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Versions: (draft-gonzalez-netconf-5277bis) 00 01 draft-ietf-netconf-subscribed-notifications

NETCONF                                                         A. Clemm
Internet-Draft                                        A. Gonzalez Prieto
Intended status: Standards Track                                 E. Voit
Expires: March 15, 2017                                E. Nilsen-Nygaard
                                                             A. Tripathy
                                                           Cisco Systems
                                                             S. Chisholm
                                                                   Ciena
                                                              H. Trevino
                                                           Cisco Systems
                                                      September 11, 2016


                   Subscribing to Event Notifications
                    draft-ietf-netconf-rfc5277bis-00

Abstract

   This document defines capabilities and operations for providing
   asynchronous message notification delivery for notifications, such as
   those defined using YANG.  Notification delivery can occur over a
   variety of protocols used commonly in conjunction with YANG, such as
   NETCONF and RESTCONF.  The capabilities and operations defined in
   this document along with their mapping onto NETCONF transport are
   intended to replace RFC 5277.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 15, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.3.  Solution Overview . . . . . . . . . . . . . . . . . . . .   5
   2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.1.  Event Streams . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Event Stream Discovery  . . . . . . . . . . . . . . . . .   7
     2.3.  Filters . . . . . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Subscription State Model at the Event Server  . . . . . .   7
   3.  Data Model Trees for Event Notifications  . . . . . . . . . .   8
   4.  Dynamic Subscriptions . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Establishing a Subscription . . . . . . . . . . . . . . .  13
     4.2.  Modifying a Subscription  . . . . . . . . . . . . . . . .  13
     4.3.  Deleting a Subscription . . . . . . . . . . . . . . . . .  14
   5.  Configured Subscriptions  . . . . . . . . . . . . . . . . . .  15
     5.1.  Creating a Configured Subscription  . . . . . . . . . . .  15
     5.2.  Establishing a Configured Subscription  . . . . . . . . .  15
     5.3.  Modifying a Configured Subscription . . . . . . . . . . .  17
     5.4.  Deleting a Configured Subscription  . . . . . . . . . . .  17
   6.  Event (Data Plane) Notifications  . . . . . . . . . . . . . .  18
   7.  Control Plane Notifications . . . . . . . . . . . . . . . . .  20
     7.1.  replayComplete  . . . . . . . . . . . . . . . . . . . . .  20
     7.2.  notificationComplete  . . . . . . . . . . . . . . . . . .  20
     7.3.  subscription-started  . . . . . . . . . . . . . . . . . .  20
     7.4.  subscription-modified . . . . . . . . . . . . . . . . . .  21
     7.5.  subscription-terminated . . . . . . . . . . . . . . . . .  21
     7.6.  subscription-suspended  . . . . . . . . . . . . . . . . .  21
     7.7.  subscription-resumed  . . . . . . . . . . . . . . . . . .  21
   8.  Data Model for Event Notifications  . . . . . . . . . . . . .  21
   9.  Backwards Compatibility . . . . . . . . . . . . . . . . . . .  39
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  40
   11. Issues that are currently being worked and resolved . . . . .  41
     11.1.  Unresolved and yet-to-be addressed issues  . . . . . . .  41
     11.2.  Agreement in principal . . . . . . . . . . . . . . . . .  41
     11.3.  Resolved Issues  . . . . . . . . . . . . . . . . . . . .  42
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  42



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   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  42
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  42
     13.2.  Informative References . . . . . . . . . . . . . . . . .  43
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   This document defines mechanisms that provide an asynchronous message
   notification delivery service in a protocol-agnostic manner.  This
   document defines capabilities and operations for providing
   asynchronous message notification delivery for notifications
   including those necessary to establish, monitor, and support
   subscriptions to notification delivery.

   Notification delivery can occur over a variety of protocols used
   commonly in conjunction with YANG, such as NETCONF [RFC6241] (defined
   in [I-D.ietf-netconf-netconf-event-notif]) and Restconf
   [I-D.ietf-netconf-restconf] (defined in
   [I-D.ietf-netconf-restconf-notif]).  The capabilities and operations
   defined in this document are intended to replace RFC 5277, along with
   their mapping onto NETCONF transport.

1.1.  Motivation

   The motivation for this work is to enable the sending of asynchronous
   notification messages that are consistent with the data model
   (content) and security model used within a NETCONF implementation.

   [RFC5277] defines a notification mechanism for NETCONF.  However,
   there are various limitations:

   o  Each subscription requires a separate NETCONF connection, which is
      wasteful.

   o  The only mechanism to terminate a subscription is terminating the
      underlying NETCONF connection.

   o  No ability to modify subscriptions once they have been created.

   o  No ability to notify the receiver of a subscription if the server
      is dropping events.

   o  No mechanism to monitor subscriptions.

   o  No alternative mechanism to create subscriptions via RPCs.  Thus
      the lifetime of the subscription is limited by that of the
      underlaying NETCONF session.




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   o  Predates YANG and defines RPCs, notifications, and data nodes
      outside of the YANG framework.

   The scope of the work aims at meeting the following operational
   needs:

   o  Ability to dynamically or statically subscribe to event
      notifications available on an event server.

   o  Ability to negotiate acceptable dynamic subscription parameters.

   o  Ability to filter the subset of notifications to be pushed with
      stream-specific semantics.

   o  Ability for the notification payload to be interpreted
      independently of the transport protocol.  (In other words, the
      encoded notification fully describes itself.)

   o  Mechanism to communicate the notifications.

   o  Ability to replay locally logged notifications.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   Configured subscription: A subscription installed via a configuration
   interface which persists across reboots.

   Dynamic subscription: A subscription agreed between subscriber and
   event server via create, establish, modify, and delete RPC control
   plane signaling messages.

   Event: Something that happens that may be of interest. (e.g., a
   configuration change, a fault, a change in status, crossing a
   threshold, or an external input to the system.)

   Event notification: A message sent by a server to a receiver
   indicating that an event (of interest to the subscriber) has
   occurred.  Events can trigger notifications if an interested party
   has subscribed to the stream(s) it belongs to.

   Event server: The server being subscribed to, which serves an event
   subscription.





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   Filter: Evaluation criteria, which may be applied against a targeted
   set of objects/events in a subscription.  Information traverses the
   filter only if specified filter criteria are met.

   NACM: NETCONF Access Control Model.

   OAM: Operations, Administration, Maintenance.

   Publisher: An entity responsible for streaming Event Notifications
   per the terms of a Subscriptions

   RPC: Remote Procedure Call.

   Stream (also referred to as "event stream"): A continuous ordered set
   of events grouped under an explicit criteria.

   Subscriber: An entity able to request and negotiate a contract for
   the receipt of event notifications from a NETCONF server.

   Receiver: A target to which an event server pushes event
   notifications.  In many deployments, the receiver and subscriber will
   be the same entity.

   Subscription: A contract between a subscriber and an event server,
   stipulating which information the receiver wishes to have pushed from
   the server without the need for further solicitation.

1.3.  Solution Overview

   This document describes mechanisms for subscribing and receiving
   event notifications from an event server.  This document builds on
   top of the capabilities defined in [RFC5277], extending them, and
   generalizing them to be protocol-agnostic.

   The enhancements over RFC 5277 include the ability to terminate
   subscriptions without terminating the client session, to modify
   existing subscriptions, and to have multiple subscriptions on a
   NETCONF session.

   These enhancements do not affect existing RFC 5277 clients that do
   not support these particular subscription requirements.

   The solution supports subscribing to event notifications using two
   mechanisms.

   1.  Dynamic subscriptions, where a client initiates a subscription
       negotiation with an event server via RPC.  A client initiates a
       negotiation by issuing a subscription request.  If the event



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       server wants to serve this request, it will accept it, and then
       start pushing event notifications as negotiated.  If the event
       server does not wish to serve it as requested, it may respond
       with subscription parameters which it would have accepted.

   2.  Configured subscriptions, which is an optional mechanism that
       enables managing subscriptions via a configuration interface so
       that an event server sends event notifications to a configured
       receiver(s).

   Some key characteristics of configured and dynamic subscriptions
   include:

   o  The lifetime of a dynamic subscription is limited by the lifetime
      of the subscriber session used to establish it.  Typically loss of
      the transport session tears down any dependent dynamic
      subscriptions.

   o  The lifetime of a configured subscription is driven by
      configuration being present on the running configuration.  This
      implies configured subscriptions persist across reboots, and
      persists even when transport is unavailable.  This also means
      configured subscriptions do not support negotiation.

   o  Subscriptions can be modified or terminated at any point of their
      lifetime. configured subscriptions can be modified by any
      configuration client with write rights on the configuration of the
      subscription.

   Note that there is no mixing-and-matching of dynamic and configured
   subscriptions.  Specifically, a configured subscription cannot be
   modified or deleted using RPC.  Similarly, a subscription created via
   RPC cannot be modified through configuration operations.

   The event server may decide to terminate a dynamic subscription at
   any time.  Similarly, it may decide to temporarily suspend the
   sending of event notifications for either configured or dynamic
   subscriptions.  Such termination or suspension may be driven by the
   server running out of resources to serve the subscription, or by
   internal errors on the server.

2.  Solution

2.1.  Event Streams

   An event stream is a set of events available for subscription from a
   server.  It is out of the scope of this document to identify a) how




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   streams are defined, b) how events are defined/generated, and c) how
   events are assigned to streams.

   That said, some event streams will be standardized whereas others may
   be vendor specific.  One standardized event stream is the "NETCONF"
   notification event stream.  The NETCONF event stream contains all
   NETCONF XML event notifications supported by the NETCONF server,
   except for those belonging only to streams that explicitly indicate
   that they must be excluded from the NETCONF stream, such as
   notifications that serve OAM and signaling purposes.

   The following is a high-level description of the flow of a
   notification.  Note that it does not mandate and/or preclude an
   implementation.  As events are raised, they are assigned to streams.
   An event may be assigned to multiple streams.  The event is
   distributed to subscribers and receivers based on the current
   subscriptions and access control.  Access control is needed because
   if any receiver of that subscription does not have permission to
   receive an event, then it never makes it into a notification, and
   processing of the event is completed for that subscription.

2.2.  Event Stream Discovery

   A server maintains a list of available event streams as operational
   data.  This list contains both standardized and vendor-specific event
   streams.  A client can retrieve this list like any other YANG-defined
   data, for example using the <get> operation when using NETCONF.

2.3.  Filters

   An event server implementation SHOULD support the ability to perform
   filtering of notification records per RFC 5277.  (TODO: since 5277 is
   to be obsoleted, we should describe the filter here.)

2.4.  Subscription State Model at the Event Server

   Below is the state machine of a subscription for the event server.
   It is important to note that a subscription doesn't exist at the
   event server until it is accepted and made active.  The mere request
   by a subscriber to establish a subscription is insufficient for that
   asserted subscription to be externally visible via this state
   machine.









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                       .-------.
                       | start |
                       '-------'
                           |
                        establish
                           |
                           |   .----------modify--------------.
                           v   v                              '
                     .-----------.                      .-----------.
          .--------. |           |------>suspend------->|           |
        modify      '|  active   |                      | suspended |
          '--------->|           |<----resume----<------|           |
                     '-----------'                      '-----------'
                           |                                  |
                        delete                             delete
                           |                                  |
                           v                                  |
                       .-------.                              |
                       |  end  |<-----------------------------'
                       '-------'

               Figure 1: Subscription states at event server

   Of interest in this state machine are the following:

   o  Successful <establish-subscription> or <modify-subscription>
      requests put the subscription into an active state.

   o  Failed <modify-subscription> requests will leave the subscription
      in its previous state, with no visible change to any streaming
      updates.

   o  A <delete-subscription> request will delete the entire
      subscription.

3.  Data Model Trees for Event Notifications

   The YANG data model for event notifications is depicted in this
   section.

module: ietf-event-notifications
   +--ro streams
   |  +--ro stream*   notif:stream
   +--rw filters
   |  +--rw filter* [filter-id]
   |     +--rw filter-id    filter-id
   |     +--rw (filter-type)?
   |        +--:(rfc5277)



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   |           +--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



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               +--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)?



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   |           |  +--:(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



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   |  +--ro subscription-id    subscription-id
   |  +--ro stream?            stream
   |  +--ro (filter-type)?
   |  |  +--:(rfc5277)
   |  |  |  +--ro filter
   |  |  +--:(by-reference)
   |  |     +--ro filter-ref?        filter-ref
   |  +--ro startTime?         yang:date-and-time
   |  +--ro stopTime?          yang:date-and-time
   |  +--ro encoding?          encoding
   +---n removed-from-subscription
      +--ro subscription-id    subscription-id

   The data model is structured as follows:

   o  "Streams" contains a list of event streams that are supported by
      the event server and that can be subscribed to.

   o  "Filters" contains a configurable list of filters that can be
      applied to a subscription.  This allows users to reference an
      existing filter definition as an alternative to defining a filter
      inline for each subscription.

   o  "Subscription-config" contains the configuration of configured
      subscriptions.  The parameters of each configured subscription are
      equivalent to the parameters of a dynamic subscription and use the
      same groupings.  In addition, the configured subscriptions specify
      intended receivers and the push source from which to send the
      stream of notification messages.

   o  "Subscriptions" contains a list of all subscriptions on an event
      server, both configured and dynamic.  It can be used do retrieve
      information about the subscriptions which an event server is
      serving.

   The data model also contains a number of notifications that allow an
   event server to signal to the client information about a
   subscription.  Finally, the data model contains a number of RPC
   definitions that are used to manage dynamic subscriptions.

4.  Dynamic Subscriptions

   Dynamic subscriptions are managed via RPC.








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4.1.  Establishing a Subscription

   This operation is an evolution of the "create-subscription" operation
   defined in RFC 5277.  It allows a subscriber to request the creation
   of a subscription both via RPC and configuration operations.  When
   invoking the RPC, establish-subscription permits negotiating the
   subscription terms, changing them dynamically.

   The input parameters of the operation are those of create
   subscription plus:

   o  filter-ref: filters that have been previously (and separately)
      configured can be referenced by a subscription.  This mechanism
      enables the reuse of filters.

   o  encoding: by default, updates are encoded using XML.  Other
      encodings may be supported, such as JSON.

   If the event server cannot satisfy the request, it sends a negative
   <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
   [I-D.ietf-netconf-yang-push], which augments the establish-
   subscription with some additional parameters, including "period".

   Subscription requests will fail if a filter with invalid syntax is
   provided or if the name of a non-existent stream is provided.

4.2.  Modifying a Subscription

   This operation permits modifying the terms of a subscription
   previously established.  Subscriptions created by configuration
   cannot be modified.  Dynamic subscriptions can be modified one or
   multiple times.  If the server accepts the request, it immediately
   starts sending events based on the new terms, completely ignoring the
   previous ones.  If the server rejects the request, the subscription
   remains as prior to the request.  That is, the request has no impact
   whatsoever.  The contents of negative responses to modify-
   subscription requests are the same as in establish subscription
   requests.




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   Dynamic subscriptions established via RPC can only be modified (or
   deleted) via RPC using the same session used to establish it.
   Configured subscriptions cannot be modified (or deleted) using RPCs.
   Instead, configured subscriptions are modified (or deleted) as part
   of regular configuration operations.  Servers MUST reject any
   attempts to modify (or delete) configured subscriptions via RPC.

   The parameters to modify-subscription are those of establish-
   subscription plus a mandatory subscription-id.

   If the event server can satisfy the request, the server sends a
   positive subscription-result.  This response is like that to an
   establish-subscription request without the subscription-id, which
   would be redundant.

   If the event server cannot satisfy the request, the server sends a
   negative subscription-result.  Its contents and semantics are
   identical to those to an establish-subscription request.

4.3.  Deleting a Subscription

   This operation permits canceling a subscription previously
   established.  Created subscriptions cannot be explicitly deleted.  If
   the server accepts the request, it immediately stops sending events
   for the subscription.  If the server rejects the request, all
   subscriptions remain as prior to the request.  That is, the request
   has no impact whatsoever.  A request may be rejected because the
   provided subscription identifier is incorrect.

   Subscriptions created via RPC can only be deleted via RPC using the
   same session used for establishment.  Configured subscriptions cannot
   be deleted using RPCs.  Instead, configured subscriptions are deleted
   as part of regular configuration operations.  Servers MUST reject any
   RPC attempt to delete configured subscriptions.

   The only parameter to delete-subscription is the identifier of the
   subscription to delete.

   If the event server can satisfy the request, the server sends an OK
   element.

   If the event server cannot satisfy the request, the server sends an
   error-rpc element.








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5.  Configured Subscriptions

   A configured subscription is a subscription installed via a
   configuration interface.

   Configured subscriptions persist across reboots, and persist even
   when transport is unavailable.  This also means configured
   subscriptions do not support negotiation.

   Configured subscriptions can be modified by any configuration client
   with write rights on the configuration of the subscription.
   Subscriptions can be modified or terminated at any point of their
   lifetime.

   Supporting configured subscriptions is optional and advertised using
   the "configured-subscriptions" feature.

   In addition to subscription parameters that apply to dynamic
   subscriptions, the following additional parameters apply to
   configured subscriptions:

   o  One or more receiver IP addresses (and corresponding ports)
      intended as the destination for push updates for each
      subscription.  In addition the transport protocol for each
      destination may be defined.

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

5.1.  Creating a Configured Subscription

   Configured subscriptions cannot be created via configuration
   operations.  New clients should use the mechanisms described in
   Section 5.2 for establishing configured subscriptions.

5.2.  Establishing a Configured Subscription

   Subscriptions can be established using configuration operations
   against the top-level subtree subscription-config.  There are two key
   differences between RPC and configuration operations for subscription
   establishment.  Firstly, configuration operations do not support
   negotiation while RPCs do.  Secondly, while RPCs mandate that the
   client establishing the subscription is the only receiver of the
   notifications, configuration operations permit specifying receivers
   independent of any tracked subscriber.  Immediately after a
   subscription is successfully established, the server sends to the




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   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>

                Figure 2: Establish configured subscription

   if the request is accepted, the server would reply:








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   <rpc-reply message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
          <ok/>
   </rpc-reply>

        Figure 3: Response to a successful configured subscription
                               establishment

   if the request is not accepted because the server cannot serve it,
   the server may reply:

   <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>

   Figure 4: Response to a failed configured subscription establishment

5.3.  Modifying a Configured Subscription

   Configured subscriptions can be modified using configuration
   operations against the top-level subtree subscription-config.

   Immediately after a subscription is successfully modified, the server
   sends to the existing receivers a control-plane notification stating
   the subscription has been modified (i.e., subscription-modified).

   If the modification involved adding and/or removing receivers, those
   modified receivers are sent control-plane notifications, indicating
   they have been added (i.e, added-to-subscription, with the same
   contents as a modified-subscription) or removed (i.e., removed-from-
   subscription)

5.4.  Deleting a Configured Subscription

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







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   DELETE /subscription-config/subscription=1922 HTTP/1.1
   Host: example.com

   HTTP/1.1 204 No Content
   Date: Sun, 24 Jul 2016 11:23:40 GMT
   Server: example-server


               Figure 5: Deleting a configured subscription

   Immediately after a subscription is successfully deleted, the event
   server sends to the receivers a control-plane notification stating
   the subscription has been terminated (subscription-terminated).

6.  Event (Data Plane) Notifications

   Once a subscription has been set up, the event server sends
   (asynchronously) the event notifications from the subscribed stream.
   We refer to these as data plane notifications.  For dynamic
   subscriptions set up via RPC operations, event notifications are sent
   over the session used to create or establish the subscription.  For
   configured subscriptions, event notifications are sent over the
   specified connections.

   An event notification is sent to the receiver(s) when an event of
   interest (i.e., meeting the specified filtering criteria) has
   occurred.  An event notification is a complete and well-formed XML
   document.  Note that <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 [RFC3339].  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 [RFC6020]:



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   notification link-failure {
     description "A link failure has been detected";
       leaf if-name {
         type leafref {
           path "/interface/name";
         }
       }
       leaf if-admin-status {
         type admin-status;
       }
       leaf if-oper-status {
         type oper-status;
       }
   }

             Figure 6: Definition of a data plane notification

   <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>

                     Figure 7: Data plane 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>

           Figure 8: Data plane notification using JSON encoding





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7.  Control Plane Notifications

   In addition to data plane notifications, a server may send control
   plane notifications to indicate to receivers that an event related to
   the subscription management has occurred.

   Control plane notifications are unlike other notifications in that
   they are not general-purpose notifications.  They cannot be filtered
   out, and they are delivered only to the receiver of a subscription.
   The definition of control plane notifications is distinct from other
   notifications by making use of a YANG extension tagging them as
   control plane notification.

   Control plane notifications include indications that a replay of
   notifications has been completed, that a subscription is done sending
   notifications because an end time has been reached, and that a
   subscription has started, been modified, been terminated, or been
   suspended.  They are described in the following subsections.

7.1.  replayComplete

   This notification is originally defined in [RFC5277].  It is sent to
   indicate that all of the replay notifications have been sent and must
   not be sent for any other reason.

   In the case of a subscription without a stop time, after the
   <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.

7.2.  notificationComplete

   This notification is originally defined in [RFC5277].  It is sent to
   indicate that a subscription, which includes a stop time, has
   finished passing events.

7.3.  subscription-started

   This notification indicates that a configured subscription has
   started and data updates are beginning to be sent.  This notification
   includes the parameters of the subscription, except for the
   receiver(s) addressing information and push-source information.  Note
   that for RPC-based subscriptions, no such notifications are sent.







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7.4.  subscription-modified

   This notification indicates that a configured subscription has been
   modified successfully.  This notification includes the parameters of
   the subscription, except for the receiver(s) addressing information
   and push-source information.  Note that for RPC-based subscriptions,
   no such notifications are sent.

7.5.  subscription-terminated

   This notification indicates that a subscription has been terminated.
   The notification includes the reason for the termination.  A
   subscription may be terminated by a server or by a client.  The
   server may decide to terminate a subscription when it is running out
   of resources for serving it, an internal error occurs, etc.  Server-
   driven terminations are notified to all receivers.  The management
   plane can also terminate configured subscriptions using configuration
   operations.

   Clients can terminate via RPC subscriptions established via RPC.  In
   such cases, no subscription-terminated notifications are sent.

7.6.  subscription-suspended

   This notification indicates that a server has suspended a
   subscription.  The notification includes the reason for the
   suspension.  A possible reason is the lack of resources to serve it.
   No further data plane notifications will be sent until the
   subscription resumes.  Suspensions are notified to the subscriber (in
   the case of dynamic subscriptions) and all receivers (in the case of
   configured subscriptions).

7.7.  subscription-resumed

   This notification indicates that a previously suspended dubscription
   has been resumed.  Data plane notifications generated in the future
   will be sent after the subscription terms.  Resumptions are notified
   to the subscriber (in the case of dynamic subscriptions) and all
   receivers (in the case of configured subscriptions).

8.  Data Model for Event Notifications

  <CODE BEGINS>
  file "ietf-event-notifications@2016-09-11.yang"
  module ietf-event-notifications {
    namespace
      "urn:ietf:params:xml:ns:yang:ietf-event-notifications";




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    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



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      "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



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        "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.";



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    }

    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



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        "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



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        "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.";



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    }

    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



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            "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 {



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              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 {



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            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;



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        }
      }
    }

    /*
     * 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;



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          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;



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        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 {



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        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.";



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      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.";
      }
    }

    /*



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     * 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;



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          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.";



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        }
        uses subscription-info;
        uses receiver-info {
          if-feature "configured-subscriptions";
        }
        uses push-source-info {
          if-feature "configured-subscriptions";
        }
      }
    }
  }

  <CODE ENDS>

9.  Backwards Compatibility

   Capabilities are advertised in messages sent by each peer during
   session establishment [RFC6241].  Servers supporting the features in
   this document must advertise both capabilities
   "urn:ietf:params:netconf:capability:notification:1.0" and
   "urn:ietf:params:netconf:capability:notification:1.1".

   An example of a hello message by a server during session
   establishment would be:

   <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>

                          Figure 9: Hello message

   Clients that only support [RFC5277] recognize capability
   "urn:ietf:params:netconf:capability:notification:1.0" and ignore
   capability "urn:ietf:params:netconf:capability:notification:1.1".



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   This allows them interacting with the server as per [RFC5277].
   Clients that support the features in this document recognize both
   capabilities.  This allows them interacting with the server as per
   this document.

   Note that to support backwards compatibility, the yang models in this
   document include two types of naming conventions.  That used in
   [RFC5277], e.g., replayComplete; and that commonly used in yang
   models, e.g., subscription-started.

10.  Security Considerations

   The security considerations from the base NETCONF document [RFC6241]
   also apply to the notification capability.

   The <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



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   only terminate or refuse any transport sessions from the publisher.
   In addition, the NETCONF Authorization Control Model [RFC6536] SHOULD
   be used to control and restrict authorization of subscription
   configuration.  This control models permits specifying per-user
   permissions to receive specific event notification types.  The
   permissions are specified as a set of access control rules.

   Note that streams can define additional authorization requirements.
   For instance, in [I-D.ietf-netconf-yang-push], each of the elements
   in its data plane notifications must also go through access control.

11.  Issues that are currently being worked and resolved

11.1.  Unresolved and yet-to-be addressed issues

   EN1 - Definition of basic set of Stream types.  What streams are
   provided and what do they contain (includes default 5277 stream).

   EN2 - Clarify interplay between filter definitions and different
   streams.  Includes information in subtrees of event payloads.

   EN3 - Mechanisms for diagnostics, e.g. deal with dropped updates,
   monitoring when they occur, etc

   EN4 - How to allow for seamless integration with non-standard
   encodings and transports (like GPB/GRPC).  Specify requirements
   encoding and transport must meet, provide examples.

   EN7 - Detecting loss of a sequential update notification, and
   mechanisms to resend.  Implications to transports must be thought
   through.

11.2.  Agreement in principal

   EN6 - Stream discovery.  Allow to discover additional stream
   properties.

   EN9 - Multiple receivers per Configured Subscription is ok.

   EN10 - Replay support will be provided for selected stream types
   (modify vs. delete)

   EN11 - Required layering security requirements/considerations will be
   added into the YANG model for Configured Subscriptions.  It will be
   up to the transport to meet these requirements.

   EN12 - Test-only option for a subscription is desired.  But it still
   needs to be defined.



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   EN13 - RFC6241 Subtree-filter definition in 5277bis cannot apply to
   elements of an event.  Must explicitly define how 6241 doesn't apply
   filtering within a 5277bis event.

   EN14 - Ensure that Configured Subscriptions are fully defined in YANG
   model.

11.3.  Resolved Issues

   EN5 - This draft obsoletes 5277, as opposed to being in parallel with
   it

   EN8 - No mandatory transport

   EN15 - Term for Dynamic and Static Subscriptions (move to
   "Configured")

12.  Acknowledgments

   For their valuable comments, discussions, and feedback, we wish to
   acknowledge Andy Bierman, Yang Geng, Peipei Guo, Susan Hares, Tim
   Jenkins, Balazs Lengyel, Kent Watsen, and Guangying Zheng.

13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <http://www.rfc-editor.org/info/rfc3339>.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
              <http://www.rfc-editor.org/info/rfc5277>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://www.rfc-editor.org/info/rfc6020>.







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   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <http://www.rfc-editor.org/info/rfc6536>.

13.2.  Informative References

   [I-D.ietf-netconf-netconf-event-notif]
              Gonzalez Prieto, Alberto., Clemm, Alexander., Voit, Eric.,
              Nilsen-Nygaard, E., Tripathy, A., Chisholm, S., and H.
              Trevino, "NETCONF support for event notifications", August
              2016, <https://datatracker.ietf.org/doc/draft-ietf-
              netconf-netconf-event-notifications/>.

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", I-D draft-ietf-netconf-restconf-13, April 2016.

   [I-D.ietf-netconf-restconf-notif]
              Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen-
              Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and
              HTTP transport for event notifications", August 2016,
              <https://datatracker.ietf.org/doc/draft-ietf-netconf-
              restconf-notif/>.

   [I-D.ietf-netconf-yang-push]
              Clemm, Alexander., Gonzalez Prieto, Alberto., Voit, Eric.,
              Tripathy, A., and E. Nilsen-Nygaard, "Subscribing to YANG
              datastore push updates", June 2016,
              <https://datatracker.ietf.org/doc/draft-ietf-netconf-yang-
              push/>.

Authors' Addresses

   Alexander Clemm
   Cisco Systems

   Email: ludwig@clemm.org








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   Alberto Gonzalez Prieto
   Cisco Systems

   Email: albertgo@cisco.com


   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com


   Einar Nilsen-Nygaard
   Cisco Systems

   Email: einarnn@cisco.com


   Ambika Prasad Tripathy
   Cisco Systems

   Email: ambtripa@cisco.com


   Sharon Chisholm
   Ciena

   Email: schishol@ciena.com


   Hector Trevino
   Cisco Systems

   Email: htrevino@cisco.com

















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