AirMagnet PRG-Laptop 7.0, Reference Manual, Page: 153 / 210

AirMagnet Laptop Wireless LAN Policy Reference Guide
Chapter 7: Deployment and Operation Error 145
AP System or Firmware Reset
The wireless Access Point goes through a system or firmware reset in
the event of reconfiguration, power failure, or software defects.
When a system reset occurs, all previously associated client stations
lose their connections until the Access Point has completed its startup
sequence of actions. All client stations have to go through the
authentication and association procedure to regain wireless
connectivity. The period of lost connectivity may range from tens of
seconds to a few minutes.
Since the AP reset is transient and wireless service eventually
recovers, there is usually very little trace to link it to the lost client
connectivity.
AirMagnet Mobile can accurately detect an AP system reset
regardless of the cause. With this AirMagnet Mobile alarm, linkage
can be drawn between interrupted service and its root cause in such a
scenario.
AP with Flawed Power-Save Implementation
The IEEE 802.11 standard defines the power-save operation for
mobile devices to conserve power by entering sleep mode. While the
client remains in sleep mode, the AP will buffer data intended for it
for delivery at a later time. The standard defines the power-save
mode handshake involving the following important procedure:
• Client informs AP of its power-save mode status (going to
sleep)
• AP informs client how often data destined to client will be
indicated in beacon
• AP buffers data intended for the client in sleep mode
• Client wakes up periodically to check on the AP beacons to
see if there is data buffered for it to receive
• If there is no data, client goes back to sleep mode. If there is
data, client informs the AP its power-save mode status to
trigger the AP to send the buffered data
APs failing to conform to this procedure may experience client data
loss. There are two well-known AP implementation defects in this
area:
Laptop Wireless LAN Policy Reference Guide.book Page 145 Thursday, January 25, 2007 5:36 PM