Internet Engineering Task Force (IETF)                            S. Das
Request for Comments: 6153                        Telcordia Technologies
Category: Standards Track                                       G. Bajko
ISSN: 2070-1721                                                    Nokia
                                                          February 2011


                    DHCPv4 and DHCPv6 Options for
  Access Network Discovery and Selection Function (ANDSF) Discovery

Abstract

  This document defines new Dynamic Host Configuration Protocol (DHCPv4
  and DHCPv6) options to enable a mobile node to discover Access
  Network Discovery and Selection Function (ANDSF) entities in an IP
  network.  ANDSF is being developed in the Third Generation
  Partnership Project (3GPP) and provides inter-system mobility
  policies and access-network-specific information to the mobile nodes
  (MNs).

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/rfc6153.

Copyright Notice

  Copyright (c) 2011 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 ....................................................2
     1.1. Conventions Used in This Document ..........................3
     1.2. Terminology and Abbreviations Used in This Document ........3
  2. ANDSF IPv4 Address Option for DHCPv4 ............................3
  3. ANDSF IPv6 Address Option for DHCPv6 ............................4
  4. Option Usage ....................................................4
     4.1. Usage of ANDSF Options for DHCPv4 ..........................4
          4.1.1. Mobile Node Behavior ................................4
     4.2. Usage of ANDSF Options for DHCPv6 ..........................5
          4.2.1. Mobile Node Behavior ................................5
  5. Security Considerations .........................................5
  6. IANA Considerations .............................................5
  7. Acknowledgments .................................................6
  8. References ......................................................6
     8.1. Normative References .......................................6
     8.2. Informative References .....................................6

1.  Introduction

  Access Network Discovery and Selection Function (ANDSF) is being
  defined in 3GPP [3GPPTS23.402] to provide necessary network discovery
  and selection assistance data to the mobile nodes for multi-access
  network scenarios where 3GPP access-network level solutions are not
  sufficient for the mobile nodes to perform network discovery and
  selection of non-3GPP networks.

  The information provided by ANDSF contains inter-system mobility
  policies and access-network-specific data to assist the mobile node
  with performing the inter-system handover.  This set of information
  can either be provisioned in the mobile node by the home operator or
  provided to the mobile node (MN) dynamically by the ANDSF over the
  S14 reference point as defined in [3GPPTS23.402] and [3GPPTS24.302].

  In 3GPP, the ANDSF is located either in the subscriber's home
  operator or visited network and needs to be known to the MN or
  discovered by the MN.  According to [3GPPTS23.402] and
  [3GPPTS24.302], the ANDSF is discovered through interaction with the
  Domain Name Service function or the DHCP server function.

  This document defines new DHCPv4 and DHCPv6 options called the ANDSF
  IP Address Options, which allow the MN to locate an ANDSF server.








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1.1.  Conventions Used in This Document

  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].

1.2.  Terminology and Abbreviations Used in This Document

  ANDSF (Access Network Discovery and Selection Function): An entity
  that provides network discovery and selection assistance data to the
  user entity (UE) as per operator policy [3GPPTS23.402].

  Access Network: A network that is accessed by the UE.

  3GPP Network: A radio access network specified by Third Generation
  Partnership Project

  Non-3GPP Network: A radio access network specified outside 3GPP by
  other projects or standards organizations

2.  ANDSF IPv4 Address Option for DHCPv4

  This section describes the ANDSF IPv4 Address Option for DHCPv4.  The
  option layout is depicted below:

     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 Code   |    Length     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     IP Address                                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    .                                                               .
    +---------------------------------------------------------------+

  Option Code
     OPTION-IPv4_Address-ANDSF (142)

  Length
     Length (in bytes) of the option excluding the 'Option Code' and
     the 'Length' fields; 'Length' field is set to 4N, where N is the
     number of IPv4 addresses carried in the option

  IP Address
     IPv4 address(es) of ANDSF server(s)

  ANDSF servers MUST be listed in order of preference, and the client
  SHOULD process them in decreasing order of preference.




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3.  ANDSF IPv6 Address Option for DHCPv6

  This section describes the ANDSF IPv6 Address Option for DHCPv6.  All
  values in the option are represented in network byte order.  The
  option layout is depicted below:

     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 Code              |         Length                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                         IP Address                            |
    .                                                               .
    +---------------------------------------------------------------+

  Option Code
     OPTION-IPv6_Address-ANDSF (143)

  Length
     Length (in bytes) of the option excluding the 'Option Code' and
     the 'Length' fields; 'Length' field is set to 16N, where N is the
     number of IPv6 addresses carried in the option

  IP Address
     IPv6 address(es) of ANDSF server(s)

  ANDSF servers MUST be listed in order of preference, and the client
  SHOULD process them in decreasing order of preference.

4.  Option Usage

4.1.  Usage of ANDSF Options for DHCPv4

  The requesting and sending of the proposed DHCPv4 options follow the
  rules for DHCP options in [RFC2131].

4.1.1.  Mobile Node Behavior

  The mobile node MAY request the IP address of an ANDSF server either
  during initial association with a network or when the policy and
  access network information is required from ANDSF.  It MAY also
  request the IP address of an ANDSF server when the network
  information is outdated or the mobile node does not have any ANDSF
  information.

  In order to request an address of a ANDSF server, the mobile node
  (DHCP client) MUST include an ANDSF IPv4 Address Option in the
  Parameter Request List (PRL) in the respective DHCP messages as




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  defined in [RFC2131] and [RFC2132].  The DHCP client MAY initiate a
  new DHCP exchange or piggyback on other DHCP message exchanges.  DHCP
  client-handling PRL options are specified in [RFC2131], Section 4.4.

4.2.  Usage of ANDSF Options for DHCPv6

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

4.2.1.  Mobile Node Behavior

  The mobile node MAY request the IP address of an ANDSF server
  according to the scenarios described in Section 4.1.1.

  In order to discover the address of an ANDSF server, the mobile node
  (DHCP client) MUST include an ANDSF IPv6 Address Option in the Option
  Request Option (ORO) in the respective DHCP messages as defined in
  [RFC3315].  The DHCP client MAY initiate a new DHCP exchange or
  piggyback on other DHCP message exchanges.  DHCP client-handling ORO
  options are specified in [RFC3315], Sections 17.1 and 18.1.

5.  Security Considerations

  If an adversary manages to modify the response from a DHCP server or
  insert its own response, an MN could be led to contact a rogue ANDSF
  server.  A modified response could also be used to mount an
  amplification attack.

  The DHCP authentication option described in [RFC3118] and [RFC3315]
  MAY be used to mitigate the above attacks.  In deployments where DHCP
  authentication is not available, 3GPP-specific lower-layer security
  services can be used to protect DHCP messages [3GPPTS33.402].  The
  3GPP ANDSF framework also provides additional mechanisms that can be
  used to mitigate the above attacks and to protect message exchanges
  between an ANDSF client and server at the higher layer
  [3GPPTS33.402].

6.  IANA Considerations

  This document defines two new DHCP options as described in Sections 2
  and 3:

  ANDSF IPv4 Address Option for DHCPv4 (OPTION-IPv4_Address-ANDSF) 142

  ANDSF IPv6 Address Option for DHCPv6 (OPTION-IPv6_Address-ANDSF) 143






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7.  Acknowledgments

  The authors would like to acknowledge the following individuals for
  their valuable comments: Patrick Stuper, Vijay Devarapalli, Jouni
  Korhonen, Jari Arkko, Ted Lemon, and Ralph Droms.

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.

  [RFC2131]      Droms, R., "Dynamic Host Configuration Protocol", RFC
                 2131, March 1997.

  [RFC2132]      Alexander, S. and R. Droms, "DHCP Options and BOOTP
                 Vendor Extensions", RFC 2132, March 1997.

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

  [RFC3118]      Droms, R., Ed., and W. Arbaugh, Ed., "Authentication
                 for DHCP Messages", RFC 3118, June 2001.

8.2.  Informative References

  [3GPPTS23.402] 3GPP TS 23.402, v8.8.0 (2009-12): Architecture
                 enhancements for non-3GPP accesses,
                 http://www.3gpp.org/ftp/Specs/html-info/23402.htm.

  [3GPPTS24.302] 3GPP TS 24.302, v8.4.1 (2009-12): Access to the 3GPP
                 Evolved Packet Core (EPC) via non-3GPP access
                 networks; Stage 3, http://www.3gpp.org/ftp/Specs/html-
                 info/24302.htm.

  [3GPPTS33.402] 3GPP TS 33.402, v8.6.0 (2009-12): 3GPP System
                 Architecture Evolution (SAE); Security aspects of
                 non-3GPP accesses, http://www.3gpp.org/ftp/Specs/html-
                 info/33402.htm.









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Authors' Addresses

  Subir Das
  Telcordia Technologies Inc.
  EMail: [email protected]


  Gabor Bajko
  Nokia
  EMail: [email protected]









































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