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rfc:rfc7458

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.

Valmikam & Koodli Informational [Page 1] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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

Valmikam & Koodli Informational [Page 2] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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].

Valmikam & Koodli Informational [Page 3] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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].

Valmikam & Koodli Informational [Page 4] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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.

Valmikam & Koodli Informational [Page 5] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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.

Valmikam & Koodli Informational [Page 6] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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.

Valmikam & Koodli Informational [Page 7] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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.

Valmikam & Koodli Informational [Page 8] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

    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

Valmikam & Koodli Informational [Page 9] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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

Valmikam & Koodli Informational [Page 10] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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.

Valmikam & Koodli Informational [Page 11] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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.

Valmikam & Koodli Informational [Page 12] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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

Valmikam & Koodli Informational [Page 13] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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

Valmikam & Koodli Informational [Page 14] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 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>.

Valmikam & Koodli Informational [Page 15] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 [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>.

Valmikam & Koodli Informational [Page 16] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

 [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>.

Valmikam & Koodli Informational [Page 17] RFC 7458 EAP Attributes for Wi-Fi - EPC Integration February 2015

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

Valmikam & Koodli Informational [Page 18]

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