Promise-Theory Considerations A subscription to updates from a YANG 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 updates being silently dropped. In other words, a subscription constitutes a promise on the side of the Clemm, et al. Expires April 5, 2018 [Page 7] Internet-Draft YANG-Push October 2017 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 data objects 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. If for some reason the publisher of a subscription is not able to keep its promise, receivers MUST be notified immediately and reliably. The publisher MAY also suspend the subscription. A publisher SHOULD reject a request for a subscription if it is unlikely that the publisher will be able 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. 3.5. Data Encodings A publisher MUST support XML encoding and MAY support other encodings such as JSON encoding. 3.5.1. Periodic Subscriptions In a periodic subscription, the data included as part of an update corresponds to data that could have been simply retrieved using a get operation and is encoded in the same way. XML encoding rules for data nodes are defined in [RFC7950]. JSON encoding rules are defined in [RFC7951]. 3.5.2. On-Change Subscriptions In an on-change subscription, updates need to indicate not only values of changed data nodes but also the types of changes that occurred since the last update. Therefore encoding rules for data in on-change updates will 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 configuration objects only. 3.6. Datastore Selection Filters Subscription policy specifies both the selection filters and the datastores against which these selection filters will be applied. Clemm, et al. Expires April 5, 2018 [Page 8] Internet-Draft YANG-Push October 2017 The result is the push of information necessary to remotely maintain an extract of the publisher's datastore. Only a single selection filter can be applied to a subscription at a time. The following selection filter types are included in the yang- push data model, and may be applied against a datastore: o subtree: A subtree selection filter identifies one or more subtrees. When specified, updates will only come from the data nodes of selected YANG subtree(s). The syntax and semantics correspond to that specified for [RFC6241] section 6. o xpath: An xpath selection filter is an XPath expression which may be meaningfully applied to a datastore. It is the results of this expression which will be pushed. These filters are intended to be used as selectors that define which objects are within the scope of a subscription. Filters are not intended to be used to filter objects based on a non-key property. Supporting non-key property filtering so would have a number of implications that would result in significant complexity. While it is possible to define extensions in the future that will support selection filtering based on values, this is not supported in this version of yang-push and a publisher MAY reject a subscription request that contains a filter for object values. Xpath itself provides powerful filtering constructs, and care must be used in filter definition. As an example, consider an xpath filter with a boolean result; such a result will not provide an easily interpretable subset of a datastore. Beyond the boolean example, it is quite possible to define an xpath filter where results are easy for an application to mis-interpret. Consider an xpath filter which only passes a datastore object when an interface is up. It is up to the receiver to understand implications of the presence or absence of objects in each update. It is not expected that implementations will support comprehensive filter syntax and boundless complexity. It will be up to implementations to describe what is viable, but the goal is to provide equivalent capabilities to what is available with a GET. Implementations MUST reject dynamic subscriptions or suspend configured subscriptions if they include filters which are unsupportable on a platform. Clemm, et al. Expires April 5, 2018 [Page 9] Internet-Draft YANG-Push October 2017 3.7. Streaming Updates Contrary to traditional data retrieval requests, datastore subscription enables an unbounded series of update records to be streamed over time. Two generic 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 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 will 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 resynch an on-change subscription. The push-update record contains a data snippet that contains an instantiated subtree with 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 e.g., a NETCONF "get" operation, 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 a data snippet that indicates the set of changes that data nodes have undergone since the last notification of YANG objects. In other words, this indicates which data nodes have been created, deleted, or have had changes to their values. In cases where multiple changes have occurred 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.) These new push-update or 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 an XML encoded notification message over NETCONF transport as per [netconf-notif]. Clemm, et al. Expires April 5, 2018 [Page 10] Internet-Draft YANG-Push October 2017 2015-03-09T19:14:56Z 1011 2015-03-09T19:14:55.233Z some_string Figure 1: Push example The following is an example of an on-change notification. It contains an update for subscription 89, including a new value for a leaf called beta, which is a child of a top-level container called alpha: 2015-03-09T19:14:56Z 89 2015-03-09T19:14:55.233Z 1500 Figure 2: Push example for on change The equivalent update when requesting json encoding: Clemm, et al. Expires April 5, 2018 [Page 11] Internet-Draft YANG-Push October 2017 2015-03-09T19:14:56Z 89 2015-03-09T19:14:55.233Z { "ietf-yang-patch:yang-patch": { "patch-id": [ null ], "edit": [ { "edit-id": "edit1", "operation": "merge", "target": "/alpha/beta", "value": { "beta": 1500 } } ] } } Figure 3: Push example for on change with JSON When the beta leaf is deleted, the publisher may send Clemm, et al. Expires April 5, 2018 [Page 12] Internet-Draft YANG-Push October 2017 2015-03-09T19:14:56Z 89 2015-03-09T19:14:55.233Z Figure 4: 2nd push example for on change update 3.8. Subscription Management The RPCs defined within [subscribe] have been enhanced to support YANG datastore subscription negotiation. Included in these enhancements are error codes which can indicate why a datastore subscription attempt has failed. A datastore subscription can be rejected for multiple reasons. This includes a too large subtree request, or the inability of the publisher 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. For instance, for the following request: Clemm, et al. Expires April 5, 2018 [Page 13] Internet-Draft YANG-Push October 2017 operational 500 encode-xml Figure 5: Establish-Subscription example the publisher might return: error-insufficient-resources 2000 Figure 6: Error response example As can be seen above the rejected subscription does not result in the generation of an rpc-reply with an rpc-error element. YANG-push specific errors and negotiation hints part are returned as part of normal RPC operations. 3.9. Receiver Authorization A receiver of subscription data MUST only be sent updates for which they have 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 subtrees. This enables YANG data pushed based on subscriptions to be authorized equivalently to a regular data retrieval (get) operation. A publisher MAY allow subscriptions which select non-existent or access-protected data. Such a capability permits a receiver the Clemm, et al. Expires April 5, 2018 [Page 14] Internet-Draft YANG-Push October 2017 ability to monitor the entire lifecyle of the data. In this case, all push-updates must be sent empty, and no push-change-updates will be sent until the data becomes visible for a receiver. A publisher MAY alternatively choose not to allow subscriptions which select non-existent or access-protected data. Such a capability enables the publisher to avoid having to perform filtering of authorized content on each update. Relevant scenarios here include: o the rejecting of a subscription request to access-protected objects, o the suspension of a subscription where new access-controlled objects are selected mid-subscription for which the receiver does not have the necessary authorization, or o the authorization privileges of a receiver change over the course of the subscription. In all these cases, the error identity "data-unavailable" SHOULD be returned. This reduces the possibility of access permission leakage. The contextual authorization model for data in YANG datastores is the NETCONF Access Control Model [RFC6536bis], Section 3.2.4. A clarification to this is that each of the individual nodes in a resulting update record MUST also have applied access control to resulting pushed messages. This includes validating that read access is ok for any nodes newly selected since the last update record for each receiver. +-------------+ +-------------------+ push-update / --> | data node | yes | | push-change-update | access | ---> | add data node | | allowed? | | to update message | +-------------+ +-------------------+ Figure 7: Access control for push updates If read access into previously accessible nodes has been lost due to a receiver permissions change, this SHOULD be reported as node 'delete' operations 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. Clemm, et al. Expires April 5, 2018 [Page 15] Internet-Draft YANG-Push October 2017 3.10. On-change Notifiable YANG objects In some cases, a publisher supporting on-change notifications may not be able to push updates for some object types on-change. Reasons for this might be that the value of the data node changes frequently (e.g., [RFC7223]'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. Support for on-change notification is usually specific to the individual YANG model and/or implementation so it is possible to define in design time. System integrators need this information (without reading any data from a live node). The default assumption is that no data nodes support on-change notification. Schema nodes and subtrees that support on-change notifications MUST be marked by accordingly with the YANG extension "notifiable-on-change". This extension is defined in the data model below. When an on-change subscription is established, data-nodes are automatically excluded unless they are marked with notifiable-on- change as true. This also means that authorization checks SHALL NOT be performed on them. A subscriber can identify which nodes may be included in on-change updates by retrieving the data nodes in the subscription's scope and checking for which notifiable-on-change is marked as true. In theory, adding notifiable-on-change markings can be done within corresponding YANG models. But a more extensible way to avoid having to modify existing module definitions is to add notifiable-on-change markings within separate module deviations. This means that when a YANG model designer wants to add a notifiable-on-change marking to nodes of an existing module without modifying the module definitions, a new module is introduced that contains deviation statements which add "notifiable-on-change" statements as applicable. deviation /sys:system/sys:system-time { deviate add { yp:notifiable-on-change false; } } Figure 8: Deviation Example Clemm, et al. Expires April 5, 2018 [Page 16] Internet-Draft YANG-Push October 2017 3.11. Other Considerations 3.11.1. Robustness and reliability Particularly in the case of on-change push updates, it is important that push updates do not get lost or, in case the loss of an update is unavoidable, that the receiver is notified accordingly. Update messages for a single subscription MAY NOT be resequenced. 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 take one or more of the following actions. o A publisher MUST set the updates-not-sent flag on any update record which is known to be missing information. o It MAY choose to suspend a subscription as per [subscribe]. o When resuming an on-change subscription, the publisher SHOULD generate a complete patch from the previous update record. If this is not possible and the synch-on-start option is configured, then the full datastore contents MAY be sent via a push-update instead (effectively replacing the previous contents). If neither of these are possible, then an updates-not-sent flag MUST be included on the next push-change-update. Note: It is perfectly acceptable to have a series of push-change- updates (and even push updates) serially queued at the transport layer awaiting transmission. It is not required to merge pending update messages. I.e., the dampening period applies to update record creation, not transmission. 3.11.2. Publisher capacity 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 trigger (on-change or periodic), the period in which to report changes (1 second periods will consume more resources than 1 hour periods), the amount of data in the subtree that is being subscribed to, and the number and combination of other subscriptions that are concurrently being serviced. Clemm, et al. Expires April 5, 2018 [Page 17] Internet-Draft YANG-Push October 2017 4. A YANG data model for management of datastore push subscriptions 4.1. Overview The YANG data model for datastore push subscriptions is depicted in the following figure. Following YANG tree convention in the depiction, brackets enclose list keys, "rw" means configuration, "ro" operational state data, "?" designates optional nodes, "*" designates nodes that can have multiple instances. Parentheses with a name in the middle enclose choice and case nodes. New YANG objects defined here (i.e., beyond those from [subscribe]) are identified with "yp". module: ietf-subscribed-notifications +--ro streams | +--ro stream* [name] | +--ro name stream | +--ro description string | +--ro replay-support? empty {replay}? | +--ro replay-log-creation-time? yang:date-and-time {replay}? | +--ro replay-log-aged-time? yang:date-and-time {replay}? +--rw filters | +--rw event-filter* [identifier] | | +--rw identifier filter-id | | +--rw (filter-spec)? | | +--:(subtree-filter) | | | +--rw subtree-filter? | | +--:(xpath-filter) | | +--rw xpath-filter? yang:xpath1.0 | +--rw yp:selection-filter* [identifier] | +--rw yp:identifier sn:filter-id | +--rw (yp:filter-spec)? | +--:(yp:subtree-filter) | | +--rw yp:subtree-filter? | +--:(yp:xpath-filter) | +--rw yp:xpath-filter? yang:xpath1.0 +--rw subscription-config {configured-subscriptions}? | +--rw subscription* [identifier] | +--rw identifier subscription-id | +--rw encoding? encoding | +--rw (target) | | +--:(stream) | | | +--rw (event-filter)? | | | | +--:(by-reference) | | | | | +--rw event-filter-ref event-filter-ref | | | | +--:(within-subscription) | | | | +--rw (filter-spec)? | | | | +--:(subtree-filter) | | | | | +--rw subtree-filter? Clemm, et al. Expires April 5, 2018 [Page 18] Internet-Draft YANG-Push October 2017 | | | | +--:(xpath-filter) | | | | +--rw xpath-filter? yang:xpath1.0 | | | +--rw stream stream | | | +--rw replay-start-time? yang:date-and-time {replay}? | | +--:(yp:datastore) | | +--rw yp:source identityref | | +--rw (yp:selected-content)? | | +--:(yp:by-reference) | | | +--rw yp:selection-filter-ref selection-filter-ref | | +--:(yp:within-subscription) | | +--rw (yp:filter-spec)? | | +--:(yp:subtree-filter) | | | +--rw yp:subtree-filter? | | +--:(yp:xpath-filter) | | +--rw yp:xpath-filter? yang:xpath1.0 | +--rw stop-time? yang:date-and-time | +--rw receivers | | +--rw receiver* [address port] | | +--rw address inet:host | | +--rw port inet:port-number | | +--rw protocol? transport-protocol | +--rw (notification-origin)? | | +--:(interface-originated) | | | +--rw source-interface? if:interface-ref | | +--:(address-originated) | | +--rw source-vrf? string | | +--rw source-address? inet:ip-address-no-zone | +--rw (yp:update-trigger)? | | +--:(yp:periodic) | | | +--rw yp:period yang:timeticks | | | +--rw yp:anchor-time? yang:date-and-time | | +--:(yp:on-change) {on-change}? | | +--rw yp:dampening-period yang:timeticks | | +--rw yp:no-synch-on-start? empty | | +--rw yp:excluded-change* change-type | +--rw yp:dscp? inet:dscp | +--rw yp:weighting? uint8 | +--rw yp:dependency? sn:subscription-id +--ro subscriptions +--ro subscription* [identifier] +--ro identifier subscription-id +--ro configured-subscription? | empty {configured-subscriptions}? +--ro encoding? encoding +--ro (target) | +--:(stream) | | +--ro (event-filter)? | | | +--:(by-reference) Clemm, et al. Expires April 5, 2018 [Page 19] Internet-Draft YANG-Push October 2017 | | | | +--ro event-filter-ref event-filter-ref | | | +--:(within-subscription) | | | +--ro (filter-spec)? | | | +--:(subtree-filter) | | | | +--ro subtree-filter? | | | +--:(xpath-filter) | | | +--ro xpath-filter? yang:xpath1.0 | | +--ro stream stream | | +--ro replay-start-time? yang:date-and-time {replay}? | +--:(yp:datastore) | +--ro yp:source identityref | +--ro (yp:selected-content)? | +--:(yp:by-reference) | | +--ro yp:selection-filter-ref selection-filter-ref | +--:(yp:within-subscription) | +--ro (yp:filter-spec)? | +--:(yp:subtree-filter) | | +--ro yp:subtree-filter? | +--:(yp:xpath-filter) | +--ro yp:xpath-filter? yang:xpath1.0 +--ro stop-time? yang:date-and-time +--ro (notification-origin)? | +--:(interface-originated) | | +--ro source-interface? if:interface-ref | +--:(address-originated) | +--ro source-vrf? string | +--ro source-address? inet:ip-address-no-zone +--ro receivers | +--ro receiver* [address port] | +--ro address inet:host | +--ro port inet:port-number | +--ro protocol? transport-protocol | +--ro pushed-notifications? yang:counter64 | +--ro excluded-notifications? yang:counter64 | +--ro status subscription-status +--ro (yp:update-trigger)? | +--:(yp:periodic) | | +--ro yp:period yang:timeticks | | +--ro yp:anchor-time? yang:date-and-time | +--:(yp:on-change) {on-change}? | +--ro yp:dampening-period yang:timeticks | +--ro yp:no-synch-on-start? empty | +--ro yp:excluded-change* change-type +--ro yp:dscp? inet:dscp +--ro yp:weighting? uint8 +--ro yp:dependency? sn:subscription-id rpcs: Clemm, et al. Expires April 5, 2018 [Page 20] Internet-Draft YANG-Push October 2017 +---x establish-subscription | +---w input | | +---w encoding? encoding | | +---w (target) | | | +--:(stream) | | | | +---w (event-filter)? | | | | | +--:(by-reference) | | | | | | +---w event-filter-ref event-filter-ref | | | | | +--:(within-subscription) | | | | | +---w (filter-spec)? | | | | | +--:(subtree-filter) | | | | | | +---w subtree-filter? | | | | | +--:(xpath-filter) | | | | | +---w xpath-filter? yang:xpath1.0 | | | | +---w stream stream | | | | +---w replay-start-time? yang:date-and-time {replay}? | | | +--:(yp:datastore) | | | +---w yp:source identityref | | | +---w (yp:selected-content)? | | | +--:(yp:by-reference) | | | | +---w yp:selection-filter-ref selection-filter-ref | | | +--:(yp:within-subscription) | | | +---w (yp:filter-spec)? | | | +--:(yp:subtree-filter) | | | | +---w yp:subtree-filter? | | | +--:(yp:xpath-filter) | | | +---w yp:xpath-filter? yang:xpath1.0 | | +---w stop-time? yang:date-and-time | | +---w (yp:update-trigger)? | | | +--:(yp:periodic) | | | | +---w yp:period yang:timeticks | | | | +---w yp:anchor-time? yang:date-and-time | | | +--:(yp:on-change) {on-change}? | | | +---w yp:dampening-period yang:timeticks | | | +---w yp:no-synch-on-start? empty | | | +---w yp:excluded-change* change-type | | +---w yp:dscp? inet:dscp | | +---w yp:weighting? uint8 | | +---w yp:dependency? sn:subscription-id | +--ro output | +--ro subscription-result subscription-result | +--ro (result)? | +--:(no-success) | | +--ro filter-failure? string | | +--ro replay-start-time-hint? yang:date-and-time | | +--ro yp:period-hint? yang:timeticks | | +--ro yp:error-path? string | | +--ro yp:object-count-estimate? uint32 Clemm, et al. Expires April 5, 2018 [Page 21] Internet-Draft YANG-Push October 2017 | | +--ro yp:object-count-limit? uint32 | | +--ro yp:kilobytes-estimate? uint32 | | +--ro yp:kilobytes-limit? uint32 | +--:(success) | +--ro identifier subscription-id +---x modify-subscription | +---w input | | +---w identifier? subscription-id | | +---w (target) | | | +--:(stream) | | | | +---w (event-filter)? | | | | +--:(by-reference) | | | | | +---w event-filter-ref event-filter-ref | | | | +--:(within-subscription) | | | | +---w (filter-spec)? | | | | +--:(subtree-filter) | | | | | +---w subtree-filter? | | | | +--:(xpath-filter) | | | | +---w xpath-filter? yang:xpath1.0 | | | +--:(yp:datastore) | | | +---w (yp:selected-content)? | | | +--:(yp:by-reference) | | | | +---w yp:selection-filter-ref selection-filter-ref | | | +--:(yp:within-subscription) | | | +---w (yp:filter-spec)? | | | +--:(yp:subtree-filter) | | | | +---w yp:subtree-filter? | | | +--:(yp:xpath-filter) | | | +---w yp:xpath-filter? yang:xpath1.0 | | +---w stop-time? yang:date-and-time | | +---w (yp:update-trigger)? | | +--:(yp:periodic) | | | +---w yp:period yang:timeticks | | | +---w yp:anchor-time? yang:date-and-time | | +--:(yp:on-change) {on-change}? | | +---w yp:dampening-period yang:timeticks | +--ro output | +--ro subscription-result subscription-result | +--ro (result)? | +--:(no-success) | +--ro filter-failure? string | +--ro yp:period-hint? yang:timeticks | +--ro yp:error-path? string | +--ro yp:object-count-estimate? uint32 | +--ro yp:object-count-limit? uint32 | +--ro yp:kilobytes-estimate? uint32 | +--ro yp:kilobytes-limit? uint32 +---x delete-subscription Clemm, et al. Expires April 5, 2018 [Page 22] Internet-Draft YANG-Push October 2017 | +---w input | | +---w identifier subscription-id | +--ro output | +--ro subscription-result subscription-result +---x kill-subscription +---w input | +---w identifier subscription-id +--ro output +--ro subscription-result subscription-result notifications: +---n replay-completed | +--ro identifier subscription-id +---n subscription-completed | +--ro identifier subscription-id +---n subscription-started | +--ro identifier subscription-id | +--ro encoding? encoding | +--ro (target) | | +--:(stream) | | | +--ro (event-filter)? | | | | +--:(by-reference) | | | | | +--ro event-filter-ref event-filter-ref | | | | +--:(within-subscription) | | | | +--ro (filter-spec)? | | | | +--:(subtree-filter) | | | | | +--ro subtree-filter? | | | | +--:(xpath-filter) | | | | +--ro xpath-filter? yang:xpath1.0 | | | +--ro stream stream | | | +--ro replay-start-time? yang:date-and-time {replay}? | | +--:(yp:datastore) | | +--ro yp:source identityref | | +--ro (yp:selected-content)? | | +--:(yp:by-reference) | | | +--ro yp:selection-filter-ref selection-filter-ref | | +--:(yp:within-subscription) | | +--ro (yp:filter-spec)? | | +--:(yp:subtree-filter) | | | +--ro yp:subtree-filter? | | +--:(yp:xpath-filter) | | +--ro yp:xpath-filter? yang:xpath1.0 | +--ro stop-time? yang:date-and-time | +--ro (yp:update-trigger)? | | +--:(yp:periodic) | | | +--ro yp:period yang:timeticks | | | +--ro yp:anchor-time? yang:date-and-time | | +--:(yp:on-change) {on-change}? Clemm, et al. Expires April 5, 2018 [Page 23] Internet-Draft YANG-Push October 2017 | | +--ro yp:dampening-period yang:timeticks | | +--ro yp:no-synch-on-start? empty | | +--ro yp:excluded-change* change-type | +--ro yp:dscp? inet:dscp | +--ro yp:weighting? uint8 | +--ro yp:dependency? sn:subscription-id +---n subscription-resumed | +--ro identifier subscription-id +---n subscription-modified | +--ro identifier subscription-id | +--ro encoding? encoding | +--ro (target) | | +--:(stream) | | | +--ro (event-filter)? | | | | +--:(by-reference) | | | | | +--ro event-filter-ref event-filter-ref | | | | +--:(within-subscription) | | | | +--ro (filter-spec)? | | | | +--:(subtree-filter) | | | | | +--ro subtree-filter? | | | | +--:(xpath-filter) | | | | +--ro xpath-filter? yang:xpath1.0 | | | +--ro stream stream | | | +--ro replay-start-time? yang:date-and-time {replay}? | | +--:(yp:datastore) | | +--ro yp:source identityref | | +--ro (yp:selected-content)? | | +--:(yp:by-reference) | | | +--ro yp:selection-filter-ref selection-filter-ref | | +--:(yp:within-subscription) | | +--ro (yp:filter-spec)? | | +--:(yp:subtree-filter) | | | +--ro yp:subtree-filter? | | +--:(yp:xpath-filter) | | +--ro yp:xpath-filter? yang:xpath1.0 | +--ro stop-time? yang:date-and-time | +--ro (yp:update-trigger)? | | +--:(yp:periodic) | | | +--ro yp:period yang:timeticks | | | +--ro yp:anchor-time? yang:date-and-time | | +--:(yp:on-change) {on-change}? | | +--ro yp:dampening-period yang:timeticks | | +--ro yp:no-synch-on-start? empty | | +--ro yp:excluded-change* change-type | +--ro yp:dscp? inet:dscp | +--ro yp:weighting? uint8 | +--ro yp:dependency? sn:subscription-id +---n subscription-terminated Clemm, et al. Expires April 5, 2018 [Page 24] Internet-Draft YANG-Push October 2017 | +--ro identifier subscription-id | +--ro error-id subscription-errors | +--ro filter-failure? string +---n subscription-suspended +--ro identifier subscription-id +--ro error-id subscription-errors +--ro filter-failure? string module: ietf-yang-push rpcs: +---x resynch-subscription {on-change}? +---w input | +---w identifier sn:subscription-id +--ro output +--ro subscription-result sn:subscription-result notifications: +---n push-update | +--ro subscription-id? sn:subscription-id | +--ro time-of-update? yang:date-and-time | +--ro updates-not-sent? empty | +--ro datastore-contents? +---n push-change-update {on-change}? +--ro subscription-id? sn:subscription-id +--ro time-of-update? yang:date-and-time +--ro updates-not-sent? empty +--ro datastore-changes? Figure 9: Model structure Selected components of the model are summarized below. 4.2. Subscription configuration Both configured and dynamic subscriptions are represented within the list subscription. But only configured subscriptions are listed within list subscription-config. In both lists, each subscription has own list elements. New and enhanced parameters extending the basic subscription data model in [subscribe] include: o The targeted datastore from which the selection is being made. The potential datastores include those from [revised-datastores]. A platform may also choose to support a custom datastore. Clemm, et al. Expires April 5, 2018 [Page 25] Internet-Draft YANG-Push October 2017 o A selection filter identifying yang nodes of interest within a datastore. Filter contents are specified via a reference to an existing filter, or via an in-line definition for only that subscription. Referenced filters allows an implementation to avoid evaluating filter acceptability during a dynamic subscription request. The case statement differentiates the options. o For periodic subscriptions, triggered updates will occur at the boundaries of a specified time interval. These boundaries many be calculated from the periodic parameters: * a "period" which defines duration between period push updates. * an "anchor-time"; update intervals always fall on the points in time that are a multiple of a period from an anchor time. If anchor time is not provided, then the anchor time MUST be set with the creation time of the initial update record. o For on-change subscriptions, assuming the dampening period has completed, triggering occurs whenever a change in the subscribed information is detected. On-change subscriptions have more complex semantics that is guided by its own set of parameters: * a "dampening-period" specifies the interval that must pass before a successive update for the subscription is sent. If no dampening period is in effect, the update is sent immediately. If a subsequent change is detected, another update is only sent once the dampening period has passed for this subscription. * an "excluded-change" flag which allows restriction of the types of changes for which updates should be sent (e.g., only add to an update record on object creation). * a "no-synch-on-start" flag which specifies whether a complete update with all the subscribed data is to be sent at the beginning of a subscription. o Optional QoS parameters to indicate the treatment of a subscription relative to other traffic between publisher and receiver. These include: * A "dscp" QoS marking which MUST be stamped on notification messages to differentiate network QoS behavior. * A "weighting" so that bandwidth proportional to this weighting can be allocated to this subscription relative to other subscriptions destined for that receiver. Clemm, et al. Expires April 5, 2018 [Page 26] Internet-Draft YANG-Push October 2017 * a "dependency" upon another subscription. Notification messages MUST NOT be sent prior to other notification messages containing update record(s) for the referenced subscription. o A subscription's weighting MUST work identically to stream dependency weighting as described within RFC 7540, section 5.3.2. o A subscription's dependency MUST work identically to stream dependency as described within RFC 7540, sections 5.3.1, 5.3.3, and 5.3.4. If a dependency is attempted via an RPC, but the referenced subscription does not exist, the dependency will be removed. 4.3. YANG Notifications 4.3.1. State Change Notifications Subscription state notifications and mechanism are reused from [subscribe]. Some have been augmented to include the YANG datastore specific objects. 4.3.2. Notifications for Subscribed Content Along with the subscribed content, there are other objects which might be part of a push-update or push-change-update A subscription-id MUST be transported along with the subscribed contents. An [RFC5277] Section 4 one-way notification MAY be used for encoding updates. Where it is, the relevant subscription-id MUST be encoded as the first element within each push-update or push- change-update. This allows a receiver to differentiate which subscription resulted in a particular push. A "time-of-update" which represents the time an update record snapshot was generated. A receiver MAY assume that a publisher's objects have these pushed values at this point in time. An "updates-not-sent" flag is set, which indicates that the update record is incomplete. If the application detects an informational discontinuity in either notification, the notification MUST include a flag "updates-not-sent". This flag which 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 missed a window in providing objects 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. Clemm, et al. Expires April 5, 2018 [Page 27] Internet-Draft YANG-Push October 2017 4.4. YANG RPCs YANG-Push subscriptions are established, modified, and deleted using RPCs augmented from [subscribe]. 4.4.1. Establish-subscription RPC The subscriber sends an establish-subscription RPC with the parameters in section 3.1. An example might look like: operational 500 encode-xml Figure 10: Establish-subscription RPC The publisher MUST respond explicitly positively (i.e., subscription accepted) or negatively (i.e., subscription rejected) to the request. Positive responses include the subscription-id of the accepted subscription. In that case a publisher MAY respond: ok 52 Figure 11: Establish-subscription positive RPC response A subscription can be rejected for multiple reasons, including the lack of authorization to establish a subscription, the lack of read Clemm, et al. Expires April 5, 2018 [Page 28] Internet-Draft YANG-Push October 2017 authorization on the requested data node, or the inability of the publisher to provide a stream with the requested semantics. When the requester is not authorized to read the requested data node, the returned information indicates the node is unavailable. For instance, if the above request was unauthorized to read node "ex:foo" the publisher may return: subtree-unavailable /ex:foo Figure 12: Establish-subscription access denied response If a request is rejected because the publisher is not able to serve it, the publisher SHOULD include in the returned error what subscription parameters would have been accepted for the request. However, there are no guarantee that subsequent requests using this info will in fact be accepted. For example, for the following request: running 10 encode-xml Figure 13: Establish-subscription request example 2 Clemm, et al. Expires April 5, 2018 [Page 29] Internet-Draft YANG-Push October 2017 a publisher that cannot serve on-change updates but periodic updates might return the following: period-unsupported 100 Figure 14: Establish-subscription error response example 2 4.4.2. Modify-subscription RPC 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 of a subscription. 1011 250 Figure 15: Modify subscription request The publisher MUST respond explicitly positively or negatively to the request. A response to a successful modification might look like: Clemm, et al. Expires April 5, 2018 [Page 30] Internet-Draft YANG-Push October 2017 ok Figure 16: Modify subscription response If the subscription modification is rejected, the publisher MUST send a response like it does for an establish-subscription and maintain the subscription as it was before the modification request. Responses MAY include hints. A subscription MAY be modified multiple times. A configured subscription cannot be modified using modify- subscription RPC. Instead, the configuration needs to be edited as needed. 4.4.3. Delete-subscription RPC 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-id. Configured subscriptions cannot be deleted via RPC, but have to be removed from the configuration. This RPC is identical to the RPC from [subscribe]. 4.4.4. Resynch-subscription RPC This RPC is only applicable only for on-change subscriptions previously been established using an establish-subscription RPC. On receipt, a publisher must either reply 'ok' and quickly follow with a push-update, or send an appropriate error such as on-change-synch- unsupported. For example: Clemm, et al. Expires April 5, 2018 [Page 31] Internet-Draft YANG-Push October 2017 1011 ok Resynch subscription 4.4.5. YANG Module Synchronization To make subscription requests, the subscriber needs to know the YANG module library available on the publisher. The YANG 1.0 module library information is sent by a NETCONF server in the NETCONF 'hello' message. For YANG 1.1 modules and all modules used with the RESTCONF [RFC8040] protocol, this information is provided by the YANG Library module (ietf-yang-library.yang from [RFC7895]. This YANG library information is important for the receiver to reproduce the set of object definitions used within the publisher. The YANG library includes a module list with the name, revision, enabled features, and applied deviations for each YANG module implemented by the publisher. The receiver is expected to know the YANG library information before starting a subscription. The "/modules-state/module-set-id" leaf in the "ietf-yang-library" module can be used to cache the YANG library information. The set of modules, revisions, features, and deviations can change at run-time (if supported by the publisher implementation). In this case, the receiver needs to be informed of module changes before data nodes from changed modules can be processed correctly. The YANG library provides a simple "yang-library-change" notification that informs the subscriber that the library has changed. The receiver then needs to re-read the entire YANG library data for the replicated publisher in order to detect the specific YANG library changes. The "ietf-netconf-notifications" module defined in [RFC6470] contains a "netconf-capability-change" notification that can identify specific Clemm, et al. Expires April 5, 2018 [Page 32] Internet-Draft YANG-Push October 2017 module changes. For example, the module URI capability of a newly loaded module will be listed in the "added-capability" leaf-list, and the module URI capability of an removed module will be listed in the "deleted-capability" leaf-list. 5. YANG module ; file "ietf-yang-push.yang" module ietf-yang-push { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push"; prefix yp; import ietf-inet-types { prefix inet; } import ietf-yang-types { prefix yang; } import ietf-subscribed-notifications { prefix sn; } import ietf-datastores { prefix ds; } organization "IETF"; contact "WG Web: WG List: Editor: Alexander Clemm Editor: Eric Voit Editor: Alberto Gonzalez Prieto Editor: Ambika Prasad Tripathy Editor: Einar Nilsen-Nygaard Editor: Andy Bierman Clemm, et al. Expires April 5, 2018 [Page 33] Internet-Draft YANG-Push October 2017 Editor: Balazs Lengyel "; description "This module contains conceptual YANG specifications for YANG push."; revision 2017-10-02 { description "Initial revision."; reference "YANG Datastore Push, draft-ietf-netconf-yang-push-09"; } /* * EXTENSIONS */ extension notifiable-on-change { argument "value"; description "Indicates whether changes to the data node are reportable in on-change subscriptions. The statement MUST only be a substatement of the leaf, leaf-list, container, list, anyxml, anydata statements. Zero or One notifiable-on-change statement is allowed per parent statement. NO substatements are allowed. The argument is a boolean value indicating whether on-change notifications are supported. If notifiable-on-change is not specified, the default is the same as the parent data node's value. For top level data nodes the default value is false."; } /* * FEATURES */ feature on-change { description "This feature indicates that on-change triggered subscriptions are supported."; } /* * IDENTITIES */ Clemm, et al. Expires April 5, 2018 [Page 34] Internet-Draft YANG-Push October 2017 /* Error type identities for datastore subscription */ identity period-unsupported { base sn:error; description "Requested time period is too short. This can be for both periodic and on-change dampening."; } identity qos-unsupported { base sn:error; description "Subscription QoS parameters not supported on this platform."; } identity dscp-unavailable { base sn:error; description "Requested DSCP marking not allocatable."; } identity on-change-unsupported { base sn:error; description "On-change not supported."; } identity on-change-synch-unsupported { base sn:error; description "On-change synch-on-start and resynchonization not supported."; } identity reference-mismatch { base sn:error; description "Mismatch in filter key and referenced yang subtree."; } identity data-unavailable { base sn:error; description "Referenced yang node or subtree doesn't exist, or read access is not permitted."; } identity datatree-size { base sn:error; description Clemm, et al. Expires April 5, 2018 [Page 35] Internet-Draft YANG-Push October 2017 "Resulting periodic or on-change push updates may exceed a size limit during normal conditions."; } identity synchronization-datatree-size { base sn:error; description "The resulting Synch-on-start or resynchronization would push a datatree which exceeds size limit for a one-time update."; } /* Datastore identities */ identity custom-datastore { base ds:datastore; description "A datastore with boundaries not defined within draft-ietf-netmod-revised-datastores"; } /* * TYPE DEFINITIONS */ typedef change-type { type enumeration { enum "create" { description "Create a new data resource if it does not already exist. If it already exists, replace."; } enum "delete" { description "Delete a data resource if it already exists. If it does not exists, take no action."; } enum "insert" { description "Insert a new user-ordered data resource"; } enum "merge" { description "merge the edit value with the target data resource; create if it does not already exist"; } enum "move" { description Clemm, et al. Expires April 5, 2018 [Page 36] Internet-Draft YANG-Push October 2017 "Reorder the target data resource"; } enum "replace" { description "Replace the target data resource with the edit value"; } enum "remove" { description "Remove a data resource if it already exists "; } } description "Specifies different types of datastore changes."; reference "RFC 8072 section 2.5, with a delta that it is ok to receive ability create on an existing node, or receive a delete on a missing node."; } typedef selection-filter-ref { type leafref { path "/sn:filters/yp:selection-filter/yp:identifier"; } 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 source { type identityref { base ds:datastore; } mandatory true; description "Datastore from which to retrieve data."; } uses selection-filter-objects; } grouping selection-filter-types { description Clemm, et al. Expires April 5, 2018 [Page 37] Internet-Draft YANG-Push October 2017 "This grouping defines a selector for objects from a datastore."; choice filter-spec { description "The content filter specification for this request."; anydata subtree-filter { description "This parameter identifies the portions of the target datastore to retrieve."; reference "RFC 6241, Section 6."; } leaf xpath-filter { type yang:xpath1.0; description "This parameter contains an XPath expression identifying the portions of the target datastore to retrieve."; reference "http://www.w3.org/TR/1999/REC-xpath-19991116"; } } } grouping selection-filter-objects { description "This grouping defines a selector for objects from a datastore."; choice selected-content { 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; } Clemm, et al. Expires April 5, 2018 [Page 38] Internet-Draft YANG-Push October 2017 } } 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 { description "Defines necessary conditions for sending an event to the subscriber."; case periodic { description "The agent 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. Where the anchor-time is available, the push will include the objects and their values which exist at an exact multiple of timeticks aligning to this start-time anchor."; } 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"; description "The agent is requested to notify changes in values in the datastore subset as defined by a selection filter."; leaf dampening-period { type yang:timeticks; mandatory true; description "The shortest time duration which is allowed between the Clemm, et al. Expires April 5, 2018 [Page 39] Internet-Draft YANG-Push October 2017 creation of independent yang object update messages. Effectively this is the amount of time that needs to have passed since the last update. Zero indicates no delay."; } } } } grouping update-policy { description "This grouping describes the datastore specific subscription conditions of a subscription."; uses update-policy-modifiable { augment "update-trigger/on-change" { description "Includes objects not modifiable once subscription is established."; leaf no-synch-on-start { type empty; description "This leaf acts as a flag that determines behavior at the start of the subscription. When present, synchronization of state at the beginning of the subscription is outside the scope of the subscription. Only updates about changes that are observed from the start time, i.e. only push- change-update notifications are sent. When absent (default behavior), in order to facilitate a receiver's synchronization, a full update is sent when the subscription starts using a push-update notification, just like in the case of a periodic subscription. After that, push-change-update notifications only are sent unless the Publisher chooses to resynch the subscription again."; } 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 update-qos { description "This grouping describes Quality of Service information concerning a subscription. This information is passed to lower Clemm, et al. Expires April 5, 2018 [Page 40] Internet-Draft YANG-Push October 2017 layers for transport prioritization and treatment"; leaf dscp { type inet:dscp; default "0"; description "The push update's IP packet transport priority. This is made visible across network hops to receiver. The transport priority is shared for all receivers of a given subscription."; } leaf weighting { type uint8 { range "0 .. 255"; } description "Relative weighting for a subscription. Allows an underlying transport layer perform informed load balance allocations between various subscriptions"; reference "RFC-7540, section 5.3.2"; } leaf dependency { type sn:subscription-id; description "Provides the Subscription ID of a parent subscription which has absolute priority should that parent have push updates ready to egress the publisher. In other words, there should be no streaming of objects from the current subscription if the parent has something ready to push."; reference "RFC-7540, section 5.3.1"; } } grouping update-error-hints { description "Allow return additional negotiation hints that apply specifically to push updates."; leaf period-hint { type yang:timeticks; description "Returned when the requested time period is too short. This hint can assert an viable period for both periodic push cadence and on-change dampening."; } leaf error-path { type string; description "Reference to a YANG path which is associated with the error Clemm, et al. Expires April 5, 2018 [Page 41] Internet-Draft YANG-Push October 2017 being returned."; } 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 resynch-subscription { if-feature "on-change"; description "This RPC allows a subscriber of an active on-change subscription to request a full push of objects in there current state. A successful result would be the set of YANG objects equivalent to a Get using the existing selection criteria. This request may only come from the same subscriber using the establish-subscription RPC."; input { leaf identifier { Clemm, et al. Expires April 5, 2018 [Page 42] Internet-Draft YANG-Push October 2017 type sn:subscription-id; mandatory true; description "Identifier of the subscription that is to be resynched."; } } output { leaf subscription-result { type sn:subscription-result; mandatory true; description "Indicates whether the request for the subscription resynch has been accepted, or why it has been denied."; } } } /* * DATA NODES */ augment "/sn:establish-subscription/sn:input" { description "This augmentation adds additional subscription parameters that apply specifically to datastore updates to RPC input."; uses update-policy; uses update-qos; } augment "/sn:establish-subscription/sn:input/sn:target" { description "This augmentation adds the datastore as a valid parameter object for the subscription to RPC input. This provides a target for the filter."; case datastore { uses datastore-criteria; } } augment "/sn:establish-subscription/sn:output/"+ "sn:result/sn:no-success" { description "This augmentation adds datastore specific error info and hints to RPC output."; uses update-error-hints; } augment "/sn:modify-subscription/sn:input" { description "This augmentation adds additional subscription parameters specific to datastore updates."; Clemm, et al. Expires April 5, 2018 [Page 43] Internet-Draft YANG-Push October 2017 uses update-policy-modifiable; } augment "/sn:modify-subscription/sn:input/sn:target" { description "This augmentation adds the datastore as a valid parameter object for the subscription to RPC input. This provides a target for the filter."; case datastore { uses selection-filter-objects; } } augment "/sn:modify-subscription/sn:output/"+ "sn:result/sn:no-success" { description "This augmentation adds push datastore error info and hints to RPC output."; uses update-error-hints; } 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."; leaf subscription-id { type sn:subscription-id; description "This references the subscription which drove the notification to be sent."; } leaf time-of-update { type yang:date-and-time; description "This leaf identifies the generation time of the datastore selection within a push-update."; } leaf updates-not-sent { type empty; description "This is a flag which indicates that not all data nodes subscribed to are included with this update. In other words, the publisher has failed to fulfill its full subscription obligations. The result is intermittent loss of synchronization of data at the receiver."; Clemm, et al. Expires April 5, 2018 [Page 44] Internet-Draft YANG-Push October 2017 } 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 format and syntax of the data corresponds to the format and syntax of data that would be returned in a corresponding get operation with the same selection filter parameters applied."; } } 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 subscription-id { type sn:subscription-id; description "This references the subscription which drove the notification to be sent."; } leaf time-of-update { type yang:date-and-time; description "This leaf identifies the generation time of the datastore changes extract. If a dampening-period was in effect before the notification was generated, this may not be the time any of the datastore-changes were actually made."; } leaf updates-not-sent { type empty; description "This is a flag which indicates that 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."; } anydata datastore-changes { description "This contains an incremental set of datastore changes needed to update a remote datastore starting at the time of the previous update, per the terms of the subscription. Changes are encoded analogous to the syntax of a corresponding yang- Clemm, et al. Expires April 5, 2018 [Page 45] Internet-Draft YANG-Push October 2017 patch operation, i.e. a yang-patch operation applied to the YANG datastore implied by the previous update to result in the current state."; reference "RFC 8072 section 2.5, with a delta that it is ok to receive ability create on an existing node, or receive a delete on a missing node."; } } augment "/sn:subscription-started" { description "This augmentation adds many yang datastore specific objects to the notification that a subscription has started."; uses update-policy; uses update-qos; } 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; } } 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 "identifier"; description "A list of pre-positioned filters that can be applied to datastore subscriptions."; leaf identifier { type sn:filter-id; description "An identifier to differentiate between selection filters."; } uses selection-filter-types; } } augment "/sn:subscription-modified" { description "This augmentation adds many yang datastore specific objects to the notification that a subscription has been modified."; uses update-policy; uses update-qos; Clemm, et al. Expires April 5, 2018 [Page 46] Internet-Draft YANG-Push October 2017 } 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; } } augment "/sn:subscription-config/sn:subscription" { description "This augmentation adds many yang datastore specific objects which can be configured as opposed to established via RPC."; uses update-policy; uses update-qos; } augment "/sn:subscription-config/sn:subscription/sn:target" { description "This augmentation adds the datastore to the selection filtering criteria for a subscription."; case datastore { uses datastore-criteria; } } augment "/sn:subscriptions/sn:subscription" { yp:notifiable-on-change true; description "This augmentation adds many datastore specific objects to a subscription."; uses update-policy; uses update-qos; } 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; } } /* YANG Parser Pyang crashing on syntax below, due to fixed bug https://github.com/mbj4668/pyang/issues/300 deviation "/sn:subscriptions/sn:subscription/sn:receivers/" + "sn:receiver/sn:pushed-notifications" { deviate add { yp:notifiable-on-change false; Clemm, et al. Expires April 5, 2018 [Page 47] Internet-Draft YANG-Push October 2017 } } deviation "/sn:subscriptions/sn:subscription/sn:receivers/" + "sn:receiver/sn:excluded-notifications" { deviate add { yp:notifiable-on-change false; } } YANG Parser Pyang crashing on syntax above */ } 6. IANA Considerations 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-08.txt (RFC form) 7. Security Considerations All security considerations from [subscribe] are relevant for datastores. In addition there are specific security considerations for receivers defined in Section 3.9 If the access control permissions on subscribed YANG nodes change during the lifecycle of a subscription, a publisher MUST either transparently conform to the new access control permissions, or must terminate or restart the subscriptions so that new access control permissions are re-established. The NETCONF Authorization Control Model SHOULD be used to restrict the delivery of YANG nodes for which the receiver has no access. Clemm, et al. Expires April 5, 2018 [Page 48] Internet-Draft YANG-Push October 2017 8. Acknowledgments For their valuable comments, discussions, and feedback, we wish to acknowledge Tim Jenkins, Kent Watsen, Susan Hares, Yang Geng, Peipei Guo, Michael Scharf, Sharon Chisholm, and Guangying Zheng. 9. References 9.1. Normative References [revised-datastores] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture", draft-ietf-netmod-revised-datastores-04 (work in progress), August 2017. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC6020] Bjorklund, M., Ed., "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, . [RFC6536bis] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", draft-ietf- netconf-rfc6536bis-05 (work in progress), September 2017. [RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module Library", RFC 7895, DOI 10.17487/RFC7895, June 2016, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016, . Clemm, et al. Expires April 5, 2018 [Page 49] Internet-Draft YANG-Push October 2017 [RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch Media Type", RFC 8072, DOI 10.17487/RFC8072, February 2017, . [subscribe] Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A., and E. Nilsen-Nygaard, "Custom Subscription to Event Notifications", draft-ietf-netconf-subscribed- notifications-04 (work in progress), September 2017. 9.2. Informative References [netconf-notif] Gonzalez Prieto, A., Clemm, A., Voit, E., Nilsen-Nygaard, E., and A. Tripathy, "NETCONF Support for Event Notifications", September 2017. [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC7223] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, . [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements for Subscription to YANG Datastores", RFC 7923, DOI 10.17487/RFC7923, June 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . Appendix A. Changes between revisions (To be removed by RFC editor prior to publication) v09 - v10 o Returned to the explicit filter subtyping of v00-v05 o identityref to ds:datastore made explicit Clemm, et al. Expires April 5, 2018 [Page 50] Internet-Draft YANG-Push October 2017 o Returned ability to modify a selection filter via RPC. v08 - v09 o Minor tweaks cleaning up text, removing appendicies, and making reference to revised-datastores. o Subscription-id optional in push updates, except when encoded in RFC5277, Section 4 one-way notification. o Finished adding the text descibing the resynch subscription RPC. o Removed relationships to other drafts and future technology appendicies as this work is being explored elsewhere. o Deferred the multi-line card issue to new drafts o Simplified the NACM interactions. v07 - v08 o Updated YANG models with minor tweaks to accommodate changes of ietf-subscribed-notifications. v06 - v07 o Clarifying text tweaks. o Clarification that filters act as selectors for subscribed data nodes; support for value filters not included but possible as a future extension o Filters don't have to be matched to existing YANG objects v05 - v06 o Security considerations updated. o Base YANG model in [subscribe] updated as part of move to identities, YANG augmentations in this doc matched up o Terms refined and text updates throughout o Appendix talking about relationship to other drafts added. o Datastore replaces stream o Definitions of filters improved Clemm, et al. Expires April 5, 2018 [Page 51] Internet-Draft YANG-Push October 2017 v04 to v05 o Referenced based subscription document changed to Subscribed Notifications from 5277bis. o Getting operational data from filters o Extension notifiable-on-change added o New appendix on potential futures. Moved text into there from several drafts. o Subscription configuration section now just includes changed parameters from Subscribed Notifications o Subscription monitoring moved into Subscribed Notifications o New error and hint mechanisms included in text and in the yang model. o Updated examples based on the error definitions o Groupings updated for consistency o Text updates throughout v03 to v04 o Updates-not-sent flag added o Not notifiable extension added o Dampening period is for whole subscription, not single objects o Moved start/stop into rfc5277bis o Client and Server changed to subscriber, publisher, and receiver o Anchor time for periodic o Message format for synchronization (i.e. synch-on-start) o Material moved into 5277bis o QoS parameters supported, by not allowed to be modified by RPC o Text updates throughout Clemm, et al. Expires April 5, 2018 [Page 52] Internet-Draft YANG-Push October 2017 Authors' Addresses Alexander Clemm Huawei Email: ludwig@clemm.org Eric Voit Cisco Systems Email: evoit@cisco.com Alberto Gonzalez Prieto VMware Email: agonzalezpri@vmware.com Ambika Prasad Tripathy Cisco Systems Email: ambtripa@cisco.com Einar Nilsen-Nygaard Cisco Systems Email: einarnn@cisco.com Andy Bierman YumaWorks Email: andy@yumaworks.com Balazs Lengyel Ericsson Email: balazs.lengyel@ericsson.com Clemm, et al. Expires April 5, 2018 [Page 53]