How latency kills overseas download speeds in South Africa

hj007

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So what's the solution? I remember during the days of 56k modems we were told it can't go faster because of Shannon's law, so the tech needed to change.
Perhaps we need to go faster than the speed of light? the speed of darkness! - with humble reference to Neverending Story part 2.
 

Jan

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So what's the solution?
You can go with an un-ACKed protocol, like UDP, or reduce the packet loss on the line. Without packet loss you can basically increase the TCP Receive Window to whatever you want (current max is 1GB) and get tens of gigabits of throughput.
 

sloe-joe

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Petec

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Great article.

Also, this is why a lot of our local online gamers are crying, because they are farting against thunder if they want to competitively duke it out against overseas players/clans.
 

Drifter

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You can go with an un-ACKed protocol, like UDP, or reduce the packet loss on the line. Without packet loss you can basically increase the TCP Receive Window to whatever you want (current max is 1GB) and get tens of gigabits of throughput.
Is that something that I can control, or will I be dependent on my ISP?
 

waylander

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Great article.

Also, this is why a lot of our local online gamers are crying, because they are farting against thunder if they want to competitively duke it out against overseas players/clans.
Games almost always use UDP, so no.
 

Moosedrool

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So what's the solution? I remember during the days of 56k modems we were told it can't go faster because of Shannon's law, so the tech needed to change.
Perhaps we need to go faster than the speed of light? the speed of darkness! - with humble reference to Neverending Story part 2.
Researchers are working on hollow fibre because optic fibre slows down light by around 31%. Hollow fibre is only 3% slower.

Another thing is the increase of processing speed also has a major effect. Remember packets gets processed before transmitted etc. So faster hardware also increase roundtrip times. Though people should expect a 10ms latency to New York.
 

Murmaider

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If you use inverse multiplexing (break the file being downloaded into say 10 segments and have 10 parallel connections pulling down each segment) you can ramp up your download speeds

In linux this is easily done with lftp:

# lftp -e 'pget -n 10 http://<url>'
 
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Murmaider

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Without packet loss you can basically increase the TCP Receive Window to whatever you want (current max is 1GB) and get tens of gigabits of throughput.
Sort of, but not so much on the internet side.
You would have to enable Jumbo Frames by increasing the MTU to 9000 (like you would with SAN traffic).
The problem is that 99% of the internet does not support jumbo frames and you would actually cause more packet loss by doing this.

You also can't account for the TCP window size across all hops on the network, at some point the traffic is going to be broken down into smaller chunks. So while your router might have a larger size, the sending router may not.
 
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hj007

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Interesting solutions. Mine was going to just be to drill a hole through the centre of the earth and shorten the distance from going on the sphere's surface to going through the diameter... but doing multiple packets sounds good too.
 

quovadis

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Those figures are based on a single thread download.

If you use inverse multiplexing (break the file being downloaded into say 10 segments and have 10 parallel connections pulling down each segment) you can ramp up the speed past these values.

In linux this is easily done with lftp:

# lftp -e 'pget -n 10 http://<url>'
Errrr? No.
 

Murmaider

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Errrr? No.
Code:
# lftp -e 'pget -n 1 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso'
865075200 bytes transferred in 111 seconds (7.41 MiB/s)

# rm -rf ubuntu-16.04.3-server-amd64.iso

# lftp -e 'pget -n 10 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso'
865075200 bytes transferred in 45 seconds (18.20 MiB/s)
 

hj007

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Code:
# lftp -e 'pget -n 1 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso'
865075200 bytes transferred in 111 seconds (7.41 MiB/s)

# rm -rf ubuntu-16.04.3-server-amd64.iso

# lftp -e 'pget -n 10 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso'
865075200 bytes transferred in 45 seconds (18.20 MiB/s)
are we not speaking cross-purposes here?.. this is to increase the download speed to get past the max-implied mbps referred to by Jan, but the discussion started being about reducing individual packet latency, for which this is not a solution...
 

Murmaider

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are we not speaking cross-purposes here?.. this is to increase the download speed to get past the max-implied mbps referred to by Jan, but the discussion started being about reducing individual packet latency, for which this is not a solution...
Yeah I think I am, looking back at my post.
I was responding to question of how do you increase your download speed, I should probably edit my original post.

EDIT
In saying that though, they saying the maximum speed that can be obtained on a 1G connection at 300ms latency is 195mbps
I am saying that this is not entirely true.

If I launch 2 simitanious downloads each using 16 threads in 16 segments:

# aria2c -x 16 -s 16 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso

Download Results:
gid |stat|avg speed |path/URI
======+====+===========+=======================================================
f0d62f|OK | 20MiB/s|/root/ubuntu-16.04.3-server-amd64.iso

and

~/tmp# aria2c -x 16 -s 16 http://mirror.pnl.gov/releases/16.04/ubuntu-16.04.3-server-amd64.iso


Download Results:
gid |stat|avg speed |path/URI
======+====+===========+=======================================================
1d61cd|OK | 13MiB/s|/root/tmp/ubuntu-16.04.3-server-amd64.iso

This gives 33MB/sec or 264mbps which is above the 195mbps in the article.
This was done on a server with a 1Gbit connection.


Which is reflected on the 2 minute traffic graph:

graph.png

Just incase you wondering about the latency:
# ping mirror.pnl.gov
PING mirror.pnl.gov (192.101.102.2) 56(84) bytes of data.
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=1 ttl=51 time=311 ms
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=2 ttl=51 time=310 ms
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=3 ttl=51 time=310 ms
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=4 ttl=51 time=310 ms
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=5 ttl=51 time=311 ms
64 bytes from fedoramirror.pnl.gov (192.101.102.2): icmp_seq=6 ttl=51 time=310 ms
 
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mercury12

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So if you stream content from international servers is there any point in increasing your download speed,in order to get better performance?
 

Sinbad

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Sort of, but not so much on the internet side.
You would have to enable Jumbo Frames by increasing the MTU to 9000 (like you would with SAN traffic).
The problem is that 99% of the internet does not support jumbo frames and you would actually cause more packet loss by doing this.

You also can't account for the TCP window size across all hops on the network, at some point the traffic is going to be broken down into smaller chunks. So while your router might have a larger size, the sending router may not.
Window size is not relevant to routers. It's relevant to the source and destination only.
 
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