IETF Mobile IP Working Group JH. Kim Internet-Draft SAMSUNG AIT Expires: April 15, 2004 P. Rajendran SAMSUNG ISO Y. Han J. Kim SAMSUNG AIT October 16, 2003 Using Neighbor Caceh Entry for Duplicate Address Detection draft-hoon-mobileip-undad-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 15, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract The Duplicate Address Detection (DAD) procedure detailed by Neighbor Discovery Protocol (NDP) requires nodes to wait for a quantified time interval during which the configured address is checked for duplication in the connected link. This delay affects normal communication in a Mobile Node (MN) during the DAD time interval thereby hampering Fast Handoff. The expected use of Mobile IP on a wide scale and the need for a minimal time delay during the handoff process require alternate mechanisms for overcoming the DAD time Kim, et al. Expires April 15, 2004 [Page 1] Internet-Draft Using NCE for DAD October 2003 interval. This draft presents a mechanism wherein the Access Router's (AR) Neighbor Cache Entry (NCE) is used to minimize the delay associated with the DAD procedure. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Requirements for using Neighbor Cache Entry in mobile ipv6 . . 5 3.1 Mobile Node's requirement . . . . . . . . . . . . . . . . . . 5 3.2 AR's requirement . . . . . . . . . . . . . . . . . . . . . . . 5 4. Protocol operation . . . . . . . . . . . . . . . . . . . . . . 6 4.1 Mobile node's operation . . . . . . . . . . . . . . . . . . . 6 4.2 Access Router's operation . . . . . . . . . . . . . . . . . . 6 5. Modified ICMPv6 message . . . . . . . . . . . . . . . . . . . 8 5.1 Modified NS message . . . . . . . . . . . . . . . . . . . . . 8 5.2 Modified NA message . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 Normative References . . . . . . . . . . . . . . . . . . . . . 11 Informative References . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . 14 Kim, et al. Expires April 15, 2004 [Page 2] Internet-Draft Using NCE for DAD October 2003 1. Introduction Mobile Nodes receive Router Advertisements (RAs) from the access routers when they roam into a foreign network. These RAs carry the prefix information of the subnet which the MN uses to configure its Care of Address (COA)[2]. The MN is then expected to perform normal DAD on the connected link to ascertain the uniqueness of the COA. This DAD time interval is expected to last a minimum of 1000ms during which time all existing communication with the MN are paused. Only after completion of the DAD time interval does the MN begin the Home registration process[3]. The DAD time interval can significantly influence the time a Mobile Node takes for Handoff thereby requiring alternate mechanisms to minimize it. In this document, we propose a scheme of using the Neighbor Cache Entries (NCE) of the access router for an efficient DAD process. Access Routers are required to perform additional functionalities in order to maintain the complete list of nodes present in the subnet in their Neighbor Cache. Mobile Nodes on detecting movement into a new subnet query the Access Router about the uniqueness of the care of address. The Access Routers check the Neighbor Cache for any matching information and respond to the mobile nodes query. This method of using the Neighbor Cache of the access router can support fast hand-off by reducing DAD delay time. Kim, et al. Expires April 15, 2004 [Page 3] Internet-Draft Using NCE for DAD October 2003 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and "silently ignore" in this document are to be interpreted as described in RFC 2119 [1]. The following terminology and abbreviations are used in this document. Access Router (AR) - Mobile node's default router which forwards IP packets not explicitly addressed to itself. Neighbor Cache Entry (NCE) - A set entries about individual neighbors to which traffic has been sent recently. Duplicate address detection (DAD) - Before the link-local address be assigned to an interface and used, however, a node must attempt to verify that this "tentative" address is not already used by some node on the connected link. Kim, et al. Expires April 15, 2004 [Page 4] Internet-Draft Using NCE for DAD October 2003 3. Requirements for using Neighbor Cache Entry in mobile ipv6 Following subsections list the minimum set of requirements for efficient DAD protocol. 3.1 Mobile Node's requirement - A mobile node should request the access router to verify the uniqueness of its IP address by sending a DAD NS. - A mobile node should assign the Care of Address to its interface, as soon as it receives NA from access router after sending NS for DAD. 3.2 AR's requirement - Access routers should accept and process all NS with unspecified source address and solicited-node-multicast destination address for DAD. - Access router should compare the target address in the received DAD NS message with the Neighbor cache entries to detect duplication. - Access routers on determining that the target address is not present in the NC should create a new NC entry for the target address. - Access router should reply to the sender which has sent NS message with the 'A' bit set in the 4th reserved field in NA if access router has no entry corresponding to the target address. Kim, et al. Expires April 15, 2004 [Page 5] Internet-Draft Using NCE for DAD October 2003 4. Protocol operation This section describes our protocol operation in detail. 4.1 Mobile node's operation A mobile node creates a new CoA with the prefix advertised by the access router when it moves to foreign network. The mobile node then MUST send the modified DAD NS message to the solicited node multicast address for DAD procedure before assigning the address to the interface. The modified NS message is sent with the reserved field bit set and the mobile node waits for a NA message either from the access router or from some other node in the same network configured with the same address. 1) NA message from access router. - The target address in this NA message form access router is the target address sent by the Mobile node in its NS message. The 'A' bit is set in the message to indicate the address's uniqueness. The 'A' bit is used to indicate that the Access Router has no NCE corresponding to the target address sent by the mobile node. On receipt of the modified NA message the mobile node can send an unsolicited NA message to the Access router to provide the MAC address. 2) NA message from existing node. - The mobile node can also receive a NA message from another node in the network with the same address prior to receiving the NA message from the router. In this case the mobile node should use some other mechanism to configure its address. If the mobile node does not receive NA messages from either the Access Router or some other existing node then it has to wait for atleast 1000ms before it can configure the address to its interface. 4.2 Access Router's operation The Access router is required to provide additional functionality in terms of maintaining the addresses of all the connected nodes in the link. The access router achieves this by listening to all DAD packets in the network. The above NS message is sent with solicited-node-multicast destination address(FF02:0:0:0:0:1:FFXX:XXXX) and Ethernet multicast destination address whose first two octets are the value 3333 hexadecimal and whose last four octets are the last four octets of destination address. A access router can receive all DAD packet by Kim, et al. Expires April 15, 2004 [Page 6] Internet-Draft Using NCE for DAD October 2003 monitoring the fixed octets (FF02:0:0:0:0:1:FF, 3333 hexadecimal) of solicited-node-multicast destination address and Ethernet multicast destination address. Once the access router receives a DAD NS message with the A bit set it looks up its NC to determine if an entry is already present. If an entry is not present then it sends out a NA message with the A bit set. It also creates a new entry in its NC with the target address of the NS message. Kim, et al. Expires April 15, 2004 [Page 7] Internet-Draft Using NCE for DAD October 2003 5. Modified ICMPv6 message 5.1 Modified NS message This NS sent from MN to verify uniquness of new CoA and request to check the NCE of access router if it has same address list as new CoA. 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 | code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Taget address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IP Field: Source Address Unspecified address. Destination Address Solicted-node-multicast address. ICMP Field: Type 135. Code, Checksum See [RFC2461]. 'R' flag Use the highest bit in a reserved field to indicate that the mobile node is requesting the access router to compare the target address with the list of entries in the NC. Kim, et al. Expires April 15, 2004 [Page 8] Internet-Draft Using NCE for DAD October 2003 5.2 Modified NA message This NA message is sent from AR if it has no entry corresponding to New CoA. 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 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R|S|O|A| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Target Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ IP Field: Source Address Access router's IP address. Destination Address Solicted-node-multicast address. Type 136. Code, Checksum See [RFC 2461]. R, S, O See [RFC 2461]. 'A' flag A bit is set when access router has no NCE about target address of Modified NS. Kim, et al. Expires April 15, 2004 [Page 9] Internet-Draft Using NCE for DAD October 2003 6. Security Considerations This draft introduces no security risks in addition to those that are already present in the underlying protocols. However, due consideration has to be given to the fact that a malicious node also can receive all NS messages for DAD. It can then send out NA messages causing the DAD of the mobile node to fail. If a malicious node sends NS messages with different target address continuously, the access router will create NCEs which will hamper a mobile nodes hand off. The access routers can be provided with a NCE maintenance process to detect such problems if it exists in the sub-network. Kim, et al. Expires April 15, 2004 [Page 10] Internet-Draft Using NCE for DAD October 2003 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-24 (work in progress), July 2003. [3] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. Kim, et al. Expires April 15, 2004 [Page 11] Internet-Draft Using NCE for DAD October 2003 Informative References [4] Moore, N., "Optimistic Duplicate Address Detection", draft-moore-ipv6-optimistic-dad-03 (work in progress), September 2003. [5] Han, Y., "Advance Duplicate Address Detection", draft-han-mobileip-adad-01 (work in progress), July 2003. Authors' Addresses Jae-Hoon Kim SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9532 EMail: yh21.han@samsung.com Praveen Rajendran SAMSUNG India Software Operation Network Systems Division INDIA EMail: praveen@samsung.com Youn-Hee Han SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9233 EMail: yh21.han@samsung.com Kim, et al. Expires April 15, 2004 [Page 12] Internet-Draft Using NCE for DAD October 2003 Jung-Ho Kim SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9533 EMail: kjhhjk@samsung.com Kim, et al. Expires April 15, 2004 [Page 13] Internet-Draft Using NCE for DAD October 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. 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Expires April 15, 2004 [Page 14] Internet-Draft Using NCE for DAD October 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Kim, et al. Expires April 15, 2004 [Page 15]