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Internet Engineering Task Force                                Subir Das
Internet-Draft                                    Telcordia Technologies
Intended status: Proposed Standard                           Gabor Bajko
Expires: April 21, 2011                                            Nokia
                                                        October 19, 2010


Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for
Access Network Discovery and Selection Function(ANDSF) Discovery
                    draft-das-mipshop-andsf-dhcp-options-07

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ANDSF DHCP Options                                       October 2010

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 3GPP and provides
   inter-system mobility policies and access network specific
   information to the mobile nodes(MNs).



Table of Contents

   1. Introduction .................................................2
   2. ANDSF IPv4 address option for DHCPv4..........................3
   3. ANDSF IPv6 address option for DHCPv6..........................4
   4. Option Usage..................................................5
        4.1 Usage of ANDSF Options for DHCPv4.......................5
        4.2 Usage of ANDSF Options for DHCPv6.......................6
   5. Security Considerations ......................................6
   6. IANA Considerations ..........................................6
   7. Acknowledgements .............................................7
   8. References ...................................................7
       8.1 Normative References ....................................7
       8.2 Informative References ..................................7
   Author's Addresses ..............................................7



(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].


(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 [3GPP TS 23.402].

   Access Network: A network that is accessed by the user entity(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.


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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].

   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] 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.


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 (To Be Assigned)




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ANDSF DHCP Options                                       October 2010


   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.



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 (To Be Assigned)


   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





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 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 mobile 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
   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 is 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.



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   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 is 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.

   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]. 3GPP
   ANDSF framework also provides additional mechanisms that can also be
   used to mitigate above attacks and to protect message exchanges
   between 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) TBA

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


7. Acknowledgements

   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




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 8. References

    8.1 Normative References

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

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

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

   [RFC3315] Droms, R.,  et al,  "Dynamic Host Configuration Protocol
      for IPv6 (DHCPv6)", RFC 3315, July 2003

   [RFC3118] Droms, et al,  "Authentication for DHCP Messages", June
      2001


   8.2 Informative References


   [3GPPTS23.402] www.3gpp.org/ftp/Specs/html-info/23402.htm
                   3GPP TS 23.402 V8.8.0 (2009-12): Architecture
                    enhancements for non-3GPP accesses

   [3GPPTS24.302] www.3gpp.org/ftp/Specs/html-info/24302.htm
                    3GPP TS 24.302 V8.4.1 (2009-12): Access to the 3GPP
                    Evolved Packet Core (EPC) via non-3GPP access
                    Networks

   [3GPPTS33.402]:www.3gpp.org/ftp/Specs/html-info/33402.htm
                    3GPP TS 33.402 v8.6.0 (2009-120) System
                    Architecture Evolution: Security aspects of
                    non-3GPP accesses


Authors' Addresses

   Subir Das
   Telcordia Technologies Inc.
   e-mail: subir(at)research(dot)Telcordia(dot)com

   Gabor Bajko
   Nokia
   e-mail: gabor(dot)bajko(at)nokia(dot)com


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