Mipshop Working Group K. Mitsuya Internet-Draft Keio University Expires: November 3, 2005 May 2, 2005 Keep Old Binding Cache for a bit draft-mitsuya-keep-old-bc-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 November 3, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The FMIPv6 specification [1] allows mobile node sending packet using previous Care of Address (PCoA) at a new subnet. But such packets are ignored at home agent or correspondent node because the Binding Cache doesn't contain the PCoA anymore. To avoid this problem, we propose keeping old binding cache for a bit. Mitsuya Expires November 3, 2005 [Page 1] Internet-Draft Keep Old Binding Cache for a bit May 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement: Ignored packets . . . . . . . . . . . . . . 3 3. Solution: Keep old binding cache . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . 6 Mitsuya Expires November 3, 2005 [Page 2] Internet-Draft Keep Old Binding Cache for a bit May 2005 1. Introduction Fast Handover for Mobile IPv6 (FMIPv6) [1] describes a protocol to reduce the handover latency and the packet loss. The specification address the following problems: how to allow a mobile node to send packets as soon as it detects a new subnet link, and how to deliver packets to a mobile node as soon as its attachment is detected by the new access router. However, there is a packet loss caused by mis-matching of Binding Update List and Binding Cache. Even if the specification allows mobile node sending packet using previous Care of Address (PCoA) at a new subnet, such packets might be ignored at home agent or correspondent node because Binding Cache doesn't contain the PCoA anymore. This document describes the packet loss problem and proposes keeping old Binding Cache to save such ignored packets. 2. Problem Statement: Ignored packets In the FMIPv6 specification [1], when mobile node moves to a new access network, it sends packets using PCoA as source address until it receives Binding Acknowledgment for its new Care of Address (NCoA). Once home agent receives the BU, the home agent MUST update its existing Binding Cache entry according to the MIPv6 specification [2]. This means that the home agent removes previous Binding Cache entry and replace it with the new one. There is a short period when Binding Update List and Binding Cache are not the same. It's from home agent updates its Binding Cache to mobile node receives the corresponding Binding Acknowledgment. At this period, mobile node sends packets, not MIPv6 signaling but normal data packets using PCoA, and home agent ignores those packets because Binding Cache doesn't contain PCoA anymore. This period is estimated as round-trip-time from mobile node to home agent. Here is a similar problem on the normal MIPv6 node. For example, a normal mobile node may have two interfaces, one is cellular (300ms between mobile node and home agent) and one is WiFi (20ms). In this typical situation, once the mobile node switches its interface from cellular to WiFi, the BU via WiFi may reach earlier than some packets via cellular. Let's say A is data packet (not MIPv6 signal) sent through cellular, B is BU sent through WiFi, and C is data packet via WiFi. mobile node sent packets in order as AAAAABCCCCC, but home agent may receive as, for example, AAABAACCCCC. The A packets between B and C are just Mitsuya Expires November 3, 2005 [Page 3] Internet-Draft Keep Old Binding Cache for a bit May 2005 ignored. We want to save those packets because they are sent correctly. 3. Solution: Keep old binding cache To avoid this problem, we propose keeping old binding cache for a bit. Once home agent receives the BU, the home agent MUST update its existing Binding Cache entry and also SHOULD keep the existing Binding Cache entry for OldBCLifetime ms. OldBCLifetime is estimated as round-trip-time from mobile node to home agent. o OldBCLifetime Default: 300ms A home agent then keeps two or more BC entries for one home address. The latest Binding Cache SHOULD be used for forwarding packets from correspondent node to mobile node, the old Binding Caches are used only for receiving packets sent from mobile node. If a mobile node moves quickly between several networks, a home agent SHOULD keep several Binding Cache entries for one home address. 4. Security Considerations This proposal does not introduce new security threats than those already described in [1]. 5. Acknowledgment The authors would like to thank all those who have provided feedback on this specification, but can only mention a few here: Julien Bournelle, Keiichi Shima, Koki Mitani, Rajeev Koodli and Ryuji Wakikawa. 6. References [1] Koodli, R., "Fast Handovers for Mobile IPv6", draft-ietf-mipshop-fast-mipv6-03 (work in progress), October 2004. [2] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. Mitsuya Expires November 3, 2005 [Page 4] Internet-Draft Keep Old Binding Cache for a bit May 2005 Author's Address Koshiro Mitsuya Keio University 5322 Endo Fujisawa, Kanagawa 252-8520 Japan Phone: +81 466 49 1100 Email: mitsuya@sfc.wide.ad.jp URI: http://www.sfc.wide.ad.jp/~mitsuya/ Mitsuya Expires November 3, 2005 [Page 5] Internet-Draft Keep Old Binding Cache for a bit May 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Mitsuya Expires November 3, 2005 [Page 6]