Figure: Dummynet network architecture. Click on the image for a more detailed description on the Dummynet webpage.

Network testbeds have become very popular to support research on network protocols and distributed applications. To reproduce network behaviour, testbeds range between two extremes: use a fully emulated network, or distribute nodes on the real Internet. The former approach yields very reproducible results but might be a poor representation of reality; the latter gives more realistic but less reproducible scenarios. Researchers at University of Pisa, a OneLab lead partner, have developed Dummynet, an emulation solution for the PlanetLab testbed system. This innovation gives researchers the advantages of emulation while keeping the option of running experiments in a large and heterogeneous testbed with realistic network conditions.

Dummynet is an emulation tool originally designed for testing networking protocols, and since then used for a variety of applications including bandwidth management. It simulates/enforces queue and bandwidth limitations, delays, packet losses, and multipath effects. It also implements a variant of Weighted Fair Queueing called WF2Q+. It can be used on user's workstations, or on machines acting as routers or bridges.