Internet Engineering Task Force Subir Das Internet-Draft Telcordia Technologies Intended status: Proposed Standard Gabor Bajko Expires: February 02, 2011 Nokia July 02, 2010 Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Options for Access Network Discovery and Selection Function(ANDSF) Discovery draft-das-mipshop-andsf-dhcp-options-04 Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". 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Bajko Expires 02/02/11 [Page 1] ANDSF DHCP Options July 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 ..............................................8 (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 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. S. Das & G. Bajko Expires 02/02/10 [Page 2] ANDSF DHCP Options July 2010 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 Option and ANDSF Domain List Option, 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 begins with an option code followed by a length and one or more IP addresses. 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 S. Das & G. Bajko Expires 02/02/11 [Page 3] ANDSF DHCP Options July 2010 Length An 8-bit field indicating the length of the option excluding the 'Option Code' and the 'Length' fields IP Address IPv4 address(es) of ANDSF Server(s) 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 and the client should process them in decreasing order of preference. The Option has the following format: Code Len IPv4 Address 1 IPv4 Address 2 +-----+----+----+----+----+----+----+----+---- | XX | n |a1 | a2 | a3 | a4 | a1 | ... +-----+----+----+----+----+----+----+----+---- 3. 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 | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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. S. Das & G. Bajko Expires 02/02/11 [Page 4] ANDSF DHCP Options July 2010 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. If the length is followed by a list of IPv6 addresses indicating appropriate ANDSF servers available to the MN, 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 performs ANDSF discovery procedure either during initial association with a network or when the policy and access network information is required from ANDSF. 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 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]. If the mobile node receives no address, it may either try another server or may continue to retransmit the PRL message. However, it MUST limit the rate at which it retransmits the message and limit the duration of the time during which it retransmits the message. 4.1.2 DHCP Server behavior When the DHCP server receives an ANDSF IPv4 Address Option in the PRL, the DHCP server MUST include the option in its response messages (as defined in [RFC2131]and [RFC2132])that may contain a S. Das & G. Bajko Expires 02/02/11 [Page 5] ANDSF DHCP Options February 2010 list of one or more IP addresses of the ANDSF server hosting the service. 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 performs ANDSF discovery according to the procedures 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]. If the mobile node receives no address, it may either try another server or may continue to retransmit the ORO message. However, it MUST limit the rate at which it retransmits the message and limit the duration of the time during which it retransmits the message. 4.2.2 DHCP Server behavior When the DHCP Server receives an ANDSF IPv6 Address Option in the ORO, the DHCP server MUST include the option in its response (as defined in [RFC3315])that may contain a list of one or more IP addresses of the ANDSF server hosting the service. 5. 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 DHCP authentication option described in [RFC3118] where available. This will also protect the denial of service attacks to DHCP servers. [RFC3118] provides mechanisms for both entity authentication and message authentication. In deployments where DHCP authentication is not available, 3GPP specific lower layer security services may be sufficient to protect DHCP messages. 3GPP ANDSF framework also provides additional S. Das & G. Bajko Expires 02/02/11 [Page 6] ANDSF DHCP Options July 2010 mechanisms that protect message exchanges between ANDSF client and server at the higher layer. 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, and Jari Arkko, 8. References 8.1 Normative References [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] Authentication for DHCP Messages, Droms et al, June 2001 8.2 Informative References [3GPP TS23.402] www.3gpp.org/ftp/Specs/html-info/23402.htm 3GPP TS 23.402 V8.8.0 (2009-12): Architecture enhancements for non-3GPP accesses (Release 8) S. Das & G. Bajko Expires 02/02/11 [Page 7] ANDSF DHCP Options July 2010 [3GPP Ts 24.302] 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; Stage 3;(Release 8) 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 S. Das & G. Bajko Expires 02/02/10 [Page 8]