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Versions: (draft-abad-i2nsf-sdn-ipsec-flow-protection) 00 01 02 03 04 05 06 07 08 09 10 11 12

I2NSF                                                     R. Marin-Lopez
Internet-Draft                                           G. Lopez-Millan
Intended status: Standards Track                    University of Murcia
Expires: April 24, 2021                             F. Pereniguez-Garcia
                                               University Defense Center
                                                        October 21, 2020


     Software-Defined Networking (SDN)-based IPsec Flow Protection
             draft-ietf-i2nsf-sdn-ipsec-flow-protection-10

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: (i) gateway-to-gateway and (ii) host-to-
   host.  The service described in this document allows the
   configuration and monitoring of IPsec Security Associations (SAs)
   from a I2NSF Controller to one or several flow-based Network Security
   Functions (NSFs) that rely on IPsec to protect data traffic.

   The document focuses on the I2NSF NSF-facing interface by providing
   YANG data models for configuring the IPsec databases (SPD, SAD, PAD)
   and IKEv2.  This allows IPsec SA establishment with minimal
   intervention by the network administrator.  It does not define any
   new protocol.

Status of This Memo

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

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

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

   This Internet-Draft will expire on April 24, 2021.







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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   5
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  SDN-based IPsec management description  . . . . . . . . . . .   6
     4.1.  IKE case: IKEv2/IPsec in the NSF  . . . . . . . . . . . .   6
     4.2.  IKE-less case: IPsec (no IKEv2) in the NSF. . . . . . . .   7
   5.  IKE case vs IKE-less case . . . . . . . . . . . . . . . . . .   9
     5.1.  Rekeying process  . . . . . . . . . . . . . . . . . . . .  10
     5.2.  NSF state loss. . . . . . . . . . . . . . . . . . . . . .  11
     5.3.  NAT Traversal . . . . . . . . . . . . . . . . . . . . . .  11
     5.4.  NSF registration and discovery  . . . . . . . . . . . . .  12
   6.  YANG configuration data models  . . . . . . . . . . . . . . .  12
     6.1.  IKE case model  . . . . . . . . . . . . . . . . . . . . .  13
     6.2.  IKE-less case model . . . . . . . . . . . . . . . . . . .  17
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
     8.1.  IKE case  . . . . . . . . . . . . . . . . . . . . . . . .  23
     8.2.  IKE-less case . . . . . . . . . . . . . . . . . . . . . .  24
     8.3.  YANG modules  . . . . . . . . . . . . . . . . . . . . . .  24
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  26
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  26
     10.2.  Informative References . . . . . . . . . . . . . . . . .  29
   Appendix A.  Common YANG model for IKE and IKE-less cases . . . .  31
   Appendix B.  YANG model for IKE case  . . . . . . . . . . . . . .  46
   Appendix C.  YANG model for IKE-less case . . . . . . . . . . . .  65
   Appendix D.  XML configuration example for IKE case (gateway-to-
                gateway) . . . . . . . . . . . . . . . . . . . . . .  76
   Appendix E.  XML configuration example for IKE-less case (host-
                to-host) . . . . . . . . . . . . . . . . . . . . . .  80
   Appendix F.  XML notification examples  . . . . . . . . . . . . .  84



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   Appendix G.  Operational use cases examples . . . . . . . . . . .  86
     G.1.  Example of IPsec SA establishment . . . . . . . . . . . .  86
       G.1.1.  IKE case  . . . . . . . . . . . . . . . . . . . . . .  86
       G.1.2.  IKE-less case . . . . . . . . . . . . . . . . . . . .  88
     G.2.  Example of the rekeying process in IKE-less case  . . . .  90
     G.3.  Example of managing NSF state loss in IKE-less case . . .  91
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  91

1.  Introduction

   Software-Defined Networking (SDN) is an architecture that enables
   users 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 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 an SDN extension providing a software
   abstraction 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 in
   [RFC8192] describes another example use case for Cloud Data Center
   Scenario titled "Client-Specific Security Policy in Cloud VPNs".  The
   use case in RFC 8192 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 maybe 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 set of software interfaces and data models for controlling and
   monitoring aspects of physical and virtual Network Security
   Functions".  As defined in [RFC8192] an NSF is "a function that is



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   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, as Section 3.1.9 in [RFC8192] states "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 in the SDN
   paradigm, the I2NSF framework [RFC8329] defines a centralized entity,
   the I2NSF Controller, which manages one or multiple NSFs through a
   I2NSF NSF-Facing interface.  In this document we define a service
   allowing the I2NSF Controller to carry out the key management
   procedures.  More specifically, we define YANG data models for I2NSF
   NSF-Facing interface that allow the I2NSF Controller to configure and
   monitor IPsec-enabled flow-based NSFs.

   IPsec architecture [RFC4301] defines clear separation between the
   processing to provide security services to IP packets and the key
   management procedures to establish the IPsec Security Associations,
   which allows to centralize 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.
   Consideration for the host-to-gateway scenario is out of scope.

   For the definition of the YANG data model for 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, PAD (e.g.  IKE credential) and 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 into the NSF.  Therefore, the NSF will have only support for
       IPsec while key management functionality is moved to the I2NSF
       Controller.

   In both cases, a 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 modelling language



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   version 1.1 [RFC7950] and based on YANG models defined in
   [netconf-vpn], [I-D.tran-ipsecme-yang], RFC 4301 [RFC4301] and RFC
   7296 [RFC7296], this document defines the required interfaces with a
   YANG model for configuration and state data for IKE, PAD, SPD and SAD
   (see Appendix A, Appendix B and Appendix C).  The proposed YANG data
   model conforms to the Network Management Datastore Architecture
   (NMDA) defined in [RFC8342].  Examples of the usage of these models
   can be found in Appendix D, Appendix E and Appendix F.

   In summary, the objetives of this I-D are:

   o  To describe the architecture for the I2NSF-based IPsec management,
      which allows 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.

   o  To map this architecture to the I2NSF Framework.

   o  To define the interfaces required to manage and monitor the IPsec
      SAs in the NSF from a I2NSF Controller.  YANG data models are
      defined for configuration and state data for IPsec and IKEv2
      management through the I2NSF NSF-Facing interface.  Thus, this I-D
      does not define any new protocol.

2.  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 RFC
   2119 [RFC2119].  When these words appear in lower case, they have
   their natural language meaning.

3.  Terminology

   This document uses the terminology described in [RFC8329], [RFC8192],
   [RFC4301],[RFC7296], [RFC6241], [ITU-T.Y.3300].  The following term
   is defined in [ITU-T.Y.3300]:

   o  Software-Defined Networking.

   The following terms are in defined in [RFC8192]:

   o  NSF.

   o  Flow-based NSF.

   The following terms are defined in [RFC4301]:



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   o  Peer Authorization Database (PAD).

   o  Security Associations Database (SAD).

   o  Security Policy Database (SPD).

   The following term is defined in [RFC6437]:

   o  Flow/traffic flow.

   The following terms is defined in [RFC7296]:

   o  Internet Key Exchange version 2 (IKEv2).

   The following terms are defined in [RFC6241]:

   o  Configuration data.

   o  Configuration datastore.

   o  State date.

   o  Startup configuration datastore.

   o  Running configuration datastore.

4.  SDN-based IPsec management description

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

4.1.  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, deriving
   and delivering IKEv2 Credentials such as a pre-shared key,
   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 end points information (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



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   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 MUST be
   defined for the I2NSF NSF-Facing Interface.

4.2.  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.












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               +-----------------------------------------+
               |         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

   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.

   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.

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

   o  IV generation.

   o  Prevent counter resets for the same key.

   o  Generation of pseudo-random cryptographic keys for the IPsec SAs.

   o  Generation of the IPsec SAs when required based on notifications
      (i.e. sadb-acquire) from the NSF.

   o  Rekey of the IPsec SAs based on notifications from the NSF (i.e.
      expire).



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   o  NAT Traversal discovery and management.

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

   o  IPsec SA's SPI random generation.

   o  Cryptographic algorithm/s selection.

   o  Usage of extended sequence numbers.

   o  Establishment of proper traffic selectors.

5.  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
   downside, the NSF needs more resources to hold IKEv2 such as memory
   for the IKEv2 implementation, and computation, since each IPsec
   security association rekeying MAY involve a Diffie-Hellman exchange.

   Alternatively, 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 G.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 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 about
   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 I2SNF-based IPsec management, one
   way to reduce the latency and alleviate some performance issues can
   be the installation of the IPsec policies and IPsec SAs at the same
   time (proactive mode, as described in Appendix G.1) instead of
   waiting for notifications (e.g. a notification sadb-acquire when a



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   new IPsec SA is required) 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
   [I-D.carrel-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
   [I-D.carrel-ipsecme-controller-ike].

   In terms of security, IKE case provides better security properties
   than IKE-less case, as we discuss in section Section 8.  The main
   reason is that the NSFs generate the session keys and not the I2NSF
   Controller.

5.1.  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 and conduct the rekey
   process.  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 (if a IPsec SA lifetime has not been defined).  This
   rekeying process starts when the I2NSF Controller receives a sadb-
   expire notification or it decides so, 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 in
   Appendix G.2.







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5.2.  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 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 will configure the affected NSF
   with the new IKEv2, SPD and PAD information.  It has also to send new
   parameters (e.g. a new fresh PSK for authentication) to the NSFs
   which have IKEv2 SAs and IPsec SAs with the affected NSF.  Finally,
   the I2NSF Controller will instruct the affected NSF to start the
   IKEv2 negotiation with the new configuration.

   Alternatively, IKEv2 configuration MAY be made permanent between NSFs
   reboots without compromising security by means of the startup
   configuration datastore in the NSF.  This way, each time a NSF
   reboots it will use that configuration for each rebooting.  It would
   imply avoiding to contact with the I2NSF Controller.

   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 G.3.

5.3.  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.  If there is a
   NAT network configured between two peers, it is required to activate
   the usage of UDP or TCP/TLS encapsulation for ESP packets ([RFC3948],
   [RFC8229]).  Note that the usage of IPsec transport mode when NAT is
   required MUST NOT be used in this specification.





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   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 by
   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/TLS 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.

5.4.  NSF registration and discovery

   NSF registration refers to the process of facilitating 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 a 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 is the cryptographic suite
   supported, 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.

6.  YANG configuration data models

   In order to support the IKE and IKE-less cases we have modeled 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 models for the SPD and SAD.  We have defined
   three models: ietf-i2nsf-ikec (Appendix A, common to both cases),



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   ietf-i2nsf-ike (Appendix B, IKE case), ietf-i2nsf-ikeless
   (Appendix C, IKE-less case).  Since the model ietf-i2nsf-ikec has
   only typedef and groupings common to the other modules, we only show
   a simplified view of the ietf-i2nsf-ike and ietf-i2nsf-ikeless
   models.

6.1.  IKE case model

   The model related to IKEv2 has been extracted from reading 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 in [RFC4301] (NOTE: We have observed
   that many implementations integrate PAD configuration as part of the
   IKEv2 configuration).

   The data model for the IKE case is defined by YANG model "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?                  string
    |     |  +--:(gnx509)
    |     |  |  +--rw gnx509?                  string
    |     |  +--:(id-key)
    |     |  |  +--rw id-key?                  string
    |     |  +--:(id-null)
    |     |     +--rw id-null?                 empty
    |     +--rw auth-protocol?                 auth-protocol-type
    |     +--rw peer-authentication
    |        +--rw auth-method?         auth-method-type



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    |        +--rw eap-method
    |        |  +--rw eap-type    uint8
    |        +--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?        ct:x509
    |           +--rw private-key?            binary
    |           +--rw ca-data*                ct:x509
    |           +--rw crl-data?               ct:crl
    |           +--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?                   boolean
    | +--rw ike-sa-lifetime-soft
    | |  +--rw rekey-time?    uint32
    | |  +--rw reauth-time?   uint32
    | +--rw ike-sa-lifetime-hard
    | |  +--rw over-time?   uint32
    | +--rw authalg*             nsfikec:integrity-algorithm-type
    | +--rw encalg* [id]
    | |  +--rw id                uint8
    | |  +--rw algorithm-type?   nsfikec:encryption-algorithm-type
    | |  +--rw key-length?       uint16
    | +--rw dh-group?                            pfs-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



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    | |   +--rw anti-replay-window?   uint64
    | |   +--rw traffic-selector
    | |   |  +--rw local-subnet      inet:ip-prefix
    | |   |  +--rw remote-subnet     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-parameters
    | |   |  +--rw esp-algorithms
    | |   |  | +--rw integrity* integrity-algorithm-type
    | |   |  | +--rw encryption* [id]
    | |   |  | | +--rw id                uint8
    | |   |  | | +--rw algorithm-type? nsfikec:encryption-algorithm-type
    | |   |  | | +--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?   yang:hex-string
    | |   |      +--rw ecn?            boolean
    | |   +--rw spd-mark
    | |      +--rw mark?   uint32
    | |      +--rw mask?   yang:hex-string
    | +--rw child-sa-info
    | |  +--rw pfs-groups*               pfs-group
    | |  +--rw child-sa-lifetime-soft
    | |  |  +--rw time?      uint32
    | |  |  +--rw bytes?     uint32
    | |  |  +--rw packets?   uint32
    | |  |  +--rw idle?      uint32
    | |  |  +--rw action?    nsfikec:lifetime-action
    | |  +--rw child-sa-lifetime-hard
    | |     +--rw time?      uint32
    | |     +--rw bytes?     uint32



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    | |     +--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?               uint64
       +--ro half-open?           uint64
       +--ro half-open-cookies?   uint64


   The 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.  More precisely, it
   consists of a list of entries, each one indicating the identity,
   authentication method and credentials that will use a particular
   peer.

   Next, we find a list "conn-entry" 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.); list of IPsec policies describing the type of network traffic
   to be secured (local/remote subnet and ports, etc.) and how must be
   protected (AH/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.





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

6.2.  IKE-less case model

   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:

   o  Each IPsec policy (spd-entry) contains one traffic selector,
      instead of a list of them.  The reason is that we have observed
      actual kernel implementations only admit a single traffic selector
      per IPsec policy.

   o  Each IPsec policy contains a identifier (reqid) to relate the
      policy with the IPsec SA.  This is common in Linux-based systems.

   o  Each IPsec policy has only one name and not a list of names.

   o  Combined algorithms have been removed because encryption
      algorithms MAY include authenticated encryption with associated
      data (AEAD).

   o  Tunnel information has been extended with information about DSCP
      mapping and ECN bit.  The reason is that we have observed real
      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 in [RFC4301] though with some changes,
   namely:

   o  Each IPsec SA (sad-entry) contains one traffic selector, instead
      of a list of them.  The reason is that we have observed actual
      kernel implementations only admit a single traffic selector per
      IPsec SA.

   o  Each IPsec SA contains a identifier (reqid) to relate the IPsec SA
      with the IPsec Policy.  The reason is that we have observed real
      kernel implementations allow to include this value.

   o  Each IPsec SA has also a name in the same way as IPsec policies.

   o  Combined algorithm has been removed because encryption algorithm
      MAY include authenticated encryption with associated data (AEAD).

   o  Tunnel information has been extended with information about
      Differentiated Services Code Point (DSCP) mapping and Explicit



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      Congestion Notificsation (ECN) bit.  The reason is that we have
      observed actual kernel implementations admit the configurations of
      these values.

   o  Lifetime of the IPsec SAs also include idle time and number of IP
      packets as threshold to trigger the lifetime.  The reason is that
      we have observed actual kernel implementations allow to set these
      types of lifetimes.

   o  Information to configure the type of encapsulation (encapsulation-
      type) for IPsec ESP packets in UDP ([RFC3948]), TCP ([RFC8229]) or
      TLS ([RFC8229]) has been included.

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

   The data model for the IKE-less case is defined by YANG model "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?   uint64
    |     +--rw traffic-selector
    |     |  +--rw local-subnet      inet:ip-prefix
    |     |  +--rw remote-subnet     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



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    |     |   +--rw protocol-parameters? ipsec-protocol-parameters
    |     |   +--rw esp-algorithms
    |     |   | +--rw integrity* integrity-algorithm-type
    |     |   | +--rw encryption* [id]
    |     |   | |+--rw id                uint8
    |     |   | |+--rw algorithm-type? nsfikec:encryption-algorithm-type
    |     |   | |+--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?   yang:hex-string
    |     |      +--rw ecn?            boolean
    |     +--rw spd-mark
    |        +--rw mark?   uint32
    |        +--rw mask?   yang:hex-string
    +--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-number-counter?    uint64
      | +--rw seq-overflow?          boolean
      | +--rw anti-replay-window?    uint32
      | +--rw traffic-selector
      | |  +--rw local-subnet      inet:ip-prefix
      | |  +--rw remote-subnet     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-parameters
      | +--rw mode?                  nsfikec:ipsec-mode
      | +--rw esp-sa
      | | +--rw encryption
      | | |+--rw encryption-algorithm? nsfikec:encryption-algorithm-type
      | | |+--rw key?                  yang:hex-string
      | | |+--rw iv?                   yang:hex-string
      | | +--rw integrity
      | |  +--rw integrity-algorithm? nsfikec:integrity-algorithm-type
      | |  +--rw key?                   yang:hex-string



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      | +--rw sa-lifetime-hard
      | |  +--rw time?      uint32
      | |  +--rw bytes?     uint32
      | |  +--rw packets?   uint32
      | |  +--rw idle?      uint32
      | +--rw sa-lifetime-soft
      | |  +--rw time?      uint32
      | |  +--rw bytes?     uint32
      | |  +--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?   yang:hex-string
      | |  +--rw ecn?            boolean
      | +--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?     uint32
         |  +--ro packets?   uint32
         |  +--ro idle?      uint32
         +--ro replay-stats
            +--ro replay-window?        uint64
            +--ro packet-dropped?       uint64
            +--ro failed?               uint32
            +--ro seq-number-counter?   uint64

     notifications:
       +---n sadb-acquire {ikeless-notification}?
       |  +--ro ipsec-policy-name    string
       |  +--ro traffic-selector
       |     +--ro local-subnet      inet:ip-prefix
       |     +--ro remote-subnet     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



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       +---n sadb-expire {ikeless-notification}?
       |  +--ro ipsec-sa-name           string
       |  +--ro soft-lifetime-expire?   boolean
       |  +--ro lifetime-current
       |     +--ro time?      uint32
       |     +--ro bytes?     uint32
       |     +--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 data model consists of a unique "ipsec-ikeless" container which,
   in turn, is integrated by two additional containers: "spd" and "sad".
   The "spd" container consists of a list of entries that conform the
   Security Policy Database.  Compared to the IKE case 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 value to link an IPsec policy with its associated
   IPsec SAs.  The "sad" container is a list of entries that conform the
   Security Association Database.  In general, each entry allows to
   specify both configuration information (SPI, traffic selectors,
   tunnel/transport mode, cryptographic algorithms and keying material,
   soft/hard lifetimes, etc.) as well as state 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 inform I2NSF controller about relevant events such as IPsec SA
   expiration, sequence number overflow or bad SPI in a received packet.

   Appendix E shows an example of IKE-less case configuration for a NSF,
   in transport mode (host-to-host), with NSFs authentication based on
   shared secrets.  For the IKE-less case, Appendix F shows examples of
   IPsec SA expire, acquire, sequence number overflow and bad SPI
   notifications.

7.  IANA Considerations

   This document registers three URIs in the "ns" subregistry of the
   IETF XML Registry [RFC3688].  Following the format in [RFC3688], the
   following registrations are requested:






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       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.

   This document registers three YANG modules in the "YANG Module Names"
   registry [RFC6020].  Following the format in [RFC6020], the following
   registrations are requested:

       Name:       ietf-i2nsf-ikec
       Namespace:  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikec
       Prefix:     nsfikec
       Reference:  RFC XXXX

       Name:       ietf-i2nsf-ike
       Namespace:  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ike
       Prefix:     nsfike
       Reference:  RFC XXXX

       Name:       ietf-i2nsf-ikeless
       Namespace:  urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless
       Prefix:     nsfikels
       Reference:  RFC XXXX

8.  Security Considerations

   First of all, this document shares all the security issues of SDN
   that are specified in the "Security Considerations" section 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.

   On the other hand, if encryption is mandatory for all traffic of a
   NSF, its default policy MUST be to drop (DISCARD) packets to prevent
   cleartext packet leaks.  This default policy MUST be pre-configured
   in the startup configuration datastore in the NSF before the NSF
   contacts the I2NSF Controller.  Moreover, the startup configuration
   datastore MUST be also pre-configured with the required ALLOW



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   policies that allow the NSF to communicate with the I2NSF Controller
   once the NSF is deployed.  This pre-configuration 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, we have divided this section 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 [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.  Although we can assume this attack is not likely
   to happen due to the assumed security measurements to protect the
   I2NSF Controller, it still deserves some analysis in the hypothetical
   case that the attack occurs.  The impact is different depending on
   the IKE case or IKE-less case.

8.1.  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 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.

   o  IKEv2 configurations should adhere to the recommendations in
      [RFC8247].

   o  If PSK authentication is used in IKEv2, the I2NSF Controller MUST
      remove the PSK immediately after generating and distributing it.

   o  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,



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      the NSF could generate the private key and export only the public
      key to the I2NSF Controller.

   o  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.

8.2.  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.

8.3.  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):



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         /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 a NSF),
         the trust root (e.g. changing the trusted CA certificates), the
         cryptographic algorithms (allowing a downgrading attack), the
         IPsec policies (e.g. by allowing leaking of data traffic by
         changing to a 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 a allow policy) in the /ipsec-ikeless/
         spd container, and add/modify/delete any IPsec SAs between two
         NSF by means of /ipsec-ikeless/sad container and, in general
         changing any IPsec SAs and IPsec policies between any NSF.

   Some of the readable data nodes in this YANG module 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 should never 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 a ESP encryption key value and
         encryption/iv contains a initialization vector value.
         Similarly, integrity/key has 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.







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9.  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 Roman Danyliw for their valuable comments.

10.  References

10.1.  Normative References

   [I-D.draft-ietf-netconf-crypto-types]
              Watsen, K., "YANG Data Types and Groupings for
              Cryptography", draft-ietf-netconf-crypto-types-18 (work in
              progress), August 2020.

   [IKEv2-Parameters]
              Internet Assigned Numbers Authority (IANA), "Internet Key
              Exchange Version 2 (IKEv2) Parameters", August 2020.

   [ITU-T.X.690]
              "Recommendation ITU-T X.690", August 2015.

   [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>.

   [RFC2247]  Kille, S., Wahl, M., Grimstad, A., Huber, R., and S.
              Sataluri, "Using Domains in LDAP/X.500 Distinguished
              Names", RFC 2247, DOI 10.17487/RFC2247, January 1998,
              <https://www.rfc-editor.org/info/rfc2247>.

   [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>.

   [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>.




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   [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>.

   [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>.

   [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>.




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   [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>.

   [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>.




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10.2.  Informative References

   [I-D.carrel-ipsecme-controller-ike]
              Carrel, D. and B. Weiss, "IPsec Key Exchange using a
              Controller", draft-carrel-ipsecme-controller-ike-01 (work
              in progress), March 2019.

   [I-D.tran-ipsecme-yang]
              Tran, K., Wang, H., Nagaraj, V., and X. Chen, "Yang Data
              Model for Internet Protocol Security (IPsec)", draft-tran-
              ipsecme-yang-01 (work in progress), June 2015.

   [ITU-T.Y.3300]
              "Recommendation ITU-T Y.3300", June 2014.

   [libreswan]
              The Libreswan Project, "Libreswan VPN software", September
              2020.

   [netconf-vpn]
              Stefan Wallin, "Tutorial: NETCONF and YANG", January 2014.

   [ONF-OpenFlow]
              ONF, "OpenFlow Switch Specification (Version 1.4.0)",
              October 2013.

   [ONF-SDN-Architecture]
              "SDN Architecture", June 2014.

   [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>.

   [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>.

   [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>.




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   [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>.

   [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>.

   [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.

   [SDNSecurity]
              Kreutz, D., Ramos, F., and P. Verissimo, "Towards Secure
              and Dependable Software-Defined Networks", 2013.

   [strongswan]
              CESNET, "StrongSwan: the OpenSource IPsec-based VPN
              Solution", September 2020.









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Appendix A.  Common YANG model for IKE and IKE-less cases

   This Appendix is Normative.

   This YANG module has normative references to [RFC3947], [RFC4301],
   [RFC4303], [RFC8174], [RFC8221] and [IKEv2-Parameters].

   This YANG module has informative references to [RFC3948] and
   [RFC8229].



       <CODE BEGINS> file "ietf-i2nsf-ikec@2020-10-21.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";
           }

           import ietf-yang-types {
               prefix yang;
               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.



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               Copyright (c) 2020 IETF Trust and the persons
               identified as authors of the code.  All rights reserved.
               Redistribution and use in source and binary forms, with
               or without modification, is permitted pursuant to, and
               subject to the license terms contained in, the
               Simplified BSD License set forth in Section 4.c of the
               IETF Trust's Legal Provisions Relating to IETF Documents
               (https://trustee.ietf.org/license-info).

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

               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.";

           revision "2020-10-21" {
               description "Initial version.";
               reference "RFC XXXX: Software-Defined Networking
               (SDN)-based IPsec Flow Protection.";
           }

           typedef encryption-algorithm-type {
               type uint16;
               description
                   "The encryption algorithm is specified with a 16-bit
                   number extracted from IANA Registry. The acceptable
                   values MUST follow the requirement levels for
                   encryption algorithms for ESP and IKEv2.";
               reference
                    "IANA Registry- 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) and RFC 8247 -
                    Algorithm Implementation Requirements and Usage
                    Guidance for the Internet Key Exchange Protocol
                    Version 2 (IKEv2).";
           }

           typedef integrity-algorithm-type {
               type uint16;
               description
                   "The integrity algorithm is specified with a 16-bit
                   number extracted from IANA Registry.



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                   The acceptable values MUST follow the requirement
                   levels for encryption algorithms for ESP and IKEv2.";
               reference
                   "IANA Registry- 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) and 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
                   "Section 3.2 in RFC 4301.";
           }

           typedef esp-encap {
               type enumeration {
                   enum espintcp {
                       description
                           "ESP in TCP encapsulation.";
                       reference
                           "RFC 8229 - TCP Encapsulation of IKE and
                            IPsec Packets.";
                   }
                   enum espintls {
                       description
                           "ESP in TCP encapsulation using TLS.";
                       reference
                           "RFC 8229 - TCP Encapsulation of IKE and
                            IPsec Packets.";
                   }
                   enum espinudp {



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                       description
                           "ESP in UDP encapsulation.";
                       reference
                           "RFC 3948 - UDP Encapsulation of IPsec ESP
                           Packets.";
                   }
                   enum none {
                       description
                           "NOT ESP encapsulation.";
                   }
               }
               description
                   "Types of ESP encapsulation when Network Address
                    Translation (NAT) is present between two NSFs.";
               reference
                   "RFC 8229 - TCP Encapsulation of IKE and IPsec
                    Packets and RFC 3948 - UDP Encapsulation of IPsec
                    ESP Packets.";
           }

           typedef ipsec-protocol-parameters {
               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:



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                           rekey. ";
                   }
               }
               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 posible
                    options: terminate-clear, terminate-hold and
                    replace.";
               reference
                   "Section 4.5 in RFC 4301.";
           }

           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 a NSF
                    perspective inbound means the traffic that enters
                    the NSF and outbound is the traffic that is sent
                    from the NSF.";
               reference
                   "Section 5 in RFC 4301.";
           }

           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.";
                   }



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               }
               description
                   "The action when traffic matches an IPsec security
                    policy. According to RFC 4301 there are three
                    possible values: BYPASS, PROTECT AND DISCARD";
               reference
                   "Section 4.4.1 in RFC 4301.";
           }

           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. We
                    specify the IP protocol number with an uint8 or
                    ANY defining an enumerate with value 256 to
                    indicate the protocol number.";
               reference
                   "Section 4.4.1.1 in RFC 4301.
                    IANA Registry - Protocol Numbers.";
           }

           grouping encap {
               description
                   "This group of nodes allows to define the type of
                    encapsulation in case NAT traversal is
                    required and 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



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                       "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 and RFC 8229.";
           }

           grouping lifetime {
               description
                   "Different lifetime values limited to an IPsec SA.";
               leaf time {
                   type uint32;
                   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 uint32;
                   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



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                       infinite.";
               }
               leaf idle {
                   type uint32;
                   default 0;
                   description
                       "When a NSF stores an IPsec SA, it
                        consumes system resources. In an idle NSF 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
                   "Section 4.4.2.1 in RFC 4301.";

           }

           grouping port-range  {
               description
                   "This grouping defines a port range, such as
                    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;
                   description
                       "End port number. The assigned value must be
                        equal or greater than the start port number.
                        To express a single port, set the same value
                        as start and end.";
               }
               reference "Section 4.4.1.2 in RFC 4301.";
           }

           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 {



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                   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 DF (Don't Fragment) bit
                                from 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.";
                   reference
                       "Section 8.1 in RFC 4301.";
               }
               leaf bypass-dscp {
                   type boolean;
                   default true;
                   description
                       "If DSCP (Differentiated Services Code Point)
                        values in the inner header have to be used to
                        select one IPsec SA among several that match
                        the traffic selectors for an outbound packet";
                   reference
                       "Section 4.4.2.1. in RFC 4301.";



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               }
               leaf dscp-mapping {
                   type yang:hex-string;
                   default "00:00:00:00:00:00";
                   description
                       "DSCP values allowed for packets carried over
                        this IPsec SA.";
                   reference
                       "Section 4.4.2.1. in RFC 4301.";
               }
               leaf ecn {
                   type boolean;
                   default false;
                   description
                       "Explicit Congestion Notification (ECN). If true
                        copy CE bits to inner header.";
                   reference
                       "Section 5.1.2 and Annex C in RFC 4301.";
               }
           }

           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-subnet {
                   type inet:ip-prefix;
                   mandatory true;
                   description
                       "Local IP address subnet.";
               }
               leaf remote-subnet {
                   type inet:ip-prefix;
                   mandatory true;
                   description
                       "Remote IP address subnet.";
               }
               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";



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                   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
                   "Section 4.4.1.2 in RFC 4301.";
           }

           grouping ipsec-policy-grouping {
               description
                   "Holds configuration information for an IPsec SPD
                    entry.";

               leaf anti-replay-window {
                   type uint64;
                   default 32;
                   description
                       "A 64-bit counter used to determine whether an
                        inbound ESP packet is a replay.";
                   reference
                       "Section 4.4.2.1 in RFC 4301.";
               }
               container traffic-selector {
                   description
                       "Packets are selected for
                        processing actions based on the IP and inner
                        protocol header information, selectors,
                        matched against entries in the SPD.";
                   uses selector-grouping;
                   reference
                       "Section 4.4.4.1 in RFC 4301.";
               }
               container processing-info {



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                   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. True 64 bit counter,
                                 False 32 bit.";
                       }
                       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



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                               be rekeyed, or whether rollover is
                               permitted (true). If Authenticated
                               Encryption with Associated Data
                               (AEAD) is used this flag MUST be
                               false.";
                       }
                       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-parameters;
                           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 integrity-algorithm-type;
                               default 0;
                               ordered-by user;
                               description
                                   "Configuration of ESP authentication
                                   based on the specified integrity
                                   algorithm. With AEAD algorithms,
                                   the integrity node is not
                                   used.";
                               reference
                                   "Section 3.2 in RFC 4303.";



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                           }
                           list encryption {
                               key id;
                               ordered-by user;
                               leaf id {
                                   type uint8;
                                   description
                                    "The index of list with the
                                    different encryption algorithms and
                                    its key-length (if required).";
                               }
                               leaf algorithm-type {
                                type nsfikec:encryption-algorithm-type;
                                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
                                   "Section 3.2 in RFC 4303.";
                           }

                           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
                                   "Section 2.7 in RFC 4303.";
                           }



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                           reference
                               "RFC 4303.";
                       }
                       container tunnel {
                           when "../mode = 'tunnel'";
                           uses tunnel-grouping;
                           description
                              "IPsec tunnel endpoints definition.";
                       }
                   }
                   reference
                       "Section 4.4.1.2 in RFC 4301.";
               }
               container spd-mark {
                       description
                           "The Mark to set for the IPsec SA of this
                            connection. This option is only available
                            on linux NETKEY/XFRM kernels. It can be
                            used with iptables to create custom
                            iptables rules using CONNMARK. It can also
                            be used with Virtual Tunnel Interfaces
                            (VTI) to direct marked traffic to
                            specific vtiXX devices.";
                       leaf mark {
                           type uint32;
                           default 0;
                           description
                               "Mark used to match XFRM policies and
                                states.";
                       }
                       leaf mask {
                           type yang:hex-string;
                           default 00:00:00:00;
                           description
                               "Mask used to match XFRM policies and
                               states.";
                       }
               }
           }
       }

       <CODE ENDS>









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Appendix B.  YANG model for IKE case

   This Appendix is Normative.

   This YANG module has normative references to [RFC2247], [RFC5280],
   [RFC4301], [RFC5280], [RFC5915], [RFC6991], [RFC7296], [RFC7383],
   [RFC7427], [RFC7619], [RFC8017], [RFC8174], [RFC8341], [ITU-T.X.690],
   [I-D.draft-ietf-netconf-crypto-types] and [IKEv2-Parameters].

   This YANG module has informative references to [RFC8229].



       <CODE BEGINS> file "ietf-i2nsf-ike@2020-10-21.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-crypto-types {
               prefix ct;
               reference "RFC XXXX: YANG Data Types and Groupings
                          for Cryptography.";
           }

           import ietf-i2nsf-ikec {
               prefix nsfikec;
               reference
                   "Common Data model for SDN-based IPsec
                    configuration.";
           }

           import ietf-netconf-acm {
               prefix nacm;
               reference
                    "RFC 8341: Network Configuration Access Control
                     Model.";



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           }

           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 IPsec IKE case model for the SDN-based
            IPsec flow protection service. An NSF will implement this
            module.

           Copyright (c) 2020 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 XXXX; see
           the RFC itself for full legal notices.

           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.";

           revision "2020-10-21" {
               description "Initial version.";
               reference "RFC XXXX: Software-Defined Networking
               (SDN)-based IPsec Flow Protection.";



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           }

           typedef ike-spi {
               type uint64 { range "0..max"; }
               description
                   "Security Parameter Index (SPI)'s IKE SA.";
               reference
                   "Section 2.6 in RFC 7296.";
           }

           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's kernel but the
                           IPsec SAs are not established immediately.
                           The IKE implementation will negotiate the
                           IPsec SAs when the NSF's kernel requests it
                           (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 any packet.";
                   }
               }
               description
                   "Different policies to set IPsec SA configuration
                    into NSF's kernel when IKEv2 implementation has
                    started.";
           }

           typedef pfs-group {
               type uint16;
               description
                   "DH groups for IKE and IPsec SA rekey.";
               reference
                   "Section 3.3.2 in RFC 7296. Transform Type 4 -
                    Diffie-Hellman Group Transform IDs in IANA Registry



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                     - Internet Key Exchange Version 2 (IKEv2)
                    Parameters.";
           }

           typedef auth-protocol-type {
               type enumeration {
                   enum ikev2 {
                       value 2;
                       description
                           "IKEv2 authentication protocol. It is the
                            only 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
                    enumerate to allow new IKE versions in the
                    future.";
               reference
                   "RFC 7296.";
           }

           typedef auth-method-type {
               type enumeration {
                   enum pre-shared {
                       description
                           "Select pre-shared key as the
                           authentication method.";
                       reference
                           "RFC 7296.";
                   }
                   enum eap {
                       description
                           "Select EAP as the authentication method.";
                       reference
                           "RFC 7296.";
                   }
                   enum digital-signature {
                       description
                           "Select digital signature method.";
                       reference
                           "RFC 7296 and RFC 7427.";
                   }
                   enum null {
                       description
                           "Null authentication.";
                       reference



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                           "RFC 7619.";
                   }

               }
               description
                   "Peer authentication method specified in the Peer
                    Authorization Database (PAD).";
           }

           container ipsec-ike {
               description
                   "IKE configuration for a NSF. It includes PAD
                    parameters, IKE connections information and state
                    data.";

               container pad {
                   description
                      "Configuration of Peer Authorization Database
                       (PAD). The PAD contains information about IKE
                       peer (local and remote). Therefore, the Security
                       Controller also stores authentication
                       information for this NSF and can include
                       several entries for the local NSF not only
                       remote peers. Storing local and remote
                       information makes possible to specify that this
                       NSF with identity A will use some particular
                       authentication with remote NSF with identity B
                       and what are the authentication mechanisms
                       allowed to B.";
                   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.";
                       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



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                               peer (this NSF).";
                           reference
                               "Section 4.4.3.1 in RFC 4301.";
                           case ipv4-address{
                               leaf ipv4-address {
                                   type inet:ipv4-address;
                                   description
                                       "Specifies the identity as a
                                        single four (4) octet.";
                               }
                           }
                           case ipv6-address{
                               leaf ipv6-address {
                                   type inet:ipv6-address;
                                   description
                                       "Specifies the identity as a
                                        single sixteen (16) octet IPv6
                                        address. An example is
                                        2001:DB8:0:0:8:800:200C:417A.";
                               }
                           }
                           case fqdn-string {
                               leaf fqdn-string {
                                   type inet:domain-name;
                                   description
                                       "Specifies the identity as a
                                        Fully-QualifiedDomain Name
                                        (FQDN) string. An example is:
                                        example.com. The string MUST
                                        NOT contain any terminators
                                        (e.g., NULL, CR, etc.).";
                               }
                           }
                           case rfc822-address-string {
                               leaf rfc822-address-string {
                                   type string;
                                   description
                                       "Specifies the identity as a
                                        fully-qualified RFC822 email
                                        address string. An example is,
                                        jsmith@example.com. The string
                                        MUST NOT contain any
                                        terminators e.g., NULL, CR,
                                        etc.).";
                                   reference
                                       "RFC 822.";
                               }
                           }



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                           case dnx509 {
                               leaf dnx509 {
                                   type string;
                                   description
                                       "Specifies the identity as a
                                        ASN.1 X.500 Distinguished
                                        Name. An example is
                                        C=US,O=Example
                                        Organisation,CN=John Smith.";
                                   reference
                                       "RFC 2247.";
                               }
                           }
                           case gnx509 {
                               leaf gnx509 {
                                   type string;
                                   description
                                       "ASN.1 X.509 GeneralName. RFC
                                        5280.";
                               }
                           }
                           case id-key {
                               leaf id-key {
                                   type string;
                                   description
                                       "Opaque octet stream that may be
                                        used to pass vendor-specific
                                        information for proprietary
                                        types of identification.";
                                   reference
                                       "Section 3.5 in RFC 7296.";
                               }
                           }
                           case id-null {
                               leaf id-null {
                                   type empty;
                                   description
                                       "ID_NULL identification used
                                        when IKE identification payload
                                        is not used." ;
                                   reference
                                       "RFC 7619.";
                               }
                           }
                       }
                       leaf auth-protocol {
                           type auth-protocol-type;
                           default ikev2;



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                           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, digitial-signature, null) that
                                will use a particular peer and the
                                credentials, 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, eap, digital signature,
                                    null).";
                              reference
                                  "Section 2.15 in RFC 7296.";
                           }
                           container eap-method {
                               when "../auth-method = 'eap'";
                               leaf eap-type {
                                   type uint8;
                                   mandatory true;
                                   description
                                       "EAP method type. 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
                                   "Section 2.16 in RFC 7296.";
                           }
                           container pre-shared {
                               when
                                   "../auth-method[.='pre-shared' or
                                    .='eap']";
                               leaf secret {



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                                   nacm:default-deny-all;
                                   type yang:hex-string;
                                   mandatory true;
                                   description
                                       "Pre-shared secret value. The
                                        NSF has to prevent read access
                                        to this value for security
                                        reasons.";
                               }
                               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 1;
                                   description
                                       "The digital signature
                                       algorithm is specified with a
                                       value extracted from the IANA
                                       Registry. Depending on the
                                       algorithm, the following leafs
                                       must contain information. For
                                       example if digital signature
                                       involves a certificate then leaf
                                       'cert-data' and 'private-key'
                                       will contain this information.";
                                   reference
                                       "IKEv2 Authentication Method -
                                        IANA Registry - Internet Key
                                        Exchange Version 2 (IKEv2)
                                        Parameters.";
                               }

                               choice public-key {
                                   mandatory true;
                                   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



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                                         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 XXXX: YANG Data Types and
                                         Groupings for Cryptography.";
                                   }

                                   leaf cert-data {
                                       type ct:x509;
                                       description
                                           "X.509 certificate data -
                                            PEM4. If raw-public-key
                                            is defined this leaf is
                                            empty.";
                                       reference
                                         "RFC XXXX: YANG Data Types and
                                         Groupings for Cryptography.";
                                   }

                                   description
                                       "If the I2NSF Controller
                                        knows that the NSF
                                        already owns a private key
                                        associated to this public key
                                        (the NSF generated the pair
                                        public key/private key out of
                                        band), it will only configure
                                        one of the leaf 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



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                                        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
                                        I2NSF controller is in charge
                                        of configuring the
                                        private-key. Otherwise, it is
                                        not set and the value is
                                        kept in secret.";
                                   reference
                                        "RFC XXXX: YANG Data Types and
                                         Groupings for Cryptography.";
                               }
                               leaf-list ca-data {
                                   type ct:x509;
                                   description
                                       "List of trusted Certification
                                       Authorities (CA) certificates
                                       encoded using ASN.1
                                       distinguished encoding rules
                                       (DER). If it is not defined
                                       the default value is empty.";
                                   reference
                                         "RFC XXXX: YANG Data Types and
                                         Groupings for Cryptography.";
                               }
                               leaf crl-data {
                                   type ct:crl;
                                   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 XXXX: YANG Data Types and
                                         Groupings for Cryptography.";
                               }
                               leaf crl-uri  {
                                   type inet:uri;
                                   description
                                       "X.509 CRL certificate URI.



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                                       If it is not defined
                                       the default value is empty.";
                               }
                               leaf oscp-uri {
                                   type inet:uri;
                                   description
                                       "OCSP URI.
                                       If it is not defined
                                       the default value is empty.";
                               }
                               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 be translated in
                       real time by 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 to false it
                           means the usage of the INITIAL_CONTACT



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                           notification will depend on the IKEv2
                           implementation.";
                   }
                   leaf version {
                       type auth-protocol-type;
                       default ikev2;
                       description
                          "IKE version. Only version 2 is supported
                          so far.";
                   }
                   leaf fragmentation {
                       type boolean;
                       default false;
                       description
                           "Whether or not to enable IKE
                            fragmentation as per RFC 7383 (true or
                            false).";
                       reference
                           "RFC 7383.";
                   }
                   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 a IKE SA reauthentication starts.";
                      leaf rekey-time {
                           type uint32;
                           default 0;
                           description
                               "Time in seconds between each IKE SA
                               rekey.The value 0 means infinite.";
                      }
                      leaf reauth-time {
                           type uint32;
                           default 0;
                           description
                             "Time in seconds between each IKE SA
                             reauthentication. The value 0 means
                             infinite.";
                      }
                      reference
                          "Section 2.8 in RFC 7296.";
                   }
                   container ike-sa-lifetime-hard {
                       description



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                           "Hard IKE SA lifetime. When this
                            time is reached the IKE SA is removed.";
                       leaf over-time {
                           type uint32;
                           default 0;
                           description
                               "Time in seconds before the IKE SA is
                                removed. The value 0 means infinite.";
                       }
                       reference
                           "RFC 7296.";
                   }
                   leaf-list authalg {
                       type nsfikec:integrity-algorithm-type;
                       default 12;
                       ordered-by user;
                       description
                          "Authentication algorithm for establishing
                          the IKE SA. This list is ordered following
                          from the higher priority to lower priority.
                          First node of the list will be the algorithm
                          with higher priority.";
                   }

                   list encalg {
                       key id;
                       min-elements 1;
                       ordered-by user;
                       leaf id {
                           type uint8;
                           description
                               "The index of the list with the
                               different encryption algorithms and its
                               key-length (if required). E.g. AES-CBC,
                               128 bits";
                       }
                       leaf algorithm-type {
                           type nsfikec:encryption-algorithm-type;
                           default 12;
                           description
                               "Default value 12 (ENCR_AES_CBC)";
                       }
                       leaf key-length {
                           type uint16;
                           default 128;
                           description
                               "By default key length is 128 bits";
                       }



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                       description
                          "Encryption or AEAD algorithm for the IKE
                          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.";
                   }
                   leaf dh-group {
                       type pfs-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;
                       default 0;
                       description
                           "Set the half-open IKE SA timeout
                            duration.";
                       reference
                           "Section 2 in RFC 7296.";
                   }

                   leaf half-open-ike-sa-cookie-threshold {
                       type uint32;
                       default 0;
                       description
                           "Number of half-open IKE SAs that activate
                            the cookie mechanism." ;
                       reference
                           "Section 2.6 in RFC 7296.";
                   }
                   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.";



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                   }
                   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 use 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.";
                   }
                   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 {



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                               description
                                   "This container carries the
                                   configuration of a IPsec policy.";
                               uses nsfikec:ipsec-policy-grouping;
                           }
                           description
                               "List of entries which will constitute
                               the representation of the SPD. Since we
                               have IKE in this case, it is only
                               required to send a 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
                           "Section 2.9 in RFC 7296.";
                   }
                   container child-sa-info {
                       leaf-list pfs-groups {
                           type pfs-group;
                           default 0;
                           ordered-by user;
                           description
                               "If non-zero, it is required perfect
                                forward secrecy when requesting new
                                IPsec SA. The non-zero value is
                                the required group number. This list is
                                ordered following from the higher
                                priority to lower priority. First node
                                of the list will be the algorithm
                                with higher priority.";
                       }
                       container child-sa-lifetime-soft {
                           description
                               "Soft IPsec SA lifetime soft.
                                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



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                                    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
                               "Section 4.5 in RFC 4301 and Section 2.8
                                in RFC 7296.";
                           }
                       }
                       container child-sa-lifetime-hard {
                           description
                               "IPsec SA lifetime hard. The action will
                                be to terminate the IPsec SA.";
                           uses nsfikec:lifetime;
                           reference
                               "Section 2.8 in RFC 7296.";
                       }
                       description
                           "Specific information for IPsec SAs
                           SAs. It includes PFS group and IPsec SAs
                           rekey lifetimes.";
                   }
                   container state {
                       config false;

                       leaf initiator {
                           type boolean;
                           description
                               "It is acting as 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.";



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                       }
                       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.";
                       }
                       leaf established {
                           type uint64;
                           description
                               "Seconds since this IKE SA has been
                                established.";
                       }
                       leaf current-rekey-time {
                           type uint64;
                           description
                               "Seconds before IKE SA must be rekeyed.";
                       }
                       leaf current-reauth-time {
                           type uint64;
                           description
                               "Seconds before IKE SA must be
                                re-authenticated.";
                       }
                       description
                           "IKE state data for a particular
                            connection.";
                   } /* ike-sa-state */
               } /* ike-conn-entries */

               container number-ike-sas {
                   config false;
                   leaf total {
                       type uint64;
                       description



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                           "Total number of active IKE SAs.";
                   }
                   leaf half-open {
                       type uint64;
                       description
                           "Number of half-open active IKE SAs.";
                   }
                   leaf half-open-cookies {
                       type uint64;
                       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>



Appendix C.  YANG model for IKE-less case

   This Appendix is Normative.

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



       <CODE BEGINS> file "ietf-i2nsf-ikeless@2020-10-21.yang"

       module ietf-i2nsf-ikeless {

           yang-version 1.1;
           namespace "urn:ietf:params:xml:ns:yang:ietf-i2nsf-ikeless";

           prefix "nsfikels";

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




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           import ietf-i2nsf-ikec {
               prefix nsfikec;
               reference
                   "Common Data model for SDN-based IPsec
                    configuration.";
           }

           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-base IPsec flow
                protection service.

                Copyright (c) 2020 IETF Trust and the persons
                identified as authors of the code.  All rights reserved.
                Redistribution and use in source and binary forms, with
                or without modification, is permitted pursuant to, and
                subject to the license terms contained in, the
                Simplified BSD License set forth in Section 4.c of the
                IETF Trust's Legal Provisions Relating to IETF Documents
                (https://trustee.ietf.org/license-info).

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

                The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
                'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',



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                '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.";

           revision "2020-10-21" {
               description "Initial version.";
               reference "RFC XXXX: Software-Defined Networking
               (SDN)-based IPsec Flow Protection.";
           }

           feature ikeless-notification {
               description
                   "To ensure broader applicability of this module,
                   the notifications are marked as a feature.
                   For the implementation of ikeless 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 to configure IPsec Security Associations
                    (IPsec SAs) in the Security Association Database
                    (SAD).";
               reference "RFC 4301.";
               container spd {
                   description
                       "Configuration of the Security Policy Database
                        (SPD.)";
                   reference "Section 4.4.1.2 in RFC 4301.";

                   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;



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                           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
                                IPsec policy will require.";
                       }
                       leaf reqid {
                           type uint64;
                           default 0;
                           description
                               "This value allows to link 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 a 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 "Section 4.4.2.1 in RFC 4301.";
                   list sad-entry {
                       key "name";
                       ordered-by user;
                       leaf name {
                           type string;
                           description



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                               "SAD entry unique name to identify this
                                entry.";
                       }
                       leaf reqid {
                           type uint64;
                           default 0;
                           description
                               "This value allows to link 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
                                   "Security Parameter Index (SPI)'s
                                    IPsec SA.";
                           }
                           leaf ext-seq-num {
                               type boolean;
                               default true;
                               description
                                   "True if this IPsec SA is using
                                    extended sequence numbers. True 64
                                    bit counter, FALSE 32 bit.";
                           }
                           leaf seq-number-counter {
                               type uint64;
                               default 0;
                               description
                                    "A 64-bit counter when this IPsec
                                    SA is using Extended Sequence
                                    Number or 32-bit counter when it
                                    is not. It used to generate the
                                    initial Sequence Number field
                                    in ESP headers.";
                           }
                           leaf seq-overflow {
                               type boolean;
                               default false;
                               description
                                   "The flag indicating whether
                                    overflow of the sequence number



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                                    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 this flag MUST BE
                                    false.";
                           }
                           leaf anti-replay-window {
                               type uint32;
                               default 32;
                               description
                                   "A 32-bit counter and a bit-map (or
                                    equivalent) used to determine
                                    whether an inbound ESP packet is a
                                    replay. If set to 0 no anti-replay
                                    mechanism is performed.";
                           }
                           container traffic-selector {
                               uses nsfikec:selector-grouping;
                               description
                                   "The IPsec SA traffic selector.";
                           }
                           leaf protocol-parameters {
                               type nsfikec:ipsec-protocol-parameters;
                               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
                                    Encapsulation Security Payload
                                    (ESP), it is required to specify
                                    encryption and integrity
                                    algorithms, and key material.";

                             container encryption {



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                               description
                                       "Configuration of encryption or
                                        AEAD algorithm for IPsec
                                        Encapsulation Security Payload
                                        (ESP).";

                               leaf encryption-algorithm {
                                type nsfikec:encryption-algorithm-type;
                                default 12;
                                description
                                           "Configuration of ESP
                                            encryption. With AEAD
                                            algorithms, the integrity
                                            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 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 to configure integrity
                                        algorithm when no AEAD



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                                        algorithms are used, and
                                        integrity is required.";
                               leaf integrity-algorithm {
                                  type nsfikec:integrity-algorithm-type;
                                  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.";



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                               }
                           }
                           container tunnel {
                               when "../mode = 'tunnel'";
                               uses nsfikec:tunnel-grouping;
                               description
                                    "Endpoints of the IPsec tunnel.";
                           }
                           container encapsulation-type
                           {
                               uses nsfikec:encap;
                               description
                                   "This container carries
                                    configuration information about
                                    the source and destination ports
                                    which will be used for ESP
                                    encapsulation that ESP packets 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.";
                               leaf replay-window {
                                   type uint64;
                                   description
                                       "Current state of the replay
                                        window.";
                               }
                               leaf packet-dropped {
                                   type uint64;
                                   description
                                       "Packets detected out of the
                                        replay window and dropped
                                        because they are replay



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                                        packets.";
                               }
                               leaf failed {
                                   type uint32;
                                   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 conforms the SAD.";
                   } /*list sad-entry*/
               } /*container sad*/
           }/*container ipsec-ikeless*/

           /* Notifications */
           notification sadb-acquire {
               if-feature ikeless-notification;
               description
                   "An IPsec SA is required. The traffic-selector
                    container contains information about the IP packet
                    that triggers the acquire 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.";



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               }
               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 has expired.  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 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.";
                   uses nsfikec:lifetime;
               }
           }
           notification sadb-seq-overflow {



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               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 sequence
                        number overflow and rollover is not permitted.
                        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 the it can
                        know all the information (crypto algorithms,
                        etc.) about the IPsec SA that has expired 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>



Appendix D.  XML configuration example for IKE case (gateway-to-gateway)

   This example shows a XML configuration file sent by the I2NSF
   Controller to establish a IPsec Security Association between two NSFs
   (see Figure 3) in tunnel mode (gateway-to-gateway) with ESP,
   authentication based on X.509 certificates and applying the IKE case.








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                              +------------------+
                              | 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>



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     </pad>
     <conn-entry>
        <name>nsf_h1-nsf_h2</name>
        <autostartup>start</autostartup>
        <version>ikev2</version>
        <initial-contact>false</initial-contact>
        <fragmentation>true</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_SHA1_160-->
        <authalg>7</authalg>
        <!--ENCR_AES_CBC - 128 bits-->
        <encalg>
           <id>1</id>
        </encalg>
        <!--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>32</anti-replay-window>
               <traffic-selector>
                  <local-subnet>2001:DB8:1::0/64</local-subnet>
                  <remote-subnet>2001:DB8:2::0/64</remote-subnet>
                  <inner-protocol>any</inner-protocol>
                  <local-ports>
                    <start>0</start>
                    <end>0</end>
                  </local-ports>
                  <remote-ports>
                    <start>0</start>
                    <end>0</end>



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                  </remote-ports>
               </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>
                        <ecn>false</ecn>
                    </tunnel>
                  </ipsec-sa-cfg>
               </processing-info>
             </ipsec-policy-config>
          </spd-entry>
        </spd>
        <child-sa-info>
           <!--8192-bit MODP Group -->
           <pfs-groups>18</pfs-groups>
           <child-sa-lifetime-soft>
              <bytes>1000000</bytes>
              <packets>1000</packets>
              <time>30</time>
              <idle>60</idle>
              <action>replace</action>



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           </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 E.  XML configuration example for IKE-less case (host-to-host)

   This example shows a XML configuration file sent by the I2NSF
   Controller to establish a IPsec Security Association between two NSFs
   (see Figure 4) in transport mode (host-to-host) with ESP, and
   applying 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>



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           <ipsec-policy-config>
              <traffic-selector>
                <local-subnet>2001:DB8:123::200/128</local-subnet>
                <remote-subnet>2001:DB8:123::100/128</remote-subnet>
                <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>
              <processing-info>
                 <action>protect</action>
                 <ipsec-sa-cfg>
                   <ext-seq-num>true</ext-seq-num>
                   <seq-overflow>true</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-subnet>2001:DB8:123::100/128</local-subnet>
                 <remote-subnet>2001:DB8:123::200/128</remote-subnet>
                 <inner-protocol>any</inner-protocol>



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                 <local-ports>
                   <start>0</start>
                   <end>0</end>
                 </local-ports>
                 <remote-ports>
                   <start>0</start>
                   <end>0</end>
                 </remote-ports>
               </traffic-selector>
               <processing-info>
                 <action>protect</action>
                 <ipsec-sa-cfg>
                   <ext-seq-num>true</ext-seq-num>
                   <seq-overflow>true</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-number-counter>100</seq-number-counter>
               <seq-overflow>true</seq-overflow>
               <anti-replay-window>32</anti-replay-window>
               <traffic-selector>
                 <local-subnet>2001:DB8:123::100/128</local-subnet>
                 <remote-subnet>2001:DB8:123::200/128</remote-subnet>



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                    <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>
                <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-number-counter>100</seq-number-counter>
                 <seq-overflow>true</seq-overflow>
                 <anti-replay-window>32</anti-replay-window>
                 <traffic-selector>
                    <local-subnet>2001:DB8:123::200/128</local-subnet>
                    <remote-subnet>2001:DB8:123::100/128</remote-subnet>
                    <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>



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                 </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 F.  XML notification examples

   Below we show several XML files that represent different types of
   notifications defined in the IKE-less YANG model, which are sent by
   the NSF to the I2NSF Controller.  The notifications happen in the
   IKE-less case.










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   <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 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-subnet>2001:DB8:123::200/128</local-subnet>
           <remote-subnet>2001:DB8:123::100/128</remote-subnet>
           <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 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 sadb-seq-overflow notification.





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


              Figure 8: Example of sadb-bad-spi notification.

Appendix G.  Operational use cases examples

G.1.  Example of IPsec SA establishment

   This appendix exemplifies the applicability of IKE case and IKE-less
   case to traditional IPsec configurations, that is, host-to-host and
   gateway-to-gateway.  The examples we show in the following 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 SaaS cloud services.  Besides, 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 we will show in the following, the I2NSF-based IPsec management
   system (for IKE and IKE-less cases), exhibits various advantages:

   1.  It allows to create 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.

G.1.1.  IKE case







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                 +----------------------------------------+
                 |  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 the 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.




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   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.

G.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 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 the 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 (SPD and SAD).  The following text describes
       how this would happen:



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       *  The I2NSF Controller chooses two random values as SPIs: for
          example, SPIa1 for NSF A and SPIb1 for NSF B.  These numbers
          MUST NOT be in conflict with any IPsec SA in NSF A or NSF B.
          It also generates fresh cryptographic material for the new
          inbound/outbound IPsec SAs and their parameters.

       *  After that, the I2NSF Controller sends simultaneously 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.

       Other alternative to this operation is: the I2NSF Controller
       sends first the IPsec policies and new inbound IPsec SAs to A and
       B and once it obtains a successful confirmation of these
       operations from NSF A and NSF B, it proceeds with installing to
       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. the 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 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 saw first the data packet will send a sadb-



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   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.

G.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, let assume that SPIa1 identifies the inbound IPsec SA in A,
   and SPIb1 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 A and SPIb2 for B.
       These numbers MUST NOT be in conflict with any IPsec SA in A or
       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. the 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 fails
   (e.g. the 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.

   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



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   step 1 and step 2 since new and valid IPsec SAs were created and are
   functional.  The I2NSF Controller may reattempt to remove the old
   inbound and outbound 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.

G.3.  Example of managing NSF state loss in IKE-less case

   In the IKE-less case, if the I2NSF Controller detects that a 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.

   Step 2 and step 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 I2NSF Controller
   and NSFs is lower.

Authors' Addresses

   Rafa Marin-Lopez
   University of Murcia
   Campus de Espinardo S/N, Faculty of Computer Science
   Murcia  30100
   Spain

   Phone: +34 868 88 85 01
   EMail: rafa@um.es


   Gabriel Lopez-Millan
   University of Murcia
   Campus de Espinardo S/N, Faculty of Computer Science
   Murcia  30100
   Spain

   Phone: +34 868 88 85 04
   EMail: gabilm@um.es



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   Fernando Pereniguez-Garcia
   University Defense Center
   Spanish Air Force Academy, MDE-UPCT
   San Javier (Murcia)  30720
   Spain

   Phone: +34 968 18 99 46
   EMail: fernando.pereniguez@cud.upct.es











































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