Network Working Group S. Bhandari Internet-Draft S. Kumar Intended status: Standards Track Cisco Systems Expires: January 9, 2013 July 8, 2012 DHCPv4 Configuration Options in PMIPv6 draft-bhandari-netext-pmipv6-dhcp-options-00 Abstract This document specifies methods to learn DHCP host configuration options by DHCPv4 server co-located at Mobile Access Gateway(MAG) as directed by Local Mobility Anchor(LMA) via Proxy Mobile IPv6(PMIPv6) signalling. Requirements Language 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 [RFC2119]. 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). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 9, 2013. Copyright Notice Copyright (c) 2012 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 Bhandari & Kumar Expires January 9, 2013 [Page 1] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Mechanisms to learn DHCPv4 options by DHCPv4 Server co-located at MAG . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. LMA signalling MAG to send DHCPINFOR . . . . . . . . . . . 4 4.2. MAG voluntarily sending DHCPINFORM . . . . . . . . . . . . 6 4.3. Mobile Header Option to encapsulate DHCPv4 Option . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 8. Normative References . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Bhandari & Kumar Expires January 9, 2013 [Page 2] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 1. Introduction Proxy Mobile IPv6 protocol is extended to support IPv4 to enable IPv4 home address mobility support to the mobile node as detailed in [RFC5844]. Dynamic Host Configuration Protocol v4 (DHCPv4) based address configuration support for a mobile node in a Proxy Mobile IPv6 domain is detailed in Section 3.4 of [RFC5844] where the Mobile Access Gateway(MAG) can support co-location of DHCPv4 Server or DHCPv4 Relay agent as directed by Local Mobility Anchor(LMA) in IPv4 DHCP Support Mode Option. When DHCPv4 Relay agent is co-located with MAG, DHCPv4 Server in the proxy mobile IPv6 domain can be configured to influence and respond to the mobile node with all the DHCPv4 configuration options. However when DHCPv4 Server is co-located with MAG in a Proxy Mobile IPv6 domain it has to be statically configured with all the DHCPv4 option values (e.g., DNS Server, SIP Server, etc. that have no corresponding Mobility Header options defined) that correspond to IPv4 Home Address assignment for all its DHCPv4 clients. Due to static configuration required at the MAG this works well when the number of MAGs are few and when the same configuration options are to be applied to all the mobile nodes attached to the MAG. Currently there is no well defined scheme to influence DHCPv4 Server co-located at MAG with the DHCPv4 options values to be offered to the DHCPv4 clients (Mobile Nodes) dynamically via PMIPv6 signalling. This document specifies mechanism for DHCPv4 server co-located at the MAG to learn DHCPv4 options that can be offered to the mobile nodes that it serves via PMIPv6 signalling. 2. Motivation Proxy mobile IPv6 [RFC5213] can be used for supporting network-based mobility management in various types of network deployments. IPv4 address assigment extension to PMIPv6 is added by [RFC5844] that adds new Mobility Header options to influence IPv4 address assignment. Specifically [RFC5844] adds support to influence: 1. IPv4 address configuration offered to the client - Mobility Header Option Type 37 that can be used to fill 'yiaddr' field of DHCPv4 message as specifed in [RFC2131] and Subnet Mask Option as specified in [RFC2132] 2. IPv4 Default-Router Address Option - Mobility Header Option Type 38 that can be used to fill DHCPv4 Router Option as specifed in [RFC2132] Bhandari & Kumar Expires January 9, 2013 [Page 3] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 In addition to the above an IPv4 device requires more configuration to communicate with other nodes in the network. For example if LMA is influencing the IPv4 address configuration it may also have to influence configuration corresponding to the address such as DNS server's IP address, Domain name for the mobile node etc. It demands operational overhead to statically configure DHCPv4 server co-located at each MAG with all this configuration options. 3. Terminology All the DHCP related terms used in this document to be interpreted as defined in the Dynamic Host Configuration Protocol v4 (DHCPv4) [RFC2131] specification. All the mobility related terms used in this document are to be interpreted as defined in the Proxy Mobile IPv6 specifications [RFC5213] and [RFC5844]. 4. Mechanisms to learn DHCPv4 options by DHCPv4 Server co-located at MAG DHCPv4 options can be learnt by a DHCPv4 Server co-located at the MAG using any of the following mechanisms: 1. LMA signaling MAG in Protocol Binding Acknowlegment(PBA) to trigger DHCPINFORM request message to obtain configuration options as specified in [RFC2131]. 2. MAG to voluntarily send DHCPINFORM message when it discovers the LMA, to dynamically learn DHCPv4 configuration options. These options will be applied to all or group of mobile nodes that will attach to the MAG and are anchored at the specific LMA, when the mobile nodes trigger DHCPv4 discover. 3. New Mobility Header option, to encapsulate DHCPv4 option within it, that is included in PBA message from LMA to MAG - DHCPv4 server co-located at MAG can process this DHCPv4 option after decapsulation and include the learnt DHCPv4 options in the DHCPv4 response messages towards the client. The following sections will describe each of the above approaches. 4.1. LMA signalling MAG to send DHCPINFOR In this approach LMA can influence the DHCPv4 Server co-located at the MAG to trigger DHCPINFORM on a per MN basis to influence DHCPv4 Bhandari & Kumar Expires January 9, 2013 [Page 4] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 options sent to the MN. Figure 1 provides high level message exchange between MN, DHCP server at MAG, MAG and LMA. MN MAG(DHCP-S) LMA |------>| | 1. DHCPDISCOVER | |------->| 2. Proxy Binding Update | |<-------| 3. Proxy Binding Acknowledgement | | | (IPv4 HoA, Support Mode set | | | to indicate server mode and | | | availability of additional | | | DHCPv4 options) | |========| 4. Tunnel/Route Setup | |------->| 5. DHCPINFORM | |<-------| 6. DHCPACK (All the options | | | applicable to the MN) |<------| | 7. DHCPOFFER (IPv4 HoA, Options) |------>| | 8. DHCPREQUEST (IPv4 HoA, Options) |<------| | 9. DHCPACK | | | Figure 1: Overview of per MN DHCPINFORM exchange between DHCP Server co-located at MAG and LMA To acheive this IPv4 DHCP Support Mode Option defined in Section 3.3.4 of [RFC5844] will be extended to carry additional flag that can be interpreted by MAG to trigger DHCPINFORM. Bhandari & Kumar Expires January 9, 2013 [Page 5] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type(39) | Length(2) | Reserved (R) |M|S| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type, Length and DHCP Support Mode (S) are as defined in Section 3.3.4 of RFC5844. Addition 1-bit from the Reserved flags is used to define the following flag: DHCP More configs available (M) A 1-bit field that when set indicates more DHCP options are available. This flag when set to (1) indicates to MAG that DHCPINFORM message has to be triggered to learn more DHCPv4 options. This flag MUST be set to (0) when the DHCP Support Mode indicates DHCP Relay. IPv4 DHCP Support Mode Option The DHCPINFORM message triggered by MAG MUST have'ciaddr' field set to IPv4 home address of the MN learnt in PBA and 'giaddr' field set to MAGs IPv4 address reachable to LMA. The response DHCPACK is received by MAG to learn and cache the DHCP options that will then be sent to the MN in DHCP reply messages. This approach provides per MN configuration granularity to LMA. This results in overhead of DHCPINFORM-DHCPACK message exchange for every MN that need to be influenced with DHCP options available. 4.2. MAG voluntarily sending DHCPINFORM When MAG discovers LMA in a Proxy Mobile IPv6 domain, it can voluntarily trigger one ore more DHCPINFORM message with 'ciaddr' field set to IPv4 address of each of its interface in that Proxy Mobile IPv6 domain. LMA MAY respond with DHCPACK message with the options applicable to all the MNs that will attach to the MAG indicated by 'ciaddr'. LMA will respond with DHCPACK only if it is configured to support MAG to act as DHCP server and has additional options available. Otherwise LMA will silently discard the received DHCPINFORM. MAG will cache the DHCP options received in response to the DHCPINFORM. DHCPv4 server co-located at MAG will send these cached Bhandari & Kumar Expires January 9, 2013 [Page 6] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 options towards the MN when it receives DHCP request messages. Figure 2 provides message exchange overview for this approach. MN MAG(DHCP-S) LMA | |------->| 1. DHCPINFORM | |<-------| 2. DHCPACK | | | (Learn and cache options . . . for future use) . . . |------>| | 3. DHCPDISCOVER | |------->| 4. Proxy Binding Update | |<-------| 5. Proxy Binding Acknowledgement | | | (IPv4 HoA, Support Mode set | | | to indicate server mode) | |========| 4. Tunnel/Route Setup |<------| | 7. DHCPOFFER (IPv4 HoA, | | | other options learnt in Step 2) |------>| | 8. DHCPREQUEST (IPv4 HoA) |<------| | 9. DHCPACK | | | Figure 2: Overview of DHCPINFORM exchange between MAG and LMA Periodicity of MAG sending such DHCPINFORM messages to refresh the cached data will be driven by configuration at MAG. This approach is optimal when LMA wants to provide the same DHCP host configuration options for a large set of MNs attaching to MAG. 4.3. Mobile Header Option to encapsulate DHCPv4 Option A new option, the DHCP Encapsulation option, is defined for use in the Proxy Binding Acknowledgement message sent by the local mobility anchor(LMA) to the mobile access gateway (MAG). This option will encapsulate the complete DHCPv4 option including code, length and value. This option MAY be included only when IPv4 DHCP Support Mode option indicates DHCPv4 Server support at MAG. It MUST NOT be included when MAG acts as a DHCPv4 Relay. Zero or more instances of this option can be included in PBA message to send different DHCP Options. DHCPv4 server co-located at MAG can decapsulate the DHCP Option within this option and send it in DHCP response messages to MNs, adhering to DHCP protocol specification. Bhandari & Kumar Expires January 9, 2013 [Page 7] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + DHCP Option + . ... . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type Length 8-bit unsigned integer indicating the length of the option in octets, excluding the type and length fields. Reserved This field is unused for now. The value MUST be initialized to 0 by the sender and MUST be ignored by the receiver. DHCP Option A variable length field containing the DHCP option including code, length and value. DHCP Encapsulation Option This approach is useful when the number of DHCP options that are to be influenced by LMA is small in comparison to the overhead of exchanging DHCPINFORM message described in Section 4.1 to retrive these options. For e.g. if only DNS Server address option has to be influenced then it can be encapsulated in this option instead of forcing a DHCPINFORM to retrieve it or defining a new Mobility Header Option equivalent to each of the DHCP Option to be influenced. 5. IANA Considerations This document defines a new Mobility Header options, the DHCP Encapsulation Option described in Section 4.3. The Type value for this option should be assigned from the same numbering space as allocated for the other mobility options, as defined in [RFC3775]. Bhandari & Kumar Expires January 9, 2013 [Page 8] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 6. Security Considerations All the security considerations from [RFC5844] apply to this specification. In addition security consideration for exchanging DHCP messages between MAG and LMA (DHCPINFORM) message as outlined in [RFC2131] also apply. Link-layer confidentiality and integrity protection may be employed to reduce the risk of disclosure and tampering of DHCP messages between LMA, MAG and MN. This document defines new mobility option for supporting dhcp configuration options encapsulation. These options are to be carried in Proxy Binding Acknowledgement messages. The required security mechanisms specified in the base Proxy Mobile IPv6 protocol for protecting these signaling messages are sufficient when carrying these mobility options. 7. Acknowledgements 8. 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. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy Mobile IPv6", RFC 5844, May 2010. Bhandari & Kumar Expires January 9, 2013 [Page 9] Internet-Draft DHCPv4 host configuration via PMIPv6 July 2012 Authors' Addresses Shwetha Bhandari Cisco Systems Cessna Business Park, Sarjapura Marathalli Outer Ring Road Bangalore, KARNATAKA 560 087 India Phone: +91 80 4426 0474 Email: shwethab@cisco.com Sanjay Kumar Cisco Systems Cessna Business Park, Sarjapura Marathalli Outer Ring Road Bangalore, KARNATAKA 560 087 India Phone: +91 80 4426 0274 Email: sakumar3@cisco.com Bhandari & Kumar Expires January 9, 2013 [Page 10]