INTERNET DRAFT JinHyeock Choi Expires: May 2002 WooShik Kang Samsung AIT November 2001 Localized Mobility Management for Mobile IPv6 in Distributed Manner 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 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 obsolete by other documents at anytime. 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 This document presents Localized Mobility Management for Mobile IPv6 in Distributed Manner (LMMDv6). Localized Mobility Management, in general introduces Local Mobility Agent functionality for proxying a Regional care of address that remains the same while the mobile node moves within a Local Mobility Domain, which reduces the binding update signaling latency and the signaling load outside the Local Mobility Domain. We present a new way of forming Local Mobility Domains and Local Mobility Agents. In this protocol, Local Mobility Agent functionality is distributed across all access routers and a Local Mobility Domain is formed dynamically according to the mobile node's movement. Table of Contents: 1. Introduction 2. Terminology 3. Protocol Overview Choi, Kang Expires May 2002 [Page 1] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 3.1 Local Mobility Domain, Local Mobility Agent and Local Mobility Domain List 3.2 Operation Overview 4. Operation Description 4.1 Local Mobility Domain 4.2 Local Mobility Agent 4.3 Local Mobility Domain List 4.4 The first arrival at a foreign network 4.5 Movement to a new access router 4.5.1 Intra-Domain Movement 4.5.2 Inter-Domain Movement References 1. Introduction Localized Mobility Management for Mobile IPv6 in Distributed Manner (LMMDv6) introduces a new way of forming Local Mobility Domains and Local Mobility Agents. It defines local binding update signaling and local-aware data routing through a Local Mobility Agent. This protocol re-uses the general idea of [2] and [3] but is a different protocol regard to the formation of Local Mobility Domains and Local Mobility Agents. Instead of using predetermined Local Mobility Domains and Local Mobility Agents, each mobile node changes its current Local Mobility Domain and Local Mobility Agent dynamically according to its movement. This protocol only requires special treatment at the mobile nodes and access routers. Home agents are unchanged and this is completely transparent to corresponding nodes. The Local Mobility Agent is merely a local home agent that maps the mobile node's Regional COA to a Local COA. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Access Router (AR) An Access Network Router residing on the edge of an Access Network and offers IP connectivity to mobile nodes Current Access Router The Access Router currently offering the connectivity to the mobile node. Local Mobility Choi, Kang Expires May 2002 [Page 2] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 The movement of an IP device without requiring a change to its routable IP address seen by the corresponding node or Home Agent. Although its point of attachment may change during the move, the IP addresses used to reach the device (both its home and IP subnet routable IP address) do not change. Local Mobility Agent (LMA) A mobile node uses Local Mobility Agent as a local home agent while roaming within a Local Mobility Domain. The LMA proxy Regional COA, receives all packets on behalf of the mobile node and will encapsulate and forward them directly to its current address. Local Mobility Domain Within the Local Mobility Domain, the globally visible routable IP address assigned to a mobile node does not change. LMD(CR, N) The Local Mobility Domain with the center router CR and the threshold hop count N. It is the set of all routers with the hop counts from CR less than or equal to N. Localized Mobility Management A method of handling mobility locally, in order to restrict the signaling area, thus possibly reducing the amount of signaling. LMMDv6 The abbreviation of Localized Mobility Management for Mobile IPv6 in Distributed Manner For more detailed terminology, refer [7]. 3. Protocol Overview 3.1 Local Mobility Domain, Local Mobility Agent and Local Mobility Domain List In this protocol, a Local Mobility Domain is composed of all routers that are sufficiently close to a fixed center router. The distance is measured by the hop count between two routers. For convenience we denote a Local Mobility Domain as LMD(CR, N); CR represents the center router. N is the threshold hop count of a positive integer. A Local Mobility Domain LMD(CR, N) is the set of all routers with the hop count from CR less than equal to N. We use the center router CR as the Local Mobility Agent in the Local Choi, Kang Expires May 2002 [Page 3] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 Mobility Domain LMD(CR, N). A network administrator determines the threshold hop count N a priori. Each router produces the list of all routers with the hop count from itself less than equal to N. We assume that all routers can execute necessary computations with the information provided from routing protocols (OSPF, RIP). 3.2. Operation Overview A mobile node uses a Local Mobility Agent as a local home agent while roaming within a Local Mobility Domain. The mobile node uses two care of addresses: a Regional care of address on the Local Mobility Agent's subnet (Regional COA) and an on-link one on the subnet of the current access router (Local COA). The mobile node registers with its home agent with Regional COA and Home Address. If the mobile node changes its current address within a Local Mobility Domain, it only needs to register the new address with a Local Mobility Agent since the Regional COA doesn't change. This reduces the binding update signaling latency and the signaling load. LMMDv6 distributes the Local Mobility Agent functionality across all access routers. When a mobile node moves to a foreign network for the first time; - The first access router to which it is attached becomes the first Local Mobility Agent. - The first Local Mobility Domain is formed accordingly. (The set of all routers with the hop counts from the first AR less than equal to N). - The mobile node gets a Regional COA and a Local COA. - It registers with the home agent with the binding update that specifies binding (Regional COA and Home Address). Assume the mobile node move to a new access router. - If the new access router belongs to the current Local Mobility Domain (the hop count between the current Local Mobility Agent and the new access router is less than equal to N), the mobile node registers with the current Local Mobility Agent. - It sends the binding update to the current LMA specifying binding (the current Regional COA, the new Local COA). A Local Mobility Agent acts essentially as a local home agent for the mobile node. The Local Mobility Agent will receive all packets on behalf of the mobile node it is serving and will encapsulate and forward them directly to the mobile node's current address, Local COA. Choi, Kang Expires May 2002 [Page 4] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 When the mobile node moves outside of the current Local Mobility Domain (the hop count between the current Local Mobility Agent and the new access router is greater than N); - The mobile node behaves as if it arrives at a foreign network for the first time. - The new access router becomes a new Local Mobility Agent and a new Local Mobility Domain is formed accordingly (the set of all routers with the hop distance of N or less). 4. Operation Description 4.1. Local Mobility Domain ************* LMD(AR1, 2)*********** * * * _ _ _ _ _ _ _ _ _ * * | | | | | | * * | AR1 |---| AR2 |---| AR3 | * * |_ _ _| |_ _ _| |_ _ _| * * | | * * | *****|******** * _ _ _ * _ _ _ _ _ _ * | | * | | | | * | AR4 |-*-| AR5 |---| AR6 | * |_ _ _| * |_ _ _| |_ _ _| * * * * *********************** ********************** * * _ _ _ _ _ _ * _ _ _ * | | | | * | | * | AR1 |---| AR2 |-*-| AR3 | * |_ _ _| |_ _ _| * |_ _ _| * | * | * *******|***** | * * _ _ _ _ _ _ _ _ _ * * | | | | | | * * | AR4 |---| AR5 |---| AR6 | * * |_ _ _| |_ _ _| |_ _ _| * * * * * ********** LMD(AR6, 2)************ Figure1: Local Mobility Domains, LMD(AR1, 2) and LMD(AR6, 2) Choi, Kang Expires May 2002 [Page 5] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 In our scheme, Local Mobility Domains are configured dynamically. A network administrator only has to choose suitable threshold hop count. We define the distance between two nodes as the hop counts between two nodes. A Local Mobility Domain is determined by the center router CR and positive integer N. A Local Mobility Domain consists of all routers such that the distance from center router CR is less or equal to N. A Local Mobility Domain LMD(CR, N) is the set of all routers with the hop distance N or less. We can vary the size of a Local Mobility Domain by varying threshold hop count according to network circumstances. For example, a network administrator can set the threshold hop count to 5. Determining the size of a Local Mobility Domain (the threshold hop count) is left to the network administrator's discretion. After threshold hop count is fixed, a Local Mobility Domain is entirely determined by its center router. We can use a different distance metric other than hop count, e.g. weighted hop count. LMMDv6 works with any distance satisfying the symmetry property (The distance from A to B equals the distance from B to A.) 4.2. Local Mobility Agent In LMMDv6, the center router becomes the Local Mobility Agent in that Local Mobility Domain. In other words, CR is the Local Mobility Agent in LMD(CR, N). LMA acts as a local home agent for the MNs it serves in a Local Mobility Domain. Though there is only one LMA for each Local Mobility Domain, this doesn't mean single point of failure because there are many Local Mobility Domains. If the current LMA fails, the currently attached access router becomes the new LMA in a newly formed Local Mobility Domain. 4.3. Local Mobility Domain List Each LMMDv6-aware access router has its own Local Mobility Domain List. The Local Mobility Domain List is the list of all routers such that the hop count from that access router is less than equal to N. The Local Mobility Domain List of AR is the list of all routers belonging to the Local Mobility Domain LMD(AR, N). The Local Mobility Domain List varies according to the access router Choi, Kang Expires May 2002 [Page 6] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 producing it and each access router has a different Local Mobility Domain List. In following example, we present the Local Mobility Domain List of each access router in a network described in Figure 2 with threshold hop count 2. _ _ _ _ _ _ _ _ _ | | | | | | | AR1 |---| AR2 |---| AR3 | |_ _ _| |_ _ _| |_ _ _| | | | | _ _ _ _ _ _ _ _ _ | | | | | | | AR4 |---| AR5 |---| AR6 | |_ _ _| |_ _ _| |_ _ _| Access Router | AR1 | AR2 | AR3 | AR4 | AR5 | AR6 -------------------------------------------------- Local | AR1 | AR1 | AR1 | AR1 | AR2 | AR3 Mobility | AR2 | AR2 | AR2 | AR2 | AR3 | AR4 Domain | AR3 | AR3 | AR3 | AR3 | AR4 | AR5 List | AR4 | AR4 | AR4 | AR4 | AR5 | AR6 | | AR5 | AR5 | AR5 | AR6 | | | | AR6 | AR6 | Figure2: The Local Mobility Domain Lists with threshold hop count 2 We assume all access routers can compute the distance from the other router. The distance can be computed by using the information from routing protocol like OSPF, RIP. The detailed mechanism for this resolution is outside the scope of this draft. A Local Mobility Domain's boundaries are defined by Local Mobility Domain List. The Local Mobility Domain List of AR is the list of LMD(AR, N). If AR1 belongs to LMD(AR2, N), AR2 also belongs to LMD(AR1, N). Hence the Local Mobility Domain List of AR1 contains the list all access routers AR such that AR1 belongs LMD(AR, N). When a MN moves to a new access router, it can decide whether it still is within the same Local Mobility Domain by checking the Local Mobility Domain List of the new AR. - If the current LMA belongs to the new Local Mobility Domain List, the MN still remains at same Local Mobility Domain and current LMA continues Localized Mobility Management service. - If not, the new AR becomes the new LMA in the new Local Mobility Domain. Choi, Kang Expires May 2002 [Page 7] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 4.4. The first arrival at a foreign network Assume a MN arrives at a foreign network for the first time and is attached to an access router. First it checks whether the first AR is LMMDv6-aware. - If the first AR is not LMMDv6-aware, then the MN using the MIPv6 [1] protocol for its mobility management. - On the other hand, if the current AR is LMMDv6-aware, the MN MAY choose to use its LMMDv6 implementation. - This information is stored in the ARs and communicated to the MN via Router Advertisements. Then the first AR to which MN is currently attached becomes the first LMA. And the first Local Mobility Domain consists of all routers with hop count less than equal to N from the first AR. ************* LMD(AR1, 2)*********** * * * _ _ _ _ _ _ _ _ _ * * | | | | | | * * | AR1 |---| AR2 |---| AR3 | * * |_ _ _| |_ _ _| |_ _ _| * * + | | * * + | *****|******** * + _ _ _ * _ _ _ _ _ _ * _+_ | | * | | | | * | | | AR4 |-*-| AR5 |---| AR6 | * |MN | |_ _ _| * |_ _ _| |_ _ _| * |_ _| * * * *********************** Figure3: The first arrival at a foreign network with threshold hop count 2 Now in this new Local Mobility Domain, the MN needs to get two COAs - a Regional COA on the LMA's subnet (Regional COA) and an on-link one on the subnet of the current AR (Local COA). - These addresses MAY be formed in a stateless or stateful manner. - In this case, Regional COA and Local COA may be the same since the current AR is the current LMA. After forming the Regional COA and Local COA, the MN sends a BU to the LMA (the current AR). - The Local COA is used as the source address of the BU. - The BU specifies its Regional COA in the Home Address field. - This BU will bind the MN's Regional COA (similar to a Home Address) to its current Local COA. Choi, Kang Expires May 2002 [Page 8] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 The BU informs the LMA that the MN has formed a Regional COA (contained in the BU as a Home Address) and request that a LMA performs DAD on its behalf. - The LMA (acting as a home agent) will then perform DAD for the MN's Regional COA on its subnet. - If successful, the LMA will return a Binding Acknowledgement (BAck) to the MN indicating a successful registration. - Otherwise, the LMA MUST return a BAck with the appropriate fault code. No new error codes are introduced for LMMDv6. The MN MUST register its new Regional COA with its home agent. - It sends a BU that specifies the binding (Regional COA, Home Address) as in MIPv6. - The Home Address field of the BU is set to the Home Address. An COA is set to the Regional COA. It can also send a similar BU (i.e. that specifies the binding between the Home Address and the Regional COA) to its current CNs. Now the LMA acts as a local home agent with Home Address being the Regional COA and care of address being the new Local COA. The LMA acts as a proxy between the Regional COA and the Local COA. It intercepts all the packets addressed to the MN and tunneled them to the MN position (Local COA). 4.5. Movement to a new access router When the MN moves to another AR, it checks whether new AR is LMMDv6-aware in the same way as in 4.4. In case the new AR is LMMDv6-aware, The MN checks whether it still remains within the current Local Mobility Domain. It sees whether the Local Mobility Domain List of the new AR contains the current LMA. There are two ways for this. - The new AR sends its Local Mobility Domain List in router advertisement with option like MAP Option of [2]. - If there are many entiries in the Local Mobility Domain List of the new AR, advertising overhead may be too costly. In that case MN sends its current LMA address in router solicitation with option like Home Address Option of [1]. Then a new AR checks its Local Mobility Domain List and sends a reply. 4.5.1 Intra-Domain Movement If the current LMA belongs to the Local Mobility Domain List of the new AR, it means the MN is still within the current Local Mobility Domain. Choi, Kang Expires May 2002 [Page 9] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 Since MN has moved to the new AR, it gets a new Local COA on the new AR's subnet. This new Local COA MAY be formed in a stateless or stateful manner. Since the MN moves within the same Local Mobility Domain (i.e. its LMA does not change), the Regional COA stays unchanged. ************* LMD(AR1, 2)*********** * * * _ _ _ _ _ _ _ _ _ * * | | | | | | * * | AR1 |---| AR2 |---| AR3 | * * |_ _ _| |_ _ _| |_ _ _| * * | | * * | *****|******** * _ _ _ * _ _ _ _ _ _ * | | * | | | | * | AR4 |-*-| AR5 |---| AR6 | * |_ _ _| * |_ _ _| |_ _ _| * + * * + * **************** + **** _+_ | | |MN | |_ _| Figure4: Intra-Domain movement When the MN moves within the same Local Mobility Domain (i.e. its LMA does not change), it MUST only register its new Local COA with its LMA. - The MN registers with the LMA by sending a BU containing its Regional COA and on-link address (Local COA). - The Local COA is used as the source address of the BU and the Regional COA is specified in the Home Address field. - The LMA MUST store this information in its binding cache to be able to forward packets to their final destination when received from the different CNs or home agents. The Binding Update signaling latency is reduced by localizing binding updates to the Local Mobility Domain and the signaling load is reduced by using LMA for a proxy care of address, as seen by hosts outside the Local Mobility Domain. When a CN sends data packets to a MN to which it does not yet have an entry in its binding cache, these packets are intercepted by the home agent and encapsulated to the registered care of address, as specified in the basic Mobile IPv6. But this care of address is the Regional COA. Choi, Kang Expires May 2002 [Page 10] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 The LMA will receive packets addressed to the MN's Regional COA (from the home agent or CNs). Packets will be tunneled from the LMA to the MN's Local COA. The MN will decapsulate the packets and process the packet in the normal manner. The added routing state maintenance in the visited domain is minimal. It does not involve the routing tables at all; all per- mobile state is kept in the Local binding cache. This data structure is internal to the LMA and can re-use the existing binding cache. 4.5.2 Inter-Domain Movement If the current LMA is not included in the new Local Mobility Domain List, it means the MN has moved outside of the current Local Mobility Domain. ********************** * * _ _ _ _ _ _ * _ _ _ * | | | | * | | * | AR1 |---| AR2 |-*-| AR3 | * |_ _ _| |_ _ _| * |_ _ _| * | * | * *******|***** | * * _ _ _ _ _ _ _ _ _ * * | | | | | | * * | AR4 |---| AR5 |---| AR6 | * * |_ _ _| |_ _ _| |_ _ _| * * + * * + * ********** LMD(AR6, 2)**** + ***** _+_ | | |MN | |_ _| Figure5: Inter-Domain movement In that case, the MN behaves in the similar way as 4.4. - The current AR becomes the new LMA and new Local Mobility Domain is formed accordingly. - After Local Registration and Home Registration, the new LMA acts as a local home agent for the MN. Notice Regarding Intellectual property rights Choi, Kang Expires May 2002 [Page 11] INTERNET DRAFT LMM for MIPv6 in Distributed Manner November 2001 Samsung Electronics is pending patent applications that may be relevant to this Internet-Draft. If this specification is adopted by IETF and any claim of this patent is necessary for practicing this standard, any party will be able to obtain a license from Samsung Electronics to use any such patent claims under openly specified, reasonable, non-discriminatory terms to implement and fully comply with the standard. References [1] D. Johnson and C. Perkins, Mobility Support in IPv6, draft-ietf- mobileip-ipv6-14.txt, July 2000 [2] H. Soliman, C. Castelluccia, Karim El-Malki, L. Ludovic Bellier, Hierarchical MIPv6 mobility management, draft-ietf-mobileip- hmipv6-03.txt, February 2001 [3] E. Gustafsson, A. Jonsson, C. Perkins, Mobile IP Regional Registration, draft-ietf-mobileip- reg-tunnel-04.txt, March 2001 [4] C. Williams, Localized Mobility Management Requirements, draft- williams-mobileip-lmm- requirements-00.txt, July 2001 [5] H. Li, Local Mobility Management Framework, draft-li-mobileip-lmm- framework-00.txt, July 2001 [6] G. Tsirtsis, A. Yegin, C. Perkins, G. Dommety, K. El-Malki, M. Khalil, Fast Handovers for Mobile IPv6, draft-ietf-mobileip-fast- mipv6-01.txt, April 2001 [7] J. Manner, M. Kojo, C. Perkins, T. Suihko, P. Eardley, D. Wisely, R. Hancock, N. Georganopoulos,Mobility Related Terminology, draft- manner-seamoby-terms-02.txt, July 2001 Author's Addresses JinHyeock Choi i-Networking Lab, Samsung AIT (SAIT) Phone: +82-31-280-8194 Email: athene@sait.samgung.co.kr WooShik Kang i-Networking Lab, Samsung AIT (SAIT) Phone: +82-31-280-8190 Email: wskang@samsung.com Choi, Kang Expires May 2002 [Page 12]