Network Working Group                                      J. Jeong, Ed.
Internet-Draft                                                 P. Lingga
Intended status: Standards Track                 Sungkyunkwan University
Expires: 30 July 1 August 2022                                          S. Hares
                                                                  L. Xia
                                                                  Huawei
                                                             H. Birkholz
                                                          Fraunhofer SIT
                                                         26
                                                         28 January 2022

             I2NSF NSF Monitoring Interface YANG Data Model
             draft-ietf-i2nsf-nsf-monitoring-data-model-13
             draft-ietf-i2nsf-nsf-monitoring-data-model-14

Abstract

   This document proposes an information model and the corresponding
   YANG data model of an interface for monitoring Network Security
   Functions (NSFs) in the Interface to Network Security Functions
   (I2NSF) framework.  If the monitoring of NSFs is performed with the
   NSF monitoring interface in a comprehensive way, it is possible to
   detect the indication of malicious activity, anomalous behavior, the
   potential sign of denial of service attacks, or system overload in a
   timely manner.  This monitoring functionality is based on the
   monitoring information that is generated by NSFs.  Thus, this
   document describes not only an information model for the NSF
   monitoring interface along with a YANG data diagram, but also the
   corresponding YANG data model.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 30 July 1 August 2022.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Use Cases for NSF Monitoring Data . . . . . . . . . . . . . .   4
   4.  Classification of NSF Monitoring Data . . . . . . . . . . . .   5
     4.1.  Retention and Emission  . . . . . . . . . . . . . . . . .   6
     4.2.  Notifications, Events, and Records  . . . . . . . . . . .   7
     4.3.  Unsolicited Poll and Solicited Pull . . . . . . . . . . .   8
   5.  Basic Information Model for Monitoring Data . . . . . . . . .   9
   6.  Extended Information Model for Monitoring Data  . . . . . . .  10
     6.1.  System Alarms . . . . . . . . . . . . . . . . . . . . . .  10
       6.1.1.  Memory Alarm  . . . . . . . . . . . . . . . . . . . .  11
       6.1.2.  CPU Alarm . . . . . . . . . . . . . . . . . . . . . .  11
       6.1.3.  Disk Alarm  . . . . . . . . . . . . . . . . . . . . .  11
       6.1.4.  Hardware Alarm  . . . . . . . . . . . . . . . . . . .  12
       6.1.5.  Interface Alarm . . . . . . . . . . . . . . . . . . .  12
     6.2.  System Events . . . . . . . . . . . . . . . . . . . . . .  13
       6.2.1.  Access Violation  . . . . . . . . . . . . . . . . . .  13
       6.2.2.  Configuration Change  . . . . . . . . . . . . . . . .  13
       6.2.3.  Session Table Event . . . . . . . . . . . . . . . . .  14
       6.2.4.  Traffic Flows . . . . . . . . . . . . . . . . . . . .  15
     6.3.  NSF Events  . . . . . . . . . . . . . . . . . . . . . . .  15
       6.3.1.  DDoS Detection  . . . . . . . . . . . . . . . . . . .  15
       6.3.2.  Virus Event . . . . . . . . . . . . . . . . . . . . .  16
       6.3.3.  Intrusion Event . . . . . . . . . . . . . . . . . . .  17
       6.3.4.  Web Attack Event  . . . . . . . . . . . . . . . . . .  18
       6.3.5.  VoIP/VoLTE Event  . . . . . . . . . . . . . . . . . .  19
     6.4.  System Logs . . . . . . . . . . . . . . . . . . . . . . .  19
       6.4.1.  Access Log  . . . . . . . . . . . . . . . . . . . . .  20
       6.4.2.  Resource Utilization Log  . . . . . . . . . . . . . .  20
       6.4.3.  User Activity Log . . . . . . . . . . . . . . . . . .  21
     6.5.  NSF Logs  . . . . . . . . . . . . . . . . . . . . . . . .  22
       6.5.1.  Deep Packet Inspection Log  . . . . . . . . . . . . .  22

     6.6.  System Counter  . . . . . . . . . . . . . . . . . . . . .  22
       6.6.1.  Interface Counter . . . . . . . . . . . . . . . . . .  23
     6.7.  NSF Counters  . . . . . . . . . . . . . . . . . . . . . .  24
       6.7.1.  Firewall Counter  . . . . . . . . . . . . . . . . . .  24
       6.7.2.  Policy Hit Counter  . . . . . . . . . . . . . . . . .  25
   7.  YANG Tree Structure of NSF Monitoring YANG Module . . . . . .  26
   8.  YANG Data Model of NSF Monitoring YANG Module . . . . . . . .  34
   9.  I2NSF Event Stream  . . . . . . . . . . . . . . . . . . . . .  82
   10. XML Examples for I2NSF NSF Monitoring . . . . . . . . . . . .  83
     10.1.  I2NSF System Detection Alarm . . . . . . . . . . . . . .  83
     10.2.  I2NSF Interface Counters . . . . . . . . . . . . . . . .  85
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  87
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  87
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  89
   14. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  89
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . .  90
     15.1.  Normative References . . . . . . . . . . . . . . . . . .  90
     15.2.  Informative References . . . . . . . . . . . . . . . . .  93
   Appendix A.  Changes from
           draft-ietf-i2nsf-nsf-monitoring-data-model-12
           draft-ietf-i2nsf-nsf-monitoring-data-model-13 . . . . . .  94
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  94

1.  Introduction

   According to [RFC8329], the interface provided by a Network Security
   Function (NSF) (e.g., Firewall, IPS, or Anti-DDoS function) to enable
   the collection of monitoring information is referred to as an I2NSF
   Monitoring Interface.  This interface enables the sharing of vital
   data from the NSFs (e.g., events, records, and counters) to the NSF
   data collector through a variety of mechanisms (e.g., queries and
   notifications).  The monitoring of NSF plays an important role in an
   overall security framework, if it is done in a timely and
   comprehensive way.  The monitoring information generated by an NSF
   can be a good, early indication of anomalous behavior or malicious
   activity, such as denial of service attacks (DoS).

   This document defines a comprehensive information model of an NSF
   monitoring interface that provides visibility into an NSF for the NSF
   data collector.  Note that an NSF data collector is defined as an
   entity to collect NSF monitoring data from an NSF, such as Security
   Controller.  It specifies the information and illustrates the methods
   that enable an NSF to provide the information required in order to be
   monitored in a scalable and efficient way via the NSF Monitoring
   Interface.  The information model for the NSF monitoring interface
   presented in this document is complementary for the security policy
   provisioning functionality of the NSF-Facing Interface specified in
   [I-D.ietf-i2nsf-nsf-facing-interface-dm].

   This document also defines a YANG [RFC7950] data model for the NSF
   monitoring interface, which is derived from the information model for
   the NSF monitoring interface.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document uses the terminology described in [RFC8329].  In
   addition, the following terms are defined in this document:

   *  I2NSF User: An entity that delivers a high-level security policy
      to the Security Controller and may request monitoring information
      via the NSF data collector.

   *  Monitoring Information: Relevant data that can be processed to
      know the status and performance of the network and the NSF.  The
      monitoring information in I2NSF environment consists of I2NSF
      Event, I2NSF Record, and I2NSF Counter (see Section 4.1 for the
      detailed definition).  This information is to be delivered to the
      NSF data collector.

   *  Notification: Unsolicited transmission of monitoring information.

   *  NSF Data Collector: An entity that collects NSF monitoring
      information from NSFs, such as Security Controller.

   *  Subscription: An agreement initialized by the NSF data collector
      to receive monitoring information from an NSF.  The method to
      subscribe follows the method explained in [RFC5277].

   This document follows the guidelines of [RFC8407], uses the common
   YANG types defined in [RFC6991], and adopts the Network Management
   Datastore Architecture (NMDA) [RFC8342].  The meaning of the symbols
   in tree diagrams is defined in [RFC8340].

3.  Use Cases for NSF Monitoring Data

   As mentioned earlier, monitoring plays a critical role in an overall
   security framework.  The monitoring of the NSF provides very valuable
   information to an NSF data collector (e.g., Security Controller) in
   maintaining the provisioned security posture.  Besides this, there
   are various other reasons to monitor the NSF as listed below:

   *  The I2NSF User that is the security administrator can configure a
      policy that is triggered on a specific event occurring in the NSF
      or the network [RFC8329]
      [I-D.ietf-i2nsf-consumer-facing-interface-dm].  If an NSF data
      collector detects the specified event, it configures additional
      security functions as defined by policies.

   *  The events triggered by an NSF as a result of security policy
      violation can be used by Security Information and Event Management
      (SIEM) to detect any suspicious activity in a larger correlation
      context.

   *  The information (i.e., events, records, and counters) from an NSF
      can be used to build advanced analytics, such as behavior and
      predictive models to improve security posture in large
      deployments.

   *  The NSF data collector can use events from the NSF for achieving
      high availability.  It can take corrective actions such as
      restarting a failed NSF and horizontally scaling up the NSF.

   *  The information (i.e., events, records, and counters) from the NSF
      can aid in the root cause analysis of an operational issue, so it
      can improve debugging.

   *  The records from the NSF can be used to build historical data for
      operation and business reasons.

4.  Classification of NSF Monitoring Data

   In order to maintain a strong security posture, it is not only
   necessary to configure an NSF's security policies but also to
   continuously monitor the NSF by consuming acquirable and observable
   data.  This enables security administrators to assess the state of
   the networks in a timely fashion.  It is not possible to block all
   the internal and external threats based on static security posture.
   A more practical approach is supported by enabling dynamic security
   measures, for which continuous visibility is required.  This document
   defines a set of monitoring elements and their scopes that can be
   acquired from an NSF and can be used as NSF monitoring data.  In
   essence, this monitoring data can be leveraged to support constant
   visibility on multiple levels of granularity and can be consumed by
   the corresponding functions.

   Three basic domains about the monitoring data originating from a
   system entity [RFC4949], i.e., an NSF, are highlighted in this
   document.

   *  Retention and Emission

   *  Notifications, Events, and Records

   *  Unsolicited Poll and Solicited Pull

   Every system entity creates information about some context with
   defined I2NSF monitoring data, and so every entity can be an I2NSF
   component.  This information is intended to be consumed by other
   I2NSF components, which deals with NSF monitoring data in an
   automated fashion.

4.1.  Retention and Emission

   A system entity (e.g., NSF) first retains I2NSF monitoring data
   inside its own system before emitting the information to another
   I2NSF component (e.g., NSF Data Collector).  The I2NSF monitoring
   information consist of I2NSF Event, I2NSF Record, and I2NSF Counter
   as follows:

   I2NSF Event:  I2NSF Event is defined as an important occurrence at a
      particular time, that is, a change in the system being managed or
      a change in the environment of the system being managed.  An I2NSF
      Event requires immediate attention and should be notified as soon
      as possible.  When used in the context of an (imperative) I2NSF
      Policy Rule, an I2NSF Event is used to determine whether the
      Condition clause of that Policy Rule can be evaluated or not.  The
      Alarm Management Framework in [RFC3877] defines an event as
      something that happens which may be of interest.  Examples for an
      event are a fault, a change in status, crossing a threshold, or an
      external input to the system.  In the I2NSF domain, I2NSF events
      are created following the definition of an event in the Alarm
      Management Framework.

   I2NSF Record:  A record is defined as an item of information that is
      kept to be looked at and used in the future.  Typically, records
      are information generated by a system entity (e.g., NSF) that is
      based on operational and informational data (i.e., various changes
      in system characteristics), and are generated at particular
      instants to be kept without any changes afterward.  A set of
      records has an ordering in time based on when they are generated.
      Unlike I2NSF Event, records do not require immediate attention but
      may be useful for visibility and retroactive cyber forensic.
      Records are typically stored in log-files or databases on a system
      entity or NSF.  The examples of records include as user
      activities, device performance, and network status.  They are
      important for debugging, auditing, and security forensic of a
      system entity or the network having the system entity.

   I2NSF Counter:  An I2NSF Counter is defined as a specific
      representation of an information element whose value changes very
      frequently.  Prominent examples are network interface counters for
      protocol data unit (PDU) amount, byte amount, drop counters, and
      error counters.  Other examples are integer approximations to
      continuous values, such as a processor temperature measured in
      tenths of a degree or the percentage of a disk that is used.
      Counters are useful in debugging and visibility into operational
      behavior of a system entity (e.g., NSF).  When an NSF data
      collector asks for the value of a counter to it, a system entity
      MUST update the counter information and emit the latest
      information to the NSF data collector.

   The retention of I2NSF monitoring information may be affected by the
   importance of the data.  The importance of the data could be context-
   dependent, where it may not just be based on the type of data, but
   may also depend on where it is deployed, e.g., a test lab and
   testbed.  The local policy and configuration will dictate the
   policies and procedures to review, archive, or purge the collected
   monitoring data.

   The I2NSF monitoring information retained on a system entity (e.g.,
   NSF) may be delivered to a corresponding I2NSF User via an NSF data
   collector.  The information consists of the aggregated records,
   typically in the form of log-files or databases.  For the NSF
   Monitoring Interface to deliver the information to the NSF data
   collector, the NSF needs to accommodate standardized delivery
   protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040].  The NSF
   data collector can forward the information to the I2NSF User through
   one of standardized delivery protocols.  The interface for this
   delivery is out of the scope of this document.

4.2.  Notifications, Events, and Records

   A specific task of I2NSF User is to process I2NSF Policy Rules.  The
   rules of a policy are composed of three clauses: Event, Condition,
   and Action clauses.  In consequence, an I2NSF Event is specified to
   trigger the evaluation of the Condition clause of the I2NSF Policy
   Rule.  Such an I2NSF Event is defined as an important occurrence at a
   particular time in the system being managed, and/or in the
   environment of the system being managed whose concept aligns well
   with the generic definition of Event from [RFC3877].

   Another role of the I2NSF Event is to trigger a notification for
   monitoring the status of an NSF.  A notification is defined in
   [RFC3877] as an unsolicited transmission of management information.
   System alarm (called alarm) is defined as a warning related to
   service degradation in system hardware in Section 6.1.  System event
   (called alert) is defined as a warning about any changes of
   configuration, any access violation, the information of sessions and
   traffic flows in Section 6.2.  Both an alarm and an alert are I2NSF
   Events that can be delivered as a notification.  The model
   illustrated in this document introduces a complementary type of
   information that can be a conveyed notification.

   In I2NSF monitoring, a notification is used to deliver either an
   event and a record via the I2NSF Monitoring Interface.  The
   difference between the event and record is the timing by which the
   notifications are emitted.  An event is emitted as soon as it happens
   in order to notify an NSF Data Collector of the problem that needs
   immediate attention.  A record is not emitted immediately to the NSF
   Data Collector, and it can be emitted periodically to the NSF Data
   Collector every certain time interval.

   It is important to note that an NSF Data Collector as a consumer
   (i.e., observer) of a notification assesses the importance of the
   notification rather than an NSF as a producer.  The producer can
   include metadata in a notification that supports the observer in
   assessing its importance (e.g., severity).

4.3.  Unsolicited Poll and Solicited Pull

   An important aspect of monitoring information is the freshness of the
   information.  From the perspective of security, it is important to
   notice the current status of the network.  The I2NSF Monitoring
   Interface provides the means of sending monitored information from
   the NSFs to an NSF data collector in a timely manner.  The method of
   acquiring the monitoring information can be performed from a client
   (i.e., NSF data collector) to a server (i.e., NSF) by unsolicited
   poll or solicited pull.

   The solicited pull is a query-based method to obtain information from
   the NSF.  In this method, the NSF will remain passive until the
   information is requested from the NSF data collector.  Once a new
   request is accepted (with proper authentication), the NSF MUST update
   the information before sending it to the NSF data collector.

   The unsolicited poll is a report-based method to obtain information
   from the NSF.  The report-based method ensures the information can be
   delivered immediately without any requests.  This method is used by
   the NSF to actively provide information to the NSF data collector.
   To receive the information, the NSF data collector subscribes to the
   NSF for the information.

   These acquisition methods are used for different types of monitoring
   information.  The information that has a high level of urgency (i.e.,
   I2NSF Event) should be provided with the unsolicited poll method,
   while information that has a lower level of urgency (i.e., I2NSF
   Record and I2NSF Counter) can be provided with either the solicited
   pull method or unsolicited poll method.

5.  Basic Information Model for Monitoring Data

   As explained in the above section, there is a wealth of data
   available from the NSF that can be monitored.  Firstly, there must be
   some general information with each monitoring message sent from an
   NSF that helps a consumer to identify meta data with that message,
   which are listed as below:

   *  message: The extra detailed description on NSF monitoring data to
      give an NSF data collector the context information as meta data.

   *  vendor-name: The vendor's name of the NSF that generates the
      message.

   *  device-model: The model of the device, can be represented by the
      device model name or serial number.  This field is used to
      identify the model of the device that provides the security
      service.

   *  software-version: The version of the software used to provide the
      security service.

   *  nsf-name: The name or IP address of the NSF generating the
      message.  If the given nsf-name is not IP address, the name can be
      an arbitrary string including FQDN (Fully Qualified Domain Name).
      The name MUST be unique in the scope of management domain for a
      different NSF to identify the NSF that generates the message.

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  timestamp: The time when the message is generated.  For the
      notification operations (i.e., System Alarms, System Events, NSF
      Events, System Logs, and NSF Logs), this is represented by the
      eventTime of NETCONF event notification [RFC5277] For other
      operations (i.e., System Counter and NSF Counter), the timestamp
      MUST be provided separately.

   *  language: describes the human language intended for the user, so
      that it allows a user to differentiate the language that is used
      in the notification.  This field is not mandatory, but required
      when the implementation provides more than one human language for
      the human-readable string fields.

6.  Extended Information Model for Monitoring Data

   The extended information model is the specific monitoring data that
   covers the additional information associated with the detailed
   information of status and performance of the network and the NSF over
   the basic information model.  The extended information combined with
   the basic information creates the monitoring information (i.e., I2NSF
   Event, Record, and Counter).

   The extended monitoring information has characteristics for data
   collection setting as follows:

   *  Acquisition method: The method to obtain the message.  It can be a
      "query" or a "subscription".  A "query" is a request-based method
      to acquire the solicited information.  A "subscription" is a
      report-based method to acquire the unsolicited information.

   *  Emission type: The cause type for the message to be emitted.  It
      can be "on-change", "periodic", or "on-request".  An "on-change"
      message is emitted when an important event happens in the NSF.  A
      "periodic" message is emitted at a certain time interval.  An "on-
      request" message is emitted when the information is requested.
      The time to periodically emit the message is configurable.

   *  Dampening type: The type of message dampening to stop the rapid
      transmission of messages.  The dampening types are "on-repetition"
      and "no-dampening".  The "on-repetition" type limits the
      transmitted "on-change" message to one message at a certain
      interval (e.g., 1 second).  This interval is defined as dampening-
      period in [RFC8641].  The dampening-period is configurable.  The
      "no-dampening" type does not limit the transmission for the
      messages of the same type.  In short, "on-repetition" means that
      the dampening is active and "no-dampening" is inactive.  It is
      recommended to activate the dampening for an "on-change" type of
      message to reduce the number of messages generated.

6.1.  System Alarms

   System alarms have the following characteristics:

   *  acquisition-method: subscription
   *  emission-type: on-change

   *  dampening-type: on-repetition or no-dampening

6.1.1.  Memory Alarm

   The memory is the hardware to store information temporarily or for a
   short period, i.e., Random Access Memory (RAM).  The memory-alarm is
   emitted when the RAM usage exceeds the threshold.  The following
   information should be included in a Memory Alarm:

   *  event-name: memory-alarm.

   *  usage: specifies the size of memory used.

   *  threshold: The threshold triggering the alarm

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  message: Simple information such as "The memory usage exceeded the
      threshold" or with extra information.

6.1.2.  CPU Alarm

   CPU is the Central Processing Unit that executes basic operations of
   the system.  The cpu-alarm is emitted when the CPU usage exceeds the
   threshold.  The following information should be included in a CPU
   Alarm:

   *  event-name: cpu-alarm.

   *  usage: Specifies the CPU utilization.

   *  threshold: The threshold triggering the event.

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  message: Simple information such as "The CPU usage exceeded the
      threshold" or with extra information.

6.1.3.  Disk Alarm

   Disk is the hardware to store information for a long period, i.e.,
   Hard Disk or Solid-State Drive.  The disk-alarm is emitted when the
   Disk usage exceeds the threshold.  The following information should
   be included in a Disk Alarm:

   *  event-name: disk-alarm.

   *  usage: Specifies the size of disk space used.

   *  threshold: The threshold triggering the event.

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  message: Simple information such as "The disk usage exceeded the
      threshold" or with extra information.

6.1.4.  Hardware Alarm

   The hardware-alarm is emitted when a hardware, e.g., CPU, memory,
   disk, or interface, problem is detected.  The following information
   should be included in a Hardware Alarm:

   *  event-name: hardware-alarm.

   *  component-name: It indicates the hardware component responsible
      for generating this alarm.

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  message: Simple information such as "The hardware component has
      failed or degraded" or with extra information.

6.1.5.  Interface Alarm

   Interface is the network interface for connecting a device with the
   network.  The interface-alarm is emitted when the state of the
   interface is changed.  The following information should be included
   in an Interface Alarm:

   *  event-name: interface-alarm.

   *  interface-name: The name of the interface.

   *  interface-state: down, up (not congested), congested (up but
      congested).

   *  severity: The severity level of the message.  There are total four
      levels, i.e., critical, high, middle, and low.

   *  message: Simple information such as "The interface is 'interface-
      state'" or with extra information.

6.2.  System Events

   System events (as alerts) have the following characteristics:

   *  acquisition-method: subscription

   *  emission-type: on-change

   *  dampening-type: on-repetition or no-dampening

6.2.1.  Access Violation

   The access-violation system event is an event when a user tries to
   access (read, write, create, or delete) any information or execute
   commands above their privilege.  The following information should be
   included in this event:

   *  event-name: access-violation.

   *  identity: The information to identify the attempted access
      violation.  The minimum information (extensible) that should be
      included:

      1.  user: The unique username that attempted access violation.

      2.  group: Group(s) to which a user belongs.  A user can belong to
          multiple groups.

      3.  ip-address: The IP address of the user that triggered the
          event.

      4.  port-number: The port number used by the user.

   *  authentication: The method to verify the valid user, i.e., pre-
      configured-key and certificate-authority.

   *  message: The message to give the context of the event, such as
      "Access is denied".

6.2.2.  Configuration Change

   A configuration change is a system event when a new configuration is
   added or an existing configuration is modified.  The following
   information should be included in this event:

   *  event-name: configuration-change.

   *  identity: The information to identify the attempted access
      violation.  The minimum information (extensible) that should be
      included:

      1.  user: The unique username that changes the configuration.

      2.  group: Group(s) to which a user belongs.  A user can belong to
          multiple groups.

      3.  ip-address: The IP address of the user that triggered the
          event.

      4.  port-number: The port number used by the user.

   *  authentication: The method to verify the valid user, i.e., pre-
      configured-key and certificate-authority.

   *  message: The message to give the context of the event, such as
      "Configuration is modified", "New configuration is added", or "A
      configuration has been removed".

   *  changes: Describes the modification that was made to the
      configuration.  The minimum information that must be provided is
      the name of the policy that has been altered (added, modified, or
      removed).  Other detailed information about the configuration
      changes is up to the implementation.

6.2.3.  Session Table Event

   Session Table Event is the event triggered by the session table of an
   NSF.  A session table holds the information of the current active
   sessions.  The following information should be included in a Session
   Table Event:

   *  event-name: detection-session-table.

   *  current-session: The number of concurrent sessions.

   *  maximum-session: The maximum number of sessions that the session
      table can support.

   *  threshold: The threshold triggering the event.

   *  message: The message to give the context of the event, such as
      "The number of session table exceeded the threshold".

6.2.4.  Traffic Flows

   Traffic flows need to be monitored because they might be used for
   security attacks to the network.  The following information should be
   included in this event:

   *  event-name: traffic-flows.

   *  src-ip: The source IPv4 or IPv6 address of the traffic flow.

   *  dst-ip: The destination IPv4 or IPv6 address of the traffic flow.

   *  src-port: The source port of the traffic flow.

   *  dst-port: The destination port of the traffic flow.

   *  protocol: The protocol of the traffic flow.

   *  arrival-rate: Arrival rate of packets of the traffic flow in
      packet per second.

   *  arrival-speed: Arrival rate of packets of the traffic flow in
      bytes per second.

6.3.  NSF Events

   NSF events have the following characteristics:

   *  acquisition-method: subscription

   *  emission-type: on-change

   *  dampening-type: on-repetition or no-dampening

6.3.1.  DDoS Detection

   The following information should be included in a DDoS Event:

   *  event-name: detection-ddos.

   *  attack-type: The type of DDoS Attack, i.e., SYN flood, ACK flood,
      SYN-ACK flood, FIN/RST flood, TCP Connection flood, UDP flood,
      ICMP flood, HTTPS flood, HTTP flood, DNS query flood, DNS reply
      flood, SIP flood, SSL flood, and NTP amplification flood.  This
      can be extended with additional types of DDoS attack.

   *  attack-src-ip: The IP address of the source of the DDoS attack.

   *  attack-dst-ip: The network prefix with a network mask (for IPv4)
      or prefix length (for IPv6) of a victim under DDoS attack.

   *  dst-port: The port number that the attack traffic aims at.

   *  start-time: The time stamp indicating when the attack started.

   *  end-time: The time stamp indicating when the attack ended.  If the
      attack is still undergoing when sending out the notification, this
      field can be empty.

   *  attack-rate: The packets per second of attack traffic.

   *  attack-speed: The bytes per second of attack traffic.

   *  rule-name: The name of the I2NSF Policy Rule being triggered.
      Note that rule-name is used to match a detected NSF event with a
      policy rule in [I-D.ietf-i2nsf-nsf-facing-interface-dm].

6.3.2.  Virus Event

   This information is used when a virus is detected within the traffic
   flow or inside the host.  The following information should be
   included in a Virus Event:

   *  event-name: detection-virus.

   *  virus-name: Name of the virus.

   *  virus-type: Type of the virus. e.g., trojan, worm, macro virus
      type.

   *  dst-ip: The destination IP address of the flow where the virus is
      found.  This is used when the virus is detected within the traffic
      flow.

   *  src-ip: The source IP address of the flow where the virus is
      found.  This is used when the virus is detected within the traffic
      flow.

   *  src-port: The source port of the flow where the virus is found.
      This is used when the virus is detected within the traffic flow.

   *  dst-port: The destination port of the flow where the virus is
      found.  This is used when the virus is detected within the traffic
      flow.

   *  src-location: The geographical location (e.g., country and city)
      of the src-ip field.  This is used when the virus is detected
      within the traffic flow.

   *  dst-location: The geographical location (e.g., country and city)
      of the dst-ip field.  This is used when the virus is detected
      within the traffic flow.

   *  host: The name or IP address of the host/device that is infected
      by the virus.  This is used when the virus is detected within a
      host system.  If the given name is not IP address, the name can be
      an arbitrary string including FQDN (Fully Qualified Domain Name).
      The name MUST be unique in the scope of management domain for
      identifying the device that has been infected with a virus.

   *  os: The operating system of the host that has the virus.  This is
      used when the virus is detected within a host system.

   *  file-type: The type of the file where the virus is hidden.  This
      is used when the virus is detected within a host system.

   *  file-name: The name of the file where the virus is hidden.  This
      is used when the virus is detected within a host system.

   *  rule-name: The name of the rule being triggered.

6.3.3.  Intrusion Event

   The following information should be included in an Intrusion Event:

   *  event-name: detection-intrusion.

   *  attack-type: Attack type, e.g., brutal force and buffer overflow.

   *  src-ip: The source IP address of the flow.

   *  dst-ip: The destination IP address of the flow.

   *  src-port:The source port number of the flow.

   *  dst-port: The destination port number of the flow

   *  src-location: The source geographical location (e.g., country and
      city) of the src-ip field.

   *  dst-location: The destination geographical location (e.g., country
      and city) of the dst-ip field.

   *  protocol: The employed transport layer protocol. e.g., TCP and
      UDP.

   *  app: The employed application layer protocol. e.g., HTTP and FTP.

   *  rule-name: The name of the I2NSF Policy Rule being triggered.

6.3.4.  Web Attack Event

   The following information should be included in a Web Attack Alarm:

   *  event-name: detection-web-attack.

   *  attack-type: Concrete web attack type. e.g., SQL injection,
      command injection, XSS, CSRF.

   *  src-ip: The source IP address of the packet.

   *  dst-ip: The destination IP address of the packet.

   *  src-port: The source port number of the packet.

   *  dst-port: The destination port number of the packet.

   *  src-location: The source geographical location (e.g., country and
      city) of the src-ip field.

   *  dst-location: The destination geographical location (e.g., country
      and city) of the dst-ip field.

   *  req-method: The HTTP method of the request.  For instance, "PUT"
      and "GET" in HTTP.

   *  req-target: The HTTP Request Target.

   *  response-code: The HTTP Response status code.

   *  req-user-agent: The HTTP User-Agent header field of the request.

   *  cookies: The HTTP Cookie header field of the request from the user
      agent.

   *  req-host: The HTTP Host header field of the request.

   *  filtering-type: URL filtering type. e.g., deny-list, allow-list,
      and unknown.

   *  rule-name: The name of the I2NSF Policy Rule being triggered.

6.3.5.  VoIP/VoLTE Event

   The following information should be included in a VoIP/VoLTE Event:

   *  event-name: detection-voip-volte

   *  source-voice-id: The detected source voice Call ID for VoIP and
      VoLTE that violates the policy.

   *  destination-voice-id: The destination voice Call ID for VoIP and
      VoLTE that violates the policy.

   *  user-agent: The user agent for VoIP and VoLTE that violates the
      policy.

   *  src-ip: The source IP address of the VoIP/VoLTE.

   *  dst-ip: The destination IP address of the VoIP/VoLTE.

   *  src-port: The source port number of the VoIP/VoLTE.

   *  dst-port: The destination port number of VoIP/VoLTE.

   *  src-location: The source geographical location (e.g., country and
      city) of the src-ip field.

   *  dst-location: The destination geographical location (e.g., country
      and city) of the dst-ip field.

   *  rule-name: The name of the I2NSF Policy Rule being triggered.

6.4.  System Logs

   System log is a record that is used to monitor the activity of the
   user on the NSF and the status of the NSF.  System logs have the
   following characteristics:

   *  acquisition-method: subscription or query

   *  emission-type: on-change, periodic, or on-request

   *  dampening-type: on-repetition or no-dampening

6.4.1.  Access Log

   Access logs record administrators' login, logout, and operations on a
   device.  By analyzing them, security vulnerabilities can be
   identified.  The following information should be included in an
   operation report:

   *  identity: The information to identify the user.  The minimum
      information (extensible) that should be included:

      1.  user: The unique username that attempted access violation.

      2.  group: Group(s) to which a user belongs.  A user can belong to
          multiple groups.

      3.  ip-address: The IP address of the user that triggered the
          event.

      4.  port-number: The port number used by the user.

   *  authentication: The method to verify the valid user, i.e., pre-
      configured-key and certificate-authority.

   *  operation-type: The operation type that the administrator execute,
      e.g., login, logout, configuration, and other.

   *  input: The operation performed by a user after login.  The
      operation is a command given by a user.

   *  output: The result after executing the input.

6.4.2.  Resource Utilization Log

   Running reports record the device system's running status, which is
   useful for device monitoring.  The following information should be
   included in running report:

   *  system-status: The current system's running status.

   *  cpu-usage: Specifies the aggregated CPU usage.

   *  memory-usage: Specifies the memory usage.

   *  disk-id: Specifies the disk ID to identify the storage disk.

   *  disk-usage: Specifies the disk usage of disk-id.

   *  disk-left: Specifies the available disk space left of disk-id.

   *  session-number: Specifies total concurrent sessions.

   *  process-number: Specifies total number of systems processes.

   *  interface-id: Specifies the interface ID to identify the network
      interface.

   *  in-traffic-rate: The total inbound traffic rate in packets per
      second.

   *  out-traffic-rate: The total outbound traffic rate in packets per
      second.

   *  in-traffic-speed: The total inbound traffic speed in bytes per
      second.

   *  out-traffic-speed: The total outbound traffic speed in bytes per
      second.

6.4.3.  User Activity Log

   User activity logs provide visibility into users' online records
   (such as login time, online/lockout duration, and login IP addresses)
   and the actions that users perform.  User activity reports are
   helpful to identify exceptions during a user's login and network
   access activities.  This information should be included in a user's
   activity report:

   *  identity: The information to identify the user.  The minimum
      information (extensible) that should be included:

      1.  user: The unique username that attempted access violation.

      2.  group: Group(s) to which a user belongs.  A user can belong to
          multiple groups.

      3.  ip-address: The IP address of the user that triggered the
          event.

      4.  port-number: The port number used by the user.

   *  authentication: The method to verify the valid user, i.e., pre-
      configured-key and certificate-authority.

   *  online-duration: The duration of a user's activeness (stays in
      login) during a session.

   *  logout-duration: The duration of a user's inactiveness (not in
      login) from the last session.

   *  additional-info: Additional Information for login:

      1.  type: User activities. e.g., Successful User Login, Failed
          Login attempts, User Logout, Successful User Password Change,
          Failed User Password Change, User Lockout, and User Unlocking.

      2.  cause: Cause of a failed user activity.

6.5.  NSF Logs

   NSF logs have the folowing characteristics:

   *  acquisition-method: subscription or query

   *  emission-type: on-change or on-request

   *  dampening-type: on-repetition or no-dampening

6.5.1.  Deep Packet Inspection Log

   Deep Packet Inspection (DPI) Logs provide statistics on uploaded and
   downloaded files and data, sent and received emails, and alert and
   blocking records on websites.  It is helpful to learn risky user
   behaviors and why access to some URLs is blocked or allowed with an
   alert record.

   *  attack-type: DPI action types. e.g., File Blocking, Data
      Filtering, and Application Behavior Control.

   *  src-user: The I2NSF User's name who generates the policy.

   *  policy-name: Security policy name that traffic matches.

   *  action: Action defined in the file blocking rule, data filtering
      rule, or application behavior control rule that traffic matches.

6.6.  System Counter

   System counter has the following characteristics:

   *  acquisition-method: subscription or query

   *  emission-type: periodic or on-request

   *  dampening-type: no-dampening

6.6.1.  Interface Counter

   Interface counters provide visibility into traffic into and out of an
   NSF, and bandwidth usage.  The statistics of the interface counters
   should be computed from the start of the service.  When the service
   is reset, the computation of statistics per counter should restart
   from 0.

   *  interface-name: Network interface name configured in NSF.

   *  in-total-traffic-pkts: Total inbound packets.

   *  out-total-traffic-pkts: Total outbound packets.

   *  in-total-traffic-bytes: Total inbound bytes.

   *  out-total-traffic-bytes: Total outbound bytes.

   *  in-drop-traffic-pkts: Total inbound drop packets.

   *  out-drop-traffic-pkts: Total outbound drop packets.

   *  in-drop-traffic-bytes: Total inbound drop bytes.

   *  out-drop-traffic-bytes: Total outbound drop bytes.

   *  in-traffic-average-rate: Inbound traffic average rate in packets
      per second.

   *  in-traffic-peak-rate: Inbound traffic peak rate in packets per
      second.

   *  in-traffic-average-speed: Inbound traffic average speed in bytes
      per second.

   *  in-traffic-peak-speed: Inbound traffic peak speed in bytes per
      second.

   *  out-traffic-average-rate: Outbound traffic average rate in packets
      per second.

   *  out-traffic-peak-rate: Outbound traffic peak rate in packets per
      second.

   *  out-traffic-average-speed: Outbound traffic average speed in bytes
      per second.

   *  out-traffic-peak-speed: Outbound traffic peak speed in bytes per
      second.

   *  discontinuity-time: The time on the most recent occasion at which
      any one or more of the counters suffered a discontinuity.  If no
      such discontinuities have occurred since the last re-
      initialization of the local management subsystem, then this node
      contains the time the local management subsystem was re-
      initialized.

6.7.  NSF Counters

   NSF counters have the following characteristics:

   *  acquisition-method: subscription or query

   *  emission-type: periodic or on-request

   *  dampening-type: no-dampening

6.7.1.  Firewall Counter

   Firewall counters provide visibility into traffic signatures,
   bandwidth usage, and how the configured security and bandwidth
   policies have been applied.

   *  src-ip: Source IP address of traffic.

   *  src-user: The I2NSF User's name who generates the policy.

   *  dst-ip: Destination IP address of traffic.

   *  src-port: Source port of traffic.

   *  dst-port: Destination port of traffic.

   *  protocol: Protocol type of traffic.

   *  app: Application type of traffic.

   *  policy-id: Security policy id that traffic matches.

   *  policy-name: Security policy name that traffic matches.

   *  in-interface: Inbound interface of traffic.

   *  out-interface: Outbound interface of traffic.

   *  total-traffic: Total traffic volume.

   *  in-traffic-average-rate: Inbound traffic average rate in packets
      per second.

   *  in-traffic-peak-rate: Inbound traffic peak rate in packets per
      second.

   *  in-traffic-average-speed: Inbound traffic average speed in bytes
      per second.

   *  in-traffic-peak-speed: Inbound traffic peak speed in bytes per
      second.

   *  out-traffic-average-rate: Outbound traffic average rate in packets
      per second.

   *  out-traffic-peak-rate: Outbound traffic peak rate in packets per
      second.

   *  out-traffic-average-speed: Outbound traffic average speed in bytes
      per second.

   *  out-traffic-peak-speed: Outbound traffic peak speed in bytes per
      second.

   *  discontinuity-time: The time on the most recent occasion at which
      any one or more of the counters suffered a discontinuity.  If no
      such discontinuities have occurred since the last re-
      initialization of the local management subsystem, then this node
      contains the time the local management subsystem was re-
      initialized.

6.7.2.  Policy Hit Counter

   Policy Hit Counters record the security policy that traffic matches
   and its hit count.  It can check if policy configurations are
   correct.

   *  src-ip: Source IP address of traffic.

   *  src-user: The I2NSF User's name who generates the policy.

   *  dst-ip: Destination IP address of traffic.

   *  src-port: Source port of traffic.

   *  dst-port: Destination port of traffic.

   *  protocol: Protocol type of traffic.

   *  app: Application type of traffic.

   *  policy-id: Security policy id that traffic matches.

   *  policy-name: Security policy name that traffic matches.

   *  hit-times: The number of times that the security policy matches
      the specified traffic.

   *  discontinuity-time: The time on the most recent occasion at which
      any one or more of the counters suffered a discontinuity.  If no
      such discontinuities have occurred since the last re-
      initialization of the local management subsystem, then this node
      contains the time the local management subsystem was re-
      initialized.

7.  YANG Tree Structure of NSF Monitoring YANG Module

   The tree structure of the NSF monitoring YANG module is provided
   below:

   module: ietf-i2nsf-nsf-monitoring
     +--ro i2nsf-counters
     |  +--ro language?           string
     |  +--ro system-interface* [interface-name]
     |  |  +--ro acquisition-method?          identityref
     |  |  +--ro emission-type?               identityref
     |  |  +--ro dampening-type?              identityref
     |  |  +--ro interface-name               if:interface-ref
     |  |  +--ro in-total-traffic-pkts?       yang:counter64
     |  |  +--ro out-total-traffic-pkts?      yang:counter64
     |  |  +--ro in-total-traffic-bytes?      uint64
     |  |  +--ro out-total-traffic-bytes?     uint64
     |  |  +--ro in-drop-traffic-pkts?        yang:counter64
     |  |  +--ro out-drop-traffic-pkts?       yang:counter64
     |  |  +--ro in-drop-traffic-bytes?       uint64
     |  |  +--ro out-drop-traffic-bytes?      uint64
     |  |  +--ro discontinuity-time           yang:date-and-time
     |  |  +--ro total-traffic?               yang:counter64
     |  |  +--ro in-traffic-average-rate?     uint32
     |  |  +--ro in-traffic-peak-rate?        uint32
     |  |  +--ro in-traffic-average-speed?    uint64
     |  |  +--ro in-traffic-peak-speed?       uint64
     |  |  +--ro out-traffic-average-rate?    uint32
     |  |  +--ro out-traffic-peak-rate?       uint32
     |  |  +--ro out-traffic-average-speed?   uint64
     |  |  +--ro out-traffic-peak-speed?      uint64
     |  |  +--ro message?                     string
     |  |  +--ro vendor-name?                 string
     |  |  +--ro nsf-name?                    union
     |  |  +--ro severity?                    severity
     |  |  +--ro timestamp?                   yang:date-and-time
     |  +--ro nsf-firewall* [policy-name]
     |  |  +--ro acquisition-method?          identityref
     |  |  +--ro emission-type?               identityref
     |  |  +--ro dampening-type?              identityref
     |  |  +--ro policy-name
                    -> /nsfintf:i2nsf-security-policy/name
     |  |  +--ro src-user?                    string
     |  |  +--ro discontinuity-time           yang:date-and-time
     |  |  +--ro total-traffic?               yang:counter64
     |  |  +--ro in-traffic-average-rate?     uint32
     |  |  +--ro in-traffic-peak-rate?        uint32
     |  |  +--ro in-traffic-average-speed?    uint64
     |  |  +--ro in-traffic-peak-speed?       uint64
     |  |  +--ro out-traffic-average-rate?    uint32
     |  |  +--ro out-traffic-peak-rate?       uint32
     |  |  +--ro out-traffic-average-speed?   uint64
     |  |  +--ro out-traffic-peak-speed?      uint64
     |  |  +--ro message?                     string
     |  |  +--ro vendor-name?                 string
     |  |  +--ro nsf-name?                    union
     |  |  +--ro severity?                    severity
     |  |  +--ro timestamp?                   yang:date-and-time
     |  +--ro nsf-policy-hits* [policy-name]
     |     +--ro acquisition-method?   identityref
     |     +--ro emission-type?        identityref
     |     +--ro dampening-type?       identityref
     |     +--ro policy-name
                    -> /nsfintf:i2nsf-security-policy/name
     |     +--ro src-user?             string
     |     +--ro message?              string
     |     +--ro vendor-name?          string
     |     +--ro nsf-name?             union
     |     +--ro severity?             severity
     |     +--ro discontinuity-time    yang:date-and-time
     |     +--ro hit-times?            yang:counter64
     |     +--ro timestamp?            yang:date-and-time
     +--rw i2nsf-monitoring-configuration
        +--rw i2nsf-system-detection-alarm
        |  +--rw enabled?        boolean
        |  +--rw system-alarm* [alarm-type]
        |     +--rw alarm-type          enumeration
        |     +--rw threshold?          uint8
        |     +--rw dampening-period?   uint32
        +--rw i2nsf-system-detection-event
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-traffic-flows
        |  +--rw dampening-period?   uint32
        |  +--rw enabled?            boolean
        +--rw i2nsf-nsf-detection-ddos {i2nsf-nsf-detection-ddos}?
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-nsf-detection-session-table
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-nsf-detection-intrusion
                                        {i2nsf-nsf-detection-intrusion}?
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-nsf-detection-web-attack
                                       {i2nsf-nsf-detection-web-attack}?
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-nsf-system-access-log
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-system-res-util-log
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-system-user-activity-log
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-nsf-log-dpi {i2nsf-nsf-log-dpi}?
        |  +--rw enabled?            boolean
        |  +--rw dampening-period?   uint32
        +--rw i2nsf-counter
           +--rw period?   uint16

     notifications:
       +---n i2nsf-event
       |  +--ro language?                                  string
       |  +--ro (sub-event-type)?
       |     +--:(i2nsf-system-detection-alarm)
       |     |  +--ro i2nsf-system-detection-alarm
       |     |     +--ro alarm-category?       identityref
       |     |     +--ro component-name?       string
       |     |     +--ro interface-name?       if:interface-ref
       |     |     +--ro interface-state?      enumeration
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro usage?                uint8
       |     |     +--ro threshold?            uint8
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     +--:(i2nsf-system-detection-event)
       |     |  +--ro i2nsf-system-detection-event
       |     |     +--ro event-category?       identityref
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro user                  string
       |     |     +--ro group*                string
       |     |     +--ro ip-address            inet:ip-address-no-zone
       |     |     +--ro port-number           inet:port-number
       |     |     +--ro authentication?       identityref
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     |     +--ro changes* [policy-name]
       |     |        +--ro policy-name
                    -> /nsfintf:i2nsf-security-policy/name
       |     +--:(i2nsf-traffic-flows)
       |     |  +--ro i2nsf-traffic-flows
       |     |     +--ro src-ip?               inet:ip-address-no-zone
       |     |     +--ro dst-ip?               inet:ip-address-no-zone
       |     |     +--ro protocol?             identityref
       |     |     +--ro src-port?             inet:port-number
       |     |     +--ro dst-port?             inet:port-number
       |     |     +--ro arrival-rate?         uint32
       |     |     +--ro arrival-speed?        uint32
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     +--:(i2nsf-nsf-detection-session-table)
       |        +--ro i2nsf-nsf-detection-session-table
       |           +--ro current-session?   uint32
       |           +--ro maximum-session?   uint32
       |           +--ro threshold?         uint32
       |           +--ro message?           string
       |           +--ro vendor-name?       string
       |           +--ro nsf-name?          union
       |           +--ro severity?          severity
       +---n i2nsf-log
       |  +--ro language?                               string
       |  +--ro (sub-logs-type)?
       |     +--:(i2nsf-nsf-system-access-log)
       |     |  +--ro i2nsf-nsf-system-access-log
       |     |     +--ro user                  string
       |     |     +--ro group*                string
       |     |     +--ro ip-address            inet:ip-address-no-zone
       |     |     +--ro port-number           inet:port-number
       |     |     +--ro authentication?       identityref
       |     |     +--ro operation-type?       operation-type
       |     |     +--ro input?                string
       |     |     +--ro output?               string
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     +--:(i2nsf-system-res-util-log)
       |     |  +--ro i2nsf-system-res-util-log
       |     |     +--ro system-status?        enumeration
       |     |     +--ro cpu-usage?            uint8
       |     |     +--ro memory-usage?         uint8
       |     |     +--ro disk* [disk-id]
       |     |     |  +--ro disk-id       string
       |     |     |  +--ro disk-usage?   uint8
       |     |     |  +--ro disk-left?    uint8
       |     |     +--ro session-num?          uint32
       |     |     +--ro process-num?          uint32
       |     |     +--ro interface* [interface-id]
       |     |     |  +--ro interface-id         string
       |     |     |  +--ro in-traffic-rate?     uint32
       |     |     |  +--ro out-traffic-rate?    uint32
       |     |     |  +--ro in-traffic-speed?    uint64
       |     |     |  +--ro out-traffic-speed?   uint64
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     +--:(i2nsf-system-user-activity-log)
       |     |  +--ro i2nsf-system-user-activity-log
       |     |     +--ro acquisition-method?   identityref
       |     |     +--ro emission-type?        identityref
       |     |     +--ro dampening-type?       identityref
       |     |     +--ro user                  string
       |     |     +--ro group*                string
       |     |     +--ro ip-address            inet:ip-address-no-zone
       |     |     +--ro port-number           inet:port-number
       |     |     +--ro authentication?       identityref
       |     |     +--ro message?              string
       |     |     +--ro vendor-name?          string
       |     |     +--ro nsf-name?             union
       |     |     +--ro severity?             severity
       |     |     +--ro online-duration?      uint32
       |     |     +--ro logout-duration?      uint32
       |     |     +--ro additional-info?      enumeration
       |     +--:(i2nsf-nsf-log-dpi) {i2nsf-nsf-log-dpi}?
       |        +--ro i2nsf-nsf-log-dpi
       |           +--ro attack-type?          dpi-type
       |           +--ro acquisition-method?   identityref
       |           +--ro emission-type?        identityref
       |           +--ro dampening-type?       identityref
       |           +--ro policy-name
                    -> /nsfintf:i2nsf-security-policy/name
       |           +--ro src-user?             string
       |           +--ro message?              string
       |           +--ro vendor-name?          string
       |           +--ro nsf-name?             union
       |           +--ro severity?             severity
       +---n i2nsf-nsf-event
          +--ro (sub-event-type)?
             +--:(i2nsf-nsf-detection-ddos) {i2nsf-nsf-detection-ddos}?
             |  +--ro i2nsf-nsf-detection-ddos
             |     +--ro attack-type?          identityref
             |     +--ro start-time            yang:date-and-time
             |     +--ro end-time?             yang:date-and-time
             |     +--ro attack-src-ip*        inet:ip-address-no-zone
             |     +--ro attack-dst-ip*        inet:ip-address-no-zone
             |     +--ro attack-src-port*      inet:port-number
             |     +--ro attack-dst-port*      inet:port-number
             |     +--ro rule-name
                       -> /nsfintf:i2nsf-security-policy/rules/name
             |     +--ro attack-rate?          uint32
             |     +--ro attack-speed?         uint64
             |     +--ro action*               log-action
             |     +--ro acquisition-method?   identityref
             |     +--ro emission-type?        identityref
             |     +--ro dampening-type?       identityref
             |     +--ro message?              string
             |     +--ro vendor-name?          string
             |     +--ro nsf-name?             union
             |     +--ro severity?             severity
             +--:(i2nsf-nsf-detection-virus)
                                            {i2nsf-nsf-detection-virus}?
             |  +--ro i2nsf-nsf-detection-virus
             |     +--ro dst-ip?               inet:ip-address-no-zone
             |     +--ro dst-port?             inet:port-number
             |     +--ro rule-name
                       -> /nsfintf:i2nsf-security-policy/rules/name
             |     +--ro src-ip?               inet:ip-address-no-zone
             |     +--ro src-port?             inet:port-number
             |     +--ro src-location?         string
             |     +--ro dst-location?         string
             |     +--ro virus-name?           string
             |     +--ro virus-type?           identityref
             |     +--ro host?                 union
             |     +--ro file-type?            string
             |     +--ro file-name?            string
             |     +--ro os?                   string
             |     +--ro action*               log-action
             |     +--ro acquisition-method?   identityref
             |     +--ro emission-type?        identityref
             |     +--ro dampening-type?       identityref
             |     +--ro message?              string
             |     +--ro vendor-name?          string
             |     +--ro nsf-name?             union
             |     +--ro severity?             severity
             +--:(i2nsf-nsf-detection-intrusion)
                                        {i2nsf-nsf-detection-intrusion}?
             |  +--ro i2nsf-nsf-detection-intrusion
             |     +--ro dst-ip?               inet:ip-address-no-zone
             |     +--ro dst-port?             inet:port-number
             |     +--ro rule-name
                       -> /nsfintf:i2nsf-security-policy/rules/name
             |     +--ro src-ip?               inet:ip-address-no-zone
             |     +--ro src-port?             inet:port-number
             |     +--ro src-location?         string
             |     +--ro dst-location?         string
             |     +--ro protocol?             identityref
             |     +--ro app?                  identityref
             |     +--ro attack-type?          identityref
             |     +--ro action*               log-action
             |     +--ro attack-rate?          uint32
             |     +--ro attack-speed?         uint64
             |     +--ro acquisition-method?   identityref
             |     +--ro emission-type?        identityref
             |     +--ro dampening-type?       identityref
             |     +--ro message?              string
             |     +--ro vendor-name?          string
             |     +--ro nsf-name?             union
             |     +--ro severity?             severity
             +--:(i2nsf-nsf-detection-web-attack)
                                       {i2nsf-nsf-detection-web-attack}?
             |  +--ro i2nsf-nsf-detection-web-attack
             |     +--ro dst-ip?               inet:ip-address-no-zone
             |     +--ro dst-port?             inet:port-number
             |     +--ro rule-name
                       -> /nsfintf:i2nsf-security-policy/rules/name
             |     +--ro src-ip?               inet:ip-address-no-zone
             |     +--ro src-port?             inet:port-number
             |     +--ro src-location?         string
             |     +--ro dst-location?         string
             |     +--ro attack-type?          identityref
             |     +--ro req-method?           identityref
             |     +--ro req-target?           string
             |     +--ro filtering-type*       identityref
             |     +--ro req-user-agent?       string
             |     +--ro cookie?               string
             |     +--ro req-host?             string
             |     +--ro response-code?        string
             |     +--ro acquisition-method?   identityref
             |     +--ro emission-type?        identityref
             |     +--ro dampening-type?       identityref
             |     +--ro action*               log-action
             |     +--ro message?              string
             |     +--ro vendor-name?          string
             |     +--ro nsf-name?             union
             |     +--ro severity?             severity
             +--:(i2nsf-nsf-detection-voip-volte)
                                       {i2nsf-nsf-detection-voip-volte}?
                +--ro i2nsf-nsf-detection-voip-volte
                   +--ro dst-ip?                 inet:ip-address-no-zone
                   +--ro dst-port?               inet:port-number
                   +--ro rule-name
                       -> /nsfintf:i2nsf-security-policy/rules/name
                   +--ro src-ip?                 inet:ip-address-no-zone
                   +--ro src-port?               inet:port-number
                   +--ro src-location?           string
                   +--ro dst-location?           string
                   +--ro source-voice-id*        string
                   +--ro destination-voice-id*   string
                   +--ro user-agent*             string
                   +--ro message?                string
                   +--ro vendor-name?            string
                   +--ro nsf-name?               union
                   +--ro severity?               severity

                 Figure 1: NSF Monitoring YANG Module Tree

8.  YANG Data Model of NSF Monitoring YANG Module

   This section describes a YANG module of I2NSF NSF Monitoring.  The
   data model provided in this document uses identities to be used to
   get information of the monitored of an NSF's monitoring data.  Every
   identity used in the document gives information or status about the
   current situation of an NSF.  This YANG module imports from
   [RFC6991], [RFC8343], and [I-D.ietf-i2nsf-nsf-facing-interface-dm],
   and makes references to [RFC0768][RFC0791]
   [RFC0792][RFC0793][RFC0854] [RFC1939][RFC0959][RFC4340]
   [RFC4443][RFC4960][RFC5321] [RFC5646] [RFC6242][RFC6265][RFC7230]
   [RFC7231][RFC8200] [RFC8641][RFC9051] [I-D.ietf-tcpm-rfc793bis]
   [IANA-HTTP-Status-Code] [IANA-Media-Types].

   <CODE BEGINS> file "ietf-i2nsf-nsf-monitoring@2022-01-26.yang" "ietf-i2nsf-nsf-monitoring@2022-01-28.yang"
   module ietf-i2nsf-nsf-monitoring {
     yang-version 1.1;
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring";
     prefix
       nsfmi;
     import ietf-inet-types{
       prefix inet;
       reference
         "Section 4 of RFC 6991";
     }
     import ietf-yang-types {
       prefix yang;
       reference
         "Section 3 of RFC 6991";
     }
     import ietf-i2nsf-policy-rule-for-nsf {
       prefix nsfintf;
       reference
         "Section 4.1 of draft-ietf-i2nsf-nsf-facing-interface-dm-17";
     }
     import ietf-interfaces {
       prefix if;
       reference
         "Section 5 of RFC 8343";
     }
     organization
       "IETF I2NSF (Interface to Network Security Functions)
        Working Group";
     contact
       "WG Web: <https://datatracker.ietf.org/wg/i2nsf>
        WG List: <mailto:i2nsf@ietf.org>

        Editor: Jaehoon Paul Jeong
        <mailto:pauljeong@skku.edu>

        Editor: Patrick Lingga
        <mailto:patricklink@skku.edu>";

     description
       "This module is a YANG module for I2NSF NSF Monitoring.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this
        document are to be interpreted as described in BCP 14
        (RFC 2119) (RFC 8174) when, and only when, they appear
        in all capitals, as shown here.

        Copyright (c) 2022 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.";

     revision "2022-01-26" "2022-01-28" {
       description "Latest revision";
       reference
         "RFC XXXX: I2NSF NSF Monitoring Interface YANG Data Model";

       // RFC Ed.: replace XXXX with an actual RFC number and remove
       // this note.
     }

     /*
      * Typedefs
      */

     typedef severity {
       type enumeration {
         enum critical {
           description
             "The 'critical' severity level indicates that
              an immediate corrective action is required.
              A 'critical' severity is reported when a service
              becomes totally out of service and must be restored.";
         }
         enum high {
           description
             "The 'high' severity level indicates that
              an urgent corrective action is required.
              A 'high' severity is reported when there is
              a severe degradation in the capability of the
              service and its full capability must be restored.";
         }
         enum middle {
           description
             "The 'middle' severity level indicates the
              existence of a non-service-affecting fault
              condition and corrective action should be done
              to prevent a more serious fault. The 'middle'
              severity is reported when the detected problem
              is not degrading the capability of the service, but
              some service degradation might happen if not
              prevented.";
         }
         enum low {
           description
             "The 'low' severity level indicates the detection
              of a potential fault before any effect is observed.
              The 'low' severity is reported when an action should
              be done before a fault happen.";
         }
       }
       description
         "An indicator representing severity levels. The severity
          levels starting from the highest are critical, high, middle,
          and low.";
     }

     typedef log-action {
       type enumeration {
         enum allow {
           description
             "If action is allowed";
         }
         enum alert {
           description
             "If action is alert";
         }
         enum block {
           description
             "If action is block";
         }
         enum discard {
           description
             "If action is discarded";
         }
         enum declare {
           description
             "If action is declared";
         }
         enum block-ip {
           description
             "If action is block-ip";
         }
         enum block-service{
           description
             "If action is block-service";
         }
       }
       description
         "The type representing action for logging.";
     }

     typedef dpi-type{
       type enumeration {
         enum file-blocking{
           description
             "DPI for preventing the specified file types from flowing
              in the network.";
         }
         enum data-filtering{
           description
             "DPI for preventing sensitive information (e.g., Credit
              Card Number or Social Security Numbers) leaving a
              protected network.";
         }
         enum application-behavior-control{
           description
             "DPI for filtering packet based on the application or
              network behavior analysis to identify malicious or
              unusual activity.";
         }

       }
       description
         "The type of Deep Packet Inspection (DPI).
          The defined types are file-blocking, data-filtering, and
          application-behavior-control.";
     }

     typedef operation-type{
       type enumeration {
         enum login {
           description
             "The operation type is Login.";
         }
         enum logout {
           description
             "The operation type is Logout.";
         }
         enum configuration {
           description
             "The operation type is Configuration. The configuration
              operation includes the command for writing a new
              configuration and modifying an existing configuration.";
         }
         enum other {
           description
             "The operation type is Other operation. This other
              includes all operations done by a user except login,
              logout, and configuration.";
         }
       }
       description
         "The type of operation done by a user during a session.
          The user operation is not considering their privileges.";
     }

     typedef login-role {
       type enumeration {
         enum administrator {
           description
             "Administrator (i.e., Superuser)'s login role.
              Non-restricted role.";
         }
         enum user {
           description
             "User login role. Semi-restricted role, some data and
              configurations are available but confidential or important
              data and configuration are restricted.";
         }
         enum guest {
           description
             "Guest login role. Restricted role, only few read data are
              available and write configurations are restricted.";
         }
       }
       description
         "The privilege level of the user account.";
     }

     /*
      * Identity
      */

     identity characteristics {
       description
         "Base identity for monitoring information
          characteristics";
     }
     identity acquisition-method {
       base characteristics;
       description
         "The type of acquisition-method. It can be multiple
          types at once.";
     }
     identity subscription {
       base acquisition-method;
       description
         "The acquisition-method type is subscription.";
     }
     identity query {
       base acquisition-method;
       description
         "The acquisition-method type is query.";
     }
     identity emission-type {
       base characteristics;
       description
         "The type of emission-type.";
     }
     identity periodic {
       base emission-type;
       description
         "The emission-type type is periodic.";
     }
     identity on-change {
       base emission-type;
       description
         "The emission-type type is on-change.";
     }
     identity on-request {
       base emission-type;
       description
         "The emission-type type is on-request.";
     }
     identity dampening-type {
       base characteristics;
       description
         "The type of message dampening to stop the rapid transmission
          of messages. The dampening types are on-repetition and
          no-dampening";
     }
     identity no-dampening {
       base dampening-type;
       description
         "The dampening-type is no-dampening. No-dampening type does
          not limit the transmission for the messages of the same
          type.";
     }
     identity on-repetition {
       base dampening-type;
       description
         "The dampening-type is on-repetition. On-repetition type limits
          the transmitted on-change message to one message at a certain
          interval.";
     }

     identity authentication-mode {
       description
         "The authentication mode for a user to connect to the NSF,
          e.g., pre-configured-key and certificate-authority";
     }
     identity pre-configured-key {
       base authentication-mode;
       description
         "The pre-configured-key is an authentication using a key
          authentication.";
     }
     identity certificate-authority {
       base authentication-mode;
       description
         "The certificate-authority (CA) is an authentication using a
          digital certificate.";
     }

     identity event {
       description
         "Base identity for I2NSF events.";
     }

     identity system-event {
       base event;
       description
         "Identity for system event";
     }

     identity system-alarm {
       base event;
       description
         "Base identity for detectable system alarm types";
     }

     identity memory-alarm {
       base system-alarm;
       description
         "A memory alarm is alerted.";
     }
     identity cpu-alarm {
       base system-alarm;
       description
         "A CPU alarm is alerted.";
     }
     identity disk-alarm {
       base system-alarm;
       description
         "A disk alarm is alerted.";
     }
     identity hardware-alarm {
       base system-alarm;
       description
         "A hardware alarm (i.e., hardware failure) is alerted.";
     }
     identity interface-alarm {
       base system-alarm;
       description
         "An interface alarm is alerted.";
     }

     identity access-violation {
       base system-event;
       description
         "The access-violation system event is an event when a user
          tries to access (read, write, create, or delete) any
          information or execute commands above their privilege.";

     }
     identity configuration-change {
       base system-event;
       description
         "The configuration-change system event is an event when a user
          adds a new configuration or modify an existing configuration
          (write configuration).";
     }

     identity attack-type {
       description
         "The root ID of attack-based notification
          in the notification taxonomy";
     }
     identity nsf-attack-type {
       base attack-type;
       description
         "This ID is intended to be used
          in the context of NSF event.";
     }

     identity virus-type {
       base nsf-attack-type;
       description
         "The type of virus. It can be multiple types at once.
          This attack type is associated with a detected
          system-log virus-attack.";
     }
     identity trojan {
       base virus-type;
       description
         "The virus type is a trojan. Trojan is able to disguise the
          intent of the files or programs to misleads the users.";
     }
     identity worm {
       base virus-type;
       description
         "The virus type is a worm. Worm can self-replicate and
          spread through the network automatically.";
     }
     identity macro {
       base virus-type;
       description
         "The virus type is a macro virus. Macro causes a series of
          threats automatically after the program is executed.";
     }
     identity boot-sector {
       base virus-type;
       description
         "The virus type is a boot sector virus. Boot sector is a virus
          that infects the core of the computer, affecting the startup
          process.";
     }
     identity polymorphic {
       base virus-type;
       description
         "The virus type is a polymorphic virus. Polymorphic can
          modify its version when it replicates, making it hard to
          detect.";
     }
     identity overwrite {
       base virus-type;
       description
         "The virus type is an overwrite virus. Overwrite can remove
          existing software and replace it with malicious code by
          overwriting it.";
     }
     identity resident {
       base virus-type;
       description
         "The virus-type is a resident virus. Resident saves itself in
          the computer's memory and infects other files and software.";
     }
     identity non-resident {
       base virus-type;
       description
         "The virus-type is a non-resident virus. Non-resident attaches
          directly to an executable file and enters the device when
          executed.";
     }
     identity multipartite {
       base virus-type;
       description
         "The virus-type is a multipartite virus. Multipartite attacks
          both the boot sector and executables files of a computer.";
     }
     identity spacefiller {
       base virus-type;
       description
         "The virus-type is a spacefiller virus. Spacefiller fills empty
          spaces of a file or software with malicious code.";
     }

     identity intrusion-attack-type {
       base nsf-attack-type;
       description
         "The attack type is associated with a detected
          system-log intrusion.";
     }
     identity brute-force {
       base intrusion-attack-type;
       description
         "The intrusion type is brute-force.";
     }
     identity buffer-overflow {
       base intrusion-attack-type;
       description
         "The intrusion type is buffer-overflow.";
     }
     identity web-attack-type {
       base nsf-attack-type;
       description
         "The attack type is associated with a detected
          system-log web-attack.";
     }
     identity command-injection {
       base web-attack-type;
       description
         "The detected web attack type is command injection.";
     }
     identity xss {
       base web-attack-type;
       description
         "The detected web attack type is Cross Site Scripting (XSS).";
     }
     identity csrf {
       base web-attack-type;
       description
         "The detected web attack type is Cross Site Request Forgery.";
     }

     identity ddos-type {
       base nsf-attack-type;
       description
         "Base identity for detectable flood types";
     }
     identity syn-flood {
       base ddos-type;
       description
         "A SYN flood is detected.";
     }
     identity ack-flood {
       base ddos-type;
       description
         "An ACK flood is detected.";
     }
     identity syn-ack-flood {
       base ddos-type;
       description
         "A SYN-ACK flood is detected.";
     }
     identity fin-rst-flood {
       base ddos-type;
       description
         "A FIN-RST flood is detected.";
     }
     identity tcp-con-flood {
       base ddos-type;
       description
         "A TCP connection flood is detected.";
     }
     identity udp-flood {
       base ddos-type;
       description
         "A UDP flood is detected.";
     }
     identity icmpv4-flood {
       base ddos-type;
       description
         "An ICMPv4 flood is detected.";
     }
     identity icmpv6-flood {
       base ddos-type;
       description
         "An ICMPv6 flood is detected.";
     }
     identity http-flood {
       base ddos-type;
       description
         "An HTTP flood is detected.";
     }
     identity https-flood {
       base ddos-type;
       description
         "An HTTPS flood is detected.";
     }
     identity dns-query-flood {
       base ddos-type;
       description
         "A Domain Name System (DNS) query flood is detected.";
     }
     identity dns-reply-flood {
       base ddos-type;
       description
        "A Domain Name System (DNS) reply flood is detected.";
     }
     identity sip-flood {
       base ddos-type;
       description
         "A Session Initiation Protocol (SIP) flood is detected.";
     }
     identity ssl-flood {
       base ddos-type;
       description
         "An Secure Sockets Layer (SSL) flood is detected";
     }
     identity ntp-amp-flood {
       base ddos-type;
       description
         "A Network Time Protocol (NTP) amplification is detected";
     }

     identity req-method {
       description
         "A set of request types in HTTP (if applicable).";
     }
     identity put {
       base req-method;
       description
         "The detected request type is PUT.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method PUT";
     }
     identity post {
       base req-method;
       description
         "The detected request type is POST.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method POST";
     }
     identity get {
       base req-method;
       description
         "The detected request type is GET.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method GET";
     }
     identity head {
       base req-method;
       description
         "The detected request type is HEAD.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method HEAD";
     }
     identity delete {
       base req-method;
       description
         "The detected request type is DELETE.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method DELETE";
     }
     identity connect {
       base req-method;
       description
         "The detected request type is CONNECT.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method CONNECT";
     }
     identity options {
       base req-method;
       description
         "The detected request type is OPTIONS.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method OPTIONS";
     }
     identity trace {
       base req-method;
       description
         "The detected request type is TRACE.";
       reference
         "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content - Request Method TRACE";
     }

     identity filter-type {
       description
         "The type of filter used to detect an attack,
          for example, a web-attack.  It can be applicable to
          more than web-attacks.";
     }
     identity allow-list {
       base filter-type;
       description
         "The applied filter type is an allow list. This filter blocks
          all connection except the specified list.";
     }
     identity deny-list {
       base filter-type;
       description
         "The applied filter type is a deny list. This filter opens all
          connection except the specified list.";
     }
     identity unknown-filter {
       base filter-type;
       description
         "The applied filter is unknown.";
     }

     identity protocol {
       description
         "An identity used to enable type choices in leaves
          and leaflists with respect to protocol metadata. This is used
          to identify the type of protocol that goes through the NSF.";
     }
     identity ip {
       base protocol;
       description
         "General IP protocol type.";
       reference
         "RFC 791: Internet Protocol
          RFC 8200: Internet Protocol, Version 6 (IPv6)";
     }
     identity ipv4 {
       base ip;
       description
         "IPv4 protocol type.";
       reference
         "RFC 791: Internet Protocol";
     }
     identity ipv6 {
       base ip;
       description
         "IPv6 protocol type.";
       reference
         "RFC 8200: Internet Protocol, Version 6 (IPv6)";
     }
     identity icmp {
       base protocol;
       description
         "Base identity for ICMPv4 and ICMPv6 condition capability";
       reference
         "RFC 792: Internet Control Message Protocol
          RFC 4443: Internet Control Message Protocol (ICMPv6)
          for the Internet Protocol Version 6 (IPv6) Specification
          - ICMPv6";
     }
     identity icmpv4 {
       base icmp;
       description
         "ICMPv4 protocol type.";
       reference
         "RFC 791: Internet Protocol
          RFC 792: Internet Control Message Protocol";
     }
     identity icmpv6 {
       base icmp;
       description
         "ICMPv6 protocol type.";
       reference
         "RFC 8200: Internet Protocol, Version 6 (IPv6)
          RFC 4443: Internet Control Message Protocol (ICMPv6)
          for the Internet Protocol Version 6 (IPv6)
          Specification";
     }
     identity transport-protocol {
       base protocol;
       description
         "Base identity for Layer 4 protocol condition capabilities,
          e.g., TCP, UDP, SCTP, DCCP, and ICMP";
     }
     identity tcp {
       base transport-protocol;
       description
         "TCP protocol type.";
       reference
         "RFC 793: Transmission Control Protocol
          draft-ietf-tcpm-rfc793bis-25: Transmission Control Protocol
          (TCP) Specification";
     }
     identity udp {
       base transport-protocol;
       description
         "UDP protocol type.";
       reference
         "RFC 768: User Datagram Protocol";
     }
     identity sctp {
       base transport-protocol;
       description
         "Identity for SCTP condition capabilities";
       reference
         "RFC 4960: Stream Control Transmission Protocol";
     }
     identity dccp {
       base transport-protocol;
       description
         "Identity for DCCP condition capabilities";
       reference
         "RFC 4340: Datagram Congestion Control Protocol";
     }
     identity application-protocol {
       base protocol;
       description
         "Base identity for Application protocol, e.g., HTTP, FTP";
     }
     identity http {
       base application-protocol;
       description
         "HTTP protocol type.";
       reference
         "RFC7230: Hypertext Transfer Protocol (HTTP/1.1): Message
          Syntax and Routing
          RFC7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content";
     }
     identity https {
       base application-protocol;
       description
         "HTTPS protocol type.";
       reference
         "RFC7230: Hypertext Transfer Protocol (HTTP/1.1): Message
          Syntax and Routing
          RFC7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics
          and Content";
     }
     identity ftp {
       base application-protocol;
       description
         "FTP protocol type.";
       reference
         "RFC 959: File Transfer Protocol";
     }
     identity ssh {
       base application-protocol;
       description
         "SSH protocol type.";
       reference
         "RFC 6242: Using the NETCONF Protocol over Secure Shell (SSH)";
     }
     identity telnet {
       base application-protocol;
       description
         "The identity for telnet.";
       reference
         "RFC 854: Telnet Protocol";
     }
     identity smtp {
       base application-protocol;
       description
         "The identity for smtp.";
       reference
         "RFC 5321: Simple Mail Transfer Protocol (SMTP)";
     }
     identity pop3 {
       base application-protocol;
       description
         "The identity for pop3. This includes POP3 over TLS";
       reference
         "RFC 1939: Post Office Protocol - Version 3 (POP3)";
     }
     identity imap {
       base application-protocol;
       description
         "The identity for Internet Message Access Protocol. This
          includes IMAP over TLS";
       reference
         "RFC 9051: Internet Message Access Protocol (IMAP) - Version
          4rev2";
     }

     /*
      * Grouping
      */

     grouping timestamp {
       description
         "Grouping for identifying the time of the message.";
       leaf timestamp {
         type yang:date-and-time;
         description
           "Specify the time of a message being delivered.";
       }
     }
     grouping common-monitoring-data {
       description
         "A set of common monitoring data that is needed
         as the basic information.";
       leaf message {
         type string;
         description
           "This is a freetext annotation for
            monitoring a notification's content.";
       }
       leaf vendor-name {
         type string;
         description
           "The name of the NSF vendor. The string is unrestricted to
            identify the provider or vendor of the NSF.";
       }
       leaf nsf-name {
         type union {
           type string;
           type inet:ip-address-no-zone;
         }
         description
           "The name or IP address of the NSF generating the message.
            If the given nsf-name is not IP address, the name can be an
            arbitrary string including FQDN (Fully Qualified Domain
            Name). The name MUST be unique in the scope of management
            domain for a different NSF to identify the NSF that
            generates the message.";
       }
       leaf severity {
         type severity;
         description
           "The severity of the alarm such as critical, high,
            middle, and low.";
       }
     }
     grouping characteristics {
       description
         "A set of characteristics of a notification.";
       leaf acquisition-method {
         type identityref {
           base acquisition-method;
         }
         description
           "The acquisition-method for characteristics";
       }
       leaf emission-type {
         type identityref {
           base emission-type;
         }
        description
           "The emission-type for characteristics";
       }
       leaf dampening-type {
         type identityref {
           base dampening-type;
         }
         description
           "The dampening-type for characteristics";
       }
     }
     grouping i2nsf-system-alarm-type-content {
       description
         "A set of contents for alarm type notification.";
       leaf usage {
         type uint8 {
           range "0..100";
         }
         units "percent";
         description
           "Specifies the used percentage";
       }
       leaf threshold {
         type uint8 {
           range "0..100";
         }
         units "percent";
         description
           "The threshold percentage triggering the alarm or
            the event";
       }
     }
     grouping i2nsf-system-event-type-content {
       description
         "System event metadata associated with system events
          caused by user activity. This can be extended to provide
          additional information.";
       leaf user {
         type string;
         mandatory true;
         description
           "The name of a user";
       }
       leaf-list group {
         type string;
         min-elements 1;
         description
           "The group(s) to which a user belongs.";
       }
       leaf ip-address {
         type inet:ip-address-no-zone;
         mandatory true;
         description
           "The IPv4 (or IPv6) address of a user that trigger the
            event.";
       }
       leaf port-number {
         type inet:port-number;
         mandatory true;
         description
           "The port number used by the user.";
       }
       leaf authentication {
         type identityref {
           base authentication-mode;
         }
         description
           "The authentication-mode of a user.";
       }
     }
     grouping i2nsf-nsf-event-type-content {
       description
         "A set of common IPv4 (or IPv6)-related NSF event
          content elements";
       leaf dst-ip {
         type inet:ip-address-no-zone;
         description
           "The destination IPv4 (IPv6) address of the packet";
       }
       leaf dst-port {
         type inet:port-number;
         description
           "The destination port of the packet";
       }
       leaf rule-name {
         type leafref {
           path
             "/nsfintf:i2nsf-security-policy"
            +"/nsfintf:rules/nsfintf:name";
         }
         mandatory true;
         description
           "The name of the I2NSF Policy Rule being triggered";
       }

     }
     grouping i2nsf-nsf-event-type-content-extend {
       description
         "A set of extended common IPv4 (or IPv6)-related NSF
          event content elements";
       uses i2nsf-nsf-event-type-content;
       leaf src-ip {
         type inet:ip-address-no-zone;
         description
           "The source IPv4 (or IPv6) address of the packet or flow";
       }
       leaf src-port {
         type inet:port-number;
         description
           "The source port of the packet or flow";
       }
       leaf src-location {
         type string {
           length "1..100";
           pattern "[0-9a-zA-Z ]*";
         }
         description
           "The source geographical location (e.g., country and city)
            of the src-ip field.";
       }
       leaf dst-location {
         type string {
           length "1..100";
           pattern "[0-9a-zA-Z ]*";
         }
         description
           "The destination geographical location (e.g., country and
            city) of the dst-ip field.";
       }
     }
     grouping log-action {
       description
         "A grouping for logging action.";
       leaf-list action {
         type log-action;
         description
           "Action type: allow, alert, block, discard, declare,
            block-ip, block-service";
       }
     }
     grouping attack-rates {
       description
         "A set of traffic rates for monitoring attack traffic
          data";
       leaf attack-rate {
         type uint32;
         units "pps";
         description
           "The average packets per second (pps) rate of attack
            traffic";
       }
       leaf attack-speed {
         type uint64;
         units "Bps";
         description
           "The average bytes per second (Bps) speed of attack traffic";
       }
     }
     grouping traffic-rates {
       description
         "A set of traffic rates for statistics data";
       leaf discontinuity-time {
         type yang:date-and-time;
         mandatory true;
         description
           "The time on the most recent occasion at which any one or
            more of the counters suffered a discontinuity.
            If no such discontinuities have occurred since the last
            re-initialization of the local management subsystem, then
            this node contains the time the local management subsystem
            was re-initialized.";
       }
       leaf total-traffic {
         type yang:counter64;
         units "packets";
         description
           "The total number of traffic packets (in and out) in the
            NSF.";
       }
       leaf in-traffic-average-rate {
         type uint32;
         units "pps";
         description
           "Inbound traffic average rate in packets per second (pps).
            The average is calculated from the start of the NSF service
            until the generation of this record.";
       }
       leaf in-traffic-peak-rate {
         type uint32;
         units "pps";
         description
           "Inbound traffic peak rate in packets per second (pps).";
       }
       leaf in-traffic-average-speed {
         type uint64;
         units "Bps";
         description
           "Inbound traffic average speed in bytes per second (Bps).
            The average is calculated from the start of the NSF service
            until the generation of this record.";
       }
       leaf in-traffic-peak-speed {
         type uint64;
         units "Bps";
         description
           "Inbound traffic peak speed in bytes per second (Bps).";
       }
       leaf out-traffic-average-rate {
         type uint32;
         units "pps";
         description
           "Outbound traffic average rate in packets per second (pps).
            The average is calculated from the start of the NSF service
            until the generation of this record.";
       }
       leaf out-traffic-peak-rate {
         type uint32;
         units "pps";
         description
          "Outbound traffic peak rate in packets per second (pps).";
       }
       leaf out-traffic-average-speed {
         type uint64;
         units "Bps";
         description
           "Outbound traffic average speed in bytes per second (Bps).
            The average is calculated from the start of the NSF service
            until the generation of this record.";
       }
       leaf out-traffic-peak-speed {
         type uint64;
         units "Bps";
         description
           "Outbound traffic peak speed in bytes per second (Bps).";
       }
     }
     grouping i2nsf-system-counter-type-content{
       description
         "A set of counters for an interface traffic data.";

       leaf interface-name {
         type if:interface-ref;
         description
           "Network interface name configured in an NSF";
         reference
           "RFC 8343: A YANG Data Model for Interface Management";
       }
       leaf in-total-traffic-pkts {
         type yang:counter64;
         description
           "Total inbound packets";
       }
       leaf out-total-traffic-pkts {
         type yang:counter64;
         description
           "Total outbound packets";
       }
       leaf in-total-traffic-bytes {
         type uint64;
         units "bytes";
         description
           "Total inbound bytes";
       }
       leaf out-total-traffic-bytes {
         type uint64;
         units "bytes";
         description
           "Total outbound bytes";
       }
       leaf in-drop-traffic-pkts {
         type yang:counter64;
         description
           "Total inbound drop packets";
       }
       leaf out-drop-traffic-pkts {
         type yang:counter64;
         description
           "Total outbound drop packets";
       }
       leaf in-drop-traffic-bytes {
         type uint64;
         units "bytes";
         description
           "Total inbound drop bytes";
       }
       leaf out-drop-traffic-bytes {
         type uint64;
         units "bytes";
         description
           "Total outbound drop bytes";
       }
       uses traffic-rates;
     }

     grouping i2nsf-nsf-counters-type-content{
       description
         "A set of contents of a policy in an NSF.";
       leaf policy-name {
         type leafref {
           path
             "/nsfintf:i2nsf-security-policy"
            +"/nsfintf:name";
         }
         mandatory true;
         description
           "The name of the policy being triggered";
       }
       leaf src-user{
         type string;
         description
           "The I2NSF User's name who generates the policy.";
       }
     }

     grouping enable-notification {
       description
         "A grouping for enabling or disabling notification";
       leaf enabled {
         type boolean;
         default "true";
         description
           "Enables or Disables the notification.
            If 'true', then the notification is enabled.
            If 'false, then the notification is disabled.";
       }
     }

     grouping dampening {
       description
         "A grouping for dampening period of notification.";
       leaf dampening-period {
         type uint32;
         units "centiseconds";
         default "0";
         description
           "Specifies the minimum interval between the assembly of
            successive update records for a single receiver of a
            subscription. Whenever subscribed objects change and
            a dampening-period interval (which may be zero) has
            elapsed since the previous update record creation for
            a receiver, any subscribed objects and properties
            that have changed since the previous update record
            will have their current values marshalled and placed
            in a new update record. But if the subscribed objects change
            when the dampening-period is active, it should update the
            record without sending the notification until the dampening-
            period is finished. If multiple changes happen during the
            active dampening-period, it should update the record with
            the latest data. And at the end of the dampening-period, it
            should send the record as a notification with the latest
            updated record and restart the countdown.";
         reference
           "RFC 8641:  Subscription to YANG Notifications for
            Datastore Updates - Section 5.";
       }
     }

     /*
      * Feature Nodes
      */

     feature i2nsf-nsf-detection-ddos {
       description
         "This feature means it supports I2NSF nsf-detection-ddos
          notification";
     }
     feature i2nsf-nsf-detection-virus {
       description
         "This feature means it supports I2NSF nsf-detection-virus
          notification";
     }
     feature i2nsf-nsf-detection-intrusion {
       description
         "This feature means it supports I2NSF nsf-detection-intrusion
          notification";
     }
     feature i2nsf-nsf-detection-web-attack {
       description
         "This feature means it supports I2NSF nsf-detection-web-attack
          notification";
     }
     feature i2nsf-nsf-detection-voip-volte {
       description
         "This feature means it supports I2NSF nsf-detection-voip-volte
          notification";
     }
     feature i2nsf-nsf-log-dpi {
       description
         "This feature means it supports I2NSF nsf-log-dpi
          notification";
     }

     /*
      * Notification nodes
      */

     notification i2nsf-event {
       description
         "Notification for I2NSF Event.";

       leaf language {
         type string {
           pattern
              "^((en-GB-oed|i-ami|i-bnn|i-default|"
            + "i-enochian|i-hak|i-klingon|i-lux|i-mingo|i-navajo|i-pwn|"
            + "i-tao|i-tay|i-tsu|sgn-BE-FR|sgn-BE-NL|sgn-CH-DE)|"
            + "(art-lojban|cel-gaulish|no-bok|no-nyn|zh-guoyu|zh-hakka|"
            + "zh-min|zh-min-nan|zh-xiang)|"
            + "(([A-Za-z]{2,3}(-[A-Za-z]{3}(-[A-Za-z]{3}){0,2})?)|"
            + "[A-Za-z]{4}|[A-Za-z]{5,8}"
            + "(-[A-Za-z]{4})?"
            + "(-[A-Za-z]{2}|[0-9]{3})?"
            + "(-[A-Za-z0-9]{5,8}|[0-9][A-Za-z0-9]{3})*"
            + "(-[0-9A-WY-Za-wy-z](-[A-Za-z0-9]{2,8})+)*"
            + "(-x(-[A-Za-z0-9]{1,8})+)?)|"
            + "x(-[A-Za-z0-9]{1,8})+)$";
         }
         description
           "The value in this field describes the human language
            intended for the user, so that it allows a user to
            differentiate the language that is used in the
            notification. This field is not mandatory, but required
            when the implementation provides more than one human
            language for the human-readable string fields,
            e.g., /i2nsf-nsf-event/i2nsf-nsf-detection-ddos/message.

            This field uses the language-tag production in Section 2.1
            in RFC 5646. See the document for more details.";
         reference
           "RFC 5646: Tags for Identifying Languages";
       }
       choice sub-event-type {
         description
           "This choice must be augmented with cases for each allowed
            sub-event. Only 1 sub-event will be instantiated in each
            i2nsf-event message. Each case is expected to define one
            container with all the sub-event fields.";
         case i2nsf-system-detection-alarm {
           container i2nsf-system-detection-alarm{
             description
               "This notification is sent, when a system alarm
                is detected.";
             leaf alarm-category {
               type identityref {
                base system-alarm;
               }
               description
                 "The alarm category for
                  system-detection-alarm notification";
             }
             leaf component-name {
               type string;
               description
                 "The hardware component responsible for generating
                  the message. Applicable for Hardware Failure
                  Alarm.";
             }
             leaf interface-name {
               type if:interface-ref;
               description
                 "The interface name responsible for generating
                  the message. Applicable for Network Interface
                  Failure Alarm.";
               reference
                 "RFC 8343: A YANG Data Model for Interface Management";
             }
             leaf interface-state {
               type enumeration {
                 enum down {
                   description
                     "The interface state is down.";
                 }
                 enum up {
                   description
                     "The interface state is up and not congested.";
                 }
                 enum congested {
                   description
                     "The interface state is up but congested.";

                 }
               }
               description
                 "The state of the interface (i.e., up, down,
                  congested). Applicable for Network Interface Failure
                  Alarm.";
             }
             uses characteristics;
             uses i2nsf-system-alarm-type-content;
             uses common-monitoring-data;
           }
         }

         case i2nsf-system-detection-event {
           container i2nsf-system-detection-event {
             description
               "This notification is sent when a security-sensitive
                authentication action fails.";
             leaf event-category {
               type identityref {
                 base system-event;
               }
               description
                 "The event category for system-detection-event";
             }
             uses characteristics;
             uses i2nsf-system-event-type-content;
             uses common-monitoring-data;
             list changes {
               key policy-name;
               description
                 "Describes the modification that was made to the
                  configuration. The minimum information that must be
                  provided is the name of the policy that has been
                  altered (added, modified, or removed).

                  This list can be extended with the detailed
                  information about the specific changes made to the
                  configuration based on the implementation.";

               leaf policy-name {
                 type leafref {
                   path
                     "/nsfintf:i2nsf-security-policy"
                    +"/nsfintf:name";
                 }
                 description
                   "The name of the policy configuration that has been
                    added, modified, or removed.";
               }
             }
           }
         }

         case i2nsf-traffic-flows {
           container i2nsf-traffic-flows {
             description
               "This notification is sent to inform about the traffic
                flows.";
             leaf src-ip {
               type inet:ip-address-no-zone;
               description
                 "The source IPv4 (or IPv6) address of the flow";
             }
             leaf dst-ip {
               type inet:ip-address-no-zone;
               description
                 "The destination IPv4 (or IPv6) address of the flow";
             }
             leaf protocol {
               type identityref {
                 base protocol;
               }
               description
                 "The protocol type for nsf-detection-intrusion
                  notification";
             }
             leaf src-port {
               type inet:port-number;
               description
                 "The source port of the flow";
             }
             leaf dst-port {
               type inet:port-number;
               description
                 "The destination port of the flow";
             }
             leaf arrival-rate {
               type uint32;
               units "pps";
               description
                 "The average arrival rate of the flow in packets per
                  second. The average is calculated from the start of
                  the NSF service until the generation of this
                  record.";
             }
             leaf arrival-speed {
               type uint32;
               units "Bps";
               description
                 "The average arrival rate of the flow in bytes per
                  second. The average is calculated from the start of
                  the NSF service until the generation of this
                  record.";
             }
             uses characteristics;
             uses common-monitoring-data;
           }
         }

         case i2nsf-nsf-detection-session-table {
           container i2nsf-nsf-detection-session-table {
             description
               "This notification is sent, when a session table
                event is detected.";
             leaf current-session {
               type uint32;
               description
                 "The number of concurrent sessions";
             }
             leaf maximum-session {
               type uint32;
               description
                 "The maximum number of sessions that the session
                  table can support";
             }
             leaf threshold {
               type uint32;
               description
                 "The threshold triggering the event";
             }
             uses common-monitoring-data;
           }
         }
       }
     }

     notification i2nsf-log {
       description
         "Notification for I2NSF log. The notification is generated
          from the logs of the NSF.";

       leaf language {
         type string {
           pattern
              "^((en-GB-oed|i-ami|i-bnn|i-default|"
            + "i-enochian|i-hak|i-klingon|i-lux|i-mingo|i-navajo|i-pwn|"
            + "i-tao|i-tay|i-tsu|sgn-BE-FR|sgn-BE-NL|sgn-CH-DE)|"
            + "(art-lojban|cel-gaulish|no-bok|no-nyn|zh-guoyu|zh-hakka|"
            + "zh-min|zh-min-nan|zh-xiang)|"
            + "(([A-Za-z]{2,3}(-[A-Za-z]{3}(-[A-Za-z]{3}){0,2})?)|"
            + "[A-Za-z]{4}|[A-Za-z]{5,8}"
            + "(-[A-Za-z]{4})?"
            + "(-[A-Za-z]{2}|[0-9]{3})?"
            + "(-[A-Za-z0-9]{5,8}|[0-9][A-Za-z0-9]{3})*"
            + "(-[0-9A-WY-Za-wy-z](-[A-Za-z0-9]{2,8})+)*"
            + "(-x(-[A-Za-z0-9]{1,8})+)?)|"
            + "x(-[A-Za-z0-9]{1,8})+)$";
         }
         description
           "The value in this field describes the human language
            intended for the user, so that it allows a user to
            differentiate the language that is used in the
            notification. This field is not mandatory, but required
            when the implementation provides more than one human
            language for the human-readable string fields,
            e.g., /i2nsf-nsf-log/i2nsf-system-res-util-log/message.

            This field uses the language-tag production in Section 2.1
            in RFC 5646. See the document for more details.";
         reference
           "RFC 5646: Tags for Identifying Languages";
       }

       choice sub-logs-type {
         description
           "This choice must be augmented with cases for each allowed
            sub-logs. Only 1 sub-event will be instantiated in each
            i2nsf-logs message. Each case is expected to define one
            container with all the sub-logs fields.";
         case i2nsf-nsf-system-access-log {
           container i2nsf-nsf-system-access-log {
             description
               "The notification is sent, if there is a new system
                log entry about a system access event.";
             uses i2nsf-system-event-type-content;
             leaf operation-type {
               type operation-type;
               description
                 "The operation type that the user executes";
             }
             leaf input {
               type string;
               description
                 "The operation performed by a user after login. The
                  operation is a command given by a user.";
             }
             leaf output {
               type string;
               description
                 "The result in text format after executing the
                  input.";
             }
             uses characteristics;
             uses common-monitoring-data;
           }
         }

         case i2nsf-system-res-util-log {
           container i2nsf-system-res-util-log {
             description
               "This notification is sent, if there is a new log
                entry representing resource utilization updates.";
             leaf system-status {
               type enumeration {
                 enum running {
                   description
                     "The system is active and running the security
                      service.";
                 }
                 enum waiting {
                   description
                     "The system is active but waiting for an event to
                      provide the security service.";
                 }
                 enum inactive {
                   description
                     "The system is inactive and not running the
                      security service.";
                 }
               }
               description
                 "The current system's running status";
             }
             leaf cpu-usage {
               type uint8;
               units "percent";
               description
                 "Specifies the relative percentage of CPU utilization
                  with respect to platform resources";

             }
             leaf memory-usage {
               type uint8;
               units "percent";
               description
                 "Specifies the percentage of memory usage.";
             }
             list disk {
               key disk-id;
               description
                 "Disk is the hardware to store information for a
                  long period, i.e., Hard Disk or Solid-State Drive.";
               leaf disk-id {
                 type string;
                 description
                   "The ID of the storage disk. It is a free form
                    identifier to identify the storage disk.";
               }
               leaf disk-usage {
                 type uint8;
                 units "percent";
                 description
                   "Specifies the percentage of disk usage";
               }
               leaf disk-left {
                 type uint8;
                 units "percent";
                 description
                   "Specifies the percentage of disk left";
               }
             }
             leaf session-num {
               type uint32;
               description
                 "The total number of sessions";
             }
             leaf process-num {
               type uint32;
               description
                 "The total number of processes";
             }
             list interface {
               key interface-id;
               description
                 "The network interface for connecting a device
                  with the network.";
               leaf interface-id {
                 type string;
                 description
                   "The ID of the network interface. It is a free form
                    identifier to identify the network interface.";
               }
               leaf in-traffic-rate {
                 type uint32;
                 units "pps";
                 description
                   "The total inbound traffic rate in packets per
                    second";
               }
               leaf out-traffic-rate {
                 type uint32;
                 units "pps";
                 description
                    "The total outbound traffic rate in packets per
                     second";
               }
               leaf in-traffic-speed {
                 type uint64;
                 units "Bps";
                 description
                   "The total inbound traffic speed in bytes per
                    second";
               }
               leaf out-traffic-speed {
                 type uint64;
                 units "Bps";
                 description
                   "The total outbound traffic speed in bytes per
                    second";
               }
             }
             uses characteristics;
             uses common-monitoring-data;
           }
         }

         case i2nsf-system-user-activity-log {
           container i2nsf-system-user-activity-log {
             description
               "This notification is sent, if there is a new user
                activity log entry.";
             uses characteristics;
             uses i2nsf-system-event-type-content;
             uses common-monitoring-data;
             leaf online-duration {
               type uint32;
               units "seconds";
               description
                 "The duration of a user's activeness (stays in login)
                  during a session.";

             }
             leaf logout-duration {
               type uint32;
               units "seconds";
               description
                 "The duration of a user's inactiveness (not in login)
                  from the last session.";
             }
             leaf additional-info {
               type enumeration {
                 enum successful-login {
                   description
                     "The user has succeeded in login.";
                 }
                 enum failed-login {
                   description
                     "The user has failed in login (e.g., wrong
                      password)";
                 }
                 enum logout {
                   description
                     "The user has succeeded in logout";
                 }
                 enum successful-password-changed {
                   description
                     "The password has been changed successfully";
                 }
                 enum failed-password-changed{
                   description
                     "The attempt to change password has failed";
                 }
                 enum lock {
                   description
                     "The user has been locked. A locked user cannot
                      login.";
                 }
                 enum unlock {
                   description
                     "The user has been unlocked.";
                 }
               }
               description
                 "User activities, e.g., Successful User Login,
                  Failed Login attempts, User Logout, Successful User
                  Password Change, Failed User Password Change, User
                  Lockout, User Unlocking, and Unknown.";
             }
           }
         }
         case i2nsf-nsf-log-dpi {
           if-feature "i2nsf-nsf-log-dpi";
           container i2nsf-nsf-log-dpi {
             description
               "This notification is sent, if there is a new DPI
                event in the NSF log.";
             leaf attack-type {
               type dpi-type;
               description
                 "The type of the DPI";
             }
             uses characteristics;
             uses i2nsf-nsf-counters-type-content;
             uses common-monitoring-data;
           }
         }
       }
     }

     notification i2nsf-nsf-event {
       description
         "Notification for I2NSF NSF Event. This notification is
          used for a specific NSF that supported such feature.";
       choice sub-event-type {
         description
         "This choice must be augmented with cases for each allowed
          sub-event. Only 1 sub-event will be instantiated in each
          i2nsf-event message. Each case is expected to define one
          container with all the sub-event fields.";
         case i2nsf-nsf-detection-ddos {
           if-feature "i2nsf-nsf-detection-ddos";
           container i2nsf-nsf-detection-ddos {
             description
               "This notification is sent, when a specific flood type
                is detected.";
             leaf attack-type {
               type identityref {
                 base ddos-type;
               }
               description
                 "Any one of Syn flood, ACK flood, SYN-ACK flood,
                  FIN/RST flood, TCP Connection flood, UDP flood,
                  ICMP (i.e., ICMPv4 or ICMPv6) flood, HTTP flood,
                  HTTPS flood, DNS query flood, DNS reply flood, SIP
                  flood, etc.";
             }
             leaf start-time {
               type yang:date-and-time;
               mandatory true;
               description
                 "The time stamp indicating when the attack started";
             }
             leaf end-time {
               type yang:date-and-time;
               description
                 "The time stamp indicating when the attack ended. If
                  the attack is still undergoing when sending out the
                  notification, this field can be empty.";
             }
             leaf-list attack-src-ip {
               type inet:ip-address-no-zone;
               description
                 "The source IPv4 (or IPv6) addresses of attack
                  traffic. It can hold multiple IPv4 (or IPv6)
                  addresses.";
             }
             leaf-list attack-dst-ip {
               type inet:ip-address-no-zone;
               description
                 "The destination IPv4 (or IPv6) addresses of attack
                  traffic. It can hold multiple IPv4 (or IPv6)
                  addresses.";
             }
             leaf-list attack-src-port {
               type inet:port-number;
               description
                 "The source ports of the DDoS attack";
             }
             leaf-list attack-dst-port {
               type inet:port-number;
               description
                 "The destination ports of the DDoS attack";
             }
             leaf rule-name {
               type leafref {
                 path
                   "/nsfintf:i2nsf-security-policy"
                  +"/nsfintf:rules/nsfintf:name";
               }
               mandatory true;
               description
                 "The name of the I2NSF Policy Rule being triggered";
             }

             uses attack-rates;
             uses log-action;
             uses characteristics;
             uses common-monitoring-data;
           }
         }
         case i2nsf-nsf-detection-virus {
           if-feature "i2nsf-nsf-detection-virus";
           container i2nsf-nsf-detection-virus {
             description
               "This notification is sent, when a virus is detected.";
             uses i2nsf-nsf-event-type-content-extend;
             leaf virus-name {
               type string;
               description
                 "The name of the detected virus";
             }
             leaf virus-type {
               type identityref {
                 base virus-type;
               }
               description
                 "The virus type of the detected virus";
             }
             leaf host {
               type union {
                 type string;
                 type inet:ip-address-no-zone;
               }
               description
                 "The name or IP address of the host/device. This is
                  used to identify the host/device that is infected by
                  the virus. If the given name is not IP address, the
                  name can be an arbitrary string including FQDN
                  (Fully Qualified Domain Name). The name MUST be unique
                  in the scope of management domain for identifying the
                  device that has been infected with a virus.";
             }
             leaf file-type {
               type string;
               description
                 "The type of file virus code is found in (if
                  applicable).";
               reference
                 "IANA Website: Media Types";
             }
             leaf file-name {
               type string;
               description
                 "The name of file virus code is found in (if
                  applicable).";
             }
             leaf os {
               type string;
               description
                 "The operating system of the device.";
             }
             uses log-action;
             uses characteristics;
             uses common-monitoring-data;
           }
         }
         case i2nsf-nsf-detection-intrusion {
           if-feature "i2nsf-nsf-detection-intrusion";
           container i2nsf-nsf-detection-intrusion {
             description
               "This notification is sent, when an intrusion event
                is detected.";
             uses i2nsf-nsf-event-type-content-extend;
             leaf protocol {
               type identityref {
                 base transport-protocol;
               }
               description
                 "The transport protocol type for
                  nsf-detection-intrusion notification";
             }
             leaf app {
               type identityref {
                 base application-protocol;
               }
               description
                 "The employed application layer protocol";
             }
             leaf attack-type {
               type identityref {
                 base intrusion-attack-type;
               }
               description
                 "The sub attack type for intrusion attack";
             }
             uses log-action;
             uses attack-rates;
             uses characteristics;
             uses common-monitoring-data;
           }
         }
         case i2nsf-nsf-detection-web-attack {
           if-feature "i2nsf-nsf-detection-web-attack";
           container i2nsf-nsf-detection-web-attack {
             description
               "This notification is sent, when an attack event is
                detected.";
             uses i2nsf-nsf-event-type-content-extend;
             leaf attack-type {
               type identityref {
                 base web-attack-type;
               }
               description
                 "Concrete web attack type, e.g., SQL injection,
                  command injection, XSS, and CSRF.";
             }
             leaf req-method {
               type identityref {
                 base req-method;
               }
               description
                 "The HTTP method of the request, e.g., PUT or GET.";
               reference
                 "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1):
                  Semantics and Content - Request Methods";
             }
             leaf req-target {
               type string;
               description
                 "The HTTP Request Target. This field can be filled in
                  the format of origin-form, absolute-form,
                  authority-form, or asterisk-form";
               reference
                 "RFC 7230: Hypertext Transfer Protocol (HTTP/1.1):
                  Message Syntax and Routing - Request Target";
             }
             leaf-list filtering-type {
               type identityref {
                 base filter-type;
               }
               description
                 "URL filtering type, e.g., deny-list, allow-list,
                  and Unknown";
             }
             leaf req-user-agent {
               type string;
               description
                 "The HTTP User-Agent header field of the request";
               reference
                 "RFC 7231: Hypertext Transfer Protocol (HTTP/1.1):
                  Semantics and Content - User Agent";
             }
             leaf cookie {
               type string;
               description
                 "The HTTP Cookie header field of the request from
                  the user agent.";
               reference
                 "RFC 6265: HTTP State Management Mechanism - Cookie";
             }
             leaf req-host {
               type string;
               description
                 "The HTTP Host header field of the request";
               reference
                 "RFC 7230: Hypertext Transfer Protocol (HTTP/1.1):
                  Message Syntax and Routing - Host";
             }
             leaf response-code {
               type string;
               description
                 "The HTTP Response status code";
               reference
                 "IANA Website: Hypertext Transfer Protocol (HTTP)
                  Status Code Registry";
             }
             uses characteristics;
             uses log-action;
             uses common-monitoring-data;
           }
         }
         case i2nsf-nsf-detection-voip-volte{
           if-feature "i2nsf-nsf-detection-voip-volte";
           container i2nsf-nsf-detection-voip-volte {
             description
               "This notification is sent, when a VoIP/VoLTE violation
                is detected.";
             uses i2nsf-nsf-event-type-content-extend;
             leaf-list source-voice-id {
               type string;
               description
                 "The detected source voice ID for VoIP and VoLTE that
                  violates the security policy.";
             }
             leaf-list destination-voice-id {
               type string;
               description
                 "The detected destination voice ID for VoIP and VoLTE
                  that violates the security policy.";
             }
             leaf-list user-agent {
               type string;
               description
                 "The detected user-agent for VoIP and VoLTE that
                  violates the security policy.";
             }
             uses common-monitoring-data;
           }
         }
       }
     }
     /*
      * Data nodes
      */
     container i2nsf-counters {
       config false;
       description
         "The state data representing continuous value changes of
          information elements that occur very frequently. The value
          should be calculated from the start of the service of the
          NSF.";

       leaf language {
         type string {
           pattern
              "^((en-GB-oed|i-ami|i-bnn|i-default|"
            + "i-enochian|i-hak|i-klingon|i-lux|i-mingo|i-navajo|i-pwn|"
            + "i-tao|i-tay|i-tsu|sgn-BE-FR|sgn-BE-NL|sgn-CH-DE)|"
            + "(art-lojban|cel-gaulish|no-bok|no-nyn|zh-guoyu|zh-hakka|"
            + "zh-min|zh-min-nan|zh-xiang)|"
            + "(([A-Za-z]{2,3}(-[A-Za-z]{3}(-[A-Za-z]{3}){0,2})?)|"
            + "[A-Za-z]{4}|[A-Za-z]{5,8}"
            + "(-[A-Za-z]{4})?"
            + "(-[A-Za-z]{2}|[0-9]{3})?"
            + "(-[A-Za-z0-9]{5,8}|[0-9][A-Za-z0-9]{3})*"
            + "(-[0-9A-WY-Za-wy-z](-[A-Za-z0-9]{2,8})+)*"
            + "(-x(-[A-Za-z0-9]{1,8})+)?)|"
            + "x(-[A-Za-z0-9]{1,8})+)$";
         }
         description
           "The value in this field describes the human language
            intended for the user, so that it allows a user to
            differentiate the language that is used in the
            notification. This field is not mandatory, but required
            when the implementation provides more than one human
            language for the human-readable string fields,
            e.g., /i2nsf-counters/system-interface/message.

            This field uses the language-tag production in Section 2.1
            in RFC 5646. See the document for more details.";
         reference
           "RFC 5646: Tags for Identifying Languages";
       }

       list system-interface {
         key interface-name;
         description
           "Interface counters provide the visibility of traffic into
            and out of an NSF, and bandwidth usage.";
         uses characteristics;
         uses i2nsf-system-counter-type-content;
         uses common-monitoring-data;
         uses timestamp;
       }
       list nsf-firewall {
         key policy-name;
         description
           "Firewall counters provide the visibility of traffic
            signatures, bandwidth usage, and how the configured security
            and bandwidth policies have been applied.";
         uses characteristics;
         uses i2nsf-nsf-counters-type-content;
         uses traffic-rates;
         uses common-monitoring-data;
         uses timestamp;
       }
       list nsf-policy-hits {
         key policy-name;
         description
           "Policy Hit Counters record the number of hits that traffic
            packets match a security policy. It can check if policy
            configurations are correct or not.";
         uses characteristics;
         uses i2nsf-nsf-counters-type-content;
         uses common-monitoring-data;
         leaf discontinuity-time {
           type yang:date-and-time;
           mandatory true;
           description
             "The time on the most recent occasion at which any one or
              more of the counters suffered a discontinuity. If no such
              discontinuities have occurred since the last
              re-initialization of the local management subsystem, then
              this node contains the time the local management subsystem
              was re-initialized.";
         }
         leaf hit-times {
           type yang:counter64;
           description
             "The number of times that the security policy matches the
              specified traffic.";
         }
         uses timestamp;
       }
     }

     container i2nsf-monitoring-configuration {
       description
         "The container for configuring I2NSF monitoring.";
       container i2nsf-system-detection-alarm {
         description
           "The container for configuring I2NSF system-detection-alarm
            notification";
         uses enable-notification;
         list system-alarm {
           key alarm-type;
           description
             "Configuration for system alarm (i.e., CPU, Memory, and
              Disk Usage)";
           leaf alarm-type {
             type enumeration {
               enum cpu {
                 description
                   "To configure the CPU usage threshold to trigger the
                    cpu-alarm";
               }
               enum memory {
                 description
                   "To configure the Memory usage threshold to trigger
                    the memory-alarm";
               }
               enum disk {
                 description
                   "To configure the Disk (storage) usage threshold to
                    trigger the disk-alarm";
               }

             }
             description
               "Type of alarm to be configured. The three alarm-types
                defined here are used to configure the threshold of the
                monitoring notification. The threshold is used to
                determine when the notification should be sent.
                The other two alarms defined in the module (i.e.,
                hardware-alarm and interface-alarm) do not use any
                threshold value to create a notification. These alarms
                detect a failure or a change of state to create a
                notification.";
           }
           leaf threshold {
             type uint8 {
               range "1..100";
             }
             units "percent";
             description
               "The configuration for threshold percentage to trigger
                the alarm. The alarm will be triggered if the usage
                is exceeded the threshold.";
           }
           uses dampening;
         }
       }
       container i2nsf-system-detection-event {
         description
           "The container for configuring I2NSF system-detection-event
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-traffic-flows {
         description
           "The container for configuring I2NSF traffic-flows
            notification";
         uses dampening;
         uses enable-notification;
       }
       container i2nsf-nsf-detection-ddos {
         if-feature "i2nsf-nsf-detection-ddos";
         description
           "The container for configuring I2NSF nsf-detection-ddos
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-nsf-detection-session-table {
         description
           "The container for configuring I2NSF nsf-detection-session-
            table notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-nsf-detection-intrusion {
         if-feature "i2nsf-nsf-detection-intrusion";
         description
           "The container for configuring I2NSF nsf-detection-intrusion
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-nsf-detection-web-attack {
         if-feature "i2nsf-nsf-detection-web-attack";
         description
           "The container for configuring I2NSF nsf-detection-web-attack
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-nsf-system-access-log {
         description
           "The container for configuring I2NSF system-access-log
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-system-res-util-log {
         description
           "The container for configuring I2NSF system-res-util-log
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-system-user-activity-log {
         description
           "The container for configuring I2NSF system-user-activity-log
            notification";
         uses enable-notification;
         uses dampening;
       }
       container i2nsf-nsf-log-dpi {
         if-feature "i2nsf-nsf-log-dpi";
         description
           "The container for configuring I2NSF nsf-log-dpi
            notification";

         uses enable-notification;
         uses dampening;
       }
       container i2nsf-counter {
         description
           "This is used to configure the counters
            for monitoring an NSF";
         leaf period {
           type uint16;
           units "minutes";
           default 0;
           description
             "The configuration for the period interval of reporting
              the counter. If 0, then the counter period is disabled.
              If value is not 0, then the counter will be reported
              following the period value.";
         }
       }
     }
   }
   <CODE ENDS>

                     Figure 2: Data Model of Monitoring

9.  I2NSF Event Stream

   This section discusses the NETCONF event stream for I2NSF NSF
   Monitoring subscription.  The YANG module in this document supports
   "ietf-subscribed-notifications" YANG module [RFC8639] for
   subscription.  The reserved event stream name for this document is
   "I2NSF-Monitoring".  The NETCONF Server (e.g., an NSF) MUST support
   "I2NSF-Monitoring" event stream for an NSF data collector (e.g.,
   Security Controller).  The "I2NSF-Monitoring" event stream contains
   all I2NSF events described in this document.

   The following XML example shows the capabilities of the event streams
   generated by an NSF (e.g., "NETCONF" and "I2NSF-Monitoring" event
   streams) for the subscription of an NSF data collector.  Refer to
   [RFC5277] for more detailed explanation of Event Streams.  The XML
   examples in this document follow the line breaks as per [RFC8792].

   <?xml version="1.0" encoding="UTF-8"?>
   <rpc-reply message-id="1"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <netconf xmlns="urn:ietf:params:xml:ns:netmod:notification">
         <streams>
           <stream>
             <name>NETCONF</name>
             <description>Default NETCONF Event Stream</description>
             <replaySupport>false</replaySupport>
           </stream>
           <stream>
             <name>I2NSF-Monitoring</name>
             <description>I2NSF Monitoring Event Stream</description>
             <replaySupport>true</replaySupport>
             <replayLogCreationTime>
               2021-04-29T09:37:39+00:00
             </replayLogCreationTime>
           </stream>
         </streams>
       </netconf>
     </data>
   </rpc-reply>

      Figure 3: Example of NETCONF Server supporting I2NSF-Monitoring
                                Event Stream

10.  XML Examples for I2NSF NSF Monitoring

   This section shows XML examples of I2NSF NSF Monitoring data
   delivered via Monitoring Interface from an NSF.  In order for the XML
   data to be used correctly, the prefix (i.e., the characters before
   the colon or 'nsfmi' in the example) in the content of the element
   that uses the "identityref" type (e.g., /i2nsf-event/i2nsf-system-
   detection-alarm/alarm-category/) in the YANG module described in this
   document MUST be the same as the namespace prefix (i.e., 'nsfmi' in
   the example) for urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-
   monitoring.  Therefore, XML software MUST be chosen that makes the
   namespace prefix information available.

10.1.  I2NSF System Detection Alarm

   The following example shows an alarm triggered by Memory Usage of the
   server; note that this example XML file is delivered by an NSF to an
   NSF data collector:

   <?xml version="1.0" encoding="UTF-8"?>
   <notification
    xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
     <eventTime>2021-04-29T07:43:52.181088+00:00</eventTime>
     <i2nsf-event
       xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring">
       <i2nsf-system-detection-alarm>
         <alarm-category
           xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                        ietf-i2nsf-nsf-monitoring">
           nsfmi:memory-alarm
         </alarm-category>
         <acquisition-method
           xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                        ietf-i2nsf-nsf-monitoring">
           nsfmi:subscription
         </acquisition-method>
         <emission-type
           xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                        ietf-i2nsf-nsf-monitoring">
           nsfmi:on-change
         </emission-type>
         <dampening-type
           xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                        ietf-i2nsf-nsf-monitoring">
           nsfmi:on-repetition
         </dampening-type>
         <usage>91</usage>
         <threshold>90</threshold>
         <message>Memory Usage Exceeded the Threshold</message>
         <nsf-name>time_based_firewall</nsf-name>
         <severity>high</severity>
       </i2nsf-system-detection-alarm>
     </i2nsf-event>
   </notification>

       Figure 4: Example of I2NSF System Detection Alarm triggered by
                                Memory Usage

   The XML data above shows:

   1.  The NSF that sends the information is named
       "time_based_firewall".

   2.  The memory usage of the NSF triggered the alarm.

   3.  The monitoring information is received by subscription method.

   4.  The monitoring information is emitted "on-change".

   5.  The monitoring information is dampened "on-repetition".

   6.  The memory usage of the NSF is 91 percent.

   7.  The memory threshold to trigger the alarm is 90 percent.

   8.  The severity level of the notification is high.

10.2.  I2NSF Interface Counters

   To get the I2NSF system interface counters information by query,
   NETCONF Client (e.g., NSF data collector) needs to initiate GET
   connection with NETCONF Server (e.g., NSF).  The following XML file
   can be used to get the state data and filter the information.

   <?xml version="1.0" encoding="UTF-8"?>
   <rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1">
     <get>
       <filter
         xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring">
         <i2nsf-counters>
           <system-interface/>
         </i2nsf-counters>
       </filter>
     </get>
   </rpc>

     Figure 5: XML Example for NETCONF GET with System Interface Filter

   The following XML file shows the reply from the NETCONF Server (e.g.,
   NSF):

   <?xml version="1.0" encoding="UTF-8"?>
   <rpc-reply message-id="1"
              xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <i2nsf-counters
         xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring">
         <system-interface>
           <discontinuity-time>
             2021-04-29T08:43:52.181088+00:00
           </discontinuity-time>
           <interface-name>ens3</interface-name>
           <acquisition-method
             xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                          ietf-i2nsf-nsf-monitoring">
             nsfmi:query
           </acquisition-method>
           <in-total-traffic-bytes>549050</in-total-traffic-bytes>
           <out-total-traffic-bytes>814956</out-total-traffic-bytes>
           <in-drop-traffic-bytes>0</in-drop-traffic-bytes>
           <out-drop-traffic-bytes>5078</out-drop-traffic-bytes>
           <nsf-name>time_based_firewall</nsf-name>
         </system-interface>
         <system-interface>
           <discontinuity-time>
             2021-04-29T08:43:52.181088+00:00
           </discontinuity-time>
           <interface-name>lo</interface-name>
           <acquisition-method
             xmlns:nsfmi="urn:ietf:params:xml:ns:yang:\
                          ietf-i2nsf-nsf-monitoring">
             nsfmi:query
           </acquisition-method>
           <in-total-traffic-bytes>48487</in-total-traffic-bytes>
           <out-total-traffic-bytes>48487</out-total-traffic-bytes>
           <in-drop-traffic-bytes>0</in-drop-traffic-bytes>
           <out-drop-traffic-bytes>0</out-drop-traffic-bytes>
           <nsf-name>time_based_firewall</nsf-name>
         </system-interface>
       </i2nsf-counters>
     </data>
   </rpc-reply>

    Figure 6: Example of I2NSF System Interface Counters XML Information

11.  IANA Considerations

   This document requests IANA to register the following URI in the
   "IETF XML Registry" [RFC3688]:

     URI: urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring
     Registrant Contact: The IESG.
     XML: N/A; the requested URI is an XML namespace.

   This document requests IANA to register the following YANG module in
   the "YANG Module Names" registry [RFC7950][RFC8525]:

     name: ietf-i2nsf-nsf-monitoring
     namespace: urn:ietf:params:xml:ns:yang:ietf-i2nsf-nsf-monitoring
     prefix: nsfmi
     reference: RFC XXXX

     // RFC Ed.: replace XXXX with an actual RFC number and remove
     // this note.

12.  Security Considerations

   The YANG module described in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the required secure transport is
   Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer is HTTPS,
   and the required secure transport is TLS [RFC8446].

   The NETCONF access control model [RFC8341] provides a means of
   restricting access to specific NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   All data nodes defined in the YANG module which can be created,
   modified and deleted (i.e., config true, which is the default) are
   considered sensitive as they all could potentially impact security
   monitoring and mitigation activities.  Write operations (e.g., edit-
   config) applied to these data nodes without proper protection could
   result in missed alarms or incorrect alarms information being
   returned to the NSF data collector.  There are threats that need to
   be considered and mitigated:

   Compromised NSF with valid credentials:  It can send falsified
      information to the NSF data collector to mislead detection or
      mitigation activities; and/or to hide activity.  Currently, there
      is no in-framework mechanism to mitigate this and an issue for all
      monitoring infrastructures.  It is important to keep the enclosure
      of confidential information to unauthorized persons to mitigate
      the possibility of compromising the NSF with this information.

   Compromised NSF data collector with valid credentials:  It has
      visibility to all collected security alarms; entire detection and
      mitigation infrastructure may be suspect.  It is important to keep
      the enclosure of confidential information to unauthorized persons
      to mitigate the possibility of compromising the NSF with this
      information.

   Impersonating NSF:  It is a system trying to send false information
      while imitating an NSF; client authentication would help the NSF
      data collector to identify this invalid NSF in the "push" model
      (NSF-to-collector), while the "pull" model (collector-to-NSF)
      should already be addressed with the authentication.

   Impersonating NSF data collector:  It is a rogue NSF data collector
      with which a legitimate NSF is tricked into communicating; for
      "push" model (NSF-to-collector), it is important to have valid
      credentials, without it it should not work; for "pull" model
      (collector-to-NSF), mutual authentication should be used to
      mitigate the threat.

   In addition, to defend against the DDoS attack caused by a lot of
   NSFs sending massive notifications to the NSF data collector, the
   rate limiting or similar mechanisms should be considered in both an
   NSF and NSF data collector, whether in advance or just in the process
   of DDoS attack.

   All of the readable data nodes in this YANG module may be considered
   sensitive in some network environments.  These data nodes represent
   information consistent with the logging commonly performed in network
   and security operations.  They may reveal the specific configuration
   of a network; vulnerabilities in specific systems; and the deployed
   security controls and their relative efficacy in detecting or
   mitigating an attack.  To an attacker, this information could inform
   how to (further) compromise the network, evade detection, or confirm
   whether they have been observed by the network operator.

   Additionally, many of the data nodes in this YANG module such as
   containers "i2nsf-system-user-activity-log", "i2nsf-system-detection-
   event", and "i2nsf-nsf-detection-voip-volte" are privacy sensitive.
   They may describe specific or aggregate user activity to include
   associating user names with specific IP addresses; or users with
   specific network usage.

13.  Acknowledgments

   This document is a product by the I2NSF Working Group (WG) including
   WG Chairs (i.e., Linda Dunbar and Yoav Nir) and Diego Lopez.  This
   document took advantage of the review and comments from the following
   people: Roman Danyliw, Tim Bray (IANA), Kyle Rose (TSV-ART), Dale R.
   Worley (Gen-ART), Melinda Shore (SecDir), Valery Smyslov (ART-ART),
   and Tom Petch.  We authors sincerely appreciate their sincere efforts
   and kind help.

   This work was supported by Institute of Information & Communications
   Technology Planning & Evaluation (IITP) grant funded by the Korea
   MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based
   Security Intelligence Technology Development for the Customized
   Security Service Provisioning).  This work was supported in part by
   the IITP (2020-0-00395, Standard Development of Blockchain based
   Network Management Automation Technology).  This work was supported
   in part by the MSIT under the Information Technology Research Center
   (ITRC) support program (IITP-2021-2017-0-01633) supervised by the
   IITP.

14.  Contributors

   This document is made by the group effort of I2NSF working group.
   Many people actively contributed to this document.  The authors
   sincerely appreciate their contributions.

   The following are co-authors of this document:

   Chaehong Chung - Department of Electronic, Electrical and Computer
   Engineering, Sungkyunkwan University, 2066 Seobu-ro Jangan-gu, Suwon,
   Gyeonggi-do 16419, Republic of Korea, Email: darkhong@skku.edu

   Jinyong (Tim) Kim - Department of Electronic, Electrical and Computer
   Engineering, Sungkyunkwan University, 2066 Seobu-ro Jangan-gu, Suwon,
   Gyeonggi-do 16419 16419, Republic of Korea, Email: timkim@skku.edu, timkim@skku.edu

   Dongjin Hong - Department of Electronic, Electrical and Computer
   Engineering, Sungkyunkwan University, 2066 Seobu-ro Jangan-gu, Suwon,
   Gyeonggi-do 16419, Republic of Korea, Email: dong.jin@skku.edu, dong.jin@skku.edu

   Dacheng Zhang - Huawei, Email: dacheng.zhang@huawei.com

   Yi Wu - Aliababa Group, Email: anren.wy@alibaba-inc.com
   Rakesh Kumar - Juniper Networks, 1133 Innovation Way, Sunnyvale, CA
   94089, USA, Email: rkkumar@juniper.net

   Anil Lohiya - Juniper Networks, Email: alohiya@juniper.net

15.  References

15.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <https://www.rfc-editor.org/info/rfc791>.

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <https://www.rfc-editor.org/info/rfc792>.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC0854]  Postel, J. and J. Reynolds, "Telnet Protocol
              Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May
              1983, <https://www.rfc-editor.org/info/rfc854>.

   [RFC0959]  Postel, J. and J. Reynolds, "File Transfer Protocol",
              STD 9, RFC 959, DOI 10.17487/RFC0959, October 1985,
              <https://www.rfc-editor.org/info/rfc959>.

   [RFC1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
              STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,
              <https://www.rfc-editor.org/info/rfc1939>.

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

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

   [RFC3877]  Chisholm, S. and D. Romascanu, "Alarm Management
              Information Base (MIB)", RFC 3877, DOI 10.17487/RFC3877,
              September 2004, <https://www.rfc-editor.org/info/rfc3877>.

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340,
              DOI 10.17487/RFC4340, March 2006,
              <https://www.rfc-editor.org/info/rfc4340>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,
              <https://www.rfc-editor.org/info/rfc4960>.

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

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              DOI 10.17487/RFC5321, October 2008,
              <https://www.rfc-editor.org/info/rfc5321>.

   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying
              Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646,
              September 2009, <https://www.rfc-editor.org/info/rfc5646>.

   [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>.

   [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>.

   [RFC6265]  Barth, A., "HTTP State Management Mechanism", RFC 6265,
              DOI 10.17487/RFC6265, April 2011,
              <https://www.rfc-editor.org/info/rfc6265>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [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>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [RFC8329]  Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
              Kumar, "Framework for Interface to Network Security
              Functions", RFC 8329, DOI 10.17487/RFC8329, February 2018,
              <https://www.rfc-editor.org/info/rfc8329>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.

   [RFC8639]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Subscription to YANG Notifications",
              RFC 8639, DOI 10.17487/RFC8639, September 2019,
              <https://www.rfc-editor.org/info/rfc8639>.

   [RFC8641]  Clemm, A. and E. Voit, "Subscription to YANG Notifications
              for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
              September 2019, <https://www.rfc-editor.org/info/rfc8641>.

   [RFC9051]  Melnikov, A., Ed. and B. Leiba, Ed., "Internet Message
              Access Protocol (IMAP) - Version 4rev2", RFC 9051,
              DOI 10.17487/RFC9051, August 2021,
              <https://www.rfc-editor.org/info/rfc9051>.

   [I-D.ietf-i2nsf-nsf-facing-interface-dm]
              Kim, J. (., Jeong, J. (., Park, J., Hares, S., and Q. Lin,
              "I2NSF Network Security Function-Facing Interface YANG
              Data Model", Work in Progress, Internet-Draft, draft-ietf-
              i2nsf-nsf-facing-interface-dm-16, 13 November 2021,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-nsf-
              facing-interface-dm-16.txt>.

   [I-D.ietf-tcpm-rfc793bis]
              Eddy, W. M., "Transmission Control Protocol (TCP)
              Specification", Work in Progress, Internet-Draft, draft-
              ietf-tcpm-rfc793bis-25, 7 September 2021,
              <https://www.ietf.org/archive/id/draft-ietf-tcpm-
              rfc793bis-25.txt>.

15.2.  Informative References

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/info/rfc4949>.

   [RFC8329]  Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
              Kumar, "Framework for Interface to Network Security
              Functions", RFC 8329, DOI 10.17487/RFC8329, February 2018,
              <https://www.rfc-editor.org/info/rfc8329>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

   [I-D.ietf-i2nsf-nsf-facing-interface-dm]
              Kim, J. (., Jeong, J. (., Park, J., Hares, S., and Q. Lin,
              "I2NSF Network Security Function-Facing Interface YANG
              Data Model", Work in Progress, Internet-Draft, draft-ietf-
              i2nsf-nsf-facing-interface-dm-16, 13 November 2021,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-nsf-
              facing-interface-dm-16.txt>.

   [I-D.ietf-i2nsf-consumer-facing-interface-dm]
              Jeong, J. (., Chung, C., Ahn, T., Kumar, R., and S. Hares,
              "I2NSF Consumer-Facing Interface YANG Data Model", Work in
              Progress, Internet-Draft, draft-ietf-i2nsf-consumer-
              facing-interface-dm-15, 15 September 2021,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-
              consumer-facing-interface-dm-15.txt>.

   [I-D.ietf-tcpm-rfc793bis]
              Eddy, W. M., "Transmission Control Protocol (TCP)
              Specification", Work in Progress, Internet-Draft, draft-
              ietf-tcpm-rfc793bis-25, 7 September 2021,
              <https://www.ietf.org/archive/id/draft-ietf-tcpm-
              rfc793bis-25.txt>.

   [IANA-HTTP-Status-Code]
              Internet Assigned Numbers Authority (IANA), "Hypertext
              Transfer Protocol (HTTP) Status Code Registry", September
              2018, <https://www.iana.org/assignments/http-status-codes/
              http-status-codes.xhtml>.

   [IANA-Media-Types]
              Internet Assigned Numbers Authority (IANA), "Media Types",
              August 2021, <https://www.iana.org/assignments/media-
              types/media-types.xhtml>.

Appendix A.  Changes from draft-ietf-i2nsf-nsf-monitoring-data-model-12 draft-ietf-i2nsf-nsf-monitoring-data-model-13

   The following changes are made from draft-ietf-i2nsf-nsf-monitoring-
   data-model-12:
   data-model-13:

   *  This version is revised following added to update the comments from Tim Bray
      (IANA), Kyle Rose (TSV-ART), Dale R.  Worley (Gen-ART), Melinda
      Shore (SecDir), Valery Smyslov (ART-ART), and Tom Petch. references.

Authors' Addresses

   Jaehoon (Paul) Jeong (editor)
   Department of Computer Science and Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea

   Phone: +82 31 299 4957
   Email: pauljeong@skku.edu
   URI:   http://iotlab.skku.edu/people-jaehoon-jeong.php

   Patrick Lingga
   Department of Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea

   Phone: +82 31 299 4957
   Email: patricklink@skku.edu

   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI 48176
   United States of America

   Phone: +1-734-604-0332
   Email: shares@ndzh.com

   Liang (Frank) Xia
   Huawei
   101 Software Avenue, Yuhuatai District
   Nanjing
   Jiangsu,
   China

   Email: Frank.xialiang@huawei.com

   Henk Birkholz
   Fraunhofer Institute for Secure Information Technology
   Rheinstrasse 75
   64295 Darmstadt
   Germany

   Email: henk.birkholz@sit.fraunhofer.de