When a simulation job is submitted, it is sent to an job queue. Based on the current availability of the node and the job settings, the total numbers of clients required for simulation are further divided into smaller groups, let's say 100 clients each. Simulation for each chunk of client is then submitted as an individual task, i.e. if you would like to simulate 1000 clients, your first 100 clients could be simulated by one VM while the next 100 clients could be running on another machine. Once all tasks have been distributed, the job is marked as running.