Internet-Draft NSF Monitoring Interface YANG Data Model May 2022
Jeong, et al. Expires 24 November 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-i2nsf-nsf-monitoring-data-model-19
Published:
Intended Status:
Standards Track
Expires:
Authors:
J. Jeong, Ed.
Sungkyunkwan University
P. Lingga
Sungkyunkwan University
S. Hares
Huawei
L. Xia
Huawei
H. Birkholz
Fraunhofer SIT

I2NSF NSF Monitoring Interface YANG Data Model

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 standard 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 tree diagram, but also the corresponding YANG data model.

Status of This Memo

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

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

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

This Internet-Draft will expire on 24 November 2022.

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Table of Contents

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 an NSF data collector (e.g., Security Controller) 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 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 (DoS) attacks.

This document defines an 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.

Note that this document covers a subset of monitoring data for systems and NSFs, which are related to security.

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:

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:

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 checking 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 of monitoring data originating from a system entity [RFC4949], i.e., an NSF, are discussed in this document.

Every system entity creates information about some context with defined I2NSF monitoring data, and so every system entity that provides such information 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 from NSFs

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 Events, I2NSF Records, and I2NSF Counters 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 of 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 the information, which is based on operational and informational data (i.e., various changes in system characteristics). They are generated by a system entity (e.g., NSF) 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 Events, records do not require immediate attention but may be useful for visibility and retroactive cyber forensics. Records are typically stored in log-files or databases on a system entity or NSF. The examples of records include 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. 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, a system entity MUST update the counter information and emit the latest information to the NSF data collector.

Retention is defined as the storing of monitoring data in NSFs. 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.

Emission is defined as the delivery of monitoring data in NSFs to an NSF data collector. 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 standardized delivery protocols (e.g., RESTCONF and NETCONF). The interface for the delivery of Monitoring Data from the NSF data collector to the I2NSF User is out of the scope of this document.

4.2. Notifications for Events and Records

A specific task of an I2NSF User is to provide 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, information about 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 or 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.

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. Push and Pull for the retrieval of monitoring data from NSFs

An important aspect of monitoring information is the freshness of the information. From the perspective of security, it is important to notice changes in 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. Monitoring information can be acquired by a client (i.e., NSF data collector) from a server (i.e., NSF) using push [RFC5277] [RFC8641] or pull methods [RFC6241] [RFC8040].

The 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 request is accepted (with proper authentication), the NSF MUST update the information before sending it to the NSF data collector.

The push 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 push method, while information that has a lower level of urgency (i.e., I2NSF Record and I2NSF Counter) can be provided with either the pull method or push method.

5. Basic Information Model for Monitoring Data

As explained in the above section, there is a wealth of data available from NSFs 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 metadata with that message, which are listed as below:

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 settable characteristics for data collection as follows:

Note that the characteristic information is not mandatory to be included in a monitoring message. The information is expected to be stored and may or may not be useful in some ways in the future. In any case, the inclusion of the characteristic information is up to the implementation.

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 memory usage exceeds the threshold. The following information should be included in a Memory Alarm:

  • event-name: memory-alarm.
  • usage: specifies the amount of memory used in percentage.
  • threshold: The threshold triggering the alarm in percentage.
  • severity: The severity level of the message. There are four levels, i.e., critical, high, middle, and low.
  • message: Simple information as a human readable text string 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 in percentage.
  • threshold: The threshold triggering the event in percentage.
  • severity: The severity level of the message. There are four levels, i.e., critical, high, middle, and low.
  • message: Simple information as a human readable text string such as "The CPU usage exceeded the threshold" or with extra information.

6.1.3. Disk (Storage) Alarm

Disk or storage is the hardware to store information for a long time, 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 ratio of the used disk space to the whole disk space in terms of percentage.
  • threshold: The threshold triggering the event in percentage.
  • severity: The severity level of the message. There are four levels, i.e., critical, high, middle, and low.
  • message: Simple information as a human readable text string 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 four levels, i.e., critical, high, middle, and low.
  • message: Simple information as a human readable text string 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: The status of the interface, i.e., down, up (not congested), congested (up but congested), testing, unknown, dormant, not-present, and lower-layer-down.
  • severity: The severity level of the message. There are four levels, i.e., critical, high, middle, and low.
  • message: Simple information as a human readable text string 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. l4-port-number: The transport layer 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 as a human readable text string 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 user that updated the configuration. 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. l4-port-number: The transport layer 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 as a human readable text string 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

A session is defined as a connection (i.e., traffic flow) of a data plane (e.g., TCP, UDP, and SCTP). Session Table Event is the event triggered by the session table of an NSF. A session table holds the information of the currently 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 (in terms of an allowed number of sessions) triggering the event.
  • message: The message as a human readable text string to give the context of the event, such as "The number of sessions exceeded the table 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.
  • interface-name: The mnemonic name of the network interface
  • interface-type: The type of a network interface such as an ingress or egress interface.
  • src-mac: The source MAC address of the traffic flow. This information may or may not be included depending on the type of traffic flow. For example, the information will be useful and should be included if the traffic flows are traffic flows of Link Layer Discovery Protocol (LLDP) [IEEE-802.1AB], Address Resolution Protocol (ARP) for IPv4 [RFC0826], and Neighbor Discovery Protocol (ND) for IPv6 [RFC4861].
  • dst-mac: The destination MAC address of the traffic flow. This information may or may not be included depending on the type of traffic flow. For example, the information will be useful and should be included if the traffic flows are LLDP, ARP for IPv4, or ND for IPv6 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 transport layer source port number of the traffic flow.
  • dst-port: The transport layer destination port number of the traffic flow.
  • protocol: The protocol of the traffic flow.
  • measurement-time: The duration of the measurement in seconds for the arrival rate and arrival throughput of packets of a traffic flow. These two metrics (i.e., arrival rate and arrival throughput) are measured over the past measurement duration before now.
  • arrival-rate: Arrival rate of packets of the traffic flow in packets per second measured over the past "measurement-time".
  • arrival-throughput: Arrival rate of packets of the traffic flow in bytes per second measured over the past "measurement-time".

Note that the NSF Monitoring Interface data model is focused on a generic method to collect the monitoring information of systems and NSFs including traffic flows related to security attacks and system resource usages. On the other hand, IPFIX [RFC7011] is a standard method to collect general information on traffic flows rather than security.

6.3. NSF Events

The NSF events provide the event that is detected by a specific NSF that supported a certain capability. This section only discusses the monitoring data for the advanced NSFs discussed in [I-D.ietf-i2nsf-capability-data-model]. The NSF events information can be extended to support other types of NSF. 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 Denial-of-Service (DoS) or Distributed Denial-of-Service (DDoS) Event:

  • event-name: detection-ddos.
  • attack-type: The type of DoS or 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, TLS flood, and NTP amplification flood. This can be extended with additional types of DoS or DDoS attack.
  • attack-src-ip: The IP addresses of the source of the DDoS attack. Note that not all IP addresses should be included but only limited IP addresses are included to conserve the server resources. The listed attacking IP addresses can be an arbitrary sampling of the "top talkers", i.e., the attackers that send the highest amount of traffic.
  • attack-dst-ip: The destination IPv4 or IPv6 addresses of attack traffic. It can hold multiple IPv4 or IPv6 addresses.
  • attack-src-port: The transport layer source port numbers of the attack traffic. Note that not all ports will have been seen on all the corresponding source IP addresses.
  • attack-dst-port: The transport layer destination port numbers that the attack traffic aims at. Note that not all ports will have been seen on all the corresponding destination IP addresses.
  • start-time: The time stamp indicating when the attack started. The time format used is following the rules in Section 5.6 of [RFC3339].
  • end-time: The time stamp indicating when the attack ended. If the attack is still ongoing when sending out the notification, this field can be empty. The time format used is following the rules in Section 5.6 of [RFC3339].
  • attack-rate: The packets per second of attack traffic.
  • attack-throughput: 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 a traffic flow or inside a host. Note that "malware" is a more generic word for malicious software, including virus and worm. In the document, "virus" is used to represent "malware" such that they are interchangeable. 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, and macro virus.

  • The following information is used only when the virus is detected within the traffic flow and not yet attacking the host:

    • dst-ip: The destination IP address of the flow where the virus is found.
    • src-ip: The source IP address of the flow where the virus is found.
    • src-port: The source port of the flow where the virus is found.
    • dst-port: The destination port of the flow where the virus is found.

  • The following information is used only when the virus is detected within a host system:

    • host: The name or IP address of the host/device that is infected by the virus. If the given name is not an IP address, the name can be an arbitrary string including a 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.
    • file-type: The type of file (indicated by the file's suffix, e.g., .exe) virus code is found in (if applicable).
    • file-name: The name of the file where the virus is hidden.
  • rule-name: The name of the rule being triggered.

Note "host" is used only when the virus is detected within a host itself. Thus, the traffic flow information such as the source and destination IP addresses is not important, so the elements of the traffic flow (i.e., dst-ip, src-ip, src-port, and dst-port) are not specified above. On the other hand, when the virus is detected within a traffic flow and not yet attacking a host, the element of "host" is not specified above.

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 or 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
  • protocol: The employed transport layer protocol. e.g., TCP or UDP. Note that QUIC protocol [RFC9000] is excluded in the data model as it is not considered in the initial I2NSF documents [RFC8329]. The QUIC traffic should not be treated as generic UDP traffic and will be considered in the future I2NSF documents.
  • app: The employed application layer protocol. e.g., HTTP or 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, or 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.
  • 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.
  • cookies: The HTTP Cookie header field of the request from the user agent. Note that though cookies have many historical infelicities that degrade security and privacy, the Cookie and Set-Cookie header fields are widely used on the Internet [RFC6265]. Thus, the cookies information needs to be kept confidential and is NOT RECOMMENDED to be included in the monitoring data unless the information is absolutely necessary to help to enhance the security of the network.
  • 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/VoCN Event

The following information should be included in a VoIP (Voice over Internet Protocol) and VoCN (Voice over Cellular Network, such as Voice over LTE or 5G) Event:

  • event-name: detection-voip-vocn
  • source-voice-id: The detected source voice Call ID for VoIP and VoCN that violates the policy.
  • destination-voice-id: The destination voice Call ID for VoIP and VoCN that violates the policy.
  • user-agent: The user agent for VoIP and VoCN that violates the policy.
  • src-ip: The source IP address of the VoIP/VoCN.
  • dst-ip: The destination IP address of the VoIP/VoCN.
  • src-port: The source port number of the VoIP/VoCN.
  • dst-port: The destination port number of VoIP/VoCN.
  • 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 or periodic
  • 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, some 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. l4-port-number: The transport layer 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 executed, 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 in percentage.
  • memory-usage: Specifies the memory usage in percentage.
  • disk-id: Specifies the disk ID to identify the storage disk.
  • disk-usage: Specifies the disk usage of disk-id in percentage.
  • disk-space-left: Specifies the available disk space left of disk-id in percentage.
  • 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 data plane traffic rate in packets per second.
  • out-traffic-rate: The total outbound data plane traffic rate in packets per second.
  • in-traffic-throughput: The total inbound data plane traffic throughput in bytes per second.
  • out-traffic-throughput: The total outbound data plane traffic throughput in bytes per second.

Note that "traffic" includes only the data plane since the monitoring interface focuses on the monitoring of traffic flows for applications, rather than the control plane. In the document, "packet" includes a layer-2 frame, so "packet" and "frame" are interchangeable. Also, note that system resources (e.g., CPU, memory, disk, and interface) are monitored for the sake of security in NSFs even though they are common ones to be monitored by a generic Operations, Administration and Maintenance (OAM) protocol (or module).

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 is as follows:

    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. l4-port-number: The transport layer 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
  • dampening-type: on-repetition or no-dampening

6.5.1. Deep Packet Inspection Log

Deep Packet Inspection (DPI) Logs provide statistics of transit traffic at an NSF such that the traffic includes uploaded and downloaded files/data, sent/received emails, and blocking/alert 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-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
  • rule-name: The name of the I2NSF Policy Rule being triggered.
  • 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
  • dampening-type: no-dampening

6.6.1. Interface Counter

Interface counters provide visibility into traffic into and out of an NSF, and bandwidth usage.

  • interface-name: Network interface name configured in NSF.
  • protocol: The type of network protocol (e.g., IPv4, IPv6, TCP, and UDP). If this field is empty, then the counter is used for all protocols.
  • measurement-time: The duration of the measurement in seconds for the calculation of statistics such as traffic rate and throughput. The statistic attributes are measured over the past measurement duration before now.
  • 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 caused by a policy or hardware/resource error.
  • out-drop-traffic-pkts: Total outbound drop packets caused by a policy or hardware/resource error.
  • in-drop-traffic-bytes: Total inbound drop bytes caused by a policy or hardware/resource error.
  • out-drop-traffic-bytes: Total outbound drop bytes caused by a policy or hardware/resource error.
  • total-traffic: The total number of traffic packets (in and out) in the NSF.
  • 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-throughput: Inbound traffic average throughput in bytes per second.
  • in-traffic-peak-throughput: Inbound traffic peak throughput 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-throughput: Outbound traffic average throughput in bytes per second.
  • out-traffic-peak-throughput: Outbound traffic peak throughput in bytes per second.
  • discontinuity-time: The time of 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. The time format used is following the rules in Section 5.6 of [RFC3339].

6.7. NSF Counters

NSF counters have the following characteristics:

  • acquisition-method: subscription or query
  • emission-type: periodic
  • dampening-type: no-dampening

6.7.1. Firewall Counter

Firewall counters provide visibility into traffic signatures and bandwidth usage that correspond to the policy that is configured in a firewall.

  • policy-name: Security policy name that traffic matches.
  • measurement-time: The duration of the measurement in seconds for the calculation of statistics such as traffic rate and throughput. The statistic attributes are measured over the past measurement duration before now.
  • in-interface: Inbound interface of traffic.
  • out-interface: Outbound interface of traffic.
  • total-traffic: The total number of traffic packets (in and out) in the firewall.
  • 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-throughput: Inbound traffic average throughput in bytes per second.
  • in-traffic-peak-throughput: Inbound traffic peak throughput 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-throughput: Outbound traffic average throughput in bytes per second.
  • out-traffic-peak-throughput: Outbound traffic peak throughput 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. The time format used is following the rules in Section 5.6 of [RFC3339].

6.7.2. Policy Hit Counter

Policy hit counters record the security policy that traffic matches and its hit count. That is, when a packet actually matches a policy, it should be added to the statistics of a "policy hit counter" of the policy. The "policy hit counter" provides the "policy-name" that matches the policy's name in the NSF-Facing Interface YANG data model [I-D.ietf-i2nsf-nsf-facing-interface-dm]. It can check if policy configurations are correct or not.

  • 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. The time format used is following the rules in Section 5.6 of [RFC3339].

7. YANG Tree Structure of NSF Monitoring YANG Module

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


module: ietf-i2nsf-monitoring-interface
  +--ro i2nsf-counters
  |  +--ro vendor-name?          string
  |  +--ro device-model?         string
  |  +--ro software-version?     string
  |  +--ro nsf-name              union
  |  +--ro timestamp?            yang:date-and-time
  |  +--ro acquisition-method?   identityref
  |  +--ro emission-type?        identityref
  |  +--ro system-interface* [interface-name]
  |  |  +--ro interface-name                    if:interface-ref
  |  |  +--ro protocol?                         identityref
  |  |  +--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 measurement-time?                 uint32
  |  |  +--ro total-traffic?                    yang:counter64
  |  |  +--ro in-traffic-average-rate?          uint64
  |  |  +--ro in-traffic-peak-rate?             uint64
  |  |  +--ro in-traffic-average-throughput?    uint64
  |  |  +--ro in-traffic-peak-throughput?       uint64
  |  |  +--ro out-traffic-average-rate?         uint64
  |  |  +--ro out-traffic-peak-rate?            uint64
  |  |  +--ro out-traffic-average-throughput?   uint64
  |  |  +--ro out-traffic-peak-throughput?      uint64
  |  +--ro nsf-firewall* [policy-name]
  |  |  +--ro in-interface?                     if:interface-ref
  |  |  +--ro out-interface?                    if:interface-ref
  |  |  +--ro policy-name     -> /i2nsfnfi:i2nsf-security-policy/name
  |  |  +--ro discontinuity-time                yang:date-and-time
  |  |  +--ro measurement-time?                 uint32
  |  |  +--ro total-traffic?                    yang:counter64
  |  |  +--ro in-traffic-average-rate?          uint64
  |  |  +--ro in-traffic-peak-rate?             uint64
  |  |  +--ro in-traffic-average-throughput?    uint64
  |  |  +--ro in-traffic-peak-throughput?       uint64
  |  |  +--ro out-traffic-average-rate?         uint64
  |  |  +--ro out-traffic-peak-rate?            uint64
  |  |  +--ro out-traffic-average-throughput?   uint64
  |  |  +--ro out-traffic-peak-throughput?      uint64
  |  +--ro nsf-policy-hits* [policy-name]
  |     +--ro policy-name     -> /i2nsfnfi:i2nsf-security-policy/name
  |     +--ro discontinuity-time    yang:date-and-time
  |     +--ro hit-times?            yang:counter64
  +--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?   centiseconds
     +--rw i2nsf-system-detection-event
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-traffic-flows
     |  +--rw dampening-period?   centiseconds
     |  +--rw enabled?            boolean
     +--rw i2nsf-nsf-detection-ddos {i2nsf-nsf-detection-ddos}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-detection-virus {i2nsf-nsf-detection-virus}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-detection-session-table
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-detection-intrusion
                                     {i2nsf-nsf-detection-intrusion}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-detection-web-attack
                                    {i2nsf-nsf-detection-web-attack}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-detection-voip-vocn
                                     {i2nsf-nsf-detection-voip-vocn}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-system-access-log
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-system-res-util-log
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-system-user-activity-log
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-nsf-log-dpi {i2nsf-nsf-log-dpi}?
     |  +--rw enabled?            boolean
     |  +--rw dampening-period?   centiseconds
     +--rw i2nsf-counter
        +--rw period?   uint16

  notifications:
    +---n i2nsf-event
    |  +--ro vendor-name?                               string
    |  +--ro device-model?                              string
    |  +--ro software-version?                          string
    |  +--ro nsf-name                                   union
    |  +--ro message?                                   string
    |  +--ro language?                                  string
    |  +--ro acquisition-method?                        identityref
    |  +--ro emission-type?                             identityref
    |  +--ro dampening-type?                            identityref
    |  +--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 severity?          severity
    |     |     +--ro usage?             uint8
    |     |     +--ro threshold?         uint8
    |     +--:(i2nsf-system-detection-event)
    |     |  +--ro i2nsf-system-detection-event
    |     |     +--ro event-category?   identityref
    |     |     +--ro user              string
    |     |     +--ro group*            string
    |     |     +--ro ip-address        inet:ip-address-no-zone
    |     |     +--ro l4-port-number    inet:port-number
    |     |     +--ro authentication?   identityref
    |     |     +--ro changes* [policy-name]
    |     |        +--ro policy-name
                              -> /i2nsfnfi:i2nsf-security-policy/name
    |     +--:(i2nsf-traffic-flows)
    |     |  +--ro i2nsf-traffic-flows
    |     |     +--ro interface-name?       if:interface-ref
    |     |     +--ro interface-type?       enumeration
    |     |     +--ro src-mac?              yang:mac-address
    |     |     +--ro dst-mac?              yang:mac-address
    |     |     +--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 measurement-time?     uint32
    |     |     +--ro arrival-rate?         uint64
    |     |     +--ro arrival-throughput?   uint64
    |     +--:(i2nsf-nsf-detection-session-table)
    |        +--ro i2nsf-nsf-detection-session-table
    |           +--ro current-session?   uint32
    |           +--ro maximum-session?   uint32
    |           +--ro threshold?         uint32
    +---n i2nsf-log
    |  +--ro vendor-name?                            string
    |  +--ro device-model?                           string
    |  +--ro software-version?                       string
    |  +--ro nsf-name                                union
    |  +--ro message?                                string
    |  +--ro language?                               string
    |  +--ro acquisition-method?                     identityref
    |  +--ro emission-type?                          identityref
    |  +--ro dampening-type?                         identityref
    |  +--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 l4-port-number    inet:port-number
    |     |     +--ro authentication?   identityref
    |     |     +--ro operation-type?   operation-type
    |     |     +--ro input?            string
    |     |     +--ro output?           string
    |     +--:(i2nsf-system-res-util-log)
    |     |  +--ro i2nsf-system-res-util-log
    |     |     +--ro system-status?   enumeration
    |     |     +--ro cpu-usage?       uint8
    |     |     +--ro memory-usage?    uint8
    |     |     +--ro disks* [disk-id]
    |     |     |  +--ro disk-id            string
    |     |     |  +--ro disk-usage?        uint8
    |     |     |  +--ro disk-space-left?   uint8
    |     |     +--ro session-num?     uint32
    |     |     +--ro process-num?     uint32
    |     |     +--ro interface* [interface-id]
    |     |        +--ro interface-id              string
    |     |        +--ro in-traffic-rate?          uint64
    |     |        +--ro out-traffic-rate?         uint64
    |     |        +--ro in-traffic-throughput?    uint64
    |     |        +--ro out-traffic-throughput?   uint64
    |     +--:(i2nsf-system-user-activity-log)
    |     |  +--ro i2nsf-system-user-activity-log
    |     |     +--ro user               string
    |     |     +--ro group*             string
    |     |     +--ro ip-address         inet:ip-address-no-zone
    |     |     +--ro l4-port-number     inet:port-number
    |     |     +--ro authentication?    identityref
    |     |     +--ro online-duration?   uint32
    |     |     +--ro logout-duration?   uint32
    |     |     +--ro additional-info
    |     |        +--ro type?    enumeration
    |     |        +--ro cause?   string
    |     +--:(i2nsf-nsf-log-dpi) {i2nsf-nsf-log-dpi}?
    |        +--ro i2nsf-nsf-log-dpi
    |           +--ro attack-type?   identityref
    |           +--ro src-ip?        inet:ip-address-no-zone
    |           +--ro src-port?      inet:port-number
    |           +--ro dst-ip?        inet:ip-address-no-zone
    |           +--ro dst-port?      inet:port-number
    |           +--ro rule-name
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
    |           +--ro action*        identityref
    +---n i2nsf-nsf-event
       +--ro vendor-name?                            string
       +--ro device-model?                           string
       +--ro software-version?                       string
       +--ro nsf-name                                union
       +--ro message?                                string
       +--ro language?                               string
       +--ro acquisition-method?                     identityref
       +--ro emission-type?                          identityref
       +--ro dampening-type?                         identityref
       +--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
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
          |     +--ro attack-rate?         uint64
          |     +--ro attack-throughput?   uint64
          +--:(i2nsf-nsf-detection-virus)
                                         {i2nsf-nsf-detection-virus}?
          |  +--ro i2nsf-nsf-detection-virus
          |     +--ro src-ip?       inet:ip-address-no-zone
          |     +--ro src-port?     inet:port-number
          |     +--ro dst-ip?       inet:ip-address-no-zone
          |     +--ro dst-port?     inet:port-number
          |     +--ro rule-name
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
          |     +--ro virus-name?   string
          |     +--ro virus-type?   identityref
          |     +--ro host?         union
          |     +--ro file-type?    string
          |     +--ro file-name?    string
          |     +--ro os?           string
          +--:(i2nsf-nsf-detection-intrusion)
                                     {i2nsf-nsf-detection-intrusion}?
          |  +--ro i2nsf-nsf-detection-intrusion
          |     +--ro src-ip?        inet:ip-address-no-zone
          |     +--ro src-port?      inet:port-number
          |     +--ro dst-ip?        inet:ip-address-no-zone
          |     +--ro dst-port?      inet:port-number
          |     +--ro rule-name
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
          |     +--ro protocol?      identityref
          |     +--ro app?           identityref
          |     +--ro attack-type?   identityref
          +--:(i2nsf-nsf-detection-web-attack)
                                    {i2nsf-nsf-detection-web-attack}?
          |  +--ro i2nsf-nsf-detection-web-attack
          |     +--ro src-ip?           inet:ip-address-no-zone
          |     +--ro src-port?         inet:port-number
          |     +--ro dst-ip?           inet:ip-address-no-zone
          |     +--ro dst-port?         inet:port-number
          |     +--ro rule-name
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
          |     +--ro attack-type?      identityref
          |     +--ro req-method?       identityref
          |     +--ro req-target?       string
          |     +--ro filtering-type*   identityref
          |     +--ro cookies?          string
          |     +--ro req-host?         string
          |     +--ro response-code?    string
          +--:(i2nsf-nsf-detection-voip-vocn)
                                     {i2nsf-nsf-detection-voip-vocn}?
             +--ro i2nsf-nsf-detection-voip-vocn
                +--ro src-ip?                 inet:ip-address-no-zone
                +--ro src-port?               inet:port-number
                +--ro dst-ip?                 inet:ip-address-no-zone
                +--ro dst-port?               inet:port-number
                +--ro rule-name
                        -> /i2nsfnfi:i2nsf-security-policy/rules/name
                +--ro source-voice-id*        string
                +--ro destination-voice-id*   string
                +--ro user-agent*             string
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] [RFC0826] [RFC0854] [RFC1939] [RFC0959] [RFC2595] [RFC4340] [RFC4443] [RFC4861] [RFC5321] [RFC5646] [RFC6242] [RFC6265] [RFC8200] [RFC8641] [RFC9051] [I-D.ietf-httpbis-http2bis] [I-D.ietf-httpbis-messaging] [I-D.ietf-httpbis-semantics] [I-D.ietf-tcpm-rfc793bis] [I-D.ietf-tsvwg-rfc4960-bis] [IANA-HTTP-Status-Code] [IEEE-802.1AB]

<CODE BEGINS> file "ietf-i2nsf-monitoring-interface@2022-05-23.yang"

module ietf-i2nsf-monitoring-interface {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-i2nsf-monitoring-interface";
  prefix
    i2nsfmi;
  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-nsf-facing-interface {
    prefix i2nsfnfi;
    reference
      "Section 4.1 of draft-ietf-i2nsf-nsf-facing-interface-dm-28";
  }
  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 Revised 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 "2022-05-23" {
    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 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.";
  }

  typedef centiseconds {
    type uint32;
    description
      "A period of time, measured in units of 0.01 seconds.";
  }

  /*
   * 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 dampening-type {
    base characteristics;
    description
      "The type of message dampening to stop the rapid transmission
       of messages, such as 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
      "Memory is the hardware to store information temporarily or for
       a short period, i.e., Random Access Memory (RAM). A
       memory-alarm is emitted when the memory usage is exceeding
       the threshold.";
  }
  identity cpu-alarm {
    base system-alarm;
    description
      "CPU is the Central Processing Unit that executes basic
       operations of the system. A cpu-alarm is emitted when the CPU
       usage is exceeding a threshold.";
  }
  identity disk-alarm {
    base system-alarm;
    description
      "Disk or storage is the hardware to store information for a
       long period, i.e., Hard Disk and Solid-State Drive. A
       disk-alarm is emitted when the disk usage is exceeding a
       threshold.";
  }
  identity hardware-alarm {
    base system-alarm;
    description
      "A hardware alarm is emitted when a hardware failure (e.g.,
       CPU, memory, disk, or interface) is detected. A hardware
       failure is a malfunction within the electronic circuits or
       electromechanical components of the hardware that makes it
       unusable.";
  }
  identity interface-alarm {
    base system-alarm;
    description
      "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.";
  }

  identity access-violation {
    base system-event;
    description
      "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 (i.e., not-conformant
       with the access profile).";
  }
  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 tls-flood {
    base ddos-type;
    description
      "A Transport Layer Security (TLS) 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
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method PUT";
  }
  identity post {
    base req-method;
    description
      "The detected request type is POST.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method POST";
  }
  identity get {
    base req-method;
    description
      "The detected request type is GET.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method GET";
  }
  identity head {
    base req-method;
    description
      "The detected request type is HEAD.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method HEAD";
  }
  identity delete {
    base req-method;
    description
      "The detected request type is DELETE.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method DELETE";
  }
  identity connect {
    base req-method;
    description
      "The detected request type is CONNECT.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method CONNECT";
  }
  identity options {
    base req-method;
    description
      "The detected request type is OPTIONS.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - Request Method OPTIONS";
  }
  identity trace {
    base req-method;
    description
      "The detected request type is TRACE.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       - 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 dpi-type {
    description
      "Base identity for the type of Deep Packet Inspection (DPI).";
  }
  identity file-blocking {
    base dpi-type;
    description
      "DPI for preventing the specified file types from flowing
       in the network.";
  }
  identity data-filtering {
    base dpi-type;
    description
      "DPI for preventing sensitive information (e.g., Credit
       Card Number or Social Security Numbers) leaving a
       protected network.";
  }
  identity application-behavior-control {
    base dpi-type;
    description
      "DPI for filtering packet based on the application or
       network behavior analysis to identify malicious or
       unusual activity.";
  }

  identity protocol {
    description
      "An identity used to enable type choices in leaves
       and leaf-lists 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
      "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
      "draft-ietf-tsvwg-rfc4960-bis-18: 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. Note that a subset of
       application protocols (e.g., HTTP, HTTPS, FTP, POP3, and
       IMAP) are handled in this YANG module, rather than all
       the existing application protocols.";
  }
  identity http {
    base application-protocol;
    description
      "The identity for Hypertext Transfer Protocol version 1.1
       (HTTP/1.1).";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       draft-ietf-httpbis-messaging-19: HTTP/1.1";
  }
  identity https {
    base application-protocol;
    description
      "The identity for Hypertext Transfer Protocol version 1.1
       (HTTP/1.1) over TLS.";
    reference
      "draft-ietf-httpbis-semantics-19: HTTP Semantics
       draft-ietf-httpbis-messaging-19: HTTP/1.1";
  }
  identity http2 {
    base application-protocol;
    description
      "The identity for Hypertext Transfer Protocol version 2
       (HTTP/2).";
    reference
      "draft-ietf-httpbis-http2bis-07: HTTP/2";
  }
  identity https2 {
    base application-protocol;
    description
      "The identity for Hypertext Transfer Protocol version 2
       (HTTP/2) over TLS.";
    reference
      "draft-ietf-httpbis-http2bis-07: HTTP/2";
  }
  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 Post Office Protocol 3 (POP3).";
    reference
      "RFC 1939: Post Office Protocol - Version 3 (POP3)";
  }
  identity pop3s {
    base application-protocol;
    description
      "The identity for Post Office Protocol 3 (POP3) over TLS";
    reference
      "RFC 1939: Post Office Protocol - Version 3 (POP3)
       RFC 2595: Using TLS with IMAP, POP3 and ACAP";
  }
  identity imap {
    base application-protocol;
    description
      "The identity for Internet Message Access Protocol (IMAP).";
    reference
      "RFC 9051: Internet Message Access Protocol (IMAP) - Version
       4rev2";
  }
  identity imaps {
    base application-protocol;
    description
      "The identity for Internet Message Access Protocol (IMAP) over
       TLS";
    reference
      "RFC 9051: Internet Message Access Protocol (IMAP) - Version
       4rev2
       RFC 2595: Using TLS with IMAP, POP3 and ACAP";
  }

  /*
   * 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 message {
    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 language {
      type string {
        pattern '(([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}))+)*(-[Xx](-([A-Za-z0-9]'
              + '{1,8}))+)?|[Xx](-([A-Za-z0-9]{1,8}))+|'
              + '(([Ee][Nn]-[Gg][Bb]-[Oo][Ee][Dd]|[Ii]-'
              + '[Aa][Mm][Ii]|[Ii]-[Bb][Nn][Nn]|[Ii]-'
              + '[Dd][Ee][Ff][Aa][Uu][Ll][Tt]|[Ii]-'
              + '[Ee][Nn][Oo][Cc][Hh][Ii][Aa][Nn]'
              + '|[Ii]-[Hh][Aa][Kk]|'
              + '[Ii]-[Kk][Ll][Ii][Nn][Gg][Oo][Nn]|'
              + '[Ii]-[Ll][Uu][Xx]|[Ii]-[Mm][Ii][Nn][Gg][Oo]|'
              + '[Ii]-[Nn][Aa][Vv][Aa][Jj][Oo]|[Ii]-[Pp][Ww][Nn]|'
              + '[Ii]-[Tt][Aa][Oo]|[Ii]-[Tt][Aa][Yy]|'
              + '[Ii]-[Tt][Ss][Uu]|[Ss][Gg][Nn]-[Bb][Ee]-[Ff][Rr]|'
              + '[Ss][Gg][Nn]-[Bb][Ee]-[Nn][Ll]|[Ss][Gg][Nn]-'
              + '[Cc][Hh]-[Dd][Ee])|([Aa][Rr][Tt]-'
              + '[Ll][Oo][Jj][Bb][Aa][Nn]|[Cc][Ee][Ll]-'
              + '[Gg][Aa][Uu][Ll][Ii][Ss][Hh]|'
              + '[Nn][Oo]-[Bb][Oo][Kk]|[Nn][Oo]-'
              + '[Nn][Yy][Nn]|[Zz][Hh]-[Gg][Uu][Oo][Yy][Uu]|'
              + '[Zz][Hh]-[Hh][Aa][Kk][Kk][Aa]|[Zz][Hh]-'
              + '[Mm][Ii][Nn]|[Zz][Hh]-[Mm][Ii][Nn]-'
              + '[Nn][Aa][Nn]|[Zz][Hh]-[Xx][Ii][Aa][Nn][Gg])))';
      }
      default "en-US";
      description
        "The value in this field indicates the language tag
         used for the human readable fields (i.e., '../message',
         '/i2nsf-log/i2nsf-nsf-system-access-log/output', and
         '/i2nsf-log/i2nsf-system-user-activity-log/additional-info
         /cause').
         The attribute is encoded following the rules in Section 2.1
         in RFC 5646. The default language tag is 'en-US'";
      reference
        "RFC 5646: Tags for Identifying Languages";
    }
  }

  grouping common-monitoring-data {
    description
      "A set of common monitoring data that is needed
      as the basic information.";

    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 device-model {
      type string;
      description
        "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.";
    }
    leaf software-version {
      type string;
      description
        "The version of the software used to provide the security
         service";
    }
    leaf nsf-name {
      type union {
        type string;
        type inet:ip-address-no-zone;
      }
      mandatory true;
      description
        "The name or IP address of the NSF generating the message.
         If the given nsf-name is not an IP address, the name can be
         an arbitrary string including a 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.";
    }
  }
  grouping characteristics {
    description
      "A set of characteristics of a monitoring information.";
    leaf acquisition-method {
      type identityref {
        base acquisition-method;
      }
      description
        "The acquisition-method for characteristics";
    }
    leaf emission-type {
      when "derived-from-or-self(../acquisition-method, "
         + "'i2nsfmi:subscription')";
      type identityref {
        base emission-type;
      }
      description
        "The emission-type for characteristics. This attribute is
         used only when the acquisition-method is a 'subscription'";
    }
  }
  grouping characteristics-extended {
    description
      "An extended characteristics for the monitoring information.";
    uses 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 l4-port-number {
      type inet:port-number;
      mandatory true;
      description
        "The transport layer 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 or 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
          "/i2nsfnfi:i2nsf-security-policy"
         +"/i2nsfnfi:rules/i2nsfnfi: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";
    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";
    }
    uses i2nsf-nsf-event-type-content;
  }
  grouping action {
    description
      "A grouping for action.";
    leaf-list action {
      type identityref {
        base i2nsfnfi:ingress-action;
      }
      description
        "Action type: pass, drop, reject, mirror, or rate limit";
    }
  }
  grouping attack-rates {
    description
      "A set of traffic rates for monitoring attack traffic
       data";
    leaf attack-rate {
      type uint64;
      units "pps";
      description
        "The average packets per second (pps) rate of attack
         traffic";
    }
    leaf attack-throughput {
      type uint64;
      units "Bps";
      description
        "The average bytes per second (Bps) throughput 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 measurement-time {
      type uint32;
      units "seconds";
      description
        "The time of the measurement in seconds for the
         calculation of statistics such as traffic rate and
         throughput. The statistic attributes are measured over
         the past measurement duration before now.";
    }
    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 uint64;
      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 uint64;
      units "pps";
      description
        "Inbound traffic peak rate in packets per second (pps).";
    }
    leaf in-traffic-average-throughput {
      type uint64;
      units "Bps";
      description
        "Inbound traffic average throughput 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-throughput {
      type uint64;
      units "Bps";
      description
        "Inbound traffic peak throughput in bytes per second (Bps).";
    }
    leaf out-traffic-average-rate {
      type uint64;
      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 uint64;
      units "pps";
      description
       "Outbound traffic peak rate in packets per second (pps).";
    }
    leaf out-traffic-average-throughput {
      type uint64;
      units "Bps";
      description
        "Outbound traffic average throughput 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-throughput {
      type uint64;
      units "Bps";
      description
        "Outbound traffic peak throughput 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 protocol {
      type identityref {
        base protocol;
      }
      description
        "The type of network protocol for the interface counter.
         If this field is empty, then the counter includes all
         protocols (e.g., IPv4, IPv6, TCP, and UDP)";
    }
    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
          "/i2nsfnfi:i2nsf-security-policy"
         +"/i2nsfnfi:name";
      }
      mandatory true;
      description
        "The name of the policy being triggered";
    }
  }

  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 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-vocn {
    description
      "This feature means it supports I2NSF nsf-detection-voip-vocn
       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. This notification provides
       general information that can be supported by most types of
       NSFs.";

    uses common-monitoring-data;
    uses message;
    uses characteristics-extended;

    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 {
            when "derived-from-or-self(../alarm-category, "
               + "'i2nsfmi:interface-alarm')";
            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 {
            when "derived-from-or-self(../alarm-category, "
               + "'i2nsfmi:interface-alarm')";
            type enumeration {
              enum up {
                value 1;
                description
                  "The interface state is up and not congested.
                   The interface is ready to pass packets.";
              }
              enum down {
                value 2;
                description
                  "The interface state is down, i.e., does not pass
                   any packets.";
              }
              enum congested {
                value 3;
                description
                  "The interface state is up but congested.";
              }
              enum testing {
                value 4;
                description
                  "In some test mode.  No operational packets can
                   be passed.";
              }
              enum unknown {
                value 5;
                description
                  "Status cannot be determined for some reason.";
              }
              enum dormant {
                value 6;
                description
                  "Waiting for some external event.";
               }
              enum not-present {
                value 7;
                description
                  "Some component (typically hardware) is missing.";
              }
              enum lower-layer-down {
                value 8;
                description
                  "Down due to state of lower-layer interface(s).";
              }
            }
            description
              "The state of the interface. Applicable for Network
               Interface Failure Alarm.";
            reference
              "RFC 8343: A YANG Data Model for Interface Management -
               Operational States";
          }
          leaf severity {
            type severity;
            description
              "The severity of the alarm such as critical, high,
               middle, and low.";
          }
          uses i2nsf-system-alarm-type-content;
        }
      }

      case i2nsf-system-detection-event {
        container i2nsf-system-detection-event {
          description
            "This notification is sent when an event in the system is
             detected, such as access violation and configuration
             change";
          leaf event-category {
            type identityref {
              base system-event;
            }
            description
              "The event category for system-detection-event";
          }
          uses i2nsf-system-event-type-content;
          list changes {
            when "derived-from-or-self(../event-category, "
               + "'i2nsfmi:configuration-change')";
            key policy-name;
            description
              "Describes the modification that was made to the
               configuration. This list is only applicable when the
               event is 'configuration-change'.
               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
                  "/i2nsfnfi:i2nsf-security-policy"
                 +"/i2nsfnfi: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 interface-name {
            type if:interface-ref;
            description
              "The mnemonic name of the network interface";
          }
          leaf interface-type {
            type enumeration {
              enum ingress {
                description
                  "The corresponding interface-name indicates an
                   ingress interface.";
              }
              enum egress {
                description
                  "The corresponding interface-name indicates an
                   egress interface.";
              }
            }
            description
              "The type of a network interface such as an ingress or
               egress interface.";
          }
          leaf src-mac {
            type yang:mac-address;
            description
              "The source MAC address of the traffic flow. This
               information may or may not be included depending on
               the type of traffic flow. For example, the information
               will be useful and should be included if the traffic
               flows are traffic flows of Link Layer Discovery
               Protocol (LLDP), Address Resolution Protocol (ARP) for
               IPv4, and Neighbor Discovery Protocol (ND) for IPv6.";
            reference
              "IEEE-802.1AB: IEEE Standard for Local and metropolitan
               area networks - Station and Media Access Control
               Connectivity Discovery - Link Layer Discovery Protocol
               (LLDP)
               RFC 826: An Ethernet Address Resolution Protocol -
               Address Resolution Protocol (ARP)
               RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
               Neighbor Discovery Protocol (ND)";
          }
          leaf dst-mac {
            type yang:mac-address;
            description
              "The destination MAC address of the traffic flow. This
               information may or may not be included depending on
               the type of traffic flow. For example, the information
               will be useful and should be included if the traffic
               flows are traffic flows of Link Layer Discovery
               Protocol (LLDP), Address Resolution Protocol (ARP) for
               IPv4, and Neighbor Discovery Protocol (ND) for IPv6.";
            reference
              "IEEE-802.1AB: IEEE Standard for Local and metropolitan
               area networks - Station and Media Access Control
               Connectivity Discovery - Link Layer Discovery Protocol
               (LLDP)
               RFC 826: An Ethernet Address Resolution Protocol -
               Address Resolution Protocol (ARP)
               RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
               Neighbor Discovery Protocol (ND)";
          }
          leaf src-ip {
            type inet:ip-address-no-zone;
            description
              "The source IPv4 or IPv6 address of the traffic flow";
          }
          leaf dst-ip {
            type inet:ip-address-no-zone;
            description
              "The destination IPv4 or IPv6 address of the traffic
               flow";
          }
          leaf protocol {
            type identityref {
              base protocol;
            }
            description
              "The protocol type of a traffic flow";
          }
          leaf src-port {
            type inet:port-number;
            description
              "The transport layer source port number of the flow";
          }
          leaf dst-port {
            type inet:port-number;
            description
              "The transport layer destination port number of the
               flow";
          }
          leaf measurement-time {
            type uint32;
            units "seconds";
            description
              "The duration of the measurement in seconds for the
               arrival rate and arrival throughput of packets of a
               traffic flow. These two metrics (i.e., arrival rate
               and arrival throughput) are measured over the past
               measurement duration before now.";
          }
          leaf arrival-rate {
            type uint64;
            units "pps";
            description
              "The arrival rate of packets of the traffic flow in
               packets per second measured over the past
               'measurement-time'.";
          }
          leaf arrival-throughput {
            type uint64;
            units "Bps";
            description
              "The arrival rate of packets of the traffic flow in
               bytes per second measured over the past
               'measurement-time'.";
          }
        }
      }

      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";
          }
        }
      }
    }
  }

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

    uses common-monitoring-data;
    uses message;
    uses characteristics-extended;

    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.";
          }
        }
      }

      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 disks {
            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-space-left {
              type uint8;
              units "percent";
              description
                "Specifies the percentage of disk space 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 uint64;
              units "pps";
              description
                "The total inbound traffic rate in packets per
                 second";
            }
            leaf out-traffic-rate {
              type uint64;
              units "pps";
              description
                 "The total outbound traffic rate in packets per
                  second";
            }
            leaf in-traffic-throughput {
              type uint64;
              units "Bps";
              description
                "The total inbound traffic throughput in bytes per
                 second";
            }
            leaf out-traffic-throughput {
              type uint64;
              units "Bps";
              description
                "The total outbound traffic throughput in bytes per
                 second";
            }
          }
        }
      }

      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 i2nsf-system-event-type-content;
          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.";
          }
          container additional-info {
            leaf type {
              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.";
            }
            leaf cause {
              type string;
              description
                "The cause of a failed user activity related to the
                 type of user activity. For example, when the 'type'
                 is failed-login, the value of this attribute can be
                 'Failed login attempt due to wrong password
                 entry'.";
            }
            description
              "The additional information about user activity.";
          }
        }
      }
      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 identityref {
              base dpi-type;
            }
            description
              "The type of the DPI";
          }
          uses i2nsf-nsf-event-type-content-extend;
          uses action;
        }
      }
    }
  }

  notification i2nsf-nsf-event {
    description
      "Notification for I2NSF NSF Event. This notification provides
       specific information that can only be provided by an NSF
       that supports additional features (e.g., DDoS attack
       detection).";

    uses common-monitoring-data;
    uses message;
    uses characteristics-extended;

    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 omitted.";
          }
          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. Note that all IP addresses should not be
               included, but only limited IP addresses are included
               to conserve the server resources. The listed attacking
               IP addresses can be an arbitrary sampling of the
               'top talkers', i.e., the attackers that send the
               highest amount of traffic.";
          }
          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 transport-layer source ports of the DDoS attack.
               Note that not all ports will have been seen on all the
               corresponding source IP addresses.";
          }
          leaf-list attack-dst-port {
            type inet:port-number;
            description
              "The transport-layer destination ports of the DDoS
               attack. Note that not all ports will have been seen
               on all the corresponding destination IP addresses.";
          }
          leaf rule-name {
            type leafref {
              path
                "/i2nsfnfi:i2nsf-security-policy"
               +"/i2nsfnfi:rules/i2nsfnfi:name";
            }
            mandatory true;
            description
              "The name of the I2NSF Policy Rule being triggered";
          }

          uses attack-rates;
        }
      }
      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 an IP address, the
               name can be an arbitrary string including a 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 a file (indicated by the file's suffix,
               e.g., .exe) where virus code is found (if
               applicable).";
          }
          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.";
          }
        }
      }
      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";
          }
        }
      }
      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
              "draft-ietf-httpbis-semantics-19: HTTP Semantics -
               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
              "draft-ietf-httpbis-messaging-19: HTTP/1.1 - Request
               Target";
          }
          leaf-list filtering-type {
            type identityref {
              base filter-type;
            }
            description
              "URL filtering type, e.g., deny-list, allow-list,
               and Unknown";
          }
          leaf cookies {
            type string;
            description
              "The HTTP Cookies header field of the request from
               the user agent. Note that though cookies have many
               historical infelicities that degrade security and
               privacy, the Cookie and Set-Cookie header fields are
               widely used on the Internet. Thus, the cookie
               information needs to be kept confidential and is NOT
               RECOMMENDED to be included in the monitoring data
               unless the information is absolutely necessary to help
               to enhance the security of the network.";
            reference
              "RFC 6265: HTTP State Management Mechanism - Cookie";
          }
          leaf req-host {
            type string;
            description
              "The HTTP Host header field of the request";
            reference
              "draft-ietf-httpbis-semantics-19: HTTP Semantics - Host";
          }
          leaf response-code {
            type string;
            description
              "The HTTP Response status code";
            reference
              "IANA Website: Hypertext Transfer Protocol (HTTP)
               Status Code Registry";
          }
        }
      }
      case i2nsf-nsf-detection-voip-vocn {
        if-feature "i2nsf-nsf-detection-voip-vocn";
        container i2nsf-nsf-detection-voip-vocn {
          description
            "This notification is sent, when a VoIP/VoCN 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 VoCN that
               violates the security policy.";
          }
          leaf-list destination-voice-id {
            type string;
            description
              "The detected destination voice ID for VoIP and VoCN
               that violates the security policy.";
          }
          leaf-list user-agent {
            type string;
            description
              "The detected user-agent for VoIP and VoCN that
               violates the security policy.";
          }
        }
      }
    }
  }
  /*
   * 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.";

    uses common-monitoring-data;
    uses timestamp;
    uses characteristics;

    list system-interface {
      key interface-name;
      description
        "Interface counters provide the visibility of traffic into
         and out of an NSF, and bandwidth usage.";
      uses i2nsf-system-counter-type-content;
    }
    list nsf-firewall {
      key policy-name;
      description
        "Firewall counters provide visibility into traffic signatures
         and bandwidth usage that correspond to the policy that is
         configured in a firewall.";
      leaf in-interface {
        type if:interface-ref;
        description
          "Inbound interface of the traffic";
      }
      leaf out-interface {
        type if:interface-ref;
        description
          "Outbound interface of the traffic";
      }
      uses i2nsf-nsf-counters-type-content;
      uses traffic-rates;
    }
    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 i2nsf-nsf-counters-type-content;
      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.";
      }
    }
  }

  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-virus {
      if-feature "i2nsf-nsf-detection-virus";
      description
        "The container for configuring I2NSF nsf-detection-virus
         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-detection-voip-vocn {
      if-feature "i2nsf-nsf-detection-voip-vocn";
      description
        "The container for configuring I2NSF nsf-detection-voip-vocn
         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 an 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. The XML examples are following the guidelines from [RFC6241] [RFC7950].

10.1. I2NSF System Detection Alarm

The following example shows an alarm triggered by Memory Usage on the server; 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-monitoring-interface">
    <acquisition-method>subscription</acquisition-method>
    <emission-type>on-change</emission-type>
    <dampening-type>on-repetition</dampening-type>
    <language>en-US</language>
    <i2nsf-system-detection-alarm>
      <alarm-category>memory-alarm</alarm-category>
      <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-monitoring-interface">
      <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-monitoring-interface">
      <acquisition-method>query</acquisition-method>
      <system-interface>
        <discontinuity-time>
          2021-04-29T08:43:52.181088+00:00
        </discontinuity-time>
        <interface-name>ens3</interface-name>
        <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>
        <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-monitoring-interface
  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-monitoring-interface
  namespace: urn:ietf:params:xml:ns:yang:ietf-i2nsf-monitoring-interface
  prefix: i2nsfmi
  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 by 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. The following 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 it is an issue for all monitoring infrastructures. It is important to keep confidential information from 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; the entire detection and mitigation infrastructure may be suspect. It is important to keep confidential information from unauthorized persons to mitigate the possibility of compromising the NSF with this information.
Impersonating NSF:
This involves 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:
This 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 which 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-vocn" are privacy sensitive. They may describe specific or aggregate user activity including associating user names with specific IP addresses; or users with specific network usage. They may also describe the specific commands that were run by users and the resulting output. Any sensitive information in that command input or output will be visible to the NSF data collector and potentially other entities, and care must be taken to protect the confidentiality of such data from unauthorized parties.

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. The 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

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, Republic of Korea, Email: 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

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, , <https://www.rfc-editor.org/info/rfc768>.
[RFC0791]
Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 10.17487/RFC0791, , <https://www.rfc-editor.org/info/rfc791>.
[RFC0792]
Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, DOI 10.17487/RFC0792, , <https://www.rfc-editor.org/info/rfc792>.
[RFC0854]
Postel, J. and J. Reynolds, "Telnet Protocol Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, , <https://www.rfc-editor.org/info/rfc854>.
[RFC0959]
Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC 959, DOI 10.17487/RFC0959, , <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, , <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, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC2595]
Newman, C., "Using TLS with IMAP, POP3 and ACAP", RFC 2595, DOI 10.17487/RFC2595, , <https://www.rfc-editor.org/info/rfc2595>.
[RFC3339]
Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, , <https://www.rfc-editor.org/info/rfc3339>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <https://www.rfc-editor.org/info/rfc3688>.
[RFC3877]
Chisholm, S. and D. Romascanu, "Alarm Management Information Base (MIB)", RFC 3877, DOI 10.17487/RFC3877, , <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, , <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, , <https://www.rfc-editor.org/info/rfc4443>.
[RFC5277]
Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, , <https://www.rfc-editor.org/info/rfc5277>.
[RFC5321]
Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, DOI 10.17487/RFC5321, , <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, , <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, , <https://www.rfc-editor.org/info/rfc6241>.
[RFC6242]
Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, , <https://www.rfc-editor.org/info/rfc6242>.
[RFC6265]
Barth, A., "HTTP State Management Mechanism", RFC 6265, DOI 10.17487/RFC6265, , <https://www.rfc-editor.org/info/rfc6265>.
[RFC6991]
Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, , <https://www.rfc-editor.org/info/rfc6991>.
[RFC7011]
Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, , <https://www.rfc-editor.org/info/rfc7011>.
[RFC7950]
Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, , <https://www.rfc-editor.org/info/rfc7950>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <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, , <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, , <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, , <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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc8342>.
[RFC8343]
Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, , <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, , <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, , <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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc8641>.
[RFC8650]
Voit, E., Rahman, R., Nilsen-Nygaard, E., Clemm, A., and A. Bierman, "Dynamic Subscription to YANG Events and Datastores over RESTCONF", RFC 8650, DOI 10.17487/RFC8650, , <https://www.rfc-editor.org/info/rfc8650>.
[RFC9000]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, , <https://www.rfc-editor.org/info/rfc9000>.
[RFC9051]
Melnikov, A., Ed. and B. Leiba, Ed., "Internet Message Access Protocol (IMAP) - Version 4rev2", RFC 9051, DOI 10.17487/RFC9051, , <https://www.rfc-editor.org/info/rfc9051>.
[I-D.ietf-httpbis-http2bis]
Thomson, M. and C. Benfield, "HTTP/2", Work in Progress, Internet-Draft, draft-ietf-httpbis-http2bis-07, , <https://www.ietf.org/archive/id/draft-ietf-httpbis-http2bis-07.txt>.
[I-D.ietf-httpbis-messaging]
Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP/1.1", Work in Progress, Internet-Draft, draft-ietf-httpbis-messaging-19, , <https://www.ietf.org/archive/id/draft-ietf-httpbis-messaging-19.txt>.
[I-D.ietf-httpbis-semantics]
Fielding, R. T., Nottingham, M., and J. Reschke, "HTTP Semantics", Work in Progress, Internet-Draft, draft-ietf-httpbis-semantics-19, , <https://www.ietf.org/archive/id/draft-ietf-httpbis-semantics-19.txt>.
[I-D.ietf-i2nsf-capability-data-model]
Hares, S., Jeong, J. P., Kim, J. T., Moskowitz, R., and Q. Lin, "I2NSF Capability YANG Data Model", Work in Progress, Internet-Draft, draft-ietf-i2nsf-capability-data-model-31, , <https://www.ietf.org/archive/id/draft-ietf-i2nsf-capability-data-model-31.txt>.
[I-D.ietf-i2nsf-nsf-facing-interface-dm]
Kim, J. T., Jeong, J. P., 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-27, , <https://www.ietf.org/archive/id/draft-ietf-i2nsf-nsf-facing-interface-dm-27.txt>.
[I-D.ietf-tcpm-rfc793bis]
Eddy, W. M., "Transmission Control Protocol (TCP) Specification", Work in Progress, Internet-Draft, draft-ietf-tcpm-rfc793bis-28, , <https://www.ietf.org/archive/id/draft-ietf-tcpm-rfc793bis-28.txt>.
[I-D.ietf-tsvwg-rfc4960-bis]
Stewart, R. R., Tüxen, M., and K. E. E. Nielsen, "Stream Control Transmission Protocol", Work in Progress, Internet-Draft, draft-ietf-tsvwg-rfc4960-bis-19, , <https://www.ietf.org/archive/id/draft-ietf-tsvwg-rfc4960-bis-19.txt>.

15.2. Informative References

[RFC0826]
Plummer, D., "An Ethernet Address Resolution Protocol: Or Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware", STD 37, RFC 826, DOI 10.17487/RFC0826, , <https://www.rfc-editor.org/info/rfc826>.
[RFC4861]
Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, , <https://www.rfc-editor.org/info/rfc4861>.
[RFC4949]
Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, DOI 10.17487/RFC4949, , <https://www.rfc-editor.org/info/rfc4949>.
[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, , <https://www.rfc-editor.org/info/rfc8792>.
[I-D.ietf-i2nsf-consumer-facing-interface-dm]
Jeong, J. P., 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-19, , <https://www.ietf.org/archive/id/draft-ietf-i2nsf-consumer-facing-interface-dm-19.txt>.
[IANA-HTTP-Status-Code]
Internet Assigned Numbers Authority (IANA), "Hypertext Transfer Protocol (HTTP) Status Code Registry", , <https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml>.
[IEEE-802.1AB]
Institute of Electrical and Electronics Engineers, "IEEE Standard for Local and metropolitan area networks - Station and Media Access Control Connectivity Discovery", , <https://ieeexplore.ieee.org/document/7433915>.

Appendix A. Changes from draft-ietf-i2nsf-nsf-monitoring-data-model-18

The following changes are made from draft-ietf-i2nsf-nsf-monitoring-data-model-18:

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
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
Susan Hares
Huawei
7453 Hickory Hill
Saline, MI 48176
United States of America
Phone: +1-734-604-0332
Liang Frank Xia
Huawei
101 Software Avenue, Yuhuatai District
Nanjing
Jiangsu,
China
Henk Birkholz
Fraunhofer Institute for Secure Information Technology
Rheinstrasse 75
64295 Darmstadt
Germany