One Slow User In The Hot Spot Can Degrade Wi-Fi Performance

Dom · Aug 2, 2003, 10:42 AM

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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Source: Y!News

Aug 2, 2003, 10:42 AM	#1
Dom DriverHeaven Extreme Member Join Date: Jun 2002 Posts: 12,940 Rep Power: 0	One Slow User In The Hot Spot Can Degrade Wi-Fi Performance 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. ____________________ Source: Y!News