6 ms·

Also a couple of things to note: 1. Submarine cables can't go in a straight line, since they've got to, you know, go down to the bottom of the ocean. (Which,

Also a couple of things to note: 1. Submarine cables can't go in a straight line, since they've got to, you know, go down to the bottom of the ocean. (Which, you may have heard, is quite deep.) Also, a cable with a length of several thousand miles tends to have some slack. 2. Your packets may take a very curvy route from one city to another, even when they're not geographically that distant. This may be because your ISP is bad (and has poor/limited routes), geographic or geopolitical concerns, or just because of the way the Internet infrastructure is built. On the US's west coast, I often experience latencies 60%+ slower than the theoretical minimum when accessing servers in the central or eastern US. (e.g. SF -> Des Moines, IA at 70ms).

danaliv 6y ago
For point 1, is the depth of the ocean significant compared to the distances traversed? My back-of-the-envelope math suggests it’s less than half a percent for a cable from New York to England. (6 miles down + 6 miles up, divided by rough great circle distance of 2600 nautical miles.) I would think a bigger factor would be that the cables (IIRC) don't go in straight lines (which you did allude to).
- sandworm101 6y ago
  Correct. The ocean bottom is relatively flat once away from the continents. Also, the submarine cable actually has a very slight advantage over a surface cable as at several thousand feet below it is following a slightly smaller radius curve. I'm waiting for the HFT firm to bore a literally strait hole between London and New York. Then we know that HFT has gone too far.
  - foota 6y ago
    Think of the shipping opportunities!
  - chokeartist 6y ago
    > I'm waiting for the HFT firm to bore a literally strait hole between London and New York. Then we know that HFT has gone too far. No need. They have Starlink now (or soon).
  - firethief 6y ago
    Surely it would be easier to use neutrinos?
  - bigiain 6y ago
    Like the Alameda Weehawken Burrito Tunnel? (Since somebody else has already mentioned the pinboardiness of these comments... https://idlewords.com/2007/04/the_alameda_weehawken_burrito_tunnel.htm https://idlewords.com/2007/04/the_alameda_weehawken_burrito_... )
    - lxgr 6y ago
      Wait what?
    - TeMPOraL 6y ago
      This is fiction? Right? Please tell me there is no actual tunnel that transports burritos from west to east coast of the United States.
      - bigiain 6y ago
        You've never eaten a piping hot El Farolito burrito in the snow in Central Park? You haven't lived!!!
  - SignalNotSecure 6y ago
    I thought quantum entanglement solved the HFT use case
    - lxgr 6y ago
      Quantum entanglement does not allow FTL communications (which would break causality).
      - tecleandor 6y ago
        Ah, but you don't need FTL, you just need FTF (Faster Than Fiber) :D
  - lxgr 6y ago
    We're not too far off – HFT is already digging tunnels [0] and building microwave relay paths [1]. [0] https://www.nytimes.com/2014/04/14/opinion/krugman-three-expensive-milliseconds.html https://www.nytimes.com/2014/04/14/opinion/krugman-three-exp... [1] https://www.amsterdamtrader.com/2014/09/hft-in-my-backyard.html https://www.amsterdamtrader.com/2014/09/hft-in-my-backyard.h...
- jholman 6y ago
  Agreed. As we probably all know, the earth is smoother than a regulation billiard ball wrapped in 1000-grit sandpaper.
pbhjpbhj 6y ago
Debugging high ping at home once mtr (or similar, I think it was a graphical tool) showed the first 5 or 6 hops all in the ISPs network and taking about ⅔ of the time; going from UK to USA and then leaving their network in Amsterdam IIRC only to terminate at another data-center in UK. Pretty crazy. Ha, it only just struck me that could have been an NSA-type routing issue!?!
- hinkley 6y ago
  That reminds me of the bug in Google Maps where a route from southern Sweden to Norway suggested driving through the Chunnel and taking a car ferry across from Scotland.
- WrtCdEvrydy 6y ago
  The internet is supposed to be self-healing but the ISP routes are sometimes hella-dumb. More than once I have seen a traceroute that takes you from Miami, down to Argentina and then back up to Cali.
cycomanic 6y ago
It's important to remember you packets are in the network layer (probably when you send them even transport or application? I'm not so familiar with the higher layers in the OSI stack). So you are still quite a bit removed from from the physical layers. Your packet will likely go through several electrical-to-optical and optical-to-electrical conversions, probably there will be some electric switches, plus multiplexers, all of which contain buffers. Then there is forward error correction in the physical layer which also requires buffers etc.. And you're obviously right that for many reasons the "straight path" might not be the path that is being taken, or even the fastest one. Bottom line, estimating ping time from geographic distance is a very rough estimate. However, the longer the distance through an uninterrupted link (i.e. a submarine cable) the better your estimate, i.e. if you sit at in a google datacentre which is directly connected to their fibre backbone and do a ping to machine in a similar data centre on a different country you will get quite close numbers I imagine (I don't work for google). On the other hand if you sit somewhere in the mid-west at home and ping a server in e.g. NY or LA, not so much.

danaliv 6y ago

For point 1, is the depth of the ocean significant compared to the distances traversed? My back-of-the-envelope math suggests it’s less than half a percent for a cable from New York to England. (6 miles down + 6 miles up, divided by rough great circle distance of 2600 nautical miles.) I would think a bigger factor would be that the cables (IIRC) don't go in straight lines (which you did allude to).

sandworm101 6y ago
Correct. The ocean bottom is relatively flat once away from the continents. Also, the submarine cable actually has a very slight advantage over a surface cable as at several thousand feet below it is following a slightly smaller radius curve. I'm waiting for the HFT firm to bore a literally strait hole between London and New York. Then we know that HFT has gone too far.
- foota 6y ago
  Think of the shipping opportunities!
- chokeartist 6y ago
  > I'm waiting for the HFT firm to bore a literally strait hole between London and New York. Then we know that HFT has gone too far. No need. They have Starlink now (or soon).
- firethief 6y ago
  Surely it would be easier to use neutrinos?
- bigiain 6y ago
  Like the Alameda Weehawken Burrito Tunnel? (Since somebody else has already mentioned the pinboardiness of these comments... https://idlewords.com/2007/04/the_alameda_weehawken_burrito_tunnel.htm https://idlewords.com/2007/04/the_alameda_weehawken_burrito_... )
  - lxgr 6y ago
    Wait what?
  - TeMPOraL 6y ago
    This is fiction? Right? Please tell me there is no actual tunnel that transports burritos from west to east coast of the United States.
    - bigiain 6y ago
      You've never eaten a piping hot El Farolito burrito in the snow in Central Park? You haven't lived!!!
- SignalNotSecure 6y ago
  I thought quantum entanglement solved the HFT use case
  - lxgr 6y ago
    Quantum entanglement does not allow FTL communications (which would break causality).
    - tecleandor 6y ago
      Ah, but you don't need FTL, you just need FTF (Faster Than Fiber) :D
- lxgr 6y ago
  We're not too far off – HFT is already digging tunnels [0] and building microwave relay paths [1]. [0] https://www.nytimes.com/2014/04/14/opinion/krugman-three-expensive-milliseconds.html https://www.nytimes.com/2014/04/14/opinion/krugman-three-exp... [1] https://www.amsterdamtrader.com/2014/09/hft-in-my-backyard.html https://www.amsterdamtrader.com/2014/09/hft-in-my-backyard.h...
jholman 6y ago
Agreed. As we probably all know, the earth is smoother than a regulation billiard ball wrapped in 1000-grit sandpaper.

pbhjpbhj 6y ago

Debugging high ping at home once mtr (or similar, I think it was a graphical tool) showed the first 5 or 6 hops all in the ISPs network and taking about ⅔ of the time; going from UK to USA and then leaving their network in Amsterdam IIRC only to terminate at another data-center in UK. Pretty crazy. Ha, it only just struck me that could have been an NSA-type routing issue!?!

hinkley 6y ago
That reminds me of the bug in Google Maps where a route from southern Sweden to Norway suggested driving through the Chunnel and taking a car ferry across from Scotland.
WrtCdEvrydy 6y ago
The internet is supposed to be self-healing but the ISP routes are sometimes hella-dumb. More than once I have seen a traceroute that takes you from Miami, down to Argentina and then back up to Cali.

cycomanic 6y ago

It's important to remember you packets are in the network layer (probably when you send them even transport or application? I'm not so familiar with the higher layers in the OSI stack). So you are still quite a bit removed from from the physical layers. Your packet will likely go through several electrical-to-optical and optical-to-electrical conversions, probably there will be some electric switches, plus multiplexers, all of which contain buffers. Then there is forward error correction in the physical layer which also requires buffers etc.. And you're obviously right that for many reasons the "straight path" might not be the path that is being taken, or even the fastest one. Bottom line, estimating ping time from geographic distance is a very rough estimate. However, the longer the distance through an uninterrupted link (i.e. a submarine cable) the better your estimate, i.e. if you sit at in a google datacentre which is directly connected to their fibre backbone and do a ping to machine in a similar data centre on a different country you will get quite close numbers I imagine (I don't work for google). On the other hand if you sit somewhere in the mid-west at home and ping a server in e.g. NY or LA, not so much.