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Internet Engineering Task Force (IETF)                            S. DasRequest for Comments: 6153                        Telcordia TechnologiesCategory: Standards Track                                       G. BajkoISSN: 2070-1721                                                    Nokia                                                           February 2011DHCPv4 and DHCPv6 Options forAccess Network Discovery and Selection Function (ANDSF) DiscoveryAbstract   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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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.Das & Bajko                  Standards Track                    [Page 1]

RFC 6153                   ANDSF DHCP Options              February 2011Table of Contents1. Introduction ....................................................21.1. Conventions Used in This Document ..........................31.2. Terminology and Abbreviations Used in This Document ........32. ANDSF IPv4 Address Option for DHCPv4 ............................33. ANDSF IPv6 Address Option for DHCPv6 ............................44. Option Usage ....................................................44.1. Usage of ANDSF Options for DHCPv4 ..........................44.1.1. Mobile Node Behavior ................................44.2. Usage of ANDSF Options for DHCPv6 ..........................54.2.1. Mobile Node Behavior ................................55. Security Considerations .........................................56. IANA Considerations .............................................57. Acknowledgments .................................................68. References ......................................................68.1. Normative References .......................................68.2. Informative References .....................................61.  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.Das & Bajko                  Standards Track                    [Page 2]

RFC 6153                   ANDSF DHCP Options              February 20111.1.  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 organizations2.  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.Das & Bajko                  Standards Track                    [Page 3]

RFC 6153                   ANDSF DHCP Options              February 20113.  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 Usage4.1.  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 asDas & Bajko                  Standards Track                    [Page 4]

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 inSection 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], Sections17.1 and18.1.5.  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 Sections2   and 3:   ANDSF IPv4 Address Option for DHCPv4 (OPTION-IPv4_Address-ANDSF) 142   ANDSF IPv6 Address Option for DHCPv6 (OPTION-IPv6_Address-ANDSF) 143Das & Bajko                  Standards Track                    [Page 5]

RFC 6153                   ANDSF DHCP Options              February 20117.  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.  References8.1.  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",RFC2131, 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.Das & Bajko                  Standards Track                    [Page 6]

RFC 6153                   ANDSF DHCP Options              February 2011Authors' Addresses   Subir Das   Telcordia Technologies Inc.   EMail: subir@research.telcordia.com   Gabor Bajko   Nokia   EMail: gabor@bajko.nokia.comDas & Bajko                  Standards Track                    [Page 7]