May 1, 2007

NS-2 Emulation Extensions

The network simulator ns-2 is a widely accepted discrete event network simulator, actively used for wired and wireless network simulations. It has a highy detailed model of the lower layers (Physical and MAC) of wireless IEEE 802.11 networks.

Ns-2 has also an emulation feature, i.e. the ability to introduce the simulator into a live network and to simulate a desired network between real applications in real-time.

Within the scope of this project we developed some methods and extensions to the ns-2 to combine wireless network simulation and network emulation. Now ns-2 can emulate an arbitrary IEEE 802.11 network between real applications. Furthermore, our extensions are generic, i.e. can be applied to any network supported in the ns-2.

NS-2 emulation extensions use two methods for network emulation: Single Host and Distributed Clients. In the first method the simulator and all the applications run on one computer. We use User-Mode-Linux virtual machines and emulate a ns-2 netwok among them. The applications run inside the virtual machines and do not notice that they communicate through a simulated network.

In the Distributed Clients method we run the applications and the simulator on separated machines for better scalability. Here we use TUN/TAP virtual network interfaces and map them to nodes in the ns-2 simulator. The network among these TUN/TAP interfaces is again simulated. The applications interact with it in the same way they would interact with a real network.

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