J. Kempf Internet Draft K. Leung Document: draft-kempf-netlmm-nohost-ps-00.txt P. Roberts K. Nishida G. Giaretta M. Liebsch Expires: December, 2005 June, 2005 Problem Statement for IP Local Mobility (draft-kempf-netlmm-nohost-ps-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. Abstract In this document, the well-known problem of localized mobility management for IP link handover is given a fresh look. After a short discussion of the problem and a couple of scenarios, the principal shortcomings of existing solutions are discussed. Table of Contents 1.0 Introduction................................................2 2.0 The Local Mobility Problem..................................3 3.0 Scenarios for Localized Mobility Management.................6 4.0 Most Serious Problems with Existing Solutions...............7 5.0 Security Considerations.....................................8 6.0 Author Information..........................................8 7.0 Informative References......................................9 8.0 IPR Statements.............................................10 9.0 Disclaimer of Validity.....................................10 10.0 Copyright Notice..........................................10 Kempf, et. al. Expires December, 2005 [Page 1]
Internet Draft Problem Statement for IP Local Mobility June, 2005 1.0 Introduction Localized mobility management has been the topic of much work in the IETF for some time, and it may seem as if little remains to be said on the topic. The experimental protocols developed from previous work, namely FMIPv6 [1] and HMIPv6[2], involve host-based solutions that mimic to a greater or lesser extent the approach taken by Mobile IPv6 [3] for global mobility management. However, recent developments in the IETF and the WLAN infrastructure market suggest that it may be time to take a fresh look at localized mobility management. Firstly, new IETF work on global mobility management protocols that are not Mobile IPv6, such as HIP [4] and Mobike [5], suggests that future wireless IP hosts may support a more diverse set of global mobility protocols. Secondly, the success in the WLAN infrastructure market of WLAN switches, which perform localized mobility management without any host involvement, suggests a possible design paradigm that could be used to accommodate other global mobility management options on the host while reducing host software complexity and expanding the range of hosts that could be accommodated. This document briefly describes the local mobility problem and a few scenarios where localized mobility management would be desirable. Then, it describes the two most serious problems with existing protocols: the requirement for host support, and the complex security interactions required between the host and the network. More detailed requirements and gap analysis for existing protocols can be found in [6]. 1.1 Terminology Mobility terminology in this draft follows that in RFC 3753[7], some of which are included here: IP Link A set of routers, mobile nodes, and wireless access points that share link broadcast capability or its functional equivalent. This definition covers one or multiple access points under one or several access routers. In the past, such a set has been called a subnet, but this term is not strictly correct for IPv6, since multiple subnet prefixes can be assigned to an IP link in IPv6. Local Mobility Local Mobility is mobility over a restricted area of the network topology. Note that, although the area of network topology over which the mobile node moves may be restricted, the actual geographic area, though not unlimited, could be quite large, depending on the mapping between the network topology and the wireless coverage area. Localized Mobility Management Localized Mobility Management is a generic term for protocols dealing with IP mobility management confined within a restricted, topologically localized portion of the network. Localized mobility management signaling is not routed outside a locally restricted part of the network, although a handover may trigger Global Mobility Management signaling. Localized mobility management protocols exploit the locality Kempf, et. al. Expires December 2005 [Page 2]
Internet Draft Problem Statement for IP Local Mobility June, 2005 of movement by confining movement related changes to a topologically restricted part of the network when movement is restricted geographically. Localized Mobility Management Domain A Localized Mobility Management Domain consists of the following three components: wireless or other access points, access routers, localized mobility management domain gateways which form the boundary to other networks and may shield other networks from the specialized routing protocols (if any) run in the Localized Mobility Management Domain; and (optionally) other internal routers which may also be needed in some cases to support a specialized routing protocol. Global Mobility Protocol A Global Mobility Protocol is a mobility protocol used by the mobile node to change the global, end-to-end routing of packets when movement causes a topology change and thus invalidates a global unicast address on the local IP link currently in active use by the mobile node. The Global Mobility Protocol allows the mobile node to maintain a mapping between a permanent rendezvous or home address and a temporary care-of address for rendezvous with nodes that want to initiate a connection, and it may also provide direct routing through the rendezvous node and/or optimized routing directly between correspondent nodes and the local address. Typically, this protocol will be Mobile IPv6 [1] but it could also be HIP [4] or Mobike [5] (note: although Mobike is not considered a mobility management protocol in general, for purposes of this document, it will be so considered because it manages the address map and routing between a fixed VPN endpoint address and a changing local address). Global Mobility Anchor Point A node in the network where the mobile node has its fixed home address that maintains the mapping between the home address and care-of address for purposes of rendezvous and possibly traffic forwarding. For Mobile IPv6 [1], this is the home agent. For HIP [4], this is the rendezvous server. For Mobike [5], this is the VPN tunnel gateway in the home network. Intra-Link Mobility Intra-Link Mobility is mobility between wireless access points within an IP Link. Typically, this kind of mobility only involves Layer 2 mechanisms, so Intra-Link Mobility is often called Layer 2 mobility. No IP link configuration is required upon movement since the link does not change, but some IP signaling may be required for the mobile node to confirm whether or not the change of wireless access point also resulted in a change of IP link. If the IP link consists of a single access point/router combination, then this type of mobility is typically absent. See Figure 1. 2.0 The Local Mobility Problem The local mobility problem is restricted to providing IP mobility management for mobile nodes within a localized mobility management domain. Localized mobility management domain consists of a group of access routers connected Kempf, et. al. Expires December 2005 [Page 3]
Internet Draft Problem Statement for IP Local Mobility June, 2005 to wired or wireless access points on the downlink side and a wired IP core through one or more aggregation routers on the side that is routed toward the border router and the Internet. The aggregation routers function as a localized mobility management domain gateway, although in this case, there is no specialized routing protocol and the routers function as a standard IP routed network. This is illustrated in Figure 1, where the aggregation routers are designated as "AggR". Transitions between service providers in separate autonomous systems or across broader topological "boundaries" within the same service provider are excluded. Figure 1 depicts the scope of local mobility in comparison to global mobility. The Aggregation Routers AggR A1 and B1 are gateways to the localized mobility management domain. The Access Routers AR A1 and A2 are in Localized Mobility Management Domain A, B1 is in Localized Mobility Management Domain B. Note that it is possible to have additional aggregation routers between AggR A1 and AggR B1 and the access routers if the domain is large. Access Points AP A1 through A3 are in Localized Mobility Management Domain A, B1 and B2 are in Localized Mobility Management Domain B. Other Aggregation Routers, Access Routers, and Access Points are also possible. The figure implies a star topology for the localized mobility management domain deployment, and the star topology is the primary one of interest since it is quite common, but the problems discussed here are equally relevant to ring or mesh topologies in which access routers are directly connected through some part of the network. Kempf, et. al. Expires December 2005 [Page 4]
Internet Draft Problem Statement for IP Local Mobility June, 2005 Localized Mobility Localized Mobility Management Domain A Management Domain B +-------+ +-------+ |AggR A1| (other AggRs) |AggR B1| (other AggRs) +-------+ +-------+ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ +-----+ +-----+ +-----+ |AR A1| |AR A2|(other ARs) |AR B1| (other ARs) +-----+ +-----+ +-----+ * * * * * * * * * * * * * * * * * * * * * * * * * * (other APs) * * (other APs) /\ /\ /\ /\ /\ /AP\ /AP\ /AP\ /AP\ /AP\ / A1 \ / A2 \ / A3 \ / B1 \ / B2 \ ------ ------ ------ ------ ------ +--+ +--+ +--+ +--+ |MN|----->|MN|----->|MN|-------->|MN| +--+ +--+ +--+ +--+ Intra-link Local Global Mobility Mobility Mobility Figure 1. Scope of Local and Global Mobility Management As shown in the figure, a global mobility protocol is necessary when a mobile node (MN) moves between two localized mobility management domains. Exactly what the scope of the localized mobility management domains is depends on deployment considerations. Mobility between two access points under the same access router and within the same IP link (e.g. within the same VLAN) constitutes Intra-link mobility, and is typically handled by Layer 2 mobility protocols. If there is only one access point/cell per access router, then intra-link mobility may be lacking. Between these two lies local mobility. Local mobility occurs when a mobile node moves between two access points connected to two different access routers in the same localized mobility management domain. Global mobility protocols allow a mobile node to maintain reachability when a change between access routers occurs, by updating the address mapping between the home address and care-of address at the global mobility anchor point, or even end to end by changing the care-of address directly at the correspondent node. A global mobility management protocol can therefore be used between access routers for handling local mobility. However, there are Kempf, et. al. Expires December 2005 [Page 5]
Internet Draft Problem Statement for IP Local Mobility June, 2005 three well-known problems involved in using a global mobility protocols for every transition between access routers. Briefly, they are: 1) Update latency. If the global mobility anchor point and/or correspondent node (for route optimized traffic) is at some distance from the mobile node's access network, the global mobility update may require a considerable amount of time, during which time packets continue to be routed to the old care-of address and are essentially dropped. 2) Signaling overhead. The amount of signaling required when a mobile node moves from one IP link to another can be quite extensive, including all the signaling required to configure an IP address on the new link and global mobility protocol signaling back into the network for changing the home to care-of address mapping. The signaling volume may negatively impact wireless bandwidth usage and real time service performance. 3) Location privacy. The change in care-of address as the mobile node moves exposes the mobile node's topological location to correspondents and potentially to eavesdroppers. An attacker that can assemble a mapping between subnet prefixes in the mobile node's access network and geographical locations can determine exactly where the mobile node is located. This can expose the mobile node's user to threats on their location privacy. These problems suggest that a protocol to localize the management of topologically small movements is preferable to using a global mobility management protocol on each IP link move. Note also that if localized mobility management is provided, it is not strictly required for a mobile node to support a global mobility management protocol since movement within a localized mobility management domain can still be accommodated. Without such support, however, a mobile node experiences a disruption in its traffic when it moves beyond the border of the localized mobility management domain. 3.0 Scenarios for Localized Mobility Management There are a variety of scenarios in which localized mobility management is attractive. 3.1 Large Campus with Diverse Physical Interconnectivity One scenario where localized mobility management would be attractive is for a campus wireless LAN deployment in which parts of the campus are connected by links that are other than 802.3 or in which it is not possible to cover the campus by one VLAN. In this case, the campus is divided into separate IP links each served by one or more access routers. This kind of deployment is served today by wireless LAN switches that co-ordinate IP mobility between them, effectively providing localized mobility management at the link layer. Since the protocols are proprietary and not interoperable, any deployments that require IP mobility necessarily require switches from the same vendor. 3.2 Advanced Cellular Network Next generation cellular protocols such as 802.16e [8] and Super 3G/3.9G [9] with all IP network architecture [10] have the potential to run IP deeper Kempf, et. al. Expires December 2005 [Page 6]
Internet Draft Problem Statement for IP Local Mobility June, 2005 into the access network than the current 3G cellular protocols, similar to today's WLAN networks. This means that the access network can become a routed IP network. Interoperable localized mobility management can unify local mobility across a diverse set of wireless protocols all served by IP, including advanced cellular, WLAN, and personal area wireless technologies such as UWB and Bluetooth. Localized mobility management at the IP layer does not replace Layer 2 mobility (where available) but rather complements it. A standardized, interoperable localized mobility management protocol for IP can remove the dependence on IP layer localized mobility protocols that are specialized to specific link technologies or proprietary, which is the situation with today's 3G protocols. The expected benefit is a reduction in maintenance cost and deployment complexity. See [6] for a more detailed discussion of the requirements for localized mobility management. 3.3 Picocellular Network with Small But Host-Dense IP Links Future radio link protocols at very high frequencies may be constrained to very short, line of sight operation. Even some existing protocols, such as UWB and Bluetooth, are designed for low power, short range operation. For such protocols, extremely small picocells become more practical. Although picocells do not necessarily imply "pico IP links", wireless sensors and other advanced host applications may end up making such picocellular type networks host-dense, requiring subnets that cover small geographical areas, such as a single room. The ability to aggregate many subnets under a localized mobility management scheme can help reduce the amount of IP signaling required on IP link movement, both over the air and through the access network. 4.0 Problems with Existing Solutions Existing solutions for localized mobility management fall into two classes: 1) Interoperable IP level protocols that require changes to the host's IP stack and handle localized mobility management as a service provided to the host by the localized mobility management domain, 2) Proprietary protocols that handle localized mobility for any host but only for a specific type of link layer, namely 802.11 running on an 802.3 wired network backhaul. For Solution 1), the following are specific problems: 1) The host software requirement limits broad usage even if the modifications are small. The success of WLAN switches indicates that network operators and users prefer no host software modifications. This preference is likely to be independent of the lack of widespread Mobile IPv4 deployment, since it is much easier to deploy and use the network. 2) Future hosts may choose other global mobility management protocols, such as HIP or Mobike. The existing localized mobility management solutions all depend on Mobile IP or derivatives. 3) Existing localized mobility management solutions do not support both IPv4 and IPv6. 4) Security for the existing localized mobility management solutions requires complex security associations with network elements for no improvement in security over what is available if localized mobility Kempf, et. al. Expires December 2005 [Page 7]
Internet Draft Problem Statement for IP Local Mobility June, 2005 management is not used. In addition to the additional signaling required to set up these security associations, provisioning a mobile node with credentials for roaming to all the localized mobility management domains where the mobile node might end up may prove difficult, acting as a possible barrier to deployment. Solution 2 has the following problems: 1) Existing solutions only support WLAN networks with Ethernet backhaul and therefore are not available for advanced cellular networks or picocellular protocols, or other types of wired backhaul. 2) Each WLAN switch vendor has its own proprietary protocol that does not interoperate with other vendor's equipment. 3) Because the solutions are based on layer 2 routing, they may not scale up to a metropolitan area, or local province. Having an interoperable, standardized localized mobility management protocol that is scalable to topologically large networks, but requires no host involvement is a highly desirable solution. 5.0 Security Considerations Localized mobility management has certain security considerations, one of which - need for localized mobility management domain to host security - was touched on in this document. Existing localized mobility management solutions increase the need for host to localized mobility management domain signaling and provisioning of the mobile node with credentials without increasing the security beyond what is available if no localized mobility management solution is used. A more complete discussion of the security requirements for localized mobility management can be found in [6]. 6.0 Acknowledgements The authors would like to thank Youngjune Gwon, DoCoMo Labs USA, for writing the first draft of this document. 7.0 Author Information James Kempf DoCoMo USA Labs 181 Metro Drive, Suite 300 San Jose, CA 95110 USA Phone: +1 408 451 4711 Email: kempf@docomolabs-usa.com Kent Leung Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA EMail: kleung@cisco.com Phil Roberts Kempf, et. al. Expires December 2005 [Page 8]
Internet Draft Problem Statement for IP Local Mobility June, 2005 Motorola Labs Schaumberg, IL USA Email: phil.roberts@motorola.com Katsutoshi Nishida NTT DoCoMo Inc. 3-5 Hikarino-oka, Yokosuka-shi Kanagawa, Japan Phone: +81 46 840 3545 Email: nishidak@nttdocomo.co.jp Gerardo Giaretta Telecom Italia Lab via G. Reiss Romoli, 274 10148 Torino Italy Phone: +39 011 2286904 Email: gerardo.giaretta@tilab.com Marco Liebsch NEC Network Laboratories Kurfuersten-Anlage 36 69115 Heidelberg Germany Phone: +49 6221-90511-46 Email: marco.liebsch@ccrle.nec.de 8.0 Informative References [1] Koodli, R., editor, "Fast Handovers for Mobile IPv6," Internet Draft, a work in progress. [2] Soliman, H., editor, "Hierarchical Mobile IPv6 Mobility Management," Internet Draft, a work in progress. [3] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in IPv6," RFC 3775. [4] Moskowitz, R., Nikander, P., Jokela, P., and Henderson, T., "Host Identity Protocol", Internet Draft, work in progress. [5] Kivinen, T., and Tschopfening, H., "Design of the MOBIKE Protocol", Internet Draft, work in progress. [6] Kempf, J., Leung, K., Roberts, P., Giaretta, G., Liebsch, M., Nishita, K., and Gwon, Y., "Requirements and Gap Analysis for Localized Mobility Management", Internet Draft, work in progress. [7] Manner, J., and Kojo, M., "Mobility Related Terminology", RFC 3753, June, 2004. [8] IEEE, "Air Interface for Mobile Broadband Wireless Access Systems", 802.16e, 2005. [9] "DoCoMo's Proposals for 3G Long Term Evolution - Technologies for Super 3G", TSG-RAN Future Evolution Workshop, Toronto, Canada, 2-3 November, 2004. Kempf, et. al. Expires December 2005 [Page 9]
Internet Draft Problem Statement for IP Local Mobility June, 2005 [10] 3GPP, "All-IP Network (AIPN) Feasibility Study", Chris Sancho, ed., 3GPP TR 22.978, 2005. 9.0 IPR Statements 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. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 10.0 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. 11.0 Copyright Notice 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. Kempf, et. al. Expires December 2005 [Page 10]