Firefly: Nanosecond Clock Synchronization for Data Centers
🕒 Firefly is a software-driven clock synchronization system from Google that achieves nanosecond-level timing across data center NICs using commodity hardware. It separates fast internal NIC-to-NIC consensus from external UTC alignment and builds consensus over a d-regular random graph. Practical techniques—RTT filtering, path profiling, and optional switch/NIC features—reduce jitter and asymmetry. It yields consistent sub-10ns internal alignment while scaling to large fabrics.
