Mobility support in IP networks requires servers to forward packets to mobile hosts and to maintain information pertaining to a mobile host's location in the network. In the mobile Internet Protocol (mobile-IP), location and packet forwarding functions are provided by servers referred to as home agents. These home agents may become the bottleneck when there are a large number of mobile hosts in the network. In this paper, we consider the design and analysis of a replicated server architecture in which multiple home agents are used to provide mobility support. In order to minimize the delay across the home agents, one of the key aspects is the design of load balancing schemes in which a home agent may transfer the control of a mobile host to another home agent in the same network. The methods for triggering the transfer and the policy for selecting the next home agent define various load balancing schemes which have different performance characteristics. In this paper, we design a protocol that forms the building block for implementing such load balancing schemes, and we then study the performance characteristics of random, round-robin, and join the shortest queue (JSQ) selection policies, and timer-, counter- and threshold-based transfer policies.

A location system utilizes sensors to track the locations of mobile users with badges. A badge periodically transmits location messages to the sensor in the room. Based on a location message, the system updates or re-confirms the position of the badge. A major performance issue of the location system is the determination of the frequency that a badge transmits the location messages (or the registration message).

In this paper, we propose an analytic model to study this performance issue. Our study indicates that in many cases, by decreasing the registration frequency (and consequently saving battery power), the location system may still maintain low lost-call probability. We also observe an interesting phenomenon that if the user movement pattern is highly irregular, the opportunity of losing a call becomes smaller.

This paper illustrates a protocol for wireless ATM networks which makes use of in-band signaling, i.e., of ATM resource management cells, to process network handovers and guarantee the in-sequence and loss-free delivery of the ATM cells containing user data. The proposed approach aims at minimizing the necessary modifications of the ATM signaling standard required to superimpose user mobility onto the fixed network infrastructure, and provides for a gradual upgrade of the fixed network to handle mobility. The proposed protocol handles both local handovers, in which the connection access point needs not migrate to a new ATM local exchange, and global handovers, in which the connection access point must migrate to a new local exchange. The maximum buffering capacity necessary at the base station to guarantee in-sequence and loss-free cell delivery is estimated using a simple model that is studied by means of an ATM network simulation tool.

Recent years have seen an explosive growth of interest in mobile networks that support the mobility. The mobility of users, the transmission of signals through open air and the requirement of low power consumption by a mobile user bring to a mobile network a large number of new security issues. In this paper, we propose an optimized protocol for mobile network authentication and security. The particular features of the new proposal are: (1) only a public parameter (a large prime p) and the public key of the certification authority $(y_{ca})$ is required knowledge for all network participants; (2) only a block cipher is used as both the secret-key encryption algorithm and the underlying cipher of the hash function.}}