NETCONF A. Clemm Internet-Draft A. Gonzalez Prieto Intended status: Standards Track E. Voit Expires: March 15, 2017 E. Nilsen-Nygaard A. Tripathy Cisco Systems S. Chisholm Ciena H. Trevino Cisco Systems September 11, 2016 Subscribing to Event Notifications draft-ietf-netconf-rfc5277bis-00 Abstract This document defines capabilities and operations for providing asynchronous message notification delivery for notifications, such as those defined using YANG. Notification delivery can occur over a variety of protocols used commonly in conjunction with YANG, such as NETCONF and RESTCONF. The capabilities and operations defined in this document along with their mapping onto NETCONF transport are intended to replace RFC 5277. 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 http://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 March 15, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. Clemm, et al. Expires March 15, 2017 [Page 1] Internet-Draft Event Notifications September 2016 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Solution Overview . . . . . . . . . . . . . . . . . . . . 5 2. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Event Streams . . . . . . . . . . . . . . . . . . . . . . 6 2.2. Event Stream Discovery . . . . . . . . . . . . . . . . . 7 2.3. Filters . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4. Subscription State Model at the Event Server . . . . . . 7 3. Data Model Trees for Event Notifications . . . . . . . . . . 8 4. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . . . 12 4.1. Establishing a Subscription . . . . . . . . . . . . . . . 13 4.2. Modifying a Subscription . . . . . . . . . . . . . . . . 13 4.3. Deleting a Subscription . . . . . . . . . . . . . . . . . 14 5. Configured Subscriptions . . . . . . . . . . . . . . . . . . 15 5.1. Creating a Configured Subscription . . . . . . . . . . . 15 5.2. Establishing a Configured Subscription . . . . . . . . . 15 5.3. Modifying a Configured Subscription . . . . . . . . . . . 17 5.4. Deleting a Configured Subscription . . . . . . . . . . . 17 6. Event (Data Plane) Notifications . . . . . . . . . . . . . . 18 7. Control Plane Notifications . . . . . . . . . . . . . . . . . 20 7.1. replayComplete . . . . . . . . . . . . . . . . . . . . . 20 7.2. notificationComplete . . . . . . . . . . . . . . . . . . 20 7.3. subscription-started . . . . . . . . . . . . . . . . . . 20 7.4. subscription-modified . . . . . . . . . . . . . . . . . . 21 7.5. subscription-terminated . . . . . . . . . . . . . . . . . 21 7.6. subscription-suspended . . . . . . . . . . . . . . . . . 21 7.7. subscription-resumed . . . . . . . . . . . . . . . . . . 21 8. Data Model for Event Notifications . . . . . . . . . . . . . 21 9. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 39 10. Security Considerations . . . . . . . . . . . . . . . . . . . 40 11. Issues that are currently being worked and resolved . . . . . 41 11.1. Unresolved and yet-to-be addressed issues . . . . . . . 41 11.2. Agreement in principal . . . . . . . . . . . . . . . . . 41 11.3. Resolved Issues . . . . . . . . . . . . . . . . . . . . 42 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42 Clemm, et al. Expires March 15, 2017 [Page 2] Internet-Draft Event Notifications September 2016 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 13.1. Normative References . . . . . . . . . . . . . . . . . . 42 13.2. Informative References . . . . . . . . . . . . . . . . . 43 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 1. Introduction This document defines mechanisms that provide an asynchronous message notification delivery service in a protocol-agnostic manner. This document defines capabilities and operations for providing asynchronous message notification delivery for notifications including those necessary to establish, monitor, and support subscriptions to notification delivery. Notification delivery can occur over a variety of protocols used commonly in conjunction with YANG, such as NETCONF [RFC6241] (defined in [I-D.ietf-netconf-netconf-event-notif]) and Restconf [I-D.ietf-netconf-restconf] (defined in [I-D.ietf-netconf-restconf-notif]). The capabilities and operations defined in this document are intended to replace RFC 5277, along with their mapping onto NETCONF transport. 1.1. Motivation The motivation for this work is to enable the sending of asynchronous notification messages that are consistent with the data model (content) and security model used within a NETCONF implementation. [RFC5277] defines a notification mechanism for NETCONF. However, there are various limitations: o Each subscription requires a separate NETCONF connection, which is wasteful. o The only mechanism to terminate a subscription is terminating the underlying NETCONF connection. o No ability to modify subscriptions once they have been created. o No ability to notify the receiver of a subscription if the server is dropping events. o No mechanism to monitor subscriptions. o No alternative mechanism to create subscriptions via RPCs. Thus the lifetime of the subscription is limited by that of the underlaying NETCONF session. Clemm, et al. Expires March 15, 2017 [Page 3] Internet-Draft Event Notifications September 2016 o Predates YANG and defines RPCs, notifications, and data nodes outside of the YANG framework. The scope of the work aims at meeting the following operational needs: o Ability to dynamically or statically subscribe to event notifications available on an event server. o Ability to negotiate acceptable dynamic subscription parameters. o Ability to filter the subset of notifications to be pushed with stream-specific semantics. o Ability for the notification payload to be interpreted independently of the transport protocol. (In other words, the encoded notification fully describes itself.) o Mechanism to communicate the notifications. o Ability to replay locally logged notifications. 1.2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Configured subscription: A subscription installed via a configuration interface which persists across reboots. Dynamic subscription: A subscription agreed between subscriber and event server via create, establish, modify, and delete RPC control plane signaling messages. Event: Something that happens that may be of interest. (e.g., a configuration change, a fault, a change in status, crossing a threshold, or an external input to the system.) Event notification: A message sent by a server to a receiver indicating that an event (of interest to the subscriber) has occurred. Events can trigger notifications if an interested party has subscribed to the stream(s) it belongs to. Event server: The server being subscribed to, which serves an event subscription. Clemm, et al. Expires March 15, 2017 [Page 4] Internet-Draft Event Notifications September 2016 Filter: Evaluation criteria, which may be applied against a targeted set of objects/events in a subscription. Information traverses the filter only if specified filter criteria are met. NACM: NETCONF Access Control Model. OAM: Operations, Administration, Maintenance. Publisher: An entity responsible for streaming Event Notifications per the terms of a Subscriptions RPC: Remote Procedure Call. Stream (also referred to as "event stream"): A continuous ordered set of events grouped under an explicit criteria. Subscriber: An entity able to request and negotiate a contract for the receipt of event notifications from a NETCONF server. Receiver: A target to which an event server pushes event notifications. In many deployments, the receiver and subscriber will be the same entity. Subscription: A contract between a subscriber and an event server, stipulating which information the receiver wishes to have pushed from the server without the need for further solicitation. 1.3. Solution Overview This document describes mechanisms for subscribing and receiving event notifications from an event server. This document builds on top of the capabilities defined in [RFC5277], extending them, and generalizing them to be protocol-agnostic. The enhancements over RFC 5277 include the ability to terminate subscriptions without terminating the client session, to modify existing subscriptions, and to have multiple subscriptions on a NETCONF session. These enhancements do not affect existing RFC 5277 clients that do not support these particular subscription requirements. The solution supports subscribing to event notifications using two mechanisms. 1. Dynamic subscriptions, where a client initiates a subscription negotiation with an event server via RPC. A client initiates a negotiation by issuing a subscription request. If the event Clemm, et al. Expires March 15, 2017 [Page 5] Internet-Draft Event Notifications September 2016 server wants to serve this request, it will accept it, and then start pushing event notifications as negotiated. If the event server does not wish to serve it as requested, it may respond with subscription parameters which it would have accepted. 2. Configured subscriptions, which is an optional mechanism that enables managing subscriptions via a configuration interface so that an event server sends event notifications to a configured receiver(s). Some key characteristics of configured and dynamic subscriptions include: o The lifetime of a dynamic subscription is limited by the lifetime of the subscriber session used to establish it. Typically loss of the transport session tears down any dependent dynamic subscriptions. o The lifetime of a configured subscription is driven by configuration being present on the running configuration. This implies configured subscriptions persist across reboots, and persists even when transport is unavailable. This also means configured subscriptions do not support negotiation. o Subscriptions can be modified or terminated at any point of their lifetime. configured subscriptions can be modified by any configuration client with write rights on the configuration of the subscription. Note that there is no mixing-and-matching of dynamic and configured subscriptions. Specifically, a configured subscription cannot be modified or deleted using RPC. Similarly, a subscription created via RPC cannot be modified through configuration operations. The event server may decide to terminate a dynamic subscription at any time. Similarly, it may decide to temporarily suspend the sending of event notifications for either configured or dynamic subscriptions. Such termination or suspension may be driven by the server running out of resources to serve the subscription, or by internal errors on the server. 2. Solution 2.1. Event Streams An event stream is a set of events available for subscription from a server. It is out of the scope of this document to identify a) how Clemm, et al. Expires March 15, 2017 [Page 6] Internet-Draft Event Notifications September 2016 streams are defined, b) how events are defined/generated, and c) how events are assigned to streams. That said, some event streams will be standardized whereas others may be vendor specific. One standardized event stream is the "NETCONF" notification event stream. The NETCONF event stream contains all NETCONF XML event notifications supported by the NETCONF server, except for those belonging only to streams that explicitly indicate that they must be excluded from the NETCONF stream, such as notifications that serve OAM and signaling purposes. The following is a high-level description of the flow of a notification. Note that it does not mandate and/or preclude an implementation. As events are raised, they are assigned to streams. An event may be assigned to multiple streams. The event is distributed to subscribers and receivers based on the current subscriptions and access control. Access control is needed because if any receiver of that subscription does not have permission to receive an event, then it never makes it into a notification, and processing of the event is completed for that subscription. 2.2. Event Stream Discovery A server maintains a list of available event streams as operational data. This list contains both standardized and vendor-specific event streams. A client can retrieve this list like any other YANG-defined data, for example using the operation when using NETCONF. 2.3. Filters An event server implementation SHOULD support the ability to perform filtering of notification records per RFC 5277. (TODO: since 5277 is to be obsoleted, we should describe the filter here.) 2.4. Subscription State Model at the Event Server Below is the state machine of a subscription for the event server. It is important to note that a subscription doesn't exist at the event server until it is accepted and made active. The mere request by a subscriber to establish a subscription is insufficient for that asserted subscription to be externally visible via this state machine. Clemm, et al. Expires March 15, 2017 [Page 7] Internet-Draft Event Notifications September 2016 .-------. | start | '-------' | establish | | .----------modify--------------. v v ' .-----------. .-----------. .--------. | |------>suspend------->| | modify '| active | | suspended | '--------->| |<----resume----<------| | '-----------' '-----------' | | delete delete | | v | .-------. | | end |<-----------------------------' '-------' Figure 1: Subscription states at event server Of interest in this state machine are the following: o Successful or requests put the subscription into an active state. o Failed requests will leave the subscription in its previous state, with no visible change to any streaming updates. o A request will delete the entire subscription. 3. Data Model Trees for Event Notifications The YANG data model for event notifications is depicted in this section. module: ietf-event-notifications +--ro streams | +--ro stream* notif:stream +--rw filters | +--rw filter* [filter-id] | +--rw filter-id filter-id | +--rw (filter-type)? | +--:(rfc5277) Clemm, et al. Expires March 15, 2017 [Page 8] Internet-Draft Event Notifications September 2016 | +--rw filter +--rw subscription-config {configured-subscriptions}? | +--rw subscription* [subscription-id] | +--rw subscription-id subscription-id | +--rw stream? stream | +--rw (filter-type)? | | +--:(rfc5277) | | | +--rw filter | | +--:(by-reference) | | +--rw filter-ref? filter-ref | +--rw startTime? yang:date-and-time | +--rw stopTime? yang:date-and-time | +--rw encoding? encoding | +--rw receivers | | +--rw receiver* [address] | | +--rw address inet:host | | +--rw port inet:port-number | | +--rw protocol? transport-protocol | +--rw (push-source)? | +--:(interface-originated) | | +--rw source-interface? if:interface-ref | +--:(address-originated) | +--rw source-vrf? uint32 | +--rw source-address inet:ip-address-no-zone +--ro subscriptions +--ro subscription* [subscription-id] +--ro subscription-id subscription-id +--ro configured-subscription? empty {configured-subscriptions}? +--ro subscription-status? subscription-status +--ro stream? stream +--ro (filter-type)? | +--:(rfc5277) | | +--ro filter | +--:(by-reference) | +--ro filter-ref? filter-ref +--ro startTime? yang:date-and-time +--ro stopTime? yang:date-and-time +--ro encoding? encoding +--ro receivers | +--ro receiver* [address] | +--ro address inet:host | +--ro port inet:port-number | +--ro protocol? transport-protocol +--ro (push-source)? +--:(interface-originated) | +--ro source-interface? if:interface-ref +--:(address-originated) +--ro source-vrf? uint32 Clemm, et al. Expires March 15, 2017 [Page 9] Internet-Draft Event Notifications September 2016 +--ro source-address inet:ip-address-no-zone rpcs: +---x establish-subscription | +---w input | | +---w stream? stream | | +---w (filter-type)? | | | +--:(rfc5277) | | | | +---w filter | | | +--:(by-reference) | | | +---w filter-ref? filter-ref | | +---w startTime? yang:date-and-time | | +---w stopTime? yang:date-and-time | | +---w encoding? encoding | +--ro output | +--ro subscription-result subscription-result | +--ro (result)? | +--:(success) | | +--ro subscription-id subscription-id | +--:(no-success) | +--ro stream? stream | +--ro (filter-type)? | | +--:(rfc5277) | | | +--ro filter | | +--:(by-reference) | | +--ro filter-ref? filter-ref | +--ro startTime? yang:date-and-time | +--ro stopTime? yang:date-and-time | +--ro encoding? encoding +---x modify-subscription | +---w input | | +---w subscription-id? subscription-id | | +---w stream? stream | | +---w (filter-type)? | | | +--:(rfc5277) | | | | +---w filter | | | +--:(by-reference) | | | +---w filter-ref? filter-ref | | +---w startTime? yang:date-and-time | | +---w stopTime? yang:date-and-time | | +---w encoding? encoding | +--ro output | +--ro subscription-result subscription-result | +--ro (result)? | +--:(success) | | +--ro subscription-id subscription-id | +--:(no-success) | +--ro stream? stream | +--ro (filter-type)? Clemm, et al. Expires March 15, 2017 [Page 10] Internet-Draft Event Notifications September 2016 | | +--:(rfc5277) | | | +--ro filter | | +--:(by-reference) | | +--ro filter-ref? filter-ref | +--ro startTime? yang:date-and-time | +--ro stopTime? yang:date-and-time | +--ro encoding? encoding +---x delete-subscription +---w input | +---w subscription-id subscription-id +--ro output +--ro subscription-result subscription-result notifications: +---n replay-complete | +--ro subscription-id subscription-id +---n notification-complete | +--ro subscription-id subscription-id +---n subscription-started | +--ro subscription-id subscription-id | +--ro stream? stream | +--ro (filter-type)? | | +--:(rfc5277) | | | +--ro filter | | +--:(by-reference) | | +--ro filter-ref? filter-ref | +--ro startTime? yang:date-and-time | +--ro stopTime? yang:date-and-time | +--ro encoding? encoding +---n subscription-suspended | +--ro subscription-id subscription-id | +--ro reason? subscription-susp-reason +---n subscription-resumed | +--ro subscription-id subscription-id +---n subscription-modified | +--ro subscription-id subscription-id | +--ro stream? stream | +--ro (filter-type)? | | +--:(rfc5277) | | | +--ro filter | | +--:(by-reference) | | +--ro filter-ref? filter-ref | +--ro startTime? yang:date-and-time | +--ro stopTime? yang:date-and-time | +--ro encoding? encoding +---n subscription-terminated | +--ro subscription-id subscription-id | +--ro reason? subscription-term-reason +---n added-to-subscription Clemm, et al. Expires March 15, 2017 [Page 11] Internet-Draft Event Notifications September 2016 | +--ro subscription-id subscription-id | +--ro stream? stream | +--ro (filter-type)? | | +--:(rfc5277) | | | +--ro filter | | +--:(by-reference) | | +--ro filter-ref? filter-ref | +--ro startTime? yang:date-and-time | +--ro stopTime? yang:date-and-time | +--ro encoding? encoding +---n removed-from-subscription +--ro subscription-id subscription-id The data model is structured as follows: o "Streams" contains a list of event streams that are supported by the event server and that can be subscribed to. o "Filters" contains a configurable list of filters that can be applied to a subscription. This allows users to reference an existing filter definition as an alternative to defining a filter inline for each subscription. o "Subscription-config" contains the configuration of configured subscriptions. The parameters of each configured subscription are equivalent to the parameters of a dynamic subscription and use the same groupings. In addition, the configured subscriptions specify intended receivers and the push source from which to send the stream of notification messages. o "Subscriptions" contains a list of all subscriptions on an event server, both configured and dynamic. It can be used do retrieve information about the subscriptions which an event server is serving. The data model also contains a number of notifications that allow an event server to signal to the client information about a subscription. Finally, the data model contains a number of RPC definitions that are used to manage dynamic subscriptions. 4. Dynamic Subscriptions Dynamic subscriptions are managed via RPC. Clemm, et al. Expires March 15, 2017 [Page 12] Internet-Draft Event Notifications September 2016 4.1. Establishing a Subscription This operation is an evolution of the "create-subscription" operation defined in RFC 5277. It allows a subscriber to request the creation of a subscription both via RPC and configuration operations. When invoking the RPC, establish-subscription permits negotiating the subscription terms, changing them dynamically. The input parameters of the operation are those of create subscription plus: o filter-ref: filters that have been previously (and separately) configured can be referenced by a subscription. This mechanism enables the reuse of filters. o encoding: by default, updates are encoded using XML. Other encodings may be supported, such as JSON. If the event server cannot satisfy the request, it sends a negative element. If the client has no authorization to establish the subscription, the indicates an authorization error. If the request is rejected because the server is not able to serve it, the server SHOULD include in the returned error what subscription parameters would have been accepted for the request when it was processed. However, they is no guarantee that subsequent requests with those parameters for this client or others will be accepted. For instance, consider a subscription from [I-D.ietf-netconf-yang-push], which augments the establish- subscription with some additional parameters, including "period". Subscription requests will fail if a filter with invalid syntax is provided or if the name of a non-existent stream is provided. 4.2. Modifying a Subscription This operation permits modifying the terms of a subscription previously established. Subscriptions created by configuration cannot be modified. Dynamic subscriptions can be modified one or multiple times. If the server accepts the request, it immediately starts sending events based on the new terms, completely ignoring the previous ones. If the server rejects the request, the subscription remains as prior to the request. That is, the request has no impact whatsoever. The contents of negative responses to modify- subscription requests are the same as in establish subscription requests. Clemm, et al. Expires March 15, 2017 [Page 13] Internet-Draft Event Notifications September 2016 Dynamic subscriptions established via RPC can only be modified (or deleted) via RPC using the same session used to establish it. Configured subscriptions cannot be modified (or deleted) using RPCs. Instead, configured subscriptions are modified (or deleted) as part of regular configuration operations. Servers MUST reject any attempts to modify (or delete) configured subscriptions via RPC. The parameters to modify-subscription are those of establish- subscription plus a mandatory subscription-id. If the event server can satisfy the request, the server sends a positive subscription-result. This response is like that to an establish-subscription request without the subscription-id, which would be redundant. If the event server cannot satisfy the request, the server sends a negative subscription-result. Its contents and semantics are identical to those to an establish-subscription request. 4.3. Deleting a Subscription This operation permits canceling a subscription previously established. Created subscriptions cannot be explicitly deleted. If the server accepts the request, it immediately stops sending events for the subscription. If the server rejects the request, all subscriptions remain as prior to the request. That is, the request has no impact whatsoever. A request may be rejected because the provided subscription identifier is incorrect. Subscriptions created via RPC can only be deleted via RPC using the same session used for establishment. Configured subscriptions cannot be deleted using RPCs. Instead, configured subscriptions are deleted as part of regular configuration operations. Servers MUST reject any RPC attempt to delete configured subscriptions. The only parameter to delete-subscription is the identifier of the subscription to delete. If the event server can satisfy the request, the server sends an OK element. If the event server cannot satisfy the request, the server sends an error-rpc element. Clemm, et al. Expires March 15, 2017 [Page 14] Internet-Draft Event Notifications September 2016 5. Configured Subscriptions A configured subscription is a subscription installed via a configuration interface. Configured subscriptions persist across reboots, and persist even when transport is unavailable. This also means configured subscriptions do not support negotiation. Configured subscriptions can be modified by any configuration client with write rights on the configuration of the subscription. Subscriptions can be modified or terminated at any point of their lifetime. Supporting configured subscriptions is optional and advertised using the "configured-subscriptions" feature. In addition to subscription parameters that apply to dynamic subscriptions, the following additional parameters apply to configured subscriptions: o One or more receiver IP addresses (and corresponding ports) intended as the destination for push updates for each subscription. In addition the transport protocol for each destination may be defined. o Optional parameters to identify an egress interface or IP address / VRF where a subscription updates should be pushed from the publisher. 5.1. Creating a Configured Subscription Configured subscriptions cannot be created via configuration operations. New clients should use the mechanisms described in Section 5.2 for establishing configured subscriptions. 5.2. Establishing a Configured Subscription Subscriptions can be established using configuration operations against the top-level subtree subscription-config. There are two key differences between RPC and configuration operations for subscription establishment. Firstly, configuration operations do not support negotiation while RPCs do. Secondly, while RPCs mandate that the client establishing the subscription is the only receiver of the notifications, configuration operations permit specifying receivers independent of any tracked subscriber. Immediately after a subscription is successfully established, the server sends to the Clemm, et al. Expires March 15, 2017 [Page 15] Internet-Draft Event Notifications September 2016 receivers a control-plane notification stating the subscription has been established (subscription-started). Because there is no explicit association with an existing transport session, configured configuration operations require additional parameters to indicate the receivers of the notifications and possibly the source of the notifications (i.e., a specific interface or server address). For example at subscription establishment, a NETCONF client may send: 1922 foo
1.2.3.4
1234 Figure 2: Establish configured subscription if the request is accepted, the server would reply: Clemm, et al. Expires March 15, 2017 [Page 16] Internet-Draft Event Notifications September 2016 Figure 3: Response to a successful configured subscription establishment if the request is not accepted because the server cannot serve it, the server may reply: application resource-denied error Temporarily the server cannot serve this subscription due to the current workload. Figure 4: Response to a failed configured subscription establishment 5.3. Modifying a Configured Subscription Configured subscriptions can be modified using configuration operations against the top-level subtree subscription-config. Immediately after a subscription is successfully modified, the server sends to the existing receivers a control-plane notification stating the subscription has been modified (i.e., subscription-modified). If the modification involved adding and/or removing receivers, those modified receivers are sent control-plane notifications, indicating they have been added (i.e, added-to-subscription, with the same contents as a modified-subscription) or removed (i.e., removed-from- subscription) 5.4. Deleting a Configured Subscription Subscriptions can be deleted using configuration operations against the top-level subtree subscription-config. For example, in RESTCONF: Clemm, et al. Expires March 15, 2017 [Page 17] Internet-Draft Event Notifications September 2016 DELETE /subscription-config/subscription=1922 HTTP/1.1 Host: example.com HTTP/1.1 204 No Content Date: Sun, 24 Jul 2016 11:23:40 GMT Server: example-server Figure 5: Deleting a configured subscription Immediately after a subscription is successfully deleted, the event server sends to the receivers a control-plane notification stating the subscription has been terminated (subscription-terminated). 6. Event (Data Plane) Notifications Once a subscription has been set up, the event server sends (asynchronously) the event notifications from the subscribed stream. We refer to these as data plane notifications. For dynamic subscriptions set up via RPC operations, event notifications are sent over the session used to create or establish the subscription. For configured subscriptions, event notifications are sent over the specified connections. An event notification is sent to the receiver(s) when an event of interest (i.e., meeting the specified filtering criteria) has occurred. An event notification is a complete and well-formed XML document. Note that is not a Remote Procedure Call (RPC) method but rather the top-level element identifying the one-way message as a notification. Note that event notifications never trigger responses. The event notification always includes an element. It is the time the event was generated by the event source. This parameter is of type dateTime and compliant to [RFC3339]. Implementations must support time zones. The event notification also contains notification-specific tagged content, if any. With the exception of , the content of the notification is beyond the scope of this document. For the encodings other than XML, notifications include an additional XML element so that the notification is a well-formed XML. The element is , E.g., . That element contains the notification contents in the desired encoding The following is an example of an event notification from [RFC6020]: Clemm, et al. Expires March 15, 2017 [Page 18] Internet-Draft Event Notifications September 2016 notification link-failure { description "A link failure has been detected"; leaf if-name { type leafref { path "/interface/name"; } } leaf if-admin-status { type admin-status; } leaf if-oper-status { type oper-status; } } Figure 6: Definition of a data plane notification 2007-09-01T10:00:00Z so-1/2/3.0 up down Figure 7: Data plane notification The equivalent using json encoding would be 2007-09-01T10:00:00Z { "acme-system:link-failure": { "if-name": "so-1/2/3.0", "if-admin-status": "up", "if-oper-status": "down " } } Figure 8: Data plane notification using JSON encoding Clemm, et al. Expires March 15, 2017 [Page 19] Internet-Draft Event Notifications September 2016 7. Control Plane Notifications In addition to data plane notifications, a server may send control plane notifications to indicate to receivers that an event related to the subscription management has occurred. Control plane notifications are unlike other notifications in that they are not general-purpose notifications. They cannot be filtered out, and they are delivered only to the receiver of a subscription. The definition of control plane notifications is distinct from other notifications by making use of a YANG extension tagging them as control plane notification. Control plane notifications include indications that a replay of notifications has been completed, that a subscription is done sending notifications because an end time has been reached, and that a subscription has started, been modified, been terminated, or been suspended. They are described in the following subsections. 7.1. replayComplete This notification is originally defined in [RFC5277]. It is sent to indicate that all of the replay notifications have been sent and must not be sent for any other reason. In the case of a subscription without a stop time, after the notification has been sent, it can be expected that any notifications generated since the start of the subscription creation will be sent, followed by notifications as they arise naturally within the system. 7.2. notificationComplete This notification is originally defined in [RFC5277]. It is sent to indicate that a subscription, which includes a stop time, has finished passing events. 7.3. subscription-started This notification indicates that a configured subscription has started and data updates are beginning to be sent. This notification includes the parameters of the subscription, except for the receiver(s) addressing information and push-source information. Note that for RPC-based subscriptions, no such notifications are sent. Clemm, et al. Expires March 15, 2017 [Page 20] Internet-Draft Event Notifications September 2016 7.4. subscription-modified This notification indicates that a configured subscription has been modified successfully. This notification includes the parameters of the subscription, except for the receiver(s) addressing information and push-source information. Note that for RPC-based subscriptions, no such notifications are sent. 7.5. subscription-terminated This notification indicates that a subscription has been terminated. The notification includes the reason for the termination. A subscription may be terminated by a server or by a client. The server may decide to terminate a subscription when it is running out of resources for serving it, an internal error occurs, etc. Server- driven terminations are notified to all receivers. The management plane can also terminate configured subscriptions using configuration operations. Clients can terminate via RPC subscriptions established via RPC. In such cases, no subscription-terminated notifications are sent. 7.6. subscription-suspended This notification indicates that a server has suspended a subscription. The notification includes the reason for the suspension. A possible reason is the lack of resources to serve it. No further data plane notifications will be sent until the subscription resumes. Suspensions are notified to the subscriber (in the case of dynamic subscriptions) and all receivers (in the case of configured subscriptions). 7.7. subscription-resumed This notification indicates that a previously suspended dubscription has been resumed. Data plane notifications generated in the future will be sent after the subscription terms. Resumptions are notified to the subscriber (in the case of dynamic subscriptions) and all receivers (in the case of configured subscriptions). 8. Data Model for Event Notifications file "ietf-event-notifications@2016-09-11.yang" module ietf-event-notifications { namespace "urn:ietf:params:xml:ns:yang:ietf-event-notifications"; Clemm, et al. Expires March 15, 2017 [Page 21] Internet-Draft Event Notifications September 2016 prefix notif-bis; import ietf-inet-types { prefix inet; } import ietf-5277-netmod { prefix netmod-notif; } import ietf-5277-netconf { prefix notif; } import ietf-interfaces { prefix if; } organization "IETF"; contact "WG Web: WG List: WG Chair: Mahesh Jethanandani WG Chair: Mehmet Ersue Editor: Alexander Clemm Editor: Alberto Gonzalez Prieto Editor: Eric Voit Editor: Einar Nilsen-Nygaard Editor: Ambika Prasad Tripathy Editor: Sharon Chisholm Editor: Hector Trevino 9. Backwards Compatibility Capabilities are advertised in messages sent by each peer during session establishment [RFC6241]. Servers supporting the features in this document must advertise both capabilities "urn:ietf:params:netconf:capability:notification:1.0" and "urn:ietf:params:netconf:capability:notification:1.1". An example of a hello message by a server during session establishment would be: urn:ietf:params:xml:ns:netconf:base:1.0 urn:ietf:params:netconf:capability:startup:1.0 urn:ietf:params:netconf:capability:notification:1.0 urn:ietf:params:netconf:capability:notification:1.1 4 Figure 9: Hello message Clients that only support [RFC5277] recognize capability "urn:ietf:params:netconf:capability:notification:1.0" and ignore capability "urn:ietf:params:netconf:capability:notification:1.1". Clemm, et al. Expires March 15, 2017 [Page 39] Internet-Draft Event Notifications September 2016 This allows them interacting with the server as per [RFC5277]. Clients that support the features in this document recognize both capabilities. This allows them interacting with the server as per this document. Note that to support backwards compatibility, the yang models in this document include two types of naming conventions. That used in [RFC5277], e.g., replayComplete; and that commonly used in yang models, e.g., subscription-started. 10. Security Considerations The security considerations from the base NETCONF document [RFC6241] also apply to the notification capability. The elements are never sent before the transport layer and the NETCONF layer, including capabilities exchange, have been established and the manager has been identified and authenticated. A secure transport must be used and the server must ensure that the user has sufficient authorization to perform the function they are requesting against the specific subset of NETCONF content involved. When a is received that refers to the content defined in this memo, clients should only be able to view the content for which they have sufficient privileges. and operations can be considered like deferred , and the content that different users can access may vary. This different access is reflected in the that different users are able to subscribe to. The contents of notifications, as well as the names of event streams, may contain sensitive information and care should be taken to ensure that they are viewed only by authorized users. The NETCONF server MUST NOT include any content in a notification that the user is not authorized to view. If a malicious or buggy NETCONF client sends a number of requests, then these subscriptions accumulate and may use up system resources. In such a situation, subscriptions can be terminated by terminating the suspect underlying NETCONF sessions using the operation. If the client uses , the server can also suspend or terminate subscriptions with per-subscription granularity. A subscription could be configured on another receiver's behalf, with the goal of flooding that receiver with updates. One or more publishers could be used to overwhelm a receiver, which doesn't even support subscriptions. Clients that do not want pushed data need Clemm, et al. Expires March 15, 2017 [Page 40] Internet-Draft Event Notifications September 2016 only terminate or refuse any transport sessions from the publisher. In addition, the NETCONF Authorization Control Model [RFC6536] SHOULD be used to control and restrict authorization of subscription configuration. This control models permits specifying per-user permissions to receive specific event notification types. The permissions are specified as a set of access control rules. Note that streams can define additional authorization requirements. For instance, in [I-D.ietf-netconf-yang-push], each of the elements in its data plane notifications must also go through access control. 11. Issues that are currently being worked and resolved 11.1. Unresolved and yet-to-be addressed issues EN1 - Definition of basic set of Stream types. What streams are provided and what do they contain (includes default 5277 stream). EN2 - Clarify interplay between filter definitions and different streams. Includes information in subtrees of event payloads. EN3 - Mechanisms for diagnostics, e.g. deal with dropped updates, monitoring when they occur, etc EN4 - How to allow for seamless integration with non-standard encodings and transports (like GPB/GRPC). Specify requirements encoding and transport must meet, provide examples. EN7 - Detecting loss of a sequential update notification, and mechanisms to resend. Implications to transports must be thought through. 11.2. Agreement in principal EN6 - Stream discovery. Allow to discover additional stream properties. EN9 - Multiple receivers per Configured Subscription is ok. EN10 - Replay support will be provided for selected stream types (modify vs. delete) EN11 - Required layering security requirements/considerations will be added into the YANG model for Configured Subscriptions. It will be up to the transport to meet these requirements. EN12 - Test-only option for a subscription is desired. But it still needs to be defined. Clemm, et al. Expires March 15, 2017 [Page 41] Internet-Draft Event Notifications September 2016 EN13 - RFC6241 Subtree-filter definition in 5277bis cannot apply to elements of an event. Must explicitly define how 6241 doesn't apply filtering within a 5277bis event. EN14 - Ensure that Configured Subscriptions are fully defined in YANG model. 11.3. Resolved Issues EN5 - This draft obsoletes 5277, as opposed to being in parallel with it EN8 - No mandatory transport EN15 - Term for Dynamic and Static Subscriptions (move to "Configured") 12. Acknowledgments For their valuable comments, discussions, and feedback, we wish to acknowledge Andy Bierman, Yang Geng, Peipei Guo, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent Watsen, and Guangying Zheng. 13. References 13.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, . [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . Clemm, et al. Expires March 15, 2017 [Page 42] Internet-Draft Event Notifications September 2016 [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, . [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, . 13.2. Informative References [I-D.ietf-netconf-netconf-event-notif] Gonzalez Prieto, Alberto., Clemm, Alexander., Voit, Eric., Nilsen-Nygaard, E., Tripathy, A., Chisholm, S., and H. Trevino, "NETCONF support for event notifications", August 2016, . [I-D.ietf-netconf-restconf] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", I-D draft-ietf-netconf-restconf-13, April 2016. [I-D.ietf-netconf-restconf-notif] Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen- Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and HTTP transport for event notifications", August 2016, . [I-D.ietf-netconf-yang-push] Clemm, Alexander., Gonzalez Prieto, Alberto., Voit, Eric., Tripathy, A., and E. Nilsen-Nygaard, "Subscribing to YANG datastore push updates", June 2016, . Authors' Addresses Alexander Clemm Cisco Systems Email: ludwig@clemm.org Clemm, et al. Expires March 15, 2017 [Page 43] Internet-Draft Event Notifications September 2016 Alberto Gonzalez Prieto Cisco Systems Email: albertgo@cisco.com Eric Voit Cisco Systems Email: evoit@cisco.com Einar Nilsen-Nygaard Cisco Systems Email: einarnn@cisco.com Ambika Prasad Tripathy Cisco Systems Email: ambtripa@cisco.com Sharon Chisholm Ciena Email: schishol@ciena.com Hector Trevino Cisco Systems Email: htrevino@cisco.com Clemm, et al. Expires March 15, 2017 [Page 44]