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Versions: (RFC 5277) 00 01 02 draft-ietf-netconf-rfc5277bis

NETCONF                                               A. Gonzalez Prieto
Internet-Draft                                                  A. Clemm
Intended status: Standards Track                                 E. Voit
Expires: December 17, 2016                             E. Nilsen-Nygaard
                                                             A. Tripathy
                                                           Cisco Systems
                                                             S. Chisholm
                                                                   Ciena
                                                              H. Trevino
                                                           Cisco Systems
                                                           June 15, 2016


            Subscribing to YANG-Defined Event Notifications
                   draft-gonzalez-netconf-5277bis-02

Abstract

   This document defines capabilities and operations for providing
   asynchronous message notification delivery for notifications 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 (to be specified in a
   separate document, but still included in the current document
   version) are intended to obsolete 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 December 17, 2016.








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Copyright Notice

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

   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 . . . . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Solution Overview . . . . . . . . . . . . . . . . . . . .   6
   2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     2.1.  Event Streams . . . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Event Stream Discovery  . . . . . . . . . . . . . . . . .   7
     2.3.  Default Event Stream  . . . . . . . . . . . . . . . . . .   8
     2.4.  Filters . . . . . . . . . . . . . . . . . . . . . . . . .   8
     2.5.  Subscription State Model at the Publisher . . . . . . . .   8
     2.6.  Data Model Trees for Event Notifications  . . . . . . . .   9
     2.7.  Creating a Subscription . . . . . . . . . . . . . . . . .  13
     2.8.  Establishing a Subscription . . . . . . . . . . . . . . .  14
   3.  Modifying a Subscription  . . . . . . . . . . . . . . . . . .  15
   4.  Deleting a Subscription . . . . . . . . . . . . . . . . . . .  16
   5.  Configured Subscriptions  . . . . . . . . . . . . . . . . . .  17
     5.1.  Creating a Configured Subscription  . . . . . . . . . . .  17
     5.2.  Establishing a Configured Subscription  . . . . . . . . .  17
     5.3.  Modifying a Configured Subscription . . . . . . . . . . .  19
     5.4.  Deleting a Configured Subscription  . . . . . . . . . . .  19
   6.  Event (Data Plane) Notifications  . . . . . . . . . . . . . .  20
   7.  Control Plane Notifications . . . . . . . . . . . . . . . . .  22
     7.1.  replayComplete  . . . . . . . . . . . . . . . . . . . . .  22
     7.2.  notificationComplete  . . . . . . . . . . . . . . . . . .  23
     7.3.  subscription-started  . . . . . . . . . . . . . . . . . .  23
     7.4.  subscription-modified . . . . . . . . . . . . . . . . . .  23
     7.5.  subscription-terminated . . . . . . . . . . . . . . . . .  23
     7.6.  subscription-suspended  . . . . . . . . . . . . . . . . .  23
     7.7.  subscription-resumed  . . . . . . . . . . . . . . . . . .  24
   8.  Subscription Management . . . . . . . . . . . . . . . . . . .  24
   9.  Data Models for Event Notifications . . . . . . . . . . . . .  25



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     9.1.  Data Model for RFC5277 (netmod namespace) . . . . . . . .  25
     9.2.  Data Model for RFC5277 (netconf namespace)  . . . . . . .  28
     9.3.  Data Model for RFC5277-bis Extensions . . . . . . . . . .  32
   10. Backwards Compatibility . . . . . . . . . . . . . . . . . . .  50
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  51
   12. Issues that are currently being worked and resolved . . . . .  52
     12.1.  Unresolved and yet-to-be addressed issues  . . . . . . .  52
     12.2.  Agreement in principal . . . . . . . . . . . . . . . . .  52
     12.3.  Resolved Issues  . . . . . . . . . . . . . . . . . . . .  53
     12.4.  Editorial To-Dos . . . . . . . . . . . . . . . . . . . .  53
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  53
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  53
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  53
     14.2.  Informative References . . . . . . . . . . . . . . . . .  54
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  54

1.  Introduction

   This document defines mechanisms that provide an asynchronous message
   notification delivery service for the NETCONF protocol .  This is an
   optional capability built on top of the base NETCONF definition.
   This document defines capabilities and operations for providing
   asynchronous message notification delivery for notifications defined
   using YANG, including capabilities and operations 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] and
   Restconf [I-D.ietf-netconf-restconf].  The capabilities and
   operations defined in this document along with their mapping onto
   NETCONF transport (to be specified in a separate document, but still
   included in the current document version) are intended to obsolete
   RFC 5277.

   Editor's note: The current version of this document specifies both
   capabilities and operations for providing asynchronous notification
   delivery, as well as mapping of those capabilities and operations
   onto NETCONF.  The transport mapping to NETCONF will be moved into a
   separate document and will be removed in future revisions of this
   document.

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.




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   [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.

   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 a NETCONF agent.

   o  Ability to negotiate acceptable dynamic subscription parameters.

   o  Ability to support multiple subscriptions over a single NETCONF
      session.

   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 NETCONF transport protocol.  (In other words,
      the encoded notification fully describes itself.)

   o  Mechanism to communicate the notifications.

   o  Ability to replay locally logged notifications.

   o  Backwards compatible with RFC 5277 implementations.





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   o  Define in YANG, the RPCs, notifications, and data nodes in RFC
      5277.

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].

   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.

   Stream (also referred to as "event stream"): A continuous flow of
   event, status, state, or other information.

   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 a NETCONF server pushes event
   notifications.  In many deployments, the receiver and subscriber will
   be the same entity.

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

   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.

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

   Configured subscription: A subscription installed via a configuration
   interface.

   Operation: In this document, this term refers to NETCONF protocol
   operations [RFC6241] defined in support of NETCONF notifications.

   NACM: NETCONF Access Control Model.




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   RPC: Remote Procedure Call.

1.3.  Solution Overview

   This document describes mechanisms for subscribing and receiving
   event notifications from a NETCONF server.  This document enhances
   the capabilities of RFC 5277 while maintaining backwards capability
   with existing implementations.  It is intended that a final version
   of this document might obsolete RFC 5277.

   The enhancements over [RFC5277] 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 [RFC5277] clients that do not
   support these particular subscription requirements.

   The solution supports subscribing to event notifications using two
   mechanisms.

   1.  Dynamic subscriptions, where a NETCONF client initiates a
       subscription negotiation with a NETCONF server.  Here a client
       initiates a negotiation by issuing a subscription request.  If
       the agent wants to serve this request, it will accept it, and
       then start pushing event notifications as negotiated.  If the
       agent 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 a NETCONF agent sends event notifications to given
       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.




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   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.

   o  A NETCONF agent can support multiple dynamic subscriptions
      simultaneously in the context of a single NETCONF session.  (This
      requires supporting interleaving.)  The termination of any of
      those subscriptions does not imply the termination of NETCONF
      transport session.

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

   The NETCONF agent may decide to terminate a dynamic subscription at
   any time.  Similarly the NETCONF agent 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 agent 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
   streams are defined, b) how events are defined/generated, and c) how
   events are assigned to streams.

   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.  A client can retrieve this list like any other YANG-defined
   data, for example using the <get> operation when using NETCONF.




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2.3.  Default Event Stream

   A NETCONF server implementation supporting the notification
   capability MUST support the "NETCONF" notification event stream.
   This 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.  The exact string "NETCONF" is used during the advertisement
   of stream support during the <get> operation on <streams> and during
   the <create-subscription> and <establish-subscription> operations.

2.4.  Filters

   A NETCONF Server implementation SHOULD support the ability to perform
   filtering of notification records per RFC 5277.

2.5.  Subscription State Model at the Publisher

   Below is the state machine of a subscription for the publisher.  It
   is important to note that 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.

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

                Figure 1: Subscription states at publisher




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   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.

2.6.  Data Model Trees for Event Notifications

   The YANG data models for event notifications are depicted in the
   following sections.

2.6.1.  Data Model Tree for RFC5277 (netconf namespace)

   module: ietf-5277-netconf
   rpcs:
      +---x create-subscription
         +--ro input
            +--ro stream?      string
            +--ro (filter-type)?
            |  +--:(rfc5277)
            |     +--ro filter
            +--ro startTime?   yang:date-and-time
            +--ro stopTime?    yang:date-and-time

2.6.2.  Data Model Tree for RFC5277 (netmod namespace)

   module: ietf-5277-netmod
      +--rw netconf
         +--rw streams
            +--rw stream* [name]
               +--rw name                     string
               +--rw description              string
               +--rw replaySupport            boolean
               +--rw replayLogCreationTime    yang:date-and-time
               +--rw replayLogAgedTime        yang:date-and-time
   notifications:
      +---n replayComplete
      +---n notificationComplete







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2.6.3.  Data Model for RFC5277-bis Extensions

module: ietf-event-notifications
   +--ro streams
   |  +--ro stream*   notif:stream
   +--rw filters
   |  +--rw filter* [filter-id]
   |     +--rw filter-id    filter-id
   |     +--rw (filter-type)?
   |        +--:(rfc5277)
   |           +--rw filter
   +--rw subscription-config {configured-subscriptions}?
   |  +--rw subscription* [subscription-id]
   |     +--rw subscription-id     subscription-id
   |     +--rw stream?             stream
   |     +--rw (filter-type)?
   |     |  +--:(rfc5277)
   |     |  |  +--rw filter
   |     |  +--:(by-reference)
   |     |     +--rw filter-ref?         filter-ref
   |     +--rw startTime?          yang:date-and-time
   |     +--rw stopTime?           yang:date-and-time
   |     +--rw encoding?           encoding
   |     +--rw receivers
   |     |  +--rw receiver* [address]
   |     |     +--rw address     inet:host
   |     |     +--rw port        inet:port-number
   |     |     +--rw protocol?   transport-protocol
   |     +--rw (push-source)?
   |        +--:(interface-originated)
   |        |  +--rw source-interface?   if:interface-ref
   |        +--:(address-originated)
   |           +--rw source-vrf?         uint32
   |           +--rw source-address      inet:ip-address-no-zone
   +--ro subscriptions
      +--ro subscription* [subscription-id]
         +--ro subscription-id            subscription-id
         +--ro configured-subscription?   empty {configured-subscriptions}?
         +--ro subscription-status?       subscription-status
         +--ro stream?                    stream
         +--ro (filter-type)?
         |  +--:(rfc5277)
         |  |  +--ro filter
         |  +--:(by-reference)
         |     +--ro filter-ref?                filter-ref
         +--ro startTime?                 yang:date-and-time
         +--ro stopTime?                  yang:date-and-time
         +--ro encoding?                  encoding



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         +--ro receivers
         |  +--ro receiver* [address]
         |     +--ro address     inet:host
         |     +--ro port        inet:port-number
         |     +--ro protocol?   transport-protocol
         +--ro (push-source)?
            +--:(interface-originated)
            |  +--ro source-interface?          if:interface-ref
            +--:(address-originated)
               +--ro source-vrf?                uint32
               +--ro source-address             inet:ip-address-no-zone
augment /netmod-notif:replayComplete:
   +---- subscription-id?   subscription-id
augment /netmod-notif:notificationComplete:
   +---- subscription-id?   subscription-id
augment /netmod-notif:netconf/netmod-notif:streams:
   +--rw exclude-from-NETCONF-stream?   empty
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



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   |  |  +---w (filter-type)?
   |  |  |  +--:(rfc5277)
   |  |  |  |  +---w filter
   |  |  |  +--:(by-reference)
   |  |  |     +---w filter-ref?        filter-ref
   |  |  +---w startTime?         yang:date-and-time
   |  |  +---w stopTime?          yang:date-and-time
   |  |  +---w encoding?          encoding
   |  +--ro output
   |     +--ro subscription-result    subscription-result
   |     +--ro (result)?
   |        +--:(success)
   |        |  +--ro subscription-id        subscription-id
   |        +--:(no-success)
   |           +--ro stream?                stream
   |           +--ro (filter-type)?
   |           |  +--:(rfc5277)
   |           |  |  +--ro filter
   |           |  +--:(by-reference)
   |           |     +--ro filter-ref?            filter-ref
   |           +--ro startTime?             yang:date-and-time
   |           +--ro stopTime?              yang:date-and-time
   |           +--ro encoding?              encoding
   +---x delete-subscription
      +---w input
      |  +---w subscription-id    subscription-id
      +--ro output
         +--ro subscription-result    subscription-result
notifications:
   +---n 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



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

2.7.  Creating a Subscription

   Editor's note: The following section needs updating.  NETCONF mapping
   will move to a separate document.

   This operation is fully defined in [RFC5277].  It allows a subscriber
   to request the creation of a dynamic subscription.  If successful,
   the subscription remains in effect for the duration of the NETCONF
   session.

   This operation is included in the document for supporting backwards
   compatibility with [RFC5277] clients.  New clients are expected not
   to use this operation, but establish subscriptions as defined in
   Section 2.8

2.7.1.  Parameters

   The input parameters of the operation are:

   o  stream: An optional parameter that indicates which stream of
      events is of interest.  If not present, events in the default
      NETCONF stream will be sent.




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   o  filter: An optional parameter that indicates which subset of all
      possible events is of interest.  The format of this parameter is
      the same as that of the filter parameter in the NETCONF protocol
      operations.  If not present, all events not precluded by other
      parameters will be sent.

   o  startTime: An optional parameter used to trigger the replay
      feature and indicate that the replay should start at the time
      specified.  If startTime is not present, this is not a replay
      subscription.  It is not valid to specify start times that are
      later than the current time.  If the startTime specified is
      earlier than the log can support, the replay will begin with the
      earliest available notification.  Implementations must support
      time zones.

   o  stopTime: An optional parameter used with the optional replay
      feature to indicate the newest notifications of interest.  If
      stopTime is not present, the notifications will continue until the
      subscription is terminated.  Must be used with and be later than
      startTime.  Implementations must support time zones.

   If the server can satisfy the request, it sends a positive
   acknowledgement.

   If the request cannot be completed for any reason, an error is
   returned along with an error reason.  Subscription requests can fail
   for several reasons, including if a filter with invalid syntax is
   provided or if the name of a non-existent stream is provided.  Other
   errors include:

   o  The optional replay feature is requested but the server does not
      support it

   o  A stopTime is requested that is earlier than the specified
      startTime

   o  A startTime is requested that is later than the current time

2.8.  Establishing a Subscription

   Editor's note: The following section needs updating.  NETCONF mapping
   will move to a separate document.

   This operation is an evolution of the create subscription operation.
   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 and enabling multiple subscriptions overs a



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   single NETCONF session (if interleaving [RFC6241] is supported), and
   canceling subscriptions without terminating the NETCONF session.

   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 NETCONF server cannot satisfy the request, the server 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.

3.  Modifying a Subscription

   Editor's note: The following section needs updating.  NETCONF mapping
   will move to a separate document.

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

   Dynamic subscriptions established via RPC can only be modified (or
   deleted) via RPC using the same session used to establish it.



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   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 NETCONF 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 NETCONF 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.  Deleting a Subscription

   Editor's note: The following section needs updating.  NETCONF mapping
   will move to a separate document.

   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 NETCONF server can satisfy the request, the server sends an OK
   element.

   If the NETCONF 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 NETCONF:







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   <rpc message-id="101"
          xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
           <target>
               <running/>
           </target>
           <subscription-config
           xmlns:xc="urn:ietf:params:xml:ns:netconf:notification:1.1">
               <subscription xc:operation="delete">
                   <subscription-id>
                       1922
                   </subscription-id >
              </subscription>
           </subscription-config>
       </edit-config>
   </rpc>

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


               Figure 5: Deleting a configured subscription

   Immediately after a subscription is successfully deleted, the 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 NETCONF 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 NETCONF 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.





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   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]:

   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




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   <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

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.
   They are thus not part of the regular NETCONF event stream.  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.




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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.

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).






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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.  Subscription Management

   Below is the state machine for the server.  It is important to note
   that a subscription does not exist at the agent until it is accepted
   and made active.

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

   Of interest in this state machine are the following:

   o  Successful <create-subscription>, <establish-subscription> or
      <modify-subscription> actions must put the subscription into an
      active state.

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

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




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9.  Data Models for Event Notifications

9.1.  Data Model for RFC5277 (netmod namespace)

   <CODE BEGINS>
   file "ietf-5277-netmod@2016-06-15.yang"
   module ietf-5277-netmod {
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-5277-netmod";
       // TODO: examples in the draft consider the namespace below
       //       which follows the namespace format in 5277
       // "urn:ietf:params:xml:ns:netmod:notification";
     prefix netmod-notif;

     import ietf-yang-types {
       prefix yang;
     }

     organization "IETF";
     contact
       "WG Web:   <http://tools.ietf.org/wg/netmod/>
        WG List:  <mailto:netmod@ietf.org>


        WG Chair: Juergen Schoenwaelder
                  <mailto:j.schoenwaelder@jacobs-university.de>
        WG Chair: Tom Nadeau
                   <mailto:tnadeau@lucidvision.com>

        Editor:   Alberto Gonzalez Prieto
                  <mailto:albertgo@cisco.com>

        Editor:   Alexander Clemm
                  <mailto:alex@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>";

     description
       "Model for RPC in RFC 5277: NETCONF Event Notifications";

     revision 2016-06-15 {



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       description
         "Model for data nodes and notifications in RFC 5277:
          NETCONF Event Notifications";
       reference
         "RFC 5277: NETCONF Event Notifications";
     }


     /*
      * EXTENSIONS
      */

     extension control-plane-notif {
       description
         "This statement applies only to notifications.
          It indicates that the notification is a control-plane
          notification and therefore it does not generate an
          event stream.";
     }


     /*
      * DATA NODES
      */
     container netconf {
       description
         "Netconf container as defined in RFC 5277.";
       reference
         "RFC 5277: NETCONF Event Notifications";

       container streams {
         // TODO: should be config false?. That breaks the leafref
         // from the config subscriptions config false;
         description
           "The container with the set of available event streams.";
         reference
           "RFC 5277: NETCONF Event Notifications";

         list stream {
           must "1 = count(./name == 'NETCONF')" {
             description
               "The list must contain a NETCONF stream.
                A NETCONF server implementation supporting the
                notification capability MUST support the
                'NETCONF' notification event stream. This stream
                contains all NETCONF XML event notifications supported
                by the NETCONF server.
                The exact string 'NETCONF' is used during the



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                advertisement of stream support during the <get>
                operation on <streams> and during the
                <create-subscription> operation.";
           }
           key "name";
           description
             "The list available event streams.";
           leaf name {
             type string;
             description
               "The name of the event stream.
                If this is the default NETCONF stream, this must have
                the value 'NETCONF'.";
           }
           leaf description {
             type string;
             mandatory true;
             description
               "A description of the event stream, including such
                information as the type of events that are sent over
                this stream.";
           }
           leaf replaySupport {
             type boolean;
             mandatory true;
             description
               "An indication of whether or not event replay is
                available on this stream.";
           }
           leaf replayLogCreationTime {
             when "../replaySupport" {
               description
                 "This object MUST be present if replay is supported.";
             }
             type yang:date-and-time;
             mandatory true;
             description
               "The timestamp of the creation of the log used to
                support the replay function on this stream.
                Note that this might be earlier then the earliest
                available notification in the log.  This object
                is updated if the log resets for some reason.
                This object MUST be present if replay is supported.";
           }
           leaf replayLogAgedTime {
             when "current()/../replaySupport" {
               description
                 "This object MUST be present if replay is supported



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                 and any notifications have been aged out of the log.";
             }
             type yang:date-and-time;
             mandatory true;
             description
               "The timestamp of the last notification aged
                out of the log. This object MUST be present
                if replay is supported and any notifications
                have been aged out of the log.";
           }
         } // list stream
       } // container streams
     } // container netconf


     /*
      * NOTIFICATIONS
      */

     notification replayComplete {
       netmod-notif:control-plane-notif;
       description
         "This notification is sent to signal the end of a replay
          portion of a subscription.";
     }

     notification notificationComplete {
       netmod-notif:control-plane-notif;
       description
         "This notification is sent to signal the end of a notification
          subscription.  It is sent in the case that stopTime was
          specified during the creation of the subscription.";
     }
   }

   <CODE ENDS>

9.2.  Data Model for RFC5277 (netconf namespace)

   <CODE BEGINS>
   file "ietf-5277-netconf@2016-06-15.yang"
   module ietf-5277-netconf {
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-5277-netconf";
       // TODO: examples in the draft consider the namespace below
       //       which follows the namespace format in 5277
       // "urn:ietf:params:xml:ns:netconf:notification:1.0";
     prefix notif;



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     import ietf-yang-types {
       prefix yang;
     }

     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:   Alberto Gonzalez Prieto
                  <mailto:albertgo@cisco.com>

        Editor:   Alexander Clemm
                  <mailto:alex@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>";

     description
       "Model for RPCs and Notifications in RFC 5277: NETCONF Event
        Notifications";

     revision 2016-06-15 {
       description
         "Model for RPC in RFC 5277: NETCONF Event Notifications";
       reference
         "RFC 5277: NETCONF Event Notifications";
     }

     /*
      * IDENTITIES
      */

     identity stream {
       description
         "Base identity to represent a generic stream of event



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          notifications.";
     }

     identity NETCONF {
       base stream;
       description
         "Default NETCONF event stream, containing events based on
          notifications defined as YANG modules that are supported
          by the system.";
     }

     /*
      * TYPEDEFS
      */

     typedef stream {
       type identityref {
         base stream;
       }
       description
         "Specifies a system-provided datastream.";
     }

     /*
      * GROUPINGS
      */

     grouping base-filter {
       description
         "This grouping defines the base for filters for
          notification events.
          It includes the filter defined in 5277 and
          it enables extending filtering to other
          types of filters";
       choice filter-type {
         description
           "A filter needs to be a single filter of a given type.
            Mixing and matching of multiple filters does not occur
            at the level of this grouping.";
         case rfc5277 {
           anyxml filter {
             description
               "Filter per RFC 5277. Notification filter.
               If a filter element is specified to look for data of a
               particular value, and the data item is not present
               within a particular event notification for its value to
               be checked against, the notification will be filtered
               out. For example, if one were to check for



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               'severity=critical' in a configuration event
               notification where this field was not supported, then
               the notification would be filtered out. For subtree
               filtering, a non-empty node set means that the filter
               matches.  For XPath filtering, the mechanisms defined
               in [XPATH] should be used to convert the returned
               value to boolean.";
           }
         }
       }
     }

     grouping subscription-info-5277 {
       description
         "This grouping describes the information in a 5277
          subscription.";
       leaf stream {
         type stream;
         default "NETCONF";
         description
           "Indicates which stream of events is of interest.
            If not present, events in the default NETCONF stream
            will be sent.";
       }
       uses base-filter;
       leaf startTime {
         type yang:date-and-time;
         description
           "Used to trigger the replay feature
            and indicate that the replay should start at the time
            specified.  If <startTime> is not present, this is not a
            replay subscription.  It is not valid to specify start
            times that are later than the current time.  If the
            <startTime> specified is earlier than the log can support,
            the replay will begin with the earliest available
            notification.  This parameter is of type dateTime and
            compliant to [RFC3339].  Implementations must
            support time zones.";
       }
       leaf stopTime {
         type yang:date-and-time;
         must "current()  > ../startTime" {
           description
             "stopTime must be used with and be later than <startTime>";
         }
         description
           "Used with the optional replay feature to indicate the
            newest notifications of interest.  If <stopTime> is



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            not present, the notifications will continue until the
            subscription is terminated.  Must be used with and be
            later than <startTime>.  Values of <stopTime> in the
            future are valid.  This parameter is of type dateTime and
            compliant to [RFC3339].  Implementations must support time
            zones.";
       }
     }


     /*
      * RPCs
      */

     rpc create-subscription {
       description
         "This operation initiates an event notification subscription
          that will send asynchronous event notifications to the
          initiator of the command until the subscription terminates.";
       input {
         uses subscription-info-5277;
       }
     }
   }

   <CODE ENDS>

9.3.  Data Model for RFC5277-bis Extensions

  <CODE BEGINS>
  file "ietf-event-notifications@2016-06-15.yang"
  module ietf-event-notifications {
    namespace
      "urn:ietf:params:xml:ns:yang:ietf-event-notifications";
      // TODO: examples in the draft consider the namespace below
      //       which follows the namespace format in 5277
      // "urn:ietf:params:xml:ns:netconf:notification:1.1";
    prefix notif-bis;


    import ietf-inet-types {
      prefix inet;
    }
    import ietf-5277-netmod {
      prefix netmod-notif;
    }
    import ietf-5277-netconf {
      prefix notif;



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    }
    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:   Alberto Gonzalez Prieto
                 <mailto:albertgo@cisco.com>

       Editor:   Alexander Clemm
                 <mailto:alex@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>";

    description
      "This module contains conceptual YANG specifications
       for NETCONF Event Notifications.";

    revision 2016-06-15 {
      description
        "Initial version. Model for NETCONF Notifications (bis)";
      reference
        "RFC XXXX: NETCONF Event Notifications";
    }


    /*
     * FEATURES
     */

    feature json {



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      description
        "This feature indicates that JSON encoding of notifications
         is supported.";
    }

    feature configured-subscriptions {
      description
        "This feature indicates that management plane configuration
         of subscription is supported.";
    }

    /*
     * IDENTITIES
     */

    /* Identities for subscription results */
    identity subscription-result {
      description
        "Base identity for RPC responses to requests surrounding
         management (e.g. creation, modification, deletion) of
         subscriptions.";
    }

    identity ok {
      base subscription-result;
      description
        "OK - RPC was successful and was performed as requested.";
    }

    identity error {
      base subscription-result;
      description
        "RPC was not successful.
         Base identity for error return codes.";
    }

    identity error-no-such-subscription {
      base error;
      description
        "A subscription with the requested subscription ID
         does not exist.";
    }

    identity error-no-such-option {
      base error;
      description
        "A requested parameter setting is not supported.";
    }



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    identity error-insufficient-resources {
      base error;
      description
        "The server has insufficient resources to support the
         subscription as requested.";
    }

    identity error-configured-subscription {
      base error;
      description
        "Cannot apply RPC to a configured subscription, i.e.
         to a subscription that was not established via RPC.";
    }

    identity error-other {
      base error;
      description
        "An unspecified error has occurred (catch all).";
    }

    /* Identities for subscription stream status */
    identity subscription-stream-status {
      description
        "Base identity for the status of subscriptions and
         datastreams.";
    }

    identity active {
      base subscription-stream-status;
      description
        "Status is active and healthy.";
    }

    identity inactive {
      base subscription-stream-status;
      description
        "Status is inactive, for example outside the
         interval between start time and stop time.";
    }

    identity suspended {
      base subscription-stream-status;
      description
        "The status is suspended, meaning that the push server
         is currently unable to provide the negotiated updates
         for the subscription.";
    }




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    identity in-error {
      base subscription-stream-status;
      description
        "The status is in error or degraded, meaning that
         stream and/or subscription is currently unable to provide
         the negotiated notifications.";
    }

    /* Identities for subscription errors */
    identity subscription-errors {
      description
        "Base identity for subscription error status.
         This identity is not to be confused with error return
         codes for RPCs";
    }

    identity internal-error {
      base subscription-errors;
      description
        "Subscription failures caused by server internal error.";
    }

    identity no-resources {
      base subscription-errors;
      description
        "Lack of resources, e.g. CPU, memory, bandwidth";
    }

    identity subscription-deleted {
      base subscription-errors;
      description
        "The subscription was terminated because the subscription
         was deleted.";
    }

    identity other {
      base subscription-errors;
      description
        "Fallback reason - any other reason";
    }

    /* Identities for encodings */
    identity encodings {
      description
        "Base identity to represent data encodings";
    }

    identity encode-xml {



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      base encodings;
      description
        "Encode data using XML";
    }

    identity encode-json {
      base encodings;
      description
        "Encode data using JSON";
    }

    /* Identities for transports */
    identity transport {
      description
        "An identity that represents a transport protocol for event
         notifications";
    }

    identity netconf {
      base transport;
      description
        "Netconf notifications as a transport.";
    }

    /*
     * TYPEDEFs
     */

    typedef subscription-id {
      type uint32;
      description
        "A type for subscription identifiers.";
    }

    typedef filter-id {
      type uint32;
      description
        "A type to identify filters which can be associated with a
         subscription.";
    }

    typedef subscription-result {
      type identityref {
        base subscription-result;
      }
      description
        "The result of a subscription operation";
    }



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    typedef subscription-term-reason {
      type identityref {
        base subscription-errors;
      }
      description
        "Reason for a server to terminate a subscription.";
    }

    typedef subscription-susp-reason {
      type identityref {
        base subscription-errors;
      }
      description
        "Reason for a server to suspend a subscription.";
    }

    typedef encoding {
      type identityref {
        base encodings;
      }
      description
        "Specifies a data encoding, e.g. for a data subscription.";
    }

    typedef subscription-status {
      type identityref {
        base subscription-stream-status;
      }
      description
        "Specifies the status of a subscription or datastream.";
    }

    typedef transport-protocol {
      type identityref {
        base transport;
      }
      description
        "Specifies transport protocol used to send notifications to a
         receiver.";
    }

    typedef push-source {
      type enumeration {
        enum "interface-originated" {
          description
            "Notifications will be sent from a specific interface on a
             NETCONF server";
        }



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        enum "address-originated" {
          description
            "Notifications will be sent from a specific address on a
             NETCONF server";
        }
      }
      description
        "Specifies from where notifications will be sourced when
         being sent by the NETCONF server.";
    }

    typedef filter-ref {
      type leafref {
        path "/notif-bis:filters/notif-bis:filter/notif-bis:filter-id";
      }
      description
        "This type is used to reference a filter.";
    }

    /*
     * GROUPINGS
     */

    grouping subscription-info {
      description
        "This grouping describes basic information concerning a
         subscription.";
      uses notif:subscription-info-5277 {
        augment "filter-type" {
          description
            "Post-5277 subscriptions allow references to existing
             filters";
          case by-reference {
            description
              "Incorporate a filter that has been configured
               separately.";
            leaf filter-ref {
              type filter-ref;
              description
                "References filter which is associated with the
                 subscription.";
            }
          }
        }
      }
      leaf encoding {
        type encoding;
        default "encode-xml";



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        description
          "The type of encoding for the subscribed data.
           Default is XML";
      }
    }

    grouping push-source-info {
      description
        "Defines the sender source from which notifications
         for a configured subscription are sent.";
      choice push-source {
        description
          "Identifies the egress interface on the Publisher from
           which notifications will or are being sent.";
        case interface-originated {
          description
            "When the push source is out of an interface on the
             Publisher established via static configuration.";
          leaf source-interface {
            type if:interface-ref;
            description
              "References the interface for notifications.";
          }
        }
        case address-originated {
          description
            "When the push source is out of an IP address on the
             Publisher established via static configuration.";
          leaf source-vrf {
            type uint32 {
              range "16..1048574";
            }
            description
              "Label of the vrf.";
          }
          leaf source-address {
            type inet:ip-address-no-zone;
            mandatory true;
            description
              "The source address for the notifications.";
          }
        }
      }
    }

    grouping receiver-info {
      description
        "Defines where and how to deliver notifications for a



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         configured subscription.  This includes
         specifying the receiver, as well as defining
         any network and transport aspects when sending of
         notifications occurs outside of Netconf.";
      container receivers {
        description
          "Set of receivers in a subscription.";
        list receiver {
          key "address";
          min-elements 1;
          description
            "A single host or multipoint address intended as a target
             for the notifications for a subscription.";
          leaf address {
            type inet:host;
            mandatory true;
            description
              "Specifies the address for the traffic to reach a
               remote host. One of the following must be
               specified: an ipv4 address, an ipv6 address,
               or a host name.";
          }
          leaf port {
            type inet:port-number;
            mandatory true;
            description
              "This leaf specifies the port number to use for messages
               destined for a receiver.";
          }
          leaf protocol {
            type transport-protocol;
            default "netconf";
            description
              "This leaf specifies the transport protocol used
               to deliver messages destined for the receiver.";
          }
        }
      }
    }

    grouping subscription-response {
      description
        "Defines the output to the rpc's establish-subscription
         and modify-subscription.";
      leaf subscription-result {
        type subscription-result;
        mandatory true;
        description



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          "Indicates whether subscription is operational,
           or if a problem was encountered.";
      }
      choice result {
        description
          "Depending on the subscription result, different
           data is returned.";
        case success {
          description
            "This case is used when the subscription request
             was successful and a subscription was created/modified
             as a result";
          leaf subscription-id {
            type subscription-id;
            mandatory true;
            description
              "Identifier used for this subscription.";
          }
        }
        case no-success {
          description
            "This case applies when a subscription request
             was not successful and no subscription was
             created (or modified) as a result.  In this case,
             information MAY be returned that indicates
             suggested parameter settings that would have a
             high likelihood of succeeding in a subsequent
             establish-subscription or modify-subscription
             request.";
          uses subscription-info;
        }
      }
    }

    /*
     * RPCs
     */

    rpc establish-subscription {
      description
        "This RPC allows a subscriber to create
         (and possibly negotiate) a subscription on its own behalf.
         If successful, the subscription
         remains in effect for the duration of the subscriber's
         association with the publisher, or until the subscription
         is terminated by virtue of a delete-subscription request.
         In case an error (as indicated by subscription-result)
         is returned, the subscription is



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         not created.  In that case, the RPC output
         MAY include suggested parameter settings
         that would have a high likelihood of succeeding in a
         subsequent create-subscription request.";
      input {
        uses subscription-info;
      }
      output {
        uses subscription-response;
      }
    }

    rpc modify-subscription {
      description
        "This RPC allows a subscriber to modify a subscription
         that was previously created using create-subscription.
         If successful, the subscription
         remains in effect for the duration of the subscriber's
         association with the publisher, or until the subscription
         is terminated by virtue of a delete-subscription request.
         In case an error is returned (as indicated by
         subscription-result), the subscription is
         not modified and the original subscription parameters
         remain in effect.  In that case, the rpc error response
         MAY include suggested parameter settings
         that would have a high likelihood of succeeding in a
         subsequent modify-subscription request.";
      input {
        leaf subscription-id {
          type subscription-id;
          description
            "Identifier to use for this subscription.";
        }
        uses subscription-info;
      }
      output {
        uses subscription-response;
      }
    }

    rpc delete-subscription {
      description
        "This RPC allows a subscriber to delete a subscription that
         was previously created using create-subscription.";
      input {
        leaf subscription-id {
          type subscription-id;
          mandatory true;



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          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 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



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         notification.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
      leaf reason {
        type subscription-susp-reason;
        description
          "Provides a reason for why the subscription was
           suspended.";
      }
    }

    notification subscription-resumed {
      netmod-notif:control-plane-notif;
      description
        "This notification indicates that a subscription that had
         previously been suspended has resumed. Notifications
         will once again be sent.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
    }

    notification subscription-modified {
      netmod-notif:control-plane-notif;
      description
        "This notification indicates that a subscription has
         been modified.  Notifications sent from this point
         on will conform to the modified terms of the
         subscription.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
      uses subscription-info;
    }

    notification subscription-terminated {
      netmod-notif:control-plane-notif;
      description



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        "This notification indicates that a subscription has been
         terminated.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
      leaf reason {
        type subscription-term-reason;
        description
          "Provides a reason for why the subscription was
           terminated.";
      }
    }

    notification added-to-subscription {
      netmod-notif:control-plane-notif;
      description
        "This notification is sent to a receiver when it has been
         added to an existing subscription.
         Note that if the receiver is added when the subscription
         is created, it will receive a subscription-started
         notification and no added-to-subscription.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
      uses subscription-info;
    }

    notification removed-from-subscription {
      netmod-notif:control-plane-notif;
      description
        "This notification is sent to a receiver when it has been
         removed from an existing subscription.
         Note that if the subscription is terminated, the receiver
         will receive a subscription-terminated notification
         and no removed-from-subscription.";
      leaf subscription-id {
        type subscription-id;
        mandatory true;
        description
          "This references the affected subscription.";
      }
    }



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    augment /netmod-notif:replayComplete {
      description
        "Augmenting the definition in RFC-5277 to include the
         subscription identifier defined in 5277-bis";
      leaf subscription-id {
        type subscription-id;
        description
          "This references the affected subscription.
           Not present for created subscriptions for backwards
           compatibility.";
      }
    }

    augment /netmod-notif:notificationComplete {
      description
        "Augmenting the definition in RFC-5277 to include the
         subscription identifier defined in 5277-bis";
      leaf subscription-id {
        type subscription-id;
        description
          "This references the affected subscription.
           Not present for created subscriptions for backwards
           compatibility.";
      }
    }


    /*
     * 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 {



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      description
        "This container contains a list of configurable filters
         that can be applied to subscriptions.  This facilitates
         the reuse of complex filters once defined.";
      list filter {
        key "filter-id";
        description
          "A list of configurable filters that can be applied to
           subscriptions.";
        leaf filter-id {
          type filter-id;
          description
            "An identifier to differentiate between filters.";
        }
        uses notif:base-filter;
      }
    }
    container subscription-config {
      if-feature "configured-subscriptions";
      description
        "Contains the list of subscriptions that are configured,
         as opposed to established via RPC or other means.";
      list subscription {
        key "subscription-id";
        description
          "Content of a subscription.";
        leaf subscription-id {
          type subscription-id;
          description
            "Identifier to use for this subscription.";
        }
        uses subscription-info;
        uses receiver-info {
          if-feature "configured-subscriptions";
        }
        uses push-source-info {
          if-feature "configured-subscriptions";
        }
      }
    }
    container subscriptions {
      config false;
      description
        "Contains the list of currently active subscriptions,
         i.e. subscriptions that are currently in effect,
         used for subscription management and monitoring purposes.
         This includes subscriptions that have been setup via RPC
         primitives, e.g. create-subscription, delete-subscription,



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         and modify-subscription, as well as subscriptions that
         have been established via configuration.";
      list subscription {
        key "subscription-id";
        config false;
        description
          "Content of a subscription.
           Subscriptions can be created using a control channel
           or RPC, or be established through configuration.";
        leaf subscription-id {
          type subscription-id;
          description
            "Identifier of this subscription.";
        }

        leaf configured-subscription {
         if-feature "configured-subscriptions";
         type empty;
         description
           "The presence of this leaf indicates that the
            subscription originated from configuration, not
            through a control channel or RPC.";
        }

        leaf subscription-status {
          type subscription-status;
          description
            "The status of the subscription.";
        }
        uses subscription-info;
        uses receiver-info {
          if-feature "configured-subscriptions";
        }
        uses push-source-info {
          if-feature "configured-subscriptions";
        }
      }
    }

    augment /netmod-notif:netconf/netmod-notif:streams {
      description
        "Augmenting the definition in RFC-5277 to so that streams
         can opt out the default stream.";
      leaf exclude-from-NETCONF-stream {
          type empty;
          description
            "Indicates that the stream should not be part of the
             default stream.";



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      }
    }

  }

  <CODE ENDS>

10.  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".
   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



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   [RFC5277], e.g., replayComplete; and that commonly used in yang
   models, e.g., subscription-started.

11.  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
   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.




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   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.

12.  Issues that are currently being worked and resolved

12.1.  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.

   EN5 - Along with Netconf-notif, should this draft obsolete 5277 or be
   in parallel with it?

   EN6 - Stream discovery.  Are adjustments needed for maximal transport
   independence?

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

   EN8 - Should we have a mandatory transport?

12.2.  Agreement in principal

   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.

12.3.  Resolved Issues

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

12.4.  Editorial To-Dos

   Update examples.  Examples are not in synch with the current model.

   Remove overlap with transport specifics, specifically NETCONF.  The
   current draft revision is "self-contained" and assumes NETCONF as a
   transport.  It does not yet reflect the breakout of transport
   mappings into a separate draft.

13.  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.

14.  References

14.1.  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>.

14.2.  Informative References

   [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-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

   Alberto Gonzalez Prieto
   Cisco Systems

   Email: albertgo@cisco.com


   Alexander Clemm
   Cisco Systems

   Email: alex@cisco.com


   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com


   Einar Nilsen-Nygaard
   Cisco Systems

   Email: einarnn@cisco.com




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   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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