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Re: Throughput riddle

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On 03/18/2016 09:48 AM, Celejar wrote:
> Hi,
>
> I'm trying to understand the throughput across the different links of
> my little home network, and am perplexed by the measured wireless
> throughput.
>
> The three main devices I'm interested in:
>
> Router: Buffalo WZR-HP-G300NH running OpenWrt (Chaos Calmer 15.05).
> Gigabit WAN and LAN, 802.11bgn wireless.
>
> https://wiki.openwrt.org/toh/buffalo/wzr-hp-g300h
>
> Laptop: Thinkpad T61 running Jessie 8.3. Gigabit ethernet, 802.11abgn
> wireless.
>
> NAS: Seagate GoFlex Net [STAK100] runninng Debian Jessie 8.3.
>
> https://archlinuxarm.org/platforms/armv5/seagate-goflex-net
>
> All throughput measurements taken with iperf (run three times and using
> the median result), unless specified otherwise. These first results are
> with the laptop connected to the router via cat5:
>
> Laptop - NAS:		~874 Mbps.

I use category 5E cables for Gigabit.  Category 5 and category 6 cables 
were not reliable for me.


Perhaps the NAS has an automatic crossover feature on it's Gigabit port. 
  If you do a computer-cable-computer test, you will want a (category 
5E) crossover cable.


Make sure you are using the right cables and that they are known good. 
I own an Ideal LinkMaster cable tester, and it has been worth every penny:

     http://www.amazon.com/Linkmaster-UTP-stp-Cable-Tester/dp/B000LDC3LA


> I suppose this is close enough to the gigabit theoretical max, and there isn't
> any significant bottleneck.
>
> Router - NAS:		~217 Mbps
> Router - laptop:	~198 Mbps
>
> Here the router CPU is apparently the bottleneck (top shows close to
> 100% CPU utilization by iperf for at least part of the 10 second iperf
> runs). I suppose that this is due to the bits needing to be copied out
> of the kernel networking stack into iperf's userspace memory, or
> something like that. I don't understanding why the NAS seems to be
> doing better, but I suppose it could be an artifact of the data.

The numbers are within 10%, so I'd call them the same as far as router 
performance is concerned.


What happens if you connect two Gigabit computers through the router and 
run iperf between the computers?


What happens if you connect one Gigabit computer and one 802.11n 
computer through the router and run iperf between the computers?


What happens if you connect two 802.11n computer through the router and 
run iperf between the computers?


> Here's the part that baffles me - these are with the laptop connected
> to the router wirelessly:
>
> Laptop - router:	~11.8 Mbps
>
> These numbers actually exhibit significant variance, but they're
> generally at least this much, and at most about 15-20 Mbps.
>
> Laptop - NAS:		~14.7 Mbps
>
> Once again, these numbers vary widely, but are in line with the laptop
> - router numbers.

Troubleshooting WiFi is tough.  Location and orientation of antennas is 
critical.  Understand that radio waves with a frequency of 2.4 GHz have 
a wavelength of ~12 cm.  One-quarter wavelength (~1 inch) can change 
everything.  You typically have little control over other WiFi devices 
or other sources of RF interference.  All matter in the universe absorbs 
and re-radiates energy in curious ways, causing constructive/ 
destructive interference patterns throughout space.  So, Murphy's Law is 
certain to strike.


Try repositioning the router. You want the antennas up high, radiating 
horizontally (e.g. stick antennas oriented vertically), and far from all 
other conductive materials -- metal-frame or masonry walls, electrical 
wiring, metallic pipes, metallic ducts, HVAC grilles, metal-film 
windows, metal window screens, televisions, other appliances, etc.. 
Beware of items concealed inside wood-frame walls.  Beware of metallic 
drywall corner bead.


Test the laptop in several locations.  Near-field radiation is more 
complex than far-field, so use a wired connection if the laptop anywhere 
near the router.  A wired Gigabit connection is going to perform better 
than 802.11n even under the best conditions, so consider running 
category 5E cable to other usage locations.  Adjust the router and 
laptop radios for minimum power that gives reliable service.


> But here's the kicker: Ookla's speedtest (run on the laptop with
> speedtest-cli) shows 29.01/5.89 (d/u), and this is fairly consistent.
> I'm paying Comcast for 25/5, and they apparently provision at
> 31.25/6.25, so I'm getting quite close to the theoretical max, even
> when the laptop is connected to the router wirelessly. Additionally,
> various Android phones also get close to the Comcast provisioned max
> when connecting wirelessly to the router.
>
> So the wireless link can apparently push at least 30 Mbps or so, so why
> are my local wireless throughput numbers so much lower?
>
> I was originally using one of the common 1/6/11 channels, and I switched
> to 3 since I saw a lot of other stations on those channels. This may
> have resulted in some improvement, but I'm still stuck locally as
> above. What's the explanation for this - how can I possibly be getting
> much better throughput to servers tens of miles away than to my local
> stations? Does iperf somehow work fundamentally differently from
> speedtest? If so, which is a better representation of actual throughput?

It's not clear if you are doing an apples-to-apples comparison.  Perhaps 
iperf isn't measuring what you think it is.


None of your devices are running the firmware or OS the manufacturer 
intended for it.  Perhaps you should revert the router and/or NAS, and 
test again.


David

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Thread

Throughput riddle Celejar <celejar@gmail.com> - 2016-03-18 17:50 +0100
  Re: Throughput riddle "John L. Ries" <jries@salford-systems.com> - 2016-03-18 19:50 +0100
    Re: Throughput riddle "John L. Ries" <jries@salford-systems.com> - 2016-03-18 20:30 +0100
      Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-18 20:40 +0100
    Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-18 20:40 +0100
  Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-19 02:10 +0100
    Re: Throughput riddle Richard Hector <richard@walnut.gen.nz> - 2016-03-19 02:50 +0100
      Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-19 03:10 +0100
        Re: Throughput riddle Richard Hector <richard@walnut.gen.nz> - 2016-03-19 03:50 +0100
          Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-19 04:50 +0100
          Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-20 14:20 +0100
    Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-20 14:20 +0100
      Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-20 17:40 +0100
        Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-20 19:10 +0100
          Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-20 21:50 +0100
            Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-21 03:20 +0100
              Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-21 06:00 +0100
                Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-22 05:30 +0100
                Re: Throughput riddle David Christensen <dpchrist@holgerdanske.com> - 2016-03-24 02:50 +0100
                Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-24 04:10 +0100
  Re: Throughput riddle arian <debian@semioptimal.net> - 2016-03-20 14:50 +0100
    Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-20 15:50 +0100
      Re: Throughput riddle arian <debian@semioptimal.net> - 2016-03-20 16:30 +0100
        Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-20 18:40 +0100
        Re: Throughput riddle Andrew McGlashan <andrew.mcglashan@affinityvision.com.au> - 2016-03-20 19:50 +0100
  RE: Throughput riddle Bonno Bloksma <b.bloksma@tio.nl> - 2016-03-21 12:50 +0100
    Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-22 05:40 +0100
  Re: Throughput riddle Dan Purgert <dan@djph.net> - 2016-03-21 13:30 +0100
    Re: Throughput riddle Celejar <celejar@gmail.com> - 2016-03-22 05:50 +0100
      Re: Throughput riddle David <david.g_jones@ntlworld.com> - 2016-03-22 11:20 +0100
        RE: Throughput riddle Bonno Bloksma <b.bloksma@tio.nl> - 2016-03-22 13:40 +0100

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