Troubleshooting the network connection speed

[Dale Dellutri]

On Tue, Aug 13, 2013 at 7:09 AM, Marko Vojinovic <vvmarko at gmail.com> wrote:

>
> Hi folks! :-)
>
> Before I go complain to my ISP, I'd like to hear if anyone can give me
> an idea what is going on with my networks... :-)
>
> I have two machines, with following link properties:
>
>  local --- 20Mbps/2Mbps (GSM wireless)
>  remote --- 100Mbps/100Mbps (100Mbit LAN connected to optical uplink)
>

I assume that the local is connected to a cable service ISP.
Cable service dpeeds are generally not guaranteed, and depend on other
users on the same cable segment, whom you know nothing about.

Perhaps you would get better download speeds from remote to local
if you tried it after local midnight.


> The remote machine is in another country, cca 2000 km away. It is
> connected to a 10Gbit optical link, but only through a 100Mbps switch,
> so that caps the bandwidth.
>
> When transferring large files via wget from remote to local, the
> maximum bandwidth that I get is 2Mbps. It *used to be* 20Mbps (couple
> of days ago). Occasionally it drops down to 300Kbps (it just happened
> as I write this), but after several minutes it gets back up to 2Mbps.
>

If it "used to be" 20 Mbps, perhaps a new user has come online on
your cable segment.


> But it doesn't want to get back up to 20Mbps, which is the max download
> throughput for the local machine.
>
> To test the local link, I opened 15-20 random youtube links
> simultaneously in Firefox. It easily capped the full 20Mbps, so the
> local link apparently works as advertised.
>

Here you are doing multiple downloads, not just one.  I don't know
whether that makes a difference or not.


> Another test of the local link --- I went to
>
>   http://fedoraproject.org/get-fedora
>
> and clicked the big blue "download now" button, to download the Live
> Desktop .iso --- the download manager in Firefox says it will complete
> it in 17 hours, since it is downloading at 15 KBps (i.e. 150 Kbps).
> This is of course ridiculously slow, for a 20Mbps link.
>

This is a better comparison: one download stream.


> All speed numbers are consistently reported by jnettop, KDE network
> widget, Firefox download manager and wget. If you suggest some other
> tool to measure the throughput, I'll try it out too.
>
> The remote machine appears to work ok --- I have downloaded and
> uploaded (elsewhere) all sorts of things, and it consistently works at
> 100Mbps up/down. Downloaded Fedora DVD iso in a couple of minutes. I
> can seed torrents from it at 100Mbps no problem (this is currently off
> because I'm trying to pull something to the local machine).
>
> So I believe something is wrong with my local link, but don't know
> exactly what --- youtube works, but other things don't.
>
> Any ideas how to troubleshoot this?
>
> Also, any ideas what to tell to my ISP?
>

Ask them about service speed guarantees.  They might have a guaranteed
speed service for a higher price.


> I could ask them to look into it, but they just might open a bunch of
> youtube links, verify that the link works, and blame the remote machine.
>
> Any suggestions appreciated.
>
> TIA, :-)
> Marko
>
> P.S. Before anyone asks --- I *do* know the difference between bits and
> bytes, Mbps and MBps, etc. I was careful to provide you with a
> case-sensitive units, and I know what I'm talking about. :-)
>

-- 
Dale Dellutri
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