Subscribing to Event Notifications

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 (defined in ) and Restconf (defined in ). The capabilities and operations defined in this document are intended to replace RFC 5277, along with their mapping onto NETCONF transport.

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. defines a notification mechanism for NETCONF. However, there are various limitations: Each subscription requires a separate NETCONF connection, which is wasteful. The only mechanism to terminate a subscription is terminating the underlying NETCONF connection. No ability to modify subscriptions once they have been created. No ability to notify the receiver of a subscription if the server is dropping events. No mechanism to monitor subscriptions. No alternative mechanism to create subscriptions via RPCs. Thus the lifetime of the subscription is limited by that of the underlaying NETCONF session. 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: Ability to dynamically or statically subscribe to event notifications available on an event server. Ability to negotiate acceptable dynamic subscription parameters. Ability to filter the subset of notifications to be pushed with stream-specific semantics. Ability for the notification payload to be interpreted independently of the transport protocol. (In other words, the encoded notification fully describes itself.) Mechanism to communicate the notifications. Ability to replay locally logged notifications.

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. 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. 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.

This document describes mechanisms for subscribing and receiving event notifications from an event server. This document builds on top of the capabilities defined in , 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. 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 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. 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: 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. 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. 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.

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 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.

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 <get> operation when using NETCONF.

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.)

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.

suspend------->| | modify '| active | | suspended | '--------->| |<----resume----<------| | '-----------' '-----------' | | delete delete | | v | .-------. | | end |<-----------------------------' '-------' ]]> Of interest in this state machine are the following: Successful <establish-subscription> or <modify-subscription> requests put the subscription into an active state. Failed <modify-subscription> requests will leave the subscription in its previous state, with no visible change to any streaming updates. A <delete-subscription> request will delete the entire subscription.

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) | +--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 +--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)? | | +--:(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 | +--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: "Streams" contains a list of event streams that are supported by the event server and that can be subscribed to. "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. "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. "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.

Dynamic subscriptions are managed via RPC.

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: filter-ref: filters that have been previously (and separately) configured can be referenced by a subscription. This mechanism enables the reuse of filters. 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 <subscription-result> element. If the client has no authorization to establish the subscription, the <subscription-result> 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 , 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.

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. 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.

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.

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: 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. Optional parameters to identify an egress interface or IP address / VRF where a subscription updates should be pushed from the publisher.

Configured subscriptions cannot be created via configuration operations. New clients should use the mechanisms described in for establishing configured subscriptions.

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 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:

<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0"> <edit-config> <target> <running/> </target> <subscription-config xmlns="urn:ietf:params:xml:ns:netconf:notification:1.1"> <subscription> <subscription-id> 1922 </subscription-id> <stream> foo </stream> <receiver> <address> 1.2.3.4 </address> <port> 1234 </port> </receiver> </subscription> </subscription-config> </edit-config> </rpc> if the request is accepted, the server would reply:

<rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <ok/> </rpc-reply> if the request is not accepted because the server cannot serve it, the server may reply:

<rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <rpc-error> <error-type>application</error-type> <error-tag>resource-denied</error-tag> <error-severity>error</error-severity> <error-message xml:lang="en"> Temporarily the server cannot serve this subscription due to the current workload. </error-message> </rpc-error> </rpc-reply>

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)

Subscriptions can be deleted using configuration operations against the top-level subtree subscription-config. For example, in RESTCONF:

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 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).

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 <notification> 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 <eventTime> element. It is the time the event was generated by the event source. This parameter is of type dateTime and compliant to . Implementations must support time zones. The event notification also contains notification-specific tagged content, if any. With the exception of <eventTime>, 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 <notification-contents-{encoding}>, E.g., <notification-contents-json>. That element contains the notification contents in the desired encoding The following is an example of an event notification from :

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; } }

<notification xmlns=" urn:ietf:params:xml:ns:netconf:notification:1.0"> <eventTime>2007-09-01T10:00:00Z</eventTime> <link-failure xmlns="http://acme.example.com/system"> <if-name>so-1/2/3.0</if-name> <if-admin-status>up</if-admin-status> <if-oper-status>down</if-oper-status> </link-failure> </notification> The equivalent using json encoding would be

<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"> <eventTime>2007-09-01T10:00:00Z</eventTime> <notification-contents-json> { "acme-system:link-failure": { "if-name": "so-1/2/3.0", "if-admin-status": "up", "if-oper-status": "down " } } </notification-contents-json> </notification>

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.

This notification is originally defined in . 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 <replayComplete> 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.

This notification is originally defined in . It is sent to indicate that a subscription, which includes a stop time, has finished passing events.

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.

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.

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.

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).

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).

<CODE BEGINS> file "ietf-event-notifications@2016-09-11.yang" module ietf-event-notifications { namespace "urn:ietf:params:xml:ns:yang:ietf-event-notifications"; 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: <http://tools.ietf.org/wg/netconf/> WG List: <mailto:netconf@ietf.org> WG Chair: Mahesh Jethanandani <mailto:mjethanandani@gmail.com> WG Chair: Mehmet Ersue <mailto:mehmet.ersue@nokia.com> Editor: Alexander Clemm <mailto:ludwig@clemm.org> Editor: Alberto Gonzalez Prieto <mailto:albertgo@cisco.com> Editor: Eric Voit <mailto:evoit@cisco.com> Editor: Einar Nilsen-Nygaard <mailto:einarnn@cisco.com> Editor: Ambika Prasad Tripathy <mailto:ambtripa@cisco.com> Editor: Sharon Chisholm <mailto:schishol@ciena.com> Editor: Hector Trevino <mailto:htrevino@cisco.com"; description "This module contains conceptual YANG specifications for NETCONF Event Notifications."; revision 2016-09-11 { description "Initial version. Model for NETCONF Notifications (bis)"; reference "draft-ietf-netconf-rfc5277bis-00"; } /* * FEATURES */ feature json { description "This feature indicates that JSON encoding of notifications is supported."; } feature configured-subscriptions { description "This feature indicates that management plane configuration of subscription is supported."; } /* * IDENTITIES */ /* Identities for subscription results */ identity subscription-result { description "Base identity for RPC responses to requests surrounding management (e.g. creation, modification, deletion) of subscriptions."; } identity ok { base subscription-result; description "OK - RPC was successful and was performed as requested."; } identity error { base subscription-result; description "RPC was not successful. Base identity for error return codes."; } identity error-no-such-subscription { base error; description "A subscription with the requested subscription ID does not exist."; } identity error-no-such-option { base error; description "A requested parameter setting is not supported."; } identity error-insufficient-resources { base error; description "The server has insufficient resources to support the subscription as requested."; } identity error-configured-subscription { base error; description "Cannot apply RPC to a configured subscription, i.e. to a subscription that was not established via RPC."; } identity error-other { base error; description "An unspecified error has occurred (catch all)."; } /* Identities for subscription stream status */ identity subscription-stream-status { description "Base identity for the status of subscriptions and datastreams."; } identity active { base subscription-stream-status; description "Status is active and healthy."; } identity inactive { base subscription-stream-status; description "Status is inactive, for example outside the interval between start time and stop time."; } identity suspended { base subscription-stream-status; description "The status is suspended, meaning that the push server is currently unable to provide the negotiated updates for the subscription."; } identity in-error { base subscription-stream-status; description "The status is in error or degraded, meaning that stream and/or subscription is currently unable to provide the negotiated notifications."; } /* Identities for subscription errors */ identity subscription-errors { description "Base identity for subscription error status. This identity is not to be confused with error return codes for RPCs"; } identity internal-error { base subscription-errors; description "Subscription failures caused by server internal error."; } identity no-resources { base subscription-errors; description "Lack of resources, e.g. CPU, memory, bandwidth"; } identity subscription-deleted { base subscription-errors; description "The subscription was terminated because the subscription was deleted."; } identity other { base subscription-errors; description "Fallback reason - any other reason"; } /* Identities for encodings */ identity encodings { description "Base identity to represent data encodings"; } identity encode-xml { base encodings; description "Encode data using XML"; } identity encode-json { base encodings; description "Encode data using JSON"; } /* Identities for transports */ identity transport { description "An identity that represents a transport protocol for event notifications"; } identity netconf { base transport; description "Netconf notifications as a transport."; } /* * TYPEDEFs */ typedef subscription-id { type uint32; description "A type for subscription identifiers."; } typedef filter-id { type uint32; description "A type to identify filters which can be associated with a subscription."; } typedef subscription-result { type identityref { base subscription-result; } description "The result of a subscription operation"; } typedef subscription-term-reason { type identityref { base subscription-errors; } description "Reason for a server to terminate a subscription."; } typedef subscription-susp-reason { type identityref { base subscription-errors; } description "Reason for a server to suspend a subscription."; } typedef encoding { type identityref { base encodings; } description "Specifies a data encoding, e.g. for a data subscription."; } typedef subscription-status { type identityref { base subscription-stream-status; } description "Specifies the status of a subscription or datastream."; } typedef transport-protocol { type identityref { base transport; } description "Specifies transport protocol used to send notifications to a receiver."; } typedef push-source { type enumeration { enum "interface-originated" { description "Notifications will be sent from a specific interface on a NETCONF server"; } enum "address-originated" { description "Notifications will be sent from a specific address on a NETCONF server"; } } description "Specifies from where notifications will be sourced when being sent by the NETCONF server."; } typedef filter-ref { type leafref { path "/notif-bis:filters/notif-bis:filter/notif-bis:filter-id"; } description "This type is used to reference a filter."; } /* * GROUPINGS */ grouping subscription-info { description "This grouping describes basic information concerning a subscription."; uses notif:subscription-info-5277 { augment "filter-type" { description "Post-5277 subscriptions allow references to existing filters"; case by-reference { description "Incorporate a filter that has been configured separately."; leaf filter-ref { type filter-ref; description "References filter which is associated with the subscription."; } } } } leaf encoding { type encoding; default "encode-xml"; description "The type of encoding for the subscribed data. Default is XML"; } } grouping push-source-info { description "Defines the sender source from which notifications for a configured subscription are sent."; choice push-source { description "Identifies the egress interface on the Publisher from which notifications will or are being sent."; case interface-originated { description "When the push source is out of an interface on the Publisher established via static configuration."; leaf source-interface { type if:interface-ref; description "References the interface for notifications."; } } case address-originated { description "When the push source is out of an IP address on the Publisher established via static configuration."; leaf source-vrf { type uint32 { range "16..1048574"; } description "Label of the vrf."; } leaf source-address { type inet:ip-address-no-zone; mandatory true; description "The source address for the notifications."; } } } } grouping receiver-info { description "Defines where and how to deliver notifications for a configured subscription. This includes specifying the receiver, as well as defining any network and transport aspects when sending of notifications occurs outside of Netconf."; container receivers { description "Set of receivers in a subscription."; list receiver { key "address"; min-elements 1; description "A single host or multipoint address intended as a target for the notifications for a subscription."; leaf address { type inet:host; mandatory true; description "Specifies the address for the traffic to reach a remote host. One of the following must be specified: an ipv4 address, an ipv6 address, or a host name."; } leaf port { type inet:port-number; mandatory true; description "This leaf specifies the port number to use for messages destined for a receiver."; } leaf protocol { type transport-protocol; default "netconf"; description "This leaf specifies the transport protocol used to deliver messages destined for the receiver."; } } } } grouping subscription-response { description "Defines the output to the rpc's establish-subscription and modify-subscription."; leaf subscription-result { type subscription-result; mandatory true; description "Indicates whether subscription is operational, or if a problem was encountered."; } choice result { description "Depending on the subscription result, different data is returned."; case success { description "This case is used when the subscription request was successful and a subscription was created/modified as a result"; leaf subscription-id { type subscription-id; mandatory true; description "Identifier used for this subscription."; } } case no-success { description "This case applies when a subscription request was not successful and no subscription was created (or modified) as a result. In this case, information MAY be returned that indicates suggested parameter settings that would have a high likelihood of succeeding in a subsequent establish-subscription or modify-subscription request."; uses subscription-info; } } } /* * RPCs */ rpc establish-subscription { description "This RPC allows a subscriber to create (and possibly negotiate) a subscription on its own behalf. If successful, the subscription remains in effect for the duration of the subscriber's association with the publisher, or until the subscription is terminated by virtue of a delete-subscription request. In case an error (as indicated by subscription-result) is returned, the subscription is not created. In that case, the RPC output MAY include suggested parameter settings that would have a high likelihood of succeeding in a subsequent create-subscription request."; input { uses subscription-info; } output { uses subscription-response; } } rpc modify-subscription { description "This RPC allows a subscriber to modify a subscription that was previously created using create-subscription. If successful, the subscription remains in effect for the duration of the subscriber's association with the publisher, or until the subscription is terminated by virtue of a delete-subscription request. In case an error is returned (as indicated by subscription-result), the subscription is not modified and the original subscription parameters remain in effect. In that case, the rpc error response MAY include suggested parameter settings that would have a high likelihood of succeeding in a subsequent modify-subscription request."; input { leaf subscription-id { type subscription-id; description "Identifier to use for this subscription."; } uses subscription-info; } output { uses subscription-response; } } rpc delete-subscription { description "This RPC allows a subscriber to delete a subscription that was previously created using create-subscription."; input { leaf subscription-id { type subscription-id; mandatory true; description "Identifier of the subscription that is to be deleted. Only subscriptions that were created using create-subscription can be deleted via this RPC."; } } output { leaf subscription-result { type subscription-result; mandatory true; description "Indicates whether subscription is operational, or if a problem was encountered."; } } } /* * NOTIFICATIONS */ notification replay-complete { netmod-notif:control-plane-notif; description "This notification is sent to indicate that all of the replay notifications have been sent. It must not be sent for any other reason."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } } notification notification-complete { netmod-notif:control-plane-notif; description "This notification is sent to indicate that a subscription, which includes a stop time, has finished passing events."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } } notification subscription-started { netmod-notif:control-plane-notif; description "This notification indicates that a subscription has started and notifications are beginning to be sent. This notification shall only be sent to receivers of a subscription; it does not constitute a general-purpose notification."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } uses subscription-info; } notification subscription-suspended { netmod-notif:control-plane-notif; description "This notification indicates that a suspension of the subscription by the server has occurred. No further notifications will be sent until subscription resumes. This notification shall only be sent to receivers of a subscription; it does not constitute a general-purpose notification."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } leaf reason { type subscription-susp-reason; description "Provides a reason for why the subscription was suspended."; } } notification subscription-resumed { netmod-notif:control-plane-notif; description "This notification indicates that a subscription that had previously been suspended has resumed. Notifications will once again be sent."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } } notification subscription-modified { netmod-notif:control-plane-notif; description "This notification indicates that a subscription has been modified. Notifications sent from this point on will conform to the modified terms of the subscription."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } uses subscription-info; } notification subscription-terminated { netmod-notif:control-plane-notif; description "This notification indicates that a subscription has been terminated."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } leaf reason { type subscription-term-reason; description "Provides a reason for why the subscription was terminated."; } } notification added-to-subscription { netmod-notif:control-plane-notif; description "This notification is sent to a receiver when it has been added to an existing subscription. Note that if the receiver is added when the subscription is created, it will receive a subscription-started notification and no added-to-subscription."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } uses subscription-info; } notification removed-from-subscription { netmod-notif:control-plane-notif; description "This notification is sent to a receiver when it has been removed from an existing subscription. Note that if the subscription is terminated, the receiver will receive a subscription-terminated notification and no removed-from-subscription."; leaf subscription-id { type subscription-id; mandatory true; description "This references the affected subscription."; } } /* * DATA NODES */ container streams { config false; description "This container contains a leaf list of built-in streams that are provided by the system."; leaf-list stream { type notif:stream; description "Identifies the built-in streams that are supported by the system. Built-in streams are associated with their own identities, each of which carries a special semantics. In case configurable custom streams are supported, as indicated by the custom-stream identity, the configuration of those custom streams is provided separately."; } } container filters { description "This container contains a list of configurable filters that can be applied to subscriptions. This facilitates the reuse of complex filters once defined."; list filter { key "filter-id"; description "A list of configurable filters that can be applied to subscriptions."; leaf filter-id { type filter-id; description "An identifier to differentiate between filters."; } uses notif:base-filter; } } container subscription-config { if-feature "configured-subscriptions"; description "Contains the list of subscriptions that are configured, as opposed to established via RPC or other means."; list subscription { key "subscription-id"; description "Content of a subscription."; leaf subscription-id { type subscription-id; description "Identifier to use for this subscription."; } uses subscription-info; uses receiver-info { if-feature "configured-subscriptions"; } uses push-source-info { if-feature "configured-subscriptions"; } } } container subscriptions { config false; description "Contains the list of currently active subscriptions, i.e. subscriptions that are currently in effect, used for subscription management and monitoring purposes. This includes subscriptions that have been setup via RPC primitives, e.g. create-subscription, delete-subscription, and modify-subscription, as well as subscriptions that have been established via configuration."; list subscription { key "subscription-id"; config false; description "Content of a subscription. Subscriptions can be created using a control channel or RPC, or be established through configuration."; leaf subscription-id { type subscription-id; description "Identifier of this subscription."; } leaf configured-subscription { if-feature "configured-subscriptions"; type empty; description "The presence of this leaf indicates that the subscription originated from configuration, not through a control channel or RPC."; } leaf subscription-status { type subscription-status; description "The status of the subscription."; } uses subscription-info; uses receiver-info { if-feature "configured-subscriptions"; } uses push-source-info { if-feature "configured-subscriptions"; } } } } <CODE ENDS>

Capabilities are advertised in messages sent by each peer during session establishment . 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:

<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> <capabilities> <capability> urn:ietf:params:xml:ns:netconf:base:1.0 </capability> <capability> urn:ietf:params:netconf:capability:startup:1.0 </capability> <capability> urn:ietf:params:netconf:capability:notification:1.0 </capability> <capability> urn:ietf:params:netconf:capability:notification:1.1 </capability> </capabilities> <session-id>4</session-id> </hello> Clients that only support recognize capability "urn:ietf:params:netconf:capability:notification:1.0" and ignore capability "urn:ietf:params:netconf:capability:notification:1.1". 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 , e.g., replayComplete; and that commonly used in yang models, e.g., subscription-started.

The security considerations from the base NETCONF document also apply to the notification capability. The <notification> 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 <get> 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. <create-subscriptiont> and <establish-subscriptiont> operations can be considered like deferred <get>, and the content that different users can access may vary. This different access is reflected in the <notificationt> 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 <create-subscription> 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 <kill-session> operation. If the client uses <establish-subscription>, 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 only terminate or refuse any transport sessions from the publisher. In addition, the NETCONF Authorization Control Model 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 , each of the elements in its data plane notifications must also go through access control.

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.

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. 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.

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")

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.