Comment by bux93

The paper mentions TCXOs and OCXOs, respectively temperature and oven-controlled crystal oscillator. You can get PCIe cards that have these on them, and devices for audio studios with a rubidium oscillator like the Tascam CG-1800.

Jane Street has a podcast that lifts the veil a little bit on how they keep their gear synced up, which is pretty interesting: https://signalsandthreads.com/clock-synchronization/