| ▲ | White Rabbit – sub-nanosecond synchronization for large distributed systems(ohwr.org) |
| 40 points by michaelsbradley 2 days ago | 11 comments |
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| ▲ | pjdesno 11 minutes ago | parent | next [-] |
| If you run "make" in the papers/IBIC2013 directory you'll get this paper:
https://cds.cern.ch/record/1743073/files/thbl2.pdf 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) |
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| ▲ | skulk 3 hours ago | parent | prev | next [-] |
| Haven't looked into this in depth but sub-nanosecond sync for systems up to 10km apart is interesting since 10km is about 33 light microseconds. There is some trickery going on. |
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| ▲ | elromulous 2 hours ago | parent | next [-] | | It's totally possible to achieve synchronization better than light transmission time. For the purposes of synchronization, the speed of light delay, and any other delay are indistinguishable, and need not be distinguished. | |
| ▲ | ooterness 2 hours ago | parent | prev | next [-] | | Two-way time transfer measures the round-trip propagation time. As a result, it's not directly relevant to the accuracy. | |
| ▲ | colechristensen 2 hours ago | parent | prev | next [-] | | The gravity well time dilation is about 3.5 nanoseconds per meter per year near the surface of the earth. (time changes rate with altitude in a gravity well) Sub-nanosecond synchronization is getting into the relativity is measurable realm. | | |
| ▲ | mike_hock an hour ago | parent [-] | | That means you get a free clock cycle every 2-3 hours on top of a mountain compared to sea level! | | |
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| ▲ | UltraSane 2 hours ago | parent | prev [-] | | Yes, it uses phased locked loops and measures phase difference between the master clock and the local clock. |
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| ▲ | roughly an hour ago | parent | prev | next [-] |
| Haven't dug in on the technicals, but this is coming out of CERN, it looks like - and in that light, the links to "We're hiring" on that page almost feel like a flex... |
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| ▲ | LowLevelKernel 33 minutes ago | parent | prev [-] |
| Not on GitHub? |
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| ▲ | boguscoder 3 minutes ago | parent [-] | | Its on gitlab but even there I failed to find sources, documentation/presentations are there though |
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