INTERNET DRAFT JinHyeock Choi Expires: November 2002 DongYun Shin Samsung AIT May 2002 Fast Router Discovery with AP Notification 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 Fast Router Discovery with AP Notification. 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 an Access Point, 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 References Choi, Shin Expires March 2002 [Page 1] INTERNET DRAFT Fast Router Discovery May 2002 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. 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. 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 before a mobile node sends an initial Router Solicitation, it SHOULD delay the transmission for a random amount of time. 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. 3. Proposal Overview In Wireless LAN technology, when a MN (mobile node) arrives at a new link, it should associate with its new AP. Choi, Shin Expires March 2002 [Page 2] INTERNET DRAFT Fast Router Discovery May 2002 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 RAs, 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. 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 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. Choi, Shin Expires March 2002 [Page 3] INTERNET DRAFT Fast Router Discovery May 2002 References [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, draft-ietf-mobileip-ipv6-17.txt, May 2002 [3] J. Kempf, M. M Khalil and B. Pentland, IPv6 Fast Router Advertisement, draft-mkhalil-ipv6-fastra-00.txt, April 2002 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 March 2002 [Page 4]