Troubleshooting the network connection speed

[Steven Stern]

On 08/13/2013 07:09 AM, Marko Vojinovic 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)
> 
> 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.
> 
> 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.
> 
> 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.
> 
> 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?
> 
> 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. :-)
> 

Check with your ISP -- there may be a way to isolate the transfer to
your connection device. For example, I use RCN Cable and there's a way
to do a speed test from within the cable modem. I use this to figure out
if there are speed issues with my connection or my internal network.

For the RCN customers out there, the format is
http://xx.speedtest.rcn.net/, where xx is the two character abbreviation
of your state (e.g., http://il.speedtest.rcn.net/).  It also shows
signal and noise levels on the connection (which can indicate corroded
cable connecttions, etc.)

-- 
-- Steve