NEMO Working Group E. K. Paik Internet-Draft H. S. Cho Expires: April 16, 2004 Seoul National University T.Ernst Keio University October 17, 2003 Multihomed Mobile Networks Problem Statements 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. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document describes the needs for multihoming support in network mobility (NEMO). Issues from designing and implementing multihomed mobile networks are analyzed in terms of mutiple connections management and usage. Table of Contents Paik, et al. Apr. 16, 2004 [Page 1] INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terms and Abbreviation . . . . . . . . . . . . . . . . . . . . 2 3. The need for Multihoming. . . . . . . . . . . . . . . .. . . . 2 4. Issue Statements . . . . . . . . . . . . . . . . . . . . . . . 3 5. Route Optimization Considerations. . . . . . . . . . . . . . . 4 6. Security Considerations. . . . . . . . . . . . . . . . . . . . 4 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction Multihomed mobile networks [1] provide advantage of enhancing session continuity and load balancing to the whole mobile networks. NEMO is based on mobile IPv6 [2], but multihoming in NEMO raises new problems that do not arise in mobile IPv6. In this document, a case is made for why multihoming is needed for NEMO and what the prerequisite issues for developing multihomed mobile networks. 2. Terms and Abbreviation It is assumed that readers are familar with the terminologies and abbreviations as defined in [1] and [2], and classifications in [3]. 3. The need for multihoming There are two basic motivations for multihoming. 1) Multihomed mobile networks enhance the session preservation of the mobile router (MR) used for mobile network nodes (MNNs). Since a wireless link is not as stable as a wired link, session preservation is an important issue in the case of mobile networks. Especially in the case of NEMO, the session preservation of the MR concerns not only the MR itself but also the one or more MNNs behind it. If the MR can not maintain a continuous session, more than one or more MNNs will not be able maintain their sessions either. As the number of MNNs increases, the impact of MR session disconnection also increases. Therefore the session preservation of the MR is critical in NEMO. 2) Multihomed mobile networks share traffic load more efficiently by selecting the best available connection or enabling multiple connections simultaneously. Since all traffic goes through the MR in a mobile network, load sharing at the MR is critical. Paik, et al. Apr. 16, 2004 [Page 2] INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003 4. Issue Statements 4.1 Connection availability Multiple connections of MRs can be used simultaneously or one at a time. 1) When multiple connections are used simultaneously, the mode of operation can be either primary-secondary or peer-to-peer. These configurations can be useful especially for large mobile networks, but there are many implementation issues which need to be addressed, e.g. which connection will be selected for each traffic folw that goes into/out of the mobile network ? 2) When only one connection can be used at a time, e.g. in the case where a single connection has to substitute for all of the other failed connections, a connection selection mechanism is needed. The connection selection can depend on which connection is available at that time. 4.2 Connection selection 4.2.1 Who selects a connection ? The connection can be selected by the home agent (HA), the MR, and/or the MNN. 1) The HA can select a connection based on the binding update information in the binding cache. 2) The MR can select a connection since the MR is one of the main bodies of the connection. 3) The MNN should be able to select a connection, e.g. in case where a user wants to select a particular access technology among the available technologies for reasons of cost or data rate. 4) A hybrid mechanism should be also available, e.g. one in which the HA, the MR, and/or the MNN coordinate to select a connection. 4.2.2 Connection selection problem analysis Connection selection problem can be analyzed as follows. 1) Selection by the HA: HAs coordination is needed when there are multiple HAs. 2) Selection by the MR: This should allow communication between MRs in the case where there is multihoming with multiple MRs. [4] is an examples of MRs coordination for selecting a connection. Paik, et al. Apr. 16, 2004 [Page 3] INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003 3) Selection by the MNN: The MNN selects an MR when there are multiple MRs. For example, it can be a problem of prefix selection when MRs advertise different prefixes. The MNN selects a HA when there are multiple HAs. For example, it can be a problem of Internet service provider (ISP) selection when each HA is associated with different ISP. Multiple HAs can be associated with different locations, access technologies, ISPs, and so on. 4.3 Scalability Should a new solution meets the all the eight configurations and the scenarios mentioned in [3]? 5. Route Optimization Considerations RO problems in multihomed mobile networks are dependant on how the connections are available and selected. 1) In case of multiple HAs and HoAs, new route optimization may be possible by routing between CN and multiple HAs with different HoAs. 2) When multiple connections are available simultaneously, how the CN knows about the availability and optimizes route ? 6. Security Considerations Security threats are dependant on how the connections are available and selected. So we will add security problems when they are encountered as the basic multihoming issues in NEMO are analyzed. References [1] Ernst, T. and H. Lach, "Network Mobility Support Terminology", Internet Draft: draft-ietf-nemo-terminology-00.txt, Work In Progress, May 2003. [2] Johnson, D. B., Perkins, C. E. and Arkko, J., "Mobility Support in IPv6", Internet Draft: draft-ietf-mobileip-ipv6-24.txt, Work In Progress, June 2003. [3] C. Ng, J. Charbon, í—Multi-Homing Issues in Bi-directional Tunneling,í˜ Internet Draft: Paik, et al. Apr. 16, 2004 [Page 4] INTERNET-DRAFTMultihomed Mobile Networks Problem StatementsOct. 17, 2003 draft-ng-nemo-multihoming-issues-01.txt, Work In Progress, May 2003. [4] Eun Kyoung Paik and Yanghee Choi, "Management of Multiple Mobile Routers for Continuous Multimedia in Mobile WLANs," Lecture Notes in Computer Science, Springer-Verlag, vol. 2532, Dec. 2002, pp.680-687. Authors' Addresses Eun Kyoung Paik Multimedia and Computer Communications Lab. Seoul National University ENG4190, School of Electronic Engineering and Computer Science Seoul National University Seoul 151-744, Korea Phone: +82 2 880 1832 Fax: +82 2 872 2045 EMail: eun@mmlab.snu.ac.kr URL: htpp://mmlab.snu.ac.kr/~eun Ho-Sik Cho Multimedia and Computer Communications Lab. Seoul National University ENG4190, School of Electronic Engineering and Computer Science Seoul National University Seoul 151-744, Korea Phone: +82 2 880 1832 Fax: +82 2 872 2045 EMail: hscho@mmlab.snu.ac.kr URL: htpp://mmlab.snu.ac.kr/~hscho Thierry Ernst Jun Murai Lab. Keio University K2 Town Campus 1488-8 Ogura, Saiwai-ku, Kawasaki Kanagawa 212-0054 Japan Phone: +81-44-580-1600 EMail: ernst@sfc.wide.ad.jp URL: htpp://www.sfc.wide.ad.jp/~ernst Paik, et al. Apr. 16, 2004 [Page 5]