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Old 06-18-2004, 07:16 PM   #1
phantompgr
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Location: South Wales, UK
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Wireless Card Connecting / Disconnecting (11 2 11 2)


Hi guys,

Wonder if any of you may shed some light on my rather curious problem....

I am running Mandrake 9.2 on an IBM Thinkpad complete with internal Prism2 Wireless network card. I have a Belkin wirless router in my computer room that interacts with the other machines on my network. This setup has been a great success with me and said laptop able to sit comfortably downstairs while accessing the internet and crucially VNC (I have VNC servers on both a Linux box and W2K box).

As you can imagine VNC has always been a little slow but was always workable, however recently it has become unuseable. When opening a TightVNC connection on my laptop (even when sitting in computer room adjacent to router), the following appears in the syslog:

Jun 15 22:45:02 Eagle kernel: eth1: New link status: Disconnected (0002)
Jun 15 22:45:03 Eagle kernel: eth1: New link status: Connected (0001)
Jun 15 22:45:09 Eagle kernel: eth1: New link status: Disconnected (0002)
Jun 15 22:45:10 Eagle kernel: eth1: New link status: Connected (0001)
Jun 15 22:45:34 Eagle ....

and the following occurs with repetitive calls to iwconfig:
eth1 IEEE 802.11-DS ESSID:"BUZZARD" Nickname:"Eagle.BIRDS-OF-PREY"
Mode:Managed Frequency:2.442GHz Access Point: 00:30:BD:62:67:B0
Bit Rate=11Mb/s Tx-Power=15 dBm Sensitivity:1/242700000
Retry min limit:7 RTS thr=250 B Fragment thr:2347 B
Link Quality:63/1 Signal level:-29 dBm Noise level:-92 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:276
Tx excessive retries:277 Invalid misc:0 Missed beacon:0

eth1 IEEE 802.11-DS ESSID:"BUZZARD" Nickname:"Eagle.BIRDS-OF-PREY"
Mode:Managed Frequency:2.442GHz Access Point: 00:30:BD:62:67:B0
Bit Rate=2Mb/s Tx-Power=15 dBm Sensitivity:1/242700000
Retry min limit:7 RTS thr=250 B Fragment thr:2347 B
Link Quality:62/1 Signal level:-29 dBm Noise level:-91 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:277
Tx excessive retries:281 Invalid misc:0 Missed beacon:0

The Bit Rate drops from 11 -> 2, the Access Point MAC Address sometimes changes entirely to 44:44:44... and the Tx excessive retries / invalid frags just keep on climbing.

I have tried adjusting the RTS threshold, ESSID, Fragment throughput and turned encryption off but nothing seems to alter this behaviour. I dont believe it is anything to do with VNC as moving a large file has the same effect.

I thought it may have something to do with the Link Quality, Signal Level and Noise Level but can find little info on whether these are "good" values or not.

Any ideas guys would be much appreciated. Any other info that may help please just ask...

Cheers

The Phantom
 
Old 06-19-2004, 09:18 AM   #2
Hangdog42
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Actually my first suspicion would be interference from an outside device. Did someone nearby get a 2.4GHz phone? Maybe a neighbor set up their own wireless network and it's signal overlaps with yours. In a stand-alone house this usually isn't a problem but in an apartment or condo it can be a real nightmare.

Most routers allow you to set a channel, and there is a tendency to default to 6, which is right in the middle of the spectrum and therefore most prone to interference. However if you move your router to one end (usually channel 1 or 11) you can minimize the problems. Most 2.4GHz phone search for a "clear" channel when there is a call, so having your router at one end of the spectrum tends to push them to the other end and minimizes interference. If it is a neighbors router, they may be having similar problems and a quick chat may get them to move to one end and you move to the other.
 
Old 06-19-2004, 11:17 AM   #3
phantompgr
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Registered: Sep 2002
Location: South Wales, UK
Distribution: Fedora Core & Mandrake
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Thanks for the reply ...

In order to test for interference I have tried the following, each time loading VNC and seeing what happens:

a) Turned my mobile off which is 2.4Ghz bluetooth
b) The default channel for the router is 11 so I changed it to 7
c) Adjusting the fragmentation

None of these things made a difference. Likewise, I believe that -100dBm is the normal noise level when no other WLANS or industrial nosie around. The card is consistently reporting -93 and the signal level is way above that (aorund -66dBm but sometimes up to 29dBm) which is plenty to ensure 11Mbps. Yet the rate is still fluctuating from 11 -> 2 -> 11 -> 2 -> 11 during the duration of a large data move or opening a VNC session.

Certainly will look out for any neighbours but I am beginning to think it is more to do with the driver in Mandrake, especially as when I boot I get a message about insmod hinting that something has the wrong parameters. I have never isolated the latter error so it may be a red herring.

Any thoughts, let me know

Cheers

The Phantom
 
  


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