Network emulation is an efficient method for evaluating distributed applications and communication protocols by combining the benefits of real world experiments and network simulation. The process of network emulation involves the execution of connected instances of the software under test (called virtual nodes) in a controlled environment. In previous work, we introduced an approach to minimize the runtime of network emulation experiments based on prior known average resource requirements of virtual nodes.

In this paper, we introduce NETbalance, a novel approach to runtime reduction for experiments with unknown or varying resource requirements. NETbalance migrates virtual nodes during an experiment to distribute the load evenly across the physical nodes, avoiding overloaded nodes and exploiting the idle resources on underloaded nodes for speeding up the experiment execution. We make the following contributions: First, we present an emulation architecture for efficiently supporting live migration of virtual nodes. Second, we propose a cost model for determining the runtime reduction achieved through the migration. Third, we introduce an algorithm for calculating placements that minimize the experiment runtime. Our evaluations of the NETbalance prototype show, that it is able to reduce the experiment runtime by up to 70%.