Hi everybody,
I have this curious issue with my wireless card on opensuse 13.1.
I sometimes move large files [backups] from one computer in my network to another, to/from my wireless Opensuse laptop [which I’ll call S] to a Kubuntu desktop [K].
I clearly remember some months ago the average transfer speed was about 10 MBps, and indeed this is the speed I get transferring from K to an older Debian laptop [D] when D is wirelessly connected.
Plus, I think this is the wifi limit bandwidth as transfers K <—> D, when D is wired, reach about 20 MBps.
What I experience is that transfers S <—> {K,D} only reach 1-2 MBps, and I can’t figure out why.
Additional infos:
~$ /sbin/lspci | grep Network
01:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24)
~$ uname -a
Linux linux-yvgl.site 3.11.10-7-desktop #1 SMP PREEMPT Mon Feb 3 09:41:24 UTC 2014 (750023e) x86_64 x86_64 x86_64 GNU/Linux
Could you please help me debug this behaviour?
Thank you in advance 
On 05/17/2014 06:26 AM, massimiliano leoni wrote:
>
> Hi everybody,
> I have this curious issue with my wireless card on opensuse 13.1.
> I sometimes move large files [backups] from one computer in my network
> to another, to/from my wireless Opensuse laptop [which I’ll call S] to a
> Kubuntu desktop [K].
>
> I clearly remember some months ago the average transfer speed was about
> 10 MBps, and indeed this is the speed I get transferring from K to an
> older Debian laptop [D] when D is wirelessly connected.
> Plus, I think this is the wifi limit bandwidth as transfers K <—> D,
> when D is wired, reach about 20 MBps.
>
> What I experience is that transfers S <—> {K,D} only reach 1-2 MBps,
> and I can’t figure out why.
>
> Additional infos:
>
> Code:
> --------------------
> ~$ /sbin/lspci | grep Network
> 01:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24)
> ~$ uname -a
> Linux linux-yvgl.site 3.11.10-7-desktop #1 SMP PREEMPT Mon Feb 3 09:41:24 UTC 2014 (750023e) x86_64 x86_64 x86_64 GNU/Linux
>
> --------------------
>
>
> Could you please help me debug this behaviour?
> Thank you in advance
The first thing to check is the reported connection speed on the wireless link.
The transport is half-duplex, thus the maximum data rate would be 1/2 of the
stated link speed. Do you have a wireless repeater in your network? If so, that
will cut the maximum throughput in half once again. Are machines K and D wired
or wireless? If the latter, their communications with the router will interfere?
How much interference do you have in your neighborhood? Run the command
sudo /usr/sbin/iwlist scan | grep -C2 Encryption
and report the output. Indicate which of the listed ESSID entries is your network.
Hi, thanks for the reply
I have a repeater, but I ran the tests with K, D and S all connected to the main wifi router *.
here’s the output you asked for:
~$ sudo /usr/sbin/iwlist scan | grep -C2 Encryption
root's password:
lo Interface doesn't support scanning.
Frequency:2.462 GHz (Channel 11)
Quality=70/70 Signal level=-34 dBm
Encryption key:on
ESSID:"Vodafone-Raptorista"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
--
Frequency:2.412 GHz (Channel 1)
Quality=48/70 Signal level=-62 dBm
Encryption key:on
ESSID:"Galaxy"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
--
Frequency:2.462 GHz (Channel 11)
Quality=38/70 Signal level=-72 dBm
Encryption key:on
ESSID:"Vodafone-Raptorista"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
where Vodafone-Raptorista is my network, and I think it’s listed once for the wifi router and once for the repeater.
K <—> D goes 10 MBps when D is wireless and S is connected wirelessly as well [they are both on, connected and on the same table, close to the wifi router].
I don’t think it’s a link issue because I ran tests in the very same situations, and S could do just as well before I installed OpenSUSE *.
What do you think?**
On 05/17/2014 11:56 AM, massimiliano leoni wrote:
>
> Hi, thanks for the reply
>
> I have a repeater, but I ran the tests with K, D and S all connected to
> the main wifi router *.
> here’s the output you asked for:
>
> Code:
> --------------------
> ~$ sudo /usr/sbin/iwlist scan | grep -C2 Encryption
> root’s password:
> lo Interface doesn’t support scanning.
>
> Frequency:2.462 GHz (Channel 11)
> Quality=70/70 Signal level=-34 dBm
> Encryption key:on
> ESSID:“Vodafone-Raptorista”
> Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
> –
> Frequency:2.412 GHz (Channel 1)
> Quality=48/70 Signal level=-62 dBm
> Encryption key:on
> ESSID:“Galaxy”
> Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
> –
> Frequency:2.462 GHz (Channel 11)
> Quality=38/70 Signal level=-72 dBm
> Encryption key:on
> ESSID:“Vodafone-Raptorista”
> Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
>
>
> --------------------
>
> where Vodafone-Raptorista is my network, and I think it’s listed once
> for the wifi router and once for the repeater.
> K <—> D goes 10 MBps when D is wireless and S is connected wirelessly
> as well [they are both on, connected and on the same table, close to the
> wifi router].
> I don’t think it’s a link issue because I ran tests in the very same
> situations, and S could do just as well before I installed OpenSUSE *.
>
> What do you think?
It seems I forgot to ask for the iwconfig output from S and D.
I think you have an 802.11g connection with a maximum raw rate of 54 Mbps. The
maximum throughput would be halved for half duplex, and halved again for the
repeater for a maximum of 13.5 Mbps, or 1.7 MBps. Repeaters are expensive in
terms of performance.
**
Ok, here they are.
From S:
~$ /usr/sbin/iwconfig
wlp1s0 IEEE 802.11abgn ESSID:"Vodafone-Raptorista"
Mode:Managed Frequency:2.462 GHz Access Point: 00:24:89:9A:02:20
Bit Rate=65 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=65/70 Signal level=-45 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:6008 Invalid misc:1932 Missed beacon:0
From D:
wlan0 IEEE 802.11abgn ESSID:"Vodafone-Raptorista"
Mode:Managed Frequency:2.462 GHz Access Point: 00:24:89:9A:02:20
Bit Rate=72.2 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=70/70 Signal level=-35 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:46 Missed beacon:0
My router is set to work in 802.11b/g/n mode.
I understand the calculation, yet this doesn’t explain why performances are so different on different machines, right?
I mean, this really seems to be a machine-dependent issue.
On 05/18/2014 05:06 AM, massimiliano leoni wrote:
>
> Ok, here they are.
> From S:
>
> Code:
> --------------------
> ~$ /usr/sbin/iwconfig
> wlp1s0 IEEE 802.11abgn ESSID:“Vodafone-Raptorista”
> Mode:Managed Frequency:2.462 GHz Access Point: 00:24:89:9A:02:20
> Bit Rate=65 Mb/s Tx-Power=15 dBm
> Retry long limit:7 RTS thr:off Fragment thr:off
> Power Management:off
> Link Quality=65/70 Signal level=-45 dBm
> Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
> Tx excessive retries:6008 Invalid misc:1932 Missed beacon:0
>
> --------------------
>
>
> From D:
>
> Code:
> --------------------
> wlan0 IEEE 802.11abgn ESSID:“Vodafone-Raptorista”
> Mode:Managed Frequency:2.462 GHz Access Point: 00:24:89:9A:02:20
> Bit Rate=72.2 Mb/s Tx-Power=15 dBm
> Retry long limit:7 RTS thr:off Fragment thr:off
> Encryption key:off
> Power Management:off
> Link Quality=70/70 Signal level=-35 dBm
> Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
> Tx excessive retries:0 Invalid misc:46 Missed beacon:0
>
> --------------------
>
>
> My router is set to work in 802.11b/g/n mode.
>
> I understand the calculation, yet this doesn’t explain why performances
> are so different on different machines, right?
> I mean, this really seems to be a machine-dependent issue.
Check the differences between S and D. First of all, the reported signal is
better by 10 dBm for machine D. That allows it to connect at 72.2 Mbps and it
should get better performance; however, 10 MBps is not possible. If you formerly
connected at 150 Mbps and were not using the repeater, that would get close to
10 MBps. At 72.2 and without the repeater, the max throughput would be 4.1 MBps.
You are also getting excessive retries on S. Yes, it is a machine-dependent
issue, but I doubt that it has anything to do with differences between Debian
and openSUSE.
What is the wireless device in machine D?
Yes, your calculation is correct as at the moment D is connected with a bitrate of 150/135 Mbps, signal level = -39dBm and transfers go at 10-11 MBps, whereas S reports a bitrate of 90 Mbps, signal level = -52dBm and transfers occur at just 1.5 MBps [it starts at about 5-6 MBps and then decreases to steady 1-2 MBps].
If transfer rates are linear, than since 90 is slightly more than half of 150, S should transfer at about 5-6 MBps, which is the initial transfer rate.
On D,
~$ lspci
04:00.0 Network controller: Intel Corporation WiFi Link 5100
So I guess now the question is “why does S have much worse statistics?”.
Could it be a kernel issue? Should I try with another kernel, or booting a live distro with another kernel and repeat the test?
Or maybe is it related to some odd internal mechanism of openSUSE, such as a firewall or a power management that limits the actual bandwidth?
On 05/18/2014 10:56 AM, massimiliano leoni wrote:
>
> Yes, your calculation is correct as at the moment D is connected with a
> bitrate of 150/135 Mbps, signal level = -39dBm and transfers go at 10-11
> MBps, whereas S reports a bitrate of 90 Mbps, signal level = -52dBm and
> transfers occur at just 1.5 MBps [it starts at about 5-6 MBps and then
> decreases to steady 1-2 MBps].
> If transfer rates are linear, than since 90 is slightly more than half
> of 150, S should transfer at about 5-6 MBps, which is the initial
> transfer rate.
>
> On D,
>
> Code:
> --------------------
>
> ~$ lspci
> 04:00.0 Network controller: Intel Corporation WiFi Link 5100
> --------------------
>
>
> So I guess now the question is “why does S have much worse statistics?”.
> Could it be a kernel issue? Should I try with another kernel, or booting
> a live distro with another kernel and repeat the test?
> Or maybe is it related to some odd internal mechanism of openSUSE, such
> as a firewall or a power management that limits the actual bandwidth?
It could be a driver issue, and you should certainly try other kernels. Any
other differences between openSUSE and Debian are so minor as to have a much
lesser effect than what you are seeing. Wifi power management is handled by the
driver, not the user code.
The rate degrades with time because the rate at which the link is stable for
small packets cannot be sustained by S under heavy pressure.