RFC 9061 | IPsec Flow Protection Based on SDN | July 2021
Marin-Lopez, et al. | Standards Track | [Page]

Stream:
  Internet Engineering Task Force (IETF)
RFC:
  9061
Category:
  Standards Track
Published:
  July 2021
ISSN:
  2070-1721
Authors:
  R. Marin-Lopez
  University of Murcia
  G. Lopez-Millan
  University of Murcia
  F. Pereniguez-Garcia
  University Defense Center

# RFC 9061

# A YANG Data Model for IPsec Flow Protection Based on Software‑Defined Networking (SDN)

## Abstract

This document describes how to provide IPsec-based flow protection (integrity and confidentiality) by means of an Interface to Network Security Function (I2NSF) Controller. It considers two main well-known scenarios in IPsec: gateway-to-gateway and host-to-host. The service described in this document allows the configuration and monitoring of IPsec Security Associations (IPsec SAs) from an I2NSF Controller to one or several flow-based Network Security Functions (NSFs) that rely on IPsec to protect data traffic.¶

This document focuses on the I2NSF NSF-Facing Interface by providing YANG data models for configuring the IPsec databases, namely Security Policy Database (SPD), Security Association Database (SAD), Peer Authorization Database (PAD), and Internet Key Exchange Version 2 (IKEv2). This allows IPsec SA establishment with minimal intervention by the network administrator. This document defines three YANG modules, but it does not define any new protocol.¶

## Status of This Memo

This is an Internet Standards Track document.¶

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9061.¶

## Copyright Notice

Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.¶

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.¶

## 1. Introduction

Software-Defined Networking (SDN) is an architecture that enables administrators to directly program, orchestrate, control, and manage network resources through software. The SDN paradigm relocates the control of network resources to a centralized entity, namely the SDN Controller. SDN Controllers configure and manage distributed network resources and provide an abstracted view of the network resources to SDN applications. SDN applications can customize and automate the operations (including management) of the abstracted network resources in a programmable manner via this interface [RFC7149] [ITU-T.Y.3300] [ONF-SDN-Architecture] [ONF-OpenFlow].¶

Recently, several network scenarios now demand a centralized way of managing different security aspects, for example, Software-Defined WANs (SD-WANs). SD-WANs are SDN extensions providing software abstractions to create secure network overlays over traditional WAN and branch networks. SD-WANs utilize IPsec [RFC4301] as an underlying security protocol. The goal of SD-WANs is to provide flexible and automated deployment from a centralized point to enable on-demand network security services, such as IPsec Security Association (IPsec SA) management. Additionally, Section 4.3.3 ("Client-Specific Security Policy in Cloud VPNs") of [RFC8192] describes another example use case for a cloud data center scenario. The use case in [RFC8192] states that "dynamic key management is critical for securing the VPN and the distribution of policies". These VPNs can be established using IPsec. The management of IPsec SAs in data centers using a centralized entity is a scenario where the current specification may be applicable.¶

Therefore, with the growth of SDN-based scenarios where network resources are deployed in an autonomous manner, a mechanism to manage IPsec SAs from a centralized entity becomes more relevant in the industry.¶

In response to this need, the Interface to Network Security Functions (I2NSF) charter states that the goal of this working group is "to define a set of software interfaces and data models for controlling and monitoring aspects of physical and virtual NSFs". As defined in [RFC8192], a Network Security Function (NSF) is "a function that is used to ensure integrity, confidentiality, or availability of network communication; to detect unwanted network activity; or to block, or at least mitigate, the effects of unwanted activity". This document pays special attention to flow-based NSFs that ensure integrity and confidentiality by means of IPsec.¶

In fact, Section 3.1.9 of [RFC8192] states that "there is a need for a controller to create, manage, and distribute various keys to distributed NSFs"; however, "there is a lack of a standard interface to provision and manage security associations". Inspired by the SDN paradigm, the I2NSF framework [RFC8329] defines a centralized entity, the I2NSF Controller, which manages one or multiple NSFs through an I2NSF NSF-Facing Interface. In this document, an architecture is defined for allowing the I2NSF Controller to carry out the key management procedures. More specifically, three YANG data models are defined for the I2NSF NSF-Facing Interface, which allows the I2NSF Controller to configure and monitor IPsec-enabled, flow-based NSFs.¶

The IPsec architecture [RFC4301] defines a clear separation between the processing to provide security services to IP packets and the key management procedures to establish the IPsec SAs, which allows centralizing the key management procedures in the I2NSF Controller. This document considers two typical scenarios to autonomously manage IPsec SAs: gateway-to-gateway and host-to-host [RFC6071]. In these cases, hosts, gateways, or both may act as NSFs. Due to its complexity, consideration for the host-to-gateway scenario is out of scope. The source of this complexity comes from the fact that, in this scenario, the host may not be under the control of the I2NSF Controller and, therefore, it is not configurable. Nevertheless, the I2NSF interfaces defined in this document can be considered as a starting point to analyze and provide a solution for the host-to-gateway scenario.¶

For the definition of the YANG data models for the I2NSF NSF-Facing Interface, this document considers two general cases, namely:¶

1. IKE case. The NSF implements the Internet Key Exchange Version 2 (IKEv2) protocol and the IPsec databases: the Security Policy Database (SPD), the Security Association Database (SAD), and the Peer Authorization Database (PAD). The I2NSF Controller is in charge of provisioning the NSF with the required information in the SPD and PAD (e.g., IKE credentials) and the IKE protocol itself (e.g., parameters for the IKE_SA_INIT negotiation).¶
2. IKE-less case. The NSF only implements the IPsec databases (no IKE implementation). The I2NSF Controller will provide the required parameters to create valid entries in the SPD and the SAD of the NSF. Therefore, the NSF will only have support for IPsec whereas key management functionality is moved to the I2NSF Controller.¶

In both cases, a YANG data model for the I2NSF NSF-Facing Interface is required to carry out this provisioning in a secure manner between the I2NSF Controller and the NSF. Using YANG data modeling language version 1.1 [RFC7950] and based on YANG data models defined in [netconf-vpn] and [TRAN-IPSECME-YANG] and the data structures defined in [RFC4301] and [RFC7296], this document defines the required interfaces with a YANG data model for configuration and state data for IKE, PAD, SPD, and SAD (see Sections 5.1, 5.2, and 5.3). The proposed YANG data model conforms to the Network Management Datastore Architecture (NMDA) defined in [RFC8342]. Examples of the usage of these data models can be found in Appendices A, B, and C.¶

In summary, the objectives of this document are:¶

- To describe the architecture for I2NSF-based IPsec management, which allows for the establishment and management of IPsec Security Associations from the I2NSF Controller in order to protect specific data flows between two flow-based NSFs implementing IPsec.¶
- To map this architecture to the I2NSF framework.¶
- To define the interfaces required to manage and monitor the IPsec SAs in the NSF from an I2NSF Controller. YANG data models are defined for configuration and state data for IPsec and IKEv2 management through the I2NSF NSF-Facing Interface. The YANG data models can be used via existing protocols, such as the Network Configuration Protocol (NETCONF) [RFC6241] or RESTCONF [RFC8040]. Thus, this document defines three YANG modules (see Section 5) but does not define any new protocol.¶

## 2. Terminology

This document uses the terminology described in [ITU-T.Y.3300], [RFC8192], [RFC4301], [RFC6437], [RFC7296], [RFC6241], and [RFC8329].¶

The following term is defined in [ITU-T.Y.3300]:¶

- Software-Defined Networking (SDN)¶

The following terms are defined in [RFC8192]:¶

- Network Security Function (NSF)¶
- flow-based NSF¶

The following terms are defined in [RFC4301]:¶

- Peer Authorization Database (PAD)¶
- Security Association Database (SAD)¶
- Security Policy Database (SPD)¶

The following two terms are related or have identical definition/usage in [RFC6437]:¶

- flow¶
- traffic flow¶

The following term is defined in [RFC7296]:¶

- Internet Key Exchange Version 2 (IKEv2)¶

The following terms are defined in [RFC6241]:¶

- configuration data¶
- configuration datastore¶
- state data¶
- startup configuration datastore¶
- running configuration datastore¶

### 2.1. Requirements Language

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.¶

## 3. SDN-Based IPsec Management Description

As mentioned in Section 1, two cases are considered, depending on whether the NSF implements IKEv2 or not: the IKE case and the IKE-less case.¶

### 3.1. IKE Case: IKEv2/IPsec in the NSF

In this case, the NSF implements IPsec with IKEv2 support. The I2NSF Controller is in charge of managing and applying IPsec connection information (determining which nodes need to start an IKEv2/IPsec session, identifying the type of traffic to be protected, and deriving and delivering IKEv2 credentials, such as a pre-shared key (PSK), certificates, etc.) and applying other IKEv2 configuration parameters (e.g., cryptographic algorithms for establishing an IKEv2 SA) to the NSF necessary for the IKEv2 negotiation.¶

With these entries, the IKEv2 implementation can operate to establish the IPsec SAs. The I2NSF User establishes the IPsec requirements and information about the endpoints (through the I2NSF Consumer-Facing Interface [RFC8329]), and the I2NSF Controller translates these requirements into IKEv2, SPD, and PAD entries that will be installed into the NSF (through the I2NSF NSF-Facing Interface). With that information, the NSF can just run IKEv2 to establish the required IPsec SA (when the traffic flow needs protection). Figure 1 shows the different layers and corresponding functionality.¶

                +-------------------------------------------+
                |          IPsec Management System          | I2NSF User
                +-------------------------------------------+
                                        |
                                        |  I2NSF Consumer-Facing
                                        |  Interface
                +-------------------------------------------+
                | IKEv2 Configuration, PAD and SPD Entries  | I2NSF
                |               Distribution                | Controller
                +-------------------------------------------+
                                        |
                                        |  I2NSF NSF-Facing
                                        |  Interface
                +-------------------------------------------+
                |   IKEv2  |      IPsec(PAD, SPD)           | Network
                |-------------------------------------------| Security
                |    IPsec Data Protection and Forwarding   | Function
                +-------------------------------------------+

Figure 1: IKE Case: IKE/IPsec in the NSF

I2NSF-based IPsec flow protection services provide dynamic and flexible management of IPsec SAs in flow-based NSFs. In order to support this capability in the IKE case, a YANG data model for IKEv2, SPD, and PAD configuration data and for IKEv2 state data needs to be defined for the I2NSF NSF-Facing Interface (see Section 5).¶

### 3.2. IKE-less Case: IPsec (No IKEv2) in the NSF

In this case, the NSF does not deploy IKEv2 and, therefore, the I2NSF Controller has to perform the IKEv2 security functions and management of IPsec SAs by populating and managing the SPD and the SAD.¶

As shown in Figure 2, when an I2NSF User enforces flow-based protection policies through the Consumer-Facing Interface, the I2NSF Controller translates these requirements into SPD and SAD entries, which are installed in the NSF. PAD entries are not required, since there is no IKEv2 in the NSF.¶

             +-----------------------------------------+
             |         IPsec Management System         | I2NSF User
             +-----------------------------------------+
                                 |
                                 |  I2NSF Consumer-Facing Interface
                                 |
             +-----------------------------------------+
             |           SPD and SAD Entries           | I2NSF
             |              Distribution               | Controller
             +-----------------------------------------+
                                 |
                                 |  I2NSF NSF-Facing Interface
                                 |
             +-----------------------------------------+
             |             IPsec (SPD, SAD)            | Network
             |-----------------------------------------| Security
             |   IPsec Data Protection and Forwarding  | Function
             +-----------------------------------------+

Figure 2: IKE-less Case: IPsec (No IKEv2) in the NSF

In order to support the IKE-less case, a YANG data model for SPD and SAD configuration data and SAD state data MUST be defined for the NSF-Facing Interface (see Section 5).¶

Specifically, the IKE-less case assumes that the I2NSF Controller has to perform some security functions that IKEv2 typically does, namely (non-exhaustive list):¶

- Initialization Vector (IV) generation¶
- prevention of counter resets for the same key¶
- generation of pseudorandom cryptographic keys for the IPsec SAs¶
- generation of the IPsec SAs when required based on notifications (i.e., sadb-acquire) from the NSF¶
- rekey of the IPsec SAs based on notifications from the NSF (i.e., expire)¶
- NAT traversal discovery and management¶

Additionally to these functions, another set of tasks must be performed by the I2NSF Controller (non-exhaustive list):¶

- IPsec SA's Security Parameter Index (SPI) random generation¶
- cryptographic algorithm selection¶
- usage of extended sequence numbers¶
- establishment of proper Traffic Selectors¶

## 4. IKE Case vs. IKE-less Case

In principle, the IKE case is easier to deploy than the IKE-less case because current flow-based NSFs (either hosts or gateways) have access to IKEv2 implementations. While gateways typically deploy an IKEv2/IPsec implementation, hosts can easily install it. As a downside, the NSF needs more resources to use IKEv2, such as memory for the IKEv2 implementation and computation, since each IPsec Security Association rekeying MAY involve a Diffie-Hellman (DH) exchange.¶

Alternatively, the IKE-less case benefits the deployment in resource-constrained NSFs. Moreover, IKEv2 does not need to be performed in gateway-to-gateway and host-to-host scenarios under the same I2NSF Controller (see Appendix D.1). On the contrary, the complexity of creating and managing IPsec SAs is shifted to the I2NSF Controller since IKEv2 is not in the NSF. As a consequence, this may result in a more complex implementation in the controller side in comparison with the IKE case. For example, the I2NSF Controller has to deal with the latency existing in the path between the I2NSF Controller and the NSF (in order to solve tasks, such as rekey) or creation and installation of new IPsec SAs. However, this is not specific to this contribution but a general aspect in any SDN-based network. In summary, this complexity may create some scalability and performance issues when the number of NSFs is high.¶

Nevertheless, literature around SDN-based network management using a centralized controller (like the I2NSF Controller) is aware of scalability and performance issues, and solutions have been already provided and discussed (e.g., hierarchical controllers, having multiple replicated controllers, dedicated high-speed management networks, etc.). In the context of I2NSF-based IPsec management, one way to reduce the latency and alleviate some performance issues can be to install the IPsec policies and IPsec SAs at the same time (proactive mode, as described in Appendix D.1) instead of waiting for notifications (e.g., a sadb-acquire notification received from an NSF requiring a new IPsec SA) to proceed with the IPsec SA installation (reactive mode). Another way to reduce the overhead and the potential scalability and performance issues in the I2NSF Controller is to apply the IKE case described in this document since the IPsec SAs are managed between NSFs without the involvement of the I2NSF Controller at all, except by the initial configuration (i.e., IKEv2, PAD, and SPD entries) provided by the I2NSF Controller. Other solutions, such as Controller-IKE [IPSECME-CONTROLLER-IKE], have proposed that NSFs provide their DH public keys to the I2NSF Controller so that the I2NSF Controller distributes all public keys to all peers. All peers can calculate a unique pairwise secret for each other peer, and there is no inter-NSF messages. A rekey mechanism is further described in [IPSECME-CONTROLLER-IKE].¶

In terms of security, the IKE case provides better security properties than the IKE-less case, as discussed in Section 7. The main reason is that the NSFs generate the session keys and not the I2NSF Controller.¶

### 4.1. Rekeying Process

Performing a rekey for IPsec SAs is an important operation during the IPsec SAs management. With the YANG data models defined in this document the I2NSF Controller can configure parameters of the rekey process (IKE case) or conduct the rekey process (IKE-less case). Indeed, depending on the case, the rekey process is different.¶

For the IKE case, the rekeying process is carried out by IKEv2, following the information defined in the SPD and SAD (i.e., based on the IPsec SA lifetime established by the I2NSF Controller using the YANG data model defined in this document). Therefore, IPsec connections will live unless something different is required by the I2NSF User or the I2NSF Controller detects something wrong.¶

For the IKE-less case, the I2NSF Controller MUST take care of the rekeying process. When the IPsec SA is going to expire (e.g., IPsec SA soft lifetime), it MUST create a new IPsec SA and it MAY remove the old one (e.g., when the lifetime of the old IPsec SA has not been defined). This rekeying process starts when the I2NSF Controller receives a sadb-expire notification or, on the I2NSF Controller's initiative, based on lifetime state data obtained from the NSF. How the I2NSF Controller implements an algorithm for the rekey process is out of the scope of this document. Nevertheless, an example of how this rekey could be performed is described in Appendix D.2.¶

### 4.2. NSF State Loss

If one of the NSF restarts, it will lose the IPsec state (affected NSF). By default, the I2NSF Controller can assume that all the state has been lost and, therefore, it will have to send IKEv2, SPD, and PAD information to the NSF in the IKE case and SPD and SAD information in the IKE-less case.¶

In both cases, the I2NSF Controller is aware of the affected NSF (e.g., the NETCONF/TCP connection is broken with the affected NSF, the I2NSF Controller is receiving a sadb-bad-spi notification from a particular NSF, etc.). Moreover, the I2NSF Controller keeps a list of NSFs that have IPsec SAs with the affected NSF. Therefore, it knows the affected IPsec SAs.¶

In the IKE case, the I2NSF Controller may need to configure the affected NSF with the new IKEv2, SPD, and PAD information. Alternatively, IKEv2 configuration MAY be made permanent between NSF reboots without compromising security by means of the startup configuration datastore in the NSF. This way, each time an NSF reboots, it will use that configuration for each rebooting. It would imply avoiding contact with the I2NSF Controller. Finally, the I2NSF Controller may also need to send new parameters (e.g., a new fresh PSK for authentication) to the NSFs that had IKEv2 SAs and IPsec SAs with the affected NSF.¶

In the IKE-less case, the I2NSF Controller SHOULD delete the old IPsec SAs in the non-failed nodes established with the affected NSF. Once the affected node restarts, the I2NSF Controller MUST take the necessary actions to reestablish IPsec-protected communication between the failed node and those others having IPsec SAs with the affected NSF. How the I2NSF Controller implements an algorithm for managing a potential NSF state loss is out of the scope of this document. Nevertheless, an example of how this could be performed is described in Appendix D.3.¶

### 4.3. NAT Traversal

In the IKE case, IKEv2 already provides a mechanism to detect whether some of the peers or both are located behind a NAT. In this case, UDP or TCP encapsulation for Encapsulating Security Payload (ESP) packets [RFC3948] [RFC8229] is required. Note that IPsec transport mode MUST NOT be used in this specification when NAT is required.¶

In the IKE-less case, the NSF does not have the assistance of the IKEv2 implementation to detect if it is located behind a NAT. If the NSF does not have any other mechanism to detect this situation, the I2NSF Controller SHOULD implement a mechanism to detect that case. The SDN paradigm generally assumes the I2NSF Controller has a view of the network under its control. This view is built either by requesting information from the NSFs under its control or information pushed from the NSFs to the I2NSF Controller. Based on this information, the I2NSF Controller MAY guess if there is a NAT configured between two hosts and apply the required policies to both NSFs besides activating the usage of UDP or TCP encapsulation of ESP packets [RFC3948] [RFC8229]. The interface for discovering if the NSF is behind a NAT is out of scope of this document.¶

If the I2NSF Controller does not have any mechanism to know whether a host is behind a NAT or not, then the IKE case MUST be used and not the IKE-less case.¶

### 4.4. NSF Registration and Discovery

NSF registration refers to the process of providing the I2NSF Controller information about a valid NSF, such as certificate, IP address, etc. This information is incorporated in a list of NSFs under its control.¶

The assumption in this document is that, for both cases, before an NSF can operate in this system, it MUST be registered in the I2NSF Controller. In this way, when the NSF starts and establishes a connection to the I2NSF Controller, it knows that the NSF is valid for joining the system.¶

Either during this registration process or when the NSF connects with the I2NSF Controller, the I2NSF Controller MUST discover certain capabilities of this NSF, such as what are the cryptographic suites supported, the authentication method, the support of the IKE case and/or the IKE-less case, etc.¶

The registration and discovery processes are out of the scope of this document.¶

## 5. YANG Configuration Data Models

In order to support the IKE and IKE-less cases, models are provided for the different parameters and values that must be configured to manage IPsec SAs. Specifically, the IKE case requires modeling IKEv2 configuration parameters, SPD and PAD, while the IKE-less case requires configuration YANG data models for the SPD and SAD. Three modules have been defined: ietf-i2nsf-ikec (Section 5.1, common to both cases), ietf-i2nsf-ike (Section 5.2, IKE case), and ietf-i2nsf-ikeless (Section 5.3, IKE-less case). Since the module ietf-i2nsf-ikec has only typedef and groupings common to the other modules, a simplified view of the ietf-i2nsf-ike and ietf-i2nsf-ikeless modules is shown.¶

### 5.1. The 'ietf-i2nsf-ikec' Module

#### 5.1.1. Data Model Overview

The module ietf-i2nsf-ikec only has definitions of data types (typedef) and groupings that are common to the other modules.¶

#### 5.1.2. YANG Module

This module has normative references to [RFC3947], [RFC4301], [RFC4303], [RFC8174], [RFC8221], [RFC3948], [RFC8229], [RFC6991], [IANA-Protocols-Number], [IKEv2-Parameters], [IKEv2-Transform-Type-1], and [IKEv2-Transform-Type-3].¶

    <CODE BEGINS> file "ietf-i2nsf-ikec@2021-07-14.yang"

    module ietf-i2nsf-ikec {
      yang-version 1.1;
      namespace "urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikec";
      prefix nsfikec;

      import ietf-inet-types {
        prefix inet;
        reference
          "RFC 6991: Common YANG Data Types.";
      }

      organization
        "IETF I2NSF Working Group";
      contact
        "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/>
         WG List: <mailto:i2nsf@ietf.org>

         Author: Rafael Marin-Lopez
                   <mailto:rafa@um.es>

         Author: Gabriel Lopez-Millan
                   <mailto:gabilm@um.es>

         Author: Fernando Pereniguez-Garcia
                   <mailto:fernando.pereniguez@cud.upct.es>
        ";
      description
        "Common data model for the IKE and IKE-less cases
         defined by the SDN-based IPsec flow protection service.

         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) 2021 IETF Trust and the persons
         identified as authors of the code.  All rights reserved.

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

         This version of this YANG module is part of RFC 9061; see
         the RFC itself for full legal notices.";

      revision 2021-07-14 {
        description
          "Initial version.";
        reference
          "RFC 9061: A YANG Data Model for IPsec Flow Protection
                     Based on Software-Defined Networking (SDN).";
      }

      typedef encr-alg-t {
        type uint16;
        description
          "The encryption algorithm is specified with a 16-bit
           number extracted from the IANA registry.  The acceptable
           values MUST follow the requirement levels for
           encryption algorithms for ESP and IKEv2.";
        reference
          "IANA: Internet Key Exchange Version 2 (IKEv2) Parameters,
                 IKEv2 Transform Attribute Types, Transform Type 1 -
                 Encryption Algorithm Transform IDs
           RFC 8221: Cryptographic Algorithm Implementation
                     Requirements and Usage Guidance for Encapsulating
                     Security Payload (ESP) and Authentication Header
                     (AH)
           RFC 8247: Algorithm Implementation Requirements and Usage
                     Guidance for the Internet Key Exchange Protocol
                     Version 2 (IKEv2).";
      }

      typedef intr-alg-t {
        type uint16;
        description
          "The integrity algorithm is specified with a 16-bit
           number extracted from the IANA registry.
           The acceptable values MUST follow the requirement
           levels for integrity algorithms for ESP and IKEv2.";
        reference
          "IANA: Internet Key Exchange Version 2 (IKEv2) Parameters,
                 IKEv2 Transform Attribute Types, Transform Type 3 -
                 Integrity Algorithm Transform IDs
           RFC 8221: Cryptographic Algorithm Implementation
                     Requirements and Usage Guidance for Encapsulating
                     Security Payload (ESP) and Authentication Header
                     (AH)
           RFC 8247: Algorithm Implementation Requirements and Usage
                     Guidance for the Internet Key Exchange Protocol
                     Version 2 (IKEv2).";
      }

      typedef ipsec-mode {
        type enumeration {
          enum transport {
            description
              "IPsec transport mode.  No Network Address
               Translation (NAT) support.";
          }
          enum tunnel {
            description
              "IPsec tunnel mode.";
          }
        }
        description
          "Type definition of IPsec mode: transport or
           tunnel.";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 3.2.";
      }

      typedef esp-encap {
        type enumeration {
          enum espintcp {
            description
              "ESP in TCP encapsulation.";
            reference
              "RFC 8229: TCP Encapsulation of IKE and
                         IPsec Packets.";
          }
          enum espinudp {
            description
              "ESP in UDP encapsulation.";
            reference
              "RFC 3948: UDP Encapsulation of IPsec ESP
                         Packets.";
          }
          enum none {
            description
              "No ESP encapsulation.";
          }
        }
        description
          "Types of ESP encapsulation when Network Address
           Translation (NAT) may be present between two NSFs.";
        reference
          "RFC 8229: TCP Encapsulation of IKE and IPsec Packets
           RFC 3948: UDP Encapsulation of IPsec ESP Packets.";
      }

      typedef ipsec-protocol-params {
        type enumeration {
          enum esp {
            description
              "IPsec ESP protocol.";
          }
        }
        description
          "Only the Encapsulation Security Protocol (ESP) is
           supported, but it could be extended in the future.";
        reference
          "RFC 4303: IP Encapsulating Security Payload (ESP).";
      }

      typedef lifetime-action {
        type enumeration {
          enum terminate-clear {
            description
              "Terminates the IPsec SA and allows the
               packets through.";
          }
          enum terminate-hold {
            description
              "Terminates the IPsec SA and drops the
               packets.";
          }
          enum replace {
            description
              "Replaces the IPsec SA with a new one:
               rekey.";
          }
        }
        description
          "When the lifetime of an IPsec SA expires, an action
           needs to be performed for the IPsec SA that
           reached the lifetime.  There are three possible
           options: terminate-clear, terminate-hold, and
           replace.";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.5.";
      }

      typedef ipsec-traffic-direction {
        type enumeration {
          enum inbound {
            description
              "Inbound traffic.";
          }
          enum outbound {
            description
              "Outbound traffic.";
          }
        }
        description
          "IPsec traffic direction is defined in
           two directions: inbound and outbound.
           From an NSF perspective, inbound and
           outbound are defined as mentioned
           in Section 3.1 in RFC 4301.";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 3.1.";
      }

      typedef ipsec-spd-action {
        type enumeration {
          enum protect {
            description
              "PROTECT the traffic with IPsec.";
          }
          enum bypass {
            description
              "BYPASS the traffic.  The packet is forwarded
               without IPsec protection.";
          }
          enum discard {
            description
              "DISCARD the traffic.  The IP packet is
               discarded.";
          }
        }
        description
          "The action when traffic matches an IPsec security
           policy.  According to RFC 4301, there are three
           possible values: BYPASS, PROTECT, and DISCARD.";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.4.1.";
      }

      typedef ipsec-inner-protocol {
        type union {
          type uint8;
          type enumeration {
            enum any {
              value 256;
              description
                "Any IP protocol number value.";
            }
          }
        }
        default "any";
        description
          "IPsec protection can be applied to specific IP
           traffic and Layer 4 traffic (TCP, UDP, SCTP, etc.)
           or ANY protocol in the IP packet payload.
           The IP protocol number is specified with a uint8
           or ANY defining an enumerate with value 256 to
           indicate the protocol number.  Note that in case
           of IPv6, the protocol in the IP packet payload
           is indicated in the Next Header field of the IPv6
           packet.";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.4.1.1
           IANA: Protocol Numbers.";
      }

      grouping encap {
        description
          "This group of nodes allows defining of the type of
           encapsulation in case NAT traversal is
           required and includes port information.";
        leaf espencap {
          type esp-encap;
          default "none";
          description
            "ESP in TCP, ESP in UDP, or ESP in TLS.";
        }
        leaf sport {
          type inet:port-number;
          default "4500";
          description
            "Encapsulation source port.";
        }
        leaf dport {
          type inet:port-number;
          default "4500";
          description
            "Encapsulation destination port.";
        }
        leaf-list oaddr {
          type inet:ip-address;
          description
            "If required, this is the original address that
             was used before NAT was applied over the packet.";
        }
        reference
          "RFC 3947: Negotiation of NAT-Traversal in the IKE
           RFC 8229: TCP Encapsulation of IKE and IPsec Packets.";
      }

      grouping lifetime {
        description
          "Different lifetime values limited to an IPsec SA.";
        leaf time {
          type uint32;
          units "seconds";
          default "0";
          description
            "Time in seconds since the IPsec SA was added.
             For example, if this value is 180 seconds, it
             means the IPsec SA expires in 180 seconds since
             it was added.  The value 0 implies infinite.";
        }
        leaf bytes {
          type uint64;
          default "0";
          description
            "If the IPsec SA processes the number of bytes
             expressed in this leaf, the IPsec SA expires and
             SHOULD be rekeyed.  The value 0 implies
             infinite.";
        }
        leaf packets {
          type uint32;
          default "0";
          description
            "If the IPsec SA processes the number of packets
             expressed in this leaf, the IPsec SA expires and
             SHOULD be rekeyed.  The value 0 implies
             infinite.";
        }
        leaf idle {
          type uint32;
          units "seconds";
          default "0";
          description
            "When an NSF stores an IPsec SA, it
             consumes system resources.  For an idle IPsec SA, this
             is a waste of resources.  If the IPsec SA is idle
             during this number of seconds, the IPsec SA
             SHOULD be removed.  The value 0 implies
             infinite.";
        }
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.4.2.1.";
      }

      grouping port-range {
        description
          "This grouping defines a port range, such as that
           expressed in RFC 4301, for example, 1500 (Start
           Port Number)-1600 (End Port Number).
           A port range is used in the Traffic Selector.";
        leaf start {
          type inet:port-number;
          description
            "Start port number.";
        }
        leaf end {
          type inet:port-number;
          must '. >= ../start' {
            error-message
              "The end port number MUST be equal or greater
               than the start port number.";
          }
          description
            "End port number.  To express a single port, set
             the same value as start and end.";
        }
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.4.1.2.";
      }

      grouping tunnel-grouping {
        description
          "The parameters required to define the IP tunnel
           endpoints when IPsec SA requires tunnel mode.  The
           tunnel is defined by two endpoints: the local IP
           address and the remote IP address.";
        leaf local {
          type inet:ip-address;
          mandatory true;
          description
            "Local IP address' tunnel endpoint.";
        }
        leaf remote {
          type inet:ip-address;
          mandatory true;
          description
            "Remote IP address' tunnel endpoint.";
        }
        leaf df-bit {
          type enumeration {
            enum clear {
              description
                "Disable the Don't Fragment (DF) bit
                 in the outer header.  This is the
                 default value.";
            }
            enum set {
              description
                "Enable the DF bit in the outer header.";
            }
            enum copy {
              description
                "Copy the DF bit to the outer header.";
            }
          }
          default "clear";
          description
            "Allow configuring the DF bit when encapsulating
             tunnel mode IPsec traffic.  RFC 4301 describes
             three options to handle the DF bit during
             tunnel encapsulation: clear, set, and copy from
             the inner IP header.  This MUST be ignored or
             has no meaning when the local/remote
             IP addresses are IPv6 addresses.";
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 8.1.";
        }
        leaf bypass-dscp {
          type boolean;
          default "true";
          description
            "If true, to copy the Differentiated Services Code
             Point (DSCP) value from inner header to outer header.
             If false, to map DSCP values
             from an inner header to values in an outer header
             following ../dscp-mapping.";
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.1.2.";
        }
        list dscp-mapping {
          must '../bypass-dscp = "false"';
          key "id";
          ordered-by user;
          leaf id {
            type uint8;
            description
              "The index of list with the
               different mappings.";
          }
          leaf inner-dscp {
            type inet:dscp;
            description
              "The DSCP value of the inner IP packet.  If this
               leaf is not defined, it means ANY inner DSCP value.";
          }
          leaf outer-dscp {
            type inet:dscp;
            default "0";
            description
              "The DSCP value of the outer IP packet.";
          }
          description
            "A list that represents an array with the mapping from the
             inner DSCP value to outer DSCP value when bypass-dscp is
             false.  To express a default mapping in the list where any
             other inner dscp value is not matching a node in the list,
             a new node has to be included at the end of the list where
             the leaf inner-dscp is not defined (ANY) and the leaf
             outer-dscp includes the value of the mapping.  If there is
             no value set in the leaf outer-dscp, the default value for
             this leaf is 0.";
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.1.2 and Appendix C.";
        }
      }

      grouping selector-grouping {
        description
          "This grouping contains the definition of a Traffic
           Selector, which is used in the IPsec policies and
           IPsec SAs.";
        leaf local-prefix {
          type inet:ip-prefix;
          mandatory true;
          description
            "Local IP address prefix.";
        }
        leaf remote-prefix {
          type inet:ip-prefix;
          mandatory true;
          description
            "Remote IP address prefix.";
        }
        leaf inner-protocol {
          type ipsec-inner-protocol;
          default "any";
          description
            "Inner protocol that is going to be
             protected with IPsec.";
        }
        list local-ports {
          key "start end";
          uses port-range;
          description
            "List of local ports. When the inner
             protocol is ICMP, this 16-bit value
             represents code and type.
             If this list is not defined,
             it is assumed that start and
             end are 0 by default (any port).";
        }
        list remote-ports {
          key "start end";
          uses port-range;
          description
            "List of remote ports. When the upper layer
             protocol is ICMP, this 16-bit value represents
             code and type.  If this list is not defined,
             it is assumed that start and end are 0 by
             default (any port).";
        }
        reference
          "RFC 4301: Security Architecture for the Internet Protocol,
                     Section 4.4.1.2.";
      }

      grouping ipsec-policy-grouping {
        description
          "Holds configuration information for an IPsec SPD
           entry.";
        leaf anti-replay-window-size {
          type uint32;
          default "64";
          description
            "To set the anti-replay window size.
             The default value is set
             to 64, following the recommendation in RFC 4303.";
          reference
            "RFC 4303: IP Encapsulating Security Payload (ESP),
                       Section 3.4.3.";
        }
        container traffic-selector {
          description
            "Packets are selected for
             processing actions based on Traffic Selector
             values, which refer to IP and inner protocol
             header information.";
          uses selector-grouping;
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.4.1.";
        }
        container processing-info {
          description
            "SPD processing.  If the required processing
             action is protect, it contains the required
             information to process the packet.";
          leaf action {
            type ipsec-spd-action;
            default "discard";
            description
              "If bypass or discard, container
               ipsec-sa-cfg is empty.";
          }
          container ipsec-sa-cfg {
            when "../action = 'protect'";
            description
              "IPsec SA configuration included in the SPD
               entry.";
            leaf pfp-flag {
              type boolean;
              default "false";
              description
                "Each selector has a Populate From
                 Packet (PFP) flag.  If asserted for a
                 given selector X, the flag indicates
                 that the IPsec SA to be created should
                 take its value (local IP address,
                 remote IP address, Next Layer
                 Protocol, etc.) for X from the value
                 in the packet.  Otherwise, the IPsec SA
                 should take its value(s) for X from
                 the value(s) in the SPD entry.";
            }
            leaf ext-seq-num {
              type boolean;
              default "false";
              description
                "True if this IPsec SA is using extended
                 sequence numbers.  If true, the 64-bit
                 extended sequence number counter is used;
                 if false, the normal 32-bit sequence
                 number counter is used.";
            }
            leaf seq-overflow {
              type boolean;
              default "false";
              description
                "The flag indicating whether
                 overflow of the sequence number
                 counter should prevent transmission
                 of additional packets on the IPsec
                 SA (false) and, therefore, needs to
                 be rekeyed or whether rollover is
                 permitted (true).  If Authenticated
                 Encryption with Associated Data
                 (AEAD) is used (leaf
                 esp-algorithms/encryption/algorithm-type),
                 this flag MUST be false.  Setting this
                 flag to true is strongly discouraged.";
            }
            leaf stateful-frag-check {
              type boolean;
              default "false";
              description
                "Indicates whether (true) or not (false)
                 stateful fragment checking applies to
                 the IPsec SA to be created.";
            }
            leaf mode {
              type ipsec-mode;
              default "transport";
              description
                "IPsec SA has to be processed in
                 transport or tunnel mode.";
            }
            leaf protocol-parameters {
              type ipsec-protocol-params;
              default "esp";
              description
                "Security protocol of the IPsec SA.
                 Only ESP is supported, but it could be
                 extended in the future.";
            }
            container esp-algorithms {
              when "../protocol-parameters = 'esp'";
              description
                "Configuration of Encapsulating
                 Security Payload (ESP) parameters and
                 algorithms.";
              leaf-list integrity {
                type intr-alg-t;
                default "0";
                ordered-by user;
                description
                  "Configuration of ESP authentication
                   based on the specified integrity
                   algorithm.  With AEAD encryption
                   algorithms, the integrity node is
                   not used.";
                reference
                  "RFC 4303: IP Encapsulating Security Payload (ESP),
                             Section 3.2.";
              }
              list encryption {
                key "id";
                ordered-by user;
                leaf id {
                  type uint16;
                  description
                    "An identifier that unequivocally identifies each
                     entry of the list, i.e., an encryption algorithm
                     and its key length (if required).";
                }
                leaf algorithm-type {
                  type encr-alg-t;
                  default "20";
                  description
                    "Default value 20 (ENCR_AES_GCM_16).";
                }
                leaf key-length {
                  type uint16;
                  default "128";
                  description
                    "By default, key length is 128
                     bits.";
                }
                description
                  "Encryption or AEAD algorithm for the
                   IPsec SAs.  This list is ordered
                   following from the higher priority to
                   lower priority.  First node of the
                   list will be the algorithm with
                   higher priority.  In case the list
                   is empty, then no encryption algorithm
                   is applied (NULL).";
                reference
                  "RFC 4303: IP Encapsulating Security Payload (ESP),
                             Section 3.2.";
              }
              leaf tfc-pad {
                type boolean;
                default "false";
                description
                  "If Traffic Flow Confidentiality
                   (TFC) padding for ESP encryption
                   can be used (true) or not (false).";
                reference
                  "RFC 4303: IP Encapsulating Security Payload (ESP),
                             Section 2.7.";
              }
              reference
                "RFC 4303: IP Encapsulating Security Payload (ESP).";
            }
            container tunnel {
              when "../mode = 'tunnel'";
              uses tunnel-grouping;
              description
                "IPsec tunnel endpoints definition.";
            }
          }
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.1.2.";
        }
      }
    }

    <CODE ENDS>

¶

### 5.2. The 'ietf-i2nsf-ike' Module

In this section, the YANG module for the IKE case is described.¶

#### 5.2.1. Data Model Overview

The model related to IKEv2 has been extracted from reading the IKEv2 standard in [RFC7296] and observing some open source implementations, such as strongSwan [strongswan] or Libreswan [libreswan].¶

The definition of the PAD model has been extracted from the specification in Section 4.4.3 of [RFC4301]. (Note that many implementations integrate PAD configuration as part of the IKEv2 configuration.)¶

The definition of the SPD model has been mainly extracted from the specification in Section 4.4.1 and Appendix D of [RFC4301].¶

The YANG data model for the IKE case is defined by the module "ietf-i2nsf-ike". Its structure is depicted in the following diagram, using the notation syntax for YANG tree diagrams [RFC8340].¶

    module: ietf-i2nsf-ike
      +--rw ipsec-ike
        +--rw pad
        |  +--rw pad-entry* [name]
        |     +--rw name                           string
        |     +--rw (identity)
        |     |  +--:(ipv4-address)
        |     |  |  +--rw ipv4-address?            inet:ipv4-address
        |     |  +--:(ipv6-address)
        |     |  |  +--rw ipv6-address?            inet:ipv6-address
        |     |  +--:(fqdn-string)
        |     |  |  +--rw fqdn-string?             inet:domain-name
        |     |  +--:(rfc822-address-string)
        |     |  |  +--rw rfc822-address-string?   string
        |     |  +--:(dnx509)
        |     |  |  +--rw dnx509?                  binary
        |     |  +--:(gnx509)
        |     |  |  +--rw gnx509?                  binary
        |     |  +--:(id-key)
        |     |  |  +--rw id-key?                  binary
        |     |  +--:(id-null)
        |     |     +--rw id-null?                 empty
        |     +--rw auth-protocol?                 auth-protocol-type
        |     +--rw peer-authentication
        |        +--rw auth-method?         auth-method-type
        |        +--rw eap-method
        |        |  +--rw eap-type    uint64
        |        +--rw pre-shared
        |        |  +--rw secret?   yang:hex-string
        |        +--rw digital-signature
        |           +--rw ds-algorithm?           uint8
        |           +--rw (public-key)?
        |           |  +--:(raw-public-key)
        |           |  |  +--rw raw-public-key?   binary
        |           |  +--:(cert-data)
        |           |     +--rw cert-data?        binary
        |           +--rw private-key?            binary
        |           +--rw ca-data*                binary
        |           +--rw crl-data?               binary
        |           +--rw crl-uri?                inet:uri
        |           +--rw oscp-uri?               inet:uri
        +--rw conn-entry* [name]
        |  +--rw name                             string
        |  +--rw autostartup?                     autostartup-type
        |  +--rw initial-contact?                 boolean
        |  +--rw version?                         auth-protocol-type
        |  +--rw fragmentation
        |  |  +--rw enabled?   boolean
        |  |  +--rw mtu?      uint16
        |  +--rw ike-sa-lifetime-soft
        |  |  +--rw rekey-time?    uint32
        |  |  +--rw reauth-time?   uint32
        |  +--rw ike-sa-lifetime-hard
        |  |  +--rw over-time?   uint32
        |  +--rw ike-sa-intr-alg*  nsfikec:intr-alg-t
        |  +--rw ike-sa-encr-alg* [id]
        |  |  +--rw id                uint16
        |  |  +--rw algorithm-type?   nsfikec:encr-alg-t
        |  |  +--rw key-length?       uint16
        |  +--rw dh-group?                            fs-group
        |  +--rw half-open-ike-sa-timer?              uint32
        |  +--rw half-open-ike-sa-cookie-threshold?   uint32
        |  +--rw local
        |  |  +--rw local-pad-entry-name    string
        |  +--rw remote
        |  |  +--rw remote-pad-entry-name    string
        |  +--rw encapsulation-type
        |  |  +--rw espencap?   esp-encap
        |  |  +--rw sport?      inet:port-number
        |  |  +--rw dport?      inet:port-number
        |  |  +--rw oaddr*      inet:ip-address
        |  +--rw spd
        |  |  +--rw spd-entry* [name]
        |  |    +--rw name                   string
        |  |    +--rw ipsec-policy-config
        |  |      +--rw anti-replay-window-size?   uint32
        |  |      +--rw traffic-selector
        |  |      |  +--rw local-prefix      inet:ip-prefix
        |  |      |  +--rw remote-prefix     inet:ip-prefix
        |  |      |  +--rw inner-protocol?   ipsec-inner-protocol
        |  |      |  +--rw local-ports* [start end]
        |  |      |  |  +--rw start    inet:port-number
        |  |      |  |  +--rw end      inet:port-number
        |  |      |  +--rw remote-ports* [start end]
        |  |      |     +--rw start    inet:port-number
        |  |      |     +--rw end      inet:port-number
        |  |      +--rw processing-info
        |  |        +--rw action?         ipsec-spd-action
        |  |        +--rw ipsec-sa-cfg
        |  |         +--rw pfp-flag?              boolean
        |  |         +--rw ext-seq-num?           boolean
        |  |         +--rw seq-overflow?          boolean
        |  |         +--rw stateful-frag-check?   boolean
        |  |         +--rw mode?                  ipsec-mode
        |  |         +--rw protocol-parameters? ipsec-protocol-params
        |  |              +--rw esp-algorithms
        |  |              |  +--rw integrity*    intr-alg-t
        |  |              |  +--rw encryption* [id]
        |  |              |  |  +--rw id                uint16
        |  |              |  |  +--rw algorithm-type?   encr-alg-t
        |  |              |  |  +--rw key-length?       uint16
        |  |              |  +--rw tfc-pad?      boolean
        |  |              +--rw tunnel
        |  |                 +--rw local           inet:ip-address
        |  |                 +--rw remote          inet:ip-address
        |  |                 +--rw df-bit?         enumeration
        |  |                 +--rw bypass-dscp?    boolean
        |  |                 +--rw dscp-mapping* [id]
        |  |                    +--rw id            uint8
        |  |                    +--rw inner-dscp?   inet:dscp
        |  |                    +--rw outer-dscp?   inet:dscp
        |  +--rw child-sa-info
        |  |  +--rw fs-groups*                fs-group
        |  |  +--rw child-sa-lifetime-soft
        |  |  |  +--rw time?      uint32
        |  |  |  +--rw bytes?     yang:counter64
        |  |  |  +--rw packets?   uint32
        |  |  |  +--rw idle?      uint32
        |  |  |  +--rw action?    nsfikec:lifetime-action
        |  |  +--rw child-sa-lifetime-hard
        |  |     +--rw time?      uint32
        |  |     +--rw bytes?     yang:counter64
        |  |     +--rw packets?   uint32
        |  |     +--rw idle?      uint32
        |  +--ro state
        |     +--ro initiator?             boolean
        |     +--ro initiator-ikesa-spi?   ike-spi
        |     +--ro responder-ikesa-spi?   ike-spi
        |     +--ro nat-local?             boolean
        |     +--ro nat-remote?            boolean
        |     +--ro encapsulation-type
        |     |  +--ro espencap?   esp-encap
        |     |  +--ro sport?      inet:port-number
        |     |  +--ro dport?      inet:port-number
        |     |  +--ro oaddr*      inet:ip-address
        |     +--ro established?           uint64
        |     +--ro current-rekey-time?    uint64
        |     +--ro current-reauth-time?   uint64
        +--ro number-ike-sas
            +--ro total?               yang:gauge64
            +--ro half-open?           yang:gauge64
            +--ro half-open-cookies?   yang:gauge64

¶

The YANG data model consists of a unique "ipsec-ike" container defined as follows. Firstly, it contains a "pad" container that serves to configure the Peer Authentication Database with authentication information about local and remote peers (NSFs). More precisely, it consists of a list of entries, each one indicating the identity, authentication method, and credentials that a particular peer (local or remote) will use. Therefore, each entry contains identity, authentication information, and credentials of either the local NSF or the remote NSF. As a consequence, the I2NF Controller can store identity, authentication information, and credentials for the local NSF and the remote NSF.¶

Next, a list "conn-entry" is defined with information about the different IKE connections a peer can maintain with others. Each connection entry is composed of a wide number of parameters to configure different aspects of a particular IKE connection between two peers: local and remote peer authentication information, IKE SA configuration (soft and hard lifetimes, cryptographic algorithms, etc.), a list of IPsec policies describing the type of network traffic to be secured (local/remote subnet and ports, etc.) and how it must be protected (ESP, tunnel/transport, cryptographic algorithms, etc.), Child SA configuration (soft and hard lifetimes), and state information of the IKE connection (SPIs, usage of NAT, current expiration times, etc.).¶

Lastly, the "ipsec-ike" container declares a "number-ike-sas" container to specify state information reported by the IKE software related to the amount of IKE connections established.¶

#### 5.2.2. Example Usage

Appendix A shows an example of IKE case configuration for an NSF, in tunnel mode (gateway-to-gateway), with NSF authentication based on X.509 certificates.¶

#### 5.2.3. YANG Module

This YANG module has normative references to [RFC5280], [RFC4301], [RFC5915], [RFC6991], [RFC7296], [RFC7383], [RFC7427], [RFC7619], [RFC8017], [ITU-T.X.690], [RFC5322], [RFC8229], [RFC8174], [RFC6960], [IKEv2-Auth-Method], [IKEv2-Transform-Type-4], [IKEv2-Parameters], and [IANA-Method-Type].¶

    <CODE BEGINS> file "ietf-i2nsf-ike@2021-07-14.yang"

    module ietf-i2nsf-ike {
      yang-version 1.1;
      namespace "urn:ietf:params:xml:ns:yang:ietf-i2nsf-ike";
      prefix nsfike;

      import ietf-inet-types {
        prefix inet;
        reference
          "RFC 6991: Common YANG Data Types.";
      }
      import ietf-yang-types {
        prefix yang;
        reference
          "RFC 6991: Common YANG Data Types.";
      }
      import ietf-i2nsf-ikec {
        prefix nsfikec;
        reference
          "RFC 9061: A YANG Data Model for IPsec Flow Protection
                     Based on Software-Defined Networking (SDN).";
      }
      import ietf-netconf-acm {
        prefix nacm;
        reference
          "RFC 8341: Network Configuration Access Control
                     Model.";
      }

      organization
        "IETF I2NSF Working Group";
      contact
        "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/>
         WG List: <mailto:i2nsf@ietf.org>

         Author: Rafael Marin-Lopez
                   <mailto:rafa@um.es>

         Author: Gabriel Lopez-Millan
                   <mailto:gabilm@um.es>

         Author: Fernando Pereniguez-Garcia
                   <mailto:fernando.pereniguez@cud.upct.es>
        ";
      description
        "This module contains the IPsec IKE case model for the SDN-based
         IPsec flow protection service.

         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) 2021 IETF Trust and the persons identified as
         authors of the code.  All rights reserved.

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

         This version of this YANG module is part of RFC 9061; see
         the RFC itself for full legal notices.";

      revision 2021-07-14 {
        description
          "Initial version.";
        reference
          "RFC 9061: A YANG Data Model for IPsec Flow Protection
                     Based on Software-Defined Networking (SDN).";
      }

      typedef ike-spi {
        type uint64 {
          range "0..max";
        }
        description
          "Security Parameter Index (SPI)'s IKE SA.";
        reference
          "RFC 7296: Internet Key Exchange Protocol Version 2
                     (IKEv2), Section 2.6.";
      }

      typedef autostartup-type {
        type enumeration {
          enum add {
            description
              "IKE/IPsec configuration is only loaded into
               IKE implementation, but IKE/IPsec SA is not
               started.";
          }
          enum on-demand {
            description
              "IKE/IPsec configuration is loaded
               into IKE implementation.  The IPsec policies
               are transferred to the NSF, but the
               IPsec SAs are not established immediately.
               The IKE implementation will negotiate the
               IPsec SAs when they are required
               (i.e., through an ACQUIRE notification).";
          }
          enum start {
            description
              "IKE/IPsec configuration is loaded
               and transferred to the NSF's kernel, and the
               IKEv2-based IPsec SAs are established
               immediately without waiting for any packet.";
          }
        }
        description
          "Different policies to set IPsec SA configuration
           into NSF's kernel when IKEv2 implementation has
           started.";
      }

      typedef fs-group {
        type uint16;
        description
          "DH groups for IKE and IPsec SA rekey.";
        reference
          "IANA: Internet Key Exchange Version 2 (IKEv2) Parameters,
                 IKEv2 Transform Attribute Types, Transform Type 4 -
                 Diffie-Hellman Group Transform IDs
           RFC 7296: Internet Key Exchange Protocol Version 2
                     (IKEv2), Section 3.3.2.";
      }

      typedef auth-protocol-type {
        type enumeration {
          enum ikev2 {
            value 2;
            description
              "IKEv2 authentication protocol.  It is the
               only one defined right now.  An enum is
               used for further extensibility.";
          }
        }
        description
          "IKE authentication protocol version specified in the
           Peer Authorization Database (PAD).  It is defined as
           enumerated to allow new IKE versions in the
           future.";
        reference
          "RFC 7296: Internet Key Exchange Protocol Version 2
                     (IKEv2).";
      }

      typedef auth-method-type {
        type enumeration {
          enum pre-shared {
            description
              "Select pre-shared key as the
               authentication method.";
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2).";
          }
          enum eap {
            description
              "Select the Extensible Authentication Protocol (EAP) as
               the authentication method.";
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2).";
          }
          enum digital-signature {
            description
              "Select digital signature as the authentication method.";
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2)
               RFC 7427: Signature Authentication in the Internet Key
                         Exchange Version 2 (IKEv2).";
          }
          enum null {
            description
              "Null authentication.";
            reference
              "RFC 7619: The NULL Authentication Method in the Internet
                         Key Exchange Protocol Version 2 (IKEv2).";
          }
        }
        description
          "Peer authentication method specified in the Peer
           Authorization Database (PAD).";
      }

      container ipsec-ike {
        description
          "IKE configuration for an NSF.  It includes PAD
           parameters, IKE connection information, and state
           data.";
        container pad {
          description
            "Configuration of the Peer Authorization Database
             (PAD).  Each entry of PAD contains authentication
             information of either the local peer or the remote peer.
             Therefore, the I2NSF Controller stores authentication
             information (and credentials) not only for the remote NSF
             but also for the local NSF.  The local NSF MAY use the
             same identity for different types of authentication
             and credentials.  Pointing to the entry for a local NSF
             (e.g., A) and the entry for remote NSF (e.g., B)
             is possible to specify all the required information to
             carry out the authentication between A and B (see
             ../conn-entry/local and ../conn-entry/remote).";
          list pad-entry {
            key "name";
            ordered-by user;
            description
              "Peer Authorization Database (PAD) entry.  It
               is a list of PAD entries ordered by the
               I2NSF Controller, and each entry is
               unequivocally identified by a name.";
            leaf name {
              type string;
              description
                "PAD-unique name to identify this
                 entry.";
            }
            choice identity {
              mandatory true;
              description
                "A particular IKE peer will be
                 identified by one of these identities.
                 This peer can be a remote peer or local
                 peer (this NSF).";
              reference
                "RFC 4301: Security Architecture for the Internet
                           Protocol, Section 4.4.3.1.";
              case ipv4-address {
                leaf ipv4-address {
                  type inet:ipv4-address;
                  description
                    "Specifies the identity as
                     a single 4-octet IPv4 address.";
                }
              }
              case ipv6-address {
                leaf ipv6-address {
                  type inet:ipv6-address;
                  description
                    "Specifies the identity as a
                     single 16-octet IPv6
                     address.  An example is
                     2001:db8::8:800:200c:417a.";
                }
              }
              case fqdn-string {
                leaf fqdn-string {
                  type inet:domain-name;
                  description
                    "Specifies the identity as a
                     Fully Qualified Domain Name
                     (FQDN) string.  An example is
                     example.com.  The string MUST
                     NOT contain any terminators
                     (e.g., NULL, Carriage Return
                     (CR), etc.).";
                }
              }
              case rfc822-address-string {
                leaf rfc822-address-string {
                  type string;
                  description
                    "Specifies the identity as a
                     fully qualified  email address
                     string (RFC 5322).  An example is
                     jsmith@example.com.  The string
                     MUST NOT contain any
                     terminators (e.g., NULL, CR,
                     etc.).";
                  reference
                    "RFC 5322: Internet Message Format.";
                }
              }
              case dnx509 {
                leaf dnx509 {
                  type binary;
                  description
                    "The binary
                     Distinguished Encoding Rules (DER)
                     encoding of an ASN.1 X.500
                     Distinguished Name, as specified in IKEv2.";
                  reference
                    "RFC 5280: Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile
                     RFC 7296: Internet Key Exchange Protocol Version 2
                               (IKEv2), Section 3.5.";
                }
              }
              case gnx509 {
                leaf gnx509 {
                  type binary;
                  description
                    "ASN.1 X.509 GeneralName structure,
                     as specified in RFC 5280, encoded
                     using ASN.1 Distinguished Encoding Rules
                     (DER), as specified in ITU-T X.690.";
                  reference
                    "RFC 5280: Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile.";
                }
              }
              case id-key {
                leaf id-key {
                  type binary;
                  description
                    "Opaque octet stream that may be
                     used to pass vendor-specific
                     information for proprietary
                     types of identification.";
                  reference
                    "RFC 7296: Internet Key Exchange Protocol Version 2
                               (IKEv2), Section 3.5.";
                }
              }
              case id-null {
                leaf id-null {
                  type empty;
                  description
                    "The ID_NULL identification is used
                     when the IKE identification payload
                     is not used.";
                  reference
                    "RFC 7619: The NULL Authentication Method in the
                               Internet Key Exchange Protocol Version 2
                               (IKEv2).";
                }
              }
            }
            leaf auth-protocol {
              type auth-protocol-type;
              default "ikev2";
              description
                "Only IKEv2 is supported right now, but
                 other authentication protocols may be
                 supported in the future.";
            }
            container peer-authentication {
              description
                "This container allows the security
                 controller to configure the
                 authentication method (pre-shared key,
                 eap, digital-signature, null) that
                 will be used with a particular peer and
                 the credentials to use, which will
                 depend on the selected authentication
                 method.";
              leaf auth-method {
                type auth-method-type;
                default "pre-shared";
                description
                  "Type of authentication method
                   (pre-shared key, eap, digital signature,
                   null).";
                reference
                  "RFC 7296: Internet Key Exchange Protocol Version 2
                             (IKEv2), Section 2.15.";
              }
              container eap-method {
                when "../auth-method = 'eap'";
                leaf eap-type {
                  type uint32 {
                    range "1 .. 4294967295";
                  }
                  mandatory true;
                  description
                    "EAP method type specified with
                     a value extracted from the
                     IANA registry.  This
                     information provides the
                     particular EAP method to be
                     used.  Depending on the EAP
                     method, pre-shared keys or
                     certificates may be used.";
                }
                description
                  "EAP method description used when
                   authentication method is 'eap'.";
                reference
                  "IANA: Extensible Authentication Protocol (EAP)
                         Registry, Method Types
                   RFC 7296: Internet Key Exchange Protocol Version 2
                             (IKEv2), Section 2.16.";
              }
              container pre-shared {
                when "../auth-method[.='pre-shared' or
                      .='eap']";
                leaf secret {
                  nacm:default-deny-all;
                  type yang:hex-string;
                  description
                    "Pre-shared secret value.  The
                     NSF has to prevent read access
                     to this value for security
                     reasons.  This value MUST be
                     set if the EAP method uses a
                     pre-shared key or pre-shared
                     authentication has been chosen.";
                }
                description
                  "Shared secret value for PSK or
                   EAP method authentication based on
                   PSK.";
              }
              container digital-signature {
                when "../auth-method[.='digital-signature'
                      or .='eap']";
                leaf ds-algorithm {
                  type uint8;
                  default "14";
                  description
                    "The digital signature
                     algorithm is specified with a
                     value extracted from the IANA
                     registry.  Default is the generic
                     digital signature method.  Depending
                     on the algorithm, the following leafs
                     MUST contain information.  For
                     example, if digital signature or the
                     EAP method involves a certificate,
                     then leaves 'cert-data' and 'private-key'
                     will contain this information.";
                  reference
                    "IANA: Internet Key Exchange Version 2 (IKEv2)
                           Parameters, IKEv2 Authentication Method.";
                }
                choice public-key {
                  leaf raw-public-key {
                    type binary;
                    description
                      "A binary that contains the
                       value of the public key.  The
                       interpretation of the content
                       is defined by the digital
                       signature algorithm.  For
                       example, an RSA key is
                       represented as RSAPublicKey, as
                       defined in RFC 8017, and an
                       Elliptic Curve Cryptography
                       (ECC) key is represented
                       using the 'publicKey'
                       described in RFC 5915.";
                    reference
                      "RFC 5915: Elliptic Curve Private Key
                                 Structure
                       RFC 8017: PKCS #1: RSA Cryptography
                                 Specifications Version 2.2.";
                  }
                  leaf cert-data {
                    type binary;
                    description
                      "X.509 certificate data in DER
                       format.  If raw-public-key is
                       defined, this leaf is empty.";
                    reference
                      "RFC 5280: Internet X.509 Public Key
                                 Infrastructure Certificate
                                 and Certificate Revocation
                                 List (CRL) Profile.";
                  }
                  description
                    "If the I2NSF Controller
                     knows that the NSF
                     already owns a private key
                     associated to this public key
                     (e.g., the NSF generated the pair
                     public key/private key out of
                     band), it will only configure
                     one of the leaves of this
                     choice but not the leaf
                     private-key.  The NSF, based on
                     the public key value, can know
                     the private key to be used.";
                }
                leaf private-key {
                  nacm:default-deny-all;
                  type binary;
                  description
                    "A binary that contains the
                     value of the private key.  The
                     interpretation of the content
                     is defined by the digital
                     signature algorithm.  For
                     example, an RSA key is
                     represented as RSAPrivateKey, as
                     defined in RFC 8017, and an
                     Elliptic Curve Cryptography
                     (ECC) key is represented as
                     ECPrivateKey, as defined in RFC
                     5915.  This value is set
                     if public key is defined and the
                     I2NSF Controller is in charge
                     of configuring the
                     private key.  Otherwise, it is
                     not set and the value is
                     kept in secret.";
                  reference
                    "RFC 5915: Elliptic Curve Private Key
                               Structure
                     RFC 8017: PKCS #1: RSA Cryptography
                               Specifications Version 2.2.";
                }
                leaf-list ca-data {
                  type binary;
                  description
                    "List of trusted Certification
                     Authorities (CAs) certificates
                     encoded using ASN.1
                     Distinguished Encoding Rules
                     (DER).  If it is not defined,
                     the default value is empty.";
                }
                leaf crl-data {
                  type binary;
                  description
                    "A CertificateList structure, as
                     specified in RFC 5280,
                     encoded using ASN.1
                     Distinguished Encoding Rules
                     (DER), as specified in ITU-T
                     X.690.  If it is not defined,
                     the default value is empty.";
                  reference
                    "RFC 5280: Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile.";
                }
                leaf crl-uri {
                  type inet:uri;
                  description
                    "X.509 Certificate Revocation List
                     (CRL) certificate URI.
                     If it is not defined,
                     the default value is empty.";
                  reference
                    "RFC 5280: Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile.";
                }
                leaf oscp-uri {
                  type inet:uri;
                  description
                    "Online Certificate Status Protocol
                     (OCSP) URI.  If it is not defined,
                     the default value is empty.";
                  reference
                    "RFC 6960: X.509 Internet Public Key Infrastructure
                               Online Certificate Status Protocol - OCSP
                     RFC 5280: Internet X.509 Public Key Infrastructure
                               Certificate and Certificate Revocation
                               List (CRL) Profile.";
                }
                description
                  "digital-signature container.";
              } /*container digital-signature*/
            } /*container peer-authentication*/
          }
        }
        list conn-entry {
          key "name";
          description
            "IKE peer connection information.  This list
             contains the IKE connection for this peer
             with other peers.  This will create, in
             real time, IKE Security Associations
             established with these nodes.";
          leaf name {
            type string;
            description
              "Identifier for this connection
               entry.";
          }
          leaf autostartup {
            type autostartup-type;
            default "add";
            description
              "By default, only add configuration
               without starting the security
               association.";
          }
          leaf initial-contact {
            type boolean;
            default "false";
            description
              "The goal of this value is to deactivate the
               usage of INITIAL_CONTACT notification
               (true).  If this flag remains set to false, it
               means the usage of the INITIAL_CONTACT
               notification will depend on the IKEv2
               implementation.";
          }
          leaf version {
            type auth-protocol-type;
            default "ikev2";
            description
              "IKE version.  Only version 2 is supported.";
          }
          container fragmentation {
            leaf enabled {
              type boolean;
              default "false";
              description
                "Whether or not to enable IKEv2
                 fragmentation (true or false).";
              reference
                "RFC 7383: Internet Key Exchange Protocol Version 2
                           (IKEv2) Message Fragmentation.";
            }
            leaf mtu {
              when "../enabled='true'";
              type uint16 {
                range "68..65535";
              }
              description
                "MTU that IKEv2 can use
                 for IKEv2 fragmentation.";
              reference
                "RFC 7383: Internet Key Exchange Protocol Version 2
                           (IKEv2) Message Fragmentation.";
            }
            description
              "IKEv2 fragmentation, as per RFC 7383.  If the
               IKEv2 fragmentation is enabled, it is possible
               to specify the MTU.";
          }
          container ike-sa-lifetime-soft {
            description
              "IKE SA lifetime soft.  Two lifetime values
               can be configured: either rekey time of the
               IKE SA or reauth time of the IKE SA.  When
               the rekey lifetime expires, a rekey of the
               IKE SA starts.  When reauth lifetime
               expires, an IKE SA reauthentication starts.";
            leaf rekey-time {
              type uint32;
              units "seconds";
              default "0";
              description
                "Time in seconds between each IKE SA
                 rekey.  The value 0 means infinite.";
            }
            leaf reauth-time {
              type uint32;
              units "seconds";
              default "0";
              description
                "Time in seconds between each IKE SA
                 reauthentication.  The value 0 means
                 infinite.";
            }
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2), Section 2.8.";
          }
          container ike-sa-lifetime-hard {
            description
              "Hard IKE SA lifetime.  When this
               time is reached, the IKE SA is removed.";
            leaf over-time {
              type uint32;
              units "seconds";
              default "0";
              description
                "Time in seconds before the IKE SA is
                 removed.  The value 0 means infinite.";
            }
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2).";
          }
          leaf-list ike-sa-intr-alg {
            type nsfikec:intr-alg-t;
            default "12";
            ordered-by user;
            description
              "Integrity algorithm for establishing
               the IKE SA.  This list is ordered following
               from the higher priority to lower priority.
               The first node of the list will be the
               algorithm with higher priority.
               Default value 12 (AUTH_HMAC_SHA2_256_128).";
          }
          list ike-sa-encr-alg {
            key "id";
            min-elements 1;
            ordered-by user;
            leaf id {
              type uint16;
              description
                "An identifier that unequivocally
                 identifies each entry of the list,
                 i.e., an encryption algorithm and
                 its key length (if required).";
            }
            leaf algorithm-type {
              type nsfikec:encr-alg-t;
              default "12";
              description
                "Default value 12 (ENCR_AES_CBC).";
            }
            leaf key-length {
              type uint16;
              default "128";
              description
                "By default, key length is 128 bits.";
            }
            description
              "Encryption or AEAD algorithm for the IKE
               SAs.  This list is ordered following
               from the higher priority to lower priority.
               The first node of the list will be the
               algorithm with higher priority.";
          }
          leaf dh-group {
            type fs-group;
            default "14";
            description
              "Group number for Diffie-Hellman
               Exponentiation used during IKE_SA_INIT
               for the IKE SA key exchange.";
          }
          leaf half-open-ike-sa-timer {
            type uint32;
            units "seconds";
            default "0";
            description
              "Set the half-open IKE SA timeout
               duration.  The value 0 implies infinite.";
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2), Section 2.";
          }
          leaf half-open-ike-sa-cookie-threshold {
            type uint32;
            default "0";
            description
              "Number of half-open IKE SAs that activate
               the cookie mechanism.  The value 0 implies
               infinite.";
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2), Section 2.6.";
          }
          container local {
            leaf local-pad-entry-name {
              type string;
              mandatory true;
              description
                "Local peer authentication information.
                 This node points to a specific entry in
                 the PAD where the authorization
                 information about this particular local
                 peer is stored.  It MUST match a
                 pad-entry-name.";
            }
            description
              "Local peer authentication information.";
          }
          container remote {
            leaf remote-pad-entry-name {
              type string;
              mandatory true;
              description
                "Remote peer authentication information.
                 This node points to a specific entry in
                 the PAD where the authorization
                 information about this particular
                 remote peer is stored.  It MUST match a
                 pad-entry-name.";
            }
            description
              "Remote peer authentication information.";
          }
          container encapsulation-type {
            uses nsfikec:encap;
            description
              "This container carries configuration
               information about the source and destination
               ports of encapsulation that IKE should use
               and the type of encapsulation that
               should be used when NAT traversal is required.
               However, this is just a best effort since
               the IKE implementation may need to use a
               different encapsulation, as described in
               RFC 8229.";
            reference
              "RFC 8229: TCP Encapsulation of IKE and IPsec
                         Packets.";
          }
          container spd {
            description
              "Configuration of the Security Policy
               Database (SPD).  This main information is
               placed in the grouping
               ipsec-policy-grouping.";
            list spd-entry {
              key "name";
              ordered-by user;
              leaf name {
                type string;
                description
                  "SPD-entry-unique name to identify
                   the IPsec policy.";
              }
              container ipsec-policy-config {
                description
                  "This container carries the
                   configuration of an IPsec policy.";
                uses nsfikec:ipsec-policy-grouping;
              }
              description
                "List of entries that will constitute
                 the representation of the SPD.  In this
                 case, since the NSF implements IKE, it
                 is only required to send an IPsec policy
                 from this NSF where 'local' is this NSF
                 and 'remote' the other NSF.  The IKE
                 implementation will install IPsec
                 policies in the NSF's kernel in both
                 directions (inbound and outbound) and
                 their corresponding IPsec SAs based on
                 the information in this SPD entry.";
            }
            reference
              "RFC 7296: Internet Key Exchange Protocol Version 2
                         (IKEv2), Section 2.9.";
          }
          container child-sa-info {
            leaf-list fs-groups {
              type fs-group;
              default "0";
              ordered-by user;
              description
                "If non-zero, forward secrecy is
                 required when a new IPsec SA is being
                 created, the (non-zero) value indicates
                 the group number to use for the key
                 exchange process used to achieve forward
                 secrecy.
                 This list is ordered following from the
                 higher priority to lower priority.  The
                 first node of the list will be the
                 algorithm with higher priority.";
            }
            container child-sa-lifetime-soft {
              description
                "Soft IPsec SA lifetime.
                 After the lifetime, the action is
                 defined in this container
                 in the leaf action.";
              uses nsfikec:lifetime;
              leaf action {
                type nsfikec:lifetime-action;
                default "replace";
                description
                  "When the lifetime of an IPsec SA
                   expires, an action needs to be
                   performed over the IPsec SA that
                   reached the lifetime.  There are
                   three possible options:
                   terminate-clear, terminate-hold, and
                   replace.";
                reference
                  "RFC 4301: Security Architecture for the Internet
                             Protocol, Section 4.5
                   RFC 7296: Internet Key Exchange Protocol Version 2
                             (IKEv2), Section 2.8.";
              }
            }
            container child-sa-lifetime-hard {
              description
                "IPsec SA lifetime hard.  The action will
                 be to terminate the IPsec SA.";
              uses nsfikec:lifetime;
              reference
                "RFC 7296: Internet Key Exchange Protocol Version 2
                           (IKEv2), Section 2.8.";
            }
            description
              "Specific information for IPsec SAs.
               It includes the Perfect Forward Secrecy (PFS)
               group and IPsec SAs rekey lifetimes.";
          }
          container state {
            config false;
            leaf initiator {
              type boolean;
              description
                "It is acting as an initiator for this
                 connection.";
            }
            leaf initiator-ikesa-spi {
              type ike-spi;
              description
                "Initiator's IKE SA SPI.";
            }
            leaf responder-ikesa-spi {
              type ike-spi;
              description
                "Responder's IKE SA SPI.";
            }
            leaf nat-local {
              type boolean;
              description
                "True if local endpoint is behind a
                 NAT.";
            }
            leaf nat-remote {
              type boolean;
              description
                "True if remote endpoint is behind
                 a NAT.";
            }
            container encapsulation-type {
              uses nsfikec:encap;
              description
                "This container provides information
                 about the source and destination
                 ports of encapsulation that IKE is
                 using and the type of encapsulation
                 when NAT traversal is required.";
              reference
                "RFC 8229: TCP Encapsulation of IKE and IPsec Packets.";
            }
            leaf established {
              type uint64;
              units "seconds";
              description
                "Seconds since this IKE SA has been
                 established.";
            }
            leaf current-rekey-time {
              type uint64;
              units "seconds";
              description
                "Seconds before IKE SA is rekeyed.";
            }
            leaf current-reauth-time {
              type uint64;
              units "seconds";
              description
                "Seconds before IKE SA is
                 reauthenticated.";
            }
            description
              "IKE state data for a particular
               connection.";
          } /* ike-sa-state */
        } /* ike-conn-entries */
        container number-ike-sas {
          config false;
          leaf total {
            type yang:gauge64;
            description
              "Total number of active IKE SAs.";
          }
          leaf half-open {
            type yang:gauge64;
            description
              "Number of half-open active IKE SAs.";
          }
          leaf half-open-cookies {
            type yang:gauge64;
            description
              "Number of half-open active IKE SAs with
               cookie activated.";
          }
          description
            "General information about the IKE SAs.  In
             particular, it provides the current number of
             IKE SAs.";
        }
      } /* container ipsec-ike */
    }

    <CODE ENDS>

¶

### 5.3. The 'ietf-i2nsf-ikeless' Module

In this section, the YANG module for the IKE-less case is described.¶

#### 5.3.1. Data Model Overview

For this case, the definition of the SPD model has been mainly extracted from the specification in Section 4.4.1 and Appendix D in [RFC4301], though with some changes, namely:¶

- For simplicity, each IPsec policy (spd-entry) contains one Traffic Selector, instead of a list of them. The reason is that actual kernel implementations only admit a single Traffic Selector per IPsec policy.¶
- Each IPsec policy contains an identifier (reqid) to relate the policy with the IPsec SA. This is common in Linux-based systems.¶
- Each IPsec policy has only one name and not a list of names.¶
- Combined algorithms have been removed because encryption algorithms MAY include Authenticated Encryption with Associated Data (AEAD).¶
- Tunnel information has been extended with information about DSCP mapping. The reason is that certain kernel implementations accept configuration of these values.¶

The definition of the SAD model has been mainly extracted from the specification in Section 4.4.2 of [RFC4301], though with some changes, namely:¶

- For simplicity, each IPsec SA (sad-entry) contains one Traffic Selector, instead of a list of them. The reason is that actual kernel implementations only admit a single Traffic Selector per IPsec SA.¶
- Each IPsec SA contains an identifier (reqid) to relate the IPsec SA with the IPsec policy. The reason is that real kernel implementations allow this value to be included.¶
- Each IPsec SA is also named in the same way as IPsec policies.¶
- The model allows specifying the algorithm for encryption. This can be Authenticated Encryption with Associated Data (AEAD) or non-AEAD. If an AEAD algorithm is specified, the integrity algorithm is not required. If a non-AEAD algorithm is specified, the integrity algorithm is required [RFC8221].¶
- Tunnel information has been extended with information about Differentiated Services Code Point (DSCP) mapping. It is assumed that NSFs involved in this document provide ECN full functionality to prevent discarding of ECN congestion indications [RFC6040].¶
- The lifetime of the IPsec SAs also includes idle time and the number of IP packets as a threshold to trigger the lifetime. The reason is that actual kernel implementations allow for setting these types of lifetimes.¶
- Information to configure the type of encapsulation (encapsulation-type) for IPsec ESP packets in UDP [RFC3948] or TCP [RFC8229] has been included.¶

The notifications model has been defined using, as reference, the PF_KEYv2 specification in [RFC2367].¶

The YANG data model for the IKE-less case is defined by the module "ietf-i2nsf-ikeless". Its structure is depicted in the following diagram, using the notation syntax for YANG tree diagrams [RFC8340].¶

    module: ietf-i2nsf-ikeless
      +--rw ipsec-ikeless
        +--rw spd
        |  +--rw spd-entry* [name]
        |     +--rw name  string
        |     +--rw direction nsfikec:ipsec-traffic-direction
        |     +--rw reqid? uint64
        |     +--rw ipsec-policy-config
        |        +--rw anti-replay-window-size?   uint32
        |        +--rw traffic-selector
        |        |  +--rw local-prefix      inet:ip-prefix
        |        |  +--rw remote-prefix     inet:ip-prefix
        |        |  +--rw inner-protocol?   ipsec-inner-protocol
        |        |  +--rw local-ports* [start end]
        |        |  |  +--rw start    inet:port-number
        |        |  |  +--rw end      inet:port-number
        |        |  +--rw remote-ports* [start end]
        |        |     +--rw start    inet:port-number
        |        |     +--rw end      inet:port-number
        |        +--rw processing-info
        |           +--rw action?         ipsec-spd-action
        |           +--rw ipsec-sa-cfg
        |             +--rw pfp-flag?              boolean
        |             +--rw ext-seq-num?           boolean
        |             +--rw seq-overflow?          boolean
        |             +--rw stateful-frag-check?   boolean
        |             +--rw mode?                  ipsec-mode
        |             +--rw protocol-parameters? ipsec-protocol-params
        |              +--rw esp-algorithms
        |              |  +--rw integrity*    intr-alg-t
        |              |  +--rw encryption* [id]
        |              |  |  +--rw id                uint16
        |              |  |  +--rw algorithm-type?   encr-alg-t
        |              |  |  +--rw key-length?       uint16
        |              |  +--rw tfc-pad?      boolean
        |              +--rw tunnel
        |                 +--rw local           inet:ip-address
        |                 +--rw remote          inet:ip-address
        |                 +--rw df-bit?         enumeration
        |                 +--rw bypass-dscp?    boolean
        |                 +--rw dscp-mapping* [id]
        |                    +--rw id            uint8
        |                    +--rw inner-dscp?   inet:dscp
        |                    +--rw outer-dscp?   inet:dscp
        +--rw sad
          +--rw sad-entry* [name]
           +--rw name               string
           +--rw reqid?             uint64
           +--rw ipsec-sa-config
           |  +--rw spi                        uint32
           |  +--rw ext-seq-num?               boolean
           |  +--rw seq-overflow?              boolean
           |  +--rw anti-replay-window-size?   uint32
           |  +--rw traffic-selector
           |  |  +--rw local-prefix      inet:ip-prefix
           |  |  +--rw remote-prefix     inet:ip-prefix
           |  |  +--rw inner-protocol?   ipsec-inner-protocol
           |  |  +--rw local-ports* [start end]
           |  |  |  +--rw start    inet:port-number
           |  |  |  +--rw end      inet:port-number
           |  |  +--rw remote-ports* [start end]
           |  |     +--rw start    inet:port-number
           |  |     +--rw end      inet:port-number
           |  +--rw protocol-parameters? nsfikec:ipsec-protocol-params
           |  +--rw mode?                      nsfikec:ipsec-mode
           |  +--rw esp-sa
           |  |  +--rw encryption
           |  |  |  +--rw encryption-algorithm?   nsfikec:encr-alg-t
           |  |  |  +--rw key?                    yang:hex-string
           |  |  |  +--rw iv?                     yang:hex-string
           |  |  +--rw integrity
           |  |     +--rw integrity-algorithm?   nsfikec:intr-alg-t
           |  |     +--rw key?                   yang:hex-string
           |  +--rw sa-lifetime-hard
           |  |  +--rw time?      uint32
           |  |  +--rw bytes?     yang:counter64
           |  |  +--rw packets?   uint32
           |  |  +--rw idle?      uint32
           |  +--rw sa-lifetime-soft
           |  |  +--rw time?      uint32
           |  |  +--rw bytes?     yang:counter64
           |  |  +--rw packets?   uint32
           |  |  +--rw idle?      uint32
           |  |  +--rw action?    nsfikec:lifetime-action
           |  +--rw tunnel
           |  |  +--rw local           inet:ip-address
           |  |  +--rw remote          inet:ip-address
           |  |  +--rw df-bit?         enumeration
           |  |  +--rw bypass-dscp?    boolean
           |  |  +--rw dscp-mapping* [id]
           |  |  |  +--rw id            uint8
           |  |  |  +--rw inner-dscp?   inet:dscp
           |  |  |  +--rw outer-dscp?   inet:dscp
           |  |  +--rw dscp-values*    inet:dscp
           |  +--rw encapsulation-type
           |     +--rw espencap?   esp-encap
           |     +--rw sport?      inet:port-number
           |     +--rw dport?      inet:port-number
           |     +--rw oaddr*      inet:ip-address
           +--ro ipsec-sa-state
              +--ro sa-lifetime-current
              |  +--ro time?      uint32
              |  +--ro bytes?     yang:counter64
              |  +--ro packets?   uint32
              |  +--ro idle?      uint32
              +--ro replay-stats
                 +--ro replay-window
                 |  +--ro w?   uint32
                 |  +--ro t?   uint64
                 |  +--ro b?   uint64
                 +--ro packet-dropped?       yang:counter64
                 +--ro failed?               yang:counter64
                 +--ro seq-number-counter?   uint64

       notifications:
         +---n sadb-acquire {ikeless-notification}?
         |  +--ro ipsec-policy-name    string
         |  +--ro traffic-selector
         |     +--ro local-prefix      inet:ip-prefix
         |     +--ro remote-prefix     inet:ip-prefix
         |     +--ro inner-protocol?   ipsec-inner-protocol
         |     +--ro local-ports* [start end]
         |     |  +--ro start    inet:port-number
         |     |  +--ro end      inet:port-number
         |     +--ro remote-ports* [start end]
         |        +--ro start    inet:port-number
         |        +--ro end      inet:port-number
         +---n sadb-expire {ikeless-notification}?
         |  +--ro ipsec-sa-name           string
         |  +--ro soft-lifetime-expire?   boolean
         |  +--ro lifetime-current
         |     +--ro time?      uint32
         |     +--ro bytes?     yang:counter64
         |     +--ro packets?   uint32
         |     +--ro idle?      uint32
         +---n sadb-seq-overflow {ikeless-notification}?
         |  +--ro ipsec-sa-name    string
         +---n sadb-bad-spi {ikeless-notification}?
            +--ro spi    uint32

¶

The YANG data model consists of a unique "ipsec-ikeless" container, which, in turn, is composed of two additional containers: "spd" and "sad". The "spd" container consists of a list of entries that form the Security Policy Database. Compared to the IKE case YANG data model, this part specifies a few additional parameters necessary due to the absence of an IKE software in the NSF: traffic direction to apply the IPsec policy and a "reqid" value to link an IPsec policy with its associated IPsec SAs since it is otherwise a little hard to find by searching. The "sad" container is a list of entries that form the Security Association Database. In general, each entry allows specifying both configuration information (SPI, Traffic Selectors, tunnel/transport mode, cryptographic algorithms and keying material, soft/hard lifetimes, etc.) as well as stating information (time to expire, replay statistics, etc.) of a concrete IPsec SA.¶

In addition, the module defines a set of notifications to allow the NSF to inform the I2NSF Controller about relevant events, such as IPsec SA expiration, sequence number overflow, or bad SPI in a received packet.¶

#### 5.3.2. Example Usage

Appendix B shows an example of an IKE-less case configuration for an NSF in transport mode (host-to-host). Additionally, Appendix C shows examples of IPsec SA expire, acquire, sequence number overflow, and bad SPI notifications.¶

#### 5.3.3. YANG Module

This YANG module has normative references to [RFC4301], [RFC4303], [RFC6991], [RFC8174] and [RFC8341].¶

    <CODE BEGINS> file "ietf-i2nsf-ikeless@2021-07-14.yang"

    module ietf-i2nsf-ikeless {
      yang-version 1.1;
      namespace "urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless";
      prefix nsfikels;

      import ietf-inet-types {
        prefix inet;
        reference
          "RFC 6991: Common YANG Data Types.";
      }
      import ietf-yang-types {
        prefix yang;
        reference
          "RFC 6991: Common YANG Data Types.";
      }
      import ietf-i2nsf-ikec {
        prefix nsfikec;
        reference
          "RFC 9061: A YANG Data Model for IPsec Flow Protection
                     Based on Software-Defined Networking (SDN).";
      }
      import ietf-netconf-acm {
        prefix nacm;
        reference
          "RFC 8341: Network Configuration Access Control
                     Model.";
      }

      organization
        "IETF I2NSF Working Group";
      contact
        "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/>
         WG List: <mailto:i2nsf@ietf.org>

         Author: Rafael Marin-Lopez
                  <mailto:rafa@um.es>

         Author: Gabriel Lopez-Millan
                  <mailto:gabilm@um.es>

         Author: Fernando Pereniguez-Garcia
                  <mailto:fernando.pereniguez@cud.upct.es>
        ";
      description
        "Data model for IKE-less case in the SDN-based IPsec flow
         protection service.

         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) 2021 IETF Trust and the persons
         identified as authors of the code.  All rights reserved.

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

         This version of this YANG module is part of RFC 9061; see
         the RFC itself for full legal notices.";

      revision 2021-07-14 {
        description
          "Initial version.";
        reference
          "RFC 9061: A YANG Data Model for IPsec Flow Protection
                     Based on Software-Defined Networking (SDN).";
      }

      feature ikeless-notification {
        description
          "This feature indicates that the server supports
           generating notifications in the ikeless module.

           To ensure broader applicability of this module,
           the notifications are marked as a feature.
           For the implementation of the IKE-less case,
           the NSF is expected to implement this
           feature.";
      }

      container ipsec-ikeless {
        description
          "Container for configuration of the IKE-less
           case. The container contains two additional
           containers: 'spd' and 'sad'.  The first allows the
           I2NSF Controller to configure IPsec policies in
           the Security Policy Database (SPD), and the second
           allows the I2NSF Controller to configure IPsec
           Security Associations (IPsec SAs) in the Security
           Association Database (SAD).";
        reference
          "RFC 4301: Security Architecture for the Internet Protocol.";
        container spd {
          description
            "Configuration of the Security Policy Database
             (SPD).";
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.1.2.";
          list spd-entry {
            key "name";
            ordered-by user;
            leaf name {
              type string;
              description
                "SPD-entry-unique name to identify this
                 entry.";
            }
            leaf direction {
              type nsfikec:ipsec-traffic-direction;
              mandatory true;
              description
                "Inbound traffic or outbound
                 traffic.  In the IKE-less case, the
                 I2NSF Controller needs to
                 specify the policy direction to be
                 applied in the NSF.  In the IKE case,
                 this direction does not need to be
                 specified, since IKE
                 will determine the direction that the
                 IPsec policy will require.";
            }
            leaf reqid {
              type uint64;
              default "0";
              description
                "This value allows linking this
                 IPsec policy with IPsec SAs with the
                 same reqid.  It is only required in
                 the IKE-less model since, in the IKE
                 case, this link is handled internally
                 by IKE.";
            }
            container ipsec-policy-config {
              description
                "This container carries the
                 configuration of an IPsec policy.";
              uses nsfikec:ipsec-policy-grouping;
            }
            description
              "The SPD is represented as a list of SPD
               entries, where each SPD entry represents an
               IPsec policy.";
          } /*list spd-entry*/
        } /*container spd*/
        container sad {
          description
            "Configuration of the IPsec Security Association
             Database (SAD).";
          reference
            "RFC 4301: Security Architecture for the Internet Protocol,
                       Section 4.4.2.1.";
          list sad-entry {
            key "name";
            ordered-by user;
            leaf name {
              type string;
              description
                "SAD-entry-unique name to identify this
                 entry.";
            }
            leaf reqid {
              type uint64;
              default "0";
              description
                "This value allows linking this
                 IPsec SA with an IPsec policy with
                 the same reqid.";
            }
            container ipsec-sa-config {
              description
                "This container allows configuring
                 details of an IPsec SA.";
              leaf spi {
                type uint32 {
                  range "0..max";
                }
                mandatory true;
                description
                  "IPsec SA of Security Parameter Index (SPI).";
              }
              leaf ext-seq-num {
                type boolean;
                default "true";
                description
                  "True if this IPsec SA is using extended
                   sequence numbers.  If true, the 64-bit
                   extended sequence number counter is used;
                   if false, the normal 32-bit sequence
                   number counter is used.";
              }
              leaf seq-overflow {
                type boolean;
                default "false";
                description
                  "The flag indicating whether
                   overflow of the sequence number
                   counter should prevent transmission
                   of additional packets on the IPsec
                   SA (false) and, therefore, needs to
                   be rekeyed or whether rollover is
                   permitted (true).  If Authenticated
                   Encryption with Associated Data
                   (AEAD) is used (leaf
                   esp-algorithms/encryption/algorithm-type),
                   this flag MUST BE false. Setting this
                   flag to true is strongly discouraged.";
              }
              leaf anti-replay-window-size {
                type uint32;
                default "64";
                description
                  "To set the anti-replay window size.
                   The default value is set to 64,
                   following the recommendation in RFC 4303.";
                reference
                  "RFC 4303: IP Encapsulating Security Payload (ESP),
                             Section 3.4.3.";
              }
              container traffic-selector {
                uses nsfikec:selector-grouping;
                description
                  "The IPsec SA Traffic Selector.";
              }
              leaf protocol-parameters {
                type nsfikec:ipsec-protocol-params;
                default "esp";
                description
                  "Security protocol of IPsec SA, only
                   ESP so far.";
              }
              leaf mode {
                type nsfikec:ipsec-mode;
                default "transport";
                description
                  "Tunnel or transport mode.";
              }
              container esp-sa {
                when "../protocol-parameters = 'esp'";
                description
                  "In case the IPsec SA is an
                   Encapsulation Security Payload
                   (ESP), it is required to specify
                   encryption and integrity
                   algorithms and key materials.";
                container encryption {
                  description
                    "Configuration of encryption or
                     AEAD algorithm for IPsec
                     Encapsulation Security Payload
                     (ESP).";
                  leaf encryption-algorithm {
                    type nsfikec:encr-alg-t;
                    default "12";
                    description
                      "Configuration of ESP
                       encryption.  With AEAD
                       algorithms, the integrity-algorithm
                       leaf is not used.";
                  }
                  leaf key {
                    nacm:default-deny-all;
                    type yang:hex-string;
                    description
                      "ESP encryption key value.
                       If this leaf is not defined,
                       the key is not defined
                       (e.g., encryption is NULL).
                       The key length is
                       determined by the
                       length of the key set in
                       this leaf.  By default, it is
                       128 bits.";
                  }
                  leaf iv {
                    nacm:default-deny-all;
                    type yang:hex-string;
                    description
                      "ESP encryption IV value.  If
                       this leaf is not defined, the
                       IV is not defined (e.g.,
                       encryption is NULL).";
                  }
                }
                container integrity {
                  description
                    "Configuration of integrity for
                     IPsec Encapsulation Security
                     Payload (ESP).  This container
                     allows configuration of integrity
                     algorithms when no AEAD
                     algorithms are used and
                     integrity is required.";
                  leaf integrity-algorithm {
                    type nsfikec:intr-alg-t;
                    default "12";
                    description
                      "Message Authentication Code
                       (MAC) algorithm to provide
                       integrity in ESP (default
                       AUTH_HMAC_SHA2_256_128).
                       With AEAD algorithms,
                       the integrity leaf is not
                       used.";
                  }
                  leaf key {
                    nacm:default-deny-all;
                    type yang:hex-string;
                    description
                      "ESP integrity key value.
                       If this leaf is not defined,
                       the key is not defined (e.g.,
                       AEAD algorithm is chosen and
                       integrity algorithm is not
                       required).  The key length is
                       determined by the length of
                       the key configured.";
                  }
                }
              } /*container esp-sa*/
              container sa-lifetime-hard {
                description
                  "IPsec SA hard lifetime.  The action
                   associated is terminate and hold.";
                uses nsfikec:lifetime;
              }
              container sa-lifetime-soft {
                description
                  "IPsec SA soft lifetime.";
                uses nsfikec:lifetime;
                leaf action {
                  type nsfikec:lifetime-action;
                  description
                    "Action lifetime: terminate-clear,
                     terminate-hold, or replace.";
                }
              }
              container tunnel {
                when "../mode = 'tunnel'";
                uses nsfikec:tunnel-grouping;
                leaf-list dscp-values {
                  type inet:dscp;
                  description
                    "DSCP values allowed for ingress packets carried
                     over this IPsec SA.  If no values are specified, no
                     DSCP-specific filtering is applied.  When
                     ../bypass-dscp is false and a dscp-mapping is
                     defined, each value here would be the same as the
                     'inner' DSCP value for the DSCP mapping (list
                     dscp-mapping).";
                  reference
                    "RFC 4301: Security Architecture for the Internet
                               Protocol, Section 4.4.2.1.";
                }
                description
                  "Endpoints of the IPsec tunnel.";
              }
              container encapsulation-type {
                uses nsfikec:encap;
                description
                  "This container carries
                   configuration information about
                   the source and destination ports
                   that will be used for ESP
                   encapsulation of ESP packets and
                   the type of encapsulation when NAT
                   traversal is in place.";
              }
            } /*ipsec-sa-config*/
            container ipsec-sa-state {
              config false;
              description
                "Container describing IPsec SA state
                 data.";
              container sa-lifetime-current {
                uses nsfikec:lifetime;
                description
                  "SAD lifetime current.";
              }
              container replay-stats {
                description
                  "State data about the anti-replay
                   window.";
                container replay-window {
                  leaf w {
                    type uint32;
                    description
                      "Size of the replay window.";
                  }
                  leaf t {
                    type uint64;
                    description
                      "Highest sequence number
                       authenticated so far,
                       upper bound of window.";
                  }
                  leaf b {
                    type uint64;
                    description
                      "Lower bound of window.";
                  }
                  description
                    "This container contains three
                     parameters that define the state
                     of the replay window: window size (w),
                     highest sequence number authenticated (t),
                     and lower bound of the window (b), according
                     to Appendix A2.1 in RFC 4303 (w = t - b + 1).";
                  reference
                    "RFC 4303: IP Encapsulating Security Payload (ESP),
                               Appendix A.";
                }
                leaf packet-dropped {
                  type yang:counter64;
                  description
                    "Packets dropped
                     because they are
                     replay packets.";
                }
                leaf failed {
                  type yang:counter64;
                  description
                    "Number of packets detected out
                     of the replay window.";
                }
                leaf seq-number-counter {
                  type uint64;
                  description
                    "A 64-bit counter when this
                     IPsec SA is using Extended
                     Sequence Number or 32-bit
                     counter when it is not.
                     Current value of sequence
                     number.";
                }
              } /* container replay-stats*/
            } /*ipsec-sa-state*/
            description
              "List of SAD entries that form the SAD.";
          } /*list sad-entry*/
        } /*container sad*/
      } /*container ipsec-ikeless*/

      /* Notifications */

      notification sadb-acquire {
        if-feature "ikeless-notification";
        description
          "The NSF detects and notifies that
           an IPsec SA is required for an
           outbound IP packet that has matched an SPD entry.
           The traffic-selector container in this
           notification contains information about
           the IP packet that triggered this
           notification.";
        leaf ipsec-policy-name {
          type string;
          mandatory true;
          description
            "It contains the SPD entry name (unique) of
             the IPsec policy that hits the IP-packet-required
             IPsec SA.  It is assumed the
             I2NSF Controller will have a copy of the
             information of this policy so it can
             extract all the information with this
             unique identifier.  The type of IPsec SA is
             defined in the policy so the security
             controller can also know the type of IPsec
             SA that MUST be generated.";
        }
        container traffic-selector {
          description
            "The IP packet that triggered the acquire
             and requires an IPsec SA.  Specifically, it
             will contain the IP source/mask and IP
             destination/mask, protocol (udp, tcp,
             etc.), and source and destination
             ports.";
          uses nsfikec:selector-grouping;
        }
      }

      notification sadb-expire {
        if-feature "ikeless-notification";
        description
          "An IPsec SA expiration (soft or hard).";
        leaf ipsec-sa-name {
          type string;
          mandatory true;
          description
            "It contains the SAD entry name (unique) of
             the IPsec SA that is about to expire.  It is assumed
             the I2NSF Controller will have a copy of the
             IPsec SA information (except the cryptographic
             material and state data) indexed by this name
             (unique identifier) so it can know all the
             information (crypto algorithms, etc.) about
             the IPsec SA that has expired in order to
             perform a rekey (soft lifetime) or delete it
             (hard lifetime) with this unique identifier.";
        }
        leaf soft-lifetime-expire {
          type boolean;
          default "true";
          description
            "If this value is true, the lifetime expired is
             soft.  If it is false, the lifetime is hard.";
        }
        container lifetime-current {
          description
            "IPsec SA current lifetime.  If
             soft-lifetime-expired is true,
             this container is set with the
             lifetime information about current
             soft lifetime.
             It can help the NSF Controller
             to know which of the (soft) lifetime
             limits raised the event: time, bytes,
             packets, or idle.";
          uses nsfikec:lifetime;
        }
      }

      notification sadb-seq-overflow {
        if-feature "ikeless-notification";
        description
          "Sequence overflow notification.";
        leaf ipsec-sa-name {
          type string;
          mandatory true;
          description
            "It contains the SAD entry name (unique) of
             the IPsec SA that is about to have a sequence
             number overflow, and rollover is not permitted.
             When the NSF issues this event before reaching
             a sequence number, overflow is implementation
             specific and out of scope of this specification.
             It is assumed the I2NSF Controller will have a
             copy of the IPsec SA information (except the
             cryptographic material and state data) indexed
             by this name (unique identifier) so it can
             know all the information (crypto algorithms,
             etc.) about the IPsec SA in
             order to perform a rekey of the IPsec SA.";
        }
      }

      notification sadb-bad-spi {
        if-feature "ikeless-notification";
        description
          "Notify when the NSF receives a packet with an
           incorrect SPI (i.e., not present in the SAD).";
        leaf spi {
          type uint32 {
            range "0..max";
          }
          mandatory true;
          description
            "SPI number contained in the erroneous IPsec
             packet.";
        }
      }
    }

    <CODE ENDS>

¶

## 6. IANA Considerations

IANA has registered the following namespaces in the "ns" subregistry within the "IETF XML Registry" [RFC3688]:¶

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

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

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

IANA has registered the following YANG modules in the "YANG Module Names" registry [RFC6020]:¶

Name:
  ietf-i2nsf-ikec¶
Maintained by IANA:
  N¶
Namespace:
  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikec¶
Prefix:
  nsfikec¶
Reference:
  RFC 9061¶

Name:
  ietf-i2nsf-ike¶
Maintained by IANA:
  N¶
Namespace:
  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ike¶
Prefix:
  nsfike¶
Reference:
  RFC 9061¶

Name:
  ietf-i2nsf-ikeless¶
Maintained by IANA:
  N¶
Namespace:
  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless¶
Prefix:
  nsfikels¶
Reference:
  RFC 9061¶

## 7. Security Considerations

First of all, this document shares all the security issues of SDN that are specified in the Security Considerations sections of [ITU-T.Y.3300] and [RFC7426].¶

On the one hand, it is important to note that there MUST exist a security association between the I2NSF Controller and the NSFs to protect the critical information (cryptographic keys, configuration parameter, etc.) exchanged between these entities. The nature of and means to create that security association is out of the scope of this document (i.e., it is part of device provisioning or onboarding).¶

On the other hand, if encryption is mandatory for all traffic of an NSF, its default policy MUST be to drop (DISCARD) packets to prevent cleartext packet leaks. This default policy MUST be preconfigured in the startup configuration datastore in the NSF before the NSF contacts the I2NSF Controller. Moreover, the startup configuration datastore MUST be also preconfigured with the required ALLOW policies that allow the NSF to communicate with the I2NSF Controller once the NSF is deployed. This preconfiguration step is not carried out by the I2NSF Controller but by some other entity before the NSF deployment. In this manner, when the NSF starts/reboots, it will always first apply the configuration in the startup configuration before contacting the I2NSF Controller.¶

Finally, this section is divided in two parts in order to analyze different security considerations for both cases: NSF with IKEv2 (IKE case) and NSF without IKEv2 (IKE-less case). In general, the I2NSF Controller, as typically in the SDN paradigm, is a target for different type of attacks; see [SDNSecServ] and [SDNSecurity]. Thus, the I2NSF Controller is a key entity in the infrastructure and MUST be protected accordingly. In particular, the I2NSF Controller will handle cryptographic material; thus, the attacker may try to access this information. The impact is different depending on the IKE case or the IKE-less case.¶

### 7.1. IKE Case

In the IKE case, the I2NSF Controller sends IKEv2 credentials (PSK, public/private keys, certificates, etc.) to the NSFs using the security association between the I2NSF Controller and NSFs. The I2NSF Controller MUST NOT store the IKEv2 credentials after distributing them. Moreover, the NSFs MUST NOT allow the reading of these values once they have been applied by the I2NSF Controller (i.e., write-only operations). One option is to always return the same value (i.e., all 0s) if a read operation is carried out.¶

If the attacker has access to the I2NSF Controller during the period of time that key material is generated, it might have access to the key material. Since these values are used during NSF authentication in IKEv2, it may impersonate the affected NSFs. Several recommendations are important.¶

- IKEv2 configurations SHOULD adhere to the recommendations in [RFC8247].¶
- If PSK authentication is used in IKEv2, the I2NSF Controller MUST remove the PSK immediately after generating and distributing it.¶
- When public/private keys are used, the I2NSF Controller MAY generate both public key and private key. In such a case, the I2NSF Controller MUST remove the associated private key immediately after distributing them to the NSFs. Alternatively, the NSF MAY generate the private key and export only the public key to the I2NSF Controller. How the NSF generates these cryptographic materials (public key/ private keys) and exports the public key is out of scope of this document.¶
- If certificates are used, the NSF MAY generate the private key and export the public key for certification to the I2NSF Controller. How the NSF generates these cryptographic material (public key/ private keys) and exports the public key is out of scope of this document.¶

### 7.2. IKE-less Case

In the IKE-less case, the I2NSF Controller sends the IPsec SA information to the NSF's SAD that includes the private session keys required for integrity and encryption. The I2NSF Controller MUST NOT store the keys after distributing them. Moreover, the NSFs receiving private key material MUST NOT allow the reading of these values by any other entity (including the I2NSF Controller itself) once they have been applied (i.e., write-only operations) into the NSFs. Nevertheless, if the attacker has access to the I2NSF Controller during the period of time that key material is generated, it may obtain these values. In other words, the attacker might be able to observe the IPsec traffic and decrypt, or even modify and re-encrypt, the traffic between peers.¶

Finally, the security association between the I2NSF Controller and the NSFs MUST provide, at least, the same degree of protection as the one achieved by the IPsec SAs configured in the NSFs. In particular, the security association between the I2NSF Controller and the NSFs MUST provide forward secrecy if this property is to be achieved in the IPsec SAs that the I2NSF Controller configures in the NSFs. Similarly, the encryption algorithms used in the security association between the I2NSF Controller and the NSF MUST have, at least, the same strength (minimum strength of a 128-bit key) as the algorithms used to establish the IPsec SAs.¶

### 7.3. YANG Modules

The YANG modules specified in this document define 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 mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].¶

The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.¶

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

For the IKE case (ietf-i2nsf-ike):
  /ipsec-ike:
    The entire container in this module is sensitive to write operations. An attacker may add/modify the credentials to be used for the authentication (e.g., to impersonate an NSF), for the trust root (e.g., changing the trusted CA certificates), for the cryptographic algorithms (allowing a downgrading attack), for the IPsec policies (e.g., by allowing leaking of data traffic by changing to an allow policy), and in general, changing the IKE SA conditions and credentials between any NSF.¶
For the IKE-less case (ietf-i2nsf-ikeless):
  /ipsec-ikeless:
    The entire container in this module is sensitive to write operations. An attacker may add/modify/delete any IPsec policies (e.g., by allowing leaking of data traffic by changing to an allow policy) in the /ipsec-ikeless/spd container, add/modify/delete any IPsec SAs between two NSF by means of /ipsec-ikeless/sad container, and, in general, change any IPsec SAs and IPsec policies between any NSF.¶

Some of the readable data nodes in these YANG modules may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability:¶

For the IKE case (ietf-i2nsf-ike):
  /ipsec-ike/pad:
    This container includes sensitive information to read operations. This information MUST NOT be returned to a client. For example, cryptographic material configured in the NSFs (peer-authentication/pre-shared/secret and peer-authentication/digital-signature/private-key) are already protected by the NACM extension "default-deny-all" in this document.¶
For the IKE-less case (ietf-i2nsf-ikeless):
  /ipsec-ikeless/sad/sad-entry/ipsec-sa-config/esp-sa:
    This container includes symmetric keys for the IPsec SAs. For example, encryption/key contains an ESP encryption key value and encryption/iv contains an Initialization Vector value. Similarly, integrity/key has an ESP integrity key value. Those values MUST NOT be read by anyone and are protected by the NACM extension "default-deny-all" in this document.¶

## 8. References

### 8.1. Normative References

[IANA-Method-Type]
  IANA, "Method Type", <https://www.iana.org/assignments/eap-numbers/>.
[IANA-Protocols-Number]
  IANA, "Protocol Numbers", <https://www.iana.org/assignments/protocol-numbers/>.
[IKEv2-Auth-Method]
  IANA, "IKEv2 Authentication Method", <https://www.iana.org/assignments/ikev2-parameters/>.
[IKEv2-Parameters]
  IANA, "Internet Key Exchange Version 2 (IKEv2) Parameters", <https://www.iana.org/assignments/ikev2-parameters/>.
[IKEv2-Transform-Type-1]
  IANA, "Transform Type 1 - Encryption Algorithm Transform IDs", <https://www.iana.org/assignments/ikev2-parameters/>.
[IKEv2-Transform-Type-3]
  IANA, "Transform Type 3 - Integrity Algorithm Transform IDs", <https://www.iana.org/assignments/ikev2-parameters/>.
[IKEv2-Transform-Type-4]
  IANA, "Transform Type 4 - Diffie-Hellman Group Transform IDs", <https://www.iana.org/assignments/ikev2-parameters/>.
[ITU-T.X.690]
  International Telecommunication Union, "Information Technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1, February 2021.
[RFC2119]
  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC3947]
  Kivinen, T., Swander, B., Huttunen, A., and V. Volpe, "Negotiation of NAT-Traversal in the IKE", RFC 3947, DOI 10.17487/RFC3947, January 2005, <https://www.rfc-editor.org/info/rfc3947>.
[RFC3948]
  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC 3948, DOI 10.17487/RFC3948, January 2005, <https://www.rfc-editor.org/info/rfc3948>.
[RFC4301]
  Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4303]
  Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, <https://www.rfc-editor.org/info/rfc4303>.
[RFC5280]
  Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, <https://www.rfc-editor.org/info/rfc5280>.
[RFC5322]
  Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, October 2008, <https://www.rfc-editor.org/info/rfc5322>.
[RFC5915]
  Turner, S. and D. Brown, "Elliptic Curve Private Key Structure", RFC 5915, DOI 10.17487/RFC5915, June 2010, <https://www.rfc-editor.org/info/rfc5915>.
[RFC6020]
  Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, <https://www.rfc-editor.org/info/rfc6020>.
[RFC6241]
  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, <https://www.rfc-editor.org/info/rfc6241>.
[RFC6242]
  Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, <https://www.rfc-editor.org/info/rfc6242>.
[RFC6960]
  Santesson, S., Myers, M., Ankney, R., Malpani, A., Galperin, S., and C. Adams, "X.509 Internet Public Key Infrastructure Online Certificate Status Protocol - OCSP", RFC 6960, DOI 10.17487/RFC6960, June 2013, <https://www.rfc-editor.org/info/rfc6960>.
[RFC6991]
  Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, <https://www.rfc-editor.org/info/rfc6991>.
[RFC7296]
  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7383]
  Smyslov, V., "Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation", RFC 7383, DOI 10.17487/RFC7383, November 2014, <https://www.rfc-editor.org/info/rfc7383>.
[RFC7427]
  Kivinen, T. and J. Snyder, "Signature Authentication in the Internet Key Exchange Version 2 (IKEv2)", RFC 7427, DOI 10.17487/RFC7427, January 2015, <https://www.rfc-editor.org/info/rfc7427>.
[RFC7619]
  Smyslov, V. and P. Wouters, "The NULL Authentication Method in the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 7619, DOI 10.17487/RFC7619, August 2015, <https://www.rfc-editor.org/info/rfc7619>.
[RFC7950]
  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, <https://www.rfc-editor.org/info/rfc7950>.
[RFC8017]
  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, "PKCS #1: RSA Cryptography Specifications Version 2.2", RFC 8017, DOI 10.17487/RFC8017, November 2016, <https://www.rfc-editor.org/info/rfc8017>.
[RFC8040]
  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, <https://www.rfc-editor.org/info/rfc8040>.
[RFC8174]
  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8221]
  Wouters, P., Migault, D., Mattsson, J., Nir, Y., and T. Kivinen, "Cryptographic Algorithm Implementation Requirements and Usage Guidance for Encapsulating Security Payload (ESP) and Authentication Header (AH)", RFC 8221, DOI 10.17487/RFC8221, October 2017, <https://www.rfc-editor.org/info/rfc8221>.
[RFC8229]
  Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229, August 2017, <https://www.rfc-editor.org/info/rfc8229>.
[RFC8247]
  Nir, Y., Kivinen, T., Wouters, P., and D. Migault, "Algorithm Implementation Requirements and Usage Guidance for the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 8247, DOI 10.17487/RFC8247, September 2017, <https://www.rfc-editor.org/info/rfc8247>.
[RFC8340]
  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, <https://www.rfc-editor.org/info/rfc8340>.
[RFC8341]
  Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, <https://www.rfc-editor.org/info/rfc8341>.
[RFC8342]
  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, <https://www.rfc-editor.org/info/rfc8342>.
[RFC8446]
  Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, <https://www.rfc-editor.org/info/rfc8446>.

### 8.2. Informative References

[IPSECME-CONTROLLER-IKE]
  Carrel, D. and B. Weis, "IPsec Key Exchange using a Controller", Work in Progress, Internet-Draft, draft-carrel-ipsecme-controller-ike-01, 10 March 2019, <https://datatracker.ietf.org/doc/html/draft-carrel-ipsecme-controller-ike-01>.
[ITU-T.Y.3300]
  International Telecommunications Union, "Y.3300: Framework of software-defined networking", June 2014, <https://www.itu.int/rec/T-REC-Y.3300/en>.
[libreswan]
  The Libreswan Project, "Libreswan VPN software", <https://libreswan.org/>.
[netconf-vpn]
  Stefan Wallin, "Tutorial: NETCONF and YANG", January 2014, <https://ripe68.ripe.net/presentations/181-NETCONF-YANG-tutorial-43.pdf>.
[ONF-OpenFlow]
  Open Networking Foundation, "OpenFlow Switch Specification", Version 1.4.0 (Wire Protocol 0x05), October 2013, <https://www.opennetworking.org/wp-content/uploads/2014/10/openflow-spec-v1.4.0.pdf>.
[ONF-SDN-Architecture]
  Open Networking Foundation, "SDN architecture", Issue 1, June 2014, <https://www.opennetworking.org/wp-content/uploads/2013/02/TR_SDN_ARCH_1.0_06062014.pdf>.
[RFC2367]
  McDonald, D., Metz, C., and B. Phan, "PF_KEY Key Management API, Version 2", RFC 2367, DOI 10.17487/RFC2367, July 1998, <https://www.rfc-editor.org/info/rfc2367>.
[RFC3688]
  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, <https://www.rfc-editor.org/info/rfc3688>.
[RFC6040]
  Briscoe, B., "Tunnelling of Explicit Congestion Notification", RFC 6040, DOI 10.17487/RFC6040, November 2010, <https://www.rfc-editor.org/info/rfc6040>.
[RFC6071]
  Frankel, S. and S. Krishnan, "IP Security (IPsec) and Internet Key Exchange (IKE) Document Roadmap", RFC 6071, DOI 10.17487/RFC6071, February 2011, <https://www.rfc-editor.org/info/rfc6071>.
[RFC6437]
  Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/RFC6437, November 2011, <https://www.rfc-editor.org/info/rfc6437>.
[RFC7149]
  Boucadair, M. and C. Jacquenet, "Software-Defined Networking: A Perspective from within a Service Provider Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014, <https://www.rfc-editor.org/info/rfc7149>.
[RFC7426]
  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S., Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-Defined Networking (SDN): Layers and Architecture Terminology", RFC 7426, DOI 10.17487/RFC7426, January 2015, <https://www.rfc-editor.org/info/rfc7426>.
[RFC8192]
  Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R., and J. Jeong, "Interface to Network Security Functions (I2NSF): Problem Statement and Use Cases", RFC 8192, DOI 10.17487/RFC8192, July 2017, <https://www.rfc-editor.org/info/rfc8192>.
[RFC8329]
  Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R. Kumar, "Framework for Interface to Network Security Functions", RFC 8329, DOI 10.17487/RFC8329, February 2018, <https://www.rfc-editor.org/info/rfc8329>.
[SDNSecServ]
  Scott-Hayward, S., O'Callaghan, G., and P. Sezer, "Sdn Security: A Survey", 2013 IEEE SDN for Future Networks and Services (SDN4FNS), pp. 1-7, DOI 10.1109/SDN4FNS.2013.6702553, November 2013, <https://doi.org/10.1109/SDN4FNS.2013.6702553>.
[SDNSecurity]
  Kreutz, D., Ramos, F., and P. Verissimo, "Towards secure and dependable software-defined networks", Proceedings of the second ACM SIGCOMM workshop on Hot Topics in software defined networking, pp. 55-60, DOI 10.1145/2491185.2491199, August 2013, <https://doi.org/10.1145/2491185.2491199>.
[strongswan]
  CESNET, "strongSwan: the OpenSource IPsec-based VPN Solution", <https://www.strongswan.org/>.
[TRAN-IPSECME-YANG]
  Tran, K., Wang, H., Nagaraj, V. K., and X. Chen, "Yang Data Model for Internet Protocol Security (IPsec)", Work in Progress, Internet-Draft, draft-tran-ipsecme-yang-01, 18 March 2016, <https://datatracker.ietf.org/doc/html/draft-tran-ipsecme-yang-01>.

## Appendix A. XML Configuration Example for IKE Case (Gateway-to-Gateway)

This example shows an XML configuration file sent by the I2NSF Controller to establish an IPsec SA between two NSFs (see Figure 3) in tunnel mode (gateway-to-gateway) with ESP, with authentication based on X.509 certificates (simplified for brevity with "base64encodedvalue==") and applying the IKE case.¶

                              +------------------+
                              | I2NSF Controller |
                              +------------------+
                       I2NSF NSF-Facing |
                              Interface |
                      /-----------------+---------------\
                     /                                   \
                    /                                     \
       +----+  +--------+                            +--------+  +----+
       | h1 |--| nsf_h1 |== IPsec_ESP_Tunnel_mode == | nsf_h2 |--| h2 |
       +----+  +--------+                            +--------+  +----+
              :1        :100                       :200       :1

    (2001:db8:1:/64)          (2001:db8:123:/64)       (2001:db8:2:/64)

Figure 3: IKE Case, Tunnel Mode, X.509 Certificate Authentication

    <ipsec-ike xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ike"
    xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
      <pad>
        <pad-entry>
          <name>nsf_h1_pad</name>
          <ipv6-address>2001:db8:123::100</ipv6-address>
          <peer-authentication>
             <auth-method>digital-signature</auth-method>
             <digital-signature>
                <cert-data>base64encodedvalue==</cert-data>
                <private-key>base64encodedvalue==</private-key>
                <ca-data>base64encodedvalue==</ca-data>
             </digital-signature>
          </peer-authentication>
        </pad-entry>
        <pad-entry>
          <name>nsf_h2_pad</name>
          <ipv6-address>2001:db8:123::200</ipv6-address>
          <auth-protocol>ikev2</auth-protocol>
          <peer-authentication>
            <auth-method>digital-signature</auth-method>
            <digital-signature>
              <!-- RSA Digital Signature -->
              <ds-algorithm>1</ds-algorithm>
              <cert-data>base64encodedvalue==</cert-data>
              <ca-data>base64encodedvalue==</ca-data>
            </digital-signature>
          </peer-authentication>
        </pad-entry>
      </pad>
      <conn-entry>
         <name>nsf_h1-nsf_h2</name>
         <autostartup>start</autostartup>
         <version>ikev2</version>
         <initial-contact>false</initial-contact>
         <fragmentation><enabled>false</enabled></fragmentation>
         <ike-sa-lifetime-soft>
            <rekey-time>60</rekey-time>
            <reauth-time>120</reauth-time>
         </ike-sa-lifetime-soft>
         <ike-sa-lifetime-hard>
            <over-time>3600</over-time>
         </ike-sa-lifetime-hard>
         <!--AUTH_HMAC_SHA2_512_256-->
         <ike-sa-intr-alg>14</ike-sa-intr-alg>
         <!--ENCR_AES_CBC - 128 bits-->
         <ike-sa-encr-alg>
            <id>1</id>
         </ike-sa-encr-alg>
         <!--8192-bit MODP Group-->
         <dh-group>18</dh-group>
         <half-open-ike-sa-timer>30</half-open-ike-sa-timer>
         <half-open-ike-sa-cookie-threshold>
            15
         </half-open-ike-sa-cookie-threshold>
         <local>
             <local-pad-entry-name>nsf_h1_pad</local-pad-entry-name>
         </local>
         <remote>
             <remote-pad-entry-name>nsf_h2_pad</remote-pad-entry-name>
         </remote>
         <spd>
           <spd-entry>
              <name>nsf_h1-nsf_h2</name>
              <ipsec-policy-config>
                <anti-replay-window-size>64</anti-replay-window-size>
                <traffic-selector>
                   <local-prefix>2001:db8:1::0/64</local-prefix>
                   <remote-prefix>2001:db8:2::0/64</remote-prefix>
                   <inner-protocol>any</inner-protocol>
                </traffic-selector>
                <processing-info>
                   <action>protect</action>
                   <ipsec-sa-cfg>
                      <pfp-flag>false</pfp-flag>
                      <ext-seq-num>true</ext-seq-num>
                      <seq-overflow>false</seq-overflow>
                      <stateful-frag-check>false</stateful-frag-check>
                      <mode>tunnel</mode>
                      <protocol-parameters>esp</protocol-parameters>
                      <esp-algorithms>
                         <!-- AUTH_HMAC_SHA1_96 -->
                         <integrity>2</integrity>
                          <encryption>
                              <!-- ENCR_AES_CBC -->
                              <id>1</id>
                              <algorithm-type>12</algorithm-type>
                              <key-length>128</key-length>
                          </encryption>
                          <encryption>
                              <!-- ENCR_3DES-->
                              <id>2</id>
                              <algorithm-type>3</algorithm-type>
                          </encryption>
                         <tfc-pad>false</tfc-pad>
                      </esp-algorithms>
                      <tunnel>
                         <local>2001:db8:123::100</local>
                         <remote>2001:db8:123::200</remote>
                         <df-bit>clear</df-bit>
                         <bypass-dscp>true</bypass-dscp>
                     </tunnel>
                   </ipsec-sa-cfg>
                </processing-info>
              </ipsec-policy-config>
           </spd-entry>
         </spd>
         <child-sa-info>
            <!--8192-bit MODP Group -->
            <fs-groups>18</fs-groups>
            <child-sa-lifetime-soft>
               <bytes>1000000</bytes>
               <packets>1000</packets>
               <time>30</time>
               <idle>60</idle>
               <action>replace</action>
            </child-sa-lifetime-soft>
            <child-sa-lifetime-hard>
               <bytes>2000000</bytes>
               <packets>2000</packets>
               <time>60</time>
               <idle>120</idle>
            </child-sa-lifetime-hard>
         </child-sa-info>
       </conn-entry>
    </ipsec-ike>

¶

## Appendix B. XML Configuration Example for IKE-less Case (Host-to-Host)

This example shows an XML configuration file sent by the I2NSF Controller to establish an IPsec SA between two NSFs (see Figure 4) in transport mode (host-to-host) with ESP in the IKE-less case.¶

                       +------------------+
                       | I2NSF Controller |
                       +------------------+
               I2NSF NSF-Facing |
                      Interface |
           /--------------------+-------------------\
          /                                          \
         /                                            \
    +--------+                                    +--------+
    | nsf_h1 |===== IPsec_ESP_Transport_mode =====| nsf_h2 |
    +--------+                                    +--------+
            :100        (2001:db8:123:/64)       :200

Figure 4: IKE-less Case, Transport Mode

    <ipsec-ikeless
      xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless"
      xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
      <spd>
        <spd-entry>
            <name>
               in/trans/2001:db8:123::200/2001:db8:123::100
            </name>
            <direction>inbound</direction>
            <reqid>1</reqid>
            <ipsec-policy-config>
               <traffic-selector>
                 <local-prefix>2001:db8:123::200/128</local-prefix>
                 <remote-prefix>2001:db8:123::100/128</remote-prefix>
                 <inner-protocol>any</inner-protocol>
               </traffic-selector>
               <processing-info>
                  <action>protect</action>
                  <ipsec-sa-cfg>
                    <ext-seq-num>true</ext-seq-num>
                    <seq-overflow>false</seq-overflow>
                    <mode>transport</mode>
                    <protocol-parameters>esp</protocol-parameters>
                    <esp-algorithms>
                       <!--AUTH_HMAC_SHA1_96-->
                       <integrity>2</integrity>
                       <!--ENCR_AES_CBC -->
                       <encryption>
                         <id>1</id>
                         <algorithm-type>12</algorithm-type>
                          <key-length>128</key-length>
                       </encryption>
                       <encryption>
                         <id>2</id>
                         <algorithm-type>3</algorithm-type>
                       </encryption>
                    </esp-algorithms>
                  </ipsec-sa-cfg>
                </processing-info>
              </ipsec-policy-config>
            </spd-entry>
            <spd-entry>
              <name>out/trans/2001:db8:123::100/2001:db8:123::200</name>
              <direction>outbound</direction>
              <reqid>1</reqid>
              <ipsec-policy-config>
                <traffic-selector>
                  <local-prefix>2001:db8:123::100/128</local-prefix>
                  <remote-prefix>2001:db8:123::200/128</remote-prefix>
                  <inner-protocol>any</inner-protocol>
                </traffic-selector>
                <processing-info>
                  <action>protect</action>
                  <ipsec-sa-cfg>
                    <ext-seq-num>true</ext-seq-num>
                    <seq-overflow>false</seq-overflow>
                    <mode>transport</mode>
                    <protocol-parameters>esp</protocol-parameters>
                    <esp-algorithms>
                      <!-- AUTH_HMAC_SHA1_96 -->
                      <integrity>2</integrity>
                      <!-- ENCR_AES_CBC -->
                      <encryption>
                         <id>1</id>
                         <algorithm-type>12</algorithm-type>
                         <key-length>128</key-length>
                      </encryption>
                      <encryption>
                         <id>2</id>
                         <algorithm-type>3</algorithm-type>
                      </encryption>
                    </esp-algorithms>
                   </ipsec-sa-cfg>
                 </processing-info>
               </ipsec-policy-config>
            </spd-entry>
         </spd>
         <sad>
           <sad-entry>
             <name>out/trans/2001:db8:123::100/2001:db8:123::200</name>
             <reqid>1</reqid>
             <ipsec-sa-config>
                <spi>34501</spi>
                <ext-seq-num>true</ext-seq-num>
                <seq-overflow>false</seq-overflow>
                <anti-replay-window-size>64</anti-replay-window-size>
                <traffic-selector>
                  <local-prefix>2001:db8:123::100/128</local-prefix>
                  <remote-prefix>2001:db8:123::200/128</remote-prefix>
                     <inner-protocol>any</inner-protocol>
                 </traffic-selector>
                 <protocol-parameters>esp</protocol-parameters>
                 <mode>transport</mode>
                 <esp-sa>
                   <encryption>
                      <!-- //ENCR_AES_CBC -->
                      <encryption-algorithm>12</encryption-algorithm>
                      <key>01:23:45:67:89:AB:CE:DF</key>
                      <iv>01:23:45:67:89:AB:CE:DF</iv>
                   </encryption>
                   <integrity>
                      <!-- //AUTH_HMAC_SHA1_96 -->
                      <integrity-algorithm>2</integrity-algorithm>
                      <key>01:23:45:67:89:AB:CE:DF</key>
                   </integrity>
                 </esp-sa>
             </ipsec-sa-config>
           </sad-entry>
           <sad-entry>
              <name>in/trans/2001:db8:123::200/2001:db8:123::100</name>
              <reqid>1</reqid>
              <ipsec-sa-config>
                  <spi>34502</spi>
                  <ext-seq-num>true</ext-seq-num>
                  <seq-overflow>false</seq-overflow>
                  <anti-replay-window-size>64</anti-replay-window-size>
                  <traffic-selector>
                     <local-prefix>2001:db8:123::200/128</local-prefix>
                     <remote-prefix>2001:db8:123::100/128</remote-prefix>
                     <inner-protocol>any</inner-protocol>
                  </traffic-selector>
                  <protocol-parameters>esp</protocol-parameters>
                  <mode>transport</mode>
                  <esp-sa>
                     <encryption>
                        <!-- //ENCR_AES_CBC -->
                        <encryption-algorithm>12</encryption-algorithm>
                        <key>01:23:45:67:89:AB:CE:DF</key>
                        <iv>01:23:45:67:89:AB:CE:DF</iv>
                     </encryption>
                     <integrity>
                        <!-- //AUTH_HMAC_SHA1_96 -->
                        <integrity-algorithm>2</integrity-algorithm>
                        <key>01:23:45:67:89:AB:CE:DF</key>
                     </integrity>
                   </esp-sa>
                   <sa-lifetime-hard>
                      <bytes>2000000</bytes>
                      <packets>2000</packets>
                      <time>60</time>
                      <idle>120</idle>
                   </sa-lifetime-hard>
                   <sa-lifetime-soft>
                      <bytes>1000000</bytes>
                      <packets>1000</packets>
                      <time>30</time>
                      <idle>60</idle>
                      <action>replace</action>
                   </sa-lifetime-soft>
             </ipsec-sa-config>
           </sad-entry>
        </sad>
    </ipsec-ikeless>

¶

## Appendix C. XML Notification Examples

In the following, several XML files are shown to illustrate different types of notifications defined in the IKE-less YANG data model, which are sent by the NSF to the I2NSF Controller. The notifications happen in the IKE-less case.¶

    <sadb-expire xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless">
    <ipsec-sa-name>in/trans/2001:db8:123::200/2001:db8:123::100
    </ipsec-sa-name>
        <soft-lifetime-expire>true</soft-lifetime-expire>
           <lifetime-current>
              <bytes>1000000</bytes>
              <packets>1000</packets>
              <time>30</time>
              <idle>60</idle>
           </lifetime-current>
    </sadb-expire>

Figure 5: Example of the sadb-expire Notification

    <sadb-acquire xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless">
        <ipsec-policy-name>in/trans/2001:db8:123::200/2001:db8:123::100
        </ipsec-policy-name>
        <traffic-selector>
            <local-prefix>2001:db8:123::200/128</local-prefix>
            <remote-prefix>2001:db8:123::100/128</remote-prefix>
            <inner-protocol>any</inner-protocol>
             <local-ports>
                  <start>0</start>
                  <end>0</end>
             </local-ports>
             <remote-ports>
                  <start>0</start>
                  <end>0</end>
             </remote-ports>
        </traffic-selector>
    </sadb-acquire>

Figure 6: Example of the sadb-acquire Notification

    <sadb-seq-overflow
        xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless">
          <ipsec-sa-name>in/trans/2001:db8:123::200/2001:db8:123::100
          </ipsec-sa-name>
    </sadb-seq-overflow>

Figure 7: Example of the sadb-seq-overflow Notification

    <sadb-bad-spi
             xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless">
            <spi>666</spi>
    </sadb-bad-spi>

Figure 8: Example of the sadb-bad-spi Notification

## Appendix D. Operational Use Case Examples

### D.1. Example of IPsec SA Establishment

This appendix exemplifies the applicability of the IKE case and IKE-less case to traditional IPsec configurations, that is, host-to-host and gateway-to-gateway. The following examples assume the existence of two NSFs needing to establish an end-to-end IPsec SA to protect their communications. Both NSFs could be two hosts that exchange traffic (host-to-host) or gateways (gateway-to-gateway), for example, within an enterprise that needs to protect the traffic between the networks of two branch offices.¶

Applicability of these configurations appear in current and new networking scenarios. For example, SD-WAN technologies are providing dynamic and on-demand VPN connections between branch offices or between branches and Software as a Service (SaaS) cloud services. Besides, Infrastructure as a Service (IaaS) services providing virtualization environments are deployments that often rely on IPsec to provide secure channels between virtual instances (host-to-host) and providing VPN solutions for virtualized networks (gateway-to-gateway).¶

As can be observed in the following, the I2NSF-based IPsec management system (for IKE and IKE-less cases) exhibits various advantages:¶

1. It allows creating IPsec SAs among two NSFs, based only on the application of general flow-based protection policies at the I2NSF User. Thus, administrators can manage all security associations in a centralized point with an abstracted view of the network.¶
2. Any NSF deployed in the system does not need manual configuration, therefore, allowing its deployment in an automated manner.¶

#### D.1.1. IKE Case

              +----------------------------------------+
              |  I2NSF User  (IPsec Management System) |
              +----------------------------------------+
                        |
               (1)    Flow-based    I2NSF Consumer-Facing
                   Protection Policy       Interface
                        |
              +---------|------------------------------+
              |         |                              |
              |         |   I2NSF Controller           |
              |         V                              |
              |   +--------------+ (2)+--------------+ |
              |   |Translate into|--->|   NETCONF/   | |
              |   |IPsec Policies|    |   RESTCONF   | |
              |   +--------------+    +--------------+ |
              |                          |     |       |
              |                          |     |       |
              +--------------------------|-----|-------+
                                         |     |
             I2NSF NSF-Facing Interface  |     |
                                         | (3) |
               |-------------------------+     +---|
               V                                   V
       +----------------------+         +----------------------+
       |       NSF A          |         |        NSF B         |
       | IKEv2/IPsec(SPD/PAD) |         | IKEv2/IPsec(SPD/PAD) |
       +----------------------+         +----------------------+

Figure 9: Host-to-Host/Gateway-to-Gateway for the IKE Case

Figure 9 describes the application of the IKE case when a data packet needs to be protected in the path between NSF A and NSF B:¶

1. The I2NSF User defines a general flow-based protection policy (e.g., protect data traffic between NSF A and B). The I2NSF Controller looks for the NSFs involved (NSF A and NSF B).¶
2. The I2NSF Controller generates IKEv2 credentials for them and translates the policies into SPD and PAD entries.¶
3. The I2NSF Controller inserts an IKEv2 configuration that includes the SPD and PAD entries in both NSF A and NSF B. If some of operations with NSF A and NSF B fail, the I2NSF Controller will stop the process and perform a rollback operation by deleting any IKEv2, SPD, and PAD configuration that had been successfully installed in NSF A or B.¶

If the previous steps are successful, the flow is protected by means of the IPsec SA established with IKEv2 between NSF A and NSF B.¶

#### D.1.2. IKE-less Case

            +----------------------------------------+
            | I2NSF User  (IPsec Management System)  |
            +----------------------------------------+
                      |
           (1)   Flow-based       I2NSF Consumer-Facing
              Protection Policy      Interface
                      |
            +---------|------------------------------+
            |         |                              |
            |         |   I2NSF Controller           |
            |         V                              |
            |  +--------------+ (2) +--------------+ |
            |  |Translate into|---->|   NETCONF/   | |
            |  |IPsec Policies|     |   RESTCONF   | |
            |  +--------------+     +--------------+ |
            |                         |     |        |
            +-------------------------|-----|--------+
                                      |     |
           I2NSF NSF-Facing Interface |     |
                                      | (3) |
               |----------------------+     +--|
               V                               V
      +----------------+             +----------------+
      |     NSF A      |             |     NSF B      |
      | IPsec(SPD/SAD) |             | IPsec(SPD/SAD) |
      +----------------+             +----------------+

Figure 10: Host-to-Host/Gateway-to-Gateway for the IKE-less Case

Figure 10 describes the application of the IKE-less case when a data packet needs to be protected in the path between NSF A and NSF B:¶

1. The I2NSF User establishes a general flow-based protection policy, and the I2NSF Controller looks for the involved NSFs.¶
2. The I2NSF Controller translates the flow-based security policies into IPsec SPD and SAD entries.¶

3. The I2NSF Controller inserts these entries in both NSF A and NSF B IPsec databases (i.e., SPD and SAD). The following text describes how this would happen:¶

   - The I2NSF Controller chooses two random values as SPIs, for example, SPIa1 for the inbound IPsec SA in NSF A and SPIb1 for the inbound IPsec SA in NSF B. The value of the SPIa1 MUST NOT be the same as any inbound SPI in A. In the same way, the value of the SPIb1 MUST NOT be the same as any inbound SPI in B. Moreover, the SPIa1 MUST be used in B for the outbound IPsec SA to A, while SPIb1 MUST be used in A for the outbound IPsec SA to B. It also generates fresh cryptographic material for the new inbound/outbound IPsec SAs and their parameters.¶
   - After that, the I2NSF Controller simultaneously sends the new inbound IPsec SA with SPIa1 and new outbound IPsec SA with SPIb1 to NSF A and the new inbound IPsec SA with SPIb1 and new outbound IPsec SA with SPIa1 to B, together with the corresponding IPsec policies.¶
   - Once the I2NSF Controller receives confirmation from NSF A and NSF B, it knows that the IPsec SAs are correctly installed and ready.¶

   Another alternative to this operation is the I2NSF Controller first sends the IPsec policies and new inbound IPsec SAs to A and B. Once it obtains a successful confirmation of these operations from NSF A and NSF B, it proceeds with installing the new outbound IPsec SAs. Even though this procedure may increase the latency to complete the process, no traffic is sent over the network until the IPsec SAs are completely operative. In any case, other alternatives MAY be possible to implement step 3.¶

4. If some of the operations described above fail (e.g., NSF A reports an error when the I2NSF Controller is trying to install the SPD entry, the new inbound or outbound IPsec SAs), the I2NSF Controller MUST perform rollback operations by deleting any new inbound or outbound IPsec SA and SPD entry that had been successfully installed in any of the NSFs (e.g., NSF B) and stop the process. Note that the I2NSF Controller MAY retry several times before giving up.¶
5. Otherwise, if the steps 1 to 3 are successful, the flow between NSF A and NSF B is protected by means of the IPsec SAs established by the I2NSF Controller. It is worth mentioning that the I2NSF Controller associates a lifetime to the new IPsec SAs. When this lifetime expires, the NSF will send a sadb-expire notification to the I2NSF Controller in order to start the rekeying process.¶

Instead of installing IPsec policies (in the SPD) and IPsec SAs (in the SAD) in step 3 (proactive mode), it is also possible that the I2NSF Controller only installs the SPD entries in step 3 (reactive mode). In such a case, when a data packet requires to be protected with IPsec, the NSF that first saw the data packet will send a sadb-acquire notification that informs the I2NSF Controller that needs SAD entries with the IPsec SAs to process the data packet. Again, if some of the operations installing the new inbound/outbound IPsec SAs fail, the I2NSF Controller stops the process and performs a rollback operation by deleting any new inbound/outbound SAs that had been successfully installed.¶

### D.2. Example of the Rekeying Process in IKE-less Case

To explain an example of the rekeying process between two IPsec NSFs, A and B, assume that SPIa1 identifies the inbound IPsec SA in A and SPIb1 identifies the inbound IPsec SA in B. The rekeying process will take the following steps:¶

1. The I2NSF Controller chooses two random values as SPI for the new inbound IPsec SAs, for example, SPIa2 for the inbound IPsec SA in A and SPIb2 for the inbound IPsec SA in B. The value of the SPIa1 MUST NOT be the same as any inbound SPI in A. In the same way, the value of the SPIb1 MUST NOT be the same as any inbound SPI in B. Then, the I2NSF Controller creates an inbound IPsec SA with SPIa2 in A and another inbound IPsec SA in B with SPIb2. It can send this information simultaneously to A and B.¶
2. Once the I2NSF Controller receives confirmation from A and B, the controller knows that the inbound IPsec SAs are correctly installed. Then, it proceeds to send, in parallel to A and B, the outbound IPsec SAs: the outbound IPsec SA to A with SPIb2 and the outbound IPsec SA to B with SPIa2. At this point, the new IPsec SAs are ready.¶
3. Once the I2NSF Controller receives confirmation from A and B that the outbound IPsec SAs have been installed, the I2NSF Controller, in parallel, deletes the old IPsec SAs from A (inbound SPIa1 and outbound SPIb1) and B (outbound SPIa1 and inbound SPIb1).¶

If some of the operations in step 1 fail (e.g., NSF A reports an error when the I2NSF Controller is trying to install a new inbound IPsec SA), the I2NSF Controller MUST perform rollback operations by removing any new inbound SA that had been successfully installed during step 1.¶

If step 1 is successful but some of the operations in step 2 fail (e.g., NSF A reports an error when the I2NSF Controller is trying to install the new outbound IPsec SA), the I2NSF Controller MUST perform a rollback operation by deleting any new outbound SA that had been successfully installed during step 2 and by deleting the inbound SAs created in step 1, in that order.¶

If the steps 1 and 2 are successful but the step 3 fails, the I2NSF Controller will avoid any rollback of the operations carried out in steps 1 and 2, since new and valid IPsec SAs were created and are functional. The I2NSF Controller MAY reattempt to remove the old inbound and outbound IPsec SAs in NSF A and NSF B several times until it receives a success or it gives up. In the last case, the old IPsec SAs will be removed when their corresponding hard lifetime is reached.¶

### D.3. Example of Managing NSF State Loss in the IKE-less Case

In the IKE-less case, if the I2NSF Controller detects that an NSF has lost the IPsec state, it could follow the next steps:¶

1. The I2NSF Controller SHOULD delete the old IPsec SAs on the non-failed nodes, established with the failed node. This prevents the non-failed nodes from leaking plaintext.¶
2. If the affected node restarts, the I2NSF Controller configures the new inbound IPsec SAs between the affected node and all the nodes it was talking to.¶
3. After these inbound IPsec SAs have been established, the I2NSF Controller configures the outbound IPsec SAs in parallel.¶

Steps 2 and 3 can be performed at the same time at the cost of a potential packet loss. If this is not critical, then it is an optimization since the number of exchanges between the I2NSF Controller and NSFs is lower.¶

## Acknowledgements

Authors want to thank Paul Wouters, Valery Smyslov, Sowmini Varadhan, David Carrel, Yoav Nir, Tero Kivinen, Martin Bjorklund, Graham Bartlett, Sandeep Kampati, Linda Dunbar, Mohit Sethi, Martin Bjorklund, Tom Petch, Christian Hopps, Rob Wilton, Carlos J. Bernardos, Alejandro Perez-Mendez, Alejandro Abad-Carrascosa, Ignacio Martinez, Ruben Ricart, and all IESG members that have reviewed this document for their valuable comments.¶

## Authors' Addresses