Learning about the internet

Dustin Melancon DMelancon at venyu.com
Mon Nov 3 22:25:29 UTC 2014


Hey Paige,

That¹s going to be extremely common when traversing transatlantic cable.
Hopefully I can help explain.

Most of your latency comes from simple speed of light limitations through
optical fiber (~35% slower than vacuum) combined with the fact that the
fiber must take a somewhat indirect path to your destination.
Additionally, a small percentage of latency will be added for all of the
switching/routing/regeneration nodes that must convert the fiber signals
from optical back to electrical (for processing / regeneration) then back
to optical. In your case, your packets are taking the following path:

Los Angeles (Arp Networks to Level3 to Cogent) -> Houston -> Atlanta ->
Washington DC -> Paris -> Frankfurt -> Munich -> Austria -> Bulgaria ->
Athens -> Hellas

Essentially it¹s taking 60ms round trip to get to DC, then another 95ms to
get to Paris, plus 60ms to get to Hellas, then another 20ms to traverse
the local ³last mile² access network to your destination.

If you had a *direct* fiber from LAX to Hellas Greece, that would be
~22,000km of round trip fiber. Working out some simple math, that would
yield approximately 110ms of round trip latency no matter how much
bandwidth you have. Now, add in all of the indirect fiber paths through
major cities plus all of the routing/switching hops and you can see why
you¹re getting 200ms+ latency.

Hope this helps!


Thanks,
Dustin Melancon, Sr. Network Engineer
225-214-3864 Direct ::: 866-978-3698 Toll-Free
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On 11/3/14, 3:15 PM, "Paige Thompson" <paigeadele at gmail.com> wrote:

>Hi,
>
>I was just reading about transatlantic cabling in some hopes that I
>would be able to find an answer as to why the latency between here in
>greece and Los Angeles is roughly ~250ms. This seems to be a really
>common thing, although I'd like to understand why and the articles on
>transatlantic cabling as near as I can tell indicate that I am getting
>screwed if anything (not enough information?)
>
>(from Los Angeles to my house)
>Konsole output
>
>Konsole output
>gw~ #mtr --report-wide xxxxxxxxxxxxxxx.access.hol.gr
>Start: Mon Nov  3 13:04:02 2014
>HOST: gw                                    Loss%   Snt   Last   Avg
> Best  Wrst StDev
> 1.|-- 208.79.92.65                          10.0%    10    1.5   3.6
>  1.2  15.5   4.6
> 2.|-- s7.lax.arpnetworks.com                 0.0%    10    0.8  10.9
>  0.8  54.2  20.7
> 3.|-- vlan953.car2.LosAngeles1.Level3.net   30.0%    10   10.5  10.3
> 10.1  10.8   0.0
> 4.|-- ae-27-27.edge6.LosAngeles1.Level3.net 30.0%    10   21.8  16.2
>  8.6  47.6  14.7
> 5.|-- ae-4-90.edge1.LosAngeles6.Level3.net  80.0%    10    9.0   8.9
>  8.7   9.0   0.0
> 6.|-- be3036.ccr21.lax04.atlas.cogentco.com 10.0%    10    1.7   2.1
>  1.4   4.3   0.7
> 7.|-- be2076.mpd22.lax01.atlas.cogentco.com 10.0%    10    1.6   1.9
>  1.6   3.2   0.0
> 8.|-- be2068.ccr22.iah01.atlas.cogentco.com  0.0%    10   37.7  37.7
> 37.3  39.0   0.3
> 9.|-- be2173.ccr42.atl01.atlas.cogentco.com  0.0%    10   51.6  52.4
> 51.5  57.5   1.7
>10.|-- be2171.mpd22.dca01.atlas.cogentco.com  0.0%    10   62.6  62.7
> 62.4  63.3   0.0
>11.|-- be2112.ccr41.iad02.atlas.cogentco.com  0.0%    10  155.5 155.8
>155.5 156.1   0.0
>12.|-- be2268.ccr42.par01.atlas.cogentco.com  0.0%    10  152.6 152.7
>152.5 153.5   0.0
>13.|-- be2278.ccr42.fra03.atlas.cogentco.com  0.0%    10  155.3 155.4
>155.1 155.5   0.0
>14.|-- be2229.ccr22.muc01.atlas.cogentco.com  0.0%    10  161.2 161.1
>160.9 161.3   0.0
>15.|-- be2223.ccr21.vie01.atlas.cogentco.com  0.0%    10  164.9 165.1
>164.9 165.2   0.0
>16.|-- be2046.ccr21.sof02.atlas.cogentco.com  0.0%    10  189.5 189.4
>189.3 189.9   0.0
>17.|-- be2118.rcr11.ath01.atlas.cogentco.com  0.0%    10  197.5 197.6
>197.4 197.7   0.0
>18.|-- 149.11.120.38                          0.0%    10  202.7 202.2
>200.3 204.2   1.4
>19.|-- 62.38.97.113                          80.0%    10  208.5 209.8
>208.5 211.1   1.7
>20.|-- gigaeth04-13.krs00.ar.hol.gr          60.0%    10  211.3 213.0
>211.2 218.2   3.4
>21.|-- ???                                   100.0    10    0.0   0.0
>  0.0   0.0   0.0
>22.|-- xxxxxxxxxxxxxxxx.access.hol.gr         40.0%    10  231.3 231.4
>231.2 231.7   0.0
>gw~ #
>
>
>
>And to be more clear: I am hoping to learn about the complex trials that
>these packets are going through and how time is being lost if the
>latency across the transatlantic cable is really capable of less the
>60ms of latency? Sure over capacity (3.2Tbits/s wow jeez) is one answer,
>but what are some other possibilities for loss of time?
>
>Also it seems with my VPN (OpenVPN) tunnel I get the most reliable
>connection (fewest drops) with:
>
>Konsole output
>mssfix 576
>fragment 576
>
>Although this could be a false positive as it only *seems* to help with
>reliability since I changed it. Even then but less often than before I
>still experience drops but I want to believe that's possibly due to my
>ISP at that point.. but assuming my ISP was absolutely perfect and never
>a problem what else there to consider?
>
>Any and all insight is appreciated.
>
>-Paige
>
>


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