An adaptive mobility anchor point selection scheme in Hierarchical Mobile IPv6 networks Sangheon Pack, Minji Nam, Taekyoung Kwon * , Yanghee Choi Seoul National University, Shilim-dong, Kwanak-gu, Seoul 301-518, Republic of Korea Available online 18 January 2006 Abstract In Hierarchical Mobile IPv6 (HMIPv6) networks, the mobility anchor point (MAP) is introduced to localize binding update messages destined to the home agent. In a large-scale wireless/mobile network, multiple MAPs may be deployed in order to provide more scalable and robust mobile services. In this case, it is important for a mobile node (MN) to select the most appropriate MAP among them. In this paper, we propose an adaptive MAP selection scheme for HMIPv6 networks. In the adaptive MAP selection scheme, an MN first esti- mates its session-to-mobility ratio (SMR). Then, based on its SMR, the MN chooses a MAP that minimizes the total cost, consisting of the binding update cost and packet delivery cost. In addition, the MN calculates two threshold SMR values, which adaptively trigger a new MAP selection procedure. If the estimated SMR is larger (or smaller) than the upper (or lower) threshold SMR value, the MN recal- culates the total cost and re-selects a MAP that minimizes the total cost. Simulation results indicate that the adaptive MAP selection scheme achieves a lower total cost and a better load balancing than the previous schemes. Ó 2005 Elsevier B.V. All rights reserved. Keywords: Hierarchical Mobile IPv6; Mobility anchor point; MAP selection scheme; Performance analysis 1. Introduction In IP-based wireless/mobile networks, there are different types of mobility agent (e.g., the home agent (HA) and for- eign agent (FA)) that are used to support host mobility. Mobile IPv6 (MIPv6) [1] is the de facto mobility protocol in IPv6 wireless/mobile networks. Hierarchical Mobile IPv6 (HMIPv6) [2] was proposed by Internet Engineering Task Force (IETF) to mitigate the high signaling overhead that is incurred in Mobile IPv6 networks when mobile nodes (MNs) perform frequent handoffs. In HMIPv6 networks, the mobility anchor point (MAP) has been introduced in order to handle binding update (BU) procedures due to handoffs within a MAP domain in a localized manner, which reduces the amount of net- work-wide signaling traffic for mobility. In HMIPv6 net- works, an MN configures two care-of-addresses (CoAs): a regional care-of-address (RCoA) and an on-link care- of-address (LCoA). The RCoA is an address on the MAP’s subnet. An MN configures an RCoA when it receives a Router Advertisement (RA) message with the MAP option. On the other hand, the LCoA is an on-link CoA attributed to the MN’s interface based on the prefix infor- mation advertised by an access router (AR). Fig. 1 illustrates the basic operations that are performed in HMIPv6 networks. An MN entering a MAP domain will receive an RA message containing information on the MAP. Then, the MN sends a BU message to the MAP, which binds its current location (i.e., LCoA) with an address on the MAP’s subnet (i.e., RCoA). The MAP acts as a local HA and, as such, it receives all packets on behalf of the MNs it is serving. That is, the MAP decapsu- lates and forwards the received packets to the MN’s cur- rent address. If the MN changes its current address within a MAP domain, it only needs to register the new address (i.e., new LCoA) with the MAP. The RCoA does not change as long as the MN moves within the same 0140-3664/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.comcom.2005.11.004 * Corresponding author. Tel.: +82 2 880 9105; fax: +82 2 872 2045. E-mail addresses: shpack@mmlab.snu.ac.kr (S. Pack), mjnam@ kt.co.kr (M. Nam), tkkwon@snu.ac.kr (T. Kwon), yhchoi@snu.ac.kr (Y. Choi). www.elsevier.com/locate/comcom Computer Communications 29 (2006) 3066–3078