





Internet Engineering Task Force (IETF)                   D. Migault, Ed.
Request for Comments: 7791                                      Ericsson
Category: Standards Track                                     V. Smyslov
ISSN: 2070-1721                                               ELVIS-PLUS
                                                              March 2016


                  Cloning the IKE Security Association
        in the Internet Key Exchange Protocol Version 2 (IKEv2)

Abstract

   This document considers a VPN end user establishing an IPsec Security
   Association (SA) with a Security Gateway using the Internet Key
   Exchange Protocol version 2 (IKEv2), where at least one of the peers
   has multiple interfaces or where Security Gateway is a cluster with
   each node having its own IP address.

   The protocol described allows a peer to clone an IKEv2 SA, where an
   additional SA is derived from an existing one.  The newly created IKE
   SA is set without the IKEv2 authentication exchange.  This IKE SA can
   later be assigned to another interface or moved to another cluster
   node.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7791.














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Copyright Notice

   Copyright (c) 2016 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
   (http://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 Notation . . . . . . . . . . . . . . . . . . . .   5
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Protocol Details  . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Support Negotiation . . . . . . . . . . . . . . . . . . .   6
     5.2.  Cloning the IKE SA  . . . . . . . . . . . . . . . . . . .   7
     5.3.  Error Handling  . . . . . . . . . . . . . . . . . . . . .   7
   6.  Payload Description . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Setting a VPN on Multiple Interfaces . . . . . . . .  11
     A.1.  Setting VPN_0 . . . . . . . . . . . . . . . . . . . . . .  11
     A.2.  Creating an Additional IKE SA . . . . . . . . . . . . . .  12
     A.3.  Creating the Child SA for VPN_1 . . . . . . . . . . . . .  12
     A.4.  Moving VPN_1 on Interface_1 . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14













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1.  Introduction

   The main scenario that motivated this document is a VPN end user
   establishing a VPN with a Security Gateway when at least one of the
   peers has multiple interfaces.  Figure 1 represents the case when the
   VPN end user has multiple interfaces, Figure 2 represents the case
   when the Security Gateway has multiple interfaces, and Figure 3
   represents the case when both the VPN end user and the Security
   Gateway have multiple interfaces.  With Figure 1 and Figure 2, one of
   the peers has n = 2 interfaces and the other has a single interface.
   This results in the creation of up to n = 2 VPNs.  With Figure 3, the
   VPN end user has n = 2 interfaces and the Security Gateway has m = 2
   interfaces.  This may lead to up to m x n VPNs.

   +------------+                                +------------+
   |            | Interface_0 : VPN_0            |            |
   |            =================                |            |
   |    VPN     |               v                |  Security  |
   |  End User  |               ==================  Gateway   |
   |            ================^                |            |
   |            | Interface_1 : VPN_1            |            |
   +------------+                                +------------+

              Figure 1: VPN End User with Multiple Interfaces

   +------------+                                +------------+
   |            |            Interface_0 : VPN_0 |            |
   |            |               ==================            |
   |    VPN     |               v                |  Security  |
   |  End User  =================                |  Gateway   |
   |            |               ^=================            |
   |            |            Interface_1 : VPN_1 |            |
   +------------+                                +------------+

            Figure 2: Security Gateway with Multiple Interfaces

   +------------+                                +------------+
   |            | Interface_0       Interface_0' |            |
   |            ==================================            |
   |    VPN     |             \\ //              |  Security  |
   |  End User  |             // \\              |  Gateway   |
   |            ==================================            |
   |            | Interface_1       Interface_1' |            |
   +------------+                                +------------+

   Figure 3: VPN End User and Security Gateway with Multiple Interfaces





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   With the current IKEv2 protocol [RFC7296], each VPN requires an IKE
   SA, and setting an IKE SA requires an authentication.  Authentication
   might require multiple round trips and an activity from the end user
   (like EAP-SIM [RFC4186] or EAP-TLS [RFC5216]) as well as crypto
   operations that would introduce an additional delay.

   Another scenario is a load-balancing solution.  Load-sharing clusters
   are often built to be transparent for VPN end users.  In the case of
   IPsec, this means that IKE and IPsec SA states are duplicated on
   every cluster node where the load balancer can redirect packets.  The
   drawback of such an approach is that anti-replay related data (in
   particular, Sequence Number) must be reliably synchronized between
   participating nodes per every outgoing Authentication Header (AH) or
   Encapsulating Security Payload (ESP) packet, which makes building
   high-speed systems problematic.  Another approach for building load-
   balancing systems is to make VPN end users aware of them, which
   allows for having two or more Security Gateways sharing the same ID,
   but each having its own IP address.  In this case, the VPN end user
   first establishes an IKE SA with one of these gateways.  Then, at
   some point of time the gateway makes a decision to move the client to
   a different cluster node.  This can be done with Redirect Mechanism
   for IKEv2 [RFC5685].  The drawback of such an approach is that it
   requires a new IKE SA to be established from scratch, including full
   authentication.  In some cases, this could be avoided by using IKEv2
   Session Resumption [RFC5723] with a new gateway.  However, this
   requires the VPN end user to know beforehand which new gateway to
   connect to.  So, it is desirable to be able to clone the existing IKE
   SA, move it to a different Security Gateway, and then indicate to the
   VPN end user to use this new SA.  This would allow participating
   Security Gateways to share the load between them.

   This document introduces the possibility of cloning the IKE SA in the
   Internet Key Exchange Protocol Version 2 (IKEv2).  The main idea is
   that the peer with multiple interfaces sets the first IKE SA as
   usual.  Then it takes advantage of the fact that this SA is completed
   and derives as many new parallel IKE SAs from it as the desired
   number of VPNs.  On each IKE SA a VPN is negotiated by creating one
   or more IPsec SAs.  This results in coexisting parallel VPNs.  Then
   the VPN end user moves each IPsec SA to its proper location using the
   IKEv2 Mobility and Multihoming Protocol (MOBIKE) [RFC4555].
   Alternatively, the VPN end user may first move the IKE SAs and then
   create the IPsec SAs.

   Note that it is up to the host's local policy to decide which
   additional VPNs to create and when to do it.  The process of
   selecting address pairs for migration is a local matter.





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   Furthermore, in the case of multiple interfaces on both ends, care
   should be taken to avoid the VPNs being duplicated by both ends or
   moved to both interfaces.

   In addition, multiple MOBIKE operations may be involved from the
   Security Gateway or the VPN end user.  Suppose, as depicted in
   Figure 3 for example, that the cloned VPN is between Interface _0 and
   Interface_0', and the VPN end user and the Security Gateway want to
   move it to Interface_1 and Interface_1'.  The VPN end user may
   initiate a MOBIKE exchange in order to move it to Interface_1, in
   which case the cloned VPN is now between Interface_1 and
   Interface_0'.  Then the Security Gateway may also initiate a MOBIKE
   exchange in order to move the VPN to Interface_1', in which case the
   VPN has reached its final destination.

   The combination of the IKE SA cloning with MOBIKE protocol provides
   IPsec communications with multiple interfaces the following
   advantages.  First, cloning the IKE SA requires very few
   modifications to already existing IKEv2 implementations.  Then, it
   takes advantage of the already existing and widely deployed MOBIKE
   protocol.  Finally, it keeps a dedicated IKE SA for each VPN, which
   simplifies reachability tests and VPN maintenance.

   Note also that the cloning of the IKE SA is independent from MOBIKE
   and can also address other future scenarios not described in the
   current document.

2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Terminology

   This section defines terms and acronyms used in this document.

   - VPN:  Virtual Private Network -- one or more Child (IPsec) SAs
         created in tunnel mode between two peers.

   - VPN End User:  designates the end user that initiates the VPN with
         a Security Gateway.  This end user may be mobile and move its
         VPN from one Security Gateway to another.








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   - Security Gateway:  designates a point of attachment for the VPN
         service.  In this document, the VPN service is provided by
         multiple Security Gateways.  Each Security Gateway may be
         considered as a specific hardware.

   - IKE SA:  IKE Security Association as defined in [RFC7296].

4.  Protocol Overview

   This document specifies how to clone existing IKE SAs without
   performing new authentication.  In order to achieve this goal, this
   document proposes that the two peers agree upon their ability to
   clone the IKE SA.  This is done during the IKE_AUTH exchange by
   exchanging the CLONE_IKE_SA_SUPPORTED notifications.  To create a new
   parallel IKE SA, one of the peers initiates a CREATE_CHILD_SA
   exchange as if it would rekey the existing IKE SA.  In order to
   indicate that the current IKE SA must not be deleted, the initiator
   includes the CLONE_IKE_SA notification in the CREATE_CHILD_SA
   exchange.  This results in two parallel IKE SAs.

   Note that without the CLONE_IKE_SA notification, the old IKE SA would
   be deleted after the rekey is successfully completed (as specified in
   Section 2.8 of [RFC7296].

5.  Protocol Details

5.1.  Support Negotiation

   The initiator and the responder indicate their support for cloning
   IKE SA by exchanging the CLONE_IKE SA_SUPPORTED notifications.  This
   notification MUST be sent in the IKE_AUTH exchange (in case of
   multiple IKE_AUTH exchanges -- in the first IKE_AUTH message from
   initiator and in the last IKE_AUTH message from responder).  If both
   initiator and responder send this notification during the IKE_AUTH
   exchange, peers may clone this IKE SA.  In the other case, the IKE SA
   MUST NOT be cloned.

   Initiator                         Responder
   -------------------------------------------------------------------
   HDR, SA, KEi, Ni -->
                                <-- HDR, SA, KEr, Nr
   HDR, SK {IDi, AUTH,
        SA, TSi, TSr,
        N(CLONE_IKE_SA_SUPPORTED)} -->
                                <-- HDR, SK {IDr, AUTH,
                                         SA, TSi, TSr,
                                         N(CLONE_IKE_SA_SUPPORTED)}




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5.2.  Cloning the IKE SA

   The initiator of the rekey exchange includes the CLONE_IKE_SA
   notification in a CREATE_CHILD_SA request for rekeying the IKE SA.
   The CLONE_IKE_SA notification indicates that the current IKE SA will
   not be immediately deleted once the new IKE SA is created.  Instead,
   two parallel IKE SAs are expected to coexist.  The current IKE SA
   becomes the old IKE SA and the newly negotiated IKE SA becomes the
   new IKE SA.  The CLONE_IKE_SA notification MUST appear only in the
   request message of the CREATE_CHILD_SA exchange concerning the IKE SA
   rekey.  If the CLONE_IKE_SA notification appears in any other
   message, it MUST be ignored.

   Initiator                         Responder
   -------------------------------------------------------------------
   HDR, SK {N(CLONE_IKE_SA), SA, Ni, KEi} -->

   If the CREATE_CHILD_SA request is concerned with an IKE SA rekey and
   contains the CLONE_IKE_SA notification, the responder proceeds to the
   IKE SA rekey, creates the new IKE SA, and keeps the old IKE SA.  No
   additional Notify Payloads are included in the CREATE_CHILD_SA
   response as represented below:

                                <--  HDR, SK {SA, Nr, KEr}

   When the IKE SA is cloned, peers MUST NOT transfer existing Child SAs
   that were created by the old IKE SA to the newly created IKE SA.  So,
   all signaling messages concerning those Child SAs would continue to
   be sent over the old IKE SA.  This is different from the regular IKE
   SA rekey in IKEv2.

5.3.  Error Handling

   There may be conditions when the responder for some reason is unable
   or unwilling to clone the IKE SA.  This inability may be temporary or
   permanent.

   Temporary inability occurs when the responder doesn't have enough
   resources at the moment to clone an IKE SA or when the IKE SA is
   being deleted by the responder.  In this case, the responder SHOULD
   reject the request to clone the IKE SA with the TEMPORARY_FAILURE
   notification.

                               <--  HDR, SK {N(TEMPORARY_FAILURE)}

   After receiving this notification, the initiator MAY retry its
   request after waiting some period of time.  See Section 2.25 of
   [RFC7296] for details.



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   In some cases, the responder may have restrictions on the number of
   coexisting IKE SAs with one peer.  These restrictions may be either
   implicit (some devices may have enough resources to handle only a few
   IKE SAs) or explicit (provided by some configuration parameter).  If
   the initiator wants to clone more IKE SAs than the responder is able
   or is configured to handle, the responder SHOULD reject the request
   with the NO_ADDITIONAL_SAS notification.

                               <--  HDR, SK {N(NO_ADDITIONAL_SAS)}

   This condition is considered permanent and the initiator SHOULD NOT
   retry cloning an IKE SA until some of the existing SAs with the
   responder are deleted.

6.  Payload Description

   Figure 4 illustrates the Notify Payload packet format as described in
   Section 3.10 of [RFC7296].  This format is used for both the
   CLONE_IKE_SA and the CLONE_IKE_SA_SUPPORTED notifications.

   The CLONE_IKE_SA_SUPPORTED notification is used in an IKEv2 exchange
   of type IKE_AUTH and the CLONE_IKE_SA is used in an IKEv2 exchange of
   type CREATE_CHILD_SA.

                           1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Next Payload  |C|  RESERVED   |         Payload Length        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Protocol ID  |   SPI Size    |      Notify Message Type      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 4: Notify Payload

   The fields Next Payload, Critical Bit, RESERVED, and Payload Length
   are defined in [RFC7296].  Specific fields defined in this document
   are:

   - Protocol ID (1 octet):  Set to zero.

   - Security Parameter Index (SPI) Size (1 octet):  Set to zero.

   - Notify Message Type (2 octets):  Specifies the type of notification
         message.  It is set to 16432 for the CLONE_IKE_SA_SUPPORTED
         notification or 16433 for the CLONE_IKE_SA notification.






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7.  IANA Considerations

   IANA has allocated two values in the "IKEv2 Notify Message Types -
   Status Types" registry:

     Value    Notify Messages - Status Types
   -----------------------------------------
     16432    CLONE_IKE_SA_SUPPORTED
     16433    CLONE_IKE_SA

8.  Security Considerations

   The protocol defined in this document does not modify IKEv2.
   Security considerations for cloning an IKE SA are mostly the same as
   those for the base IKEv2 protocol described in [RFC7296].

   Cloning an IKE SA allows an initiator to duplicate existing SAs.  As
   a result, it may influence any accounting or control mechanisms based
   on a single IKE SA per authentication.

   Suppose a system has a limit on the number of IKE SAs it can handle.
   In this case, cloning an IKE SA may provide a way for resource
   exhaustion, as a single end user may populate multiple IKE SAs.

   Suppose a system shares the IPsec resources by limiting the number of
   Child SAs per IKE SA.  With a single IKE SA per end user, this
   provides an equal resource sharing.  In this case, cloning the IKE SA
   provides the means for an end user to overpass this limit.  Such a
   system should evaluate the number of Child SAs over the number of all
   IKE SAs associated to an end user.

   Note that these issues are not unique to the ability of cloning the
   IKE SA, as multiple IKE SAs between two peers may be created without
   involving a cloning method.  Note also that implementation can always
   limit the number of cloned IKE SAs.

   Suppose the VPN or any other IPsec-based service monitoring is based
   on the liveliness of the first IKE SA.  Such a system considers a
   service is accessed or used from the time IKE performs an
   authentication to the time the IKE SA is deleted.  Such accounting
   methods were fine as any IKE SA required an authentication exchange.
   As cloning the IKE SA skips the authentication phase, it may make it
   possible to delete the initial IKE SA while the service is being used
   on the cloned IKE SA.  Such accounting methods should consider that
   the service is being used from the first IKE SA establishment to
   until the last IKE SA is removed.





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   When this solution is used to build load-balancing systems, then
   there is a necessity to transfer IKE SA states between nodes of a
   load-sharing cluster.  Since IKE SA state contains sensitive
   information, such as session keys, implementations must take all due
   precautions.  Such precautions might include using technical and/or
   administrative means to protect IKE SA state data.  The details of
   what is transferred and how it is protected are out of scope of this
   document.

9.  References

9.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4555]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol
              (MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,
              <http://www.rfc-editor.org/info/rfc4555>.

   [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, <http://www.rfc-editor.org/info/rfc7296>.

9.2.  Informative References

   [RFC4186]  Haverinen, H., Ed. and J. Salowey, Ed., "Extensible
              Authentication Protocol Method for Global System for
              Mobile Communications (GSM) Subscriber Identity Modules
              (EAP-SIM)", RFC 4186, DOI 10.17487/RFC4186, January 2006,
              <http://www.rfc-editor.org/info/rfc4186>.

   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS
              Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216,
              March 2008, <http://www.rfc-editor.org/info/rfc5216>.

   [RFC5685]  Devarapalli, V. and K. Weniger, "Redirect Mechanism for
              the Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5685, DOI 10.17487/RFC5685, November 2009,
              <http://www.rfc-editor.org/info/rfc5685>.

   [RFC5723]  Sheffer, Y. and H. Tschofenig, "Internet Key Exchange
              Protocol Version 2 (IKEv2) Session Resumption", RFC 5723,
              DOI 10.17487/RFC5723, January 2010,
              <http://www.rfc-editor.org/info/rfc5723>.



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Appendix A.  Setting a VPN on Multiple Interfaces

   This section is informational and exposes how a VPN end user, as
   illustrated in Figure 1, can build two VPNs on its two interfaces
   without multiple authentications.  Other cases represented in
   Figure 2 and Figure 3 are similar and can be easily derived from this
   case.  The mechanism is based on cloning the IKE SA and the MOBIKE
   extension [RFC4555].

A.1.  Setting VPN_0

   First, the VPN end user negotiates a VPN using one interface.  This
   involves regular IKEv2 exchanges.  In addition, the VPN end user and
   the Security Gateway advertise their support for MOBIKE.  At the end
   of the IKE_AUTH exchange, VPN_0 is set as represented in Figure 5.

   +------------+                                +------------+
   |            | Interface_0 : VPN_0            |            |
   |            =================                |            |
   |    VPN     |               v                |  Security  |
   |  End User  |               ==================  Gateway   |
   |            =                                |            |
   |            | Interface_1                    |            |
   +------------+                                +------------+

                 Figure 5: VPN End User Establishing VPN_0

   The exchanges are completely described in [RFC7296] and [RFC4555].
   First, peers negotiate IKE SA parameters and exchange nonces and
   public keys in the IKE_SA_INIT exchange.  In the figure below, they
   also proceed to NAT detection because of the use of MOBIKE.

   Initiator                         Responder
   -------------------------------------------------------------------
   (IP_I0:500 -> IP_R:500)
   HDR, SA, KEi, Ni,
        N(NAT_DETECTION_SOURCE_IP),
        N(NAT_DETECTION_DESTINATION_IP)  -->

                         <--  (IP_R:500 -> IP_I0:500)
                              HDR, SA, KEr, Nr,
                                   N(NAT_DETECTION_SOURCE_IP),
                                   N(NAT_DETECTION_DESTINATION_IP)

   Then the initiator and the responder proceed to the IKE_AUTH
   exchange, advertise their support for MOBIKE and their ability to
   clone the IKE SA -- with the MOBIKE_SUPPORTED and the
   CLONE_IKE_SA_SUPPORTED notifications -- and negotiate the Child SA



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   for VPN_0.  Optionally, the initiator and the responder can advertise
   their multiple interfaces using the ADDITIONAL_IP4_ADDRESS and/or
   ADDITIONAL_IP6_ADDRESS notifications.

   (IP_I0:4500 -> IP_R:4500)
   HDR, SK {IDi, AUTH,
        SA, TSi, TSr,
        N(MOBIKE_SUPPORTED),
        [N(ADDITIONAL_IP*_ADDRESS)+,]
        N(CLONE_IKE_SA_SUPPORTED)}  -->

                         <--  (IP_R:4500 -> IP_I0:4500)
                              HDR, SK {IDr, AUTH,
                                   SA, TSi, TSr,
                                   N(MOBIKE_SUPPORTED),
                                   [N(ADDITIONAL_IP*_ADDRESS)+,]
                                   N(CLONE_IKE_SA_SUPPORTED)}

A.2.  Creating an Additional IKE SA

   In this case, the VPN end user wants to establish an additional VPN
   with its Interface_1.  The VPN end user will first establish a
   parallel IKE SA using a CREATE_CHILD_SA that concerns an IKE SA rekey
   associated with a CLONE_IKE_SA notification.  This results in two
   separate IKE SAs between the VPN end user and the Security Gateway.
   Currently both IKE SAs are set using Interface_0 of the VPN end user.

   Initiator                         Responder
   -------------------------------------------------------------------
   (IP_I0:4500 -> IP_R:4500)
   HDR, SK {N(CLONE_IKE_SA),
        SA, Ni, KEi} -->
                         <--  (IP_R:4500 -> IP_I0:4500)
                              HDR, SK {SA, Nr, KEr}

A.3.  Creating the Child SA for VPN_1

   Once the new IKE SA has been created, the VPN end user can initiate a
   CREATE_CHILD_SA exchange that concerns the creation of a Child SA for
   VPN_1.  The newly created VPN_1 will use Interface_0 of the VPN end
   user.

   It is out of scope for this document to define how the VPN end user
   handles traffic with multiple interfaces.  The VPN end user can use
   the same inner IP address on its multiple interfaces.  In this case,
   the same Traffic Selectors (that is, the IP address used for VPN_0
   and VPN_1) can match for both VPNs VPN_0 and VPN_1.  The VPN end user
   must be aware of such a match and be able to manage it.  It can, for



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   example, use distinct Traffic Selectors on both VPNs using different
   ports, manage the order of its Security Policy Database (SPD), or
   have SPD defined per interfaces.  Defining these mechanisms is out of
   scope for this document.  Alternatively, the VPN end user can use a
   different inner IP address for each interface.

   The creation of VPN_1 is performed via the newly created IKE SA as
   follows:

   Initiator                         Responder
   -------------------------------------------------------------------
   (IP_I0:4500 -> IP_R:4500)
   HDR(new), SK(new) {SA, TSi, TSr}  -->

                         <--  (IP_R:4500 -> IP_I0:4500)
                              HDR(new), SK(new) {SA, TSi, TSr}

   The resulting configuration is depicted in Figure 6.  VPN_0 and VPN_1
   have been created, but both are using the same Interface:
   Interface_0.

   +------------+                                +------------+
   |            | Interface_0 : VPN_0, VPN_1     |            |
   |            ====================             |            |
   |    VPN     =================  v             |  Security  |
   |  End User  |               v  ===============  Gateway   |
   |            |               ==================            |
   |            | Interface_1                    |            |
   +------------+                                +------------+

            Figure 6: VPN End User Establishing VPN_0 and VPN_1

A.4.  Moving VPN_1 on Interface_1

   In this section, MOBIKE is used to move VPN_1 on Interface_1.  The
   exchange is described in [RFC4555].

   (IP_I1:4500 -> IP_R:4500)
   HDR(new), SK(new) {N(UPDATE_SA_ADDRESSES),
             N(NAT_DETECTION_SOURCE_IP),
             N(NAT_DETECTION_DESTINATION_IP),
             N(COOKIE2)}  -->

                         <--  (IP_R:4500 -> IP_I1:4500)
                              HDR(new), SK(new) {
                                   N(NAT_DETECTION_SOURCE_IP),
                                   N(NAT_DETECTION_DESTINATION_IP),
                                   N(COOKIE2)}



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RFC 7791                     Cloning IKE SA                   March 2016


   This results in the situation as described in Figure 7.

   +------------+                                +------------+
   |            | Interface_0 : VPN_0            |            |
   |            ==================               |            |
   |    VPN     |                v               |  Security  |
   |  End User  |                =================  Gateway   |
   |            =================^               |            |
   |            | Interface_1 : VPN_1            |            |
   +------------+                                +------------+

              Figure 7: VPN End User with Multiple Interfaces

Acknowledgments

   The ideas for this document came from various input from the IP
   Security Maintenance and Extensions (ipsecme) Working Group and from
   discussions with Tero Kivinen and Michael Richardson.  Yaron Sheffer
   and Tero Kivinen provided significant input to set the current design
   of the protocol, as well as its designation.

Authors' Addresses

   Daniel Migault (editor)
   Ericsson
   8400 boulevard Decarie
   Montreal, QC H4P 2N2
   Canada

   Email: daniel.migault@ericsson.com


   Valery Smyslov
   ELVIS-PLUS
   PO Box 81
   Moscow (Zelenograd)  124460
   Russian Federation

   Phone: +7 495 276 0211
   Email: svan@elvis.ru











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