A Composable Emulation Framework for Whitebox Switches

High-fidelity network emulation is indispensable for reliable operation at scale. While existing emulators are built for monolithic, blackbox switches, emerging switch architectures are chipping away at this assumption. Cloud providers routinely source device modules from different vendors and compose them together to construct disaggregated, whitebox switches. This raises novel challenges in network emulation, as we must move from building bespoke firmware-based emulators to a composable emulation framework where diverse emulators can be stitched together for high-fidelity emulation: whether for data plane, control plane, or peripheral modules (e.g., optical components). We have designed the first such framework, MirSwitch, addressing key challenges in reconciling interface contract differences across emulator modules using an adaptor-centric approach. MirSwitch can faithfully emulate a wide range of functionalities of whitebox switches, while achieving 2.2× forwarding performance improvements which are critical for forwarding emulation. We have deployed MirSwitch in our production network, which our operators have used to troubleshoot 97.5% of a total of 203 issues in a recent year.