Stateless routing in network simulations

The memory resources required by network simulations can grow quadratically with the size of the simulated network. In simulations that use routing tables at each node to perform per-hop packet forwarding, the storage required for the routing tables is O(N/sup 2/), where N is the number of simulated network nodes in the topology. Additionally, the CPU time required in the simulation environment to compute and populate these routing tables can be excessive and can dominate the overall simulation time. We propose a new routing technique, known as Neighbor-Index Vectors, or NIx-Vectors, which eliminates both the storage required for the routing tables and the CPU time required to compute them. We show experimental results using NIx-Vector routing in the popular network simulator ns (S. McCanne and S. Floyd, 1997). With our technique, we achieve a near order of magnitude increase in the maximum size of a simulated network running ns on a single workstation. Further, we demonstrate an increase of two orders of magnitude in topology size (networks as large as 250000 nodes) by using this technique and running the simulation in parallel on a network of workstations.