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 RPC subscription state signaling messages.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 include event records.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 a 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 associated dynamic subscriptions. For connectionless or stateless transports like HTTP, it is the lack of receipt acknowledgement of a sequential set of notification messages and/or keep-alives which will terminate dynamic subscriptions. The lifetime of a configured subscription is driven by relevant configuration being present on the running configuration. This implies configured subscriptions persist across reboots, and persist even when transport is unavailable.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 upon the original subscribing transport session.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 established via RPC cannot be modified through configuration operations (if needed, an operator may use a kill RPC however).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 either configured or dynamic subscriptions. Such termination or suspension MAY be driven by the publisher running out of resources to serve the subscription, or by internal errors on 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 realtionships between these two documents include:
the data model in this document replaces the data model in .the RPC operations in this draft replaces the symetrical 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 events. 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 events are defined/generated, and c) how events 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. Beyond NETCONF, implementations are free to add additional event streams.As events are raised by a system, they may be assigned to one or more streams. The event record is distributed to receivers 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 notification messages 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 . The subsets of these filtering syntaxes supported are left to each implementation. A subset of information is never stripped from within the event record.If no stream filter is provided, all event records on a stream are to be sent.Below is the state machine of a subscription for the publisher for a dynamic subscription. It is important to note that such a subscription doesn't exist at the publisher 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.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 external controls over suspend and resume.As shown below, a very similar state machine exists for configured subscriptions. Creation, modification, and deletion is via configuration operations rather than via RPC. When a subscription is first created, the operational status of each receiver is initially set to connecting. Individual are receivers are moved to an active status when a subscription-started state change notification is successfully delivered. Configured subscriptions remain active if transport connectivity is not lost and event records are not being dropped due to buffer overflow. A configured subscription MUST be moved connecting if transport connectivity is lost. A configured subscription MUST be moved to a suspended status if notification messages are being dropped despite the presence of transport connectivity. A configured subscription MUST be returned to an active status from the suspended status as soon as transport connectivity is re-established, and a receiver acknowledges receipt of a "subscription-resumed". Otherwise, it MUST be moved to connecting.The interaction model described within this section is mirrored in the RPCs and Notifications later in the document. It should be noted that these RPCs and Notifications have been designed to be extensible and allow subscriptions into targets other than event streams. provides an example of such an extension.The top-level decompositions of data model are as follows:"Streams" contains a list of event streams that are supported by the publisher and against which subscription is allowed."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 a superset of the parameters of a dynamic subscription and use the same groupings. In addition, the configured subscriptions MUST also specify intended receivers and MAY specify the push source from which to send the stream of notification messages."Subscriptions" contains 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. The data model also contains a number of YANG Notifications that allow a publisher to signal 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, and are made against targets located within the publisher. These RPCs have been designed extensibly so that they may be augmented for targets beyond event streams.The "establish-subscription" operation allows a subscriber to request the creation of a subscription via RPC. Multiple establish subscription RPC requests can be made within the same transport session.The input parameters of the operation are:
A stream name which identifies the continuous feed of events against which the subscription is applied.A filter which may reduce the set of event records pushed.The desired encoding for the notification message.An optional stop time for the subscription.An optional start time which indicates that this subscription is requesting a replay of previously generated information from the event stream.If the publisher cannot satisfy the "establish-subscription" request, it sends a negative "subscription-result" element. If the subscriber has no authorization to establish the subscription, the "subscription-result" indicates an authorization error. Optionally, the "subscription-result" MAY include one or more hints on alternative input parameters and value which would have resulted in an accepted subscription.Subscription requests MUST fail if a filter with invalid syntax is provided or if a non-existent stream is referenced. Replay provides the ability to establish an subscription which is also capable of passing along recently generated event records. In other words, as the subscription initializes itself, it sends any previously generated content from within target event stream which meet 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 only viable for dynamic subscriptions. Replay is an optional feature. Replay is dependent on an event stream supporting some form of logging, although it 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.An end time MAY be specified using the optional stop-time parameter, which only in the case of replay MAY also be earlier than the current time. If no stop-time is present, notification messages will continue to be sent until the subscription is terminated. 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.Not all streams will support replay. Those that do MUST include they do via the "replay-support" object. In addition, a event stream that does support replay is not expected to have an unlimited supply of saved notifications available to accommodate any given replay request. Subscribers MAY do a get on "replay-log-creation-time" and "replay-log-aged-time" to assess the availability of replay. The actual size of the replay log at any given time is a publisher specific matter. Control parameters for this aspect of the feature 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. Subscriptions created by configuration operations cannot be modified via this RPC. Dynamic subscriptions can be modified one or multiple times. If the publisher accepts the requested modifications, it replies that this change has been made, 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 input parameters and value which would have resulted in a successfully modified subscription.Dynamic subscriptions established via RPC can only be modified via RPC using the same transport session used to establish that subscription.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 successful reply has been sent, the publisher MUST NOT send any more notification messages for this subscription. If the publisher rejects the request, all subscriptions remain as prior to the request. That is, the request has no impact whatsoever.Subscriptions established via RPC can only be deleted via RPC using the same transport session 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 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 the yang tree.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.A configured subscription is a subscription installed via a configuration interface. Such a subscription MAY push notification messages to more than one receiver. The publisher does not provide information about receivers are provided no information about other receivers. Supporting configured subscriptions is optional and advertised using the "configured" feature.Configured subscriptions persist across reboots, and persist even when transport is unavailable.Configured subscriptions can be modified by any configuration client with write permissions for the configuration of the subscription. Subscriptions can be modified or terminated via the configuration interface at any point of their lifetime.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 notification messages for each subscription. In addition, the transport for each destination MAY be defined.Optional parameters to identify an egress interface, a host IP address, a VRF, or an IP address plus VRF out of which notification messages should 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. Configured subscriptions are established using configuration operations against the top-level subtree subscription-config. There are two key differences between RPCs and configuration operations for subscription creation. Firstly, configuration operations install a subscription without question, while RPCs are designed to the support negotiation and rejection of requests. Secondly, while 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, as successful receipt of the subscription start change notification by a particular receiver indicated, notification messages may then be pushed.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 is to allows 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.Immediately after a subscription is successfully modified, the publisher sends to the existing receivers a state change 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 state change notifications, indicating they have been added (i.e, subscription-started to a specific receiver) or removed (i.e., subscription-terminated to a specific receiver.)Subscriptions can be deleted using configuration operations against the top-level subtree subscription-config. For example, in RESTCONF:Immediately after a subscription is successfully deleted, the publisher sends to all receivers of that subscription a state change notification stating the subscription has been terminated (i.e., subscription-terminated).Configured 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 the existing receivers a state change notification stating the subscription has been terminated (i.e., subscription-terminated).Once a subscription has been set up, the publisher streams subscribed 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 specified connections.A notification message is sent to a receiver when something of interest occurs which is able to traverse all specified filtering and access control 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 definition of subscription state notifications is distinct from other notification messages by making use of a YANG extension tagging them as subscription state notification. Subscription state notifications include indications that a replay of event records has been completed, that a subscription is done 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 indicates that a configured subscription has started and data updates are beginning to be sent. This state change notification includes 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 for RPC-based subscriptions, no "subscription-started" notifications are sent.This indicates that a configured subscription has been modified successfully. This state change notification includes 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 for RPC-based subscriptions, no "subscription-modified" state change notifications are sent.This indicates that a subscription has been terminated by the publisher. The state change notification includes the reason for the termination. The publisher MAY decide to terminate a subscription when it is running out of resources for serving it, an internal error occurs, etc. Publisher-driven terminations are notified to all receivers. Northbound systems MAY also terminate configured subscriptions using configuration operations.Subscribers can terminate via RPC 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 there MUST be this state change notification that the subscription has been ended. This indicates that a publisher has suspended a subscription. The state change notification includes the reason for the suspension. A possible reason is the lack of resources to serve it. No further subscribed event records 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 indicates that a previously suspended subscription has been resumed. Subscribed event records generated after the generation of this state change notification will be sent. These state change notifications go to the subscriber (in the case of dynamic subscriptions) and all receivers (in the case of configured subscriptions).This indicates that a subscription, which includes a stop time, has successfully finished passing event records upon the reaching of that stop time.This 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 event records will be sent in sequence as they arise naturally within the system.Container "subscriptions" in the YANG module below 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, 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.A publisher 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 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 SHOULD be used for subscriptions which will have subscription identifiers provided from outside the publisher, and upper half for subscription identifiers assigned by the publisher.No state change notification or nor subscribed event records within notification messages may be sent before the transport layer, including any requried 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.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 user 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 user 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. Subscribers 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-user 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 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)v06 - v07
Clarification on state machine for configured susbcriptions.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