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INFORMATIONAL

Internet Engineering Task Force (IETF)                       R. Valmikam
Request for Comments: 7458                                  Unaffiliated
Category: Informational                                        R. Koodli
ISSN: 2070-1721                                                    Intel
                                                           February 2015


        Extensible Authentication Protocol (EAP) Attributes for
             Wi-Fi Integration with the Evolved Packet Core

Abstract

   With Wi-Fi emerging as a crucial access network for mobile service
   providers, it has become important to provide functions commonly
   available in 3G and 4G networks in Wi-Fi access networks as well.
   Such functions include Access Point Name (APN) Selection, multiple
   Packet Data Network (PDN) connections, and seamless mobility between
   Wi-Fi and 3G/4G networks.

   The EAP Authentication and Key Agreement (EAP-AKA), and EAP-AKA',
   protocol is required for mobile devices to access the mobile Evolved
   Packet Core (EPC) via Wi-Fi networks.  This document defines a few
   new EAP attributes to enable the above-mentioned functions in such
   networks.  The attributes are exchanged between a client (such as a
   Mobile Node (MN)) and its network counterpart (such as an
   Authentication, Authorization, and Accounting (AAA) server) in the
   service provider's infrastructure.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc7458.








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Copyright Notice

   Copyright (c) 2015 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
      1.1. APN Selection ..............................................4
      1.2. Multiple APN Connectivity ..................................4
      1.3. Wi-Fi to E-UTRAN Mobility ..................................4
   2. Terminology .....................................................4
   3. Protocol Overview ...............................................5
      3.1. Brief Introduction to EAP ..................................5
      3.2. IEEE 802.11 Authentication Using EAP over 802.1X ...........5
   4. New EAP Attributes ..............................................7
      4.1. APN Selection ..............................................7
      4.2. Connectivity Type ..........................................7
      4.3. Wi-Fi to UTRAN/E-UTRAN Mobility ............................8
      4.4. MN Serial ID ...............................................8
   5. Attribute Extensions ............................................8
      5.1. AT_VIRTUAL_NETWORK_ID ......................................8
      5.2. AT_VIRTUAL_NETWORK_REQ .....................................9
      5.3. AT_CONNECTIVITY_TYPE ......................................10
      5.4. AT_HANDOVER_INDICATION ....................................11
      5.5. AT_HANDOVER_SESSION_ID ....................................11
      5.6. AT_MN_SERIAL_ID ...........................................12
   6. Security Considerations ........................................13
   7. IANA Considerations ............................................14
   8. References .....................................................15
      8.1. Normative References ......................................15
      8.2. Informative References ....................................16
   Acknowledgments ...................................................18
   Authors' Addresses ................................................18







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1.  Introduction

   Wi-Fi has emerged as a "trusted" access technology for mobile service
   providers; see [EPC2] for reference to the 3rd Generation Partnership
   Project (3GPP) description of "trusted" access.  Advances in IEEE
   802.11u [IEEE802.11u] and "HotSpot 2.0" [hs20] have enabled seamless
   roaming, in which a Mobile Node can select and connect to a Wi-Fi
   access network just as it would roam into a cellular network.  It has
   thus become important to provide certain functions in Wi-Fi that are
   commonly supported in licensed-spectrum networks such as 3G and 4G
   networks.  This document specifies a few new EAP attributes for an MN
   to interact with the network to support some of these functions (see
   below).  These new attributes serve as a trigger for Proxy Mobile
   IPv6 network nodes to undertake the relevant mobility operations.
   For instance, when the MN requests a new IP session (i.e., a new APN
   in 3GPP) and the network agrees, the corresponding attribute (defined
   below) acts as a trigger for the Mobile Anchor Gateway (MAG) to
   initiate a new mobility session with the Local Mobility Anchor (LMA).
   This document refers to [RFC6459] for the basic definitions of mobile
   network terminology (such as APN) used here.

   The 3GPP networks support many functions that are not commonly
   implemented in a Wi-Fi network.  This document defines EAP attributes
   that enable the following functions in Wi-Fi access networks using
   EAP-AKA [RFC4187] and EAP-AKA' [RFC5448]:

      o APN Selection

      o Multiple APN Connectivity

      o Wi-Fi to 3G/4G (Universal Terrestrial Radio Access Network
      (UTRAN) / Evolved UTRAN (E-UTRAN)) mobility

   The attributes defined here are exchanged between the MN and the EAP
   server, typically realized as part of the AAA server infrastructure
   in a service provider's infrastructure.  In particular, the Wi-Fi
   access network simply conveys the attributes to the service
   provider's core network where the EAP processing takes place [EPC].
   Since these attributes share the same IANA registry, the methods are
   applicable to EAP-AKA, EAP-AKA', EAP Subscriber Identity Modules
   (EAP-SIM) [RFC4186], and with appropriate extensions, are possibly
   applicable for other EAP methods as well.  In addition to the trusted
   Wi-Fi access networks, the attributes are applicable to any trusted
   "non-3GPP" access network that uses the EAP methods and provides
   connectivity to the mobile EPC, which provides connectivity for 3G,
   4G, and other non-3GPP access networks [EPC2].





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1.1.  APN Selection

   The 3GPP networks support the concept of an APN.  This is defined in
   [GPRS].  Each APN is an independent IP network with its own set of IP
   services.  When the MN attaches to the network, it may select a
   specific APN to receive desired services.  For example, to receive
   generic Internet services, a user device may select APN "Internet";
   and to receive IP Multimedia Subsystems (IMS) voice services, it may
   select APN "IMSvoice".

   In a Wi-Fi access scenario, an MN needs a way of sending the desired
   APN name to the network.  This document specifies a new attribute to
   propagate the APN information via EAP.  The agreed APN is necessary
   for the Proxy Mobile IPv6 MAG to initiate a new session with the LMA.

1.2.  Multiple APN Connectivity

   As an extension of APN Selection, an MN may choose to connect to
   multiple IP networks simultaneously.  3GPP provides this feature via
   additional Packet Data Protocol (PDP) contexts or additional Packet
   Data Network (PDN) connections and defines the corresponding set of
   signaling procedures.  In a trusted Wi-Fi network, an MN connects to
   the first APN via DHCPv4 or IPv6 Router Solicitation.  This document
   specifies an attribute that indicates the MN's capability to support
   multiple APN connectivity.  The specific connectivity types are also
   necessary for the Proxy Mobile IPv6 signaling.

1.3.  Wi-Fi to E-UTRAN Mobility

   When operating in a multiaccess network, an MN may want to gracefully
   handover its IP attachment from one access network to another.  For
   instance, an MN connected to a 3GPP E-UTRAN network may choose to
   move its connectivity to a trusted Wi-Fi network.  Alternatively, the
   MN may choose to connect using both access technologies
   simultaneously and maintain two independent IP attachments.  To
   implement these scenarios, the MN needs a way to correlate the UTRAN/
   E-UTRAN session with the new Wi-Fi session.  This document specifies
   an attribute to propagate E-UTRAN session identification to the
   network via EAP.  This helps the network to correlate the sessions
   between the two Radio Access Network (RAN) technologies and thus
   helps the overall handover process.

2.  Terminology

   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].




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3.  Protocol Overview

3.1.  Brief Introduction to EAP

   EAP is defined as a generic protocol in [RFC3748].  EAP, combined
   with one of the payload protocols such as EAP-AKA' [RFC5448] can
   accomplish several things in a network:

   o  Establish the identity of the user (MN) to the network.

   o  Authenticate the user during the first attach with the help of an
      authentication center that securely maintains the user
      credentials.  This process is called "EAP Authentication".

   o  Re-authenticate the user periodically, but without the overhead of
      a round-trip to the authentication center.  This process is called
      "EAP Fast Re-Authentication".

   This document makes use of the EAP Authentication procedure.  The use
   of the EAP Fast Re-Authentication procedure is for further study.
   Both the EAP Authentication and EAP Fast Re-Authentication procedures
   are specified for trusted access network use in 3GPP[TS-33.402].

3.2.  IEEE 802.11 Authentication Using EAP over 802.1X

   In a Wi-Fi network, EAP is carried over the IEEE 802.1X
   Authentication protocol.  The IEEE 802.1X Authentication is a
   transparent, payload-unaware mechanism to carry the authentication
   messages between the MN and the Wi-Fi network elements.

   EAP, on the other hand, has multiple purposes.  Apart from its core
   functions of communicating an MN's credentials to the network and
   proving the MN's identity, it also allows the MN to send arbitrary
   information elements to help establish the MN's IP session in the
   network.  Figure 1 shows an example of end-to-end EAP flow in the
   context of an IEEE 802.11 Wi-Fi network.  We first define the
   terminology:

   o  MN: Mobile Node

   o  WAN: Wi-Fi Access Node, typically consisting of Wi-Fi Access Point
      and Wi-Fi Controller.  The CAPWAP [RFC5415] protocol allows these
      functions to be realized in separate physical nodes or in a single
      node.  In a Proxy Mobile IPv6 (PMIPv6) [RFC5213] network, the MAG
      functionality is located in the WAN, either in the Wi-Fi Access
      Point or in the Wi-Fi Controller.





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   o  AAA: The infrastructure node supporting the AAA server with the
      EAP methods (AKA, AKA', EAP-SIM).  The endpoints of the EAP method
      are the MN and the AAA server.

   o  IPCN: IP Core Network.  This includes the PMIPv6 LMA function.

  MN                        WAN                        AAA         IPCN
                           (MAG)                                   (LMA)
  1)|<----------Beacon--------|                         |             |
  2)|<----------Probe-------->|                         |             |
    |                         |                         |             |
    |              802.11 Auth|                         |             |
  3)|<----------------------->|                         |             |
    |                         |                         |             |
    |       802.11 Association|                         |             |
  4)|<----------------------->|                         |             |
    |                         |                         |             |
  5)|<----EAP Req/Identity----|                         |             |
    |                         |                         |             |
  6)|----EAP Resp/Identity----|->--EAP Resp/Identity--->|             |
    |                         |                         |             |
  7)|<-EAP Req/AKA-Challenge<-|--EAP Req/AKA-Challenge--|             |
    |                         |                         |             |
  8)|-EAP Resp/AKA-Challenge--|>EAP Resp/AKA-Challenge->|             |
    |                         |                         |             |
  9)|<-----EAP Success------<-|------EAP Success--------|             |
    |                         |                         |             |
 10)|<====== 802.11 Data ====>|<========== 802.11 Data ====Tunnel to=>|
    |                         |                         | core network|
    |                         |                         |             |

                     Figure 1: Example EAP Deployment

   1.   An MN detects a beacon from a WAP in the vicinity.

   2.   The MN probes the WAP to determine suitability to attach (Verify
        Service Set Identifier (SSID) list, authentication type, and so
        on).

   3.   The MN initiates the IEEE 802.11 Authentication with the Wi-Fi
        network.  In Wi-Fi Protected Access (WPA) / WPA2 mode, this is
        an open authentication without any security credential
        verification.

   4.   The MN initiates 802.11 Association with the Wi-Fi network.






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   5.   The Wi-Fi network initiates 802.1X/EAP Authentication procedures
        by sending EAP Request/Identity.

   6.   The MN responds with its permanent or temporary identity.

   7.   The Wi-Fi network challenges the MN to prove its identity by
        sending EAP Request/AKA-Challenge.

   8.   The MN calculates the security digest and responds with EAP
        Response/AKA-Challenge.

   9.   If the authentication is successful, the Wi-Fi network responds
        to the MN with EAP Success.

   10.  An end-to-end data path is available for the MN to start IP
        layer communication (DHCPv4, IPv6 Router Solicitation, and so
        on).

4.  New EAP Attributes

   The following subsections define the new EAP attributes and their
   usage.

4.1.  APN Selection

   In a Wi-Fi network, an MN includes the AT_VIRTUAL_NETWORK_ID
   attribute in the EAP-Response/AKA-Challenge to indicate the desired
   APN identity for the first PDN connection.

   If the MN does not include the AT_VIRTUAL_NETWORK_ID attribute in the
   EAP-Response/AKA-Challenge, the network may select an APN by other
   means.  This selection mechanism is outside the scope of this
   document.

   An MN includes the AT_VIRTUAL_NETWORK_REQ attribute to indicate
   single or multiple PDN capability.  In addition, a Sub type in the
   attribute indicates IPv4, IPv6, or dual IPv4v6 PDN connectivity.

4.2.  Connectivity Type

   An MN indicates its preference for connectivity using the
   AT_CONNECTIVITY_TYPE attribute in the EAP-Response/AKA-Challenge
   message.  The preference indicates whether the MN wishes connectivity
   to the Evolved Packet Core (the so-called "EPC PDN connectivity") or
   Internet Offload (termed as "Non-Seamless Wireless Offload").

   The network makes its decision and replies with the same attribute in
   the EAP Success message.



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4.3.  Wi-Fi to UTRAN/E-UTRAN Mobility

   When a multiaccess MN enters a Wi-Fi network, the following
   parameters are applicable in the EAP-Response/AKA-Challenge for IP
   session continuity from UTRAN/E-UTRAN.

   o  AT_HANDOVER_INDICATION: This attribute indicates to the network
      that the MN intends to continue the IP session from UTRAN/E-UTRAN.
      If a previous session can be located, the network will honor this
      request by connecting the Wi-Fi access to the existing IP session.

   o  AT_HANDOVER_SESSION_ID: An MN MAY use this attribute to identify
      the session on UTRAN/E-UTRAN.  If used, this attribute contains
      Packet Temporary Mobile Subscriber Identity (P-TMSI) if the
      previous session was on UTRAN; if the previous session was on
      E-UTRAN, it contains Mobile Temporary Mobile Subscriber Identity
      (M-TMSI).  This attribute helps the network correlate the Wi-Fi
      session to an existing UTRAN/E-UTRAN session.

4.4.  MN Serial ID

   The MN_SERIAL_ID attribute defines an MN's serial number, including
   International Mobile Equipment Identity (IMEI) and International
   Mobile Equipment Identity Software Version (IMEISV).  The IMEI (or
   IMEISV) is used for ensuring a legitimate (and not a stolen) device
   is in use.  As with the others, this attribute is exchanged with the
   service provider's AAA server.  The MN_SERIAL_ID MUST NOT be
   propagated further by the AAA server to any other node.

5.  Attribute Extensions

   The format for the new attributes follows that in [RFC4187].  Note
   that the Length field value is inclusive of the first two bytes.

5.1.  AT_VIRTUAL_NETWORK_ID

   The AT_VIRTUAL_NETWORK_ID attribute identifies the virtual IP network
   to which the MN intends to attach.  The implementation of the virtual
   network on the core network side is technology specific.  For
   instance, in a 3GPP network, the virtual network is implemented based
   on the 3GPP APN primitive.

   This attribute SHOULD be included in the EAP-Response/AKA-Challenge
   message.







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      0                   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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |AT_VIRTUAL     | Length        | Virtual Network Id            |
      |  _NETWORK_ID  |               |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Virtual Network Id                           |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 2: AT_VIRTUAL_NETWORK_ID EAP Attribute

   Virtual Network Id:

   An arbitrary octet string that identifies a virtual network in the
   access technology to which the MN is attaching.  For instance, in
   3GPP E-UTRAN, this could be an APN.  See [TS-23.003] for encoding of
   the field.

5.2.  AT_VIRTUAL_NETWORK_REQ

   When an MN intends to connect an APN, it SHOULD use this attribute to
   indicate different capabilities to the network.  In turn, the network
   provides what is supported.

   From the MN, this attribute can be included only in EAP-Response/
   Identity.  From the network, it SHOULD be included in the EAP
   Request/AKA-Challenge message.  In the MN-to-network direction, the
   Type field (below) indicates the MN's request.  In the network-to-MN
   direction, the Type field indicates the network's willingness to
   support the request; a present Type field value indicates the network
   support for that Type.

      0                   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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |AT_VIRTUAL_    |     Length    |  Virt-Net-Req | Virt-Net-Req  |
      |NETWORK_REQ    |               |     Type      |   Sub type    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 3: AT_VIRTUAL_NETWORK_REQ EAP Attribute

   Virt-Net-Req Type:

   Type can have one of the following values:

   o  0: Reserved




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   o  1: Single PDN connection

   o  2: Multiple PDN connection.  Can request Non-Seamless Wi-Fi
      Offload or EPC connectivity (see the Connectivity Type attribute
      below)

   Virt-Net-Req Sub type:

   Sub type can have one of the following values:

   o  0: Reserved

   o  1: PDN Type: IPv4

   o  2: PDN Type: IPv6

   o  3: PDN Type: IPv4v6

5.3.  AT_CONNECTIVITY_TYPE

   An MN uses this attribute to indicate whether it wishes the
   connectivity type to be Non-Seamless WLAN Offload or EPC.  This
   attribute is applicable for multiple PDN connections only.

   From the MN, this attribute can be included only in EAP-Response/
   Identity.  From the network, it SHOULD be included in the EAP
   Request/AKA-Challenge message.

      0                   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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |AT_CONNECTIVITY|     Length    | Connectivity  | Reserved      |
      |_TYPE          |               | Type          |               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 4: AT_CONNECTIVITY_TYPE EAP Attribute

   Connectivity Type:

   Connectivity Type can have one of the following values:

   o  0: Reserved

   o  1: Non-Seamless WLAN Offload (NSWO)

   o  2: EPC PDN connectivity





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5.4.  AT_HANDOVER_INDICATION

   This attribute indicates an MN's handover intention of an existing IP
   attachment.

   This attribute SHOULD be included in the EAP-Response/AKA-Challenge
   message.

      0                   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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |AT_HANDOVER_IND|     Length    | Handover      |   Pad         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5: AT_HANDOVER_INDICATION EAP Attribute

   Handover Type:

   o  0 - The MN has no intention of handing over an existing IP
      session, i.e., the MN is requesting an independent IP session with
      the Wi-Fi network without disrupting the IP session with the
      UTRAN/E-UTRAN.  In this case, no Session Id (Section 5.5) is
      included.

   o  1 - The MN intends to handover an existing IP session.  In this
      case, MN MAY include a Session Id (Section 5.5) to correlate this
      Wi-Fi session with a UTRAN/E-UTRAN session.

5.5.  AT_HANDOVER_SESSION_ID

   When an MN intends to handover an earlier IP session to the current
   access network, it may propagate a session identity that can help
   identify the previous session from UTRAN/E-UTRAN that the MN intends
   to handover.  This attribute is defined as a generic octet string.
   The MN MAY include an E-UTRAN Globally Unique Temporary User
   Equipment Identity (GUTI) if the previous session was an E-UTRAN
   session.  If the previous session was a UTRAN session, the MN MAY
   include a UTRAN Global Radio Network Controller (RNC) ID (Mobile
   Country Code (MCC), Mobile Network Code (MNC), RNC ID) and P-TMSI
   concatenated as an octet string.

   This attribute SHOULD be included in the EAP-Response/AKA-Challenge
   message.








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   0                   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |AT_HANDOVER_   |   Length      |  Access       |  Reserved     |
   |  SESSION_ID   |               |  Technology   |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Session Id                          |
   |                              ...                              |
   |                              ...                              |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 6: AT_HANDOVER_SESSION_ID EAP Attribute

   Access Technology:

   This field represents the RAN technology from which the MN is
   undergoing a handover.

   o  0: Reserved

   o  1: UTRAN

   o  2: E-UTRAN

   Session Id:

   An octet string of variable length that identifies the session in the
   source access technology.  As defined at the beginning of this
   section, the actual value is RAN technology dependent.  For E-UTRAN,
   the value is GUTI.  For UTRAN, the value is Global RNC ID (6 bytes)
   followed by P-TMSI (4 bytes).  See [TS-23.003] for encoding of the
   field.

5.6.  AT_MN_SERIAL_ID

   This attribute defines the MN's machine serial number.  Examples are
   IMEI and IMEISV.

   A network that requires the machine serial number for authorization
   purposes MUST send a request for the attribute in an EAP-Request/
   AKA-Challenge message.  If the attribute is present, the MN SHOULD
   include the attribute in the EAP-Response/AKA-Challenge message.  If
   the MN sends the attribute, it MUST be contained within an
   AT_ENCR_DATA attribute.  An MN MUST NOT provide the attribute unless
   it receives the request from a network authenticated via EAP/AKA.





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   0                   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |AT_MN_         |   Length      |  Serial ID    |  Reserved     |
   |  SERIAL_ID    |               |    Type       |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           MN Serial Id                        |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 7: AT_MN_SERIAL_ID EAP Attribute

   Serial ID Type:

   This field identifies the type of the MN Identifier.

   o  0: Reserved

   o  1: IMEI

   o  2: IMEISV

   MN Serial Id:

   An arbitrary octet string that identifies the MN's machine serial
   number.  The actual value is device specific.  See [TS-23.003] for
   encoding of the field.  When sent by the network in the EAP-Request/
   AKA-Challenge message, this field is not present, which serves as an
   indication for the MN to provide the attribute in the EAP-Response/
   AKA-Challenge message.

   An AT_MN_SERIAL_ID attribute MUST only be used with methods that can
   provide mutual (network and device) authentication, such as AKA,
   AKA', and EAP-SIM.

6.  Security Considerations

   This document defines new EAP attributes to extend the capability of
   the EAP-AKA protocol as specified in Section 8.2 of [RFC4187].  The
   attributes are passed between an MN and a AAA server in provider-
   controlled, trusted Wi-Fi networks, where the Wi-Fi access network is
   a relay between the MN and the AAA server.  The document does not
   specify any new messages or options to the EAP-AKA protocol.

   The attributes defined here are fields that are used in existing 3G
   and 4G networks, where they are exchanged (in protocols specific to
   3G and 4G networks) subsequent to the mobile network authentication
   (e.g., using the UMTS-AKA mechanism).  For the operator-controlled



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   Wi-Fi access that is connected to the same core infrastructure as the
   3G and 4G access, a similar model is followed here with the EAP-AKA
   (or EAP-AKA', EAP-SIM) authentication.  In doing so, processing these
   attributes, security-wise, is no worse than that in existing 3G and
   4G mobile networks.

   The attributes inherit the security protection (integrity, replay,
   and confidentiality) provided by the parameters in the AKA(') or SIM
   methods; see Section 12.6 in [RFC4187].  Furthermore, RFC 4187
   requires attributes exchanged in EAP-Request/AKA-Identity or
   EAP-Response/AKA-Identity to be integrity-protected with
   AT_CHECKCODE; see Section 8.2 in [RFC4187].  This requirement applies
   to the AT_CONNECTIVITY_TYPE and AT_VIRTUAL_NETWORK_REQ attributes
   defined in this document.

   The AT_MN_SERIAL_ID attribute MUST have confidentiality protection
   provided by the AKA(') or EAP-SIM methods beyond the secure transport
   (such as private leased lines, VPN, etc.) deployed by the provider of
   the trusted Wi-Fi service.

   Use of identifiers such as IMEI could have privacy implications,
   wherein devices can be profiled and tracked.  With additional
   information, this could also lead to profiling of user's network
   access patterns.  Implementers should consult [hotos-2011], and the
   references therein, for a broader discussion and possible mitigation
   methods on the subject.

7.  IANA Considerations

   This document defines the following new skippable EAP-AKA attributes.
   These attributes have been assigned from the "EAP-AKA and EAP-SIM
   Parameters" registry at <https://www.iana.org/assignments/
   eapsimaka-numbers>.

   o  AT_VIRTUAL_NETWORK_ID (Section 5.1): 145

   o  AT_VIRTUAL_NETWORK_REQ (Section 5.2): 146

   o  AT_CONNECTIVITY_TYPE (Section 5.3): 147

   o  AT_HANDOVER_INDICATION (Section 5.4): 148

   o  AT_HANDOVER_SESSION_ID (Section 5.5): 149

   o  AT_MN_SERIAL_ID (Section 5.6): 150






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   A new IANA registry titled "Trusted Non-3GPP Access EAP Parameters"
   has been created.  The range for both Types and Sub types in the
   registry is 0 - 127, with 0 (zero) being a reserved value.  IANA has
   made assignments in a monotonically increasing order in increments of
   1, starting from 1.  New assignments in this registry are made with
   the Specification Required policy [RFC5226].

   The IANA Designated Expert should review the requirements for new
   assignments based on factors including, but not limited to, the
   source of request (e.g., standards bodies), deployment needs (e.g.,
   industry consortium, operator community), and experimental needs
   (e.g., academia, industrial labs).  A document outlining the purpose
   of new assignments should accompany the request.  Such a document
   could be a standards document or a research project description.  The
   Designated Expert should consider that there is sufficient evidence
   of potential usage both on the endpoints (e.g., Mobile Devices, etc.)
   and the infrastructure (e.g., AAA servers, gateways, etc.)

   The following fields have been assigned:

   o  Virt-Net-Req Type (Section 5.2): 1

   o  Virt-Net-Req Sub type (Section 5.2): 2

   o  Connectivity Type (Section 5.3): 3

   o  Access Technology (Section 5.5): 4

   o  Serial ID Type (Section 5.6): 5

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4187]  Arkko, J. and H. Haverinen, "Extensible Authentication
              Protocol Method for 3rd Generation Authentication and Key
              Agreement (EAP-AKA)", RFC4187, January 2006,
              <http://www.rfc-editor.org/info/rfc4187>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008, <http://www.rfc-editor.org/info/rfc5226>.





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   [RFC6459]  Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen,
              T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, January 2012,
              <http://www.rfc-editor.org/info/rfc6459>.

8.2.  Informative References

   [EPC]      3GPP, "General Packet Radio Service (GPRS); enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", TS 23.401 8.8.0, December 2009,
              <http://www.3gpp.org/ftp/Specs/html-info/23401.htm>.

   [EPC2]     3GPP, "Architecture enhancements for non-3GPP accesses",
              TS 23.402 8.8.0, December 2009,
              <http://www.3gpp.org/ftp/Specs/html-info/23402.htm>.

   [GPRS]     3GPP, "General Packet Radio Service (GPRS); Service
              description, Stage 2", TS 23.060, December 2006,
              <http://www.3gpp.org/ftp/Specs/html-info/23060.htm>.

   [IEEE802.11u]
              IEEE, "IEEE Standard for Information Technology-
              Telecommunications and information exchange between
              systems-Local and Metropolitan networks-specific
              requirements-Part II: Wireless LAN Medium Access Control
              (MAC) and Physical Layer (PHY) specifications: Amendment
              9: Interworking with External Networks", IEEE Std 802.11u-
              2011, February 2011, <http://standards.ieee.org/findstds/
              standard/802.11u-2011.html>.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC3748, June 2004,
              <http://www.rfc-editor.org/info/rfc3748.txt>.

   [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, January 2006,
              <http://www.rfc-editor.org/info/rfc4186>.

   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC
              5213, August 2008,
              <http://www.rfc-editor.org/info/rfc5213>.





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   [RFC5415]  Calhoun, P., Montemurro, M., and D. Stanley, "Control And
              Provisioning of Wireless Access Points (CAPWAP) Protocol
              Specification", RFC5415, January 2009,
              <http://www.rfc-editor.org/info/rfc5415.txt>.

   [RFC5448]  Arkko, J., Lehtovirta, V., and P. Eronen, "Improved
              Extensible Authentication Protocol Method for 3rd
              Generation Authentication and Key Agreement (EAP-AKA')",
              RFC 5448, May 2009,
              <http://www.rfc-editor.org/info/rfc5448>.

   [TS-23.003]
              3GPP, "Numbering, addressing and identification", TS
              23.003 12.2.0, March 2014,
              <http://www.3gpp.org/ftp/Specs/html-info/23003.htm>.

   [TS-33.402]
              3GPP, "3GPP System Architecture Evolution (SAE); Security
              aspects of non-3GPP accesses", TS 33.402 8.6.0, December
              2009, <http://www.3gpp.org/ftp/Specs/html-info/33402.htm>.

   [hotos-2011]
              Wetherall, et al., D., "Privacy Revelations for Web and
              Mobile Apps", Proceedings of the Hot Topics in Operating
              Systems (HotOS), May 2011,
              <https://www.usenix.org/legacy/events/hotos11/tech/>.

   [hs20]     "Hotspot 2.0 (Release 2) Technical Specification Package
              v1.0.0", <https://www.wi-fi.org/hotspot-20-release-2-
              technical-specification-package-v100>.





















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Acknowledgments

   Thanks to Sebastian Speicher for the review and suggesting
   improvements.  Thanks to Mark Grayson for proposing the MN Serial ID
   attribute, and thanks to Brian Haberman for suggesting a new
   registry.

Authors' Addresses

   Ravi Valmikam
   Unaffiliated
   United States

   EMail: valmikam@gmail.com


   Rajeev Koodli
   Intel
   United States

   EMail: rajeev.koodli@intel.com






























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