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Versions: 00 01 02 03 04 05 06 07 RFC 6153

Internet Engineering Task force                              Subir Das
Internet Draft                                  Telcordia Technologies
Intended Status: Proposed Standard                         Gabor Bajko
Expires: September 03, 2009                                      Nokia
                                                        March 03, 2009


Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for
Access Network Discovery and Selection Function(ANDSF) Discovery
                   draft-das-mipshop-andsf-dhcp-options-00

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
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Copyright and License Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

   This document defines new Dynamic Host Configuration Protocol
   (DHCPv4 and DHCPv6) options that allow clients to discover the IP
   address or the domain name of Access Network Discovery and Selection

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ANDSF DHCP Options                                      March  2009

   Function (ANDSF) entities in an IP network. ANDSF is being
   developed in 3GPP (Release-8) and provides inter-system mobility
   policies and access network specific information to the mobile
   nodes [3GPPTS23.402].


 (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 RFC-2119.

 (2) Terminology and abbreviations used in this document

   ANDSF (Access Network Discovery and Selection Function): An entity
   that contains data management and control functionality and provides
   necessary 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 UE

   3GPP Network : Third Generation Partnership Project specified network

   Non-3GPP Network: Network that is not specified by 3GPP network (e.g., CDMA network)

Table of Contents

   1. Introduction .................................................2
   2. ANDSF IPv4 address option for DHCPv4..........................3
   3. ANDSF Domain Name List option for DHCPv4......................4
   4. ANDSF IPv6 address option for DHCPv6..........................5
   5. ANDSF Domain Name List option for DHCPv6......................6
   6. Option Usage..................................................7
        6.1 Usage of ANDSF Options for DHCPv4.......................8
        6.2 Usage of ANDSF Options for DHCPv6.......................8
   7. Security Considerations ......................................8
   8. IANA Considerations ..........................................8
   9. Acknowledgements .............................................9
   10. References ..................................................9
       10.1 Normative References ...................................9
   Author's Addresses .............................................10

1. Introduction

    Access Network Discovery and Selection Function (ANDSF) is being
    defined in 3GPP (Release-8) to provide necessary network discovery
    and selection assistance data to the mobile nodes for multi-access



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   network scenarios where 3GPP access-network level information is not
   sufficient for the mobile nodes to perform discovery and
   selection of non-3GPP networks[3GPPTS23.402].

   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) by the ANDSF
   over the S14 reference point as defined in [3GPPTS23.402].

   In 3GPP release-8, the ANDSF is located in the subscriber's home
   operator 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 Option and ANDSF Domain List Option, which allow the MN to
   locate an ANDSF Server that hosts the desired service as required
   by 3GPP.



2. ANDSF IPv4 Address Option for DHCPv4

   This section describes the ANDSF IPv4 Address Option for DHCPv4.
   The Option begins with an option code followed by a length and one
   or more IP addresses. The value of the length octet does not
   include itself or the option code. 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) - 1 byte

         Length

                An 8-bit field indicating the length of the option
                excluding the 'Option Code' and the 'Length' fields


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   IP Address

                IPv4 address(es) of ANDSF Server(s)

   When the total length of an ANDSF IPv4 Address Option exceeds 254
   octets, the procedure outlined in [RFC3396] MUST be employed to
   split the option into multiple, smaller options.

   If the length is followed by a list of IPv4 addresses indicating
   appropriate ANDSF servers available to the MN, servers MUST be
   listed in order of preference. Its minimum length is 4, and the
   length MUST be a multiple of 4. The Option has the following
   format:

           Code Len   IPv4 Address 1    IPv4 Address 2
         +-----+---+---+----+----+----+----+----+---
         |  XX | n |a1 | a2 | a3 | a4 | a1 |  ...
         +-----+---+---+----+----+----+-----+----+--


3. ANDSF Domain Name List Option for DHCPv4

   This section describes the ANDSF Domain Name List Option for DHCPv4.
   The general format of this option 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     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     FQDN(s)                                   |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


    Option Code

                OPTION-IPv4_FQDN-ANDSF (To Be Assigned) - 1 byte

     Length
                An 8-bit field indicating the length of the option
                excluding the 'Option Code' and the 'Length' fields

      FQDN

                Fully qualified domain name of ANDSF Server

   When the total length of an ANDSF Domain Name List Option exceeds
   254 octets, the procedure outlined in [RFC3396] MUST be employed
   to split the option into multiple, smaller options.


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  The encoding for this option has the following format:

           Code  Len   DNS name of ANDSF server
         +-----+----+----+-----+-----+-----+-----+--
         | XX  | n  | s1 |  s2 |  s3 |  s4 | s5  |  ...
         +-----+----+----+-----+-----+-----+-----+--


   The Option begins with a  code followed by a length and a sequence
   of labels that are encoded according to Section 8 of [RFC3315].

   [RFC1035] encoding was chosen to accommodate future international-
   lized domain name mechanisms. The minimum length for this encoding
   is 3.

   The option MAY contain multiple domain names, but these domain names
   SHOULD be used to construct Service Record (SRV) lookups as specified
   in [3GPPTS23.003], rather than querying for different A records.  The
   client can try any or ALL of the domain names to construct the SRV
   lookups. The list of domain names MAY contain the domain name of the
   ANDSF provider and its partner networks that also offer ANDSF
   Capabilities.

   As an example, consider the case where the server wants to offer
   two MIH IS servers, "example.com" and "example.net".  These would
   be encoded as follows:
   +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   | XX  |26 | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'c'|'o'|'m'| 0 |
   +-----+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   +---+---+---+---+---+---+---+---+---+---+---+---+---+
   | 7 |'e'|'x'|'a'|'m'|'p'|'l'|'e'| 3 |'n'|'e'|'t'| 0 |
   +---+---+---+---+---+---+---+---+---+---+---+---+---+


4. ANDSF IPv6 Address option for DHCPv6

   This section describes the ANDSF IPv6 Address Option for DHCPv6.
   The Option begins with an option code followed by a length
   and one or more IP addresses. The value of the length octet does
   not include itself or the option code. 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                                |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   ANDSF DHCP Options                                    March 2009

   Option Code

             OPTION-IPv6_Address-ANDSF (To Be Assigned) - 2 bytes

   Length

             A 16-bit field indicating the length of the option
             excluding the 'Option Code' and the 'Length' fields.

   IP Address

             IPv6 address(es) of ANDSF Server(s)

   The Option follows the same format (except the Option Code and
   Length value) as described in Section 2. The value of the Option
   Code and Length are 2-octets and the Length does not include itself
   or the Option Code field.



5. ANDSF Domain Name List option for DHCPv6

   This section describes the ANDSF Domain List Option for DHCPv6. The
   general format of this option 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              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     Domain Name List                          |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


       Option Code

             OPTION-IPv6_FQDN-ANDSF(To Be Assigned) - 2 bytes

       Length

             A 16-bit field indicating the length of the option
             excluding the 'Option Code' and the 'Length' fields.

       Domain Name List

             FQDN(s) of ANDSF Server





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   The Option follows the same format (except the Option Code and
   Length value) as described in Section 3. The value of the Option
   Code and Length are 2-octets and the Length does not include itself
   or the Option Code field.

   The semantics and content of the DHCPv6 encoding of this option are
   exactly the same as the encoding described in Section 3, except the
   Option Code and Length value.



6. Option Usage

6.1 Usage of ANDSF Options for DHCPv4

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

6.1.1 Mobile Node behavior

   The mobile node may perform an ANDSF discovery procedure either during
   initial association with a network or when the policy and access
   network information is required from ANDSF to perform discovery and
   selection of non-3GPP networks. It may also try to perform the ANDSF
   discovery when the network information is outdated or mobile does not
   have any ANDSF information.

   In order to request an address or domain name of a ANDSF Server, the
   mobile node(DHCP client) MUST include either an ANDSF IP Address
   Option or an ANDSF Domain Name List Option into either a DHCPDISCOVER
   or DHCPINFORM message.

6.1.2 DHCP Server behavior

   When the DHCP server receives either a DHCPDISCOVER or DHCPINFORM
   message containing either an ANDSF Option or an ANDSF Domain Name
   List Option, the DHCP server MUST always construct the response that
   may contain a list of one or more IP addresses or a list of one or
   more FQDNs of the ANDSF server hosting the service.

   In case that the server cannot find any ANDSF Server satisfying
   the requested Option Code, the server MUST return the ANDSF Option
   by setting the Option Code to the requested Option Code and the
   length of the Option to 1.


6.2 Usage of ANDSF Options for DHCPv6

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

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6.2.1 Mobile node behavior

   The mobile node may perform the ANDSF discovery procedure
   either during initial association with a network or when the policy
   and access network information is required from ANDSF to perform
   discovery and selection of non-3GPP networks. It may also
   try to perform the ANDSF discovery when the network information is
   outdated or mobile does not have any ANDSF information.

   In order to discover the address or domain name of an ANDSF Server,
   the mobile node(DHCP client) MUST include either an ANDSF IP Address
   Option or Domain Name List Option into either a REQUEST or an
   INFORMATION-REQUEST message.

6.2.2 DHCP Server behavior

   When the DHCP Server receives either a REQUEST or an INFORMATION-
   REQUEST message with either an ANDSF IP Address Option or Domain
   Name List Option, the DHCP server MUST always construct the response
   that may contain a list of one or more IP addresses or a list of one
   or more FQDNs of the ANDSF server hosting the service.

   In case that the server cannot find any ANDSF Server satisfying
   the requested Option Code, the server MUST return the ANDSF Option
   by setting the Option Code to the requested Option Code and the
   length of the Option to 1.


 7. Security Considerations

   The security considerations in [RFC2131] apply. 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.

   It is recommended to use either DHCP authentication option described
   in [RFC3118] where available, or rely upon 3GPP specific security.
   This will also protect the denial of service attacks to DHCP
   servers. [RFC3118] provides mechanisms for both entity
   authentication and message authentication.


8. IANA Considerations

   This document defines two new DHCPv4 options as described in Sections
   2 and 3.

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

   ANDSF Domain Name List option for DHCPv4(OPTION-IPv4_FQDN-ANDSF) TBA


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  This document also defines two DHCPv6 options as described in
  Sections 4 and 5.

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

   ANDSF Domain Name List option for DHCPv6 (OPTION-IPv6_FQDN-ANDSF) TBA



9. Acknowledgements




10. References

    10.1 Normative References

   [3GPP TS23.402] www.3gpp.org/ftp/Specs/html-info/23402.htm
                   3GPP TS 23.402 V8.4.1 (2009-01): Architecture
                    enhancements for non-3GPP accesses (Release 8)

   [3GPP Ts 24.302] www.3gpp.org/ftp/Specs/html-info/24302.htm
                    3GPP TS 24.302 V8.0.0 (2008-12): Access to the 3GPP
                    Evolved Packet Core (EPC) via non-3GPP access
                    networks; Stage 3;(Release 8

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

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

   [3GPP TS23.003] www.3gpp.org/ftp/Specs/html-info/23003.htm
                   3GPP TS 23.003 V8.3.0 (2008-12): Numbering,
                   addressing and identification(Release 8)

   [RFC3315] Dynamic Host Configuration Protocol for IPv6 (DHCPv6),
      Droms et al, July 2003

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

   [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long DHCP Options",
      RFC3396, November 2002.

   [RFC5226] T. Narten and H. Alvestrand, "Guidelines for Writing an
    IANA  Considerations Section in RFCs" , May 2008.



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Authors' Addresses

   Subir Das
   Telcordia Technologies Inc.
   e-mail: subir@research.telcordia.com


   Gabor Bajko
   Nokia
   e-mail: gabor.bajko@nokia.com






































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