INTERNET DRAFT JinHyeock Choi Expires: August 2003 DongYun Shin Samsung AIT February 2003 Fast Router Discovery with RA Caching in AP 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 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 obsolete by other documents at anytime. 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 presents RA Caching in AP for Fast Router Discovery. For seamless handoff, a mobile node MUST quickly discover its new access router. In our proposal AP caches Router Advertisement message and sends it to a new mobile node as soon as L2 association is made. We present a way for AP to cache necessary RA. By putting 'RA Caching' and 'AP Notification' functionality on AP, we get the optimized result without IPv6 standard change. Table of Contents: 1. Introduction 2. Terminology 3. Proposal Overview 4. Operation Description 4.1 RA Caching 4.2 AP Notification 5. L2 trigger Choi, Shin Expires August 2003 [Page 1] INTERNET DRAFTFast Router Discovery with RA Caching in AP February 2003 6. Security Considerations References 1. Introduction The primary movement detection mechanism for Mobile IPv6 defined in [2] uses the facilities of IPv6 Neighbor Discovery [1], including Router Discovery and Neighbor Unreachability Detection. A mobile node MUST quickly detect when it moves to a link served by a new access router, so that it can acquire a new care-of address and send Binding Updates quickly. A mobile node MUST receive Router Advertisement from a new access router as soon as possible. There are several hindrances for sufficiently fast Router Discovery. First, Neighbor Discovery protocol [1] limits routers to a minimum interval of 3 seconds between sending unsolicited multicast Router Advertisement messages. Second, it SHOULD delay the transmission for a random amount of time before a mobile node sends an initial Router Solicitation. Third, a router MUST delay a response to a Router Solicitation by a random time too. Though solutions are proposed by [2],[3], they require IPv6 standard [1] change. In our proposal AP (Access Point) caches RA (Router Advertisement) message and sends it to a new mobile node as soon as L2 association is made. We present a way for AP to cache necessary RA. By putting 'RA Caching' and 'AP Notification' functionality on an Access Point, we get the optimized result without IPv6 standard change. In our scheme, mobile node receives Router Advertisement just after L2 association is made which is the earliest possible time under current standard. 2. Terminology 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. Access Router (AR) An Access Network Router residing on the edge of an Access Network and offers IP connectivity to mobile nodes Access Point (AP) An L2 entity that has station functionality and provides access to the distribution services, via the wireless medium for associated stations. Choi, Shin Expires August 2003 [Page 2] INTERNET DRAFTFast Router Discovery with RA Caching in AP February 2003 3. Proposal Overview In 802.11 b Wireless LAN technology, when a MN (mobile node) arrives at a new link, it should associate with its new AP. In our proposal, AP caches RA message beforehand and sends it to a mobile node as soon as L2 association is made. We can cache RA in AP manually or use the following scheme. AR (Access Router) periodically multicasts unsolicited RA, which go through AP. So AP can scan incoming L2 frames and cache necessary RA. AP scans L2 frame either continuously or periodically to update stored RA. Moreover if AR and AP are under same network administration, they can be configured such that AP caches RA efficiently. 4. Operation Description Our proposal consists of 'RA Caching' and 'AP Notification', RA Caching periodically scans incoming L2 frame for unsolicited RA and stores it. AP Notification sends stored RA to new MN as soon as L2 association is made. 4.1. RA Caching AP scans incoming L2 frame for unsolicited RA. First it scans L2 frame header to see whether it is a multicast frame. If not, AP sends that frame down link and scans next L2 frame. If so, AP looks IP header to check whether it contains unsolicited RA. If incoming L2 frame doesn't contain unsolicited RA, AP sends that frame down link and scans next L2 frame. When AP finds unsolicited RA, it stores it and sends a copy down link. AP can scan continuously, updating old RA with new RA. Or if it costs too much for AP to scan every incoming L2 frame, we can control the scanning rate. For example, we can set timer and execute scanning every T seconds. Or we can make AP to be able to send Router Solicitation message. Periodically AP sends Router Solicitation. Then AR will send RA and AP caches it. It is noted that AP doesn't need to have IP address since it can use unspecified address as its source address. 4.2. AP Notification Choi, Shin Expires August 2003 [Page 3] INTERNET DRAFTFast Router Discovery with RA Caching in AP February 2003 When a new MN arrives at AP, it sends Association Request Message with its MAC address. Then AP grants association by sending Association Response Message. As soon as association is made, AP sends stored RA to a new MN with MAC address in Association Request message. MN receives RA just after association is made which is the earliest possible time in current standard. 5. L2 trigger L2 trigger is a notification from L2 that a certain event has happened or is about to happen. We formulate our poposal as a trigger like below. L2 Event Recipient Parameters Trigger +-------------+---------------+------------+-----------------+ | Fast | When new L2 | MN | Router | | Router | association | | Advertisement | | Discovery | is made. | | | In other way, the above trigger may be incorporated with Link Up trigger. We can add Router Advertisement message as a new parameter for Link Up Trigger. 6. Security Considerations Since our proposal is based on Neighbor Discovery, its trust models and threats are similar to the ones presented in [5]. There are also Movement Detection specific threats described in 8.0 of [4]. If higher layer notification of connectivity is not available, and eager handoff strategies are in place, any node or router which advertises an RA with a false prefix will cause mobile nodes to perform spurious handover signalling and DAD operations. But above threats are inherent to all schemes which depends exclusively on Router Discovery for movement detection. Our proposal doesn't incur any additional threats. We will incorporate the solutions developed in IETF SEND Working Group when available. References Choi, Shin Expires August 2003 [Page 4] INTERNET DRAFTFast Router Discovery with RA Caching in AP February 2003 [1] T. Narten, E. Nordmark and W. Simpson, Neighbor Discovery for IP Version 6 (IPv6), RFC 2461, December, 1998. [2] D. Johnson, C. Perkins and J. Arkko, Mobility Support in IPv6, Internet-Draft (work in progress), January 2003 [3] J. Kempf, M. M Khalil and B. Pentland, IPv6 Fast Router Advertise- ment, Internet-Draft (work in progress), October 2002 [4] G. Daley and JinHyeock Choi, Movement Detection Optimization in Mobile IPv6, Internet-Draft (work in progress), February 2003 [5] P. Nikander, J. Kempf and E. Nordmark, IPv6 Neighbor Discovery trust models and threats, Internet-Draft (work in progress), Jan- uary 2003 Author's Addresses JinHyeock Choi i-Networking Lab, Samsung AIT (SAIT) Phone: +82-31-280-9233 Email: athene@sait.samgung.co.kr DongYun Shin i-Networking Lab, Samsung AIT (SAIT) Phone: +82-31-280-9552 Email: yun7521@samgung.co.kr Choi, Shin Expires August 2003 [Page 5]