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Firefly: Scalable, Ultra-Accurate Clock Synchronization for Datacenters#

SIGCOMM 2025 digest Program Wildcard pick Coimbra · 8–11 September 2025

Abstract Paper Recording

Pooria Namyar et al. (Google, USC, NVIDIA)

Play the recording: Firefly: Scalable, Ultra-Accurate Clock Synchronization for Datacenters

Why: Precise time quietly underpins distributed consistency, certificate/token validity windows, and ordering — sub-10ns in software is a striking result with security and distributed-systems reach.

What: A software-driven clock-sync system hitting sub-10ns device-to-device and ≤1µs device-to-UTC in a 248-machine Clos, resilient to time-server failure and unstable clocks.

How: Distributed consensus on a random overlay graph with gradual hardware-clock adjustment, plus "layered synchronization" decoupling internal (device-to-device) from external (to-UTC) sync.

Where applicable: Datacenter timing (e.g., cloud financial exchanges); software-only, broadly applicable where hardware PTP is impractical.