VNLAYER BASED IPV6 ROUTING PROTOCOLS FOR MOBILE AD HOC NETWORKS

The Virtual Node Layer [1] (VNLayer) is a programming abstraction for a Mobile Ad-Hoc Network (MANET), defining virtual servers at fixed locations of the geographical area covered by the network. The fixed virtual servers are emulated by a subset of the mobile nodes. The advantage of this abstraction is that simple wireline protocols can be deployed on the infrastructure to tame the difficulties inherent in the MANET setting. A disadvantage is the overhead of implementing the Virtual Node Layer. We designed an ns-2 [4] based simulation package (VNSim) for the VNLayer. The implementation of the VNLayer uses a leader-based state replication strategy to emulate the virtual nodes. A VNLayer based address allocation algorithm based on DHCP [5] is implemented and evaluated using VNSim. The simulation results show that VNSim can efficiently simulate a virtual node system with up to a few hundred mobile nodes; that the VNLayer overhead is quite small; and that the address allocation protocol performs well in a small network of 16 regions with 40 to 120 mobile nodes and a larger network of 64 regions with 160 mobile nodes. Rate of motion for the mobile nodes varies from quite slow to quite fast. Topology based or geographically based IPv6 routing protocols can be deployed on the overlay network of fixed virtual nodes, creating a hierarchical MANET routing system. In such a system, the clean separation between hosts and routers eliminates the need for extensive changes to the hosts. The use of a fixed overlay network can prevent excessive message flooding. Extending earlier ns-2 based simulation studies of such virtual node systems, we propose to investigate the performance and the failure modes of virtual node based IPv6 routing protocols in MANETs. Simple IPv6 routers will be implemented in VNSim. The message overhead and routing performance of various virtual node based IPv6 routing protocols will be evaluated and compared with standard MANET routing protocols like AODV and a simple VNLayer based routing protocol, geocast.