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

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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/.

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This Internet-Draft will expire on May 4, 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. Conventions used in this document
• 2.1. Terminology
• 2.2. Tree Diagrams
• 3. Objectives
• 4. Relationship to YANG Push
• 5. Model Overview
• 6. EVENT TRIGGER YANG Module
• 7. EVENT YANG Module
• 8. Security Considerations
• 9. IANA Considerations
• 10. Acknowledges
• 11. Contributors
• 12. Normative References
• Appendix A. Usage Example of ECA model Working with YANG PUSH
• Appendix B. Usage Example of Reusing Trigger-Grouping
• Appendix C. Changes between Revisions
• Authors' Addresses

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.

[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:

• 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.
• 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.
• 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.
• 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 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:

• Clear and precise identification of Event types in the ECA Policy.
• Clear and precise identification of managed object in the ECA Policy.
• Allow nested ECA policy,e.g, one event to be able to call another nested event.
• Allow the NETCONF server send updates only when the value falls within a certain range.
• 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.
• 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:

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

• 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.
    • 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?

• 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 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.

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

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

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

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.

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
       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 {
      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.";
      }
      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.";
      }
      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
        "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
      "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
      "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;
        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 {
                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";
              }
              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";
            }
            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:

• /events/event/event-name
• /events/event/target
• /events/actions/target
• /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 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

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

  

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

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.

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>
           <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>
       <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:

  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

• Add text in introduction section to clarify the usage examples of ECA policy
• Update objective section to align with use cases.
• Clarify the relationship between target and policy variable.
• Change variation trigger condition back into threshold trigger condition and clarify the usage of three trigger conditions.
• Remove Event MIB related section.
• Add new coauthors.

v02 - v03

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

v01 - v02

• Introduce the group-id which allow group a set of events that can be executed together
• Change threshold trigger condition into variation trigger condition to further clarify the difference between boolean trigger condition and variation trigger condition.
• Module structure optimization.
• Usage Example Update.

v00 - v01

• Separate ietf-event-trigger.yang from Event management modeland ietf-event.yang and make it reusable in other YANG models.
• Clarify the difference between boolean trigger condition and threshold trigger condition.
• Change evt-smp-min and evt-smp-max into min-data-object and max-data-object in the data model.

Authors' Addresses