Simulating Fixed Virtual Nodes for Adapting Wireline Protocols to MANET

The virtual node layer (VNLayer) is a programming abstraction for mobile ad hoc networks (MANETs). It defines simple virtual servers at fixed locations in a network, addressing a central problem for MANETs, which is the absence of fixed infrastructure. Advantages of this abstraction are that persistent state is maintained in each region, even when mobile nodes move or fail, and that simple wireline protocols can be deployed on the infrastructure, thereby taming the difficulties inherent in MANET setting. The major disadvantage is the messaging overhead for maintaining the persistent state. In this paper, we use simulation to determine the magnitude of the messaging overhead and the impact on the performance of the protocol. The overhead of maintaining the servers and the persistent state is small in bytes, but the number of messages required is relatively large. In spite of this, the latency of address allocation is relatively small and almost all mobile nodes have an address for 99 percent of their lifetime. Our ns-2 based simulation package (VNSim) implements the VNLayer using a leader-based state replication strategy to emulate the virtual nodes. VNSim efficiently simulates a virtual node system with up to a few hundred mobile nodes. VNSim can be used to simulate any VNLayer-based application.