White Rabbit – sub-nanosecond synchronization for large distributed systems
ohwr.org
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It's quite interesting - this isn't ethernet as we know it. Instead of each NIC using its own free-running clock, all the physical layers are sync'ed to each other at layer 1. (note that gigabit ethernet, which is what it uses, sends data at all times - when idle it sends the idle symbol)
Sub-nanosecond synchronization is getting into the relativity is measurable realm.
Just because there are ninety nine ways to do something wrong doesn't mean there couldn't exist one way to do it right. In the case of space datacenters, there absolutely exists a way to do it effectively. Dumb VCs will never know the difference.
It's the physics of cooling the beasts and the communication delays that make those plans ludicrous.
To turn your assertion on its head, the fact that the supporters don't seem to be able (or willing) to do the math to fact check these proposals is not an indicator that the plans will work.
As a starting point for comparison, the total power budget of the ISS is under 100kW and a single supercomputer rack dissipates about 4x that. What changes to the ISS can be made to get 100x more power and dissipate 100x more heat?
1. There is no real size limit to radiators in space, especially when in solar orbit.
2. High temperature chip architectures can be used, operating at 600K.
3. Heat pipes can bring the temperature even higher, such as to 1200K.
4. Special 3D radiator geometries can be used to optimize heat escape.
5. Metamaterials can be used to optimize photon emission in the best directions.
Together, these will shrink the required radiator area dramatically. Beyond these standard ideas, other exotic approaches exist at the edge of viability.
The ISS in contrast is restricted considering it has to sit in Earth orbit.
You may see this video (AI researched and generated) to grasp some of the points: https://www.youtube.com/watch?v=s7Mv_OcBXI8
Since cm precision is often not possible, is roundtrip-length an estimated average from prior roundtrips?
jitter kills
* you measure the round trip time often enough
* the shift affects light in both directions equally
P.S. There is WR workshop this week with some talks being publicly available on CERN's indico website.
In short, it's about giving PTP and SyncE some extra smarts.
I'm not sure why you would think that? If you can assume the fiber is the same in both directions you know the round trip time is exactly double the latency of the connection. Then you know to phase shift your start time by that much when you get a start signal and you're in sync.
Obviously it's not trivial in practice, but it's not a fundamentally insurmountable problem.
Of course no doubt there’s some requirements that cannot avoid that requirement.
But for the most part needing synchronized time is just going to be a forever problem isn’t it?
Tight clock sync collapses this. If clock uncertainty ε is small and bounded, you can timestamp a write, wait ε, and trust the global order without talking to anyone. Spanner’s external consistency works because TrueTime’s ε was a few milliseconds, so commit-wait was tolerable. The latency cost of planet-scale serializability stops depending on how far apart your replicas are and starts depending on how good your clocks are.
That’s the real significance. Time sync converts a coordination problem (bounded by physics) into a local computation (bounded by clock quality). Spanner proved this is possible but required GPS receivers and atomic clocks in every datacenter, which kept the capability inside Google for years. White Rabbit-class sync pushes ε from milliseconds toward sub-nanoseconds over commodity Ethernet hardware, and it’s now in IEEE 1588 as a standard PTP profile. If sub-nanosecond sync becomes baseline network infrastructure, the long-held assumption that strong consistency has to be slow at geographic scale stops holding, and a meaningful chunk of what databases currently work around (HLCs, weak isolation defaults, application-level reconciliation) becomes unnecessary.
But if we imagine the vast majority of internet and telecom infrastructure is also implemented this way, we can reason about information over time in general. Makes me think of 'earth is a big computer' type of sci fi trope. Neat!
Note that this is also for a large part a hardware-based technology