IETF MIP6 Working Group N. Montavont Internet-Draft LSIIT - ULP Expires: January 17, 2005 R. Wakikawa Keio University T. Ernst WIDE at Keio University T. Noel LSIIT - ULP C. Ng Panasonic Singapore Labs July 19, 2004 Analysis of Multihoming in Mobile IPv6 draft-montavont-mobileip-multihoming-pb-statement-01.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 January 17, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract Individual solutions have been proposed to extend Mobile IPv6 in order to allow mobile nodes to be multihomed, but all issues have not Montavont, et al. Expires January 17, 2005 [Page 1] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 been addressed by a single document. In this document, we thus propose a taxonomy to classify the situations where a mobile node may be multihomed. This taxonomy is then used to describe all multihomed scenarios. Issues preventing mobile nodes to be multihomed while operating Mobile IPv6 are highlighted. This document doesn't aim at proposing solutions, however, it is expected to raise discussion in order to make sure forthcoming solutions will address all the issues. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1 Issues Related to Mobile IPv6 . . . . . . . . . . . . . . 8 4.2 Issues Not Related to Mobile IPv6 . . . . . . . . . . . . 8 4.3 Issues Related to a Host Connected to Home Link . . . . . 9 5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . 12 Montavont, et al. Expires January 17, 2005 [Page 2] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 1. Introduction Mobile IPv6 [4],[5] is designed to allow a mobile node to maintain its IPv6 communications while moving between IPv6 subnets. However, the current specification does not give hints nor requirements to deal with mobile nodes with multiple points of attachement, i.e. a multihomed mobile node. We are thus proposing the current document to fill this gap. This document has two goals. The first goal is to define a taxonomy which helps to represent the different situations where a mobile host is multihomed. For each case, we show the configuration a multihomed host may have (number of interfaces, number of Home Addresses or number of Care-of Addresses). We also give a concrete illustration for each scenario. The second goal of this document is to define the requirements needed to manage multihomed hosts. Different issues will be raised in order to provide full support of multihomed hosts in Mobile IPv6. The potentially needed solutions to support new features will be described in a separate document. The reader is assumed to have read our companion document [1] which outlines the goals and benefits of multihoming for both fixed and mobile nodes (i.e. generic IPv6 nodes). Real-life scenarios as illustrated in that document are the based motivations of this present study of multihomed issues peculiar to mobile nodes. The terms used in this memo are the same as the ones used in Mobile IPv6 [4]. The document is organized as follows: in the first section, we propose a taxonomy to classify the different cases where mobile hosts are multihomed. Then this taxonomy is used to describe the multihoming scenarios specific to Mobile IPv6. In the next section, an analysis of each case is given in order to select the most interesting scenarios highlighted in the previous section. The last section summarizes the different features needed in Mobile IPv6 to reach the goal defined in [1]. Montavont, et al. Expires January 17, 2005 [Page 3] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 2. Taxonomy As detailed in [1], multihoming can provide a number of benefits: ubiquitous access, redundancy/fault recovery, load sharing, load balancing, bicasting and preferences settings. In that document, the multihoming study is split into two main axes: either the node has only one interface (and several IPv6 addresses) or the node has several interfaces. In this memo, we follow the same guidelines, but we conduct this study from the pespective of mobile nodes operating Mobile IPv6 specifically. However, two more parameters are necessary to study the feasability of each goal: the multihoming management will be different according to the number of Home Addresses and the number of Care-of Addresses the mobile node has. We then proposes the following taxonomy: o x = number of active interfaces o y = number of Home Addresses (HoAs) o z = number of Care-of Addresses (CoAs) A value of '1' implies there is a single instance of the parameter, whereas a value of 'n' indicates that there are multiple instances of the parameter. An illustration of this taxonomy is given in Figure 1. Montavont, et al. Expires January 17, 2005 [Page 4] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 Mobile Node HoA1 HoA2 ... HoAn --> Mobile IP layer (x) | | | +-----+--------+ | | | | | | | CoA1 +--CoA2 +---CoA3 ... CoAn --> IP layer (y) | | | | Link1 Link2 Link3 ... Linkn --> IPv6 Link (n/a *) | | | | +-----+----+ | | | | | IF1 IF2 ... IFn --> Physical layer (z) (z = the number of active interfaces) HoA1 ::= {CoA1, 2, 3} [IF1 and IF2] HoA2 ::= {CoA3} [IF2] Mobile Node(x = 2, y = 3, z = 2) * because number of IPv6 link is equal to the number of CoAs, equal to y Figure 1: Illustration of the chosen taxonomy The variable y indicates the number of HoAs allocated to a host. A host may have multiple HoAs (x=n) when either: o The host has only one home link, and all its HoAs are based on the same IPv6 prefix (e.g. the host may have multiple interfaces). o The host has only one home link, and multiple HoAs with distinct prefixes because there are several IPv6 prefixes advertised on the home link. o The host has several home links, and thus has at least two HoAs with different IPv6 prefixes. As the taxonomy suggests, the fact that the mobile node has several HoAs is independent from the fact that the mobile node has multiple interfaces. The fact that the mobile node has multiple interfaces does not imply that it has multiple HoAs and vice-versa. Montavont, et al. Expires January 17, 2005 [Page 5] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 3. Scenarios o x = 1: only one interface on the host 1. One HoA, one CoA (1,1,1) The host is not multihomed. The host has only one interface, with one HoA and is currently away from its home link (one CoA on the foreign link). 2. Several HoAs, one CoA (1,n,1) The host is multihomed, since it has several HoAs. This case may happen when a host is getting access to Internet through different ISPs and each offers a Mobile IPv6 service to the host. That way, the host will have a HoA per ISP. Once the host is connected to a visited IPv6 subnet, it gets one CoA. This CoA may be registered with all the Home Agents provided by the ISPs, in order to remain simulteneously reachable through all its HoAs. 3. One HoA, several CoAs (1,1,n) The host is multihomed since it has several CoAs. This case may occur when the interface of the host is connected to a link where multiple IPv6 prefixes are advertised. 4. Several HoAs, several CoAs (1,n,n) The host is multihomed, since it has multiple addresses. This case can be viewed as a combination of the two cases described above: the host has several HoAs (e.g. given by different ISPs) and several CoAs (e.g. because the host is receiving multiple IPv6 prefixes). o x = n: the host has multiple interfaces 1. One HoA, one CoA (n,1,1) The host is multihomed: this is a special case of a host with two interfaces connected to different IPv6 subnets; one of the subnet is the home network of the host and allows the host to use its HoA. The host can build a temporary IPv6 address on its other interface but it cannot register the temporary address with its Home Agent (unless the host stops using its HoA, i.e. its interface connected to the home link). 2. One HoA, several CoAs (n,1,n) Montavont, et al. Expires January 17, 2005 [Page 6] The host is multihomed: the host has several addresses to choose from. For example, consider a host with several interfaces, each connected to an IPv6 network (the same or not). In this example, at least one IPv6 address is configured on each interface. The host has only one home link, and only one Home Agent. 3. Several HoA, one CoA (n,n,1) The host is multihomed. This case extends the case (n,1,1) when the host has several HoAs, for example from multiple ISPs. 4. Several HoAs, several CoAs (n,n,n) The host is multihomed. Many scenarios may lead to this case. For example, consider a host with three interfaces, two of them connected to their home link(two different HoAs) and the last one connected to a visited link where two IPv6 prefixes are advertised. Montavont, et al. Expires January 17, 2005 [Page 7] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 4. Open Issues In this section we highlight open issues which have to be taken into account to handle a multihomed host using Mobile IPv6 and we list the requirements for a Mobile IPv6 node to benefit from its multihomed configuration in an optimized fashion. To meet some of these requirements, specific procedures in the Mobile IPv6 specification will be required. It's not the purpose of this document to provide solutions to meet these requirements but we give some hints. Solutions to meet these requirements will be defined in a separate document. 4.1 Issues Related to Mobile IPv6 1. In the (*,n,*) cases when the mobile host otains a new CoA, it's not clear to which HoA the new CoA would be bound to. There is thus a need to define a relationship between HoAs and CoAs. 2. In the (*,1,n) case, several CoAs may be simultaneously used by a mobile node. In this case, the host must be able to register all CoAs with a single HoA on a distant node (Correspondent Node or Home Agent). This questions how to manage multiple CoAs bound to a single HoA and how to identify an entry in the Binding Cache. Solutions like [10] may be used. 4.2 Issues Not Related to Mobile IPv6 1. In the (n,*,*) cases, the solution should bring support to allow a mobile host to simultaneously use several interfaces, regardless the number of HoAs and CoAs the mobile node may have. 2. In the (*,n,*) case, a mechanism should be defined to detail how to bind multiple HoAs to a host. 3. In the (n,*,*) cases, a mechanism is needed to redirect flows from one interface to another: this functionality would allow a mobile node to pursue all communication flows that were initiated over the failed interface before it is down. 4. In the (n,1,1) case again, the node may want to use each interface differently according to some policies and preferences that would define which flow would be mapped to which interface and/or which flow should not be used over a given interface. In order to optimize the global connectivity of a multihomed host, a solution may be defined to allow multihomed hosts to set filters on flows on distant nodes (Correspondent Node or Home Agent), such as mechanisms proposed by [7], [8] and [9]. Montavont, et al. Expires January 17, 2005 [Page 8] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 4.3 Issues Related to a Host Connected to Home Link In the (n,*,*) cases listed in Section 3, the host may have one of its interfaces directly connected to a home link. This may have an impact on the multihoming management. For example, if we consider the case (n,n,n) with a host having three interfaces, three HoAs and two CoAs (connected to two visited IPv6 subnets), the CoAs cannot be registered with the Home Agent serving the host on the home link it is connected to. Otherwise, the case (n,n,n) can translate into either case (n,n,1) or (n,n,0) according to the way the host is connected to the Internet. Case (n,n,1) only happens when the host is connected to a visited link with only one interface and obtain only one CoA. Other interfaces are connected to the home link(s). In the case (n,n,0), i.e. several interfaces, several HoAs, and no CoA, all interfaces of the host are connected to their respective home links. Some Mobile IPv6 features cannot be used when the host is connected to the same link as its Home Agent (e.g. home registration). So, such specific scenrarios must be considered by the solutions. 5 References [1] Ernst, T., "Goals and Benefits of Multihoming", draft-multihoming-generic-goals-and-benefits-00 (work in progress), February 2004. [2] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC 3753, June 2004. [3] Ernst, T. and H. Lach, "Network Mobility Support Terminology", draft-ietf-nemo-terminology-01 (work in progress), February 2004. [4] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [5] Arkko, J., Devarapalli, V. and F. Dupont, "Using IPsec to Protect Mobile IPv6 Signaling Between Mobile Nodes and Home Agents", RFC 3776, June 2004. [6] Montavont, N., Noel, T. and M. Kassi-Lahlou, "MIPv6 for Multiple Interfaces", draft-montavont-mobileip-mmi-00 (work in progress), July 2002. [7] Soliman, H., Malki, K. and C. Castelluccia, "Per-flow movement Montavont, et al. Expires January 17, 2005 [Page 9] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 in MIPv6", draft-soliman-mobileip-flow-move-02 (work in progress), July 2002. [8] Montavont, N. and T. Noel, "Home Agent Filtering for Mobile IPv6", draft-montavont-mobileip-ha-filtering-v6-00 (work in progress), January 2004. [9] Kuladinithi, K., "Filters for Mobile IPv6 Bindings (NOMADv6)", draft-nomadv6-mobileip-filters-02 (work in progress), June 2004. [10] Wakikawa, R., "Multiple Care-of Addresses Registration", draft-wakikawa-mobileip-multiplecoa-02 (work in progress), September 2003. [11] Stemm, M. and R. Katz, "Vertical Handoffs in Wireless Overlay Networks", Journal Mobile Networks and Applications, vol. 3, number 4, pages 335-350, 1998. Authors' Addresses Nicolas Montavont LSIIT - Univerity Louis Pasteur Pole API, bureau C444 Boulevard Sebastien Brant Illkirch 67400 FRANCE Phone: (33) 3 90 24 45 87 EMail: montavont@dpt-info.u-strasbg.fr URI: http://www-r2.u-strasbg.fr/~montavont/ Wakikawa Ryuji Keio University Jun Murai Lab., Keio University. 5322 Endo Fujisawa, Kanagawa 252-8520 Japan Phone: +81-466-49-1100 Fax: +81-466-49-1395 EMail: ryuji@sfc.wide.ad.jp URI: http://www.mobileip.jp/ Montavont, et al. Expires January 17, 2005 [Page 10] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 Ernst Thierry WIDE at Keio University Jun Murai Lab., Keio University. K-square Town Campus, 1488-8 Ogura, Saiwa-Ku Kawasaki, Kanagawa 212-0054 Japan Phone: +81-44-580-1600 Fax: +81-44-580-1437 EMail: ernst@sfc.wide.ad.jp URI: http://www.sfc.wide.ad.jp/~ernst/ Thomas Noel LSIIT - Univerity Louis Pasteur Pole API, bureau C444 Boulevard Sebastien Brant Illkirch 67400 FRANCE Phone: (33) 3 90 24 45 92 EMail: noel@dpt-info.u-strasbg.fr URI: http://www-r2.u-strasbg.fr/~noel/ Chan-Wah Ng Panasonic Singapore Laboratories Pte Ltd Blk 1022 Tai Seng Ave #06-3530 Tai Seng Industrial Estate Singapore 534415 SG Phone: +65 65505420 EMail: cwng@psl.com.sg Montavont, et al. Expires January 17, 2005 [Page 11] Internet-Draft Analysis of Multihoming in Mobile IPv6 July 2004 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. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Montavont, et al. Expires January 17, 2005 [Page 12]