radarnc
@nc.da
| flaw in wireless LAN technology
A group of French researchers said Wednesday that they've spotted a flaw in wireless LAN technology that could allow one slow user to drag down performance of everyone connecting to a hot spot.
Four scientists, who work for France's Centre Nationale de la Recherche Scientifique (CNRS) in Paris, said in their research paper that anomalies in the IEEE 802.1x standard -- including 802.11a, 802.11g, and the most widely-used Wi-Fi protocol, 802.11b -- can result in degraded performance for all accessing the Internet through a hot spot when just one slow user connects.
They cited an example where several users, who are enjoying a fast 11Mbps connection because they're close to the hot spot, see their performance dramatically drop when a single user -- perhaps because he is further from the access point -- connects at a sluggish 1Mbps. In that case, the French experts said, all are punished for the sins of the one: those users once connected at 11Mbps will see their speeds dragged down to 1Mbps.
The anomaly, they said, is inherent in the CSMA/CA (Carrier Sense Multiple Access/Avoidance Collision) access protocol, which guarantees equal access to the hot spot by all devices.
While the problem may not be readily apparent to users -- especially when everyone accessing the hot spot is engaged in relatively light-load activities, such as browsing Web pages -- if just one user is downloading files, or accessing audio or video via wireless, others can be penalized. |
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jparr
join:2003-04-04
/dev/zero | 802.11b WISPs have been dealing with this problem for years. I cannot believe those "French Researchers" weren't embarrased to publish that paper. |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
|  said by jparr  :
802.11b WISPs have been dealing with this problem for years. I cannot believe those "French Researchers" weren't embarrased to publish that paper.
HEHEHE!!!!, LOL!
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»www.wavecrazy.net |
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ikarus1
Premium
join:2002-10-23
Urbanna, VA
| reply to radarnc
Well... hmmmm.... That's not the way it works exactly. I'd say those researchers need to do some research.
IIRC, the AP will talk to you at whatever speed you talk to it. That means *WHEN* the guy at 1 MBit is passing traffic he takes longer to pass that traffic *BUT* when the guy running at 11 MBits is passing traffic he still moves his traffic at 11 MBits. Sure the slow guy impacts everyone because whenever he is talking everyone waits *BUT* I don't believe the impact is that serious... *AND* you can always lock out the lower speeds on the AP... so....
Tell those researchers to rename themselves as students.
-m-
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FAVORITE ANSWERED QUESIONQ: I want to add an antenna to my wireless device, any suggestions?A: »www.freeantennas.com |
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shamanfk
join:2001-03-12
Fort Kent, ME
| It is my understanding that 802.11 is a "listen until clear, then talk" protocol and the others must wait for the channel to become quiet before transmitting.
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Success is getting what you want; Happiness is wanting what you get. |
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ikarus1
Premium
join:2002-10-23
Urbanna, VA
| 802.xx is an half-duplex technology, meaning whomever is talking will be the one who controls bandwidth... UNLESS there is a hidden node problem.
Go back... RE-READ the post. You will figure it out.
-m-
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FAVORITE ANSWERED QUESIONQ: I want to add an antenna to my wireless device, any suggestions?A: »www.freeantennas.com |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| said by ikarus1 :
Go back... RE-READ the post. You will figure it out.
-m-
Are we cranky tonight??:)
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»www.wavecrazy.net |
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guhuna
R.I.P Mike
Premium
join:2001-03-31
Brentwood, CA | reply to radarnc
they have just done this now? wow I could have told ya this 2 years ago. |
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playerap
Check Those Hooters
join:2003-05-08
Bangor, MI | reply to radarnc
wow ya ur right i couldve told u that a long time ago |
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The Folsom
Kindly Shut Your Noise Hole.
Premium
join:2003-01-31
Yucaipa, CA | reply to radarnc
Maybe something got lost in the translation (bah dum bum). |
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philman2
join:2001-02-09
Van Nuys, CA
|  I guess the interesting part of the article is not telling there is an anomaly but explaining mathematically how/why it works and how/if you can circumvent it. In other words, there is a huge gap between "I can feel it" and "I can prove it".
But I guess you guys could all have "told us that a long time ago"  |
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ikarus1
Premium
join:2002-10-23
Urbanna, VA
| reply to superdog
said by superdog :
said by ikarus1 :
Go back... RE-READ the post. You will figure it out.
-m-
Are we cranky tonight??:)
Err ummmm, my bad. Sorry. I guess I was feeling cranky. How do some of these stories make world wide headlines? One would think "researchers" would first read the IEEE specs on 802.xx (whatever) before going to all that effort. It could save them time and let them spend their efforts on something which really *IS* a problem... say SPAM for example.
-m-
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FAVORITE ANSWERED QUESIONQ: I want to add an antenna to my wireless device, any suggestions?A: »www.freeantennas.com |
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drjim
Premium,MVM
join:2000-06-13
Torrance, CA
clubs: | Dude, they're FRENCH! What else would you expect?
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One man's Magic is another man's Engineering. |
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number1melon
Premium
join:2003-01-17
Fort Lauderdale, FL
| reply to radarnc
'zis es bvull sheet'. I have a really really slow old IBM laptop that I sometimes run on my wireless LAN and it dosen't seem to affect the other computers at all.
--
child: "mom, will you take me to Borders?"
mom's drunk friend: don't go! the mexican border is a very dangerous place.
based on atcual events. |
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