





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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RFC 6153                   ANDSF DHCP Options              February 2011


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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RFC 6153                   ANDSF DHCP Options              February 2011


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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RFC 6153                   ANDSF DHCP Options              February 2011


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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RFC 6153                   ANDSF DHCP Options              February 2011


   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: subir@research.telcordia.com


   Gabor Bajko
   Nokia
   EMail: gabor@bajko.nokia.com









































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