Realistic Large-Scale Online Network Simulation

Abstract

Large-scale network simulation is an important technique for studying the dynamic behavior of networks, network protocols, and emerging classes of distributed applications (e.g. Grid, peer-to-peer, etc.) Large scale and realism are two critical requirements for network simulations of Grid application studies. Our work here extends previous efforts in three key ways. First, we study networks 100 times larger than in our previous studies (20000 routers). Second, at this scale, we study realistic network structures (100 ASs, BGP4 and OSPF routing) versus flat OSPF routing. Finally, we describe and evaluate a new profile-based load-balancing approach called hierarchical profile-based load balance. Our extensive large-scale experiments with profile-based load balance (PROF) on flat-routed (OSPF) networks show that PROF outperforms several other techniques based on topology and static application information. However, these results and those for multi-AS networks motivate our invention of a new hierarchical technique (HPROF) which clusters network nodes to achieve a desired minimum link latency (MLL), a key determinant of simulation parallelism, then applies the graph partitioner. HPROF explicitly controls the trade-off between simulation efficiency and available parallelism, producing robust and superior performance for large-scale networks, including both single-AS and multi-AS networks. HPROF can improve load imbalance by 40%, and reduce the simulation time by about 50% in our 20000 router simulations executed on 128-node clusters. The parallel efficiency achieved by these simulations is over 40%, providing substantial capabilities for simulating large networks. In summary, these advances demonstrate that realistic large-scale network simulation for networks of 20000 routers (comparable to a large Tier-1 ISP network such as AT&T) can be accomplished with our system. To demonstrate the capabilities of our simulation tool, we simulate a large-scale Denial-of-Service attack in a large-scale network with 10000 routers organized as 40 Autonomous Systems. The simulation includes over 400 live application processes, the DoS attack and application entities, and generates aggregate traffic of over 6 Gbps.