So the findings here do make sense. For sub 5m cables directly connecting two machines is going to be faster then having some PHY in between that has to resignal. I'm surprised that fiber is only 0.4ns/m worse then their direct copper cables, that is pretty incredible.
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?
"Has lower latency than" fiber. Which is not so shocking. And, yes, technically a valid use of the word "faster" but I think I'm far from the only one who assumed they were going to make a bandwidth claim rather than a latency claim.
Faster only because the distances involved are short enough that the PHY layer adds significant overhead. But if you somehow could wave a magic wand and make optical computing work, then fiber would be faster (& generate less heat).
This coming from Arista is unsurprising because their original niche was low-latency, and the first industries that they made in-roads in against the 'incumbents' was finance:
> 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]
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:
IIRC, the passive copper SFP Direct Attach cables are basically just a fancy "crossover cable" (for those old enough to remember those days). Essentially there is no medium conversion.
Its been long known that Direct Attach Copper (DAC's) are faster for short runs. It makes sense since there does not need to be an analog-digital conversion.
Its not copper that's faster, it's the dielectric in between the twisted pair that has a lower index of refraction.
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.
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[ 5.2 ms ] story [ 30.5 ms ] threadWhat 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?
> 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:
* https://en.wikipedia.org/wiki/Andy_Bechtolsheim
https://en.wikipedia.org/wiki/Velocity_factor
Not enough to matter in this comparison, but i thought I should mention it.
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.
https://pmc.ncbi.nlm.nih.gov/articles/PMC11548225/
Copper is Faster than Fiber in some circumstances.