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Re: [A bit OT] Diagnosing home network

On Sun, May 21, 2017 at 02:18:06PM -0000, Dan Purgert wrote:
> Mark Fletcher wrote:
> >
> > 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.
> Quick google doesn't show any "Linkstation" devices with more than one
> ethernet port (much less wifi).  Do you perhaps mean an "Airstation"?
> Could you provide the model number, so we can look it up?

Thanks everyone for your suggestions. I"m now travelling for business, 
hence the delay in replying. I will check on my return at the end of the 
week and reply.

> > [...]
> > 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.
> 880KB (we'll call it 1 MB) / kilobytes per second is about 8 megabits
> per second (1 byte = 8 bits).  8 mbit is a touch low (but in the
> "range") of what you can expect from 802.11g.  802.11n may also fall
> this low, but generally only when there's interference / poor signal.
> A VERY rough rule of thumb is that on a perfectly clear channel, you can
> expect your throughput to be approximately 1/3 to 1/2 of the "on the
> box" speed (so 802.11g - 54mbit/sec yields roughly 18-24 mbit) for ONE
> device connected to the AP.
> >From there, you have to divide up the available throughput by number of
> clients (i.e. a given wifi client's speed is 1/n, assuming that all
> clients are using the same technology).  So if your wifi was *perfect*
> for 802.11g, and one client got 24 mbit -- 2 clients would average 12
> mbit each, 3 would average 8, and so on.  
> In addition to "your clients", you have to contend with neighbors on the
> same channels (who add to the 1/n throughput troubles).  5 GHz helps
> here, as it's less likely that the clients in your home will see the 5
> GHz signal from your neighbors, even if you are on the same channel.
> > [...]
> >
> > 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.
> iperf would be a solid start.  Run it from one machine to another (e.g.
> the wireless laptop to a wired desktop).  Don't try running it on the
> router / access point / switch (if you have any of those), as iperf can
> be resource intensive, so you "lose" a lot of speed due to their
> processor not being able to keep up with the packet generation.
> Also check your wifi channel usage -- 2.4 GHz should be on channel 1, 6,
> or 11 (if you're somewhere where 13 is allowed, you could try that too).
> If you use any other channel (2-5 or 7-10), you're going to be getting a
> lot of interference (and throughput losses) from your neighbors.
> -- 
> |_|O|_| Registered Linux user #585947
> |_|_|O| Github: https://github.com/dpurgert
> |O|O|O| PGP: 05CA 9A50 3F2E 1335 4DC5  4AEE 8E11 DDF3 1279 A281

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