Mobile-IP Working Group Yong-Geun Hong Internet Draft Myung-Ki Shin Draft-hong-mobileip-acar-01.txt Jung-Soo Park Expires: April 2004 Hyoung-Jun Kim ETRI October 2003 Access Router Based Movement Detection and CoA Configuration draft-hong-mobileip-acar-01.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. Abstract This document proposes Access Router (AR) based movement detection and Care-of Address (CoA) configuration for fast handover in Mobile IPv6 using layer 2 hints (for example, Link Up in 802.11). After receiving these layer 2 hints, an Active Access Router (AcAR) which will serve a Mobile Node (MN) performs movement detection, formulates a new CoA of the MN and does Duplicate Address Detection (DAD) on behalf of the MN. After confirming the uniqueness of the new CoA, the AcAR sends it through a RA message. Since an AcAR can quickly determine the L3 movement by the comparison between neighbor caches and L2 information of a MN, the movement detection delay is reduced. Since DAD is performed by an AcAR in advance, a MN does not have to do normal DAD and it can use a new CoA for its interface directly. And it may reduce another handover delay which is added because of the characteristics of an application layer. Hong, Shin, Park, Kim Expires: April 2004 [Page 1] AR-Based MD and CoA Configuration June 2003 Table of Contents 1. Introduction...................................................2 2. Terminology....................................................3 3. Protocol Overview..............................................3 3.1 Movement Detection.........................................3 3.2 CoA configuration and Duplicate Address Detection..........4 3.3 Delivering new CoA to MN...................................4 4. Modification to IPv6 Neighbor Discovery........................5 4.1 Modified Router Solicitation Message Format................5 4.2 Modified Router Advertisement Message Format...............5 4.3 Modified Prefix Information Option Format..................6 Security Considerations...........................................7 References........................................................7 Acknowledgments...................................................8 Author's Addresses................................................8 1. Introduction In Mobility Support in IPv6 (MIPv6) [1], a MN can determine its network layer movement by using Router Discovery and Neighbor Unreachability Detection. After a MN makes a new CoA, it must check its uniqueness by DAD. The delay of movement detection, new CoA configuration and DAD are inevitable in MIPv6 because of its basic operations. But the combined delay could be appreciable for real-time applications and throughput-sensitive applications [2]. Until now, there are many efforts to reduce the handover latency, especially in movement detection phase and in new CoA configuration phase. For fast movement detection, there are many drafts such as IPv6 Fast Router Advertisement [3], Fast Router Discovery with RA Caching in AP [4], and Router Advertisement Link Identification for Mobile IPv6 Movement Detection [5]. Also, there are many drafts such as Enhanced Forwarding from Previous Care-of Address for Fast Mobile IPv6 Handover (eFWD) [6], Optimistic Duplicate Address Detection [7], and Advance Duplicate Address Detection [8] for fast new CoA configuration and DAD. This document proposes Access Router (AR) based movement detection and CoA configuration for fast handover in Mobile IPv6 using layer 2 hints (for example, Link Up in 802.11). After receiving these layer 2 hints, an Active Access Router (AcAR) which will serve a MN performs movement detection, formulates a new CoA of the MN and does DAD on behalf of the MN immediately after L2 handoff. Since an AcAR can quickly determine the L3 movement by the comparison between neighbor caches and L2 information of a MN, the movement detection delay is reduced. After confirming the uniqueness of the new CoA, the AcAR sends it through a RA message. Since DAD is performed by an AcAR in advance, a MN does not have to do normal DAD and it can use the new Hong, Shin, Park, Kim Expires: April 2004 [Page 2] AR-Based MD and CoA Configuration June 2003 CoA for its interface. And it may reduce another handover delay which is added because of the characteristics of an application layer. 2. Terminology CoA Care-of Address DAD Duplicate Address Detection MN Mobile Node AcAR Active Access Router It performs movement detection, CoA configuration and DAD on behalf of a MN. 3. Protocol Overview The goal of this draft is that it explicitly uses layer 2 hints for fast handover. Although the increased rate of unsolicited Router Advertisement (RA) messages may provide timely movement detection, this scheme of modified interval time is not an ultimate solution : it increases considerable overhead and makes it difficult to connect another common networks. Another goal of this draft is that it considers movement detection as well as new CoA configuration, and DAD simultaneously at AR. Until now, most only focus on one of them. And only a MN does any necessary operations to detect L3 movement such as soliciting a Router Solicitation (RS), checking the reachability of an old AR, checking the validation of an old CoA and waiting RA messages from any ARs. If a MN and an AR have the same information to detect L3 movement, the AR may take the role of movement detection. It is same to CoA configuration and DAD. If an AR generates a new CoA for a MN, it can do DAD instead of a MN. 3.1 Movement Detection When mobile IPv6 networks have a possibility to connect another public networks and the frequency of unsolicited RAs have problems for traffic loads, the proposed mechanism provides a reasonable solution for receiving Router Advertisement more quickly. After the completion of L2 handoff, a MN and an AR may know it by some general L2 event. Especially in 802.11 networks, the LU trigger may be used after reassociation.request and reassociation.reply messages sharing. In our proposed scheme, L3 movement detection is processed by an AR. We call this AR as an Active Access Router (AcAR). The initiation of movement detection is enabled by L2 triggers at a MN immediately after the completion of L2 handoff and delivered to the network layer Hong, Shin, Park, Kim Expires: April 2004 [Page 3] AR-Based MD and CoA Configuration June 2003 of a MN. When L2 triggers are delivered to a network layer, the MN sends a unicast RS message before any general operations. This operation should be happened before any general operations and processed independently of an application layer. Note that in general operations, sending unicast Neighbor Solicitation of an old AR and multicasting RS are happen after the failure of application layer operation trial or other layer operation trial. In some test, we found it takes a few seconds. After an AcAR receive this RS message, it can do movement detection operation. The AcAR compare the L2 identifier of a MN (MAC address in case of 802.11) with the values in neighbor caches. The comparison results in two cases. - The L2 identifier is not found in neighbor cache. It means that the MN is a new comer of the subnet area of the AcAR. So the AcAR prepare CoA generation and DAD operation. This situation is that the MN is moved between each AR which has a different subnet prefix. - The L2 identifier is found in neighbor caches. It means that the MN is already served by the AcAR. So the AcAR does not have to do CoA generation and DAD operation. The only thing needed is that the AcAR must immediately inform it to the MN and enables the MN to continuously use the existing CoA. This situation is that the MN is not moved between each AR which has a different subnet prefix. For example, in 802.11 networks, the MN is moved between different AP but each AP is connected to the same AR. In this case, L2 handoff is happened, but L3 handover is not happened. So other CoA configuration and DAD operation for the MN is unnecessary. 3.2 CoA configuration and Duplicate Address Detection If an AcAR decides to generate a CoA for a MN, it uses its prefix information and L2 information of the MN which is included in Source link-layer address options of RS. As described in IPv6 Stateless Address Autoconfiguration [12], a CoA is generated using normal IPv6 mechanism. An AcAR already has a prefix as one router and L2 information is provided by a modified RS messages. After configuration of a new CoA, an AcAR does DAD operation on behalf of a MN. If DAD is succeeded, an AcAR can deliver the CoA to a MN. If DAD is failed, it follows normal IPv6 mechanism. 3.3 Delivering new CoA to MN When a MN requests a CoA through a modified RS message, an AcAR responds to the MN with a modified RA message which includes a new CoA. When L3 movement is not happened even thought L2 handoff is Hong, Shin, Park, Kim Expires: April 2004 [Page 4] AR-Based MD and CoA Configuration June 2003 happened, an AcAR informs it to an MN and enables the MN to continuously use the existing CoA immediately after movement detection. 4. Modification to IPv6 Neighbor Discovery 4.1 Modified Router Solicitation Message Format Host sends Router Solicitations in order to prompt routers to generate Router Advertisements quickly [13]. Like this, a MN can send modified RS messages to AcARs to obtain a new CoA. To do this, we modify the basic RS message by the addition of a single flag bit (C) to indicate that the MN sending the RS message wants to get a new CoA from AcARs. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |C| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source link-layer address options +-+-+-+-+-+-+-+-+-+-+-+- This format represents the following changes over that originally specified for Neighbor Discovery [13]. CoA Generate (C) 1-bit CoA generate flag. When set, indicates that this RS message is to request AcARs to generate a new CoA and respond Reserved Reduced from a 32-bit field to a 31-bit field to account for the addition of the above bit Options Use Source link-layer address options. This options is used to check the proper node for assigning new CoA by AcAR 4.2 Modified Router Advertisement Message Format Routers send out Router Advertisement messages periodically, or in response to a router Solicitation [13]. Like this, an AcAR responds to the above RS message. We modify the basic RA message by the addition of a single flag bit (C) to indicate that the modified prefix information option includes the new generated CoA for the MN. Hong, Shin, Park, Kim Expires: April 2004 [Page 5] AR-Based MD and CoA Configuration June 2003 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cur Hop Limit |M|O|H|C|Res... | Router Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reachable Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Retrans Timer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix Information options +-+-+-+-+-+-+-+-+-+-+-+- This format represents the following changes over that originally specified for MIPv6 [1]. CoA Generate (C) 1-bit CoA generate flag. When set, indicates that this RA message is advertised by an AcAR and the prefix information option in this RA message includes the new generated CoA for the MN. Reserved Reduced from a 5-bit field to a 4-bit field to account for the addition of the above bit Options Use the modified prefix information option. This option is used to deliver the generated CoA to the MN by AcAR. 4.3 Modified Prefix Information Option Format MIPv6 extends Neighbor Discovery to allow a router to advertise its global address, by the addition a single flag bit in the format of a prefix information for use in a RA message [1]. Like this, we modify the prefix information option by the addition a single flag (C) bit to indicate that the prefix field in this option contains the CoA for the MN. 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 | Prefix Length |L|A|R|C|Res.. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Valid Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Preferred Lifetime | Hong, Shin, Park, Kim Expires: April 2004 [Page 6] AR-Based MD and CoA Configuration June 2003 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Prefix + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This format represents the following changes over that originally specified for MIPv6 [1]. CoA Generate (C) 1-bit CoA generate flag. When set, indicates that the prefix field contains a complete IP address that will be assigned to the MN as a CoA. Reserved Reduced from a 5-bit field to a 4-bit field to account for the addition of the above bit Prefix The complete IP address which is generated by an AcAR for a CoA of the MN. If the IP address is the same to the existing CoA of MN, it indicated that the MN can use the existing CoA even though L2 handoff. Security Considerations In our proposed scheme, a delivering of L2 triggers to a network layer of a MN may not be security issues because it operates in a system. Security issues of using a modified RS, RA message and modified Prefix Information Option is not beyond the scope of Neighbor Discovery and MIPv6. References [1] D. Johnson, C. Perkins, J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-24.txt (work in progress), June 2003 [2] Koodli, R., "Fast Handovers for Mobile IPv6", draft-ietf-mipshop- fast-mipv6-00.txt (work in progress), October 2003. [3] J. Kempf, M. Khalil, B. Pentland. "IPv6 Fast Router Advertisement", draft-mkhalil-ipv6-fastra-03.txt, March 2002. Hong, Shin, Park, Kim Expires: April 2004 [Page 7] AR-Based MD and CoA Configuration June 2003 [4] JinHyoeck Choi, DongYun Shin. "Fast Router Discovery with RA", draft-jinchoi-mobileip-frd-00.txt (work in progress), Feb 2003. [5] B. Pentland, G. Daley, "Router Advertisement Link Identification for Mobile IPv6 Movement Detection", draft-pentland-mobileip- linkid-00.txt (work in progress), May 2003. [6] Youngjune Gwon, A. Yegin, "Enhanced Forwarding from Previous Care-of Address for Fast Mobile IPv6 Handovers (eFWD)", draft-gwon-mobileip-efwd-fmipv6-01.txt, June 2002. [7] N. Moore, "Optimistic Duplicated Address Detection", draft-moore- ipv6-optimistic-dad-01.txt (work in progress), Feb 2003. [8] Y. Han, Y. Choi, S. Park, "Advance Duplicate Address Detection", draft-han-mobileip-adad-00.txt (work in progress), June 2003. [9] A. Yegin, et al, "Supporting Optimized Handover for IP Mobility- Requirements for Underlying Systems", draft-manyfolks-l2- mobilereq-02.txt, June 2002. [10]"Recommended Practice for Multi-Vendor Access Point Interoperability via an Inter-Access Point Protocol Across Distribution Systems Supporting IEEE 802.11 Operation," IEEE Std 802.11f/D1, DRAFT. [11] A. Yegin, "Link-layer Triggers Protocol", draft-yegin-l2- triggers-00.txt, June 2002. [12] Thomson, S. and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [13] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. Acknowledgments Thanks to Hee Young Jung, Seok Joo Koh and Kyeong Jin Lee for providing valuable feedback and contributing to this draft. Author's Addresses Yong-Guen Hong ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Tel : +82 42 860 6447 Hong, Shin, Park, Kim Expires: April 2004 [Page 8] AR-Based MD and CoA Configuration June 2003 Fax : +82 42 861 5404 E-mail : yghong@etri.re.kr Myung-Ki Shin ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Tel : +82 42 860 4847 Fax : +82 42 861 5404 E-mail : mkshin@etri.re.kr Jung-Soo Park ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Tel : +82 42 860 6514 Fax : +82 42 861 5404 E-mail : pjs@etri.re.kr Hyoung-Jun Kim ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Tel : +82 42 860 6576 Fax : +82 42 861 5404 E-mail : khj@etri.re.kr Hong, Shin, Park, Kim Expires: April 2004 [Page 9]