Time Jails: A Hybrid Approach to Scalable Network Emulation

It is essential to evaluate the performance of newly developed distributed software and network protocols. Network emulation enables reproducible evaluation of unmodified real implementations. Software built for distributed systems, such as a large scale peer-to-peer system, requires evaluation scenarios with thousands of communicating nodes. Two approaches for scaling network emulation to such scenario sizes have been proposed in the literature: node virtualization and time visualization. Node visualization allows maximizing the utilization of standard hardware used for emulation experiments. Time visualization enables trading experiment duration for visually increased resources of the hardware. It stands to reason that a combination of those two approaches may increase scalability even further. However, in existing combinations, either node visualization implies relatively high overhead or time virtualization requires modifications of the test subject implementation. In this paper, we present a novel hybrid approach called time visualized emulation environment (TVEE). It integrates node visualization with low overhead and time virtualization, which is transparent to the execution of test subjects. We introduce visual time based on epochs to enable better dynamic hardware utilization during long lasting experiments. Additionally, a mechanism similar to soft timers ensures an accurate reproduction of network properties in the time visualized emulation. Our evaluations show the accuracy and scalability of time visualized network emulation. Comparing TCP throughput, TVEE outperforms other approaches using an event based visual time by an order of magnitude.