User Manual

Appendix
BreezeNET PRO.11 Series 9-31 User’s Guide
2. On a voice system, a temporary disconnection may not affect the conver-
sation, while in a packet-based environment it significantly reduces per-
formance because retransmission is then performed by the upper layer
protocols.
The 802.11 standard does not define how roaming should be performed, but
defines the basic tools. These include active/passive scanning, and a re-
association process, where a station which is roaming from one Access
Point to another becomes associated with the new one
1.
9.5.6. Keeping Synchronization
Stations need to keep synchronization, which is necessary for keeping
hopping synchronized, and other functions like Power Saving. On an
infrastructure BSS, this is achieved by all the stations updating their clocks
according to the AP’s clock, using the following mechanism:
The AP periodically transmits frames called Beacon Frames. These frames
contain the value of the AP’s clock at the moment of transmission (note that
this is the moment when transmission actually occurs, and not when it is put
in the queue for transmission. Since the Beacon Frame is transmitted using
CSMA rules, transmission may be delayed significantly).
The receiving stations check the value of their clocks at the moment the
signal is received, and correct it to keep in synchronization with the AP’s
clock. This prevents clock drifting which could cause loss of synch after a
few hours of operation.
9.5.7. Security
Security is one of the first concerns that people have when deploying a
wireless LAN. The 802.11 committee has addressed the issue by providing
what is called WEP (Wired Equivalent Privacy).
Users are primarily concerned that an intruder should not be able to:
• Access the Network resources by using similar wireless LAN equipment
• Capture wireless LAN traffic (eavesdropping)
1
The BreezeNET product line provides a patented enhanced roaming mechanism which allows stations to
roam at speeds of 60 Km/h without losing or duplicating packets.