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Versions: 00 01 02 03 04 05 06

NETMOD Working Group                                             M. Wang
Internet-Draft                                                     Q. Wu
Intended status: Standards Track                                  Huawei
Expires: May 3, 2020                                              C. Xie
                                                           China Telecom
                                                              I. Bryskin
                                                              Individual
                                                                  X. Liu
                                                          Volta Networks
                                                                A. Clemm
                                                               Futurewei
                                                             H. Birkholz
                                                          Fraunhofer SIT
                                                                 T. Zhou
                                                                  Huawei
                                                        October 31, 2019


              A YANG Data model for ECA Policy Management
                     draft-wwx-netmod-event-yang-04

Abstract

   RFC8328 defines a policy-based management framework that allow
   definition of a data model to be used to represent high-level,
   possibly network-wide policies.  Policy discussed in RFC8328 are
   classified into imperative policy and declarative policy, ECA policy
   is an typical example of imperative policy.  This document defines an
   YANG data model for the ECA policy management.  The ECA policy YANG
   provides the ability for the network management function (within a
   controller, an orchestrator, or a network element) to control the
   configuration and monitor state change on the network element and
   take simple and instant action when a trigger condition on the system
   state is met.

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 https://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




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   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 May 3, 2020.

Copyright Notice

   Copyright (c) 2019 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   4
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Relationship to YANG Push . . . . . . . . . . . . . . . . . .   5
   5.  Model Overview  . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  EVENT TRIGGER YANG Module . . . . . . . . . . . . . . . . . .  12
   7.  EVENT YANG Module . . . . . . . . . . . . . . . . . . . . . .  17
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  23
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  24
   10. Acknowledges  . . . . . . . . . . . . . . . . . . . . . . . .  24
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  25
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  25
   Appendix A.  Usage Example of ECA model Working with YANG PUSH  .  26
   Appendix B.  Usage Example of Reusing Trigger-Grouping  . . . . .  29
   Appendix C.  Changes between Revisions  . . . . . . . . . . . . .  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Introduction

   Network management consists of using one or multiple device-,
   technology-, service specific policies to influence management
   behavior within the system and make sure policies are enforced or
   executed correctly.




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   [RFC8328] defines a policy-based management framework that allow
   definition of a data model to be used to represent high-level,
   possibly network-wide policies.  Policies discussed in [RFC8328] are
   classified into imperative policy and declarative policy.
   Declarative policy specifies the goals to be achieved but not how to
   achieve those goals while imperative policy specifies when Events are
   triggered and what actions must be performed on the occurrence of an
   event.  ECA policy is a typical example of imperative policy.

   Event-driven management of states of managed objects across a wide
   range of devices can be used to monitor state changes of managed
   objects or resource and automatic trigger of rules in response to
   events so as to better service assurance for customers and to provide
   rapid autonomic response that can exhibit self-management properties
   including self-configuration, self-healing, self-optimization, and
   self-protection.  Following are some of the use-cases where such ECA
   Policy can be used:

   o  To filter out of objects underneath a requested a subtree, the
      subscriber may use YANG Push smart filter to request the network
      server to monitor specific network management data objects and
      send updates only when the value falls within a certain range.

   o  To filter out of objects underneath a requested a subtree, the
      subscriber may use YANG Push smart filter to request the network
      server to monitor specific network management data objects and
      send updates only when the value exceeds a certain threshold for
      the first time but not again until the threshold is cleared.

   o  To provide rapid autonomic response that can exhibit self-
      management properties, the management system delegate event
      response behaviors (e.g., auto-recover from network failure) to
      the network device so that the network can react to network change
      as quickly as the event is detected.  The event response behaviors
      delegation can be done using ECA policy,e.g., to preconfigure
      protection/ restoration capability on the network device.

   o  To perform troubleshoot failures (i.e., fault verification and
      localization) and provide root cause analysis, the management
      system monitoring specific network management data objects may
      request the network device to export state information of a set of
      managed data objects when the value of monitored data object
      exceeds a certain threshold.

   This document defines a ECA Policy management YANG data model.  The
   ECA Policy YANG provides the ability for the network management
   function (within a controller, an orchestrator, or a network element)
   to control the configurations and monitor state parameters on the



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   network element and take simple and instant action when a trigger
   condition on the system state is met.

   The data model in this document is designed to be compliant with the
   Network Management Datastore Architecture (NMDA) [RFC8342].

2.  Conventions used in this document

2.1.  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 [RFC2119].  In this
   document, these words will appear with that interpretation only when
   in ALL CAPS.  Lower case uses of these words are not to be
   interpreted as carrying [RFC2119] significance.

   This document uses the following terms:

   Error  A deviation of a system from normal operation [RFC3877].

   Fault  Lasting error or warning condition [RFC3877].

   Event  Something that happens which may be of interest or trigger the
      invocation of the rule.  A fault, an alarm, a change in network
      state, network security threat, hardware malfunction, buffer
      untilization crossing a threshold, network connection setup, an
      external input to the system, for example [RFC3877].

2.2.  Tree Diagrams

   Tree diagrams used in this document follow the notation defined in
   [RFC8340].

3.  Objectives

   This section describes some of the design objectives for the ECA
   Policy management Data Model:

   o  Clear and precise identification of Event types in the ECA Policy.

   o  Clear and precise identification of managed object in the ECA
      Policy.

   o  Allow nested ECA policy,e.g, one event to be able to call another
      nested event.





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   o  Allow the NETCONF server send updates only when the value falls
      within a certain range.

   o  Allow the NETCONF server send updates only when the value exceeds
      a certain threshold for the first time but not again until the
      threshold is cleared.

   o  Provide rapid autonomic response in the network device that can
      exhibit self-management properties including self-configuration,
      self-healing, self-optimization, and self-protection.

4.  Relationship to YANG Push

   YANG-push mechanism provides a subscription service for updates from
   a datastore.  And it supports two types of subscriptions which are
   distinguished by how updates are triggered: periodic and on-change.

   The On-change Push allow receivers to receive updates whenever
   changes to target managed objects occur.  This document specifies a
   mechanism that provides three trigger conditions:

   o  Existence: When a specific managed object appears,disappear or
      object change, the trigger fires, e.g. reserved ports are
      configured.

   o  Boolean: The user can set the type of boolean operator (e.g.
      unequal, equal, less, less-or-equal, greater, greater-or-equal,
      etc) and preconfigured threshold value (e.g.  Pre-configured
      threshold).  If the value of a managed object meet Boolean
      conditions, the trigger fires, e.g., when the boolean operator
      type is 'less', the trigger will be fired if the value of managed
      object is less than the pre-configured Boolean value.

   o  Threshold: The user can set the rising threshold,the falling
      threshold, the delta rising threshold, the delta falling
      threshold.  A threshold test regularly compares the value of the
      monitored object with the threshold values, e.g., an event is
      triggered if the value of the monitored object is greater than or
      equal to the rising threshold or an event is triggered if the
      difference between the current measurement value and the previous
      measurement value is smaller than or equal to the delta falling
      threshold.

   In these three trigger conditions, existence with type set to object
   change is similar to on Push change.

   In addtion, the model defined in this document provides a method for
   closed loop network management automation which allows automatic



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   trigger of rules in response to events so as to better service
   assurance for customers and to provide rapid autonomic response that
   can exhibit self-management properties including self-configuration,
   self-healing, self-optimization, and self-protection.  The details of
   the usage example is described in Appendix A.

5.  Model Overview

   The YANG data model for the ECA Policy management has been split into
   two modules:

   o  The ietf-event-trigger.yang module defines a set of groupings for
      a generic trigger.  It is intended that these groupings will be
      used by the policy based event management model or other models
      that require the trigger conditions.  In this model, three trigger
      conditions are defined under the "test" choice node:

      *  Existence: An existence test monitors and manages the absence,
         presence, and change of a data object, for example, interface
         status.  When a monitored object is specified, the system reads
         the value of the monitored object regularly.

         +  If the test type is Absent, the system triggers a network
            event and takes the specified action when the monitored
            object disappears.

         +  If the test type is Present, the system triggers a network
            event and takes the specified action when the monitored
            object appears.

         +  If the test type is Changed, the system triggers a network
            event and takes the specified action when the value of the
            monitored object changes.

      *  Boolean: A Boolean test compares the value of the monitored
         object with the reference value and takes action according to
         the comparison result.  The comparison types include unequal,
         equal, less, lessorequal, greater, and greaterorequal.  For
         example, if the comparison type is equal, an event is triggered
         when the value of the monitored object equals the reference
         value.  The event will not be triggered again until the value
         becomes unequal and comes back to equal.

      *  Threshold: A Threshold trigger condition regularly compares
         compares the value of the monitored object with the threshold
         values.





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         +  A rising network event is triggered if the value of the
            monitored object is greater than or equal to the rising
            threshold.

         +  A falling network event is triggered if the value of the
            monitored object is smaller than or equal to the falling
            threshold.

         +  A rising network event is triggered if the difference
            between the current measurement value and the previous
            measurement value is greater than or equal to the delta
            rising threshold.

         +  A falling network event is triggered if the difference
            between the current measurement value and the previous
            measurement value is smaller than or equal to the delta
            falling threshold.

         +  A falling network event is triggered if the values of the
            monitored object, the rising threshold, and the falling
            threshold are the same.

         +  A falling network event is triggered if the delta rising
            threshold, the delta falling threshold, and the difference
            between the current sampled value and the previous sampled
            value is the same.

         If the value of the monitored object crosses a threshold
         multiple times in succession, the managed device triggers a
         network event only for the first crossing.

      Editor-note: Three trigger conditions defined this document align
      with Complex condition and Simple condition defined in RFC3460?
      Are they sufficient to model ECA condition?

   o  The ietf-event.yang module defines four lists: trigger, target,
      event, and action.  Triggers define the targets meeting some
      conditions that lead to events.  Events trigger corresponding
      actions:

      *  Each trigger can be seen as a logical test that, if satisfied
         or evaluated to be true, cause the action to be carried out.
         The ietf-event.yang module uses groupings defined in ietf-
         event-trigger.yang to present the trigger attributes.

      *  The target list defines managed objects that can be added to
         logging or be set to a new value on the trigger, the trigger
         test type, or the event that resulted in the actions.  The



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         target is also refered to as policy variable defined in
         [RFC3460].

      *  The event list defines what happens when an event is triggered,
         i.e., trigger the corresponding action, e.g., addding a logging
         ( i.e. Recording the triggered event), setting a value to the
         managed object or both.  The group-id can be used to group a
         set of event that can be executed together,e.g., deliver a
         service or provide service assurance.

      *  Nested-event are supported by allowing one event's trigger to
         reference other event's definitions using the call-event
         configuration.  Called events apply their triggers and actions
         before returning to the calling event's trigger and resuming
         evaluation.  If the called event is triggered, then it returns
         an effective boolean true value to the calling event.  For the
         calling event, this is equivalent to a condition statement
         evaluating to a true value and evaluation of the event
         continues.

      *  The action list consists of updates or invocations on local
         managed object attributes and defines a set of actions which
         will be performed (e.g. logging, set value, etc) when the
         corresponding event is triggered.  The value to be set can use
         many variations on rule structure.

   The following tree diagrams [RFC8340] provide an overview of the data
   model for "ietf-event-trigger" module and the "ietf-event" module.

   module: ietf-event-trigger
     grouping existences-trigger
       +-- existences
          +-- test-type?   enumeration
          +-- target*      target
     grouping boolean-trigger
       +-- boolean
          +-- operator?   operator
          +-- value?      match-value
          +-- target*     target
     grouping threshold-trigger
       +-- threshold
          +-- rising-value?           match-value
          +-- rising-target*          target
          +-- falling-value?          match-value
          +-- falling-target*         target
          +-- delta-rising-value?     match-value
          +-- delta-rising-target*    target
          +-- delta-falling-value?    match-value



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          +-- delta-falling-target*   target
          +-- startup?                enumeration
     grouping trigger-grouping
       +-- (test)?
          +--:(existences)
          |  +-- existences
          |     +-- test-type?   enumeration
          |     +-- target*      target
          +--:(boolean)
          |  +-- boolean
          |     +-- operator?   operator
          |     +-- value?      match-value
          |     +-- target*     target
          +--:(threshold)
             +-- threshold
                +-- rising-value?           match-value
                +-- rising-target*          target
                +-- falling-value?          match-value
                +-- falling-target*         target
                +-- delta-rising-value?     match-value
                +-- delta-rising-target*    target
                +-- delta-falling-value?    match-value
                +-- delta-falling-target*   target
                +-- startup?                enumeration

   module: ietf-event
     +--rw events
        +--rw event* [event-name type]
           +--rw event-name           string
           +--rw type                 identityref
           +--rw event-description?   string
           +--rw group-id?            group-type
           +--rw target*              trig:target
           +--rw clear?               boolean
           +--rw trigger* [name]
           |  +--rw name                   string
           |  +--rw trigger-description?   string
           |  +--rw call-event?            -> ../../event-name
           |  +--rw frequency
           |  |  +--rw type?         identityref
           |  |  +--rw periodic
           |  |  |  +--rw interval    uint32
           |  |  |  +--rw start?      yang:date-and-time
           |  |  |  +--rw end?        yang:date-and-time
           |  |  +--rw scheduling
           |  |     +--rw month*          string
           |  |     +--rw day-of-month*   uint8
           |  |     +--rw day-of-week*    uint8



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           |  |     +--rw hour*           uint8
           |  |     +--rw minute*         uint8
           |  |     +--rw second*         uint8
           |  |     +--rw start?          yang:date-and-time
           |  |     +--rw end?            yang:date-and-time
           |  +--rw (test)?
           |     +--:(existences)
           |     |  +--rw existences
           |     |     +--rw target*   target
           |     +--:(boolean)
           |     |  +--rw boolean
           |     |     +--rw operator?   operator
           |     |     +--rw value?      match-value
           |     |     +--rw target*     target
           |     +--:(threshold)
           |        +--rw threshold
           |           +--rw rising-value?           match-value
           |           +--rw rising-target*          target
           |           +--rw falling-value?          match-value
           |           +--rw falling-target*         target
           |           +--rw delta-rising-value?     match-value
           |           +--rw delta-rising-target*    target
           |           +--rw delta-falling-value?    match-value
           |           +--rw delta-falling-target*   target
           |           +--rw startup?                enumeration
           +--rw actions
              +--rw action* [name]
                 +--rw name       string
                 +--rw set
                 |  +--rw target?   trig:target
                 |  +--rw value?    <anydata>
                 +--rw logging
                    +--rw type?   logging-type

   The relation between Event, Trigger, Target and Action is described
   as follows:















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    Project
   +-------------------------------+
   | Event                         |
   |  +-------+                    |
   |  |Target |                    |
   |  +---|---+                    |   +-------------------------------+
   |      |                        |   | Event                         |
   | +----V---+        +--------+  |   |  +-------+                    |
   | |Trigger |------->| Action |-------->|Target |                    |
   | +--------+        +--------+  |   |  +---|---+                    |
   +-------------------------------+   |      |                        |
                                       | +----|---+        +--------+  |
                                       | |Trigger |------- | Action |  |
                                       | +--------+        +----+---+  |
                                       +------------------------+------+
                                                                |
                                              +-----------------+
                                       +------+------------------------+
                                       | Event|                        |
                                       |  +---V---+                    |
                                       |  |Target |                    |
                                       |  +---|---+                    |
                                       |      |                        |
                                       | +----|---+        +--------+  |
                                       | |Trigger |------- | Action |  |
                                       | +--------+        +---+----+  |
                                       +-----------------------+-------+
                                              +----------------+
                                       +------+------------------------+
                                       | Event|                        |
                                       |  +---V---+                    |
                                       |  |Target |                    |
                                       |  +---|---+                    |
                                       |      |                        |
                                       | +----|---+        +--------+  |
                                       | |Trigger |------- | Action |  |
                                       | +--------+        +--------+  |
                                       +-------------------------------+


   One event may trigger another event,i.e., the action output in the
   first event can be input to target in the second event and a set of
   events can be grouped together and executed in a coordinated manner,
   but if it does not trigger another event, the relation between two
   events should be ignored.






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6.  EVENT TRIGGER YANG Module

<CODE BEGINS> file "ietf-event-trigger@2019-10-28.yang"
module ietf-event-trigger {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-event-trigger";
  prefix trig;

  import ietf-yang-types {
    prefix yang;
  }
  organization
    "IETF xxx Working Group";
  contact
    "Zitao Wang: wangzitao@huawei.com
     Qin Wu: bill.wu@huawei.com";
  description
    "This module defines a reusable grouping for event trigger.";

  revision 2019-10-28 {
    description
      "Initial revision.";
    reference
      "foo";
  }

  typedef match-value {
    type union {
      type yang:xpath1.0;
      type yang:object-identifier;
      type string;
    }
    description
      "This type is used to match resources of type 'target'.
       Since the type 'target' is a union of different types,
       the 'match-value' type is also a union of corresponding
       types.";
  }

  typedef target {
    type union {
      type instance-identifier;
      type yang:object-identifier;
      type yang:uuid;
      type string;
    }
    description
      "If the target is modelled in YANG, this type will



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       be an instance-identifier.
       If the target is an SNMP object, the type will be an
       object-identifier.
       If the target is anything else, for example a distinguished
       name or a CIM path, this type will be a string.
       If the target is identified by a UUID use the uuid
       type.
       If the server supports several models, the presedence should
       be in the order as given in the union definition.";
  }

  typedef operator {
    type enumeration {
      enum unequal {
        description
          "Indicates that the comparision type is unequal to.";
      }
      enum equal {
        description
          "Indicates that the comparision type is equal to.";
      }
      enum less {
        description
          "Indicates that the comparision type is less than.";
      }
      enum less-or-equal {
        description
          "Indicates that the comparision type is less than
           or equal to.";
      }
      enum greater {
        description
          "Indicates that the comparision type is greater than.";
      }
      enum greater-or-equal {
        description
          "Indicates that the comparision type is greater than
           or equal to.";
      }
    }
    description
      "definition of the operator";
  }

  grouping existences-trigger {
    description
      "A grouping that provides existence trigger";
    container existences {



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      leaf test-type {
        type enumeration {
          enum absent {
            description
              "If the test type is Absent, the system triggers an event
               and takes the specified action when the monitored object disappears.";
          }
          enum present {
            description
              "If the test type is Present, the system triggers an event
               and takes the specified action when the monitored object appears.";
          }
          enum changed {
            description
              "If the test type is Changed, the system triggers an alarm event and takes
               the specified action when the value of the monitored object changes.";
          }
        }
       description "test type.";
      }
      leaf-list target {
        type target;
        description
          "List for target objects";
      }
      description
        "Container for existence";
    }
  }

  grouping boolean-trigger {
    description
      "A grouping that provides boolean trigger";
    container boolean {
      leaf operator {
        type operator;
        description
          "Comparison type.";
      }
      leaf value {
        type match-value;
        description
          "Compartion value which is static threshold value.";
      }
      leaf-list target {
        type target;
        description
          "List for target management objects.";



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      }
      description
        "Container for boolean test.";
    }
  }

  grouping threshold-trigger {
    description
      "A grouping that provides threshold trigger";
    container threshold {
      leaf rising-value {
        type match-value;
        description
          "Sets the rising threshold to the specified value,
           when the current sampled value is greater than or equal to
           this threshold, and the value at the last sampling interval
           was less than this threshold, the event is triggered. ";
      }
      leaf-list rising-target {
        type target;
        description
          "List for target objects.";
      }
      leaf falling-value {
        type match-value;
        description
          "Sets the falling threshold to the specified value.";
      }
      leaf-list falling-target {
        type target;
        description
          "List for target objects.";
      }
      leaf delta-rising-value {
        type match-value;
        description
          "Sets the delta rising threshold to the specified value.";
      }
      leaf-list delta-rising-target {
        type target;
        description
          "List for target objects.";
      }
      leaf delta-falling-value {
        type match-value;
        description
          "Sets the delta falling threshold to the specified value.";
      }



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      leaf-list delta-falling-target {
        type target;
        description
          "List for target objects.";
      }
      leaf startup {
        type enumeration {
          enum rising {
            description
              "If the first sample after this
               managed object becomes active is greater than or equal
                to 'rising-value' and the 'startup' is equal to
                'rising' then one threshold rising event is
               triggered for that managed object.";
          }
          enum falling {
            description
              "If the first sample after this managed object becomes
               active is less than or equal to 'falling-value' and
               the 'startup' is equal to 'falling' then one
               threshold falling event is triggered for that managed
               object.";
          }
          enum rising-or-falling {
            description
              "That event may be triggered when the
               'startup' is equal to 'rising-or-falling'.
               'rising-or-falling' indicate the state value of the
                managed object may less than or greater than the
               specified thrshold value.";
          }
        }
        description
          "Startup setting.";
      }
      description
        "Container for the threshold trigger condition.
         Note that the threshold here  may change over time
         or the state value changes in either ascend order
         or descend order.";
    }
  }

  grouping trigger-grouping {
    description
      "A grouping that provides event trigger.";
    choice test {
      description



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        "Choice test";
      case existences {
        uses existences-trigger;
      }
      case boolean {
        uses boolean-trigger;
      }
      case threshold {
        uses threshold-trigger;
      }
    }
  }
}
<CODE ENDS>

7.  EVENT YANG Module

   <CODE BEGINS> file "ietf-event@2019-10-28.yang"

   module ietf-event {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-event";
     prefix evt;

     import ietf-yang-types {
       prefix yang;
     }
     import ietf-event-trigger {
       prefix trig;
     }

     organization
       "IETF xxx Working Group";
     contact
       "Zitao Wang: wangzitao@huawei.com
        Qin Wu: bill.wu@huawei.com";
     description
       "This module defines a model for the service topology.";

     revision 2019-10-28 {
       description
         "Initial revision.";
       reference
         "foo";
     }

     identity event-type {
       description



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         "Base identity for event type";
     }

     identity frequency {
       description
         "Base identity for frequency";
     }

     identity periodic {
       base frequency;
       description
         "Identity for periodic trigger";
     }

     identity scheduling {
       base frequency;
       description
         "Identity for scheduling trigger";
     }

     identity logging {
       description
         "Base identity for logging action";
     }

     identity logging-notification {
       base logging;
       description
         "Logging for event notification";
     }

     identity logging-set {
       base logging;
       description
         "Logging for reset values";
     }

     typedef logging-type {
       type identityref {
         base logging;
       }
       description
         "Logging types";
     }

     typedef group-type {
       type string;
       description



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         "Group type";
     }

     grouping start-end-grouping {
       description
         "A grouping that provides start and end times for
          Event objects.";
       leaf start {
         type yang:date-and-time;
         description
           "The date and time when the Event object
            starts to create triggers.";
       }
       leaf end {
         type yang:date-and-time;
         description
           "The date and time when the Event object
            stops to create triggers.
            It is generally a good idea to always configure
            an end time and to refresh the end time as needed
            to ensure that agents that lose connectivity to
            their Controller do not continue executing Schedules
            forever.";
       }
     }

     container events {
       list event {
         key "event-name type";
         leaf event-name {
           type string;
           description
             "Event name";
         }
         leaf type {
           type identityref {
             base event-type;
           }
           description
             "Type of event";
         }
         leaf event-description {
           type string;
           description
             "Event description";
         }
         leaf group-id {
           type group-type;



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           description
             "Group Identifier";
         }
         leaf-list target {
           type trig:target;
           description
             "targeted objects";
         }
         leaf clear {
           type boolean;
           default "false";
           description
             "A flag indicate whether the event be closed";
         }
         list trigger {
           key "name";
           leaf name {
             type string;
             description
               "Trigger name";
           }
           leaf trigger-description {
             type string;
             description
               "Trigger description";
           }
           leaf call-event {
             type leafref {
               path "../../event-name";
             }
             description
               "This leaf call sub-event.";
           }
           container frequency {
             leaf type {
               type identityref {
                 base frequency;
               }
               description
                 "Type of trigger frequency";
             }
             container periodic {
               when "derived-from-or-self(../type, 'periodic')";
               description
                 "A periodic timing object triggers periodically
                  according to a regular interval.";
               leaf interval {
                 type uint32 {



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                   range "1..max";
                 }
                 units "seconds";
                 mandatory true;
                 description
                   "The number of seconds between two triggers
                    generated by this periodic timing object.";
               }
               uses start-end-grouping;
             }
             container scheduling {
               when "derived-from-or-self(../type, 'scheduling')";
               description
                 "A scheduling timing object triggers.";
               leaf-list month {
                 type string;
                 description
                   "A set of months at which this scheduling timing
                    will trigger.";
               }
               leaf-list day-of-month {
                 type uint8 {
                   range "0..59";
                 }
                 description
                   "A set of days of the month at which this
                    scheduling timing will trigger.";
               }
               leaf-list day-of-week {
                 type uint8 {
                   range "0..59";
                 }
                 description
                   "A set of weekdays at which this scheduling timing
                    will trigger.";
               }
               leaf-list hour {
                 type uint8 {
                   range "0..59";
                 }
                 description
                   "A set of hours at which the scheduling timing will
                    trigger.";
               }
               leaf-list minute {
                 type uint8 {
                   range "0..59";
                 }



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                 description
                   "A set of minutes at which this scheduling timing
                    will trigger.";
               }
               leaf-list second {
                 type uint8 {
                   range "0..59";
                 }
                 description
                   "A set of seconds at which this calendar timing
                    will trigger.";
               }
               uses start-end-grouping;
             }
             description
               "Container for frequency";
           }
           uses trig:trigger-grouping;
           description
             "List for trigger";
         }
         container actions {
           list action {
             key "name";
             leaf name {
               type string;
               description
                 "Action Name";
             }
             container set {
               leaf target {
                 type trig:target;
                 description
                   "The target objects";
               }
               anydata value {
                 description
                   "Inline set content.";
               }
               description
                 "Set a value to the target";
             }
             container logging {
               leaf type {
                 type logging-type;
                 description
                   "Specifies the log action";
               }



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               description
                 "Specifies the log action";
             }
             description
               "List for actions";
           }
           description
             "Container for Actions";
         }
         description
           "List for Events";
       }
       description
         "YANG data module for defining event triggers and actions for
          network management purposes";
     }
   }

   <CODE ENDS>

8.  Security Considerations

   The YANG modules defined in this document MAY be accessed via the
   RESTCONF protocol [RFC8040] or NETCONF protocol ([RFC6241]).  The
   lowest RESTCONF or NETCONF layer requires that the transport-layer
   protocol provides both data integrity and confidentiality, see
   Section 2 in [RFC8040] and [RFC6241].  The lowest NETCONF layer is
   the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH)[RFC6242] . The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC5246].

   The NETCONF access control model [RFC6536] provides the means to
   restrict access for particular NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   o  /events/event/event-name

   o  /events/event/target



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   o  /events/actions/target

   o  /events/event/trigger/name

9.  IANA Considerations

   This document registers two URIs in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registrations are
   requested to be made:

   ---------------------------------------------------------------------
      URI: urn:ietf:params:xml:ns:yang:ietf-event-trigger
      Registrant Contact: The IESG.
      XML: N/A, the requested URI is an XML namespace.

      URI: urn:ietf:params:xml:ns:yang:ietf-event
      Registrant Contact: The IESG.
      XML: N/A, the requested URI is an XML namespace.
   ---------------------------------------------------------------------

   This document registers two YANG modules in the YANG Module Names
   registry [RFC6020].

   ---------------------------------------------------------------------
      Name:         ietf-event-trigger
      Namespace:    urn:ietf:params:xml:ns:yang:ietf-event-trigger
      Prefix:       trig
      Reference:    RFC xxxx

      Name:         ietf-event
      Namespace:    urn:ietf:params:xml:ns:yang:ietf-event
      Prefix:       evt
      Reference:    RFC xxxx
   ---------------------------------------------------------------------

10.  Acknowledges

   This work has benefited from the discussions of ECA Policy over the
   years.  In particular, the SUPA project [
   https://datatracker.ietf.org/wg/supa/about/ ] provided approaches to
   express high-level, possibly network-wide policies to a network
   management function (within a controller, an orchestrator, or a
   network element).

   Igor Bryskin, Xufeng Liu, Alexander Clemm, Henk Birkholz, Tianran
   Zhou contributed to an earlier version of [GNCA].  We would like to
   thank the authors of that document on event response behaviors




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   delegation for material that assisted in thinking that helped improve
   this document.

11.  Contributors

      Nicola Sambo
      Scuola Superiore Sant'Anna
      Via Moruzzi 1
      Pisa  56124
      Italy

      Email: nicola.sambo@sssup.it

      Giuseppe Fioccola
      Huawei Technologies
      Riesstrasse, 25
      Munich  80992
      Germany

      Email: giuseppe.fioccola@huawei.com

12.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", March 1997.

   [RFC2981]  Kavasseri, R., Ed., "Event MIB", RFC 2981,
              DOI 10.17487/RFC2981, October 2000,
              <https://www.rfc-editor.org/info/rfc2981>.

   [RFC3460]  Moore, B., Ed., "Policy Core Information Model (PCIM)
              Extensions", RFC 3460, DOI 10.17487/RFC3460, January 2003,
              <https://www.rfc-editor.org/info/rfc3460>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

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

   [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,
              <https://www.rfc-editor.org/info/rfc6241>.




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   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
              Profile (MPLS-TP) Identifiers", RFC 6370,
              DOI 10.17487/RFC6370, September 2011,
              <https://www.rfc-editor.org/info/rfc6370>.

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

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC7952]  Lhotka, L., "Defining and Using Metadata with YANG",
              RFC 7952, DOI 10.17487/RFC7952, August 2016,
              <https://www.rfc-editor.org/info/rfc7952>.

   [RFC8328]  Liu, W., Xie, C., Strassner, J., Karagiannis, G., Klyus,
              M., Bi, J., Cheng, Y., and D. Zhang, "Policy-Based
              Management Framework for the Simplified Use of Policy
              Abstractions (SUPA)", RFC 8328, DOI 10.17487/RFC8328,
              March 2018, <https://www.rfc-editor.org/info/rfc8328>.

Appendix A.  Usage Example of ECA model Working with YANG PUSH

   The relation between Event and YANG PUSH is described as follow: YANG
   Push Notification may trigger one event, i.e. one trigger conditions
   of the Event A can be set to "receiver received a yang push
   notification", and it can associates with other conditions of the
   Event A.  When these conditions are met, the event A is triggered.
















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     +-----------------------+
     | yang-push             |
     |                       |
     |   +--------------+    |
     |   | receiver     |    |     +------------------------------+
     |   |              |    |     |  Event A                     |
     |   +--------^-----+    |     |                              |
     |            |          |     |     +-----------+            |
     |            | +-------+|     |     |           |            |
     |            | |notification  |     |    target |            |
     |            | |       +|     |   -->           |            |
     |            | +-------+\\    ----  +----+------+            |
     |   +--------+-----+    | \---|          |                   |
     |   | target       |  ---- \\ |          |                   |
     |   |              +--  |    \\          |                   |
     |   +--------------+    |     |\  +------V---+   +----------+|
     +-----------------------+     | \\|          |   |          ||
                                   |   >  trigger +--->  action  ||
                                   |   |          |   |          ||
                                   |   +----------+   +-----+----+|
                                   |                              |
                                   +------------------------ -----+

   For Example:

   The receiver received a push-change-update notification and learned
   that the "oper-status" of interface[name='eth0'] changed.

   The target of Event "interface-state-monitoring" is set to
   "/if:interfaces/if:interface[if:name='eth0']", the trigger list
   contains two conditions: 1)receiver received a push-change-update
   notification; 2) the value of "in-errors" of interface[name='eth0']
   exceeded the pre-configured threshold.  When these conditions are
   met, corresponding action will be performed, i.e. disable
   interface[name='eth0'].  The XML examples are shown as below:



  <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
   <eventTime>2017-10-25T08:22:33.44Z</eventTime>
   <push-change-update
        xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
     <id>89</id>
     <datastore-changes>
       <yang-patch>
         <patch-id>0</patch-id>
         <edit>
           <edit-id>edit1</edit-id>



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           <operation>replace</operation>
           <target>/ietf-interfaces:interfaces</target>
           <value>
             <interfaces
                  xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
               <interface>
                 <name>eth0</name>
                 <oper-status>up</oper-status>
               </interface>
             </interfaces>
           </value>
         </edit>
       </yang-patch>
     </datastore-changes>
   </push-change-update>
  </notification>

    <event>
     <event-name>interface-state-monitoring</event-name>
     <type>interface-exception</type>
     <target>/if:interfaces/if:interface[if:name='eth0']</target>
     <trigger>
      <name>state-push-change</name>
      <trigger-description>received yang push
\changed notification</trigger-description>
      <test>
       <existence>/yp:notification/yp:push-change-update/yp:id[id=89]\
/yp:datastore-changes/.../yp:target="/ietf-interfaces:interfaces='eth0'\
"</existence>
      </test>
     </trigger>
     <trigger>
      <name>evaluate-in-errors</name>
      <call-event>interface-state-chang</call-event>
      <trigger-description>evaluate the number of
       the packets that contained errors
       </trigger-description>
      <frequency>10m</frequency>
      <test>
       <boolean>
        <operator>greater-or-equal</operator>
        <value>100</value>
        <target>/if:interfaces/if:interface[if:name='eth0']\
/if:statistic/if:in-errors</target>
       </boolean>
      </test>
     </trigger>
     <action>



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       <target>/if:interfaces/if:interface[if:name='eth0']</target>
       <value>
        <interfaces>
         <interface>
          <name>eth0</name>
          <enable>false</enable>
         </interface>
        </interfaces>
       </value>
     </action>
    </event>
   </events>

Appendix B.  Usage Example of Reusing Trigger-Grouping

   The "ietf-event-trigger.yang" module defines a set of groupings for a
   generic trigger.  It is intended that these groupings can be reused
   by other models that require the trigger conditions, for example, in
   some subscription and notification cases, many applications do not
   require every update, only updates that are of certain interest.  The
   following example describe how to reuse the "ietf-event-trigger"
   module to define the subscription and notification smarter filter.

       import ietf-subscribed-notifications {
        prefix sn;
      }
     import ietf-event-trigger {
      prefix trig;
     }

     augment "/sn:subscriptions/sn:subscription" {
       description "add the smart filter container";
       container smart-filter {
          description "It concludes filter configurations";
          uses trig:trigger-grouping;
       }
     }

   The tree diagrams:












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     module: ietf-smart-filter
     augment /sn:subscriptions/sn:subscription:
       +--rw smart-filter
          +--rw (test)?
             +--:(existences)
             |  +--rw existences
             |     +--rw target*   target
             +--:(boolean)
             |  +--rw boolean
             |     +--rw operator?   operator
             |     +--rw value?      match-value
             |     +--rw target*     target
             +--:(variation)
                +--rw variation
                   +--rw rising-value?           match-value
                   +--rw rising-target*          target
                   +--rw falling-value?          match-value
                   +--rw falling-target*         target
                   +--rw delta-rising-value?     match-value
                   +--rw delta-rising-target*    target
                   +--rw delta-falling-value?    match-value
                   +--rw delta-falling-target*   target
                   +--rw startup?                enumeration

Appendix C.  Changes between Revisions

   v03 - v04

   o  Add text in introduction section to clarify the usage examples of
      ECA policy

   o  Update objective section to align with use cases.

   o  Clarify the relationship between target and policy variable.

   o  Change variation trigger condition back into threshold trigger
      condition and clarify the usage of three trigger conditions.

   o  Remove Event MIB related section.

   o  Add new coauthors.

   v02 - v03

   o  Usage Example Update: add an usage example to introduce how to
      reuse the ietf-event-trigger module to define the subscription-
      notification smarter filter.




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   v01 - v02

   o  Introduce the group-id which allow group a set of events that can
      be executed together

   o  Change threshold trigger condition into variation trigger
      condition to further clarify the difference between boolean
      trigger condition and variation trigger condition.

   o  Module structure optimization.

   o  Usage Example Update.

   v00 - v01

   o  Separate ietf-event-trigger.yang from Event management modeland
      ietf-event.yang and make it reusable in other YANG models.

   o  Clarify the difference between boolean trigger condition and
      threshold trigger condition.

   o  Change evt-smp-min and evt-smp-max into min-data-object and max-
      data-object in the data model.

Authors' Addresses

   Michael Wang
   Huawei Technologies,Co.,Ltd
   101 Software Avenue, Yuhua District
   Nanjing  210012
   China

   Email: wangzitao@huawei.com


   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: bill.wu@huawei.com


   Chongfeng Xie
   China Telecom

   Email: xiechf@ctbri.com.cn



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   Igor Bryskin
   Individual

   Email: i_bryskin@yahoo.com


   Xufeng Liu
   Volta Networks

   Email: xufeng.liu.ietf@gmail.com


   Alexander Clemm
   Futurewei

   Email: ludwig@clemm.org


   Henk Birkholz
   Fraunhofer SIT

   Email: henk.birkholz@sit.fraunhofer.de


   Tianran Zhou
   Huawei

   Email: zhoutianran@huawei.com























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