Dynamic control of the address binding update for mobile nodes in a hierarchical mobile IP network

Hierarchical Mobile Internet Protocol version 6 (HMIPv6) has been proposed by the Internet Engineering Task Force (IETF) as an enhancement of the MIPv6. It is designed to reduce the amount of required signaling and to speed up the hand-off operation for mobile connection by means of hierarchical routing. In the HMIPv6, a router called the Mobile Anchor Point (MAP) serves mobile nodes (MNs) to aid their address binding and update as a local home agent. However, as the number of MNs increases in a MAP domain, the resource of the MAP becomes scarce, which increases the chance of failing in admitting new and hand-off MNs. Therefore some control scheme is needed in order to guarantee the quality of service (QoS) of the network. In this paper, we propose a dynamic control of the address binding update for the MNs in an HMIPv6 network. We consider three types of MNs entering the MAP domain, namely, a new MN, a hand-off MN in the sleep mode, and a hand-off MN in the active mode. We impose different costs on rejection of requests from these MNs, since the forced termination of an ongoing communication causes greater pain to a user than blocking a new MN. An optimal admission policy is obtained from a semi-Markov decision process with respect to the number of MNs present in a MAP domain. Based on this optimal policy, we calculate the probabilities of blocking each type of MN. We show numerically that our control reduces the probability of rejecting active mode hand-off MNs at little expense of blocking new MNs. It is also shown that our dynamic control outperforms the static control based on the guard channel scheme.