Internet Draft J. Kempf, Editor Document: draft-ietf-netlmm-nohost-ps-03.txt Expires: December, 2006 June, 2006 Problem Statement for Network-based IP Local Mobility (draft-ietf-netlmm-nohost-ps-03.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/1id-abstracts.html. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract Localized mobility management is a well understood concept in the IETF with a number of solutions already available. This document looks at the principal shortcomings of the existing solutions, all of which involve the host in mobility management, and makes a case for network-based local mobility management. Contributors Gerardo Giaretta, Kent Leung, Katsutoshi Nishida, Phil Roberts, and Marco Liebsch all contributed major effort to this document. Their names are not included in the authors' section due to the RFC Editor's limit of 5 names. Table of Contents 1.0 Introduction.............................................2 2.0 The Local Mobility Problem...............................4 3.0 Scenarios for Localized Mobility Management..............6 4.0 Problems with Existing Solutions.........................7 J. Kempf, editor Expires December, 2006 [Page 1]
Internet Draft NETLMM Problem Statement June, 2006 5.0 IANA Considerations......................................8 6.0 Security Considerations..................................8 7.0 References...............................................9 8.0 Acknowledgements.........................................9 9.0 Author's Addresses.......................................9 10.0 IPR Statements..........................................10 11.0 Disclaimer of Validity..................................11 12.0 Copyright Notice........................................11 1.0 Introduction Localized mobility management has been the topic of much work in the IETF. The experimental protocols developed from previous work, namely FMIPv6 [1] and HMIPv6 [2], involve host-based solutions that require host involvement at the IP layer similar to or in addition to that required 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 nodes may support a more diverse set of global mobility protocols. While it is possible that existing localized mobility management protocols could be used with HIP and Mobike, some would require additional effort to implement and deploy in a non-Mobile IPv6 mobile environment. Secondly, the success in the WLAN infrastructure market of WLAN switches, which perform localized management without any host stack involvement, suggests a possible paradigm that could be used to accommodate other global mobility options on the mobile node while reducing host stack software complexity expanding the range of mobile nodes that could be accommodated. This document briefly describes the general local mobility problem and scenarios where localized mobility management would be desirable. Then problems with existing or proposed IETF localized mobility management protocols are briefly discussed. The network- based mobility management architecture and a short description of how it solves these problems is presented. A more detailed discussion of goals for a network-based, localized mobility management protocol and gap analysis for existing protocols can be found in [6]. Note that IPv6 and wireless links are considered to be the primary focal points for a network-based localized mobility management, so the language in this document reflects that focus. However, the conclusions of this document apply equally to IPv4 and wired links where nodes are disconnecting and reconnecting. 1.1 Terminology J. Kempf, editor Expires December, 2006 [Page 2]
Internet Draft NETLMM Problem Statement June, 2006 Mobility terminology in this draft follows that in RFC 3753 [7], with the addition of some new and revised terminology given here: Local Mobility (revised) Local Mobility is mobility over an access network. Note that, although the area of network topology over which the mobile node moves may be restricted, the actual geographic area 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 any IP protocol that maintains the IP connectivity and reachability of a mobile node for purposes of maintaining session continuitity when the mobile node moves, and whose signaling is confined to an access network. Localized Mobility Management Protocol A protocol that supports localized mobility management. Global Mobility Management Protocol A Global Mobility Management Protocol is a mobility protocol used by the mobile node to change the global, end-to-end routing of packets for purposes of maintaining session continuity when movement causes a topology change and thus invalidates a global unicast address of the mobile node. This protocol could be Mobile IP [1][13] but it could also be HIP [4] or Mobike [5]. Global Mobility Anchor Point A node in the network where the mobile node maintains a permanent address and a mapping between the permanent address and the local temporary address where the mobile node happens to be currently located. The Global Mobility Anchor Point may be used for purposes of rendezvous and possibly traffic forwarding. Intra-Link Mobility Intra-Link Mobility is mobility between wireless access points within a link. Typically, this kind of mobility only involves Layer 2 mechanisms, so Intra-Link Mobility is often called Layer 2 mobility. No IP subnet 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 the previous access routers becoming unreachable. If the link is served by a single access J. Kempf, editor Expires December, 2006 [Page 3]
Internet Draft NETLMM Problem Statement June, 2006 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 an access network. The access network gateways function as aggregation routers. In this case, there is no specialized routing protocol (e.g. GTP, Cellular IP, Hawaii, etc.) and the routers form a standard IP routed network (e.g. OSPF, IS-IS, RIP, etc.). This is illustrated in Figure 1, where the access network gateway routers are designated as "ANG". 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 Access Network Gateways (ANGs) GA1 and GB1 are gateways to their access networks. The Access Routers (ARs) RA1 and RA2 are in access network A, RB1 is in access network B. Note that it is possible to have additional aggregation routers between ANG GA1 and ANG GB1 and the access routers if the access network is large. Access Points (APs) PA1 through PA3 are in access network A, PB1 and PB2 are in access network B. Other ANGs, ARs, and APs are also possible, and other routers can separate the ARs from the ANGs. The figure implies a star topology for the access network 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 ARs are directly connected through some part of the network. As shown in the figure, a global mobility protocol may be necessary when a mobile node (MN) moves between two access networks. Exactly what the scope of the access networks is depends on deployment considerations. Mobility between two APs under the same AR constitutes intra-link, or Layer 2, mobility, and is typically handled by Layer 2 mobility protocols (if there is only one AP/cell per AR, then intra-link mobility may be lacking). Between these two lies local mobility. Local mobility occurs when a mobile node moves between two APs connected to two different ARs. Global mobility protocols allow a mobile node to maintain reachability when the MN's globally routable IP address changes. It does this by updating the address mapping between the permanent address and temporary local address at the global mobility anchor point, or even end to end by changing the temporary local address directly at the node with which the mobile node is corresponding. A global mobility management protocol can therefore be used between ARs for handling local mobility. However, there are three well- known problems involved in using a global mobility protocol for every movement between ARs. Briefly, they are: J. Kempf, editor Expires December, 2006 [Page 4]
Internet Draft NETLMM Problem Statement June, 2006 Access Network A Access Network B +-------+ +-------+ |ANG GA1| (other ANGs) |ANG GB1| (other ANGs) +-------+ +-------+ @ @ @ @ @ @ @ @ @ (other routers) @ @ @ @ @ @ @ @ @ +------+ +------+ +------+ |AR RA1| |AR RA2|(other ARs) |AR RB1| (other ARs) +------+ +------+ +------+ * * * * * * * * * * * * * * * * * * * * * * * * * * (other APs) * * (other APs) /\ /\ /\ /\ /\ /AP\ /AP\ /AP\ /AP\ /AP\ /PA1 \ /PA2 \ /PA3 \ /PB1 \ /PB2 \ ------ ------ ------ ------ ------ +--+ +--+ +--+ +--+ |MN|----->|MN|----->|MN|-------->|MN| +--+ +--+ +--+ +--+ Intra-link Local Global (Layer 2) Mobility Mobility Mobility Figure 1. Scope of Local and Global Mobility Management 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 this time, packets continue to be routed to the old temporary local address and are essentially dropped. 2) Signaling overhead. The amount of signaling required when a mobile node moves from one last hop 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 permanent to temporary local address mapping. The signaling volume may negatively impact wireless bandwidth usage and real time service performance. 3) Location privacy. The change in temporary local 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 J. Kempf, editor Expires December, 2006 [Page 5]
Internet Draft NETLMM Problem Statement June, 2006 expose the mobile node's user to threats on their location privacy. A more detailed discussion of location privacy for Mobile IPv6 can be found in [12]. 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 movement to a new link. In addition to these problems, localized mobility management can provide a measure of local control, so mobility management can be tuned for specialized local conditions. 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 restricted IP access network 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 useful. 3.1 Large Campus One scenario where localized mobility management would be attractive is a large campus wireless LAN deployment. Having a single broadcast domain for all WLAN access points doesn't scale very well. Also, sometimes parts of the campus cannot be covered by one VLAN for other reasons (e.g., some links are other than 802.3). In this case, the campus is divided into separate last hop 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] have the potential to run IP deeper 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 UltraWide Band (UWB) [10] and Bluetooth [11]. 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 J. Kempf, editor Expires December, 2006 [Page 6]
Internet Draft NETLMM Problem Statement June, 2006 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 goals for a network-based localized mobility management protocol. 3.3 Picocellular Network with Small But Node-Dense Last Hop 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 transmit power, short range operation. For such protocols, extremely small picocells become more practical. Although picocells do not necessarily imply "pico subnets", wireless sensors and other advanced applications may end up making such picocellular type networks node-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 link movement. 4.0 Problems with Existing Solutions Existing solutions for localized mobility management fall into three classes: 1) Interoperable IP level protocols that require changes to the mobile node's IP stack and handle localized mobility management as a service provided to the mobile node by the access network, 2) Link specific or proprietary protocols that handle localized mobility for any mobile node but only for a specific type of link layer, namely 802.11 running on an 802.3 wired network backhaul. The dedicated localized mobility management IETF protocols for Solution 1 are not yet widely deployed, but work continues on standardization. Some Mobile IPv4 deployments use localized mobility management. For Solution 1, the following are specific problems: 1) The host stack 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 stack software modifications. This preference is independent of the lack of widespread Mobile IPv4 deployment, since it is much easier to deploy and use the network. 2) Future mobile nodes 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) Existing host-based localized mobility management solutions require setting up additional security associations with network elements in the access domain. J. Kempf, editor Expires December, 2006 [Page 7]
Internet Draft NETLMM Problem Statement June, 2006 Market acceptance of WLAN switches has been very large, so Solution 2 is widely deployed and continuing to grow. 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 stack involvement for localized mobility management is a highly desirable solution. Mobility routing anchor points within the backbone network maintain a collection of routes for individual mobile nodes. The routes point to the ARs on which mobile nodes currently are located. Packets for the mobile node are routed to and from the mobile node through the mobility anchor point. When a mobile node moves from one AR to another, the ARs send a route update to the mobility anchor point. While some mobile node involvement is necessary and expected for generic mobility functions such as movement detection and to inform the AR about mobile node movement, no specific mobile node to network protocol will be required for localized mobility management itself. The advantages that this solution has over the Solutions 1 and 2 above are as follows: 1) Compared with Solution 1, a network-based solution requires no localized mobility management support on the mobile node and is independent of global mobility management protocol, so it can be used with any or none of the existing global mobility management protocols. The result is a more modular mobility management architecture that better accommodates changing technology and market requirements. 2) Compared with Solution 2, an IP level network-based localized mobility management solution works for link protocols other than Ethernet, and for wide area networks. 5.0 IANA Considerations There are no IANA considerations in this document. 6.0 Security Considerations Localized mobility management has certain security considerations, one of which - need for access network to mobile node security - was touched on in this document. Host-based localized mobility management protocols have all the security problems involved with providing a service to a host. Network-based localized mobility J. Kempf, editor Expires December, 2006 [Page 8]
Internet Draft NETLMM Problem Statement June, 2006 management requires security among network elements equivalent to what is needed for routing information security, and security between the host and network equivalent to what is needed for network access, but no more. A more complete discussion of the security goals for network-based localized mobility management can be found in [6]. 7.0 References 7.1 Informative References [1] Koodli, R., editor, "Fast Handovers for Mobile IPv6," RFC 4068, July, 2005. [2] Soliman, H., editor, "Hierarchical Mobile IPv6 Mobility Management," RFC 4140, August, 2005. [3] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in IPv6," RFC 3775. [4] Moskowitz, R., and Nikander, P., "Host Identity Protocol (HIP) Architecture", RFC 4423, May, 2006. [5] Eronen, P., editor, "IKEv2 Mobility and Multihoming Protocol (MOBIKE)", Internet Draft, work in progress. [6] Kempf, J., editor, "Goals for Network-based 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] 3GPP, "3GPP System Architecture Evolution: Report on Technical Options and Conclusions", TR 23.882, 2005, http://www.3gpp.org/ftp/Specs/html-info/23882.htm. [10] http://www.ieee802.org/15/pub/TG3a.htm [11] Bluetooth SIG, "Specification of the Bluetooth System", November, 2004, available at http://www.bluetooth.com. [12] Koodli, R., "IP Address Location Privacy and Mobile IPv6: Problem Statement", Internet Draft, work in progress. [13] Perkins, C., editor, " IP Mobility Support for IPv4", RFC 3220, August, 2002. 8.0 Acknowledgements The authors would like to acknowledge the following for particularly diligent reviewing: Vijay Devarapalli, Peter McCann, Gabriel Montenegro, Vidya Narayanan, Pekka Savola, and Fred Templin. 9.0 Author's Addresses James Kempf DoCoMo USA Labs 181 Metro Drive, Suite 300 J. Kempf, editor Expires December, 2006 [Page 9]
Internet Draft NETLMM Problem Statement June, 2006 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 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 10.0 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. J. Kempf, editor Expires December, 2006 [Page 10]
Internet Draft NETLMM Problem Statement June, 2006 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. 11.0 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. 12.0 Copyright Notice Copyright (C) The Internet Society (2006). 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. J. Kempf, editor Expires December, 2006 [Page 11]
