Custom Subscription to Event StreamsCisco Systemsevoit@cisco.comHuaweiludwig@clemm.orgVMWareagonzalezpri@vmware.comCisco Systemseinarnn@cisco.comCisco Systemsambtripa@cisco.com
Operations & Management
NETCONFDraftThis document defines capabilities and operations for the customized establishment of subscriptions upon a publisher's event streams. Also defined are delivery mechanisms for instances of the resulting notification messages. Effectively this allows a subscriber to request and receive a continuous, custom feed of publisher generated information.This document defines capabilities and operations for the customized establishment of subscriptions upon system generated event streams. Effectively this enables a "subscribe then publish" capability where the customized information needs of each target receiver are understood by the publisher before subscribed event records are marshalled and pushed. The receiver then gets a continuous, custom feed of publisher generated information.While the functionality defined in this document is transport-agnostic, protocols like NETCONF or RESTCONF can be used to configure or dynamically signal subscriptions, and there are bindings defined for subscribed event record delivery for NETCONF within , and for HTTP2 or HTTP1.1 within .There are various limitations, many of which have been exposed in which needed to be solved. Key capabilities supported by this document include:multiple subscriptions on a single transport sessionsupport for dynamic and statically configured subscriptionsmodification of an existing subscriptionoperational counters and instrumentationnegotiation of subscription parameters (through the use of hints returned as part of declined subscription requests)state change notifications (e.g., publisher driven suspension, parameter modification)independence from transport protocolThe 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 publisher created via an establish-subscription RPC.Event: An occurrence of something 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 record: A set of information detailing an event.NACM: NETCONF Access Control Model.Notification message: A set of transport encapsulated information intended for a receiver indicating that one or more event(s) have occurred. A notification message may bundle multiple event records. This includes the bundling multiple, independent RFC 7950 YANG notifications.Publisher: An entity responsible for streaming notification messages per the terms of a Subscription.Receiver: A target to which a publisher pushes subscribed event records. For dynamic subscriptions, the receiver and subscriber are the same entity.Stream (also referred to as "event stream"): A continuous ordered set of events aggregated under some context.Stream filter: Evaluation criteria which may be applied against event records within a stream. Event records pass the filter when specified criteria are met.Subscribed event records: Event records which have met the terms of the subscription. This include terms (such as security checks) enforced by the publisher.Subscriber: An entity able to request and negotiate a contract for the generation and push of event records from a publisher.Subscription: A contract with a publisher, stipulating which information one or more receivers wish to have pushed from the publisher without the need for further solicitation.This document describes a transport agnostic mechanism for subscribing to and receiving content from a stream instantiated within a publisher. This mechanism is through the use of a subscription.Two types of subscriptions are supported:Dynamic subscriptions, where a subscriber initiates a subscription negotiation with a publisher via RPC. If the publisher wants to serve this request, it accepts it, and then starts pushing notification messages. If the publisher does not wish to serve it as requested, then an error response is returned. This response MAY include hints at subscription parameters which would have been accepted.Configured subscriptions, which allow the management of subscriptions via a configuration interface so that a publisher can send notification messages to configured receiver(s). Support for this capability is optional.Additional characteristics differentiating configured from dynamic subscriptions include:The lifetime of a dynamic subscription is bounded by the transport session used to establish it. For connection-oriented stateful transport like NETCONF, the loss of the transport session will result in the immediate termination of any associated dynamic subscriptions. For connectionless or stateless transports like HTTP, a lack of receipt acknowledgement of a sequential set of notification messages and/or keep-alives can be used to trigger a termination of a dynamic subscription. Contrast this to the lifetime of a configured subscription. This lifetime is driven by relevant configuration being present within the publisher's running configuration. Being tied to configuration operations implies configured subscriptions can be configured to persist across reboots, and implies a configured subscription can persist even when its publisher is fully disconnected from any network.Configured subscriptions can be modified by any configuration client with write permission on the configuration of the subscription. Dynamic subscriptions can only be modified via an RPC request made by the original subscriber.Note that there is no mixing-and-matching of dynamic and configured operations on a single subscriptions. Specifically, a configured subscription cannot be modified or deleted using RPCs defined in this document. Similarly, a subscription established via RPC cannot be modified through configuration operations. Also note that transport specific transport drafts based on this specification MUST detail the life cycles of both dynamic and configured subscriptions.The publisher MAY decide to terminate a dynamic subscription at any time. Similarly, it MAY decide to temporarily suspend the sending of notification messages for any dynamic subscription, or for one or more receivers of a configured subscription. Such termination or suspension is driven by internal considerations of the publisher.This document is intended to provide a superset of the subscription capabilities initially defined within . Especially when extending an existing implementation, it is important to understand what has been reused and what has been replaced. Key relationships between these two documents include:
the data model in this document replaces the data model in .the RPC operations in this draft replaces the symmetrical operations of , section 4.the one way operation of is still used. However this operation will no longer be required with the availability of . the definition and contents of the NETCONF stream are identical between this document and .a publisher MAY implement both the data model and RPCs defined in and this new document concurrently, in order to support old clients. However the use of both alternatives on a single transport session is prohibited.An event stream is a named entity on a publisher which exposes a continuously updating set of event records. Each event stream is available for subscription. It is out of the scope of this document to identify a) how streams are defined, b) how event records are defined/generated, and c) how event records are assigned to streams.There is only one reserved event stream within this document: NETCONF. The NETCONF event stream contains all NETCONF XML event record information supported by the publisher, except for where it has been explicitly indicated that this the event record MUST be excluded from the NETCONF stream. The NETCONF stream will include individual YANG notifications as per section 7.16. Each of these YANG notifications will be treated a distinct event record. Beyond the NETCONF stream, implementations are free to add additional event streams.As event records are created by a system, they may be assigned to one or more streams. The event record is distributed to subscription's receiver(s) where: (1) a subscription includes the identified stream, and (2) subscription filtering does not exclude the event record from that receiver.If access control permissions are in use to secure publisher content, then for event records to be sent to a receiver, that receiver MUST be allowed access to all the event records on the stream. If subscriber permissions change during the lifecycle of a subscription, then the subscription MUST be continued or terminated accordingly.This document defines an extensible filtering mechanism. Two optional stream filtering syntaxes supported are and subtree . A filter always removes a complete event record; a subset of information is never stripped from an event record.If no stream filter is provided within a subscription, all event records on a stream are to be sent.This document provides an optional feature describing QoS parameters. These parameters indicate the treatment of a subscription relative to other traffic between publisher and receiver. Included are:
A "dscp" QoS marking to differentiate transport QoS behavior. Where provided, this marking MUST be stamped on notification messages.A "weighting" so that bandwidth proportional to this weighting can be allocated to this subscription relative to other subscriptions destined for that receiver.a "dependency" upon another subscription. Notification messages MUST NOT be sent prior to other notification messages containing update record(s) for the referenced subscription.A subscription's weighting MUST work identically to stream dependency weighting as described within RFC 7540, section 5.3.2.A subscription's dependency MUST work identically to stream dependency as described within , sections 5.3.1, 5.3.3, and 5.3.4. If a dependency is attempted via an RPC, but the referenced subscription does not exist, the dependency will be silently removed.Dynamic subscriptions are managed via RPC, and are made against targets located within the publisher. These RPCs have been designed extensibly so that they may be augmented for subscription targets beyond event streams.Below is the publisher's state machine for a dynamic subscription. It is important to note that such a subscription doesn't exist at the publisher until it an "establish-subscription" RPC is accepted. The mere request by a subscriber to establish a subscription is insufficient for that asserted subscription to be externally visible.Of interest in this state machine are the following:
Successful establish or modify RPCs put the subscription into an active state.Failed modify RPCs will leave the subscription in its previous state, with no visible change to any streaming updates.A delete or kill RPC will end the subscription.Suspend and resume state changes are driven by internal process and prioritization. There are no direct controls over suspend and resume other than modifying a subscriptionThe "establish-subscription" operation allows a subscriber to request the creation of a subscription via RPC. It MUST be possible to support multiple establish subscription RPC requests made within the same transport session.The input parameters of the operation are:
A stream name which identifies the targeted stream of events against which the subscription is applied.A stream filter which may reduce the set of event records pushed.An optional encoding for the event records pushed. Note: If no encoding is included, the encoding of the RPC MUST be used.An optional stop time for the subscription. If no stop-time is present, notification messages will continue to be sent until the subscription is terminated.An optional start time which indicates that this subscription is requesting a replay of previously generated information from the event stream. For more on replay, see If the publisher can satisfy the "establish-subscription" request, it provides an identifier for the subscription, and immediately starts streaming notification messages. If the subscriber has no authorization to establish the subscription, transport protocol specific replies are used to indicate an authorization error. If an RPC request is properly framed, but publisher cannot satisfy the "establish-subscription" request, the publisher MUST send a negative "subscription-result" element describing the reason for the failure. Optionally, the "subscription-result" MAY be accompanied by one or more hints on alternative inputs which would have resulted in an accepted subscription."establish-subscription" requests MUST fail if a filter with invalid or unsupportable syntax is provided, or if a non-existent stream is referenced. Replay provides the ability to establish a subscription which is also capable of passing recently generated event records. In other words, as the subscription initializes itself, it sends any previously generated content from within target event stream which meets the filter and timeframe criteria. These historical event records would then be followed by event records generated after the subscription has been established. All event records will be delivered in the order generated.Replay is an optional feature which is dependent on an event stream supporting some form of logging. Replay puts no restrictions on the size or form of the log, or where it resides within the device.The inclusion of a replay-start-time within an "establish-subscription" RPC indicates a replay request. If the "replay-start-time" contains a value that is earlier than content stored within the publisher's replay buffer, then the subscription MUST be rejected, and the leaf "replay-start-time-hint" MUST be set in the reply.If a "stop-time" parameter is included, it MAY also be earlier than the current time and MUST be later than the "replay-start-time". The publisher MUST NOT accept a "replay-start-time" for a future time.If the "replay-start-time" is later than any information stored in the replay buffer, then the publisher MUST send a "replay-completed" notification immediately after the "subscription-started" notification.If a stream supports replay, the "replay-support" leaf is present in the "/streams/stream" list entry for the stream. An event stream that does support replay is not expected to have an unlimited supply of saved notifications available to accommodate any given replay request. To assess the availability of replay, subscribers can perform a get on "replay-log-creation-time" and "replay-log-aged-time". See for the tree describing these elements. The actual size of the replay log at any given time is a publisher specific matter. Control parameters for the replay log are outside the scope of this document.The "modify-subscription" operation permits changing the terms of an existing dynamic subscription previously established on that transport session via "establish-subscription". Dynamic subscriptions can be modified one or multiple times. If the publisher accepts the requested modifications, it replies with "ok" in the "subscription-result", then immediately starts sending event records based on the new terms. If the publisher rejects the request, the subscription remains as prior to the request. That is, the request has no impact whatsoever. The contents of a such a rejected modification MAY include one or more hints on alternative inputs which would have resulted in a successfully modified subscription.If the publisher accepts the requested modifications on a currently suspended subscription, the subscription will immediately be resumed (i.e., the modified subscription is returned to an active status.) The publisher MAY immediately suspend this newly modified subscription through the "subscription-suspended" notification before any event records are sent.Dynamic subscriptions established via RPC can only be modified via RPC using the same transport session used to establish that subscription. Subscriptions created by configuration operations cannot be modified via this RPC.The "delete-subscription" operation permits canceling an existing subscription previously established on that transport session. If the publisher accepts the request, and the publisher has indicated this success via an "ok" in the "subscription-result", the publisher MUST NOT send any more notification messages for this subscription. If the publisher rejects the request, the request has no impact whatsoever on any subscription.Dynamic subscriptions can only be deleted via this RPC using the same transport session previously used for subscription establishment. Configured subscriptions cannot be deleted using RPCs.The "kill-subscription" operation permits an operator to end a dynamic subscription which is not associated with the transport session used for the RPC. This operation MUST be secured so that only connections with sufficiently privileged access rights are able to invoke this RPC. A publisher MUST terminate any dynamic subscription identified by RPC request. An operator may find subscription identifiers which may be used with "kill-subscription" by searching for the IP address of a receiver within "subscriptions\subscription\receivers\receiver\address".Configured subscriptions cannot be killed using this RPC. Instead, configured subscriptions are deleted as part of regular configuration operations. Publishers MUST reject any RPC attempt to kill a configured subscription.The tree structure of "kill-subscription" is almost identical to "delete-subscription", with only the name of the RPC changing.A configured subscription is a subscription installed via a configuration interface. Configured subscriptions may be modified by any configuration client with the proper permissions. Subscriptions can be modified or terminated via the configuration interface at any point of their lifetime.Configured subscriptions have several characteristics distinguishing them from dynamic subscriptions:
persistence across reboots,persistence even when transport is unavailable, andan ability to send notification messages to more than one receiver (note that the publisher does not provide information to a receiver about other receivers.)Supporting configured subscriptions is optional and advertised using the "configured" feature. In addition to subscription parameters available to dynamic subscriptions as described in , the following additional parameters are also available to configured subscriptions:
One or more receiver IP addresses (and corresponding ports) intended as the destination for notification messages.Optional parameters to identify an egress interface, a host IP address, a VRF (as defined by the network instance name within ), or an IP address plus VRF out of which notification messages are to be pushed from the publisher. Where any of this info is not explicitly included, or where just the VRF is provided, notification messages MUST egress the publisher's default interface towards that receiver.Below is the state machine for a configured subscription. The creation or modification of a configured subscription initiates a publisher evaluation to determine if the subscription is valid or invalid. The publisher uses its own criteria in making this determination. If valid, the subscription becomes operational. A valid subscription may become invalid on one of two ways. First, it may be modified in a way which fails a re-evaluation. Second, the publisher itself might itself determine that the subscription in no longer supportable. In either case, a "subscription-terminated" notification is sent to any active or suspended receivers. A valid subscription may also transtion to a concluded status if a configured stop time has been reached. In this case, a "subscription-concluded" is sent to any active or suspended receivers.During any times a subscription is considered valid, a publisher will attempt to connect with all configured receivers and deliver notification messages. Below is the state machine for each receiver of a configured subscription. This receiver state machine itself is fully contained within the state machine of the configured subscription, and is only relevant when the configured subscription itself is determined to be valid.When a subscription first becomes valid, the operational status of each receiver is initialized to connecting. Individual are receivers are moved to an active status when a "subscription-started" state change notification is successfully passed to that receiver. Configured receivers remain active if transport connectivity is not lost, and event records are not being dropped due to a publisher buffer overflow. A configured subscription's receiver MUST be moved to connecting if transport connectivity is lost, or if the receiver is reset via configuration operations.A configured subscription's receiver MUST be moved to a suspended state if there is transport connectivity between the publisher and receiver, but notification messages are not being generated for that receiver. A configured subscription receiver MUST be returned to an active state from the suspended state when notification messages are again being generated and a receiver has successfully been sent a "subscription-resumed" or a "subscription-modified".Modification of a configured subscription is possible at any time. A "subscription-modified" state change notification will be sent to all active receivers, immediately followed by notification messages conforming to the new parameters. Suspended receivers will also be informed of the modification. However this notification will await the end of the suspension for that receiver.The mechanisms described above is mirrored in the RPCs and YANG notifications within the document. It should be noted that these RPCs and YANG notifications have been designed to be extensible and allow subscriptions into targets other than event streams. provides an example of such an extension.Configured subscriptions are established using configuration operations against the top-level subtree "subscription-config". There are two key differences between the new RPCs defined in this document and configuration operations for subscription creation. Firstly, configuration operations install a subscription without question, while the RPCs are designed to the support negotiation and rejection of requests. Secondly, while the RPCs mandate that the subscriber establishing the subscription is the only receiver of the notification messages, configuration operations permit specifying receivers independent of any tracked subscriber. Because there is no explicit association with an existing transport session, configuration operations require additional parameters beyond those of dynamic subscriptions to indicate receivers, and possibly whether the notification messages need to come from a specific egress interface on the publisher.After a subscription is successfully created, the publisher immediately sends a "subscription-started" state change notification to each receiver. It is quite possible that upon configuration, reboot, or even steady-state operations, a transport session may not be currently available to the receiver. In this case, when there is something to transport for an active subscription, transport specific call-home operations will be used to establish the connection. When transport connectivity is available, notification messages may then be pushed.With active configured subscriptions, it is allowable to buffer event records even after a "subscription-started" has been sent. However if events are lost (rather than just delayed) due to replay buffer overflow, a new "subscription-started" must be sent. This new "subscription-started" indicates an event record discontinuity.To see an example at subscription creation using configuration operations over NETCONF, see Appendix A of .Note that is possible to configure replay on a configured subscription. This capability is to allow a configured subscription to exist on a system so that event records generated during boot can be buffered and pushed as soon as the transport session is established.Configured subscriptions can be modified using configuration operations against the top-level subtree "subscription-config".If the modification involves adding receivers, added receivers are placed in the "connecting" state. If a receiver is removed, the state change notification "subscription-terminated" is sent to that receiver if that receiver is "active" or "suspended" .If the modification involved changing the policies for the subscription, the publisher sends to currently active receivers a "subscription-modified" notification. For any suspended receivers, a "subscription-modified" notification will be delayed until the receiver is resumed. (Note: in this case, the "subscription-modified" notification informs the receiver that the subscription has been resumed, so no additional "subscription-resumed" need be sent.)Subscriptions can be deleted using configuration operations against the top-level subtree "subscription-config".Immediately after a subscription is successfully deleted, the publisher sends to all receivers of that subscription a state change notification stating the subscription has ended (i.e., "subscription-terminated").It is possible that a configured subscription to a receiver needs to be reset. This re-initialization may be useful in cases where a publisher has timed out trying to reach a receiver. When such a reset occurs, a transport session will be initiated if necessary, and a new "subscription-started" notification will be sent.Whether dynamic or configured, once a subscription has been set up, the publisher streams event records via notification messages per the terms of the subscription. For dynamic subscriptions set up via RPC operations, notification messages are sent over the session used to establish the subscription. For configured subscriptions, notification messages are sent over the connections specified by the transport, plus receiver IP address and port configured.A notification message is sent to a receiver when an event record is able to traverse the specified filter criteria. This notification message MUST be encoded as one-way notification element of , Section 4. The following example within section 7.16.3 is an example of a compliant message:This [RFC5277] section 4 one-way operation has the drawback of not including useful header information such as a subscription identifier. When using this mechanism, it is left up to implementations or augmentations to this document to determine which event records belong to which subscription.These drawbacks, along with other useful common headers and the ability to bundle multiple event records together is being explored within . When the notification-messages is supported, this document will be updated to indicate support.In addition to subscribed event records, a publisher will send subscription state notifications to indicate to receivers that an event related to the subscription management has occurred.Subscription state notifications are unlike other notifications which might be found in the event stream. They cannot be filtered out, and they are delivered only to directly impacted receiver(s) of a subscription. The identification of subscription state notifications is easy to separate from other notification messages through the use of the YANG extension "subscription-state-notif". This extension tags a notification as subscription state notification. The complete set of subscription state notifications is described in the following subsections.This notification indicates that a configured subscription has started, and event records may be sent. Included in this state change notification are all the parameters of the subscription, except for the receiver(s) addressing information and origin information indicating where notification messages will egress the publisher. Note that if a referenced filter from the "filters" container has been used within the subscription, the notification will include the contents of that referenced under the "within-subscription" subtree.Note that for dynamic subscriptions, no "subscription-started" notifications are ever sent.This notification indicates that a subscription has been modified by configuration operations. The same parameters of "subscription-started" are provided via this notification. As a result, the tree structure of "subscription-modified" is almost identical to "subscription-started", with only the name of the notification changing.A publisher most often sends this notification directly after the modification of any configuration parameters impacting a configured subscription. But it may also be sent at two other times.
First, where a configured subscription has been modified during the suspension of a receiver, the notification will be delayed until the receiver's suspension is lifted. In this situation, the notification indicates that the subscription has been both modified and resumed.Second, for dynamic subscriptions, there is one and only one time this notification may be sent. A "subscription-modified" state change notifications MUST be sent if the contents of a filter identified by a "stream-filter-ref" has changed.This notification indicates that a subscription has been terminated on the publisher. The state change notification includes the reason for the termination.The publisher MAY decide to terminate a subscription rather than continuing to serve it. Such a decision may be made when a publisher runs out of resources, an internal error occurs, or some other reason. Publisher-driven terminations are always notified to all receivers.Subscribers themselves can terminate existing subscriptions established via a "delete-subscription" RPC. In such cases, no "subscription-terminated" state change notifications are sent. However if a "kill-subscription" RPC is sent, or some other event other than reaching the subscription's stop time results in the end of a subscription, then this state change notification MUST be sent. This notification indicates that a publisher has suspended the sending of event records to a receiver, and also indicates the possible loss of events. The state change notification includes the reason for the suspension. No further notification will be sent until the subscription resumes. The tree structure of "subscription-suspended" is almost identical to "subscription-terminated", with only the name of the notification changing.This indicates that a previously suspended subscription has been resumed under the unmodified terms previously in place. Subscribed event records generated after the generation of this state change notification will be sent.This notification indicates that a subscription, which includes a "stop-time", has successfully finished passing event records upon the reaching of that time.The tree structure of "subscription-completed" is almost identical to "subscription-resumed", with only the name of the notification changing.This notification indicates that all of the event records prior to the current time have been sent. This includes new event records generated since the start of the subscription. This notification MUST NOT be sent for any other reason. If subscription contains no "stop-time", or has a "stop-time" which has not been reached, then after the "replay-completed" notification has been sent, additional event records will be sent in sequence as they arise naturally on the publisher.The tree structure of "replay-completed" is almost identical to "subscription-resumed", with only the name of the notification changing.Container "subscriptions" in the YANG module contains the state of all known subscriptions. This includes subscriptions that were established (and have not yet been deleted) using RPCs, as well as subscriptions that have been configured as part of configuration. Using the "get" operation with NETCONF, or subscribing to this information via allows the status of subscriptions to be monitored.Each subscription is represented as a list element. The associated information includes an identifier for the subscription, receiver counter information, the status of the subscription, as well as the various subscription parameters that are in effect. The subscription status indicates the subscription's state with each receiver (e.g., is currently active or suspended). Leaf "configured-subscription" indicates whether the subscription came into being via configuration or via RPC.Subscriptions that were established by RPC are removed from the list once they expire (reaching stop-time) or when they are terminated. Subscriptions that were established by configuration need to be deleted from the configuration by a configuration editing operation even if the stop time has been passed.Publishers supporting this document MUST indicate support the YANG model "ietf-subscribed-notifications" within the YANG library of the publisher. In addition support for optional features: "encode-xml", "encode-json", "configured" "supports-vrf", and "replay" MUST also be indicated if supported.If a publisher supports this specification but not subscriptions via , the publisher MUST NOT advertise "urn:ietf:params:netconf:capability:notification:1.0". Even without this advertisement however, the publisher MUST support the one-way notification element of Section 4.This section contains tree diagrams for top level YANG Data Node containers defined in . If you would rather see tree diagrams for Notifications, see . Or for the tree diagrams for the RPCs, see .A publisher maintains a list of available event streams as operational data. This list contains both standardized and vendor-specific event streams. The list of event streams that are supported by the publisher and against which subscription is allowed may be acquired from the "streams" container within the YANG module.The "filters" container maintains a list of all subscription filters which persist outside the life-cycle of a single subscription. This enables pre-defined and validated filters which may be referenced and used by more than one subscription.The "subscriptions" container maintains a list of all subscriptions on a publisher, both configured and dynamic. It can be used to retrieve information about the subscriptions which a publisher is serving."Subscription-config" container contains the configuration of configured subscriptions.For a deployment including both configured and dynamic subscriptions, split subscription identifiers into static and dynamic halves. That way it is unlikely there will be collisions if the configured subscriptions attempt to set a subscription-id which might have already been dynamically allocated. The lower half the "identifier" object in the subscriptions container SHOULD be used when the "identifier" is selected and assigned by an external entity (such as with a configured subscription). And the upper half SHOULD be used for subscription identifiers dynamically chosen and assigned by the publisherNeither state change notification nor subscribed event records within notification messages may be sent before the transport layer, including any required capabilities exchange, has been established.An implementation may choose to transition between active and suspended subscription states more frequently than required by this specification. However if a subscription is unable to marshal all intended updates into a transmittable message in multiple successive intervals, the subscription SHOULD be suspended with the reason "unsupportable-volume".For configured subscriptions, operations are against the set of receivers using the subscription identifier as a handle for that set. But for streaming up dates, state change notifications are local to a receiver. In this specification it is the case that receivers get no information from the publisher about the existence of other receivers. But if an operator wants to let the receivers correlate results, it is useful to use the subscription identifier handle across the receivers to allow that correlation.
This document registers the following namespace URI in the "IETF XML
Registry" :
URI: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers the following YANG module in the "YANG
Module Names" registry :
Name: ietf-subscribed-notifications
Namespace: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications
Prefix: sn
Reference: draft-ietf-netconf-ietf-subscribed-notifications-08.txt
(RFC form)
For dynamic subscriptions the publisher MUST authenticate and authorize all RPC requests.Subscriptions could overload a publisher's CPU. For this reason, the publisher MUST have the ability to decline a dynamic subscription request, and provide the appropriate RPC error response to a subscriber should the proposed subscription overly deplete the publisher's resources.A publisher needs to be able to suspend an existing dynamic or configured subscription based on capacity constraints. When this occurs, the subscription status MUST be updated accordingly and the receivers notified with subscription state notifications.If a malicious or buggy subscriber sends an unexpectedly large number of RPCs, the result might be an excessive use of system resources. In such a situation, subscription interactions MAY be terminated by terminating the transport session.For both configured and dynamic subscriptions the publisher MUST authenticate and authorize a receiver via some transport level mechanism before sending any updates.A secure transport is highly recommended and the publisher MUST ensure that the receiver has sufficient authorization to perform the function they are requesting against the specific subset of content involved.A publisher MUST NOT include any content in a notification message for which the receiver has not been authorized.With configured subscriptions, one or more publishers could be used to overwhelm a receiver. No notification messages SHOULD be sent to any receiver which doesn't even support subscriptions. Receivers that do not want notification messages need only terminate or refuse any transport sessions from the publisher.The NETCONF Authorization Control Model SHOULD be used to control and restrict authorization of subscription configuration. This control models permits specifying per-receiver permissions to receive event records from specific streams.Where NACM is available, the NACM "very-secure" tag MUST be placed on the "kill-subscription" RPC so that only administrators have access to use this.One subscription id can be used for two or more receivers of the same configured subscription. But due to the possibility of different access control permissions per receiver, it SHOULD NOT be assumed that each receiver is getting identical updates.For their valuable comments, discussions, and feedback, we wish to acknowledge Andy Bierman, Tim Jenkins, Martin Bjorklund, Kent Watsen, Balazs Lengyel, Robert Wilton, Sharon Chisholm, Hector Trevino, Susan Hares, Michael Scharf, and Guangying Zheng.
XML Path Language (XPath) Version 1.0Network Configuration Protocol (NETCONF) Access Control ModelYANG Network InstancesYANG Datastore SubscriptionNETCONF support for event notificationsRestconf and HTTP transport for event notificationsYANG Notification Headers and Bundles(To be removed by RFC editor prior to publication)v07 - v08
Split YANG trees to separate document subsections.Clarified configured state machine based on Balazs comments, and moved it into the configured subscription subsections.Normative reference to Network Instance model for VRFOne transport protocol for all receivers of configured subscriptions.QoS section moved in from yang-pushv06 - v07
Clarification on state machine for configured subscriptions.v05 - v06
Made changes proposed by Martin, Kent, and others on the list. Most significant of these are Stream returned to string (with the SYSLOG identity removed), intro section on 5277 relationship, an identity set moved to an enumeration, clean up of definitions/terminology, state machine proposed for configured subscriptions with a clean-up of susbcription state options.JSON and XML become features. Also Xpath and subtree filtering become featuresTerminology updates with event records, and refinement of filters to just stream filters.Encoding refined in establish-subscription so it takes the RPC's encoding as the default.Namespaces in examples fixed.v04 - v05
Returned to the explicit filter subtyping of v00stream object changed to 'name' from 'stream'Cleaned up examplesClarified that JSON support needs notification-messages draft.v03 - v04Moved back to the use of RFC5277 one-way notifications and encodings.v03 - v04Replay updatedv02 - v03RPCs and Notification support is identified by the Notification 2.0 capability.Updates to filtering identities and textNew error type for unsupportable volume of updatesText tweaks.v01 - v02Subscription status moved under receiver.v00 - v01Security considerations updatedIntro rewrite, as well as scattered text changesAdded Appendix A, to help match this to related drafts in progressUpdated filtering definitions, and filter types in yang file, and moved to identities for filter typesAdded Syslog as a streamHTTP2 moved in from YANG-Push as a transport optionReplay made an optional feature for events. Won't apply to datastoresEnabled notification timestamp to have different formats.Two error codes added.v01 5277bis - v00 subscribed notificationsKill subscription RPC added.Renamed from 5277bis to Subscribed Notifications.Changed the notification capabilities version from 1.1 to 2.0.Extracted create-subscription and other elements of RFC5277.Error conditions added, and made specific in return codes.Simplified yang model structure for removal of 'basic' grouping.Added a grouping for items which cannot be statically configured.Operational counters per receiver.Subscription-id and filter-id renamed to identifierSection for replay added. Replay now cannot be configured.Control plane notification renamed to subscription state notificationSource address: Source-vrf changed to string, default address option addedIn yang model: 'info' changed to 'policy'Scattered text clarificationsv00 - v01 of 5277bisYANG Model changes. New groupings for subscription info to allow restriction of what is changeable via RPC. Removed notifications for adding and removing receivers of configured subscriptions.Expanded/renamed definitions from event server to publisher, and client to subscriber as applicable. Updated the definitions to include and expand on RFC 5277.Removal of redundancy with other draftsMany other clean-ups of wording and terminology