DHCP Options for Home Information Discovery in Mobile IPv6 (MIPv6)
RFC 6610

Internet Engineering Task Force (IETF)                           H. Jang
Request for Comments: 6610                                         KISTI
Category: Standards Track                                       A. Yegin
ISSN: 2070-1721                                                  Samsung
                                                            K. Chowdhury
                                               Radio Mobile Access, Inc.
                                                                 J. Choi
                                                                 Samsung
                                                                T. Lemon
                                                                 Nominum
                                                                May 2012

   DHCP Options for Home Information Discovery in Mobile IPv6 (MIPv6)

Abstract

   This document defines a DHCP-based scheme to enable dynamic discovery
   of Mobile IPv6 home network information.  New DHCP options are
   defined that allow a mobile node to request the home agent IP
   address, Fully Qualified Domain Name (FQDN), or home network prefix
   and obtain it via the DHCP response.

Status of This Memo

   This is an Internet Standards Track document.

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

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6610.

Copyright Notice

   Copyright (c) 2012 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

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RFC 6610         DHCPv6 for Home Info Discovery in MIPv6        May 2012

   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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
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   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. DHCP Options for Home Network/Agent Dynamic Discovery ...........4
      3.1. MIPv6 Home Network ID FQDN Option ..........................4
      3.2. Home Network Information Options ...........................5
           3.2.1. MIPv6 Visited Home Network Information Option .......5
           3.2.2. MIPv6 Identified Home Network Information Option ....6
           3.2.3. MIPv6 Unrestricted Home Network Information Option ..6
      3.3. MIPv6 Home Network Prefix Option ...........................7
      3.4. MIPv6 Home Agent Address Option ............................7
      3.5. MIPv6 Home Agent FQDN Option ...............................8
   4. Option Usage ....................................................9
      4.1. Mobile Node Behavior .......................................9
           4.1.1. Requesting MIPv6 Configuration ......................9
           4.1.2. Processing MIPv6 Configuration Information .........10
      4.2. Relay Agent Behavior ......................................11
      4.3. DHCP Server Behavior ......................................12
      4.4. Home Agent Discovery Using a Network Access Server ........12
   5. Security Considerations ........................................13
   6. IANA Considerations ............................................14
   7. Acknowledgments ................................................14
   8. References .....................................................14
      8.1. Normative References ......................................14
      8.2. Informative References ....................................15

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1.  Introduction

   Before a mobile node can engage in Mobile IPv6 signaling with a home
   agent, it should either know the IP address of the home agent via
   pre-configuration or dynamically discover it.  The Mobile IPv6
   specification [RFC6275] describes how home agents can be dynamically
   discovered by mobile nodes that know the home network prefix.  This
   scheme does not work when prefix information is not already available
   to the mobile node.  This document specifies extensions to DHCPv6
   [RFC3736] [RFC3315] to deliver the home agent information to the
   mobile node in the form of the IP address of the home agent or the
   Fully Qualified Domain Name (FQDN) [RFC1035] of the home agent.  The
   information delivered to the mobile node may also include the home
   prefix for the mobile node.  The solution involves defining new DHCP
   options to carry home network prefixes, home agent IP addresses, and
   FQDN information.  The mobile node MAY also use the home prefix to
   discover the list of home agents serving the home prefix using the
   Dynamic Home Agent Address Discovery mechanism specified in
   [RFC6275].

   As part of configuring the initial TCP/IP parameters, a mobile node
   can find itself a suitable home agent.  Such a home agent might
   reside in the access network to which the mobile node connects or in
   a home network with which the mobile node is associated.  A mobile
   node can indicate its home network identity when roaming to a visited
   network in order to obtain the MIPv6 bootstrap parameters from the
   home network.  As an example, the visited network may determine the
   home network of the mobile node based on the realm portion of the NAI
   (Network Access Identifier) [RFC4282] used in access authentication
   [RFC5447].

   The mobile node may or may not be connected to the "home" network
   when it attempts to learn Mobile IPv6 home network information.  This
   allows operators to centrally deploy home agents while being able to
   bootstrap mobile nodes that are already roaming.  This scenario also
   occurs when Hierarchical Mobile IPv6 (HMIPv6) [RFC5380] is used,
   where the mobile node is required to discover the MAP (a special home
   agent) that is located multiple hops away from the mobile node's
   attachment point.

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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   General mobility terminology can be found in [RFC3753].  The
   following additional terms, as defined in [RFC4640], are used in this
   document:

   Access Service Provider (ASP):  A network operator that provides
      direct IP packet forwarding to and from the mobile node.

   Mobility Service Provider (MSP):  A service provider that provides
      Mobile IPv6 service.  In order to obtain such service, the mobile
      node must be authenticated and authorized to use the Mobile IPv6
      service.

   Mobility Service Authorizer (MSA):  A service provider that
      authorizes Mobile IPv6 service.

3.  DHCP Options for Home Network/Agent Dynamic Discovery

   This section introduces new DHCP options that are used for dynamic
   discovery of the home agent's IPv6 address, IPv6 home network prefix,
   or FQDN information in Mobile IPv6.  Transport to a home agent over
   IPv4 is also supported by specifying an IPv4-Embedded IPv6 address.
   The detailed procedures are described in Section 2.3.2 of "Mobile
   IPv6 Support for Dual Stack Hosts and Routers" [RFC5555].

   The names of options listed in this section all start with MIPv6, in
   order to differentiate them from other DHCP options that might have
   similar names.  However, throughout the rest of this document, the
   options are referred to by name without the MIPv6 prefix, for
   brevity.

3.1.  MIPv6 Home Network ID FQDN Option

   This option is used by mobile nodes to communicate to the DHCP server
   an FQDN that identifies the target home network for which the client
   is requesting configuration information.  When the mobile node
   requests configuration for more than one target home network, this
   option is also used by the server to identify the target home network
   for each Identified Home Network Information option returned.

   When a mobile node sends this option to request information about a
   specific home network, the option is simply included in the DHCP
   message from the mobile node.  When a server responds with an
   Identified Home Network Information option, this option MUST be
   encapsulated in the Identified Home Network Information option that
   it identifies.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       OPTION_MIP6_HNIDF       |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                 Home Network Identifier FQDN                  |
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-code:  OPTION_MIP6_HNIDF (49)

   Option-len:  Length of option, per RFC 3315

   Home Network Identifier FQDN:  A Fully Qualified Domain Name (FQDN)
      that identifies a mobile IP home network for which the client is
      seeking configuration information.  This is encoded in accordance
      with RFC 3315, Section 8, "Representation and Use of Domain
      Names".

3.2.  Home Network Information Options

   There are three different options that specify home network
   information.  Which of these options is used depends on what kind of
   home network information the client needs.  Each of these options is
   used to encapsulate options containing prefix and home agent
   information about the home network for which configuration
   information was requested.

3.2.1.  MIPv6 Visited Home Network Information Option

   This option is used by relay agents and DHCP servers to provide
   information about the local home network.

    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_MIP6_VDINF       |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                            Options                            |
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Option-code:  OPTION_MIP6_VDINF (50)

   Option-len:  Length of option, per RFC 3315

   Options:  One or more options, specifying information about the local
             ASP (visited domain).

3.2.2.  MIPv6 Identified Home Network Information Option

   This option is used by relay agents and DHCP servers to provide
   information about the home network identified by a Home Network
   Identifier FQDN 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_MIP6_IDINF       |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                            Options                            |
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-code:  OPTION_MIP6_IDINF (69)

   Option-len:  Length of option, per RFC 3315

   Options:  One or more options, specifying information about the home
             network identified by a Home Network Identifier FQDN option
             sent by a mobile node.

3.2.3.  MIPv6 Unrestricted Home Network Information Option

   This option is used by relay agents and DHCP servers to provide
   information about the a home network specified by the DHCP server
   administrator.

    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_MIP6_UDINF       |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                            Options                            |
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Option-code:  OPTION_MIP6_UDINF (70)

   Option-len:  Length of option, per RFC 3315

   Options:  One or more options, specifying information about some home
             network as specified by the DHCP server administrator.

3.3.  MIPv6 Home Network Prefix Option

   This option is used by DHCP servers and relay agents to define the
   prefix for a home network.  This option should only appear in one of
   the Home Network Information options.

    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_MIP6_HNP        |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Prefix-len   |                                               |
   +-+-+-+-+-+-+-+-+                                               +
   |                                                               |
   |                           Prefix                              |
   |                                                               |
   |                                                 +-+-+-+-+-+-+-+
   |                                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-code:  OPTION_MIP6_HNP (71)

   Option-len:  Length of option, per RFC 3315

   Prefix-len:  Length of prefix

   Prefix:  Home Network Prefix

3.4.  MIPv6 Home Agent Address Option

   This option is used by DHCP servers and relay agents to specify the
   home agent IP address.  In cases where the home agent must be
   contacted over an IPv4-only infrastructure, the IPv4 address is
   specified as an IPv4-Embedded IPv6 address using the "Well-Known
   Prefix" [RFC6052].  This option should only appear in one of the Home
   Network Information options.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        OPTION_MIP6_HAA        |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                                                               |
   |                           Address                             |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-code:  OPTION_MIP6_HAA (72)

   Option-len:  Length of option, per RFC 3315

   Address:  IP Address of home agent

3.5.  MIPv6 Home Agent FQDN Option

   This option is used by DHCP servers and relay agents to specify the
   home agent FQDN.  This FQDN is used to look up one or more A or AAAA
   records containing IPv4 or IPv6 addresses for the home agent, as
   needed.  This option should only appear in one of the Home Network
   Information options.

    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_MIP6_HAF        |           Option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                                                               |
   |                             FQDN                              |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Option-code:  OPTION_MIP6_HAF (73)

   Option-len:  Length of option, per RFC 3315

   Address:  FQDN resolving to one or more IPv4 and/or IPv6 addresses
             for the home agent.  This is encoded in accordance with RFC
             3315, Section 8, "Representation and Use of Domain Names".

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4.  Option Usage

   The requesting and sending of the proposed DHCP options follow the
   rules for DHCPv6 options in [RFC3315].

4.1.  Mobile Node Behavior

   Mobile nodes MAY obtain MIPv6 configuration information during either
   a stateful configuration exchange [RFC3315] or a stateless
   configuration exchange [RFC3736].

   Mobile nodes that obtain MIPv6 configuration information using a
   stateful configuration exchange SHOULD include the same options in
   every message they send to the DHCP server.

   Mobile nodes that obtain MIPv6 configuration using a stateless
   exchange MAY omit MIPv6 configuration from some exchanges, but SHOULD
   reconfigure whenever a change in the attached network is detected.
   If the DHCP server responds to a MIPv6-related stateless
   configuration request with an Information Request Timer option, the
   mobile node SHOULD attempt to reconfigure when the IRT expires.

   A mobile node using stateless configuration may try to perform home
   network information discovery when it lacks home network information
   for MIPv6 or needs to change the home agent for some reason.  For
   example, this may be necessary to recover from the failure of an
   existing home agent or to use the local home agent located in the
   network where the mobile node is currently attached.  Note that
   despite the home information discovery procedure, the mobile node may
   continue to use the old home agent, in order to avoid losing current
   sessions.

4.1.1.  Requesting MIPv6 Configuration

   Mobile nodes signal that they are interested in being configured with
   MIPv6 home agent information by requesting one or more of the three
   Home Network Information options: the Visited Home Network
   Information option, the Identified Home Network Information option,
   or the Unrestricted Home Network Information option.  To request
   these options, the client lists them in the Option Request Option
   (ORO).  A client that requests any of these three options in the ORO
   MUST also request the Home Network Identifier FQDN option, the Home
   Network Prefix option, the Home Agent Address option, and the Home
   Agent FQDN option.

   If the mobile node requests the Visited Home Network Information
   option, this indicates that it is interested in learning the home

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   network information that pertains to the currently visited network.
   This type can be used to discover local home agents in the local ASP.

   If the mobile node requests the Identified Home Network Information
   option, this indicates that it is interested in learning the home
   network information that pertains to a specified realm.  This type
   can be used to discover home agents that are hosted by a user's home
   domain or by any target domain.  A mobile node requesting the
   Identified Home Network Information option MUST include a Client Home
   Network ID FQDN option identifying the MSP being identified.  The
   target MSP can be a mobile node's home MSP or any MSP that has a
   trusted roaming relationship with the mobile node's MSA.

   If the mobile node has no preference as to the home network with
   which it should be configured, it SHOULD request the Unrestricted
   Home Network Information option, and SHOULD NOT request either the
   Visited Home Network Information option or the Identified Home
   Network Information option.

   A client that wishes to be configured with both the Visited Home
   Network Information option and the Identified Home Network
   Information option may request both options in the Option Request
   Option.  A client may request information about more than one
   identified domain by requesting the Identified Home Network
   Information option in the ORO and including more than one Home
   Network ID FQDN option.  A client that sends more than one Home
   Network ID FQDN option MUST request the Home Network ID option in the
   ORO.

4.1.2.  Processing MIPv6 Configuration Information

   DHCP Clients on mobile nodes should be prepared to receive any MIPv6
   Home Network Information options they request.  If more than one Home
   Network ID FQDN option was sent, the client should be prepared to
   handle zero or more Identified Home Network Information options in
   response; the DHCP server may not have configuration information for
   all targeted domains, or, indeed, for any.  If a misconfigured server
   returns an Identified Home Network Information option that does not
   contain a Home Network ID FQDN option corresponding to one that the
   client requested, the client MUST silently discard that Identified
   Home Network Information option.

   If any of the three Home Network Information options is returned,
   configuration information will be included within it.  The client
   must be prepared to handle home agent addresses in the form of either
   the Home Agent Address option or the Home Agent FQDN option.

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   If the client finds an IPv4-Embedded IPv6 address in a Home Agent
   Address option, it may only use this address to communicate over
   IPv4.  If a Home Network Information option does not contain complete
   configuration information, the client MUST silently discard that Home
   Network Information option.

   If the client receives any Home Network ID FQDN options, Home Network
   Prefix options, Home Agent Address options, or Home Agent FQDN
   options that are not encapsulated in one of the three types of Home
   Network Information options, it MUST silently discard these options.

   The DHCP client must pass whatever configuration information it
   receives to the appropriate mobile IP implementation on the mobile
   node.  How this is done, and what the mobile IP implementation on the
   mobile node does with this information, is outside the scope of this
   document.

   As described later in this section, servers may provide more than one
   Home Network Information option or multiple Home Agent Prefix, Home
   Agent Address, or Home Agent FQDN options.  When provided with
   multiple Visited Home Network Information options or Unrestricted
   Home Network Information options of the same type, or with multiple
   sub-options within such an option, the mobile node SHOULD choose the
   first one that it can employ.

   If the DHCP client on a mobile node receives any Home Network Prefix
   options, Home Agent Address option, or Home Agent FQDN option that
   are not contained within Home Network Information options, the DHCP
   client MUST silently discard these options.

4.2.  Relay Agent Behavior

   In some cases, DHCP relay agents may have access to configuration
   information for the mobile node.  In such cases, relay agents MAY
   send Visited Home Network Information options, Identified Home
   Network Information options, and/or Unrestricted Home Network
   Information options to the DHCP server.  To do so, the relay agent
   MUST encapsulate these options in a Relay-Supplied Options option
   [RFC6422].  If the DHCP relay agent includes any Identified Home
   Network Information options, these options MUST correspond to home
   networks identified in Home Network ID FQDN options in the client
   request.  In addition, each Identified Home Network Information
   option must contain a Home Network ID FQDN option identical to the
   one sent by the client, to identify the network to the client.

   No special handling is required when processing relay-reply messages.

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4.3.  DHCP Server Behavior

   Generally, DHCP servers can simply be configured with Visited Home
   Network Information options, Identified Home Network Information
   options, and Unrestricted Home Network Information options.  In the
   case of Visited Home Network Information options and Unrestricted
   Home Network Information options, which clients get what options
   depends on operator configuration.

   A DHCP server MAY maintain a table of Home Network ID FQDNs.  For
   each such FQDN, a server that maintains such a table SHOULD include
   an Identified Home Network Information option.  Such a server would
   look up the FQDN from any Home Network ID FQDN options provided by
   the client in its table, and for each match, include the Identified
   Home Network Information option configured in the table entry for
   that FQDN.

   If a DHCP server does not implement the Home Network ID FQDN table,
   or some similar functionality, it is an error for the operator to
   configure it with any Identified Home Network Information options.
   These options could be erroneously forwarded to the client, which
   would have no use for them, and is required to discard them.

   DHCP servers that implement the Home Network ID FQDN table must, when
   sending an Identified Home Network Information option to the client,
   include a Home Network ID option within the Identified Home Network
   Information option that identifies the home network for which
   configuration information is being sent.

   Aside from the Home Network ID FQDN table, the actual behavior of the
   DHCP server with respect to MIPv6 configuration is simply in
   accordance with the DHCPv6 protocol specification [RFC3315] and
   depends on operator configuration.  No special processing is required
   for Visited Home Network Information options or Unrestricted Home
   Network Information options.

4.4.  Home Agent Discovery Using a Network Access Server

   [RFC5447] describes the complete procedure for home agent assignment
   among the mobile node, NAS (Network Access Server), DHCP, and
   Authentication, Authorization, and Accounting (AAA) entities for the
   bootstrapping procedure in the integrated scenario.

   A NAS is assumed to be co-located with a DHCP relay agent or a DHCP
   server in this solution.  In a network where the NAS is not
   co-located with a DHCP relay or a server, the server may not be
   provided with the home network information from the NAS; therefore,

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   it may either fail to provide information or provide home information
   that has been pre-configured by the administrator or that is acquired
   through a mechanism that is not described in this document.

5.  Security Considerations

   Secure delivery of home agent and home network information from a
   DHCP server to the mobile node (DHCP client) relies on the same
   security as DHCP.  The particular option defined in this document
   does not have additional impact on DHCP security.

   Aside from the DHCP client-to-server interaction, an operator must
   also ensure secure delivery of mobile IP information to the DHCP
   server.  This is outside the scope of DHCP and the newly defined
   options.

   The mechanisms in this specification could be used by attackers to
   learn the addresses of home agents in the home network or to feed
   incorrect information to mobile nodes.

   The ability to learn addresses of nodes may be useful to attackers
   because brute-force scanning of the address space is not practical
   with IPv6.  Thus, they could benefit from any means that make mapping
   the networks easier.  For example, if a security threat targeted at
   routers or even home agents is discovered, having a simple mechanism
   to easily find out possible targets may prove to be an additional
   security risk.

   Apart from discovering the address(es) of home agents, attackers will
   not be able to learn much from this information, and mobile nodes
   cannot be tricked into using wrong home agents, as the actual
   communication with the home agents employs mutual authentication.

   The mechanisms from this specification may also leak interesting
   information about network topology and prefixes to attackers, and
   where there is no security to protect DHCP, even modify this
   information.  Again, the mobile nodes and home agents employ end-to-
   end security when they communicate with each other.  The authentic
   source of all information is that communication, not the information
   from DHCP.

   However, attacks against the information carried in DHCP may lead to
   denial of service if mobile nodes are unable to connect to any home
   agent, or choose a home agent that is not the most preferred one.

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6.  IANA Considerations

   IANA has assigned the following new DHCPv6 Option Codes in the
   registry maintained in

   http://www.iana.org/assignments/dhcpv6-parameters:

      49: OPTION_MIP6_HNIDF for the Home Network ID FQDN option

      50: OPTION_MIP6_VDINF for the Visited Home Network Information
          option

      69: OPTION_MIP6_IDINF for the Identified Home Network Information
          option

      70: OPTION_MIP6_UDINF for the Unrestricted Home Network
          Information option

      71: OPTION_MIP6_HNP for the Home Network Prefix option

      72: OPTION_MIP6_HAA for the Home Agent Address option

      73: OPTION_MIP6_HAF for the Home Agent FQDN option

7.  Acknowledgments

   The authors would like to thank Kilian Weniger, Domagoj Premec,
   Basavaraj Patil, Vijay Devarapalli, Gerardo Giaretta, Bernie Volz,
   David W. Hankins, Behcet Sarikaya, Vidya Narayanan, Francis Dupont,
   Sam Weiler, Jari Arkko, Alfred Hoenes, Suresh Krishnan, and Miguel A.
   Diaz for their valuable feedback.

8.  References

8.1.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.

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RFC 6610         DHCPv6 for Home Info Discovery in MIPv6        May 2012

   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282, December 2005.

   [RFC5555]  Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
              Routers", RFC 5555, June 2009.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
              in IPv6", RFC 6275, July 2011.

   [RFC6422]  Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options",
              RFC 6422, December 2011.

8.2.  Informative References

   [RFC3753]  Manner, J. and M. Kojo, "Mobility Related Terminology",
              RFC 3753, June 2004.

   [RFC4640]  Patel, A. and G. Giaretta, "Problem Statement for
              bootstrapping Mobile IPv6 (MIPv6)", RFC 4640,
              September 2006.

   [RFC5380]  Soliman, H., Castelluccia, C., ElMalki, K., and L.
              Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility
              Management", RFC 5380, October 2008.

   [RFC5447]  Korhonen, J., Bournelle, J., Tschofenig, H., Perkins, C.,
              and K. Chowdhury, "Diameter Mobile IPv6: Support for
              Network Access Server to Diameter Server Interaction",
              RFC 5447, February 2009.

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Authors' Addresses

   Heejin Jang
   Korea Institute of Science and Technology Information (KISTI)
   245 Daehak-ro, Yuseong-gu
   Daejeon 305-806
   Korea

   EMail: heejin.jang@gmail.com

   Alper E. Yegin
   Samsung Electronics
   Istanbul
   Turkey

   EMail: alper.yegin@yegin.org

   Kuntal Chowdhury
   Radio Mobile Access, Inc.
   100 Ames Pond Dr.
   Tewksbury, MA  01876
   US

   EMail: kc@radiomobiles.com

   JinHyeock Choi
   Samsung Advanced Institute of Technology
   P.O. Box 111
   Suwon 440-600
   Korea

   EMail: jinchoe@gmail.com

   Ted Lemon
   Nominum
   2000 Seaport Blvd
   Redwood City, CA  94063
   USA

   Phone: +1 650 381 6000
   EMail: Ted.Lemon@nominum.com

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