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Re: [A bit OT] Diagnosing home network

On 05/19/2017 10:41 PM, Mark Fletcher wrote:

Hi!  :-)

I have some doubts about the throughput of my home network and I'm
hoping for some advice on tools that might help me diagnose it.

My home network consists of 2 Debian machines, one Jessie and one
Stretch, an LFS mini-ITX machine acting as my firewall, another LFS
laptop that is connected only occasionally, a Windows 8.1 laptop, 3
iPhones of varying ages, 2 iPads, 1 Android tablet device, a couple of
other proprietary tablets and a Buffalo Linkstation that provides most
of the connectivity.

The internet access is via Cable. I run an ethernet cable from the cable
modem to the firewall machine, then from the firewall machine to the
Linkstation's WAN port. The firewall machine's WiFi interface is
disabled (I didn't include its driver when I built the kernel for that
machine). The Jessie box, a phone-to-ethernet device and a NAS are
plugged into the Linkstation wired LAN ports. Everything else connects
to the Linkstation WiFi.

Which model Buffalo LinkStation do you have? I can't find one with more than one LAN port:


The terms 'wifi' and 'wan' do not appear on the Wikipedia page:


The LinkStation offers 2.4GHz and 5GHz
connections, the 2.4GHz is b/g and the 5GHz is ac I believe. Those
devices that can use the 5GHz connection, are, the rest are using the

I have my doubts about cross-LAN throughput. For example, as I write I
am using WinSCP on the Windows 8.1 laptop to copy a movie file from my
Jessie box to the laptop. (The movie concerned is not copyright before
anyone asks). The Jessie box is connected to the LinkStation by wired
ethernet, and the Windows 8.1 laptop by WiFi. I am getting a transfer
rate consistently across the life of the connection of 880KB/s. I'd
expect it to be a lot faster than that. I checked the WinSCP software is
capable of limiting the connection speed, but is set not to.

The laptop is situated here on my desktop, less than 2 feet from the
LinkStation (albet with a computer monitor between them).

Radio devices placed too close can create problems. I put my WiFi access points/ routers high on a wall near the center of my house. All my WiFi devices are 3+ meters away.

Neither laptop
nor Jessie box were doing anything else at the time -- the load on the
Jessie box was essentially zero before the transfer started, rose to 1
while the transfer was going on, then fell back to basically zero when
it finished (monitored using xload).

I'd like to be able to diagnose what's going on here, why the transfer
was so slow. Any recommendations for tools I should research? I am very
willing to read man pages etc, but am a bit lost where to start. Google
gave me a lot of Windows-based stuff which I could look into but I would
prefer to use Linux-based tools if possible.

Pointers to tools I should research -- and even better, links to good
tutorials on those tools if you know any -- would be much appreciated.

I'd start with ifconfig (Debian), ipconfig (Windows), whatever network interface management graphical user intefaces (GUI) they provide, and whatever web user interface (WUI) your wired/WiFi router provides. Try to find out the speed, duplex, etc., of the links between the router and Jesse and the router and Windows. Look for indicators of link layer errors. On Jesse, look at the files in /var/log for clues. On Windows, figure out where error messages go and take a look (Event Viewer?).

A bad Ethernet cable could degrade the connection to 10 Mbps and/or half-duplex.

As you're looking at the GUI/WUI's, copy all of the settings into plain text files, one per interface (yes, this will take a fair amount of typing).

Your router WUI should have a mechanism for backing up and restoring all of the settings to/from a file. Back up the settings.

Pick a benchmark and run it as a baseline. Copying a big file via WinSCP from Jesse to Windows and using a stopwatch is a valid benchmark. Type this information into the text file (cut and paste, if possible). Also consider the reverse direction. Also consider copying Jesse to LinkStation and reverse, and Windows to LinkStation and reverse.

Then, start making changes. Make one change, document it, power cycle the entire network, run all benchmarks, and document them.

Look for settings that can be automatic or manual, but are set to manual. Change them to automatic.

When my laptop is at my SOHO work area, I use it's LAN connection -- with the equipment I have, wired is always faster that WiFi.


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