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RFC 7839

Proposed STD
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Access-Network-Identifier Option in DHCP

 


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Internet Engineering Task Force (IETF)                       S. Bhandari
Request for Comments: 7839                                 S. Gundavelli
Category: Standards Track                                     M. Grayson
ISSN: 2070-1721                                                  B. Volz
                                                           Cisco Systems
                                                             J. Korhonen
                                                        Broadcom Limited
                                                               June 2016


                Access-Network-Identifier Option in DHCP

Abstract

   This document specifies the format and mechanism that is to be used
   for encoding Access-Network Identifiers in DHCPv4 and DHCPv6 messages
   by defining new Access-Network-Identifier options and sub-options.

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 7841.

   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/rfc7839.

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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  DHCPv4 Access-Network-Identifier Option . . . . . . . . . . .   5
     4.1.  DHCPv4 Access-Network-Identifier Sub-options  . . . . . .   5
     4.2.  DHCPv4 Access-Technology-Type Sub-option  . . . . . . . .   6
     4.3.  DHCPv4 Network-Identifier Sub-options . . . . . . . . . .   7
       4.3.1.  DHCPv4 Network-Name Sub-option  . . . . . . . . . . .   7
       4.3.2.  DHCPv4 Access-Point-Name Sub-option . . . . . . . . .   8
       4.3.3.  DHCPv4 Access-Point-BSSID Sub-option  . . . . . . . .   9
     4.4.  DHCPv4 Operator-Identifier Sub-options  . . . . . . . . .   9
       4.4.1.  DHCPv4 Operator-Identifier Sub-option . . . . . . . .   9
       4.4.2.  DHCPv4 Operator-Realm Sub-option  . . . . . . . . . .  10
   5.  DHCPv6 Access-Network-Identifier Options  . . . . . . . . . .  10
     5.1.  DHCPv6 Access-Technology-Type Option  . . . . . . . . . .  11
     5.2.  DHCPv6 Network-Identifier Options . . . . . . . . . . . .  11
       5.2.1.  DHCPv6 Network-Name Option  . . . . . . . . . . . . .  12
       5.2.2.  DHCPv6 Access-Point-Name Option . . . . . . . . . . .  12
       5.2.3.  DHCPv6 Access-Point-BSSID Option  . . . . . . . . . .  13
     5.3.  DHCPv6 Operator-Identifier Options  . . . . . . . . . . .  13
       5.3.1.  DHCPv6 Operator-Identifier Option . . . . . . . . . .  13
       5.3.2.  DHCPv6 Operator-Realm Option  . . . . . . . . . . . .  14
   6.  Relay Agent Behavior  . . . . . . . . . . . . . . . . . . . .  14
   7.  Server Behavior . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     10.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

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1.  Introduction

   Access-network identification of a network device has a range of
   applications.  For example, the Local Mobility Anchor (LMA) in a
   Proxy Mobile IPv6 (PMIPv6) domain is able to provide service
   treatment for the mobile node's traffic based on the access network
   to which the mobile node is attached.

   This document specifies the Dynamic Host Configuration Protocol for
   IPv4 (DHCPv4) [RFC2131] and the Dynamic Host Configuration Protocol
   for IPv6 (DHCPv6) [RFC3315] options for access-network identification
   that is added by the relay agent in the DHCPv4 or DHCPv6 messages
   sent towards the server.  The scope of applicability for this option
   is between a DHCP relay agent and a mobile access gateway where the
   same operator typically operates both these functions

   A DHCP relay agent that is aware of the access network and access
   operator adds this information in the DHCP messages.  This
   information can be used to provide differentiated services and
   policing of traffic based on the access network to which a client is
   attached.  Examples of how this information can be used in mobile
   networks can be found in [RFC6757].

2.  Motivation

   PMIPv6 [RFC5213] can be used for supporting network-based mobility
   management in various types of network deployments.  The network
   architectures, such as service provider Wi-Fi access aggregation or
   WLAN integrated mobile packet core, are examples where PMIPv6 is a
   component of the overall architecture.  Some of these architectures
   require the ability of the LMA [RFC5213] to provide differentiated
   services and policing of traffic to the mobile nodes based on the
   access network to which they are attached.  Policy systems in
   mobility architectures, such as Policy and Charging Control (PCC)
   [TS23203] and Access Network Discovery and Selection Function (ANDSF)
   [TS23402] in the 3GPP system, allow configuration of policy rules
   with conditions based on the access-network information.  For
   example, the service treatment for the mobile node's traffic may be
   different when they are attached to an access network owned by the
   home operator than when owned by a roaming partner.  In the case of
   access networks based on IEEE 802.11, the service treatment can also
   be different based on the configured Service Set Identifiers (SSIDs).
   Other examples of services include the operator's ability to apply
   tariff based on the location.

   The PMIPv6 extension as specified in [RFC6757] defines PMIPv6 options
   to carry Access-Network Identifiers in PMIPv6 signaling from the
   Mobile Access Gateway (MAG) to the LMA.  The MAG can learn this

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   information from the DHCP options as inserted by the DHCP relay agent
   in the access network.  If the MAG relays the DHCP messages to the
   LMA as specified in [RFC5844], this information can be inserted by
   the MAG towards the LMA in the forwarded DHCP messages.

   Figure 1 illustrates an example of PMIPv6 deployment.  In this
   example, the access network is based on IEEE 802.11 technology, the
   DHCP relay agent function is located on the Access Point (AP), and
   the DHCP server function is located on the MAG.  The MAG delivers the
   information elements related to the access network to the LMA over
   PMIPv6 signaling messages.  The MAG obtains these information
   elements from the DHCP relay agent as per this specification.  The
   information elements related to the access network include the SSID
   of the used IEEE 802.11 network, the geo-location of the access
   network to which the mobile node is attached, and the identity of the
   operator running the IEEE 802.11 access-network infrastructure.

          SSID: IETF-1
          Operator-Identifier: provider1.example

          +--+
          |AP|-----------.                    {Access-Specific Policies)
          +--+           | (DHCP Server)   _-----_             |
          (DHCP Relay) +-----+           _(       )_        +-----+
                       | MAG |-=========(   PMIPv6  )======-| LMA |-
                       +-----+           (_ Tunnel_)        +-----+
          +--+           |                 '-----'
          |AP|-----------'
          +--+
          (DHCP Relay)

          SSID: IETF-2
          Operator-Identifier: provider2.example

                      Access Networks Attached to MAG

3.  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].

   All the DHCP-related terms used in this document are to be
   interpreted as defined in DHCPv4 [RFC2131] and DHCPv6 [RFC3315]
   specifications.  "DHCP message" refers to both DHCPv4 and DHCPv6
   messages throughout this document.

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   All the mobility-related terms used in this document are to be
   interpreted as defined in the PMIPv6 specifications [RFC5213] and
   [RFC5844].  Additionally, this document uses the following
   abbreviations:

   Service Set Identifier (SSID)

      The Service Set Identifier (SSID) identifies the name of the IEEE
      802.11 network.  The SSID differentiates from one network to the
      other.

   Operator-Identifier

      The Operator-Identifier is the Structure of Management Information
      (SMI) Network Management Private Enterprise Code of the IANA-
      maintained "Private Enterprise Numbers" registry [SMI].  It
      identifies the operator running the access network where the
      client is attached.

4.  DHCPv4 Access-Network-Identifier Option

   The Access-Network Identifier (ANI) carries information related to
   the identity of the access network to which the client is attached.
   This information includes access-technology type, network identifier,
   and access network operator identifiers.

   Relay agents that include ANI information include one or more sub-
   options (see Section 4.1) in the Relay Agent Information option
   [RFC3046].

4.1.  DHCPv4 Access-Network-Identifier Sub-options

   The Access-Network-Identifier information will be defined in multiple
   sub-options allocated from the "DHCP Relay Agent Sub-Option Codes"
   registry.

   ANI Sub-options: The ANI sub-options consist of a sequence of Sub-
   Option Code, Length, and Value tuples for each sub-option, encoded in
   the following manner:

       Subopt  Len     Sub-option Data
      +------+------+------+------+------+------+--...-+------+
      | code |   N  |  s1  |  s2  |  s3  |  s4  |      |  sN  |
      +------+------+------+------+------+------+--...-+------+

   Subopt code
      The 1-octet code for the sub-options defined in the following
      sections.

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   Len
      An unsigned 8-bit integer giving the length of the Sub-option Data
      field in this sub-option in octets.

   Sub-option Data (s1 to sN)
      The data area for the sub-option.

   The initial assignment of the DHCP Access-Network-Identifier sub-
   options is as follows:

      +=================+=======================================+
      | SUB-OPTION CODE |      SUB-OPTION DESCRIPTION           |
      +=================+=======================================+
      |       13        | Access-Technology-Type Sub-option     |
      +=========================================================+
      |       14        | Access-Network-Name Sub-option        |
      +=========================================================+
      |       15        | Access-Point-Name Sub-option          |
      +=========================================================+
      |       16        | Access-Point-BSSID Sub-option         |
      +=========================================================+
      |       17        | Operator-Identifier Sub-option        |
      +=========================================================+
      |       18        | Operator-Realm Sub-option             |
      +=========================================================+

4.2.  DHCPv4 Access-Technology-Type Sub-option

   This sub-option is used for exchanging the type of the access
   technology of the network to which the client is attached.  Its
   format is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |   Reserved    |      ATT      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      13

   Length
      2

   Reserved
      An 8-bit field that is unused for now.  The value MUST be
      initialized to 0 by the sender and MUST be ignored by the
      receiver.

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   Access-Technology-Type (ATT)
      An 8-bit field that specifies the access technology through which
      the client is connected to the access link from the IANA name
      space "Access Technology Type Option type values" registry defined
      in [RFC5213].

4.3.  DHCPv4 Network-Identifier Sub-options

   These sub-options are used for carrying the name of the access
   network (e.g., an SSID in the case of an IEEE 802.11 access network
   or a Public Land-based Mobile Network (PLMN) Identifier [TS23003] in
   the case of a 3GPP access network) and the Access-Point Name to which
   the client is attached.  The format of these sub-options is defined
   in the following sections.  The Network-Identifier sub-options are
   only for the currently known access-technology types.

4.3.1.  DHCPv4 Network-Name Sub-option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      .                                                               .
      .                     Network-Name (e.g., SSID or PLMNID)       .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      14

   Length
      The length of the Network-Name field.

   Network-Name
      The name of the access network to which the mobile node is
      attached.  The encoding MUST be UTF-8 as described in [RFC3629].

      The type of the Network-Name is dependent on the access technology
      to which the mobile node is attached.  For networks based on IEEE
      802.11, the Network-Name will be the SSID of the network.  For
      3GPP access-based networks, it is the PLMN Identifier of the
      access network, and for 3GPP2 access, the Network-Name is the ANI
      [ANI].

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      When encoding the PLMN Identifier, both the Mobile Network Code
      (MNC) [TS23003] and Mobile Country Code (MCC) [TS23003] MUST be
      three digits.  If the MNC in use only has two digits, then it MUST
      be preceded with a '0'.

4.3.2.  DHCPv4 Access-Point-Name Sub-option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      .                                                               .
      .                        Access-Point-Name                      .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      15

   Length
      The length of the Access-Point-Name field.

   Access-Point-Name
      The name of the access point (physical device name) to which the
      mobile node is attached.  This is the identifier that uniquely
      identifies the access point.  While the Network-Name (e.g., SSID)
      identifies the operator's access network, the Access-Point-Name
      identifies a specific network device in the network to which the
      mobile node is attached.  In some deployments, the Access-Point-
      Name can be set to the string representation of the Media Access
      Control (MAC) address of the device as specified in [RFC6991] (see
      mac-address typedef) or some unique identifier that can be used by
      the policy systems in the operator network to unambiguously
      identify the device.  The encoding MUST be UTF-8 as described in
      [RFC3629].

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4.3.3.  DHCPv4 Access-Point-BSSID Sub-option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      |                        Access-Point-BSSID                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      16

   Length
      6

   Access-Point-BSSID
      The 48-bit Basic SSSID (BSSID) of the access point to which the
      mobile node is attached.

4.4.  DHCPv4 Operator-Identifier Sub-options

   The Operator-Identifier sub-options can be used for carrying the
   Operator-Identifiers of the access network to which the client is
   attached.  The format of these sub-options is defined below.

4.4.1.  DHCPv4 Operator-Identifier Sub-option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .      Operator-Identifier      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      17

   Length
      4

   Operator-Identifier
      The Operator-Identifier is a variable-length Private Enterprise
      Number (PEN) [SMI] encoded in a network byte order.  Please refer
      to Section 3.1.3 of [RFC6757] for additional details.

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4.4.2.  DHCPv4 Operator-Realm Sub-option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Subopt Code  |     Length    |                               |
      |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
      .                                                               .
      .                        Operator-Realm                         .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Subopt Code
      18

   Length
      The length of the Operator-Realm field.

   Operator-Realm
      Realm of the operator (e.g., EXAMPLE.COM).  Please refer to
      Section 3.1.3 of [RFC6757] for additional details.

5.  DHCPv6 Access-Network-Identifier Options

   The Access-Network-Identifier options defined here may be added by
   the DHCPv6 relay agent in Relay-forward messages.

      +=================+=======================================+
      |    OPTION CODE  |      OPTION DESCRIPTION               |
      +=================+=======================================+
      |       105       | OPTION_ANI_ATT                        |
      +=========================================================+
      |       106       | OPTION_ANI_NETWORK_NAME               |
      +=========================================================+
      |       107       | OPTION_ANI_AP_NAME                    |
      +=========================================================+
      |       108       | OPTION_ANI_AP_BSSID                   |
      +=========================================================+
      |       109       | OPTION_ANI_OPERATOR_ID                |
      +=========================================================+
      |       110       | OPTION_ANI_OPERATOR_REALM             |
      +=========================================================+

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5.1.  DHCPv6 Access-Technology-Type Option

   This option is used for exchanging the type of access technology the
   client uses to attach to the network.  Its format is as follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         OPTION_ANI_ATT        |           Option-Len          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Reserved    |       ATT     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_ATT (105)

   Option-Len
      2

   Reserved
      An 8-bit field that is unused for now.  The value MUST be
      initialized to 0 by the sender and MUST be ignored by the
      receiver.

   Access-Technology-Type (ATT):
      The contents of this field are the same as the ATT field described
      in Section 4.2.

5.2.  DHCPv6 Network-Identifier Options

   These options can be used for carrying the name of the access network
   (e.g., an SSID in the case of an IEEE 802.11 access network or a PLMN
   Identifier [TS23003] in the case of a 3GPP access network) and an
   Access-Point Name to which the client is attached.  The format of
   these options is defined below.

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5.2.1.  DHCPv6 Network-Name Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    OPTION_ANI_NETWORK_NAME    |           Option-Len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                     Network-Name (e.g., SSID or PLMNID)       .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_NETWORK_NAME (106)

   Option-Len
      The length of the Network-Name field.

   Network-Name
      The contents of this field are the same as the Network-Name field
      described in Section 4.3.1.

5.2.2.  DHCPv6 Access-Point-Name Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       OPTION_ANI_AP_NAME      |           Option-Len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                        Access-Point-Name                      .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_AP_NAME (107)

   Option-Len
      The length of the Access-Point-Name field.

   Access-Point-Name
      The contents of this field are the same as the Access-Point-Name
      field described in Section 4.3.2.

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5.2.3.  DHCPv6 Access-Point-BSSID Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       OPTION_ANI_AP_BSSID     |           Option-Len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Access-Point-BSSID                     |
      +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_AP_BSSID (108)

   Option-Len
      6

   Access-Point-BSSID
      The contents of this field are the same as the Access-Point-BSSID
      field described in Section 4.3.3.

5.3.  DHCPv6 Operator-Identifier Options

   The Operator-Identifier options can be used for carrying the
   Operator-Identifier of the access network to which the client is
   attached.  The format of these options is defined below.

5.3.1.  DHCPv6 Operator-Identifier Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     OPTION_ANI_OPERATOR_ID    |           Option-Len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Operator-Identifier                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_OPERATOR_ID (109)

   Option-Len
      4

   Operator-Identifier
      The contents of this field are the same as the DHCPv4 Operator-
      Identifier Sub-option field described in Section 4.4.1.

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5.3.2.  DHCPv6 Operator-Realm Option

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   OPTION_ANI_OPERATOR_REALM   |           Option-Len          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      .                                                               .
      .                        Operator-Realm                         .
      .                                                               .
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-Code
      OPTION_ANI_OPERATOR_REALM (110)

   Option-Len
      The length of the Operator-Realm field.

   Operator-Realm
      The contents of this field are the same as the Operator-Realm
      field described in Section 4.4.2.

6.  Relay Agent Behavior

   DHCPv4 relay agents MAY include sub-options as defined in Section 4.2
   through 4.4 of [RFC3046] in the Relay Agent Information option for
   providing information about the access network over which DHCP
   messages from the client are received.

   The DHCPv4 relay agent MUST include the DHCPv4 Access-Technology-Type
   Sub-option (Section 4.2) when including any of these sub-options in
   the DHCP message: DHCPv4 Network-Name Sub-option (Section 4.3.1),
   DHCPv4 Access-Point-Name Sub-option (Section 4.3.2), and DHCPv4
   Access-Point-BSSID Sub-option (Section 4.3.3).

   DHCPv6 Relay Agents MAY include options (defined in Section 5) in the
   Relay-forward message when forwarding any DHCPv6 message type from
   clients to the servers to provide information about the access
   network over which DHCPv6 messages from the client are received.

   The DHCPv6 relay agent MUST include the DHCPv6 Access-Technology-Type
   Option (Section 5.1) when including any of these options in the DHCP
   message: DHCPv6 Network-Name Option (Section 5.2.1), DHCPv6 Access-
   Point-Name Option (Section 5.2.2), and DHCPv6 Access-Point-BSSID
   Option (Section 5.2.3).

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7.  Server Behavior

   The DHCPv4 base specification [RFC2131] requires that the DHCPv4
   server ignore the DHCPv4 Access-Network-Identifier Option if it does
   not understand the option.

   If the DHCPv4 server does not understand the received sub-option
   defined in Sections 4.1 through 4.4 of [RFC3046], the DHCPv4 Relay-
   Agent-Information Option, it MUST ignore those sub-options only.  If
   the DHCPv4 server is able to process the DHCPv4 Access-Network-
   Identifier sub-options defined in Sections 4.1 through 4.4 of
   [RFC3046], the DHCPv4 Relay-Agent-Information Option, it MAY use this
   information obtained from the sub-option for address pool selection
   or for policy decisions as per its configured policy.  This
   information obtained from the sub-option SHOULD NOT be stored unless
   it is absolutely needed.  However, if it is stored, the information
   MUST be deleted as quickly as possible to eliminate any possibility
   of the information getting exposed to an intruder.

   The DHCPv4 server MUST ignore the received DHCPv4 Access-Network-
   Identifier Option and process the rest of the message as per the base
   DHCPv4 specifications if the received DHCPv4 message does not include
   the DHCPv4 Access-Technology-Type Sub-option (Section 4.2) but does
   include any one of these other options: DHCPv4 Network Name Sub-
   option (Section 4.3.1), DHCPv4 Access-Point-Name Sub-option
   (Section 4.3.2), or DHCPv4 Access-Point-BSSID Sub-option
   (Section 4.3.3).

   DHCPv6 base specification [RFC3315] requires that the DHCPv6 server
   ignore the DHCPv6 Access-Network-Identifier Option if it does not
   understand the option.

   If the DHCPv6 server receives the options defined in Section 5 and is
   configured to use the options defined in Section 5, it SHOULD look
   for the DHCPv6 Access-Network-Identifier options in the Relay-forward
   message of the DHCPv6 relay agent(s) based on its configured policy.
   The server MAY use received ANI options for its address pool
   selection policy decisions as per its configured policy.  This
   information obtained from the options SHOULD NOT be stored unless it
   is absolutely needed.  However, if it is stored, the information MUST
   be deleted as quickly as possible to eliminate any possibility of the
   information getting exposed to an intruder.

   The DHCPv6 server MUST ignore the received DHCPv6 Access-Network-
   Identifier Option and process the rest of the message as per the base
   DHCPv6 specifications if the received DHCPv6 message does not include
   the DHCPv6 Access-Technology-Type Option (Section 5.1) but it does
   includes any one of these other options: DHCPv6 Network-Name Option

Top      ToC       Page 16 
   (Section 5.2.1), DHCPv6 Access-Point-Name Option (Section 5.2.2), or
   DHCPv6 Access-Point-BSSID Option (Section 5.2.3).

8.  IANA Considerations

   IANA has assigned sub-option codes for the following DHCPv4 sub-
   options from the "DHCP Relay Agent Sub-Option Codes" registry,
   <http://www.iana.org/assignments/bootp-dhcp-parameters>:

      +=================+=======================================+
      | SUB-OPTION CODE |     SUB-OPTION DESCRIPTION            |
      +=================+=======================================+
      |       13        | Access-Technology-Type Sub-option     |
      +=========================================================+
      |       14        | Access-Network-Name Sub-option        |
      +=========================================================+
      |       15        | Access-Point-Name Sub-option          |
      +=========================================================+
      |       16        | Access-Point-BSSID Sub-option         |
      +=========================================================+
      |       17        | Operator-Identifier Sub-option        |
      +=========================================================+
      |       18        | Operator-Realm Sub-option             |
      +=========================================================+

   IANA has assigned option codes for the following DHCPv6 options from
   the "Option Codes" registry for DHCPv6,
   <http://www.iana.org/assignments/dhcpv6-parameters>, as specified in
   [RFC3315]:

      +=================+=======================================+
      |   OPTION CODE   |      OPTION DESCRIPTION               |
      +=================+=======================================+
      |       105       | OPTION_ANI_ATT                        |
      +=========================================================+
      |       106       | OPTION_ANI_NETWORK_NAME               |
      +=========================================================+
      |       107       | OPTION_ANI_AP_NAME                    |
      +=========================================================+
      |       108       | OPTION_ANI_AP_BSSID                   |
      +=========================================================+
      |       109       | OPTION_ANI_OPERATOR_ID                |
      +=========================================================+
      |       110       | OPTION_ANI_OPERATOR_REALM             |
      +=========================================================+

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9.  Security Considerations

   Since there is no privacy protection for DHCP messages, an
   eavesdropper who can monitor the link between the DHCP server and
   relay agent can discover access-network information.

   [RFC3118] and [RFC3315] describe many of the threats in using DHCP.
   [RFC3118] and [RFC3315] each provide a solution; the Authentication
   Option for DHCPv4 and DHCPv6 (respectively).  However, neither of
   these options are in active use and therefore are not a viable
   mitigation option.  DHCP itself is inherently insecure and thus link-
   layer confidentiality and integrity protection SHOULD be employed to
   reduce the risk of disclosure and tampering.

   It is possible for a rogue DHCP relay agent to insert or overwrite
   with incorrect Access-Network-Identifier options for malicious
   purposes.  A DHCP client can also pose as a rogue DHCP relay agent by
   sending incorrect Access-Network-Identifier options.  While the
   introduction of fraudulent DHCP relay agent information options can
   be prevented by a perimeter defense that blocks these options unless
   the DHCP relay agent is trusted, a deeper defense using the
   authentication sub-option for the DHCPv4 Relay-Agent-Information
   Option [RFC4030] SHOULD be deployed as well.  Administrators SHOULD
   configure DHCP servers that use this option to communicate with their
   relay agents using IPsec, as described in Section 21.1 of [RFC3315].

   The information elements that this document is exposing are the
   client's access-network information.  These pertain to the access
   network to which the client is attached, such as Access-Technology
   Type (e.g., WLAN, Ethernet, etc.), Access-Point Identity (Name,
   BSSID), and Operator-Identifier and Operator-Realm.  In deployments
   where this information cannot be secured using IPsec [RFC4301] or
   other security protocols, administrators SHOULD disable the
   capability specified in this document on the DHCP entities.

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10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <http://www.rfc-editor.org/info/rfc2131>.

   [RFC3046]  Patrick, M., "DHCP Relay Agent Information Option",
              RFC 3046, DOI 10.17487/RFC3046, January 2001,
              <http://www.rfc-editor.org/info/rfc3046>.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

10.2.  Informative References

   [ANI]      "Interoperability Specification (IOS) for High Rate Packet
              Data (HRPD) Radio Access Network Interfaces with Session
              Control in the Access Network", 3GPP2 A.S0008-C v4.0,
              April 2011.

   [RFC3118]  Droms, R., Ed. and W. Arbaugh, Ed., "Authentication for
              DHCP Messages", RFC 3118, DOI 10.17487/RFC3118, June 2001,
              <http://www.rfc-editor.org/info/rfc3118>.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <http://www.rfc-editor.org/info/rfc3629>.

   [RFC4030]  Stapp, M. and T. Lemon, "The Authentication Suboption for
              the Dynamic Host Configuration Protocol (DHCP) Relay Agent
              Option", RFC 4030, DOI 10.17487/RFC4030, March 2005,
              <http://www.rfc-editor.org/info/rfc4030>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <http://www.rfc-editor.org/info/rfc4301>.

Top      ToC       Page 19 
   [RFC5213]  Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
              Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
              RFC 5213, DOI 10.17487/RFC5213, August 2008,
              <http://www.rfc-editor.org/info/rfc5213>.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010,
              <http://www.rfc-editor.org/info/rfc5844>.

   [RFC6757]  Gundavelli, S., Ed., Korhonen, J., Ed., Grayson, M.,
              Leung, K., and R. Pazhyannur, "Access Network Identifier
              (ANI) Option for Proxy Mobile IPv6", RFC 6757,
              DOI 10.17487/RFC6757, October 2012,
              <http://www.rfc-editor.org/info/rfc6757>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <http://www.rfc-editor.org/info/rfc6991>.

   [SMI]      IANA, "PRIVATE ENTERPRISE NUMBERS, SMI Network Management
              Private Enterprise Codes", March 2016,
              <https://www.iana.org/assignments/enterprise-numbers>.

   [TS23003]  3GPP, "Numbering, addressing and identification", 3GPP
              TS 23.003 13.4.0, December 2015.

   [TS23203]  3GPP, "Policy and charging control architecture", 3GPP
              TS 23.203 13.6.0, December 2015.

   [TS23402]  3GPP, "Architecture enhancements for non-3GPP accesses",
              3GPP TS 23.402 13.4.0, December 2015.

Acknowledgements

   The authors would like to thank Kim Kinnear, Ted Lemon, Gaurav
   Halwasia, Hidetoshi Yokota, Sheng Jiang, and Francis Dupont for their
   valuable input.  Also, thank you to Tomek Mrugalski for a thorough
   review of the document.

Top      ToC       Page 20 
Authors' Addresses

   Shwetha Bhandari
   Cisco Systems
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA  560 087
   India

   Phone: +91 80 4426 0474
   Email: shwethab@cisco.com


   Sri Gundavelli
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134
   United States

   Email: sgundave@cisco.com


   Mark Grayson
   Cisco Systems
   11 New Square Park
   Bedfont Lakes, FELTHAM  TW14 8HA
   England

   Email: mgrayson@cisco.com


   Bernie Volz
   Cisco Systems
   1414 Massachusetts Ave
   Boxborough, MA  01719
   United States

   Email: volz@cisco.com


   Jouni Korhonen
   Broadcom Limited
   3151 Zanker Rd
   San Jose, CA  95134
   United States

   Email: jouni.nospam@gmail.com