Enhancing DHCP for Address Autoconfiguration in Multi-hop WLANs

To extend the coverage area of conventional WLANs and to provide better mobility support, multi-hop WLANs are emerging as a viable and cost-effective solution. A possible way to construct such a multi-hop WLAN system is to employ an ad hoc routing protocol to discover and maintain the multi-hop paths between the clients and the access points. A prerequisite of proper routing is that all the nodes have a unique network-layer identifier. However, traditional autoconfiguration protocols commonly used in infrastructure-based WLANs, such as DHCP, are not directly applicable in this context due to multi-hop relaying between hosts. In this paper we propose an enhancement of DHCP to enable dynamic address allocation of mobile nodes in multi-hop WLAN systems, without changing the legacy implementation of the DHCP servers. We have implemented a prototype of our solution, and we have measured the maximum delay needed to configure an IP address under various topology configurations and network loads. Our experimental results indicate that the proposed mechanism is quite fast in lightly loaded networks, while the contention between data traffic and control messages may significantly increase the configuration delay.