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cnst
Asked: 2013-07-26 08:39:13 +0800 CST

Testing network connectivity on a server with Gigabit Ethernet

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I have a box with Gigabit Ethernet, and I'm unable to get past about 200Mbps or 250Mbps in my download tests.

I do the tests like this:

% wget -6 -O /dev/null --progress=dot:mega http://proof.ovh.ca/files/1Gb.dat
--2013-07-25 12:32:08--  http://proof.ovh.ca/files/1Gb.dat
Resolving proof.ovh.ca (proof.ovh.ca)... 2607:5300:60:273a::1
Connecting to proof.ovh.ca (proof.ovh.ca)|2607:5300:60:273a::1|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 125000000 (119M) [application/x-ns-proxy-autoconfig]
Saving to: ‘/dev/null’

     0K ........ ........ ........ ........ ........ ........  2% 5.63M 21s
  3072K ........ ........ ........ ........ ........ ........  5% 13.4M 14s
  6144K ........ ........ ........ ........ ........ ........  7% 15.8M 12s
  9216K ........ ........ ........ ........ ........ ........ 10% 19.7M 10s
 12288K ........ ........ ........ ........ ........ ........ 12% 18.1M 9s
 15360K ........ ........ ........ ........ ........ ........ 15% 19.4M 8s
 18432K ........ ........ ........ ........ ........ ........ 17% 20.1M 7s

With the constraint that I only control one server which I want to test, and not the sites against which I want to perform the tests, how do I do a fair test?

Basically, is there some tool that would let me download a 100MB file in several simultaneous TCP streams over HTTP?

Or download several files at once in one go?

gigabit-ethernet

3 Answers

  1. Aria2 is command line tool similar to wget that supports multiple simultaneous downloads over http , bittorent, ftp etc.

    aria2c -d /dev -o null  --allow-overwrite=true -x 15 url  --file-allocation=none

    Download file with 15 connections to /dev/null.

    --allow-overwrite prevents aria from trying to rename /dev/nulll.

    I prefer not to start allocating space before the download since it takes time for the download to start

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  2. You will be limited to less then the speed of the slowest link. You could have a 10Gig connection, but if your internet connection is Dialup, you are going to be waiting. Even on a LAN that can support 1GB end to end, you may see a bottlneck with the read speeds of the source server or the write speeds of the destination server.

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  3. There are many factors that contribute to this:

    For one thing, you're downloading over the Internet. Let's assume you truly have a gigabit down connection at your disposal:

    TCP overhead can eat anywhere from 5-10% of your bandwidth - for simplicity's sake let's say 10%. So you're down to 900Mbits/s.

    Remote server load is a major factor and you can't control or see it. Many servers can easily pull 200 MB/s read times, but under load it can push the speeds down.

    Routing is a factor in speed too. If your route is saturated, speed will suffer.

    And finally ...do you really have a gigabit connection to the Internet, or is it just your port speed? Speeds are limited by the slowest link that you cross. Also, if you have a hosted server with a gigabit link, these are often shared by other clients and you don't get a dedicated gigabit link to begin with.

    Edit: The reason I didn't recommend a tool is because they're a google search away and there's tons.

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