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

I2NSF                                                     R. Marin-Lopez
Internet-Draft                                           G. Lopez-Millan
Intended status: Standards Track                    University of Murcia
Expires: February 6, 2020                           F. Pereniguez-Garcia
                                               University Defense Center
                                                          August 5, 2019


     Software-Defined Networking (SDN)-based IPsec Flow Protection
             draft-ietf-i2nsf-sdn-ipsec-flow-protection-07

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.

   The document focuses on the NSF Facing Interface by providing models
   for configuration and state data 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 February 6, 2020.






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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 . . . . . . . . . . . . . . . . . . . . . . . . .   5
   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. . . . . . . .   7
       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. . . . . . . . . . . . . . . . . . . .  12
       5.3.3.  NAT Traversal . . . . . . . . . . . . . . . . . . . .  12
       5.3.4.  NSF Discovery . . . . . . . . . . . . . . . . . . . .  13
   6.  YANG configuration data models  . . . . . . . . . . . . . . .  13
     6.1.  IKE case model  . . . . . . . . . . . . . . . . . . . . .  14
     6.2.  IKE-less case model . . . . . . . . . . . . . . . . . . .  17
   7.  Use cases examples  . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Host-to-host or gateway-to-gateway under the same
           Security Controller . . . . . . . . . . . . . . . . . . .  20
     7.2.  Host-to-host or gateway-to-gateway under different
           Security Controllers  . . . . . . . . . . . . . . . . . .  24
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  27
     9.1.  IKE case  . . . . . . . . . . . . . . . . . . . . . . . .  28
     9.2.  IKE-less case . . . . . . . . . . . . . . . . . . . . . .  29
     9.3.  YANG modules  . . . . . . . . . . . . . . . . . . . . . .  29
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  31
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  31
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  31
     11.2.  Informative References . . . . . . . . . . . . . . . . .  32



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   Appendix A.  Appendix A: Common YANG model for IKE and IKE-less
                cases  . . . . . . . . . . . . . . . . . . . . . . .  35
   Appendix B.  Appendix B: YANG model for IKE case  . . . . . . . .  48
   Appendix C.  Appendix C: YANG model for IKE-less case . . . . . .  67
   Appendix D.  Example of IKE case, tunnel mode (gateway-to-
                gateway) with X.509 certificate authentication.  . .  77
   Appendix E.  Example of IKE-less case, transport mode (host-to-
                host). . . . . . . . . . . . . . . . . . . . . . . .  81
   Appendix F.  Examples of notifications. . . . . . . . . . . . . .  85
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  86

1.  Introduction

   Software-Defined Networking (SDN) is an architecture that enables
   users to directly program, orchestrate, control and manage network
   resources through software.  The SDN paradigm relocates the control
   of network resources to a dedicated network element, namely SDN
   Controller.  The SDN controller (or Security Controller in the
   context of this document) 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), an 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 such as IPsec SA management 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 the SDN
   paradigm.

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




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   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
       (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 Security 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, the IKE credential and information related with the IKE
   negotiation (e.g.  IKE_SA_INIT).  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).  Examples of the usage
   of these models can found in Appendix D, Appendix E and Appendix F.

   This document considers two typical scenarios to manage autonomously
   IPsec SAs: gateway-to-gateway and host-to-host [RFC6071].  In these
   cases, hosts, 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.  The analysis of the host-to-gateway
   (roadwarrior) scenario is out of scope of this document.

   Finally, 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", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC



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   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],
   [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.  An entity 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 fall 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), Diffie-Hellman (DH) groups, IPsec SAs parameters
      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
      (traffic selectors information), inbound and outboud IPsec SAs,
      etc.

   o  Security Associations Database (SAD).  It includes information
      about IPsec SAs, such as SPI, destination addresses,




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      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.  It is
      used when the NSF deploys IKE implementation (IKE case).

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 (SA) 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, depending on
   whether the NSF ships an IKEv2 implementation or not: IKE case and
   IKE-less case.

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 IPsec connection information (determining which nodes need
   to start an IKE/IPsec session, deriving and delivering IKE
   Credentials such as a pre-shared key, certificates, etc.), and
   applying other IKE configuration parameters (e.g.  cryptographic
   algorithms for establishing an IKE SA) 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 these 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 NSFs.  In order to support this
   capability in IKE case, the following interface requirements need to
   be met:

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

   o  In scenarios where multiple Security 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 NSFs.  That
      is, the may need to agree on whether IKEv2 authentication will be
      based on raw public keys, pre-shared keys, etc.  In case of using
      pre-shared keys they will have to agree in the PSK.

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




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   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 these requirements into SPD and SAD
   entries, which are installed in the NSF.  PAD entries are not
   required since there is no IKEv2 in the NSF.

5.2.1.  Interface Requirements for IKE-less case

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

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





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   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 the same key.

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

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

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

   o  NAT Traversal discovery and management.

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

   o  IPsec SA's SPI random generation.

   o  Cryptographic algorithm/s selection.

   o  Usage of extended sequence numbers.

   o  Establishment of proper traffic selectors.

5.3.  IKE case vs IKE-less case

   In principle, IKE case is 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 internal interface so that
   the IKE configuration sent by the Security Controller can be enforced
   in runtime.

   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 and managing
   IPsec SAs is shifted to the Security Controller since IKEv2 is not in
   the NSF.  As a consequence, this may result in a more complex
   implementation in the controller side in comparison with IKE case.
   For example, the Security Controller have to deal with the latency



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   existing in the path between the Security Controller and the NSF in
   order to solve tasks such as, rekey or creation and installation of
   new IPsec SAs.  However, this is not specific to our contribution but
   a general aspect in any SDN-based network.  In summary, this overload
   may create some scalability and performance issues when the number of
   NSFs is high.

   Nevertheless, literature around SDN-based network management using a
   centralized Security Controller is aware about scalability and
   performance issues and solutions have been already provided and
   discussed (e.g.  hierarchical Security Controllers; having multiple
   replicated Security Controllers, dedicated high-speed management
   networks, etc).  In the context of SDN-based IPsec management, one
   way to reduce the latency and alleviate some performance issues can
   be the installation of the IPsec policies and IPsec SAs at the same
   time (proactive mode, as described in Section 7.1) instead of waiting
   for notifications (e.g. a notification sadb-acquire when a new IPsec
   SA is required) to proceed with the IPsec SA installations (reactive
   mode).  Another way to reduce the overhead and the potential
   scalability and performance issues in the Security Controller is to
   apply the 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 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 rekey mechanism is further described in
   [I-D.carrel-ipsecme-controller-ike].

   In terms of security, IKE case provides better security properties
   than IKE-less case, as we discuss in section Section 9.  The main
   reason is that the NSFs are generating the session keys and not the
   Security Controller.

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.  Therefore, connections
   will live unless something different is required by the administrator
   or the Security Controller detects something wrong.

   Traditionally, during a rekey process of the IPSec SA using IKE, a
   bundle of inbound and outbound IPsec SAs is taken into account from
   the perspective of one of the NSFs.  For example, if the inbound
   IPsec SA expires both the inbound and outbound IPsec SA are rekeyed
   at the same time in that NSF.  However, when IKE is not used, we have



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   followed a different approach to avoid any packet loss during rekey:
   the Security Controller installs first the new inbound SAs in both
   NSFs and then, the outbound IPsec SAs.

   In other words, for the 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 NSFs A and B, let
   assume that SPIa1 identifies the inbound IPsec SA in A, and SPIb1 the
   inbound IPsec SA in B.  The rekeying process will take the following
   steps:

   1.  The Security Controller chooses two random values as SPI for the
       new inbound IPsec SAs: for example, SPIa2 for A and SPIb2 for B.
       These numbers MUST NOT be in conflict with any IPsec SA in A or
       B.  Then, the Security Controller creates an inbound IPsec SA
       with SPIa2 in A and another inbound IPsec SA in B with SPIb2.  It
       can send this information simultaneously to A and B.

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

   3.  Once the Security Controller receives confirmation from A and B
       that the outbound IPsec SAs have been installed, the Security
       Controller, in parallel, deletes the old IPsec SAs from A
       (inbound SPIa1 and outbound SPIb1) and B (outbound SPIa1 and
       inbound SPIb1).

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

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



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

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 the 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.  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 it will delete the old IPsec SAs on the non-failed
   nodes, established with the failed node (step 1).  This prevents the
   non-failed nodes from leaking plaintext.  If the affected node comes
   to live, the Security Controller will configure the new inbound IPsec
   SAs between the affected node and all the nodes it was talking to
   (step 2).  After these inbound IPsec SAs have been established, the
   Security Controller can configure the outbound IPsec SAs in parallel
   (step 3).

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

5.3.3.  NAT Traversal

   In the IKE case, IKEv2 already provides a mechanism to detect whether
   some of the peers or both are located behind a NAT.  If there is a
   NAT network configured between two peers, it is required to activate



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   the usage of UDP or TCP/TLS encapsulation for ESP packets ([RFC3948],
   [RFC8229]).  Note that the usage of IPsec transport mode when NAT is
   required MUST NOT be used in this specification.

   On the contrary, the 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 under its control.  This view is built
   either requesting information to the NSFs under its control, or
   because these NSFs inform 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
   [RFC8512] a data model for NAT management.  The Security Controller
   can use this NETCONF module with a NSF to collect NAT information or
   even configure a NAT network.  In any case, if this NETCONF module is
   not available in the NSF and the Security Controller does not have a
   mechanism to know whether a host is behind a NAT or not, then the IKE
   case should be the right choice and not the IKE-less case.

5.3.4.  NSF Discovery

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

   Either during this registration process or when the NSF connects with
   the Security Controller, the Security Controller MUST discover
   certain capabilities of this NSF, such as what is the cryptographic
   suite supported, authentication method, the support of the IKE case
   or the IKE-less case, etc.  This discovery process is out of the
   scope of this document.

6.  YANG configuration data models

   In order to support the IKE and IKE-less cases we have modeled the
   different parameters and values that must be configured to manage
   IPsec SAs.  Specifically, 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),



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   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, 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 [strongswan] or Libreswan
   [libreswan].

   The definition of the PAD model has been extracted from the
   specification in section 4.4.3 in [RFC4301] (NOTE: We have observed
   that many implementations integrate PAD configuration as part of the
   IKEv2 configuration).



   module: ietf-ipsec-ike
   +--rw ipsec-ike
     +--rw pad
     |  +--rw pad-entry* [name]
     |     +--rw name                           string
     |     +--rw (identity)
     |     |  +--:(ipv4-address)
     |     |  |  +--rw ipv4-address?            inet:ipv4-address
     |     |  +--:(ipv6-address)
     |     |  |  +--rw ipv6-address?            inet:ipv6-address
     |     |  +--:(fqdn-string)
     |     |  |  +--rw fqdn-string?             inet:domain-name
     |     |  +--:(rfc822-address-string)
     |     |  |  +--rw rfc822-address-string?   string
     |     |  +--:(dnx509)
     |     |  |  +--rw dnx509?                  string
     |     |  +--:(gnx509)
     |     |  |  +--rw gnx509?                  string
     |     |  +--:(id-key)
     |     |  |  +--rw id-key?                  string
     |     |  +--:(id-null)
     |     |     +--rw id-null?                 empty
     |     +--rw auth-protocol?                 auth-protocol-type
     |     +--rw peer-authentication
     |        +--rw auth-method?                auth-method-type
     |        +--rw eap-method
     |        |  +--rw eap-type                 uint8
     |        +--rw pre-shared



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     |        |  +--rw secret?                  yang:hex-string
     |        +--rw digital-signature
     |           +--rw ds-algorithm?            uint8
     |           +--rw (public-key)
     |           |  +--:(raw-public-key)
     |           |  |  +--rw raw-public-key?   binary
     |           |  +--:(cert-data)
     |           |     +--rw cert-data?        ct:x509
     |           +--rw private-key?            binary
     |           +--rw ca-data*                ct:x509
     |           +--rw crl-data?               ct:crl
     |           +--rw crl-uri?                inet:uri
     |           +--rw oscp-uri?               inet:uri
     +--rw conn-entry* [name]
     |  +--rw name                                 string
     |  +--rw autostartup?                         autostartup-type
     |  +--rw initial-contact?                     boolean
     |  +--rw version?                             auth-protocol-type
     |  +--rw fragmentation?                       boolean
     |  +--rw ike-sa-lifetime-soft
     |  |  +--rw rekey-time?    uint32
     |  |  +--rw reauth-time?   uint32
     |  +--rw ike-sa-lifetime-hard
     |  |  +--rw over-time?   uint32
     |  +--rw authalg*  ic:integrity-algorithm-type
     |  +--rw encalg*   ic:encryption-algorithm-type
     |  +--rw dh-group?                            pfs-group
     |  +--rw half-open-ike-sa-timer?              uint32
     |  +--rw half-open-ike-sa-cookie-threshold?   uint32
     |  +--rw local
     |  |  +--rw local-pad-entry-name?   string
     |  +--rw remote
     |  |  +--rw remote-pad-entry-name?   string
     |  +--rw encapsulation-type
     |  |  +--rw espencap?   esp-encap
     |  |  +--rw sport?      inet:port-number
     |  |  +--rw dport?      inet:port-number
     |  |  +--rw oaddr*      inet:ip-address
     |  +--rw spd
     |  |  +--rw spd-entry* [name]
     |  |    +--rw name                   string
     |  |    +--rw ipsec-policy-config
     |  |      +--rw anti-replay-window?   uint64
     |  |      +--rw traffic-selector
     |  |      |  +--rw local-subnet      inet:ip-prefix
     |  |      |  +--rw remote-subnet     inet:ip-prefix
     |  |      |  +--rw inner-protocol?   ipsec-inner-protocol
     |  |      |  +--rw local-ports* [start end]



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     |  |      |  |  +--rw start          inet:port-number
     |  |      |  |  +--rw end            inet:port-number
     |  |      |  +--rw remote-ports* [start end]
     |  |      |     +--rw start          inet:port-number
     |  |      |     +--rw end            inet:port-number
     |  |      +--rw processing-info
     |  |      |  +--rw action?         ipsec-spd-action
     |  |      |  +--rw ipsec-sa-cfg
     |  |      |    +--rw pfp-flag?              boolean
     |  |      |    +--rw ext-seq-num?           boolean
     |  |      |    +--rw seq-overflow?          boolean
     |  |      |    +--rw stateful-frag-check?   boolean
     |  |      |    +--rw mode?                  ipsec-mode
     |  |      |    +--rw protocol-parameters? ipsec-protocol-parameters
     |  |      |    +--rw esp-algorithms
     |  |      |    |  +--rw integrity*  integrity-algorithm-type
     |  |      |    |  +--rw encryption* encryption-algorithm-type
     |  |      |    |  +--rw tfc-pad?      boolean
     |  |      |    +--rw tunnel
     |  |      |       +--rw local           inet:ip-address
     |  |      |       +--rw remote          inet:ip-address
     |  |      |       +--rw df-bit?         enumeration
     |  |      |       +--rw bypass-dscp?    boolean
     |  |      |       +--rw dscp-mapping?   yang:hex-string
     |  |      |       +--rw ecn?            boolean
     |  |      +--rw spd-mark
     |  |         +--rw mark?   uint32
     |  |         +--rw mask?   yang:hex-string
     |  +--rw child-sa-info
     |  |  +--rw pfs-groups*               pfs-group
     |  |  +--rw child-sa-lifetime-soft
     |  |  |  +--rw time?      uint32
     |  |  |  +--rw bytes?     uint32
     |  |  |  +--rw packets?   uint32
     |  |  |  +--rw idle?      uint32
     |  |  |  +--rw action?    ic:lifetime-action
     |  |  +--rw child-sa-lifetime-hard
     |  |     +--rw time?      uint32
     |  |     +--rw bytes?     uint32
     |  |     +--rw packets?   uint32
     |  |     +--rw idle?      uint32
     |  +--ro state
     |     +--ro initiator?             boolean
     |     +--ro initiator-ikesa-spi?   ike-spi
     |     +--ro responder-ikesa-spi?   ike-spi
     |     +--ro nat-local?             boolean
     |     +--ro nat-remote?            boolean
     |     +--ro encapsulation-type



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     |     |  +--ro espencap?   esp-encap
     |     |  +--ro sport?      inet:port-number
     |     |  +--ro dport?      inet:port-number
     |     |  +--ro oaddr*      inet:ip-address
     |     +--ro established?           uint64
     |     +--ro current-rekey-time?    uint64
     |     +--ro current-reauth-time?   uint64
     +--ro number-ike-sas
        +--ro total?               uint64
        +--ro half-open?           uint64
        +--ro half-open-cookies?   uint64


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

6.2.  IKE-less case model

   For this case, the definition of the SPD model has been mainly
   extracted from the specification in section 4.4.1 and Appendix D in
   [RFC4301], though with some simplications.  For example, each IPsec
   policy (spd-entry) contains one traffic selector, instead a list of
   them.  The reason is that we have observed real kernel
   implementations only admit a traffic selector per IPsec policy.

   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 allows to associate an IPsec SA with its corresponding
   policy through the specific traffic selector but also an identifier
   (reqid).

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


   module: ietf-ipsec-ikeless
   +--rw ipsec-ikeless
    +--rw spd
    |  +--rw spd-entry* [name]
    |     +--rw name                   string
    |     +--rw direction?             ic:ipsec-traffic-direction
    |     +--rw reqid?                 uint64
    |     +--rw ipsec-policy-config
    |        +--rw anti-replay-window?   uint64
    |        +--rw traffic-selector
    |        |  +--rw local-subnet      inet:ip-prefix
    |        |  +--rw remote-subnet     inet:ip-prefix



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    |        |  +--rw inner-protocol?   ipsec-inner-protocol
    |        |  +--rw local-ports* [start end]
    |        |  |  +--rw start          inet:port-number
    |        |  |  +--rw end            inet:port-number
    |        |  +--rw remote-ports* [start end]
    |        |     +--rw start          inet:port-number
    |        |     +--rw end            inet:port-number
    |        +--rw processing-info
    |        |  +--rw action?         ipsec-spd-action
    |        |  +--rw ipsec-sa-cfg
    |        |     +--rw pfp-flag?              boolean
    |        |     +--rw ext-seq-num?           boolean
    |        |     +--rw seq-overflow?          boolean
    |        |     +--rw stateful-frag-check?   boolean
    |        |     +--rw mode?                  ipsec-mode
    |        |     +--rw protocol-parameters?
    |        |     +--rw esp-algorithms
    |        |     |  +--rw integrity*    integrity-algorithm-type
    |        |     |  +--rw encryption*  encryption-algorithm-type
    |        |     |  +--rw tfc-pad?      boolean
    |        |     +--rw tunnel
    |        |        +--rw local           inet:ip-address
    |        |        +--rw remote          inet:ip-address
    |        |        +--rw df-bit?         enumeration
    |        |        +--rw bypass-dscp?    boolean
    |        |        +--rw dscp-mapping?   yang:hex-string
    |        |        +--rw ecn?            boolean
    |        +--rw spd-mark
    |           +--rw mark?   uint32
    |           +--rw mask?   yang:hex-string
    +--rw sad
     +--rw sad-entry* [name]
       +--rw name               string
       +--rw reqid?             uint64
       +--rw ipsec-sa-config
       |  +--rw spi                    uint32
       |  +--rw ext-seq-num?           boolean
       |  +--rw seq-number-counter?    uint64
       |  +--rw seq-overflow?          boolean
       |  +--rw anti-replay-window?    uint32
       |  +--rw traffic-selector
       |  |  +--rw local-subnet       inet:ip-prefix
       |  |  +--rw remote-subnet      inet:ip-prefix
       |  |  +--rw inner-protocol?    ipsec-inner-protocol
       |  |  +--rw local-ports*       [start end]
       |  |  |  +--rw start           inet:port-number
       |  |  |  +--rw end             inet:port-number
       |  |  +--rw remote-ports* [start end]



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       |  |     +--rw start           inet:port-number
       |  |     +--rw end             inet:port-number
       |  +--rw protocol-parameters?  ic:ipsec-protocol-parameters
       |  +--rw mode?                 ic:ipsec-mode
       |  +--rw esp-sa
       |  |  +--rw encryption
       |  |  |  +--rw encryption-algorithm? ic:encryption-algorithm-type
       |  |  |  +--rw key?                    yang:hex-string
       |  |  |  +--rw iv?                     yang:hex-string
       |  |  +--rw integrity
       |  |     +--rw integrity-algorithm? ic:integrity-algorithm-type
       |  |     +--rw key?                   yang:hex-string
       |  +--rw sa-lifetime-hard
       |  |  +--rw time?      uint32
       |  |  +--rw bytes?     uint32
       |  |  +--rw packets?   uint32
       |  |  +--rw idle?      uint32
       |  +--rw sa-lifetime-soft
       |  |  +--rw time?      uint32
       |  |  +--rw bytes?     uint32
       |  |  +--rw packets?   uint32
       |  |  +--rw idle?      uint32
       |  |  +--rw action?    ic:lifetime-action
       |  +--rw tunnel
       |  |  +--rw local           inet:ip-address
       |  |  +--rw remote          inet:ip-address
       |  |  +--rw df-bit?         enumeration
       |  |  +--rw bypass-dscp?    boolean
       |  |  +--rw dscp-mapping?   yang:hex-string
       |  |  +--rw ecn?            boolean
       |  +--rw encapsulation-type
       |     +--rw espencap?   esp-encap
       |     +--rw sport?      inet:port-number
       |     +--rw dport?      inet:port-number
       |     +--rw oaddr*      inet:ip-address
       +--ro ipsec-sa-state
          +--ro sa-lifetime-current
          |  +--ro time?      uint32
          |  +--ro bytes?     uint32
          |  +--ro packets?   uint32
          |  +--ro idle?      uint32
          +--ro replay-stats
             +--ro replay-window?        uint64
             +--ro packet-dropped?       uint64
             +--ro failed?               uint32
             +--ro seq-number-counter?   uint64

    notifications:



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


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

7.  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 Security
      Controller









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

        Figure 3: Host-to-host / gateway-to-gateway single Security
                       Controller for the IKE case.

   Figure 3 describes the IKE case:

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

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

   3.  The Security Controller inserts an IKEv2 configuration that
       includes the SPD and PAD entries in both NSF A and NSF B.  If
       some of operations with NSF A and NSF B fail the Security
       Controller will stop the process and perform a rollback operation
       by deleting any IKEv2, SPD and PAD configuration that had been
       successfully installed in NSF A or B.

   4.  If the previous step is successful, the flow is protected by
       means of 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
                  +------------------+       +------------------+
                  |    NSF A         |<=====>|   NSF B          |
                  |IPsec(SPD/SAD)    |   4)  |IPsec(SPD/SAD)    |
                  +------------------+       +------------------+

        Figure 4: Host-to-host / gateway-to-gateway single Security
                       Controller for IKE-less case.

   In the 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 Security Controller does not run any IKEv2
   implementation (neither the NSFs), 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 Security
   Controller.

   Figure 4 describes the IKE-less case, when a data packet needs to be
   protected in the path between the NSF A and NSF B:

   1.  The administrator establishes the flow-based security policies,
       and 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 these entries in both NSF A and
       NSF B IPsec databases (SPD and SAD).  The following text
       describes how this happens between two NSFs A and B:




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

       *  Once the Security Controller receives confirmation from NSF A
          and NSF B, the controller knows that the IPsec SAs are
          correctly installed and ready.

       If some of the operations described above fails (e.g. the NSF A
       reports an error when the Security Controller is trying to
       install the SPD entry, the new inbound and outbound IPsec SAs)
       the Security Controller must perform rollback operations by
       deleting any new inbound or outbound SA and SPD entry that had
       been successfully installed in any of the NSFs (e.g NSF B) and
       stop the process (NOTE: the Security Controller may retry several
       times before giving up).  Other alternative to this operation is:
       the Security Controller sends first the IPsec policies and new
       inbound IPsec SAs to A and B and once it obtains a successful
       confirmation of these operations from NSF A and NSF B, it
       proceeds with installing to the new outbound IPsec SAs.  However,
       this may increase the latency to complete the process.  As an
       advantage, no traffic is sent over the network until the IPsec
       SAs are completely operative.  In any case other alternatives may
       be possible.  Finally, it is worth mentioning that the Security
       Controller associates a lifetime to the new 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.

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

   Instead of installing IPsec policies in the SPD and IPsec SAs in the
   SAD in step 3 (proactive mode), it is also possible that the Security
   Controller only installs the SPD entries in step 3 (reactive mode).
   In such a case, when a data packet requires to be protected with
   IPsec, the NSF that saw first the data packet will send a sadb-
   acquire notification that informs the Security Controller that needs
   SAD entries with the IPsec SAs to process the data packet.  In such
   as reactive mode, since IPsec policies are already installed in the
   SPD, the Security Controller installs first the new IPsec SAs in NSF
   A and B with the operations described in step 3 but without sending
   any IPsec policies.  Again, if some of the operations installing the



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   new inbound/outbound IPsec SAs fail, the Security Controller stops
   the process and performs a rollback operation by deleting any new
   inbound/outbound SAs that had been successfully installed.

   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 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 cases), this system has various
   advantages:

   1.  It allows to create IPsec SAs among two NSFs, based only on the
       application of 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.  Any NSF deployed in the system does not need manual
       configuration, 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.  NSF A and NSF B) 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
              +--------------------+          +--------------------+
              |    NSF A            |<=======>|   NSF B            |
              |IKEv2/IPsec(SPD/PAD)|          |IKEv2/IPsec(SPD/PAD)|
              +--------------------+  (5)     +--------------------+

         Figure 5: Different Security Controllers in the 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 NSF A and NSF B, but the NSF B 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,
       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)       +--------------+
                  |    NSF A     |<==============>|    NSF B     |
                  |IPsec(SPD/SAD)|                |IPsec(SPD/SAD)|
                  +--------------+                +--------------+

      Figure 6: Different Security Controllers in the IKE-less case.

   Figure 6 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 NSF B
       and NSF B MUST be protected.  Nevertheless, it notices that NSF B
       is under the control of another Security Controller B, 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 the 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.  IANA Considerations

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





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        URI: urn:ietf:params:xml:ns:yang:ietf-ipsec-common
        Registrant Contact: The I2NSF WG of the IETF.
        XML: N/A, the requested URI is an XML namespace.

        URI: urn:ietf:params:xml:ns:yang:ietf-ipsec-ike
        Registrant Contact: The I2NSF WG of the IETF.
        XML: N/A, the requested URI is an XML namespace.

        URI: urn:ietf:params:xml:ns:yang:ietf-ipsec-ikeless
        Registrant Contact: The I2NSF WG of the IETF.
        XML: N/A, the requested URI is an XML namespace.

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

        Name:         ietf-ipsec-common
        Namespace:    urn:ietf:params:xml:ns:yang:ietf-ipsec-common
        Prefix:       ic
        Reference:    RFC XXXX

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

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

9.  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 (cryptographic keys,
   configuration parameter, etc...) exchanged between these entities.
   For example, when 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, if encryption is mandatory for all traffic of a
   NSF, its default policy MUST be to drop (DISCARD) packets to prevent
   cleartext packet leaks.  This default policy MUST be in the startup



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   configuration datastore in the NSF before the NSF contacts with the
   Security Controller.  Moreover, the startup configuration datastore
   MUST be pre-configured with the required ALLOW policies that allow to
   communicate the NSF with the Security Controller once the NSF is
   deployed.  This pre-configuration step is not carried out by the
   Security Controller but by some other entity before the NSF
   deployment.  In this manner, when the NSF starts/reboots, it will
   always apply first the configuration in the startup configuration
   before contacting the Security Controller.

   Finally, we have divided this section in two parts in order to
   analyze different security considerations for both cases: NSF with
   IKEv2 (IKE case) and NSF without IKEv2 (IKE-less case).  In general,
   the Security Controller, as typically in the SDN paradigm, is a
   target for different type of attacks.  Thus, the Security Controller
   is a key entity in the infrastructure and MUST be protected
   accordingly.  In particular, 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
   case the attack occurs.  The impact is different depending on the IKE
   case or IKE-less case.

9.1.  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 MUST NOT 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
   to return always the same value (i.e. all 0s) if a read operation is
   carried out.  If the attacker has access to the Security Controller
   during the period of time that key material is generated, it might
   have access to the key material.  Since these values are used during
   NSF authentication in IKEv2, it may impersonate the affected NSFs.
   Several recommendations are important.  If PSK authentication is used
   in IKEv2, the Security Controller MUST remove the PSK immediately
   after generating and distributing it.  Moreover, the PSK MUST have a
   proper length (e.g.  minimum 128 bit length) and strength.  When
   public/private keys are used, the Security Controller MAY generate
   both public key and private key.  In such a case, the Security
   Controller MUST remove the associated private key immediately after
   distributing them to the NSFs.  Alternatively, the NSF could generate
   the private key and export only the public key to the Security
   Controller.  If certificates are used, the NSF MAY generate the



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   private key and exports the public key for certification to the
   Security Controller.  How the NSF generates these cryptographic
   material (public key/private keys) and export the public key, or it
   is instructed to do so, it is out of the scope of this document.

9.2.  IKE-less case

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

9.3.  YANG modules

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

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

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

   The YANG modules describe configuration data for the IKE case (ietf-
   ipsec-ike) and IKE-less case (ietf-ipsec-ikeless).  There is a common
   module (ietf-ipsec-common) used in both cases.

   For the IKE case (ietf-ipsec-ike):



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

   For the IKE-less case (ietf-ipsec-ikeless):

         /ipsec-ikeless: The entire container in this module is
         sensitive to write operations.  An attacker may add/modify/
         delete any IPsec policies (e.g. by allowing leaking of data
         traffic by changing to a allow policy) in the /ipsec-ikeless/
         spd container, and add/modify/delete any IPsec SAs between two
         NSF by means of /ipsec-ikeless/sad container and, in general
         changing any IPsec SAs and IPsec policies between any NSF.

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

   For the IKE case (ietf-ipsec-ike):

         /ipsec-ike/pad: This container includes sensitive information
         to read operations.  This information should never be returned
         to a client.  For example, cryptographic material configured in
         the NSFs: peer-authentication/pre-shared/secret and peer-
         authentication/digital-signature/private-key are already
         protected by the NACM extension "default-deny-all" in this
         document.

   For the IKE-less case (ietf-ipsec-ikeless):

         /ipsec-ikeless/sad/ipsec-sa-config/esp-sa: This container
         includes symmetric keys for the IPsec SAs.  For example,
         encryption/key contains a ESP encryption key value and
         encryption/iv contains a initialization vector value.
         Similarly, integrity/key has ESP integrity key value.  Those
         values must not be read by anyone and are protected by the NACM
         extension "default-deny-all" in this document.







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10.  Acknowledgements

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

11.  References

11.1.  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>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [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>.

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

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



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

11.2.  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-terminology]
              Hares, S., Strassner, J., Lopez, D., Xia, L., and H.
              Birkholz, "Interface to Network Security Functions (I2NSF)
              Terminology", draft-ietf-i2nsf-terminology-08 (work in
              progress), July 2019.

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

   [ITU-T.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.

   [libreswan]
              The Libreswan Project, "Libreswan VPN software", August
              2019.

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

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

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





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   [RFC2367]  McDonald, D., Metz, C., and B. Phan, "PF_KEY Key
              Management API, Version 2", RFC 2367,
              DOI 10.17487/RFC2367, July 1998,
              <https://www.rfc-editor.org/info/rfc2367>.

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

   [RFC3948]  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
              Stenberg, "UDP Encapsulation of IPsec ESP Packets",
              RFC 3948, DOI 10.17487/RFC3948, January 2005,
              <https://www.rfc-editor.org/info/rfc3948>.

   [RFC6071]  Frankel, S. and S. Krishnan, "IP Security (IPsec) and
              Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
              DOI 10.17487/RFC6071, February 2011,
              <https://www.rfc-editor.org/info/rfc6071>.

   [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>.

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

   [RFC8229]  Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation
              of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229,
              August 2017, <https://www.rfc-editor.org/info/rfc8229>.








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   [RFC8512]  Boucadair, M., Ed., Sivakumar, S., Jacquenet, C.,
              Vinapamula, S., and Q. Wu, "A YANG Module for Network
              Address Translation (NAT) and Network Prefix Translation
              (NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019,
              <https://www.rfc-editor.org/info/rfc8512>.

   [strongswan]
              CESNET, "StrongSwan: the OpenSource IPsec-based VPN
              Solution", August 2019.










































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



       <CODE BEGINS> file "ietf-ipsec-common@2019-08-05.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; }

           organization "IETF I2NSF Working Group";

           contact
           "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/about/>
            WG List: <mailto:i2nsf@ietf.org>

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

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

           Author: Fernando Pereniguez-Garcia
                   <mailto:fernando.pereniguez@cud.upct.es>
           ";

           description
               "Common Data model for the IKE and IKE-less cases
                defined by the SDN-based IPsec flow protection service.

               Copyright (c) 2019 IETF Trust and the persons
               identified as authors of the code.  All rights reserved.
               Redistribution and use in source and binary forms, with
               or without modification, is permitted pursuant to, and
               subject to the license terms contained in, the
               Simplified BSD License set forth in Section 4.c of the
               IETF Trust's Legal Provisions Relating to IETF Documents
               (https://trustee.ietf.org/license-info).

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

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



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               'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this
               document are to be interpreted as described in BCP 14
               (RFC 2119) (RFC 8174) when, and only when, they appear
               in all capitals, as shown here.";

           revision "2019-08-05" {
               description "Revision 06";
               reference "RFC XXXX: YANG Groupings and typedef
                          for IKE and IKE-less case";
           }

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

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

           typedef ipsec-mode {



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               type enumeration {
                   enum transport {
                       description
                           "IPsec transport mode. No Network Address
                            Translation (NAT) support.";
                   }
                   enum tunnel {
                       description "IPsec tunnel mode.";
                   }
               }
               description
                   "Type definition of IPsec mode: transport or
                    tunnel.";
               reference
                   "Section 3.2 in RFC 4301.";
           }

           typedef esp-encap {
               type enumeration {
                   enum espintcp {
                       description
                           "ESP in TCP encapsulation.";
                       reference
                           "RFC 8229 - TCP Encapsulation of IKE and
                            IPsec Packets.";
                   }
                   enum espintls {
                       description
                           "ESP in TCP encapsulation using TLS.";
                       reference
                           "RFC 8229 - TCP Encapsulation of IKE and
                            IPsec Packets.";
                   }
                   enum espinudp {
                       description
                           "ESP in UDP encapsulation.";
                       reference
                           "RFC 3948 - UDP Encapsulation of IPsec ESP
                           Packets.";
                   }
                   enum none {
                       description
                           "NOT ESP encapsulation.";
                   }
               }
               description
                   "Types of ESP encapsulation when Network Address
                    Translation (NAT) is present between two NSFs.";



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               reference
                   "RFC 8229 - TCP Encapsulation of IKE and IPsec
                    Packets and RFC 3948 - UDP Encapsulation of IPsec
                    ESP Packets.";
           }

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

           }

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

           typedef ipsec-traffic-direction {



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               type enumeration {
                   enum inbound {
                       description "Inbound traffic.";
                   }
                   enum outbound {
                       description "Outbound traffic.";
                   }
               }
               description
                   "IPsec traffic direction is defined in two
                    directions: inbound and outbound. From a NSF
                    perspective inbound means the traffic that enters
                    the NSF and outbound is the traffic that is sent
                    from the NSF.";
               reference
                   "Section 5 in RFC 4301.";
           }

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

           typedef ipsec-inner-protocol {
               type union {
                   type uint8;
                   type enumeration {
                       enum any {



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                           value 256;
                           description
                               "Any IP protocol number value.";
                       }
                   }
               }
               default any;
               description
                   "IPsec protection can be applied to specific IP
                    traffic and layer 4 traffic (TCP, UDP, SCTP, etc.)
                    or ANY protocol in the IP packet payload. We
                    specify the IP protocol number with an uint8 or
                    ANY defining an enumerate with value 256 to
                    indicate the protocol number.";
               reference
                   "Section 4.4.1.1 in RFC 4301.
                    IANA Registry - Protocol Numbers.";
           }

           grouping encap {
               description
                   "This group of nodes allows to define the type of
                    encapsulation in case NAT traversal is
                    required and port information.";
               leaf espencap {
                   type esp-encap;
                   description
                       "ESP in TCP, ESP in UDP or ESP in TLS.";
               }
               leaf sport {
                   type inet:port-number;
                   default 4500;
                   description
                       "Encapsulation source port.";
               }
               leaf dport {
                   type inet:port-number;
                   default 4500;
                   description
                       "Encapsulation destination port.";
               }

               leaf-list oaddr {
                   type inet:ip-address;
                   description
                       "If required, this is the original address that
                        was used before NAT was applied over the Packet.
                        ";



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               }
               reference
                   "RFC 3947 and RFC 8229.";
           }

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



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           }

           grouping port-range  {
               description
                   "This grouping defines a port range, such as
                    expressed in RFC 4301. For example: 1500 (Start
                    Port Number)-1600 (End Port Number). A port range
                    is used in the Traffic Selector.";

               leaf start {
                   type inet:port-number;
                   description
                       "Start port number.";
               }
               leaf end {
                   type inet:port-number;
                   description
                       "End port number.";
               }
               reference "Section 4.4.1.2 in RFC 4301.";
           }

           grouping tunnel-grouping {
               description
                   "The parameters required to define the IP tunnel
                    endpoints when IPsec SA requires tunnel mode. The
                    tunnel is defined by two endpoints: the local IP
                    address and the remote IP address.";

               leaf local {
                   type inet:ip-address;
                   mandatory true;
                   description
                       "Local IP address' tunnel endpoint.";
               }
               leaf remote {
                   type inet:ip-address;
                   mandatory true;
                   description
                       "Remote IP address' tunnel endpoint.";
               }
               leaf df-bit {
                   type enumeration {
                       enum clear {
                           description
                               "Disable the DF (Don't Fragment) bit
                                from the outer header. This is the
                                default value.";



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                       }
                       enum set {
                           description
                               "Enable the DF bit in the outer header.";
                       }
                       enum copy {
                           description
                               "Copy the DF bit to the outer header.";
                       }
                   }
                   default clear;
                   description
                       "Allow configuring the DF bit when encapsulating
                        tunnel mode IPsec traffic. RFC 4301 describes
                        three options to handle the DF bit during
                        tunnel encapsulation: clear, set and copy from
                        the inner IP header.";
                   reference
                       "Section 8.1 in RFC 4301.";
               }
               leaf bypass-dscp {
                   type boolean;
                   default true;
                   description
                       "If DSCP (Differentiated Services Code Point)
                        values in the inner header have to be used to
                        select one IPsec SA among several that match
                        the traffic selectors for an outbound packet";
                   reference
                       "Section 4.4.2.1. in RFC 4301.";
               }
               leaf dscp-mapping {
                   type yang:hex-string;
                   description
                       "DSCP values allowed for packets carried over
                        this IPsec SA.";
                   reference
                       "Section 4.4.2.1. in RFC 4301.";
               }
               leaf ecn {
                   type boolean;
                   default false;
                   description
                       "Explicit Congestion Notification (ECN). If true
                        copy CE bits to inner header.";
                   reference
                       "Section 5.1.2 and Annex C in RFC 4301.";
               }



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           }

           grouping selector-grouping {
               description
                   "This grouping contains the definition of a Traffic
                    Selector, which is used in the IPsec policies and
                    IPsec SAs.";

               leaf local-subnet {
                   type inet:ip-prefix;
                   mandatory true;
                   description
                       "Local IP address subnet.";
               }
               leaf remote-subnet {
                   type inet:ip-prefix;
                   mandatory true;
                   description
                       "Remote IP address subnet.";
               }
               leaf inner-protocol {
                   type ipsec-inner-protocol;
                   default any;
                   description
                       "Inner Protocol that is going to be
                       protected with IPsec.";
               }
               list local-ports {
                   key "start end";
                   uses port-range;
                   description
                       "List of local ports. When the inner
                        protocol is ICMP this 16 bit value represents
                        code and type.";
               }
               list remote-ports {
                   key "start end";
                   uses port-range;
                   description
                       "List of remote ports. When the upper layer
                       protocol is ICMP this 16 bit value represents
                       code and type.";
               }
               reference
                   "Section 4.4.1.2 in RFC 4301.";
           }

           grouping ipsec-policy-grouping {



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

               leaf anti-replay-window {
                   type uint64;
                   default 32;
                   description
                       "A 64-bit counter used to determine whether an
                        inbound ESP packet is a replay.";
                   reference
                       "Section 4.4.2.1 in RFC 4301.";
               }
               container traffic-selector {
                   description
                       "Packets are selected for
                        processing actions based on the IP and inner
                        protocol header information, selectors,
                        matched against entries in the SPD.";
                   uses selector-grouping;
                   reference
                       "Section 4.4.4.1 in RFC 4301.";
               }
               container processing-info {
                   description
                       "SPD processing. If the required processing
                        action is protect, it contains the required
                        information to process the packet.";
                   leaf action {
                       type ipsec-spd-action;
                       default discard;
                       description
                           "If bypass or discard, container
                           ipsec-sa-cfg is empty.";
                   }
                   container ipsec-sa-cfg {
                       when "../action = 'protect'";
                       description
                           "IPSec SA configuration included in the SPD
                           entry.";
                       leaf pfp-flag {
                           type boolean;
                           default false;
                           description
                                "Each selector has a Populate From
                                 Packet (PFP) flag. If asserted for a
                                 given selector X, the flag indicates
                                 that the IPSec SA to be created should



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                                 take its value (local IP address,
                                 remote IP address, Next Layer
                                 Protocol, etc.) for X from the value
                                 in the packet. Otherwise, the IPsec SA
                                 should take its value(s) for X from
                                 the value(s) in the SPD entry.";
                       }
                       leaf ext-seq-num {
                           type boolean;
                           default false;
                           description
                                "True if this IPsec SA is using extended
                                 sequence numbers. True 64 bit counter,
                                 False 32 bit.";
                       }
                       leaf seq-overflow {
                           type boolean;
                           default false;
                           description
                               "The flag indicating whether
                               overflow of the sequence number
                               counter should prevent transmission
                               of additional packets on the IPsec
                               SA (false) and, therefore needs to
                               be rekeyed, or whether rollover is
                               permitted (true). If Authenticated
                               Encryption with Associated Data
                               (AEAD) is used this flag MUST be
                               false.";
                       }
                       leaf stateful-frag-check {
                           type boolean;
                           default false;
                           description
                               "Indicates whether (true) or not (false)
                                stateful fragment checking applies to
                                the IPsec SA to be created.";
                       }
                       leaf mode {
                           type ipsec-mode;
                           default transport;
                           description
                               "IPsec SA has to be processed in
                                transport or tunnel mode.";
                       }
                       leaf protocol-parameters {
                           type ipsec-protocol-parameters;
                           default esp;



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                           description
                                "Security protocol of the IPsec SA:
                                Only ESP is supported but it could be
                                extended in the future.";
                       }
                       container esp-algorithms {
                           when "../protocol-parameters = 'esp'";
                           description
                                "Configuration of Encapsulating
                                Security Payload (ESP) parameters and
                                algorithms.";
                           leaf-list integrity {
                               type integrity-algorithm-type;
                               default 0;
                               ordered-by user;
                               description
                                   "Configuration of ESP authentication
                                   based on the specified integrity
                                   algorithm. With AEAD algorithms,
                                   the integrity node is not
                                   used.";
                               reference
                                   "Section 3.2 in RFC 4303.";
                           }
                           leaf-list encryption {
                               type encryption-algorithm-type;
                               default 20;
                               ordered-by user;
                               description
                                   "Configuration of ESP encryption
                                   algorithms. The default value is
                                   20 (ENCR_AES_GCM_16).";
                               reference
                                   "Section 3.2 in RFC 4303.";
                           }
                           leaf tfc-pad {
                               type boolean;
                               default false;
                               description
                                   "If Traffic Flow Confidentiality
                                    (TFC) padding for ESP encryption
                                    can be used (true) or not (false)";
                               reference
                                   "Section 2.7 in RFC 4303.";
                           }
                           reference
                               "RFC 4303.";
                       }



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

       <CODE ENDS>



Appendix B.  Appendix B: YANG model for IKE case




       <CODE BEGINS> file "ietf-ipsec-ike@2019-08-05.yang"



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       module ietf-ipsec-ike {
           yang-version 1.1;
           namespace "urn:ietf:params:xml:ns:yang:ietf-ipsec-ike";
           prefix "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-10:
                   Common YANG Data Types for Cryptography.";
           }

           import ietf-ipsec-common {
               prefix ic;
               reference
                   "RFC XXXX: module ietf-ipsec-common, revision
                    2019-08-05.";
           }

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

           organization "IETF I2NSF Working Group";

           contact
           "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/about/>
            WG List: <mailto:i2nsf@ietf.org>

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

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

           Author: Fernando Pereniguez-Garcia
                   <mailto:fernando.pereniguez@cud.upct.es>
           ";

           description

           "This module contains IPSec IKE case model for the SDN-based



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            IPsec flow protection service. An NSF will implement this
            module.


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

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

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

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

           revision "2019-08-05" {
               description "Revision 6";
               reference
                   "RFC XXXX: YANG model for IKE case.";
           }

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

           typedef autostartup-type {
               type enumeration {
                   enum add {
                       description
                           "IKE/IPsec configuration is only loaded into
                            IKE implementation but IKE/IPsec SA is not
                            started.";
                   }
                   enum on-demand {
                       description



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                           "IKE/IPsec configuration is loaded
                           into IKE implementation. The IPsec policies
                           are transferred to the NSF's kernel but the
                           IPsec SAs are not established immediately.
                           The IKE implementation will negotiate the
                           IPsec SAs when the NSF's kernel requests it
                           (i.e. through an ACQUIRE notification).";
                   }
                   enum start {
                       description "IKE/IPsec configuration is loaded
                       and transferred to the NSF's kernel, and the
                       IKEv2 based IPsec SAs are established
                       immediately without waiting any packet.";
                   }
               }
               description
                   "Different policies to set IPsec SA configuration
                    into NSF's kernel when IKEv2 implementation has
                    started.";
           }



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

           typedef auth-protocol-type {
               type enumeration {
                   enum ikev2 {
                       value 2;
                       description
                           "IKEv2 authentication protocol. It is the
                            only defined right now. An enum is used for
                            further extensibility.";
                   }
               }
               description
                   "IKE authentication protocol version specified in the
                    Peer Authorization Database (PAD). It is defined as
                    enumerate to allow new IKE versions in the



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                    future.";
               reference
                   "RFC 7296.";
           }

           typedef auth-method-type {
               type enumeration {
                   enum pre-shared {
                       description
                           "Select pre-shared key as the
                           authentication method.";
                       reference
                           "RFC 7296.";
                   }
                   enum eap {
                       description
                           "Select EAP as the authentication method.";
                       reference
                           "RFC 7296.";
                   }
                   enum digital-signature {
                       description
                           "Select digital signature method.";
                       reference
                           "RFC 7296 and RFC 7427.";
                   }
                   enum null {
                       description
                           "Null authentication.";
                       reference
                           "RFC 7619.";
                   }

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

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

               container pad {
                   description
                      "Configuration of Peer Authorization Database



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                       (PAD). The PAD contains information about IKE
                       peer (local and remote). Therefore, the Security
                       Controller also stores authentication
                       information for this NSF and can include
                       several entries for the local NSF not only
                       remote peers. Storing local and remote
                       information makes possible to specify that this
                       NSF with identity A will use some particular
                       authentication with remote NSF with identity B
                       and what are the authentication mechanisms
                       allowed to B.";
                   list pad-entry {
                       key "name";
                       ordered-by user;
                       description
                           "Peer Authorization Database (PAD) entry. It
                            is a list of PAD entries ordered by the
                            Security Controller.";
                       leaf name {
                           type string;
                           description
                               "PAD unique name to identify this
                                entry.";
                       }
                       choice identity {
                           mandatory true;
                           description
                               "A particular IKE peer will be
                               identified by one of these identities.
                               This peer can be a remote peer or local
                               peer (this NSF).";
                           reference
                               "Section 4.4.3.1 in RFC 4301.";
                           case ipv4-address{
                               leaf ipv4-address {
                                   type inet:ipv4-address;
                                   description
                                       "Specifies the identity as a
                                        single four (4) octet.";
                               }
                           }
                           case ipv6-address{
                               leaf ipv6-address {
                                   type inet:ipv6-address;
                                   description
                                       "Specifies the identity as a
                                        single sixteen (16) octet IPv6
                                        address. An example is



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                                        2001:DB8:0:0:8:800:200C:417A.";
                               }
                           }
                           case fqdn-string {
                               leaf fqdn-string {
                                   type inet:domain-name;
                                   description
                                       "Specifies the identity as a
                                        Fully-QualifiedDomain Name
                                        (FQDN) string. An example is:
                                        example.com. The string MUST
                                        NOT contain any terminators
                                        (e.g., NULL, CR, etc.).";
                               }
                           }
                           case rfc822-address-string {
                               leaf rfc822-address-string {
                                   type string;
                                   description
                                       "Specifies the identity as a
                                        fully-qualified RFC822 email
                                        address string. An example is,
                                        jsmith@example.com. The string
                                        MUST NOT contain any
                                        terminators e.g., NULL, CR,
                                        etc.).";
                                   reference
                                       "RFC 822.";
                               }
                           }
                           case dnx509 {
                               leaf dnx509 {
                                   type string;
                                   description
                                       "Specifies the identity as a
                                        ASN.1 X.500 Distinguished
                                        Name. An example is
                                        C=US,O=Example
                                        Organisation,CN=John Smith.";
                                   reference
                                       "RFC 2247.";
                               }
                           }
                           case gnx509 {
                               leaf gnx509 {
                                   type string;
                                   description
                                       "ASN.1 X.509 GeneralName. RFC



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                                        3280.";
                               }
                           }
                           case id-key {
                               leaf id-key {
                                   type string;
                                   description
                                       "Opaque octet stream that may be
                                        used to pass vendor-specific
                                        information for proprietary
                                        types of identification.";
                                   reference
                                       "Section 3.5 in RFC 7296.";
                               }
                           }
                           case id-null {
                               leaf id-null {
                                   type empty;
                                   description
                                       "ID_NULL identification used
                                        when IKE identification payload
                                        is not used." ;
                                   reference
                                       "RFC 7619.";
                               }
                           }
                       }
                       leaf auth-protocol {
                           type auth-protocol-type;
                           default ikev2;
                           description
                               "Only IKEv2 is supported right now but
                                other authentication protocols may be
                                supported in the future.";
                       }
                       container peer-authentication {
                           description
                               "This container allows the Security
                                Controller to configure the
                                authentication method (pre-shared key,
                                eap, digitial-signature, null) that
                                will use a particular peer and the
                                credentials, which will depend on the
                                selected authentication method.";
                           leaf auth-method {
                              type auth-method-type;
                              default pre-shared;
                              description



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                                   "Type of authentication method
                                   (pre-shared, eap, digital signature,
                                    null).";
                              reference
                                  "Section 2.15 in RFC 7296.";
                           }
                           container eap-method {
                               when "../auth-method = 'eap'";
                               leaf eap-type {
                                   type uint8;
                                   mandatory true;
                                   description
                                       "EAP method type. This
                                       information provides the
                                       particular EAP method to be
                                       used. Depending on the EAP
                                       method, pre-shared keys or
                                       certificates may be used.";
                               }
                               description
                                   "EAP method description used when
                                   authentication method is 'eap'.";
                               reference
                                   "Section 2.16 in RFC 7296.";
                           }
                           container pre-shared {
                               when
                                   "../auth-method[.='pre-shared' or
                                    .='eap']";
                               leaf secret {
                                   nacm:default-deny-all;
                                   type yang:hex-string;
                                   description
                                       "Pre-shared secret value. The
                                        NSF has to prevent read access
                                        to this value for security
                                        reasons.";
                               }
                               description
                                   "Shared secret value for PSK or
                                    EAP method authentication based on
                                    PSK.";
                           }
                           container digital-signature {
                               when
                                "../auth-method[.='digital-signature'
                               or .='eap']";
                               leaf ds-algorithm {



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                                   type uint8;
                                   description
                                       "The digital signature
                                       algorithm is specified with a
                                       value extracted from the IANA
                                       Registry. Depending on the
                                       algorithm, the following leafs
                                       must contain information. For
                                       example if digital signature
                                       involves a certificate then leaf
                                       'cert-data' and 'private-key'
                                       will contain this information.";
                                   reference
                                       "IKEv2 Authentication Method -
                                        IANA Registry - Internet Key
                                        Exchange Version 2 (IKEv2)
                                        Parameters.";
                               }

                               choice public-key {
                                   mandatory true;
                                   leaf raw-public-key {
                                       type binary;
                                       description
                                         "A binary that contains the
                                         value of the public key.  The
                                         interpretation of the content
                                         is defined by the digital
                                         signature algorithm. For
                                         example, an RSA key is
                                         represented as RSAPublicKey as
                                         defined in RFC 8017, and an
                                         Elliptic Curve Cryptography
                                         (ECC) key is represented
                                         using the 'publicKey'
                                         described in RFC 5915.";
                                   reference
                                         "RFC XXX: Common YANG Data
                                         Types for Cryptography.";
                                   }
                                   leaf cert-data {
                                       type ct:x509;
                                       description
                                           "X.509 certificate data -
                                            PEM4.";
                                       reference
                                           "RFC XXX: Common YANG Data
                                           Types for Cryptography.";



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                                   }
                                   description
                                       "If the Security Controller
                                        knows that the NSF
                                        already owns a private key
                                        associated to this public key
                                        (the NSF generated the pair
                                        public key/private key out of
                                        band), it will only configure
                                        one of the leaf of this
                                        choice. The NSF, based on
                                        the public key value can know
                                        the private key to be used.";
                               }
                               leaf private-key {
                                   nacm:default-deny-all;
                                   type binary;
                                   description
                                       "A binary that contains the
                                        value of the private key. The
                                        interpretation of the content
                                        is defined by the digital
                                        signature algorithm. For
                                        example, an RSA key is
                                        represented as RSAPrivateKey as
                                        defined in RFC 8017, and an
                                        Elliptic Curve Cryptography
                                        (ECC) key is represented as
                                        ECPrivateKey as defined in RFC
                                        5915.";
                                   reference
                                       "RFC XXX: Common YANG Data
                                       Types for Cryptography.";
                               }
                               leaf-list ca-data {
                                   type ct:x509;
                                   description
                                       "List of trusted Certification
                                       Authorities (CA) certificates
                                       encoded using ASN.1
                                       distinguished encoding rules
                                       (DER).";
                                   reference
                                       "RFC XXX: Common YANG Data
                                       Types for Cryptography.";
                               }
                               leaf crl-data {
                                   type ct:crl;



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                                   description
                                      "A CertificateList structure, as
                                       specified in RFC 5280,
                                       encoded using ASN.1
                                       distinguished encoding rules
                                       (DER),as specified in ITU-T
                                       X.690.";
                                   reference
                                       "RFC XXX: Common YANG Data Types
                                        for Cryptography.";
                               }
                               leaf crl-uri  {
                                   type inet:uri;
                                   description
                                       "X.509 CRL certificate URI.";
                               }
                               leaf oscp-uri {
                                   type inet:uri;
                                   description
                                       "OCSP URI.";
                               }
                               description
                                   "Digital Signature container.";

                           } /*container digital-signature*/
                       } /*container peer-authentication*/
                   }
               }

               list conn-entry {
                   key "name";
                   description
                       "IKE peer connection information. This list
                       contains the IKE connection for this peer
                       with other peers. This will be translated in
                       real time by IKE Security Associations
                       established with these nodes.";
                   leaf name {
                       type string;
                       mandatory true;
                       description
                           "Identifier for this connection
                            entry.";
                   }
                   leaf autostartup {
                         type autostartup-type;
                         default add;
                         description



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                             "By-default: Only add configuration
                              without starting the security
                              association.";
                   }
                   leaf initial-contact {
                       type boolean;
                       default false;
                       description
                           "The goal of this value is to deactivate the
                           usage of INITIAL_CONTACT notification
                           (true). If this flag remains to false it
                           means the usage of the INITIAL_CONTACT
                           notification will depend on the IKEv2
                           implementation.";
                   }
                   leaf version {
                       type auth-protocol-type;
                       default ikev2;
                       description
                          "IKE version. Only version 2 is supported
                          so far.";
                   }
                   leaf fragmentation {
                       type boolean;
                       default false;
                       description
                           "Whether or not to enable IKE
                            fragmentation as per RFC 7383 (true or
                            false).";
                       reference
                           "RFC 7383.";
                   }
                   container ike-sa-lifetime-soft {
                       description
                           "IKE SA lifetime soft. Two lifetime values
                            can be configured: either rekey time of the
                            IKE SA or reauth time of the IKE SA. When
                            the rekey lifetime expires a rekey of the
                            IKE SA starts. When reauth lifetime
                            expires a IKE SA reauthentication starts.";
                      leaf rekey-time {
                           type uint32;
                           default 0;
                           description
                               "Time in seconds between each IKE SA
                               rekey.The value 0 means infinite.";
                      }
                      leaf reauth-time {



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                           type uint32;
                           default 0;
                           description
                             "Time in seconds between each IKE SA
                             reauthentication. The value 0 means
                             infinite.";
                      }
                      reference
                          "Section 2.8 in RFC 7296.";
                   }
                   container ike-sa-lifetime-hard {
                       description
                           "Hard IKE SA lifetime. When this
                            time is reached the IKE SA is removed.";
                       leaf over-time {
                           type uint32;
                           default 0;
                           description
                               "Time in seconds before the IKE SA is
                                removed. The value 0 means infinite.";
                       }
                       reference
                           "RFC 7296.";
                   }
                   leaf-list authalg {
                       type ic:integrity-algorithm-type;
                       default 12;
                       ordered-by user;
                       description
                          "Authentication algorithm for establishing
                          the IKE SA. This list is ordered following
                          from the higher priority to lower priority.
                          First node of the list will be the algorithm
                          with higher priority. If this list is empty
                          the default integrity algorithm value assumed
                          is NONE.";
                   }
                   leaf-list encalg {
                       type ic:encryption-algorithm-type;
                       default 12;
                       ordered-by user;
                       description
                          "Encryption or AEAD algorithm for the IKE
                          SAs. This list is ordered following
                          from the higher priority to lower priority.
                          First node of the list will be the algorithm
                          with higher priority. If this list is empty
                          the default encryption value assumed is



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                          NULL.";
                   }
                   leaf dh-group {
                       type pfs-group;
                       default 14;
                       description
                           "Group number for Diffie-Hellman
                           Exponentiation used during IKE_SA_INIT
                           for the IKE SA key exchange.";
                   }
                   leaf half-open-ike-sa-timer {
                       type uint32;
                       description
                           "Set the half-open IKE SA timeout
                            duration.";
                       reference
                           "Section 2 in RFC 7296.";
                   }

                   leaf half-open-ike-sa-cookie-threshold {
                       type uint32;
                       description
                           "Number of half-open IKE SAs that activate
                            the cookie mechanism." ;
                       reference
                           "Section 2.6 in RFC 7296.";
                   }
                   container local {
                       leaf local-pad-entry-name {
                           type string;
                           description
                               "Local peer authentication information.
                                This node points to a specific entry in
                                the PAD where the authorization
                                information about this particular local
                                peer is stored. It MUST match a
                                pad-entry-name.";
                       }
                       description
                           "Local peer authentication information.";
                   }
                   container remote {
                       leaf remote-pad-entry-name {
                           type string;
                           description
                               "Remote peer authentication information.
                                This node points to a specific entry in
                                the PAD where the authorization



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                                information about this particular
                                remote peer is stored. It MUST match a
                                pad-entry-name.";
                       }
                       description
                           "Remote peer authentication information.";
                   }
                   container encapsulation-type
                   {
                       uses ic:encap;
                       description
                           "This container carries configuration
                           information about the source and destination
                           ports of encapsulation that IKE should use
                           and the type of encapsulation that
                           should use when NAT traversal is required.
                           However, this is just a best effort since
                           the IKE implementation may need to use a
                           different encapsulation as
                           described in RFC 8229.";
                       reference
                           "RFC 8229.";
                   }
                   container spd {
                       description
                           "Configuration of the Security Policy
                           Database (SPD). This main information is
                           placed in the grouping
                           ipsec-policy-grouping.";
                       list spd-entry {
                           key "name";
                           ordered-by user;
                           leaf name {
                               type string;
                               mandatory true;
                               description
                                   "SPD entry unique name to identify
                                   the IPsec policy.";
                           }
                           container ipsec-policy-config {
                               description
                                   "This container carries the
                                   configuration of a IPsec policy.";
                               uses ic:ipsec-policy-grouping;
                           }
                           description
                               "List of entries which will constitute
                               the representation of the SPD. Since we



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                               have IKE in this case, it is only
                               required to send a IPsec policy from
                               this NSF where 'local' is this NSF and
                               'remote' the other NSF. The IKE
                               implementation will install IPsec
                               policies in the NSF's kernel in both
                               directions (inbound and outbound) and
                               their corresponding IPsec SAs based on
                               the information in this SPD entry.";
                       }
                       reference
                           "Section 2.9 in RFC 7296.";
                   }
                   container child-sa-info {
                       leaf-list pfs-groups {
                           type pfs-group;
                           default 0;
                           ordered-by user;
                           description
                               "If non-zero, it is required perfect
                                forward secrecy when requesting new
                                IPsec SA. The non-zero value is
                                the required group number. This list is
                                ordered following from the higher
                                priority to lower priority. First node
                                of the list will be the algorithm
                                with higher priority.";
                       }
                       container child-sa-lifetime-soft {
                           description
                               "Soft IPsec SA lifetime soft.
                                After the lifetime the action is
                                defined in this container
                                in the leaf action.";
                           uses ic:lifetime;
                           leaf action {
                               type ic:lifetime-action;
                               default replace;
                               description
                                   "When the lifetime of an IPsec SA
                                    expires an action needs to be
                                    performed over the IPsec SA that
                                    reached the lifetime. There are
                                    three possible options:
                                    terminate-clear, terminate-hold and
                                    replace.";
                           reference
                               "Section 4.5 in RFC 4301 and Section 2.8



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

                       leaf initiator {
                           type boolean;
                           description
                               "It is acting as initiator for this
                                connection.";
                       }
                       leaf initiator-ikesa-spi {
                           type ike-spi;
                           description
                               "Initiator's IKE SA SPI.";
                       }
                       leaf responder-ikesa-spi {
                           type ike-spi;
                           description
                               "Responder's IKE SA SPI.";
                       }
                       leaf nat-local {
                           type boolean;
                           description
                               "True, if local endpoint is behind a
                                NAT.";
                       }
                       leaf nat-remote {
                           type boolean;
                           description
                               "True, if remote endpoint is behind
                               a NAT.";
                       }




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                       container encapsulation-type
                       {
                           uses ic:encap;
                           description
                               "This container provides information
                               about the source and destination
                               ports of encapsulation that IKE is
                               using, and the type of encapsulation
                               when NAT traversal is required.";
                           reference
                               "RFC 8229.";
                       }
                       leaf established {
                           type uint64;
                           description
                               "Seconds since this IKE SA has been
                                established.";
                       }
                       leaf current-rekey-time {
                           type uint64;
                           description
                               "Seconds before IKE SA must be rekeyed.";
                       }
                       leaf current-reauth-time {
                           type uint64;
                           description
                               "Seconds before IKE SA must be
                                re-authenticated.";
                       }
                       description
                           "IKE state data for a particular
                            connection.";
                   } /* ike-sa-state */
               } /* ike-conn-entries */

               container number-ike-sas {
                   config false;
                   leaf total {
                       type uint64;
                       description
                           "Total number of active IKE SAs.";
                   }
                   leaf half-open {
                       type uint64;
                       description
                           "Number of half-open active IKE SAs.";
                   }
                   leaf half-open-cookies {



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                       type uint64;
                       description
                           "Number of half open active IKE SAs with
                            cookie activated.";
                   }
                   description
                       "General information about the IKE SAs. In
                       particular, it provides the current number of
                       IKE SAs.";
               }
           }  /* container ipsec-ike */
       }


       <CODE ENDS>



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





       <CODE BEGINS> file "ietf-ipsec-ikeless@2019-08-05.yang"

       module ietf-ipsec-ikeless {

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

           prefix "ikeless";

           import ietf-yang-types { prefix yang; }

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

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



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           organization "IETF I2NSF Working Group";

           contact
           "WG Web:  <https://datatracker.ietf.org/wg/i2nsf/about/>
            WG List: <mailto:i2nsf@ietf.org>

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

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

           Author: Fernando Pereniguez-Garcia
                   <mailto:fernando.pereniguez@cud.upct.es>
           ";

           description
               "Data model for IKE-less case in the SDN-base IPsec flow
                protection service.

                Copyright (c) 2019 IETF Trust and the persons
                identified as authors of the code.  All rights reserved.
                Redistribution and use in source and binary forms, with
                or without modification, is permitted pursuant to, and
                subject to the license terms contained in, the
                Simplified BSD License set forth in Section 4.c of the
                IETF Trust's Legal Provisions Relating to IETF Documents
                (https://trustee.ietf.org/license-info).

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

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


           revision "2019-08-05" {
               description "Revision 06";
               reference "RFC XXXX: YANG model for IKE case.";
           }


           container ipsec-ikeless {
               description



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                   "Container for configuration of the IKE-less
                    case. The container contains two additional
                    containers: 'spd' and 'sad'. The first allows the
                    Security Controller to configure IPsec policies in
                    the Security Policy Database SPD, and the second
                    allows to configure IPsec Security Associations
                    (IPsec SAs) in the Security Association Database
                    (SAD).";
               reference "RFC 4301.";
               container spd {
                   description
                       "Configuration of the Security Policy Database
                        (SPD.)";
                   reference "Section 4.4.1.2 in RFC 4301.";

                   list spd-entry {
                       key "name";
                       ordered-by user;
                       leaf name {
                           type string;
                           mandatory true;
                           description
                               "SPD entry unique name to identify this
                                entry.";
                       }
                       leaf direction {
                           type ic:ipsec-traffic-direction;
                           description
                               "Inbound traffic or outbound
                                traffic. In the IKE-less case the
                                Security Controller needs to
                                specify the policy direction to be
                                applied in the NSF. In the IKE case
                                this direction does not need to be
                                specified since IKE
                                will determine the direction that
                                IPsec policy will require.";
                       }
                       leaf reqid {
                           type uint64;
                           default 0;
                           description
                               "This value allows to link this
                                IPsec policy with IPsec SAs with the
                                same reqid. It is only required in
                                the IKE-less model since, in the IKE
                                case this link is handled internally
                                by IKE.";



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                       }

                       container ipsec-policy-config {
                           description
                               "This container carries the
                               configuration of a IPsec policy.";
                           uses ic:ipsec-policy-grouping;
                       }
                       description
                           "The SPD is represented as a list of SPD
                            entries, where each SPD entry represents an
                            IPsec policy.";
                   } /*list spd-entry*/
               } /*container spd*/

               container sad {
                   description
                       "Configuration of the IPSec Security Association
                        Database (SAD)";
                   reference "Section 4.4.2.1 in RFC 4301.";
                   list sad-entry {
                       key "name";
                       ordered-by user;
                       leaf name {
                           type string;
                           description
                               "SAD entry unique name to identify this
                                entry.";
                       }
                       leaf reqid {
                           type uint64;
                           default 0;
                           description
                               "This value allows to link this
                                IPsec SA with an IPsec policy with
                                the same reqid.";
                       }

                       container ipsec-sa-config {
                           description
                               "This container allows configuring
                               details of an IPsec SA.";
                           leaf spi {
                               type uint32 { range "0..max"; }
                               mandatory true;
                               description
                                   "Security Parameter Index (SPI)'s
                                    IPsec SA.";



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                           }
                           leaf ext-seq-num {
                               type boolean;
                               default true;
                               description
                                   "True if this IPsec SA is using
                                    extended sequence numbers. True 64
                                    bit counter, FALSE 32 bit.";
                           }
                           leaf seq-number-counter {
                               type uint64;
                               default 0;
                               description
                                    "A 64-bit counter when this IPsec
                                    SA is using Extended Sequence
                                    Number or 32-bit counter when it
                                    is not. It used to generate the
                                    initial Sequence Number field
                                    in ESP headers.";
                           }
                           leaf seq-overflow {
                               type boolean;
                               default false;
                               description
                                   "The flag indicating whether
                                    overflow of the sequence number
                                    counter should prevent transmission
                                    of additional packets on the IPsec
                                    SA (false) and, therefore needs to
                                    be rekeyed, or whether rollover is
                                    permitted (true). If Authenticated
                                    Encryption with Associated Data
                                    (AEAD) is used this flag MUST BE
                                    false.";
                           }
                           leaf anti-replay-window {
                               type uint32;
                               default 32;
                               description
                                   "A 32-bit counter and a bit-map (or
                                    equivalent) used to determine
                                    whether an inbound ESP packet is a
                                    replay. If set to 0 no anti-replay
                                    mechanism is performed.";
                           }
                           container traffic-selector {
                               uses ic:selector-grouping;
                               description



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                                   "The IPsec SA traffic selector.";
                           }
                           leaf protocol-parameters {
                               type ic:ipsec-protocol-parameters;
                               default esp;
                               description
                                   "Security protocol of IPsec SA: Only
                                   ESP so far.";
                           }
                           leaf mode {
                               type ic:ipsec-mode;
                               description
                                   "Tunnel or transport mode.";
                           }
                           container esp-sa {
                               when "../protocol-parameters =
                            'esp'";
                               description
                                   "In case the IPsec SA is
                                    Encapsulation Security Payload
                                    (ESP), it is required to specify
                                    encryption and integrity
                                    algorithms, and key material.";

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

                                   leaf encryption-algorithm {
                                     type ic:encryption-algorithm-type;
                                     description
                                           "Configuration of ESP
                                            encryption. With AEAD
                                            algorithms, the integrity
                                            node is not used.";
                                   }

                                   leaf key {
                                       nacm:default-deny-all;
                                       type yang:hex-string;
                                       description
                                           "ESP encryption key value.";
                                    }
                                   leaf iv {
                                       nacm:default-deny-all;



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                                       type yang:hex-string;
                                       description
                                           "ESP encryption IV value.";
                                   }
                               }
                               container integrity {
                                   description
                                       "Configuration of integrity for
                                        IPSec Encapsulation Security
                                        Payload (ESP). This container
                                        allows to configure integrity
                                        algorithm when no AEAD
                                        algorithms are used, and
                                        integrity is required.";
                                    leaf integrity-algorithm {
                                       type ic:integrity-algorithm-type;
                                       description
                                           "Message Authentication Code
                                           (MAC) algorithm to provide
                                           integrity in ESP.";
                                   }
                                   leaf key {
                                       nacm:default-deny-all;
                                       type yang:hex-string;
                                       description
                                           "ESP integrity key value.";
                                   }
                               }
                           } /*container esp-sa*/

                           container sa-lifetime-hard {
                               description
                                   "IPsec SA hard lifetime. The action
                                   associated is terminate and
                                   hold.";
                               uses ic:lifetime;
                           }
                           container sa-lifetime-soft {
                               description
                                   "IPSec SA soft lifetime.";
                               uses ic:lifetime;
                               leaf action {
                                   type ic:lifetime-action;
                                   description
                                       "Action lifetime:
                                        terminate-clear,
                                        terminate-hold or replace.";
                               }



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                           }
                           container tunnel {
                               when "../mode = 'tunnel'";
                               uses ic:tunnel-grouping;
                               description
                                    "Endpoints of the IPsec tunnel.";
                           }
                           container encapsulation-type
                           {
                               uses ic:encap;
                               description
                                   "This container carries
                                    configuration information about
                                    the source and destination ports
                                    which will be used for ESP
                                    encapsulation that ESP packets the
                                    type of encapsulation when NAT
                                    traversal is in place.";
                           }
                       } /*ipsec-sa-config*/

                       container ipsec-sa-state {
                           config false;
                           description
                               "Container describing IPsec SA state
                               data.";
                           container sa-lifetime-current {
                               uses ic:lifetime;
                               description
                                   "SAD lifetime current.";
                           }
                           container replay-stats {
                               description
                                   "State data about the anti-replay
                                    window.";
                               leaf replay-window {
                                   type uint64;
                                   description
                                       "Current state of the replay
                                        window.";
                               }
                               leaf packet-dropped {
                                   type uint64;
                                   description
                                       "Packets detected out of the
                                        replay window and dropped
                                        because they are replay
                                        packets.";



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                               }
                               leaf failed {
                                   type uint32;
                                   description
                                       "Number of packets detected out
                                        of the replay window.";
                               }
                               leaf seq-number-counter {
                                   type uint64;
                                   description
                                       "A 64-bit counter when this
                                        IPsec SA is using Extended
                                        Sequence Number or 32-bit
                                        counter when it is not.
                                        Current value of sequence
                                        number.";
                               }
                           } /* container replay-stats*/
                       } /*ipsec-sa-state*/

                       description
                           "List of SAD entries that conforms the SAD.";
                   } /*list sad-entry*/
               } /*container sad*/
           }/*container ipsec-ikeless*/

           /* Notifications */
           notification sadb-acquire {
               description
                   "An IPsec SA is required. The traffic-selector
                    container contains information about the IP packet
                    that triggers the acquire notification.";
               leaf ipsec-policy-name {
                   type string;
                   mandatory true;
                   description
                       "It contains the SPD entry name (unique) of
                        the IPsec policy that hits the IP packet
                        required IPsec SA. It is assumed the
                        Security Controller will have a copy of the
                        information of this policy so it can
                        extract all the information with this
                        unique identifier. The type of IPsec SA is
                        defined in the policy so the Security
                        Controller can also know the type of IPsec
                        SA that must be generated.";
               }
               container traffic-selector {



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                    description
                        "The IP packet that triggered the acquire
                         and requires an IPsec SA. Specifically it
                         will contain the IP source/mask and IP
                         destination/mask; protocol (udp, tcp,
                         etc...); and source and destination
                         ports.";
                    uses ic:selector-grouping;
                }
           }

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



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                   mandatory true;
                   description
                       "It contains the SAD entry name (unique) of
                        the IPsec SA that is about to have sequence
                        number overflow and rollover is not permitted.
                        It is assumed the Security Controller will have
                        a copy of the IPsec SA information (except the
                        cryptographic material and state data) indexed
                        by this name (unique identifier) so the it can
                        know all the information (crypto algorithms,
                        etc.) about the IPsec SA that has expired in
                        order to perform a rekey of the IPsec SA.";
               }
           }
           notification sadb-bad-spi {
               description
                   "Notify when the NSF receives a packet with an
                    incorrect SPI (i.e. not present in the SAD).";
               leaf spi {
                   type uint32 { range "0..max"; }
                   mandatory true;
                   description
                       "SPI number contained in the erroneous IPsec
                        packet.";
               }
           }
       }/*module ietf-ipsec*/

       <CODE ENDS>



Appendix D.  Example of IKE case, tunnel mode (gateway-to-gateway) with
             X.509 certificate authentication.

   This example shows a XML configuration file sent by the Security
   Controller to establish a IPsec Security Association between two NSFs
   in tunnel mode (gateway-to-gateway) with ESP, and authentication
   based on X.509 certificates using IKEv2.












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                        Security Controller
                              |
                 /---- Southbound interface -----\
                /                                 \
               /                                   \
              /                                     \
             /                                       \
            nsf_h1                                  nsf_h2
    h1---- (:1/:100)===== IPsec_ESP_Tunnel_mode =====(:200/:1)-------h2
    2001:DB8:1:/64       (2001:DB8:123:/64)           2001:DB8:2:/64

     Figure 7: IKE case, tunnel mode , X.509 certicate authentication.


   <ipsec-ike xmlns="urn:ietf:params:xml:ns:yang:ietf-ipsec-ike"
   xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
     <pad>
       <pad-entry>
         <name>nsf_h1_pad</name>
         <ipv6-address>2001:DB8:123::100</ipv6-address>
         <peer-authentication>
            <auth-method>digital-signature</auth-method>
            <digital-signature>
               <cert-data>base64encodedvalue==</cert-data>
               <private-key>base64encodedvalue==</private-key>
               <ca-data>base64encodedvalue==</ca-data>
            </digital-signature>
         </peer-authentication>
       </pad-entry>
       <pad-entry>
         <name>nsf_h2_pad</name>
         <ipv6-address>2001:DB8:123::200</ipv6-address>
         <auth-protocol>ikev2</auth-protocol>
         <peer-authentication>
           <auth-method>digital-signature</auth-method>
           <digital-signature>
             <!-- RSA Digital Signature -->
             <ds-algorithm>1</ds-algorithm>
             <cert-data>base64encodedvalue==</cert-data>
             <ca-data>base64encodedvalue==</ca-data>
           </digital-signature>
         </peer-authentication>
       </pad-entry>
     </pad>
     <conn-entry>
        <name>nsf_h1-nsf_h2</name>
        <autostartup>start</autostartup>
        <version>ikev2</version>



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        <initial-contact>false</initial-contact>
        <fragmentation>true</fragmentation>
        <ike-sa-lifetime-soft>
           <rekey-time>60</rekey-time>
           <reauth-time>120</reauth-time>
        </ike-sa-lifetime-soft>
        <ike-sa-lifetime-hard>
           <over-time>3600</over-time>
        </ike-sa-lifetime-hard>
        <authalg>7</authalg>
        <!--AUTH_HMAC_SHA1_160-->
        <encalg>3</encalg>
        <!--ENCR_3DES -->
        <dh-group>18</dh-group>
        <!--8192-bit MODP Group-->
        <half-open-ike-sa-timer>30</half-open-ike-sa-timer>
        <half-open-ike-sa-cookie-threshold>
           15
        </half-open-ike-sa-cookie-threshold>
        <local>
            <local-pad-entry-name>nsf_h1_pad</local-pad-entry-name>
        </local>
        <remote>
            <remote-pad-entry-name>nsf_h2_pad</remote-pad-entry-name>
        </remote>
        <spd>
          <spd-entry>
             <name>nsf_h1-nsf_h2</name>
             <ipsec-policy-config>
               <anti-replay-window>32</anti-replay-window>
               <traffic-selector>
                  <local-subnet>2001:DB8:1::0/64</local-subnet>
                  <remote-subnet>2001:DB8:2::0/64</remote-subnet>
                  <inner-protocol>any</inner-protocol>
                  <local-ports>
                    <start>0</start>
                    <end>0</end>
                  </local-ports>
                  <remote-ports>
                    <start>0</start>
                    <end>0</end>
                  </remote-ports>
               </traffic-selector>
               <processing-info>
                  <action>protect</action>
                  <ipsec-sa-cfg>
                     <pfp-flag>false</pfp-flag>
                     <ext-seq-num>true</ext-seq-num>



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                     <seq-overflow>false</seq-overflow>
                     <stateful-frag-check>false</stateful-frag-check>
                     <mode>tunnel</mode>
                     <protocol-parameters>esp</protocol-parameters>
                     <esp-algorithms>
                        <!-- AUTH_HMAC_SHA1_96 -->
                        <integrity>2</integrity>
                        <!-- ENCR_AES_CBC -->
                        <encryption>12</encryption>
                        <tfc-pad>false</tfc-pad>
                     </esp-algorithms>
                     <tunnel>
                        <local>2001:DB8:123::100</local>
                        <remote>2001:DB8:123::200</remote>
                        <df-bit>clear</df-bit>
                        <bypass-dscp>true</bypass-dscp>
                        <ecn>false</ecn>
                    </tunnel>
                  </ipsec-sa-cfg>
               </processing-info>
             </ipsec-policy-config>
          </spd-entry>
        </spd>
        <child-sa-info>
           <!--8192-bit MODP Group -->
           <pfs-groups>18</pfs-groups>
           <child-sa-lifetime-soft>
              <bytes>1000000</bytes>
              <packets>1000</packets>
              <time>30</time>
              <idle>60</idle>
              <action>replace</action>
           </child-sa-lifetime-soft>
           <child-sa-lifetime-hard>
              <bytes>2000000</bytes>
              <packets>2000</packets>
              <time>60</time>
              <idle>120</idle>
           </child-sa-lifetime-hard>
        </child-sa-info>
      </conn-entry>
   </ipsec-ike>









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Appendix E.  Example of IKE-less case, transport mode (host-to-host).

   This example shows a XML configuration file sent by the Security
   Controller to establish a IPsec Security association between two NSFs
   in transport mode (host-to-host) with ESP.

                             Security Controller
                                       |
                        /---- Southbound interface -----\
                       /                                 \
                      /                                   \
                     /                                     \
                    /                                       \
                 nsf_h1                                    nsf_h2
                 (:100)===== IPsec_ESP_Transport_mode =====(:200)
                               (2001:DB8:123:/64)

                 Figure 8: IKE-less case, transport mode.


   <ipsec-ikeless
     xmlns="urn:ietf:params:xml:ns:yang:ietf-ipsec-ikeless"
     xmlns:nc="urn:ietf:params:xml:ns:netconf:base:1.0">
     <spd>
       <spd-entry>
           <name>
              in/trans/2001:DB8:123::200/2001:DB8:123::100
           </name>
           <direction>inbound</direction>
           <reqid>1</reqid>
           <ipsec-policy-config>
              <traffic-selector>
                <local-subnet>2001:DB8:123::200/128</local-subnet>
                <remote-subnet>2001:DB8:123::100/128</remote-subnet>
                <inner-protocol>any</inner-protocol>
                   <local-ports>
                      <start>0</start>
                      <end>0</end>
                   </local-ports>
                   <remote-ports>
                      <start>0</start>
                      <end>0</end>
                    </remote-ports>
              </traffic-selector>
              <processing-info>
                 <action>protect</action>
                 <ipsec-sa-cfg>
                   <ext-seq-num>true</ext-seq-num>



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                   <seq-overflow>true</seq-overflow>
                   <mode>transport</mode>
                   <protocol-parameters>esp</protocol-parameters>
                   <esp-algorithms>
                      <!--AUTH_HMAC_SHA1_96-->
                      <integrity>2</integrity>
                      <!--ENCR_AES_CBC -->
                      <encryption>12</encryption>
                   </esp-algorithms>
                 </ipsec-sa-cfg>
               </processing-info>
             </ipsec-policy-config>
           </spd-entry>
           <spd-entry>
             <name>out/trans/2001:DB8:123::100/2001:DB8:123::200</name>
             <direction>outbound</direction>
             <reqid>1</reqid>
             <ipsec-policy-config>
               <traffic-selector>
                 <local-subnet>2001:DB8:123::100/128</local-subnet>
                 <remote-subnet>2001:DB8:123::200/128</remote-subnet>
                 <inner-protocol>any</inner-protocol>
                 <local-ports>
                   <start>0</start>
                   <end>0</end>
                 </local-ports>
                 <remote-ports>
                   <start>0</start>
                   <end>0</end>
                 </remote-ports>
               </traffic-selector>
               <processing-info>
                 <action>protect</action>
                 <ipsec-sa-cfg>
                   <ext-seq-num>true</ext-seq-num>
                   <seq-overflow>true</seq-overflow>
                   <mode>transport</mode>
                   <protocol-parameters>esp</protocol-parameters>
                   <esp-algorithms>
                     <!-- AUTH_HMAC_SHA1_96 -->
                     <integrity>2</integrity>
                     <!-- ENCR_AES_CBC -->
                     <encryption>12</encryption>
                   </esp-algorithms>
                  </ipsec-sa-cfg>
                </processing-info>
              </ipsec-policy-config>
           </spd-entry>



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        </spd>
        <sad>
          <sad-entry>
            <name>out/trans/2001:DB8:123::100/2001:DB8:123::200</name>
            <reqid>1</reqid>
            <ipsec-sa-config>
               <spi>34501</spi>
               <ext-seq-num>true</ext-seq-num>
               <seq-number-counter>100</seq-number-counter>
               <seq-overflow>true</seq-overflow>
               <anti-replay-window>32</anti-replay-window>
               <traffic-selector>
                 <local-subnet>2001:DB8:123::100/128</local-subnet>
                 <remote-subnet>2001:DB8:123::200/128</remote-subnet>
                    <inner-protocol>any</inner-protocol>
                    <local-ports>
                       <start>0</start>
                       <end>0</end>
                    </local-ports>
                    <remote-ports>
                       <start>0</start>
                       <end>0</end>
                    </remote-ports>
                </traffic-selector>
                <protocol-parameters>esp</protocol-parameters>
                <mode>transport</mode>
                <esp-sa>
                  <encryption>
                     <!-- //ENCR_AES_CBC -->
                     <encryption-algorithm>12</encryption-algorithm>
                     <key>01:23:45:67:89:AB:CE:DF</key>
                     <iv>01:23:45:67:89:AB:CE:DF</iv>
                  </encryption>
                  <integrity>
                     <!-- //AUTH_HMAC_SHA1_96 -->
                     <integrity-algorithm>2</integrity-algorithm>
                     <key>01:23:45:67:89:AB:CE:DF</key>
                  </integrity>
                </esp-sa>
            </ipsec-sa-config>
          </sad-entry>
          <sad-entry>
             <name>in/trans/2001:DB8:123::200/2001:DB8:123::100</name>
             <reqid>1</reqid>
             <ipsec-sa-config>
                 <spi>34502</spi>
                 <ext-seq-num>true</ext-seq-num>
                 <seq-number-counter>100</seq-number-counter>



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                 <seq-overflow>true</seq-overflow>
                 <anti-replay-window>32</anti-replay-window>
                 <traffic-selector>
                    <local-subnet>2001:DB8:123::200/128</local-subnet>
                    <remote-subnet>2001:DB8:123::100/128</remote-subnet>
                    <inner-protocol>any</inner-protocol>
                    <local-ports>
                       <start>0</start>
                       <end>0</end>
                    </local-ports>
                    <remote-ports>
                       <start>0</start>
                       <end>0</end>
                    </remote-ports>
                 </traffic-selector>
                 <protocol-parameters>esp</protocol-parameters>
                 <mode>transport</mode>
                 <esp-sa>
                    <encryption>
                       <!-- //ENCR_AES_CBC -->
                       <encryption-algorithm>12</encryption-algorithm>
                       <key>01:23:45:67:89:AB:CE:DF</key>
                       <iv>01:23:45:67:89:AB:CE:DF</iv>
                    </encryption>
                    <integrity>
                       <!-- //AUTH_HMAC_SHA1_96 -->
                       <integrity-algorithm>2</integrity-algorithm>
                       <key>01:23:45:67:89:AB:CE:DF</key>
                    </integrity>
                  </esp-sa>
                  <sa-lifetime-hard>
                     <bytes>2000000</bytes>
                     <packets>2000</packets>
                     <time>60</time>
                     <idle>120</idle>
                  </sa-lifetime-hard>
                  <sa-lifetime-soft>
                     <bytes>1000000</bytes>
                     <packets>1000</packets>
                     <time>30</time>
                     <idle>60</idle>
                     <action>replace</action>
                  </sa-lifetime-soft>
            </ipsec-sa-config>
          </sad-entry>
       </sad>
   </ipsec-ikeless>




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Appendix F.  Examples of notifications.

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


   <sadb-expire xmlns="urn:ietf:params:xml:ns:yang:ietf-ipsec-ikeless">
   <ipsec-sa-name>in/trans/2001:DB8:123::200/2001:DB8:123::100
   </ipsec-sa-name>
       <soft-lifetime-expire>true</soft-lifetime-expire>
          <lifetime-current>
             <bytes>1000000</bytes>
             <packets>1000</packets>
             <time>30</time>
             <idle>60</idle>
          </lifetime-current>
   </sadb-expire>


              Figure 9: Example of sadb-expire notification.


   <sadb-acquire xmlns="urn:ietf:params:xml:ns:yang:ietf-ipsec-ikeless">
       <ipsec-policy-name>in/trans/2001:DB8:123::200/2001:DB8:123::100
       </ipsec-policy-name>
       <traffic-selector>
           <local-subnet>2001:DB8:123::200/128</local-subnet>
           <remote-subnet>2001:DB8:123::100/128</remote-subnet>
           <inner-protocol>any</inner-protocol>
            <local-ports>
                 <start>0</start>
                 <end>0</end>
            </local-ports>
            <remote-ports>
                 <start>0</start>
                 <end>0</end>
            </remote-ports>
       </traffic-selector>
   </sadb-acquire>


             Figure 10: Example of sadb-acquire notification.







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   <sadb-seq-overflow
       xmlns="urn:ietf:params:xml:ns:yang:ietf-ipsec-ikeless">
         <ipsec-sa-name>in/trans/2001:DB8:123::200/2001:DB8:123::100
         </ipsec-sa-name>
   </sadb-seq-overflow>


           Figure 11: Example of sadb-seq-overflow notification.


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


             Figure 12: Example of sadb-bad-spi notification.

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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