What I would actually like to see is how this performs in a more real world situation. Like does this increase line error rates, causing the transport or application to have to resend at a higher rate, which would erase all savings by having lower latency. Also if they are really signaling these in the multi GHz are these passive cables acting like antenna, and having a cabinet full of them just killing itself on crosstalk?
Look at the graphs. The fiber has a higher slope; each meter adds more latency than a meter of copper.
This is simply due to the speed of electromagnetic wave propgation in the different media.
https://networkengineering.stackexchange.com/questions/16438...
Both the propagation of light in fiber and signal propagation in copper are much slower than the speed of lightin vaccuum, but they are not equal.
No glass, just some reflective coating on the inside of a waveguide (hollow tube).
https://azure.microsoft.com/en-us/blog/how-hollow-core-fiber...
Surely resignaling should be the fixed cost they calculate at about 1ns? Why does it also incur a 0.4ns/m cost?
Speed of electricity in wire should be pretty close to c (at least the front)
This is why point-to-point microwave links took over the HFT market -- they're covering miles with free space, not fiber.
It seems there is quite a wide range for different types of cables so some will be faster and others slower than optical fibre. https://en.wikipedia.org/wiki/Velocity_factor
But the resignalling must surely be unrelated?
Obligatory Adm. Grace Hopper nanosecond reference:
c is the speed of light in a vacuum, but it is not really about light, it is a property of spacetime itself, and light just happens to be carried by a massless particle, which, according to Einstein's equations, make it go at c (when undisturbed by the medium). Gravity also goes at c.
(Physicists will in fact use the c=1 convention when keeping track of the distinction between distance units and time units is not important. A related convention is hbar=1.)
You can tell that c is fundamental, rather than just a property of light, from how it appears in the equations for Lorentz boosts (length contraction and time dilation).
EM signals move at about 0,66c in fiber, and about 0,98c in copper.
The insulation slows it down.
Especially since physics imposes a ~1.67ns/m penalty on fiber. The best-case inverse speed of light in copper is ~3.3ns/m, while it's ~5ns/m in fiber optics.
(My naive view is that they're both 'just copper'?)
Faster parallel DACs require more pairs of coax, and thus are thicker and more expensive.
With both ends connected to a device? No.
Aside from that you've got a linear scrambler into balanced drivers into twisted pair. It's about as noise immune as you can get. Unless you put the noise right up next to the cable itself.
Latency is well defined and nobody is quibbling on that.
Maybe it's all about sufficient bandwidth - now that it's ubiquitous, latency tends to be the dominant concern?
A cat video will start displaying much sooner with 1 Mbps of bandwidth compared to 100 Kbps:
> taking a comparatively short time
* https://www.merriam-webster.com/dictionary/fast § 3(a)(2)
> done in comparatively little time; taking a comparatively short time: fast work.
* https://www.dictionary.com/browse/fast § 2
So an online experiences happens sooner (=faster-in-time) with more bandwidth.
So basically: Lower latency, lower bandwidth?
No: DAC and (MMF/SMF) fibre will (in this example) both give you 10Gbps.
> The low-latency of Arista switches has made them prevalent in high-frequency trading environments, such as the Chicago Board Options Exchange[50] (largest U.S. options exchange) and RBC Capital Markets.[51] As of October 2009, one third of its customers were big Wall Street firms.[52]
* https://en.wikipedia.org/wiki/Arista_Networks
They've since expanded into more areas, and are said to be fairly popular with hyper-scalers. Often recommended in forums like /r/networking (support is well-regarded).
One of the co-founders is Andy Bechtolsheim, also a co-founder of Sun, and who wrote Brin and Page one of the earliest cheques to fund Google:
And, if we neglect how long the signal can travel like the authors do, copper is always going to win this fight vs. fiber because copper can use air as its dielectric but fiber cannot.
Try running Cat cables on powerlines like Aerial Fibre
But I think I understand what you mean.
The shape of individual EM waveforms is no longer relevant instead there are just buckets of got some or not.
Not enough to matter in this comparison, but i thought I should mention it.
Which is why you get network topologies other than 'just' fat tree in HPC networks:
* https://www.hpcwire.com/2019/07/15/super-connecting-the-supe...
This specifically mentions the 7130 model, which is a specialized bit of kit, and which Arista advertises for (amongst other things):
> Arista's 7130 applications simplify and transform network infrastructure, and are targeted for use cases including ultra-low latency exchange trading, accurate and lossless network visibility, and providing vendor or broker based shared services. They enable a complete lifecycle of packet replication, multiplexing, filtering, timestamping, aggregation and capture.
* https://www.arista.com/en/products/7130-applications
It is advertised as a "Layer 1" device and has a user-programmable FPGA. Some pre-built applications are: "MetaWatch: Market data & packet capture, Regulatory compliance (MiFID II - RTS 25)", "MetaMux: Market data fan-out and data aggregation for order entry at nanosecond levels", "MultiAccess: Supporting Colo deployments with multiple concurrent exchange connection", "ExchangeApp: Increase exchange fairness, Maintain trade order based on edge timestamps".
Latency matters (and may even be regulated) in some of these use cases.
The differing slope of the lines is due to velocity factor in the cable. The speed of light in vacuum is much faster than in other media. And the lines diverge the longer you make them.