200623 clock synchronisation

Clock synchronisation at serious speed

British engineers say they have developed a technique that synchronises the clocks of computers in under a billionth of a second.

What they call “clock phase caching” could eventually eliminate one of the hurdles for the deployment of all-optical networks, potentially leading to more efficient data centres, they suggest in a paper in the journal Nature Electronics.

“It has the potential to transform communication between computers in the cloud, making key future technologies like the internet of things and artificial intelligence cheaper, faster and consume less power,” says lead author Kari Clark, from University College London (UCL).

Server-to-server traffic in data centres is increasing by 70% each year, the researchers say, which is difficult to meet with existing technologies.

Until now, cloud providers have been able to accommodate rapid growth by relying on Moore’s Law for networking, whereby about every two years electronic switch integrated circuits double their data transmission speed at the same cost and power.

However, the sustainability of this approach is increasingly being questioned due to the difficulty of continuing to be able to make silicon transistors smaller and faster.

All-optical networks that use light to both transmit and route data are a promising alternative, but their viability has been limited by the need for each server to continuously adjust its clock time according to incoming data.

Clark’s work with colleagues from UCL and Microsoft shows, they say, that by synchronising clocks of all connected servers via optical fibre, and programming hardware to memorise clock phase values so clock time does not have to be re-checked, the time to “recover” the clock could be practically eliminated.

Their prototype can synchronise the clocks of thousands of computers in the time it takes light to travel 30 centimetres through the air. This resulted in a significant increase in the performance of optical switching compared to state-of-the-art solutions, they report.

“While there is still a long way to go, this technique brings us a step closer to the vision of an all-optical data centre,” note co-authors Hitesh Ballani and Paolo Costa, from Microsoft Research Cambridge.

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