SplayNet: Distributed User-Space Topology Emulation

Abstract. Network emulation allows researchers to test distributed ap-plications on diverse topologies with fine control over key properties such as delays, bandwidth, congestion, or packet loss. Current approaches to network emulation require using dedicated machines and low-level operating system support. They are generally limited to one user deploy-ing a single topology on a given set of nodes, and they require complex management. These constraints restrict the scope and impair the up-take of network emulation by designers of distributed applications. We propose a set of novel techniques for network emulation that operate only in user-space without specific operating system support. Multiple users can simultaneously deploy several topologies on shared physical nodes with minimal setup complexity. A modular network model allows emulating complex topologies, including congestion at inner routers and links, without any centralized orchestration nor dedicated machine. We implement our user-space network emulation mechanisms in SplayNet, as an extension of an open-source distributed testbed. Our evaluation with a representative set of applications and topologies shows that Splay-Net provides accuracy comparable to that of low-level systems based on dedicated machines, while offering better scalability and ease of use