Virtual routers: a tool for emulating IP routers

Setting up experimental networks of a sufficient size is a crucial element for the development of communication services. Unfortunately, the required equipment, like routers and hosts, is expensive and its availability is limited. On the other hand, simulations often lack interoperability to real systems and scalability, which limits the scope and the validity of their results. Therefore, an intermediate approach between these two alternatives that allows for setting up testbeds on a cluster of computers is needed. This paper presents an intermediate approach based on the emulation of IP routers and evaluates the concept. In a first set of experiments the impact of various parameters on the packet delay was investigated, while further experiments compare the performance of differentiated services run on the network emulator with the results obtained by the well known network simulator ns.