[SOLVED] RTL8187 wireless network quality decays

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[SOLVED] RTL8187 wireless network quality decays

Postby noah++ on Fri May 18, 2012 1:31 am

Hi,

I am using Mint for the first time on this computer, having just installed the new LMDE RC. I use an Alfa USB b/g adapter, and that adapter uses the RTL8187 kernel driver. It works fine in Windows 7, and seemed to work fine for the brief period I was using Arch Linux last week (heh!). Now in Mint, I am having a problem.

It will work well at startup. Eventually, some websites will start loading slow. Soon after, the same sites will just hang at the "Waiting for reply..." phase in Firefox. That'll be the case for google.com, for instance, even while yahoo.com works fine. But then the speed of loads from yahoo.com will start to decay, too. Before long, the problem cascades across many more sites, until I can't reach anything beyond my router. I have to unplug the USB card and plug it back in. (Just disabling networking or wireless networking from Network Manager didn't help.) Then it's fine again, until another few minutes or hours pass, and the problem starts again.

The problem is not limited to Firefox -- the whole system gets marred -- though the symptoms are easiest to track in Firefox. Also note that connection link quality, as seen from iwconfig, stays consistent. (Accordingly, I guess, I never seem to have trouble reaching my router's admin page.) While I experience this problem, I am able to associate my cell phone to my wireless network and access normally the same sites that I can't reach in Mint.

One possibly important difference I've noticed under Mint is in the pattern of the card's activity LED. Under Windows, it just blinks brightly and sporadically under the network load of my idle computer. Now it's blinking on and off so rapidly that it looks like a continuous, dim light unless you look carefully. It also runs pretty warm now.

Part I of the following mintWifi.py output lists the broken PCI chip I have disabled in BIOS. The rest should pertain to the USB adapter I am actually using.
Code: Select all
-------------------------
* I. scanning WIFI PCI devices...
  -- Intel Corporation Centrino Advanced-N 6200 (rev ff)
      ==> PCI ID = 8086:4239 (rev ff)
-------------------------
* II. querying ndiswrapper...
-------------------------
* III. querying iwconfig...
lo        no wireless extensions.

vboxnet0  no wireless extensions.

eth1      no wireless extensions.

wlan0     IEEE 802.11bg  ESSID:"linksys" 
          Mode:Managed  Frequency:2.437 GHz  Access Point: 00:1A:70:51:FE:3D   
          Bit Rate=54 Mb/s   Tx-Power=20 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=70/70  Signal level=-30 dBm 
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:96   Missed beacon:0

-------------------------
* IV. querying ifconfig...
eth1      Link encap:Ethernet  HWaddr f0:de:f1:2c:fe:05 
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:20 Memory:f2500000-f2520000

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:138 errors:0 dropped:0 overruns:0 frame:0
          TX packets:138 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:11260 (10.9 KiB)  TX bytes:11260 (10.9 KiB)

wlan0     Link encap:Ethernet  HWaddr 00:c0:ca:3e:bb:41 
          inet addr:192.168.1.112  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::2c0:caff:fe3e:bb41/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:203860 errors:0 dropped:0 overruns:0 frame:0
          TX packets:140687 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:287483184 (274.1 MiB)  TX bytes:14538318 (13.8 MiB)

-------------------------
* V. querying DHCP...
Reloading /etc/samba/smb.conf: smbd only.
RTNETLINK answers: File exists
-------------------------
* VI. querying nslookup google.com...
Server:      75.75.75.75
Address:   75.75.75.75#53

Non-authoritative answer:
Name:   google.com
Address: 173.194.33.46
Name:   google.com
Address: 173.194.33.35
Name:   google.com
Address: 173.194.33.34
Name:   google.com
Address: 173.194.33.36
Name:   google.com
Address: 173.194.33.39
Name:   google.com
Address: 173.194.33.40
Name:   google.com
Address: 173.194.33.33
Name:   google.com
Address: 173.194.33.32
Name:   google.com
Address: 173.194.33.41
Name:   google.com
Address: 173.194.33.38
Name:   google.com
Address: 173.194.33.37
Last edited by noah++ on Sun May 20, 2012 11:54 pm, edited 1 time in total.
noah++
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Re: RTL8187 wireless network quality decays

Postby noah++ on Sat May 19, 2012 4:36 pm

I've been observing the interface with Wireshark. When the problem occurs, I see a lot of TCP retransmissions go through, and not much else. I see a series of TCP retransmissions: 1, 2, 3, and 7 seconds apart. I see a series of such series pass, while I see no new objects appear in Firefox.

Any ideas why I'm getting this problem, or how to fix it?
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Re: RTL8187 wireless network quality decays

Postby WharfRat on Sat May 19, 2012 11:56 pm

noah++ ,

Open a terminal and keep an eye on
Code: Select all
 tail -f /var/log/messages

That might help in determining what the problem is.

Good luck :wink:
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Re: RTL8187 wireless network quality decays

Postby noah++ on Sun May 20, 2012 9:41 pm

There's nothing interesting in my messages log, thanks.

I've been calling this a quantum network problem, because it seemed every time I would open Wireshark to observe it, its behavior would change -- the problem would suddenly clear. Now I realize Wireshark is doing more than observing. It switches the adapter into promiscuous mode. Something about that switch nudges it into proper functioning.

I gotta think this is a low-level, driver problem. I only wish I could identify it with enough specificity to make a credible bug report.
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Re: RTL8187 wireless network quality decays

Postby WharfRat on Sun May 20, 2012 10:13 pm

noah++,

Did you happen to stumble across this yet?

https://wiki.archlinux.org/index.php/Rtl8187_wireless

Maybe setting the rate will help :?
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Re: RTL8187 wireless network quality decays

Postby noah++ on Sun May 20, 2012 10:28 pm

Ah, thanks, WharfRat. That looks like exactly what I needed. But right before I got your message, I downloaded and installed the RTL8187L driver direct from Realtek, and it has been working flawlessly. So I'm happy.
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Re: RTL8187 wireless network quality decays

Postby WharfRat on Sun May 20, 2012 11:53 pm

noah++ wrote:Ah, thanks, WharfRat. That looks like exactly what I needed. But right before I got your message, I downloaded and installed the RTL8187L driver direct from Realtek, and it has been working flawlessly. So I'm happy.


That was going to be my next suggestion - glad to hear that you got it going :D
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Actual solution

Postby noah++ on Mon May 28, 2012 5:44 pm

Update: I was not using the new drivers when I thought I was! So, naturally, the problems returned soon after I marked this thread SOLVED. I tried adjusting settings with iwconfig, and it didn't help. My journey to the actual solution (using the newest official kernel drivers) is laid out in this thread.
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