Current techniques for evaluating wireless applications Simulation

1. ModelNet: A Large-Scale Network Emulator for Wireless NetworksPriya Mahadevan, Ken Yocum, and Amin Vahdat Duke University, http://issg.cs.duke.edu Goal: To subject unmodified wireless applications using distributed emulation to realistic mobile and ad hoc scenarios ModelNet Architecture Motivation • Current techniques for evaluating wireless applications • Simulation • Limited scalability, need to rewrite applications for the simulator, leave out important details of the system • Live deployment • limited in size, not reproducible, hard to isolate faults • Emulation • static, small scale, hard to configure • Our Requirements • Combine advantages of live deployment and simulation • Support large scale applications • Run unmodified applications on unmodified OS’s • Reproducible behavior • Allow movement patterns during the experiment • Modelnet Cores • Responsible for routing packets and performing the actual emulation • Edge nodes • Run user-level services • Pipes • Are used for emulation , have bandwidth, loss-rate and latencies associated with it • Virtual Nodes • Have an IP address and corresponding location in the emulated topology Implementing ad hoc protocols ModelNet Usage • Core keeps track of all the routing info for each VC • Core simulates the effect of the routing protocols by generating and handling all route requests/updates and broadcast packets • Creation • Generate initial mobile/adhoc topologies • Assignment • Assign pipes to ModelNet cores • Binding • Assign VN to edge nodes, bind physical nodes to cores • Execution • Execute target applications Wireless Environment Emulation Initial Results • On any topology change, determine new routes and neighbor sets for each node • Insert dummy packets into the queues of all nodes within range of a transmitting node to capture bandwidth sharing inherent to the broadcast medium • All packets from A to B consume bandwidth at all the neighboring nodes of A as well as B. This is unlike wired networks where bandwidth is consumed only at the link connecting nodes A and B • Ad hoc Scenario • Square with side 670m, 50 mobile hosts with random start points • Implement the “random wavepoint” model Future Research • Emulating MAC layer • Implementing various ad hoc routing protocols in ModelNet core