3 ms·

I have one question regarding the statement: "the cloud infrastructure cannot be more than 100km from the end device consuming the application, due to the fini

by prth 10y ago

I have one question regarding the statement: "the cloud infrastructure cannot be more than 100km from the end device consuming the application, due to the finite speed of light, which can only traverse ~100km (round trip) in the 1 ms that is available for the networking portion ..." Since light would traverse ~299km in 1ms, would the max distance of the cloud architecture be ~149.9km - assuming we do not take into account any additional processing and response times? Edit: The author was using the speed of light in current-day fibre-optics as an estimation (~213km in 1ms, a reduction of about 30% from vacuum). Relevant - http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.2013.45.html http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.201...

cmdrfred 10y ago
Is that not the speed of light in a vacuum? I believe its different in different mediums.
- jarvist 10y ago
  Yes, it's about 2/3 c (speed of light) in a fibre optic (refractive index n=1.44), and about 1/3 c in a copper cable. Air barely slows it down.
  - zoren 10y ago
    Do you have a source on the 1/3 c in copper?
    - iheartmemcache 10y ago
      http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.2013.45.html http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.201... Here's a definitive src on .69c for an 'ideal' fibre velocity factor. Here are two sources, both of which have prop. velocities @ around .6c depending on the dialectric. Again ideal. I haven't architected any long-run infrastructure, but 1/3rd sounds pretty right to me. https://cdn.shopify.com/s/files/1/0986/4308/files/Cable-Delay-FAQ.pdf https://cdn.shopify.com/s/files/1/0986/4308/files/Cable-Dela... http://www.faculty.ece.vt.edu/swe/lwa/memo/lwa0136.pdf http://www.faculty.ece.vt.edu/swe/lwa/memo/lwa0136.pdf RG58 is your traditional coax copper you'd run with copper and SMA connectors on an above-average scope.
deleted 10y ago
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overlordalex 10y ago
Typically the speed of light in copper/fibre is about 2/3rds of lights speed in a vacuum. Hence the discrepancy.
- samdoidge 10y ago
  Typically the speed of light in copper/fibre is about 2/3rds of lights speed in a vacuum Does light travel through copper?
  - dest 10y ago
    Both light (air, fiber) and electricity (copper) lead to a propagating electromagnetic field.

by prth 10y ago

cmdrfred 10y ago

Is that not the speed of light in a vacuum? I believe its different in different mediums.

jarvist 10y ago
Yes, it's about 2/3 c (speed of light) in a fibre optic (refractive index n=1.44), and about 1/3 c in a copper cable. Air barely slows it down.
- zoren 10y ago
  Do you have a source on the 1/3 c in copper?
  - iheartmemcache 10y ago
    http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.2013.45.html http://www.nature.com/nphoton/journal/v7/n4/full/nphoton.201... Here's a definitive src on .69c for an 'ideal' fibre velocity factor. Here are two sources, both of which have prop. velocities @ around .6c depending on the dialectric. Again ideal. I haven't architected any long-run infrastructure, but 1/3rd sounds pretty right to me. https://cdn.shopify.com/s/files/1/0986/4308/files/Cable-Delay-FAQ.pdf https://cdn.shopify.com/s/files/1/0986/4308/files/Cable-Dela... http://www.faculty.ece.vt.edu/swe/lwa/memo/lwa0136.pdf http://www.faculty.ece.vt.edu/swe/lwa/memo/lwa0136.pdf RG58 is your traditional coax copper you'd run with copper and SMA connectors on an above-average scope.

deleted 10y ago

[deleted]

overlordalex 10y ago

Typically the speed of light in copper/fibre is about 2/3rds of lights speed in a vacuum. Hence the discrepancy.

samdoidge 10y ago
Typically the speed of light in copper/fibre is about 2/3rds of lights speed in a vacuum Does light travel through copper?
- dest 10y ago
  Both light (air, fiber) and electricity (copper) lead to a propagating electromagnetic field.