Imported debug from /usr/lib/site-python/debug.pyc draft-ietf-i2nsf-sdn-ipsec-flow-protection-04 - Software-Defined Networking (SDN)-based IPsec Flow Protection
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Versions: (draft-abad-i2nsf-sdn-ipsec-flow-protection) 00 01 02 03 04

I2NSF                                                     R. Marin-Lopez
Internet-Draft                                           G. Lopez-Millan
Intended status: Standards Track                    University of Murcia
Expires: September 12, 2019                         F. Pereniguez-Garcia
                                               University Defense Center
                                                          March 11, 2019


     Software-Defined Networking (SDN)-based IPsec Flow Protection
             draft-ietf-i2nsf-sdn-ipsec-flow-protection-04

Abstract

   This document describes how providing IPsec-based flow protection by
   means of a Software-Defined Network (SDN) controller (aka.  Security
   Controller) and establishes the requirements to support this service.
   It considers two main well-known scenarios in IPsec: (i) gateway-to-
   gateway and (ii) host-to-host.  The SDN-based service described in
   this document allows the distribution and monitoring of IPsec
   information from a Security Controller to one or several flow-based
   Network Security Function (NSF).  The NSFs implement IPsec to protect
   data traffic between network resources with IPsec.

   The document focuses in the NSF Facing Interface by providing models
   for Configuration and State data model required to allow the Security
   Controller to configure the IPsec databases (SPD, SAD, PAD) and IKEv2
   to establish security associations with a reduced intervention of the
   network administrator.

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 September 12, 2019.






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Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  SDN-based IPsec management description  . . . . . . . . . . .   6
     5.1.  IKE case: IKE/IPsec in the NSF  . . . . . . . . . . . . .   6
       5.1.1.  Interface Requirements for IKE case . . . . . . . . .   7
     5.2.  IKE-less case: IPsec (no IKEv2) in the NSF  . . . . . . .   8
       5.2.1.  Interface Requirements for IKE-less case  . . . . . .   8
     5.3.  IKE case vs IKE-less case . . . . . . . . . . . . . . . .   9
       5.3.1.  Rekeying process  . . . . . . . . . . . . . . . . . .  10
       5.3.2.  NSF state loss  . . . . . . . . . . . . . . . . . . .  11
       5.3.3.  NAT Traversal . . . . . . . . . . . . . . . . . . . .  12
   6.  YANG configuration data models  . . . . . . . . . . . . . . .  12
     6.1.  IKE case model  . . . . . . . . . . . . . . . . . . . . .  13
     6.2.  IKE-less case model . . . . . . . . . . . . . . . . . . .  16
   7.  Use cases examples  . . . . . . . . . . . . . . . . . . . . .  21
     7.1.  Host-to-host or gateway-to-gateway under the same
           controller  . . . . . . . . . . . . . . . . . . . . . . .  21
     7.2.  Host-to-host or gateway-to-gateway under different
           security controllers  . . . . . . . . . . . . . . . . . .  23
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
     8.1.  IKE case  . . . . . . . . . . . . . . . . . . . . . . . .  26
     8.2.  IKE-less case . . . . . . . . . . . . . . . . . . . . . .  26
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  27
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  27
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  27
     10.2.  Informative References . . . . . . . . . . . . . . . . .  28
   Appendix A.  Appendix A: Common YANG model for IKE and IKEless
                cases  . . . . . . . . . . . . . . . . . . . . . . .  31
   Appendix B.  Appendix B: YANG model for IKE case  . . . . . . . .  37



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   Appendix C.  Appendix C: YANG model for IKE-less case . . . . . .  43
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  49

1.  Introduction

   Software-Defined Networking (SDN) is an architecture that enables
   users to directly program, orchestrate, control and manage network
   resources through software.  SDN paradigm relocates the control of
   network resources to a dedicated network element, namely SDN
   controller.  The SDN controller manages and configures the
   distributed network resources and provides an abstracted view of the
   network resources to the SDN applications.  The SDN application 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 are considering a centralized way
   of managing different security aspects.  For example, Software-
   Defined WANs (SD-WAN) advocates to manage IPsec SAs from a
   centralized point.  Therefore, with the growth of SDN-based scenarios
   where network resources are deployed in an autonomous manner, a
   mechanism to manage IPsec SAs according to the SDN architecture
   becomes more relevant.  Thus, the SDN-based service described in this
   document will autonomously deal with IPsec SAs management following a
   SDN paradigm.

   An example of usage can be the notion of Software Defined WAN (SD-
   WAN), SDN extension providing a software abstraction to create secure
   network overlays over traditional WAN and branch networks.  SD-WAN is
   based on IPsec as underlying security protocol and aims to provide
   flexible, automated, fast deployment and on-demand security network
   services.

   IPsec architecture [RFC4301] defines a clear separation between the
   processing to provide security services to IP packets and the key
   management procedures to establish the IPsec security associations.
   In this document, we define a service where the key management
   procedures can be carried by an external entity: the Security
   Controller.

   First, this document exposes the requirements to support the
   protection of data flows using IPsec [RFC4301].  We have considered
   two general cases:

   1)  IKE case.  The Network Security Function (NSF) implements the
       Internet Key Exchange (IKE) protocol and the IPsec databases: the
       Security Policy Database (SPD), the Security Association Database



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       (SAD) and the Peer Authorization Database (PAD).  The Security
       Controller is in charge of provisioning the NSF with the required
       information to IKE, the SPD and the PAD.

   2)  IKE-less case.  The NSF only implements the IPsec databases (no
       IKE implementation).  The Security 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 automated key management functionality is moved to
       the controller.

   In both cases, an interface/protocol is required to carry out this
   provisioning in a secure manner between the Security Controller and
   the NSF.  In particular, IKE case requires the provision of SPD and
   PAD entries and the IKE credential and information related with the
   IKE negotiation (e.g.  IKE_SA_INIT), and IKE-less case requires the
   management of SPD and SAD entries.  Based on YANG models in
   [netconf-vpn] and [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).

   This document considers two typical scenarios to manage autonomously
   IPsec SAs: gateway-to-gateway and host-to-host [RFC6071].  The
   analysis of the host-to-gateway (roadwarrior) scenario is out of
   scope of this document.  In these cases, host or gateways or both may
   act as NSFs.  Finally, it also discusses the situation where two NSFs
   are under the control of two different Security Controllers.

   NOTE: This work pays attention to the challenge "Lack of Mechanism
   for Dynamic Key Distribution to NSFs" defined in [RFC8192] in the
   particular case of the establishment and management of IPsec SAs.  In
   fact, this I-D could be considered as a proper use case for this
   particular challenge in [RFC8192].

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in 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 [RFC7149], [RFC4301],
   [ITU-T.Y.3300], [ONF-SDN-Architecture], [ONF-OpenFlow],




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   [ITU-T.X.1252], [ITU-T.X.800] and [I-D.ietf-i2nsf-terminology].  In
   addition, the following terms are defined below:

   o  Software-Defined Networking.  A set of techniques enabling to
      directly program, orchestrate, control, and manage network
      resources, which facilitates the design, delivery and operation of
      network services in a dynamic and scalable manner [ITU-T.Y.3300].

   o  Flow/Data Flow.  Set of network packets sharing a set of
      characteristics, for example IP dst/src values or QoS parameters.

   o  Security Controller.  A Controller is a management component that
      contains control plane functions to manage and facilitate
      information sharing, as well as execute security functions.  In
      the context of this document, it provides IPsec management
      information.

   o  Network Security Function (NSF).  Software that provides a set of
      security-related services.

   o  Flow-based NSF.  A NSF that inspects network flows according to a
      set of policies intended for enforcing security properties.  The
      NSFs considered in this document falls into this classification.

   o  Flow-based Protection Policy.  The set of rules defining the
      conditions under which a data flow MUST be protected with IPsec,
      and the rules that MUST be applied to the specific flow.

   o  Internet Key Exchange (IKE) v2 Protocol to establish IPsec
      Security Associations (SAs).  It requires information about the
      required authentication method (i.e. raw RSA/ECDSA keys or X.509
      certificates), DH groups, modes and algorithms for IKE SA
      negotiation, etc.

   o  Security Policy Database (SPD).  It includes information about
      IPsec policies direction (in, out), local and remote addresses,
      inbound and outboud SAs, etc.

   o  Security Associations Database (SAD).  It includes information
      about IPsec SAs, such as SPI, destination addresses,
      authentication and encryption algorithms and keys to protect IP
      flows.

   o  Peer Authorization Database (PAD).  It provides the link between
      the SPD and a security association management protocol such as IKE
      or the SDN-based solution described in this document.





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4.  Objectives

   o  To describe the architecture for the SDN-based IPsec management,
      which implements a security service to allow the establishment and
      management of IPsec security associations from a central point, in
      order to protect specific data flows.

   o  To define the interfaces required to manage and monitor the IPsec
      Security Associations in the NSF from a Security Controller.  YANG
      models are defined for configuration and state data for IPsec
      management.

5.  SDN-based IPsec management description

   As mentioned in Section 1, two cases are considered:

5.1.  IKE case: IKE/IPsec in the NSF

   In this case the NSF ships an IKEv2 implementation besides the IPsec
   support.  The Security Controller is in charge of managing and
   applying SPD and PAD entries (deriving and delivering IKE Credentials
   such as a pre-shared key, certificates, etc.), and applying other IKE
   configuration parameters (e.g.  IKE_SA_INIT algorithms) to the NSF
   for the IKE negotiation.

   With these entries, the IKEv2 implementation can operate to establish
   the IPsec SAs.  The application (administrator) establishes the IPsec
   requirements and information about the end points information
   (through the Client Facing Interface, [RFC8192]), and the Security
   Controller translates those requirements into IKE, SPD and PAD
   entries that will be installed into the NSF (through the NSF Facing
   Interface).  With that information, the NSF can just run IKEv2 to
   establish the required IPsec SA (when the data flow needs
   protection).  Figure 1 shows the different layers and corresponding
   functionality.
















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                +-------------------------------------------+
                |IPsec Management/Orchestration Application | Client or
                |          I2NSF Client                     | App Gateway
                +-------------------------------------------+
                                        |    Client Facing Interface
                +-------------------------------------------+
       Vendor   |             Application Support           |
       Facing<->|-------------------------------------------| Security
       Interface| IKE Credential,PAD and SPD entries Distr. | Controller
                +-------------------------------------------+
                                        |       NSF Facing Interface
                +-------------------------------------------+
                |                 I2NSF Agent               |
                |-------------------------------------------| Network
                |   IKE    |      IPsec(SPD,PAD)            | Security
                |-------------------------------------------| Function
                |         Data Protection and Forwarding    |
                +-------------------------------------------+

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

5.1.1.  Interface Requirements for IKE case

   SDN-based IPsec flow protection services provide dynamic and flexible
   management of IPsec SAs in flow-based NSF.  In order to support this
   capability in case IKE case, the following interface requirements are
   to be met:

   o  A YANG data model for configuration data for IKEv2, SPD and PAD.

   o  A YANG data model for state data for IKE, PAD, SPD and SAD (NOTE:
      the SAD entries are created in runtime by IKEv2.)

   o  In scenarios where multiple controllers are implicated, SDN-based
      IPsec management services may require a mechanism to discover
      which Security Controller is managing a specific NSF.  Moreover,
      an east-west interface [RFC7426] is required to exchange IPsec-
      related information.  For example, if two gateways need to
      establish an IPsec SA and both are under the control of two
      different controllers then both Security Controllers need to
      exchange information to properly configure their own gateways.
      That is, the may need to agree on whether IKEv2 authentication
      will be based on raw public keys or pre-shared keys.  In case of
      using pre-shared keys they will have to agree in the PSK.







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5.2.  IKE-less case: IPsec (no IKEv2) in the NSF

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

              +-----------------------------------------+
              |   IPsec Management  Application         | Client or
              |               I2NSF Client              | App Gateway
              +-----------------------------------------+
                                      |   Client Facing Interface
              +-----------------------------------------+
        Vendor|             Application Support         |
     Facing<->|-----------------------------------------| Security
     Interface|      SPD, SAD and PAD Entries Distr.    | Controller
              +-----------------------------------------+
                                      |   NSF Facing Interface
              +-----------------------------------------+
              |              I2NSF Agent                | Network
              |-----------------------------------------| Security
              |            IPsec (SPD,SAD)              | Function (NSF)
              |-----------------------------------------|
              |     Data Protection and Forwarding      |
              +-----------------------------------------+

            Figure 2: IKE-less case: IPsec (no IKE) in the NSF

   As shown in Figure 2, applications for flow protection run on the top
   of the Security Controller.  When an administrator enforces flow-
   based protection policies through the Client Facing Interface, the
   Security Controller translates those 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.

5.2.1.  Interface Requirements for IKE-less case

   In order to support the IKE-less case, the following requirements are
   to be met:

   o  A YANG data model for configuration data for SPD and SAD.

   o  A YANG data model for state data for SPD and SAD.

   o  In scenarios where multiple controllers are implicated, SDN-based
      IPsec management services may require a mechanism to discover
      which Security Controller is managing a specific NSF.  Moreover,
      an east-west interface [RFC7426] is required to exchange IPsec-



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      related information.  NOTE: A possible east-west protocol for this
      IKE-less case could be IKEv2.  However, this needs to be explore
      since the IKEv2 peers would be the Security Controllers.

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

   o  IV generation.

   o  prevent counter resets for same key.

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

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

   o  Generation of the IPsec SAs when required based on notifications
      (i.e. sadb_acquire).

   o  NAT Traversal discovery and management.

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

   o  SPI random generation.

   o  Cryptographic algorithm/s selection.

   o  Usage of extended sequence numbers.

   o  Establishment of proper traffic selectors.

5.3.  IKE case vs IKE-less case

   IKE case MAY be easier to deploy than IKE-less case because current
   gateways typically have an IKEv2/IPsec implementation.  Moreover
   hosts can install easily an IKE implementation.  As downside, the NSF
   needs more resources to hold IKEv2.  Moreover, the IKEv2
   implementation needs to implement an interface so that the I2NSF
   Agent can interact with them.

   Alternatively, IKE-less case allows lighter NSFs (no IKEv2
   implementation), which benefits the deployment in constrained NSFs.
   Moreover, IKEv2 does not need to be performed in gateway-to-gateway
   and host-to-host scenarios under the same Security Controller (see
   Section 7.1).  On the contrary, the overload of creating fresh IPsec
   SAs is shifted to the Security Controller since IKEv2 is not in the



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   NSF.  As a consequence, this may result in a more complex
   implementation in the controller side.  This overload may create some
   scalability issues when the number of NSFs is high.

   In general, literature around SDN-based network management using a
   centralized SDN controller is aware about scalability issues and
   solutions have been already provided (e.g. hierarchical SDN
   controllers; having multiple replicated SDN controllers, etc).  In
   the context of IPsec management, one straight way to reduce the
   overhead and the potential scalability issue in the Security
   Controller is to apply IKE case, described in this document, since
   the IPsec SAs are managed between NSFs without the involvement of the
   Security Controller at all, except by the initial IKE configuration
   provided by the Security Controller.  Other option with IKE-less is
   to use techniques already seen in SDN world such as, for example,
   hierarchical SDN controllers.  Other solutions, such as Controller-
   IKE [I-D.carrel-ipsecme-controller-ike], have proposed that NSFs
   provide their DH public keys to the Security Controller, so that the
   Security 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 re-key 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 Security Controller is not able to observe any
   session keys generated for the IPsec SAs because IKEv2 is in charge
   of negotiating the IPsec SAs.

5.3.1.  Rekeying process

   For IKE case, the rekeying process is carried out by IKEv2, following
   the information defined in the SPD and SAD.

   For IKE-less case, the Security Controller needs to take care of the
   rekeying process.  When the IPsec SA is going to expire (e.g.  IPsec
   SA soft lifetime), it has to create a new IPsec SA and remove the old
   one.  This rekeying process starts when the Security Controller
   receives a sadb_expire notification or it decides so, based on
   lifetime state data obtained from the NSF.

   To explain the rekeying process between two IPsec peers A and B, let
   assume that SPIa1 identifies the inbound SA in A and SPIb1 the
   inbound SA in B.

   1.  The Security Controller chooses two random values as SPI for the
       new inbound 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.



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       Then, the Security Controller creates an inbound SA with SPIa2 in
       A and another inbound SA in B with SPIb2.  It can send this
       information simultaneously to A and B.

   2.  Once the Security Controller receives confirmation from A and B,
       inbound SA are correctly installed.  Then it proceeds to send in
       parallel to A and B the outbound SAs: it sends the outbound SA to
       A with SPIb2 and the outbound SA to B with SPIa2.  At this point
       the new IPsec SA is ready.

   3.  Once the Security Controller receives confirmation from A and B,
       that the outbound SAs have been installed, the Security
       Controller deletes the old IPsec SAs from A (inbound SPIa1 and
       outbound SPIb1) and B (outbound SPIa1 and inbound SPIb1) in
       parallel.  It is worth noting that if the IPsec implementation
       can itself detect traffic on the new IPsec SA, and it can delete
       the old IPsec SA itself without instruction from the Security
       Controller, then this step 3 is not required.

5.3.2.  NSF state loss

   If one of the NSF restarts, it will lose the IPsec state (affected
   NSF).  By default, the Security 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 IKE case, and SPD and SAD information
   in IKE-less case.

   In both cases, the Security Controller is aware of the affected NSF
   (e.g. the NETCONF/TCP connection is broken with the affected NSF, the
   Security Controller is receiving sadb_bad-spi notification from a
   particular NSF, etc.).  Moreover, the Security Controller has a
   register about all the NSFs that have IPsec SAs with the affected
   NSF.  Therefore, it knows the affected IPsec SAs.

   In IKE case, the Security 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.  It can
   also instruct the affected NSF to send IKEv2 INITIAL_CONTACT.
   Finally, the Security Controller will instruct the affected NSF to
   start the IKEv2 negotiation with the new configuration.

   In IKE-less case, if the Security Controller detects that a NSF has
   lost the IPsec SAs (e.g. it reboots) it will delete the old IPsec SAs
   of the non-failed nodes established with the failed node (step 1).
   This prevents the non-failed nodes from leaking plaintext.  If the
   failed node comes to live, the Security Controller will configure the
   new inbound IPsec SAs between the failed node and all the nodes the



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   failed was talking to (step 2).  After these inbound IPsec SAs have
   been established, the Security Controller can configure the outbound
   IPsec SAs (step 3).

   Nevertheless other more optimized options can be considered (e.g.
   making IKEv2 configuration permanent between reboots).

5.3.3.  NAT Traversal

   In IKE case, IKEv2 already owns 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 of ESP packets ([RFC3948],
   [RFC8229]).  Note that the usage of TRANSPORT mode when NAT is
   required is forbidden in this specification.

   On the contrary, IKE-less case does not have any protocol in the NSFs
   to detect whether they are located behind a NAT or not.  However, the
   SDN paradigm generally assumes the Security Controller has a view of
   the network it controls.  This view is built either requesting
   information to the NSFs under its control, or because these NSFs
   inform to the Security Controller.  Based on this information, the
   Security Controller can 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]).

   For example, the Security Controller could directly request the NSF
   for specific data such as networking configuration, NAT support, etc.
   Protocols such as NETCONF or SNMP can be used here.  For example, RFC
   7317 [RFC7317] provides a YANG data model for system management or
   [I-D.ietf-opsawg-nat-yang] a data model for NAT management.  The
   Security Controller can use this NETCONF module with a gateway to
   collect NAT information or even configure a NAT.  In any case, if
   this NETCONF module is not available and the Security Controller
   cannot know if a host is behind a NAT or not, then IKE case should be
   the right choice and not the IKE-less.

6.  YANG configuration data models

   In order to support IKE case and IKE-less case we have modelled the
   different parameters and values that must be configured to manage
   IPsec SAs.  Specifically, IKE requires modeling IKEv2, SPD and PAD
   while IKE-less case requires configuration models for the SPD and
   SAD.  We have defined three models: ietf-ipsec-common (Appendix A),
   ietf-ipsec-ike (Appendix B, IKE case), ietf-ipsec-ikeless
   (Appendix C, IKE-less case).  Since the model ietf-ipsec-common has
   only typedef and groupings common to the other modules, in the



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   following we only show a simplified view of the ietf-ipsec-ike and
   ietf-ipsec-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 or 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.)



module: ietf-ipsec-ike
  +--rw ikev2
     +--rw pad
     |  +--rw pad-entry* [pad-entry-id]
     |     +--rw pad-entry-id                   uint64
     |     +--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
     |     |  +--:(id_key)
     |     |  |  +--rw id_key?                  string
     |     |  +--:(id_null)
     |     |  |  +--rw id_null?                 empty
     |     |  +--:(user_fqdn)
     |     |     +--rw user_fqdn?               string
     |     +--rw my-identifier                  string
     |     +--rw pad-auth-protocol?             auth-protocol-type
     |     +--rw auth-method
     |        +--rw auth-m?              auth-method-type
     |        +--rw eap-method
     |        |  +--rw eap-type?   uint8
     |        +--rw pre-shared
     |        |  +--rw secret?   yang:hex-string
     |        +--rw digital-signature
     |           +--rw ds-algorithm?     signature-algorithm-t



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     |           +--rw raw-public-key?   yang:hex-string
     |           +--rw key-data?         string
     |           +--rw key-file?         string
     |           +--rw ca-data*          string
     |           +--rw ca-file?          string
     |           +--rw cert-data?        string
     |           +--rw cert-file?        string
     |           +--rw crl-data?         string
     |           +--rw crl-file?         string
     |           +--rw oscp-uri?         inet:uri
     +--rw ike-conn-entry* [conn-name]
     |  +--rw conn-name                            string
     |  +--rw autostartup                          type-autostartup
     |  +--rw initial-contact?                     boolean
     |  +--rw version?                             enumeration
     |  +--rw ike-fragmentation?                   boolean
     |  +--rw ike-sa-lifetime-hard
     |  |  +--rw time?      yang:timestamp
     |  |  +--rw idle?      yang:timestamp
     |  |  +--rw bytes?     uint32
     |  |  +--rw packets?   uint32
     |  +--rw ike-sa-lifetime-soft
     |  |  +--rw time?      yang:timestamp
     |  |  +--rw idle?      yang:timestamp
     |  |  +--rw bytes?     uint32
     |  |  +--rw packets?   uint32
     |  |  +--rw action?    ic:lifetime-action
     |  +--rw ike-sa-authalg*                      ic:integrity-algorithm-t
     |  +--rw ike-sa-encalg*                       ic:encryption-algorithm-t
     |  +--rw dh_group                             uint32
     |  +--rw half-open-ike-sa-timer?              uint32
     |  +--rw half-open-ike-sa-cookie-threshold?   uint32
     |  +--rw local
     |  |  +--rw local-pad-id?   uint64
     |  +--rw remote
     |  |  +--rw remote-pad-id?   uint64
     |  +--rw espencap?                            esp-encap
     |  +--rw sport?                               inet:port-number
     |  +--rw dport?                               inet:port-number
     |  +--rw oaddr*                               inet:ip-address
     |  +--rw spd
     |  |  +--rw spd-entry* [spd-entry-id]
     |  |     +--rw spd-entry-id            uint64
     |  |     +--rw priority?               uint32
     |  |     +--rw anti-replay-window?     uint16
     |  |     +--rw names* [name]
     |  |     |  +--rw name-type?   ipsec-spd-name
     |  |     |  +--rw name         string



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     |  |     +--rw condition
     |  |     |  +--rw traffic-selector-list* [ts-number]
     |  |     |     +--rw ts-number               uint32
     |  |     |     +--rw direction?              ipsec-traffic-direction
     |  |     |     +--rw local-subnet?           inet:ip-prefix
     |  |     |     +--rw remote-subnet?          inet:ip-prefix
     |  |     |     +--rw upper-layer-protocol*   ipsec-upper-layer-proto
     |  |     |     +--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-operation
     |  |     |  +--rw ipsec-sa-cfg
     |  |     |     +--rw pfp-flag?            boolean
     |  |     |     +--rw extSeqNum?           boolean
     |  |     |     +--rw seqOverflow?         boolean
     |  |     |     +--rw statefulfragCheck?   boolean
     |  |     |     +--rw security-protocol?   ipsec-protocol
     |  |     |     +--rw mode?                ipsec-mode
     |  |     |     +--rw ah-algorithms
     |  |     |     |  +--rw ah-algorithm*   integrity-algorithm-t
     |  |     |     |  +--rw trunc-length?   uint32
     |  |     |     +--rw esp-algorithms
     |  |     |     |  +--rw authentication*   integrity-algorithm-t
     |  |     |     |  +--rw encryption*       encryption-algorithm-t
     |  |     |     |  +--rw tfc_pad?          uint32
     |  |     |     +--rw tunnel
     |  |     |        +--rw local?          inet:ip-address
     |  |     |        +--rw remote?         inet:ip-address
     |  |     |        +--rw bypass-df?      boolean
     |  |     |        +--rw bypass-dscp?    boolean
     |  |     |        +--rw dscp-mapping?   yang:hex-string
     |  |     |        +--rw ecn?            boolean
     |  |     +--rw spd-lifetime-soft
     |  |     |  +--rw time?      yang:timestamp
     |  |     |  +--rw idle?      yang:timestamp
     |  |     |  +--rw bytes?     uint32
     |  |     |  +--rw packets?   uint32
     |  |     |  +--rw action?    lifetime-action
     |  |     +--rw spd-lifetime-hard
     |  |     |  +--rw time?      yang:timestamp
     |  |     |  +--rw idle?      yang:timestamp
     |  |     |  +--rw bytes?     uint32
     |  |     |  +--rw packets?   uint32
     |  |     +--ro spd-lifetime-current



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     |  |        +--ro time?      yang:timestamp
     |  |        +--ro idle?      yang:timestamp
     |  |        +--ro bytes?     uint32
     |  |        +--ro packets?   uint32
     |  +--ro ike-sa-state
     |     +--ro uptime
     |     |  +--ro running?   yang:date-and-time
     |     |  +--ro since?     yang:date-and-time
     |     +--ro initiator?             boolean
     |     +--ro initiator-ikesa-spi?   uint64
     |     +--ro responder-ikesa-spi?   uint64
     |     +--ro nat-local?             boolean
     |     +--ro nat-remote?            boolean
     |     +--ro nat-any?               boolean
     |     +--ro espencap?              esp-encap
     |     +--ro sport?                 inet:port-number
     |     +--ro dport?                 inet:port-number
     |     +--ro oaddr*                 inet:ip-address
     |     +--ro established?           uint64
     |     +--ro rekey-time?            uint64
     |     +--ro reauth-time?           uint64
     |     +--ro child-sas* []
     |        +--ro spis
     |           +--ro spi-in?    ic:ipsec-spi
     |           +--ro spi-out?   ic:ipsec-spi
     +--ro number-ike-sas
        +--ro total?               uint32
        +--ro half-open?           uint32
        +--ro half-open-cookies?   uint32


6.2.  IKE-less case model

   The definition of the SPD model has been mainly extracted from the
   specification in section 4.4.1 and Appendix D in [RFC4301].  Unlike
   existing implementations (e.g.  XFRM), it is worth mentioning that
   this model follows [RFC4301] and, consequently, each policy (spd-
   entry) consists of one or more traffic selectors.

   The definition of the SAD model has been extracted from the
   specification in section 4.4.2 in [RFC4301].  Note that this model
   not only associates an IPsec SA with its corresponding policy (spd-
   entry-id) but also indicates the specific traffic selector that
   caused its establishment.  In other words, each traffic selector of a
   policy (spd-entry) generates a different IPsec SA (sad-entry).

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



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  module: ietf-ipsec-ikeless
    +--rw ietf-ipsec
       +--rw spd
       |  +--rw spd-entry* [spd-entry-id]
       |     +--rw spd-entry-id            uint64
       |     +--rw priority?               uint32
       |     +--rw anti-replay-window?     uint16
       |     +--rw names* [name]
       |     |  +--rw name-type?   ipsec-spd-name
       |     |  +--rw name         string
       |     +--rw condition
       |     |  +--rw traffic-selector-list* [ts-number]
       |     |     +--rw ts-number               uint32
       |     |     +--rw direction?              ipsec-traffic-direction
       |     |     +--rw local-subnet?           inet:ip-prefix
       |     |     +--rw remote-subnet?          inet:ip-prefix
       |     |     +--rw upper-layer-protocol*   ipsec-upper-layer-proto
       |     |     +--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-operation
       |     |  +--rw ipsec-sa-cfg
       |     |     +--rw pfp-flag?            boolean
       |     |     +--rw extSeqNum?           boolean
       |     |     +--rw seqOverflow?         boolean
       |     |     +--rw statefulfragCheck?   boolean
       |     |     +--rw security-protocol?   ipsec-protocol
       |     |     +--rw mode?                ipsec-mode
       |     |     +--rw ah-algorithms
       |     |     |  +--rw ah-algorithm*   integrity-algorithm-t
       |     |     |  +--rw trunc-length?   uint32
       |     |     +--rw esp-algorithms
       |     |     |  +--rw authentication*   integrity-algorithm-t
       |     |     |  +--rw encryption*       encryption-algorithm-t
       |     |     |  +--rw tfc_pad?          uint32
       |     |     +--rw tunnel
       |     |        +--rw local?          inet:ip-address
       |     |        +--rw remote?         inet:ip-address
       |     |        +--rw bypass-df?      boolean
       |     |        +--rw bypass-dscp?    boolean
       |     |        +--rw dscp-mapping?   yang:hex-string
       |     |        +--rw ecn?            boolean
       |     +--rw spd-lifetime-soft
       |     |  +--rw time?      yang:timestamp



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       |     |  +--rw idle?      yang:timestamp
       |     |  +--rw bytes?     uint32
       |     |  +--rw packets?   uint32
       |     |  +--rw action?    lifetime-action
       |     +--rw spd-lifetime-hard
       |     |  +--rw time?      yang:timestamp
       |     |  +--rw idle?      yang:timestamp
       |     |  +--rw bytes?     uint32
       |     |  +--rw packets?   uint32
       |     +--ro spd-lifetime-current
       |        +--ro time?      yang:timestamp
       |        +--ro idle?      yang:timestamp
       |        +--ro bytes?     uint32
       |        +--ro packets?   uint32
       +--rw sad
          +--rw sad-entry* [sad-entry-id]
             +--rw sad-entry-id                uint64
             +--rw spi?                        ic:ipsec-spi
             +--rw seq-number?                 uint64
             +--rw seq-number-overflow-flag?   boolean
             +--rw anti-replay-window?         uint16
             +--rw spd-entry-id?               uint64
             +--rw local-subnet?               inet:ip-prefix
             +--rw remote-subnet?              inet:ip-prefix
             +--rw upper-layer-protocol*       ipsec-upper-layer-proto
             +--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 security-protocol?          ic:ipsec-protocol
             +--rw sad-lifetime-hard
             |  +--rw time?      yang:timestamp
             |  +--rw idle?      yang:timestamp
             |  +--rw bytes?     uint32
             |  +--rw packets?   uint32
             +--rw sad-lifetime-soft
             |  +--rw time?      yang:timestamp
             |  +--rw idle?      yang:timestamp
             |  +--rw bytes?     uint32
             |  +--rw packets?   uint32
             |  +--rw action?    ic:lifetime-action
             +--rw mode?                       ic:ipsec-mode
             +--rw statefulfragCheck?          boolean
             +--rw dscp?                       yang:hex-string
             +--rw path-mtu?                   uint16
             +--rw tunnel



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             |  +--rw local?          inet:ip-address
             |  +--rw remote?         inet:ip-address
             |  +--rw bypass-df?      boolean
             |  +--rw bypass-dscp?    boolean
             |  +--rw dscp-mapping?   yang:hex-string
             |  +--rw ecn?            boolean
             +--rw espencap?                   esp-encap
             +--rw sport?                      inet:port-number
             +--rw dport?                      inet:port-number
             +--rw oaddr*                      inet:ip-address
             +--ro sad-lifetime-current
             |  +--ro time?      yang:timestamp
             |  +--ro idle?      yang:timestamp
             |  +--ro bytes?     uint32
             |  +--ro packets?   uint32
             +--ro stats
             |  +--ro replay-window?   uint32
             |  +--ro replay?          uint32
             |  +--ro failed?          uint32
             +--ro replay_state
             |  +--ro seq?      uint32
             |  +--ro oseq?     uint32
             |  +--ro bitmap?   uint32
             +--ro replay_state_esn
             |  +--ro bmp-len?         uint32
             |  +--ro oseq?            uint32
             |  +--ro oseq-hi?         uint32
             |  +--ro seq-hi?          uint32
             |  +--ro replay-window?   uint32
             |  +--ro bmp*             uint32
             +--rw ah-sa
             |  +--rw integrity
             |     +--rw integrity-algorithm?   ic:integrity-algorithm-t
             |     +--rw key?                   string
             +--rw esp-sa
                +--rw encryption
                |  +--rw encryption-algorithm?   ic:encryption-algorithm-t
                |  +--rw key?                    yang:hex-string
                |  +--rw iv?                     yang:hex-string
                +--rw integrity
                |  +--rw integrity-algorithm?   ic:integrity-algorithm-t
                |  +--rw key?                   yang:hex-string
                +--rw combined-enc-intr?   boolean

    notifications:
      +---n spdb_expire
      |  +--ro index?   uint64
      +---n sadb_acquire



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      |  +--ro base-list* [version]
      |  |  +--ro version       string
      |  |  +--ro msg_type?     sadb-msg-type
      |  |  +--ro msg_satype?   sadb-msg-satype
      |  |  +--ro msg_seq?      uint32
      |  +--ro local-subnet?           inet:ip-prefix
      |  +--ro remote-subnet?          inet:ip-prefix
      |  +--ro upper-layer-protocol*   ipsec-upper-layer-proto
      |  +--ro local-ports* [start end]
      |  |  +--ro start    inet:port-number
      |  |  +--ro end      inet:port-number
      |  +--ro remote-ports* [start end]
      |     +--ro start    inet:port-number
      |     +--ro end      inet:port-number
      +---n sadb_expire
      |  +--ro base-list* [version]
      |  |  +--ro version       string
      |  |  +--ro msg_type?     sadb-msg-type
      |  |  +--ro msg_satype?   sadb-msg-satype
      |  |  +--ro msg_seq?      uint32
      |  +--ro spi?                        ic:ipsec-spi
      |  +--ro anti-replay-window?         uint16
      |  +--ro encryption-algorithm?       ic:encryption-algorithm-t
      |  +--ro authentication-algorithm?   ic:integrity-algorithm-t
      |  +--ro sad-lifetime-hard
      |  |  +--ro time?      yang:timestamp
      |  |  +--ro idle?      yang:timestamp
      |  |  +--ro bytes?     uint32
      |  |  +--ro packets?   uint32
      |  +--ro sad-lifetime-soft
      |  |  +--ro time?      yang:timestamp
      |  |  +--ro idle?      yang:timestamp
      |  |  +--ro bytes?     uint32
      |  |  +--ro packets?   uint32
      |  +--ro sad-lifetime-current
      |     +--ro time?      yang:timestamp
      |     +--ro idle?      yang:timestamp
      |     +--ro bytes?     uint32
      |     +--ro packets?   uint32
      +---n sadb_bad-spi
         +--ro state    ic:ipsec-spi










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7.  Use cases examples

   This section explains how different traditional configurations, that
   is, host-to-host and gateway-to-gateway are deployed using this SDN-
   based IPsec management service.  In turn, these configurations will
   be typical in modern networks where, for example, virtualization will
   be key.

7.1.  Host-to-host or gateway-to-gateway under the same controller

                      +----------------------------------------+
                      |           Security Controller          |
                      |                                        |
                   (1)|   +--------------+ (2)+--------------+ |
      Flow-based  ------> |Translate into|--->| South. Prot. | |
      Security. Pol.  |   |IPsec Policies|    |              | |
                      |   +--------------+    +--------------+ |
                      |                          |     |       |
                      |                          |     |       |
                      +--------------------------|-----|-------+
                                                 |     |
                                                 | (3) |
                       |-------------------------+     +---|
                       V                                   V
           +----------------------+         +----------------------+
           |    NSF1              |<=======>|   NSF2               |
           |IKEv2/IPsec(SPD/PAD)  |         |IKEv2/IPsec(SPD/PAD)  |
           +----------------------+  (4)    +----------------------+

    Figure 3: Host-to-host / gateway-to-gateway single controller flow
                             for the IKE case.

   Figure 3 describes the case IKE case:

   1.  The administrator defines general flow-based security policies.
       The Security Controller looks for the NSFs involved (NSF1 and
       NSF2).

   2.  The Security Controller generates IKEv2 credentials for them and
       translates the policies into SPD and PAD entries.

   3.  The Security Controller inserts the SPD and PAD entries in both
       NSF1 and NSF2.

   4.  The flow is protected with the IPsec SA established with IKEv2.






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                        +----------------------------------------+
                        |    (1)     Security Controller         |
            Flow-based  |                                        |
            Security -----------|                                |
            Policy      |       V                                |
                        |  +---------------+ (2)+-------------+  |
                        |  |Translate into |--->| South. Prot.|  |
                        |  |IPsec policies |    |             |  |
                        |  +---------------+    +-------------+  |
                        |                         |     |        |
                        |                         |     |        |
                        +-------------------------| --- |--------+
                                                  |     |
                                                  | (3) |
                           |----------------------+     +--|
                           V                               V
                  +------------------+       +------------------+
                  |    NSF1          |<=====>|   NSF2           |
                  |IPsec(SPD/SAD)    |   4)  |IPsec(SPD/SAD)    |
                  +------------------+       +------------------+

    Figure 4: Host-to-host / gateway-to-gateway single controller flow
                            for IKE-less case.

   In IKE-less case, flow-based security policies defined by the
   administrator are translated into IPsec SPD entries and inserted into
   the corresponding NSFs.  Besides, fresh SAD entries will be also
   generated by the Security Controller and enforced in the NSFs.  In
   this case, the controller does not run any IKEv2 implementation, and
   it provides the cryptographic material for the IPsec SAs.  These keys
   will be also distributed securely through the southbound interface.
   Note that this is possible because both NSFs are managed by the same
   controller.

   Figure 4 describes the IKE-less, when a data packet needs to be
   protected in the path between the NSF1 and NSF2:

   1.  The administrator establishes the flow-based security policies.
       The Security Controller looks for the involved NSFs.

   2.  The Security Controller translates the flow-based security
       policies into IPsec SPD and SAD entries.

   3.  The Security Controller inserts the these entries in both NSF1
       and NSF2 IPsec databases.  It associates a lifetime to the IPsec
       SAs.  When this lifetime expires, the NSF will send a sadb_expire
       notification to the Security Controller in order to start the
       rekeying process.



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   4.  The flow is protected with the IPsec SA established by the
       Security Controller.

   Both NSFs could be two hosts that exchange traffic and require to
   establish an end-to-end security association to protect their
   communications (host-to-host) or two gateways (gateway-to-gateway),
   for example, within an enterprise that needs to protect the traffic
   between, for example, 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.  Beside, IaaS services
   providing virtualization environments are deployments solutions based
   on IPsec to provide secure channels between virtual instances (host-
   to-host) and providing VPN solutions for virtualized networks
   (gateway-to-gateway).

   In general (for IKE and IKE-less case), this system has various
   advantages:

   1.  It allows to create IPsec SAs among two NSFs, with only the
       application of more general flow-based security policies at the
       application layer.  Thus, administrators can manage all security
       associations in a centralized point with an abstracted view of
       the network.

   2.  All NSFs deployed after the application of the new policies are
       NOT manually configured, therefore allowing its deployment in an
       automated manner.

7.2.  Host-to-host or gateway-to-gateway under different security
      controllers

   It is also possible that two NSFs (i.e.  NSF1 and NSF2) are under the
   control of two different Security Controllers.  This may happen, for
   example, when two organizations, namely Enterprise A and Enterprise
   B, have their headquarters interconnected through a WAN connection
   and they both have deployed a SDN-based architecture to provide
   connectivity to all their clients.











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                +-------------+                 +-------------+
                |             |                 |             |
      Flow-based|   Security  |<===============>|   Security <--Flow-based
      Sec. Pol.--> Controller |        (3)      |  Controller | Sec. Pol.
            (1) |      A      |                 |      B      |   (2)
                +-------------+                 +-------------+
                     |                                 |
                     | (4)                         (4) |
                     V                                 V
          +----------------------+          +----------------------+
          |    NSF1              |<========>|   NSF2               |
          |IKEv2/IPsec(SPD/PAD)  |          |IKEv2/IPsec(SPD/PAD)  |
          +----------------------+  (5)     +----------------------+

           Figure 5: Different security controllers in IKE case

   Figure 5 describes IKE case when two security controllers are
   involved in the process.

   1.  The A's administrator establishes general Flow-based Security
       Policies in Security Controller A.

   2.  The B's administrator establishes general Flow-based Security
       Policies in Security Controller B.

   3.  The Security Controller A realizes that protection is required
       between the NSF1 and NSF2, but the NSF2 is under the control of
       another Security Controller (Security Controller B), so it starts
       negotiations with the other controller to agree on the IPsec SPD
       policies and IKEv2 credentials for their respective NSFs.  NOTE:
       This may require extensions in the East/West interface.

   4.  Then, both Security Controllers enforce the IKEv2 credentials and
       related parameters and the SPD and PAD entries in their
       respective NSFs.

   5.  The flow is protected with the IPsec SAs established with IKEv2
       between both NSFs.













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                +--------------+                   +--------------+
                |              |                   |              |
         Flow-based. --->                          |          <--- Flow-based
         Prot.  |   Security   |<=================>|   Security   |Sec.
         Pol.(1)|  Controller  |        (3)        |  Controller  |Pol. (2)
                |       A      |                   |       B      |
                +--------------+                   +--------------+
                        |                               |
                        | (4)                       (4) |
                        V                               V
                +------------------+      (5)       +------------------+
                |    NSF1          |<==============>|    NSF2          |
                |IPsec(SPD/SAD)    |                | IPsec(SPD/SAD)   |
                +------------------+                +------------------+

         Figure 6: Different security controllers in IKE-less case

   Figure 5 describes IKE-less case when two security controllers are
   involved in the process.

   1.  The A's administrator establishes general Flow Protection
       Policies in Security Controller A.

   2.  The B's administrator establishes general Flow Protection
       Policies in Security Controller B.

   3.  The Security Controller A realizes that the flow between NSF1 and
       NSF2 MUST be protected.  Nevertheless, the controller notices
       that NSF2 is under the control of another Security Controller, so
       it starts negotiations with the other controller to agree on the
       IPsec SPD and SAD entries that define the IPsec SAs.  NOTE: It
       would worth evaluating IKEv2 as the protocol for the East/West
       interface in this case.

   4.  Once the Security Controllers have agreed on key material and the
       details of the IPsec SAs, they both enforce this information into
       their respective NSFs.

   5.  The flow is protected with the IPsec SAs established by both
       Security Controllers in their respective NSFs.

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 [RFC8192].  On the one hand, it is important to
   note that there MUST exit a security association between the Security
   Controller and the NSFs to protect of the critical information



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   (cryptographic keys, configuration parameter, etc...) exchanged
   between these entities.  For example, if NETCONF is used as
   southbound protocol between the Security Controller and the NSFs, it
   is defined that TLS or SSH security association MUST be established
   between both entities.  On the other hand, we have divided this
   section in two parts to analyze different security considerations for
   both cases: NSF with IKEv2 (IKE case) and NSF without IKEv2 (IKE-less
   case).  In general, the Security Controller, as typically in the SDN
   paradigm, is a target for different type of attacks.  As a
   consequence, the Security Controller is a key entity in the
   infrastructure and MUST be protected accordingly.  In particular,
   according to this document, the Security Controller will handle
   cryptographic material so that the attacker may try to access this
   information.  Although, we can assume this attack will not likely to
   happen due to the assumed security measurements to protect the
   Security Controller, it deserves some analysis in the hypothetical
   the attack occurs.  The impact is different depending on the IKE case
   or IKE-less case.

8.1.  IKE case

   In IKE case, the Security Controller sends IKE credentials (PSK,
   public/private keys, certificates, etc...) to the NSFs using the
   security association between Security Controller and NSFs.  The
   general recommendation is that the Security Controller SHOULD NEVER
   store the IKE credentials after distributing them.  Moreover the NSFs
   MUST NOT allow the reading of these values once they have been
   applied by the Security Controller (i.e. write only operations).  One
   option is return always the same value (all 0s).  If the attacker has
   access to the Security Controller during the period of time that key
   material is generated, it may access to these values.  Since these
   values are used during NSF authentication in IKEv2, it may
   impersonate the affected NSFs.  Several recommendations are
   important.  If PSK authentication is used in IKEv2, the Security
   Controller SHOULD remove the PSK immediately after generating and
   distributing it.  Moreover, the PSK MUST have a proper length (e.g.
   minimu, 128 bit length) and strength.  If raw public keys are used,
   the Security Controller SHOULD remove the associated private key
   immediately after generating and distributing them to the NSFs.  If
   certificates are used, the NSF may generate the private key and
   exports the public key for certification to the Security Controller.

8.2.  IKE-less case

   In the IKE-less case, the controller sends the IPsec SA information
   to the SAD that includes the keys for integrity and encryption (when
   ESP is used).  That key material are symmetric keys to protect data
   traffic.  The general recommendation is that the Security Controller



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   SHOULD NEVER stores the keys after distributing them.  Moreover, the
   NSFs MUST NOT allow the reading of these values once they have been
   applied by the Security Controller (i.e. write only operations).
   Nevertheless, if the attacker has access to the Security Controller
   during the period of time that key material is generated, it may
   access to these values.  In other words, it may have access to the
   key material used in the distributed IPsec SAs and observe the
   traffic between peers.  In any case, some escenarios with special
   secure environments (e.g. physically isolated data centers) make this
   type of attack difficult.  Moreover, some scenarios such as IoT
   networks with constrained devices, where reducing implementation and
   computation overhead is important, can apply IKE-less case as a
   tradeoff between security and low overhead at the constrained device,
   at the cost of assuming the security impact described above.

9.  Acknowledgements

   Authors want to thank Paul Wouters, Sowmini Varadhan, David Carrel,
   Yoav Nir, Tero Kivinen, Graham Bartlett, Sandeep Kampati, Linda
   Dunbar, Carlos J.  Bernardos, Alejandro Perez-Mendez, Alejandro Abad-
   Carrascosa, Ignacio Martinez and Ruben Ricart for their valuable
   comments.

10.  References

10.1.  Normative References

   [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>.

   [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>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [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>.






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   [RFC8192]  Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R.,
              and J. Jeong, "Interface to Network Security Functions
              (I2NSF): Problem Statement and Use Cases", RFC 8192,
              DOI 10.17487/RFC8192, July 2017,
              <https://www.rfc-editor.org/info/rfc8192>.

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

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.ietf-i2nsf-framework]
              Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
              Kumar, "Framework for Interface to Network Security
              Functions", draft-ietf-i2nsf-framework-10 (work in
              progress), November 2017.

   [I-D.ietf-i2nsf-problem-and-use-cases]
              Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R.,
              and J. Jeong, "I2NSF Problem Statement and Use cases",
              draft-ietf-i2nsf-problem-and-use-cases-16 (work in
              progress), May 2017.

   [I-D.ietf-i2nsf-terminology]
              Hares, S., Strassner, J., Lopez, D., Xia, L., and H.
              Birkholz, "Interface to Network Security Functions (I2NSF)
              Terminology", draft-ietf-i2nsf-terminology-07 (work in
              progress), January 2019.

   [I-D.ietf-opsawg-nat-yang]
              Boucadair, M., Sivakumar, S., Jacquenet, C., Vinapamula,
              S., and Q. Wu, "A YANG Module for Network Address
              Translation (NAT) and Network Prefix Translation (NPT)",
              draft-ietf-opsawg-nat-yang-17 (work in progress),
              September 2018.









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   [I-D.jeong-i2nsf-sdn-security-services-05]
              Jeong, J., Kim, H., Park, J., Ahn, T., and S. Lee,
              "Software-Defined Networking Based Security Services using
              Interface to Network Security Functions", draft-jeong-
              i2nsf-sdn-security-services-05 (work in progress), July
              2016.

   [I-D.pfkey-spd]
              Sakane, S., "PF_KEY Extensions for IPsec Policy Management
              in KAME Stack", October 2002.

   [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.X.1252]
              "Baseline Identity Management Terms and Definitions",
              April 2010.

   [ITU-T.X.800]
              "Security Architecture for Open Systems Interconnection
              for CCITT Applications", March 1991.

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

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

   [netopeer]
              CESNET, CESNET., "NETCONF toolset Netopeer", November
              2016.

   [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>.






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   [RFC3549]  Salim, J., Khosravi, H., Kleen, A., and A. Kuznetsov,
              "Linux Netlink as an IP Services Protocol", RFC 3549,
              DOI 10.17487/RFC3549, July 2003,
              <https://www.rfc-editor.org/info/rfc3549>.

   [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>.

   [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>.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <https://www.rfc-editor.org/info/rfc7317>.

   [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>.

   [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>.

   [strongswan]
              CESNET, CESNET., "StrongSwan: the OpenSource IPsec-based
              VPN Solution", April 2017.














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Appendix A.  Appendix A: Common YANG model for IKE and IKEless cases



        <CODE BEGINS> file "ietf-ipsec-common@2019-03-11.yang"

        module ietf-ipsec-common{
                yang-version 1.1;
                namespace "urn:ietf:params:xml:ns:yang:ietf-ipsec-common";
                prefix "ipsec-common";

                import ietf-inet-types { prefix inet; }
                import ietf-yang-types { prefix yang; }

                import ietf-crypto-types {
                        prefix ct;
                        reference "draft-ietf-netconf-crypto-types-01: Common YANG Dta Types for Cryptography";
                }

                organization "IETF I2NSF (Interface to Network Security Functions) Working Group";

                contact
                " Rafael Marin Lopez
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Telf: +34868888501
                e-mail: rafa@um.es

                Gabriel Lopez Millan
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Tel: +34 868888504
                email: gabilm@um.es

                Fernando Pereniguez Garcia
                Department of Sciences and Informatics
                University Defense Center (CUD), Spanish Air Force Academy, MDE-UPCT
                30720 San Javier - Spain
                Tel: +34 968189946
                email: fernando.pereniguez@cud.upct.es
                ";

                description "Common Data model for SDN-based IPSec configuration.";

                revision "2019-03-11" {
                        description "Revision";



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                        reference "";
                }

                typedef encryption-algorithm-t {
                        type ct:encryption-algorithm-ref;
                        description "typedef";
                }

                typedef integrity-algorithm-t {
                        type ct:mac-algorithm-ref;
                        description
                                "This typedef enables importing modules to easily define an
                                identityref to the 'asymmetric-key-encryption-algorithm'
                                base identity.";
                }

                typedef ipsec-mode {
                        type enumeration {
                                enum TRANSPORT { description "Transport mode. No NAT support."; }
                                enum TUNNEL { description "Tunnel mode"; }
                        }
                        description "Type definition of IPsec mode";
                }

                typedef esp-encap {
                        type enumeration {
                                enum ESPINTCP { description "ESP in TCP encapulation.";}
                                enum ESPINTLS { description "ESP in TCP encapsulation using TLS.";}
                                enum ESPINUDP { description "ESP in UDP encapsulation. RFC 3948 ";}
                                enum NONE { description "NOT ESP encapsulation" ; }
                        }
                        description "type defining types of ESP encapsulation";
                }

                grouping encap { /* This is defined by XFRM */
                        description "Encapsulation container";
                        leaf espencap { type esp-encap; description "ESP in TCP, ESP in UDP or ESP in TLS";}
                        leaf sport {type inet:port-number; description "Encapsulation source port";}
                        leaf dport {type inet:port-number; description "Encapsulation destination port"; }
                        leaf-list oaddr {type inet:ip-address; description "Encapsulation Original Address ";}
                }

                typedef ipsec-protocol {
                        type enumeration {
                                enum ah { description "AH Protocol"; }
                                enum esp { description "ESP Protocol"; }
                        }
                        description "type define of ipsec security protocol";



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                }

                typedef ipsec-spi {
                        type uint32 { range "0..max"; }
                        description "SPI";
                }

                typedef lifetime-action {
                        type enumeration {
                                enum terminate-clear {description "Terminate the IPsec SA and allow the packets through";}
                                enum terminate-hold {description "Terminate the IPsec SA and drop the packets";}
                                enum replace  {description "Replace the IPsec SA with a new one";}
                        }
                        description "Action when lifetime expiration";
                }

                /*################## SPD basic groupings ####################*/

                typedef ipsec-traffic-direction {
                        type enumeration {
                                enum INBOUND { description "Inbound traffic"; }
                                enum OUTBOUND { description "Outbound traffic"; }
                        }
                        description "IPsec traffic direction";
                }

                typedef ipsec-spd-operation {
                        type enumeration {
                                enum PROTECT { description "PROTECT the traffic with IPsec"; }
                                enum BYPASS { description "BYPASS the traffic"; }
                                enum DISCARD { description "DISCARD the traffic"; }
                        }
                        description "The operation when traffic matches IPsec security policy";
                }

                typedef ipsec-upper-layer-proto {
                        type enumeration {
                                enum TCP { description "TCP traffic"; }
                                enum UDP { description "UDP traffic"; }
                                enum SCTP { description "SCTP traffic";}
                                enum DCCP { description "DCCP traffic";}
                                enum ICMP { description "ICMP traffic";}
                                enum IPv6-ICMP { description "IPv6-ICMP traffic";}
                                enum GRE {description "GRE traffic";}
                        }
                        description "Next layer proto on top of IP";
                }




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                typedef ipsec-spd-name {
                        type enumeration {
                                enum id_rfc_822_addr { description "Fully qualified user name string."; }
                                enum id_fqdn { description "Fully qualified DNS name."; }
                                enum id_der_asn1_dn { description "X.500 distinguished name."; }
                                enum id_key { description "IKEv2 Key ID."; }
                        }
                        description "IPsec SPD name type";
                }

                grouping lifetime {
                        description "lifetime current state data";
                        leaf time {type yang:timestamp; default 0; description "Time since the element is added";}
                        leaf idle {type yang:timestamp; default 0; description "Time the element is in idle state";}
                        leaf bytes { type uint32; default 0; description "Lifetime in bytes number";}
                        leaf packets {type uint32; default 0; description "Lifetime in packets number";}
                }

                /*################## SAD and SPD common basic groupings ####################*/

                grouping port-range  {
                        description "Port range grouping";
                        leaf start { type inet:port-number; description "Start Port Number"; }
                        leaf end { type inet:port-number; description "End Port Number"; }
                }

                grouping tunnel-grouping {
                        description "Tunnel mode grouping";
                        leaf local{ type inet:ip-address; description "Local tunnel endpoint"; }
                        leaf remote{ type inet:ip-address; description "Remote tunnel enpoint"; }
                        leaf bypass-df { type boolean; description "Bypass DF bit"; }
                        leaf bypass-dscp { type boolean; description "Bypass DSCP"; }
                        leaf dscp-mapping { type yang:hex-string; description "DSCP mapping"; }
                        leaf ecn { type boolean; description "Bit ECN"; } /* RFC 4301 ASN1 notation. Annex C*/
                }

                grouping selector-grouping {
                        description "Traffic selector grouping";

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

                        leaf-list upper-layer-protocol { type ipsec-upper-layer-proto; description "List of Upper Layer Protocol";}

                        list local-ports {
                                key "start end";
                                uses port-range;
                                description "List of local ports. When the upper-layer-protocol is ICMP this 16 bit value respresents code and type as mentioned in RFC 4301";



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                        }

                        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 respresents code and type as mentioned in RFC 4301";
                        }
                }

                /*################## SPD ipsec-policy-grouping ####################*/

                grouping ipsec-policy-grouping {

                        description "Holds configuration information for an IPSec SPD entry.";

                        leaf spd-entry-id { type uint64; description "SPD entry id "; }
                        leaf priority {type uint32; default 0; description "Policy priority";}
                        leaf anti-replay-window { type uint16 { range "0 | 32..1024"; } description "Anti replay window size"; }

                        list names {
                                key "name";
                                leaf name-type { type ipsec-spd-name; description "SPD name type."; }
                                leaf name { type string; description "Policy name"; }
                                description "List of policy names";
                        }

                        container condition {
                                description "SPD condition - RFC4301";
                                list traffic-selector-list {
                                        key "ts-number";
                                        leaf ts-number { type uint32; description "Traffic selector number"; }
                                        leaf direction { type ipsec-traffic-direction; description "in/out"; }
                                        uses selector-grouping;
                                        ordered-by user;
                                        description "List of traffic selectors";
                                }
                        }

                        container processing-info {
                                description "SPD processing - RFC4301";
                                leaf action{ type ipsec-spd-operation; mandatory true; description "Bypass or discard, container ipsec-sa-cfg is empty";}

                                container ipsec-sa-cfg {
                                        when "../action = 'PROTECT'";

                                        leaf pfp-flag { type boolean; description "Each selector has with a pfp flag."; }
                                        leaf extSeqNum { type boolean; description "TRUE 64 bit counter, FALSE 32 bit"; }
                                        leaf seqOverflow { type boolean; description "TRUE rekey, FALSE terminare &amp; audit"; }



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                                        leaf statefulfragCheck { type boolean; description "Indicates whether (TRUE) or not (FALSE) stateful fragment checking (RFC 4301) applies to the SA to be created."; }
                                        leaf security-protocol { type ipsec-protocol; description "Security protocol of IPsec SA: Either AH or ESP."; }
                                        leaf mode { type ipsec-mode; description "transport/tunnel"; }

                                        container ah-algorithms {
                                                when "../security-protocol = 'ah'";
                                                leaf-list ah-algorithm { type integrity-algorithm-t; description "Configure Authentication Header (AH)."; }
                                                leaf trunc-length { type uint32; description "Truncation value for AH algorithm"; }
                                                description "AH algoritms ";
                                        }

                                        container esp-algorithms {
                                                when "../security-protocol = 'esp'";
                                                description "Configure Encapsulating Security Payload (ESP).";
                                                leaf-list authentication { type integrity-algorithm-t; description "Configure ESP authentication"; }
                                                /* With AEAD algorithms, the authentication node is not used */
                                                leaf-list encryption { type encryption-algorithm-t; description "Configure ESP encryption"; }
                                                leaf tfc_pad { type uint32; default 0; description "TFC padding for ESP encryption"; }
                                        }

                                        container tunnel {
                                                when "../mode = 'TUNNEL'";
                                                uses tunnel-grouping;
                                                description "tunnel grouping container";
                                        }

                                        description " IPSec SA configuration container";
                                }
                        }

                        container spd-lifetime-soft {
                                description "SPD lifetime hard state data";
                                uses lifetime;
                                leaf action {type lifetime-action; description "Action lifetime";}
                        }

                        container spd-lifetime-hard {
                                description "SPD lifetime hard state data. The action after the lifetime is to remove the SPD entry.";
                                uses lifetime;
                        }

                        // State data for an IPsec SPD entry
                        container spd-lifetime-current {
                                uses lifetime;
                                config false;
                                description "SPD lifetime current state data";
                        }
                } /* grouping ipsec-policy-grouping */



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        }
    <CODE ENDS>



Appendix B.  Appendix B: YANG model for IKE case




        <CODE BEGINS> file "ietf-ipsec-ike@2019-03-11.yang"

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

                import ietf-inet-types { prefix inet; }
                import ietf-yang-types { prefix yang; }

                import ietf-crypto-types {
                        prefix ct;
                        reference "draft-ietf-netconf-crypto-types-01: Common YANG Data Types for Cryptography";
                }

                import ietf-ipsec-common {
                        prefix ic;
                        reference "Common Data model for SDN-based IPSec configuration";
                }

                organization "IETF I2NSF (Interface to Network Security Functions) Working Group";

                contact
                " Rafael Marin Lopez
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Telf: +34868888501
                e-mail: rafa@um.es

                Gabriel Lopez Millan
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Tel: +34 868888504
                email: gabilm@um.es

                Fernando Pereniguez Garcia



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                Department of Sciences and Informatics
                University Defense Center (CUD), Spanish Air Force Academy, MDE-UPCT
                30720 San Javier - Spain
                Tel: +34 968189946
                email: fernando.pereniguez@cud.upct.es
                ";

                description "Data model for IKE case.";

                revision "2019-03-11" {
                        description "Revision 1.1";
                        reference "";
                }

                typedef type-autostartup {
                        type enumeration {
                                enum ADD {description "IPsec configuration is only loaded but not started.";}
                                enum ON-DEMAND {description "IPsec configuration is loaded and transferred to the NSF's kernel";}
                                enum START { description "IPsec configuration is loaded and transferred to the NSF's kernel, and the IKEv2 based IPsec SAs are established";}
                        }
                        description "Different policies of when to start an IKEv2 based IPsec SA";
                }

                typedef auth-protocol-type {
                        type enumeration {
                                enum IKEv2 { description "Authentication protocol based on IKEv2"; }
                        }
                        description "IKE authentication protocol version";
                }

                typedef pfs-group {
                        type enumeration {
                                enum NONE {description "NONE";}
                                enum 768-bit-MODP {description "768-bit MODP Group";}
                                enum 1024-bit-MODP {description "1024-bit MODP Group";}
                                enum 1536-bit-MODP {description "1536-bit MODP Group";}
                                enum 2048-bit-MODP {description "2048-bit MODP Group";}
                                enum 3072-bit-MODP {description "3072-bit MODP Group";}
                                enum 4096-bit-MODP {description "4096-bit MODP Group";}
                                enum 6144-bit-MODP {description "6144-bit MODP Group";}
                                enum 8192-bit-MODP {description "8192-bit MODP Group";}
                        }
                        description "PFS group for IPsec rekey";
                }

                /*################## PAD  ####################*/

                typedef auth-method-type {



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                        /* Most implementations also provide XAUTH protocol, others used are: BLISS, P12, NTLM, PIN */
                        type enumeration {
                                enum pre-shared { description "Select pre-shared key message as the authentication method"; }
                                enum eap { description "Select EAP as the authentication method"; }
                                enum digital-signature { description "Select digital signature method";}
                                enum null {description "null authentication";}
                        }
                        description "Peer authentication method";
                }

                typedef signature-algorithm-t {
                        type ct:signature-algorithm-ref; // We must reference to "signature-algorithm-ref" but we temporary use hash-algorithm-ref
                        description "This typedef enables referencing to any digital signature algorithm";
                }

                grouping auth-method-grouping {
                        description "Peer authentication method data";

                        container auth-method {
                                description "Peer authentication method container";

                                leaf auth-m { type auth-method-type; description "Type of authentication method (pre-shared, eap, digital signature, null)"; }

                                container eap-method {
                                        when "../auth-m = 'eap'";
                                        leaf eap-type { type uint8; description "EAP method type"; }
                                        description "EAP method description used when auth method is eap";
                                }

                                container pre-shared {
                                        when "../auth-m[.='pre-shared' or .='eap']";
                                        leaf secret { type yang:hex-string; description "Pre-shared secret value";}
                                        description "Shared secret value";
                                }

                                container digital-signature {
                                        when "../auth-m[.='digital-signature' or .='eap']";
                                        leaf ds-algorithm {type signature-algorithm-t; description "Name of the digital signature algorithm";}
                                        leaf raw-public-key {type yang:hex-string; description "RSA raw public key" ;}
                                        leaf key-data { type string; description "RSA private key data - PEM"; }
                                        leaf key-file { type string; description "RSA private key file name "; }
                                        leaf-list ca-data { type string; description "List of trusted CA certs - PEM"; }
                                        leaf ca-file { type string; description "List of trusted CA certs file"; }
                                        leaf cert-data { type string; description "X.509 certificate data - PEM4"; }
                                        leaf cert-file { type string; description "X.509 certificate file"; }
                                        leaf crl-data { type string; description "X.509 CRL certificate data in base64"; }
                                        leaf crl-file { type string; description " X.509 CRL certificate file"; }
                                        leaf oscp-uri { type inet:uri; description "OCSP URI";}



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                                        description "RSA signature container";
                                }
                        }
                }

                grouping identity-grouping {
                        description "Identification type. It is an union identity";
                        choice identity {
                                description "Choice of identity.";
                                leaf ipv4-address { type inet:ipv4-address; description "Specifies the identity as a single four (4) octet IPv4 address. An example is, 10.10.10.10. "; }
                                leaf ipv6-address { type inet:ipv6-address; description "Specifies the identity as a single sixteen (16) octet IPv6 address. An example is FF01::101, 2001:DB8:0:0:8:800:200C:417A ."; }
                                leaf fqdn-string { type inet:domain-name; description "Specifies the identity as a Fully-Qualified Domain Name (FQDN) string. An example is: example.com. The string MUST not contain any terminators (e.g., NULL, CR, etc.)."; }
                                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.)."; }
                                leaf dnX509 { type string; description "Specifies the identity as a distinguished name in the X.509 tradition."; }
                                leaf id_key { type string; description "Key id"; }
                                leaf id_null { type empty; description "RFC 7619" ; }
                                leaf user_fqdn { type string; description "User FQDN"; }
                        }
                        leaf my-identifier { type string; mandatory true; description "id used for authentication"; }
                }

                /*################ end PAD ##################*/


                /*################## IKEv2-grouping ##################*/
                grouping ike-proposal {
                        description "IKEv2 proposal grouping";

                        container ike-sa-lifetime-hard {
                                description "IKE SA lifetime hard";
                                uses ic:lifetime;
                        }

                        container ike-sa-lifetime-soft {
                                description "IPsec SA lifetime soft";
                                uses ic:lifetime;
                                leaf action {type ic:lifetime-action; description "Action lifetime";}
                        }

                        leaf-list ike-sa-authalg { type ic:integrity-algorithm-t; description "Auth algorigthm for IKE SA";}
                        leaf-list ike-sa-encalg { type ic:encryption-algorithm-t; description "Auth algorigthm for IKE SAs";}
                        leaf dh_group { type uint32; mandatory true; description "Group number for Diffie Hellman Exponentiation";}
                        leaf half-open-ike-sa-timer { type uint32; description "Set the half-open IKE SA timeout duration" ; }
                        leaf half-open-ike-sa-cookie-threshold { type uint32; description "Number of half-open IKE SAs that activate the cookie mechanism." ; }
                }

                grouping ike-child-sa-info {
                        description "IPsec SA Information";



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                        leaf-list pfs_groups { type pfs-group; description "If non-zero, require perfect forward secrecy when requesting new SA. The non-zero value is the required group number"; }

                        container child-sa-lifetime-soft {
                                description "IPsec SA lifetime soft";
                                uses ic:lifetime;
                                leaf action {type ic:lifetime-action; description "action lifetime";}
                        }

                        container child-sa-lifetime-hard {
                                description "IPsec SA lifetime hard. The action will be to terminate the IPsec SA.";
                                uses ic:lifetime;
                        }
                }

                /*################## End IKEv2-grouping ##################*/


                container ikev2 {

                        description "Configure the IKEv2 software";

                        container pad {
                                description "Configure Peer Authorization Database (PAD)";
                                list pad-entry {
                                        key "pad-entry-id";
                                        ordered-by user;
                                        description "Peer Authorization Database (PAD)";
                                        leaf pad-entry-id { type uint64; description "SAD index. ";}
                                        uses identity-grouping;
                                        leaf pad-auth-protocol { type auth-protocol-type; description "IKEv2, etc. ";}
                                        uses auth-method-grouping;
                                }
                        }

                        list ike-conn-entry {
                                key "conn-name";
                                description "IKE peer connection information";
                                leaf conn-name  { type string; mandatory true; description "Name of IKE connection";}
                                leaf autostartup { type type-autostartup; mandatory true; description "if True: automatically start tunnel at startup; else we do lazy tunnel setup based on trigger from datapath";}
                                leaf initial-contact {type boolean; default false; description "This IKE SA is the only currently active between the authenticated identities";}
                                leaf version {
                                        type enumeration {
                                                enum ikev2 {value 2; description "IKE version 2";}
                                        }
                                        description "IKE version";
                                }

                                leaf ike-fragmentation { type boolean; description "Whether to use IKEv2 fragmentation as per RFC 7383 (TRUE or FALSE)"; }



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                                uses ike-proposal;

                                container local {
                                        description "Local peer connection information";
                                        leaf local-pad-id { type uint64; description " ";}
                                }

                                container remote {
                                        description "Remote peer connection information";
                                        leaf remote-pad-id { type uint64; description " ";}
                                }

                                uses ic:encap;

                                container spd {
                                        description "Configure the Security Policy Database (SPD)";
                                        list spd-entry {
                                                key "spd-entry-id";
                                                uses ic:ipsec-policy-grouping;
                                                ordered-by user;
                                                description "List of SPD entries";
                                        }
                                }

                                container ike-sa-state {
                                        container uptime {
                                                description "IKE service uptime";
                                                leaf running { type yang:date-and-time;  description "Relative uptime";}
                                                leaf since   { type yang:date-and-time;  description "Absolute uptime";}
                                        }

                                        leaf initiator { type boolean; description "It is acting as initiator in this connection";}
                                        leaf initiator-ikesa-spi {type uint64; description "Initiator's IKE SA SPI";}
                                        leaf responder-ikesa-spi {type uint64; description "Responsder's IKE SA SPI";}
                                        leaf nat-local {type boolean; description "YES, if local endpoint is behind a NAT";}
                                        leaf nat-remote {type boolean; description "YES, if remote endpoint is behind a NAT";}
                                        leaf nat-any {type boolean; description "YES, if both local and remote endpoints are behind a NAT";}

                                        uses ic:encap;

                                        leaf established {type uint64; description "Seconds the IKE SA has been established";}
                                        leaf rekey-time {type uint64; description "Seconds before IKE SA gets rekeyed";}
                                        leaf reauth-time {type uint64; description "Seconds before IKE SA gets re-authenticated";}
                                        list child-sas {
                                                container spis{
                                                        description "IPsec SA's SPI '";
                                                        leaf spi-in {type ic:ipsec-spi;  description "Security Parameter Index for inbound IPsec SA";}
                                                        leaf spi-out {type ic:ipsec-spi;  description "Security Parameter Index for the corresponding outbound IPsec SA";}



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                                                }
                                                description "State data about IKE CHILD SAs";
                                        }
                                        config false;
                                        description "IKE state data";
                                } /* ike-sa-state */
                        } /* ike-conn-entries */


                        container number-ike-sas{
                                leaf total {type uint32; description "Total number of IKEv2 SAs";}
                                leaf half-open {type uint32; description "Number of half-open IKEv2 SAs";}
                                leaf half-open-cookies {type uint32; description "Number of half open IKE SAs with cookie activated" ;}
                                config false;
                                description "Number of IKE SAs";
                        }
                }  /* container ikev2 */
        }

        <CODE ENDS>



Appendix C.  Appendix C: YANG model for IKE-less case





        <CODE BEGINS> file "ietf-ipsec-ikeless@2019-03-11.yang"

        module ietf-ipsec-ikeless {

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

                prefix "ipsec-ikeless";

                import ietf-yang-types { prefix yang; }

                import ietf-ipsec-common {
                        prefix ic;
                        reference "Common Data model for SDN-based IPSec configuration";
                }

                organization "IETF I2NSF (Interface to Network Security Functions) Working Group";

                contact



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                " Rafael Marin Lopez
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Telf: +34868888501
                e-mail: rafa@um.es

                Gabriel Lopez Millan
                Dept. Information and Communications Engineering (DIIC)
                Faculty of Computer Science-University of Murcia
                30100 Murcia - Spain
                Tel: +34 868888504
                email: gabilm@um.es

                Fernando Pereniguez Garcia
                Department of Sciences and Informatics
                University Defense Center (CUD), Spanish Air Force Academy, MDE-UPCT
                30720 San Javier - Spain
                Tel: +34 968189946
                email: fernando.pereniguez@cud.upct.es
                ";

                description "Data model for IKE-less case";

                revision "2019-03-11" {
                        description "Revision";
                        reference "";
                }

                /*################## SAD grouping ####################*/
                grouping ipsec-sa-grouping {
                        description "Configure Security Association (SA). Section 4.4.2.1 in RFC 4301";

                        leaf sad-entry-id {type uint64; description "This value identifies a specific entry in the SAD";}
                        leaf spi { type ic:ipsec-spi;  description "Security Parameter Index. This may not be unique for a particular SA";}
                        leaf seq-number { type uint64; description "Current sequence number of IPsec packet."; }
                        leaf seq-number-overflow-flag { type boolean; description "The flag indicating whether overflow of the sequence number counter should prevent transmission of additional packets on the SA, or whether rollover is permitted."; }
                        leaf anti-replay-window { type uint16 { range "0 | 32..1024"; } description "Anti replay window size"; }
                        leaf spd-entry-id {type uint64; description "This value links the SA with the SPD entry";}

                        uses ic:selector-grouping;

                        leaf security-protocol { type ic:ipsec-protocol; description "Security protocol of IPsec SA: Either AH or ESP."; }

                        container sad-lifetime-hard {
                                description "SAD lifetime hard state data. The action associated is terminate.";
                                uses ic:lifetime;
                        }



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                        container sad-lifetime-soft {
                                description "SAD lifetime hard state data";
                                uses ic:lifetime;
                                leaf action {type ic:lifetime-action; description "action lifetime";}
                        }

                        leaf mode { type ic:ipsec-mode; description "SA Mode"; }
                        leaf statefulfragCheck { type boolean; description "Indicates whether (TRUE) or not (FALSE) stateful fragment checking (RFC 4301) applies to this SA."; }

                        leaf dscp { type yang:hex-string; description "DSCP value"; }
                        leaf path-mtu { type uint16; description "Maximum size of an IPsec packet that can be transmitted without fragmentation"; }

                        container tunnel {
                                when "../mode = 'TUNNEL'";
                                uses ic:tunnel-grouping;
                                description "Container for tunnel grouping";
                        }

                        uses ic:encap;

                        // STATE DATA for SA
                        container sad-lifetime-current {
                                uses ic:lifetime;
                                config false;
                                description "SAD lifetime current state data";
                        }

                        container stats { // xfrm.h
                                leaf replay-window {type uint32; default 0; description " "; }
                                leaf replay {type uint32; default 0; description "packets detected out of the replay window and dropped because they are replay packets";}
                                leaf failed {type uint32; default 0; description "packets detected out of the replay window ";}
                                config false;
                                description "SAD statistics";
                        }

                        container replay_state { // xfrm.h
                                leaf seq {type uint32; default 0; description "input traffic sequence number when anti-replay-window != 0";}
                                leaf oseq {type uint32; default 0; description "output traffic sequence number";}
                                leaf bitmap {type uint32; default 0; description "";}
                                config false;
                                description "Anti-replay Sequence Number state";
                        }

                        container replay_state_esn { // xfrm.h
                                leaf bmp-len {type uint32; default 0; description "bitmap length for ESN"; }
                                leaf oseq { type uint32; default 0; description "output traffic sequence number"; }
                                leaf oseq-hi { type uint32; default 0; description ""; }
                                leaf seq-hi { type uint32; default 0; description ""; }



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                                leaf replay-window {type uint32; default 0; description ""; }
                                leaf-list bmp { type uint32; description "bitmaps for ESN (depends on bmp-len) "; }
                                config false;
                                description "Anti-replay Extended Sequence Number (ESN) state";
                        }

                }
                /*################## end SAD grouping ##################*/


                /*################# Register grouping #################*/
                typedef sadb-msg-type {
                        type enumeration {
                                enum sadb_acquire { description "SADB_ACQUIRE"; }
                                enum sadb_expire { description "SADB_EXPIRE"; }
                        }
                        description "Notifications (PF_KEY message types) that must be forwarded by the NSF to the controller in IKE-less case";
                }

                typedef sadb-msg-satype {
                         type enumeration {
                                enum sadb_satype_unspec { description "SADB_SATYPE_UNSPEC"; }
                                enum sadb_satype_ah { description "SADB_SATYPE_AH"; }
                                enum sadb_satype_esp { description "SADB_SATYPE_ESP"; }
                                enum sadb_satype_rsvp { description "SADB_SATYPE_RSVP"; }
                                enum sadb_satype_ospfv2 { description "SADB_SATYPE_OSPFv2"; }
                                enum sadb_satype_ripv2 { description "SADB_SATYPE_RIPv2"; }
                                enum sadb_satype_mip { description "SADB_SATYPE_MIP"; }
                                enum sadb_satype_max { description "SADB_SATYPE_MAX"; }
                        }
                        description "PF_KEY Security Association types";
                }

                grouping base-grouping {
                        description "Configuration for the  message header format";
                        list base-list {
                                         key "version";
                                         leaf version { type string; description "Version of PF_KEY (MUST be PF_KEY_V2)"; }
                                         leaf msg_type { type sadb-msg-type; description "Identifies the type of message"; }
                                         leaf msg_satype { type sadb-msg-satype; description "Defines the type of Security Association"; }
                                         leaf msg_seq { type uint32; description "Sequence number of this message."; }
                                         description "Configuration for a specific message header format";
                        }
                }
                /*################# End Register grouping #################*/


                /*################## IPsec configuration ##################*/



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                container ietf-ipsec {
                        description "IPsec configuration";

                        container spd {
                                                description "Configure the Security Policy Database (SPD)";
                                                list spd-entry {
                                                   key "spd-entry-id";
                                                   uses ic:ipsec-policy-grouping;
                                                   ordered-by user;
                                                   description "List of SPD entries";
                                                }
                        }

                        container sad {
                                description "Configure the IPSec Security Association Database (SAD)";

                                list sad-entry {
                                        key "sad-entry-id";

                                        uses ipsec-sa-grouping;

                                        container ah-sa {
                                                when "../security-protocol = 'ah'";
                                                description "Configure Authentication Header (AH) for SA";
                                                container integrity {
                                                        description "Configure integrity for IPSec Authentication Header (AH)";
                                                        leaf integrity-algorithm { type ic:integrity-algorithm-t; description "Configure Authentication Header (AH)."; }
                                                        leaf key { type string; description "AH key value";}
                                                }
                                        }

                                        container esp-sa {
                                                when "../security-protocol = 'esp'";
                                                description "Set IPSec Encapsulation Security Payload (ESP)";

                                                container encryption {
                                                        description "Configure encryption for IPSec Encapsulation Secutiry Payload (ESP)";
                                                        leaf encryption-algorithm { type ic:encryption-algorithm-t; description "Configure ESP encryption"; }
                                                        leaf key { type yang:hex-string; description "ESP encryption key value";}
                                                        leaf iv {type yang:hex-string; description "ESP encryption IV value"; }
                                                }

                                                container integrity {
                                                        description "Configure authentication for IPSec Encapsulation Secutiry Payload (ESP)";
                                                        leaf integrity-algorithm { type ic:integrity-algorithm-t; description "Configure Authentication Header (AH)."; }
                                                        leaf key { type yang:hex-string; description "ESP integrity key value";}
                                                }




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                                                /* With AEAD algorithms, the integrity node is not used */

                                                leaf combined-enc-intr { type boolean; description "ESP combined mode algorithms. The algorithm is specified in encryption-algorithm";}
                                        }
                                        description "List of SAD entries";
                                }
                        }
                } /* container ietf-ipsec */


                /*################## RPC and Notifications ##################*/

                // These RPCs are needed by a Security Controller in IKEless case

                notification spdb_expire {
                        description "A SPD entry has expired";
                        leaf index { type uint64; description "SPD index. RFC4301 does not mention an index however real implementations (e.g. XFRM or PFKEY_v2 with KAME extensions provide a policy index to refer a policy. "; }
                }

                notification sadb_acquire {
                        description "A IPsec SA is required ";
                        uses base-grouping;
                        uses ic:selector-grouping; // To indicate the concrete traffic selector of the policy that triggered this acquire.
                }

                notification sadb_expire {
                        description "A IPsec SA expiration (soft or hard)";

                        uses base-grouping;
                        leaf spi { type ic:ipsec-spi;  description "Security Parameter Index";}
                        leaf anti-replay-window { type uint16 { range "0 | 32..1024"; } description "Anti replay window"; }

                        leaf encryption-algorithm { type ic:encryption-algorithm-t; description "encryption algorithm of the expired SA"; }
                        leaf authentication-algorithm { type ic:integrity-algorithm-t; description "authentication algorithm of the expired SA"; }

                        container sad-lifetime-hard {
                                description "SAD lifetime hard state data";
                                uses ic:lifetime;
                        }
                        container sad-lifetime-soft {
                                description "SAD lifetime soft state data";
                                uses ic:lifetime;
                        }

                        container sad-lifetime-current {
                                description "SAD lifetime current state data";
                                uses ic:lifetime;
                        }



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                }

                notification sadb_bad-spi {
                        description "Notifiy when the NSF receives a packet with an incorrect SPI (i.e. not present in the SAD)";
                        leaf state { type ic:ipsec-spi; mandatory "true"; description "SPI number contained in the erroneous IPsec packet"; }
                }

        }/*module ietf-ipsec*/

        <CODE ENDS>



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


   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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